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ELEKTORELECTRONIC-SI

CONTENTSFebruary 1995Volume 21Number 230ISSN 0268/4519

In next month's issue

FOCUS ON: CD-ROMWideband active loopantennaTelephone -controlled mains

switch

DSP function generatorTDA I560Q: a 30 W audio

amplifier for carsStepper motor ICLong -life night lightand others for yourcontinued interest.

Front coverFollowing last month'sdescription of the DolbySurround system, this monthwe present a practicalapplication of it in the formof a Surround SoundProcessor (see page 26) asillustrated. However, thisdoes not use special DolbyICs. The design describedalso includes the additionaloutput amplifiers requiredfor the centre channel andsurround channels.

Copyright © 1995 Elektuur

A B CAUDIT BUREAU OF CIRCULATIONS

CONSUMER PRESS

0

26 PROJECT: Surround sound processorBased on a design by D. Laues

CO OINFNTS

48 MOSFET logic invertersBy G. Kleine

64 Operational amplifiers revisitedBy J. Markus

II

16 PROJECT: MIDI multiplexorDesign by P. Rigaill

8 PROJECT: Light -effects generatorDesign by G. Kleine

12 PCB production: the direct toner methodBy Dr R. Milker

22 PROJECT: Automatic lighting timerDesign by E. Quinet

40 FOCUS ON: CAD of schematics and PCBsBy our design and editorial staff

68 PROJECT: Infrared -controlled dimmerDesign by U. Reiser

74 PROJECT: Induction motor governorDesign by H. Bonekamp

52 COURSE: The digital solutionPart 3: acquiring dataBy Owen Bishop

s r

34 PROJECT: Upgrade your car battery chargerDesign by L. Lemmens

9 t i 0

58 Parameters of MMIC wideband RF amplifiersBy G. Kleine

a I a

81 Book availability & prices82 Buyers' guide5 From the world of electronics

82 Index of advertisers46 New Books78 Readers' services81 Switchboard80 Terms of Business

Light -effects generator - p. 8

MIDI multiplexor - p. 16

Surround sound processor - p. 26

c I

Upgrade your car battery chargerp. 34

Elektor Electronics is published monthly, except in August, by Elektor Electronics (Publishing), P.O. Box 1414, Dorchester, Dorset DT2 8YH, England. The magazine isavailable from newsagents, bookshops, and electronics retail outlets, or on subscription at an annual (1994/95) post paid price of £2800 in the United Kingdom; air speeded:

£3500 in Europe, £44.00 in Africa, the Middle East and South America; £46.00 in Australia, New Zealand and the Far East; and $US 59.00 in the USA and Canada. Second

Class Postage paid at Rahway N.J. Postmaster: please send address corrections to Elektor Electronics, c/o Mercury Airfreight International Inc., 2323 Randolph Avenue,Avenel, New Jersey, N.J. 07001.

ELEKTOR ELECTRONICS FEBRUARY 1995

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From the World of Electronics

BT to start trialinteractive TV

BT is to start consumer trials of BT in-teractive TV- which includes video on de-mand - this summer with 2500 house-holds in Colchester and Ipswich. Thisfollows the success of its technical trialsheld near Ipswich with 60 BT employ-ees.

The world -leading new service promisesto create a revolution in the home.BT Interactive TV brings together thetelephone and the television to enablecustomers to choose a range of servicesfrom a menu on an ordinary television set.The material is then transmitted from acentral database over the telephone net-work to the television, while not affect-ing the normal telephone line.

BT aims to offer, during the period ofthe trial, shopping on demand, a rangeof educational programming for homes andschools, movies and television program-ming (video on demand), a home bank-ing service, a magazine service and acommunity link (a local infrmation ser-vice). Additional services will be intro-duced during the course of the trial.

Shopping on demand will be offeredunder individual brands by Thomas Cookfor holidays and travel, Sears (Olympus,Adams and Freemans) for a wide rangeof fashion and sporting goods, and W.H.Smith for books, CDs and videos. A gro-cery service is being developed by SafewayStores PLC and will be offered during thecourse of the trial as capacity on the sys-tem grows.

The television service will be devel-oped with the consortium of BBC, Carlton,Granada, Kingfisher and Pearson with pro-grammes supplied by the member com-panies and their subsidiaries. Movieswill be offered from the major Hollywoodstudios and leading UK and Europeansources.

Additional sports programming willbe supplied by BSkyB and music pro-gramming will be supplied by BMG Video(UK), Picture Music International (thevideo subsidiary of EMI), Polygram, SonyMusic and Warner Music.

Customers will be able to choose from600 hours of television programming,400 hours of movies and 200 hours of musicprogramming, all of which will be regu-larly updated.

There will also be 350 hours of edu-cational programming ranging from chil-dren's to adult learning. This service willbe offered free of charge to eight schoolsin the Ipswich and Colchester area aswell as being available in the trial homes.

Educational programming will be sup-plied by Abbey Home Entertainment,Academy TV, Adult Literacy and Basic SkillsUnit, Anglia TV, BBC, Channel 4, Dorling

Kindersley Vision, the Industrial Society,Open University, Video School and YorkshireTV.

The trial homes will have access to amagazine service supplied by IPC MagazinesLtd which displays video, audio, text andgraphics.

Customers will be able to access a TVprogramme guide with features aboutTV programming plus leadings sport andlifestyle titles such as Golf Monthly andFamily Circle.

National Westminster Bank will offera home banking service which will pro-vide account management services, suchas balances, statement information andtransfers between accounts, as well as prod-uct information on a wide range of per-sonal financial services.

Technology contractsThe technology used in I3T's trials has beenundergoing technical evaluation sinceMarch last year. Following its success, BThas awarded a number of contracts forthe marketing trial.

Oracle will provide the multimediadatabase and navigational software andnCUBE will provide the media server.The customer management system comesfrom Sequent and Apple Computers aresupplying the set -top boxes.

Technical notesThe set -top box (STB) was based on anApple Macintosh LC475 computer, run-ning Mac 0/S modified to support MPEGand a 2 Mb/s network interface. At startupit downloads the operating system andOracle Media Objects (OMO), the runtime version of the authorware tool inwhich the services are created.

The network connected to the STB wasa 2 Mb /s stream delivered over eithercopper using asymmetric digital sub-scriber loop (ADSL) or fibre. ADSL tech-nology delivers over an ordinary tele-phone loop 2 Mb / s in one direction, a9.6 kbp/s bidirectional control channeland the ordinary analogue telephone ser-vice.

The variety of ADSL used at the trialwas DMT (discrete multitone) which di-vides the spectrum into a number ofbands and spreads the video transmis-sion over them in such a way as to min-imize interference and noise. For the fibredelivery a passive optical network was used.

Users were connected directly to theserver system without any concentra-tion or switching stage. The server sys-tem consisted of an nCUBE massivelyparallel computer and the system ran onOracle database software with the videocontent compressed to MPEG-1 stan-dards.

In the marketing trial BT will be usingADSL along with fibre in the ratio of about

4 copper to 1 fibre. Instead of DMT, CAP(carrier -less amplitude and phase mod-ulation) ADSL will be used in the marketingtrial.

In the marketing trial, BT will be stay-ing with the same combination of serverand set -top box technologies suppliedby nCUBE, Oracle and Apple Computers.However, there will be a switching/con-centration stage which will be ATM based.Users will be connected to an ATM switchwith a concentration ratio of roughly twoto one. This means that there are abouttwice as many users as there are serverports and about half of them can be online to the system at any one time.

Intelligent agents forcommunications networks of

the futureWith the burgeoning of communicationssystems to include new facilities, manyand varied networks are coming into usesuch as those involving fixed optical fibrelinks, radio cells, optical wireless andsatellite microwave - and these in turnuse a variety of transport mechanisms.

The customers of the future will findthemselves connected simultaneously toseveral different networks each of whichmay present limitations as well as ad-vantages.

In the early days of telephony whenhuman operators held sway, a caller ask-ing for a number would perhaps be toldby the operator: "Mr Jones has left home,and is now at his office. I've just put a callthrough to him, Shall I connect you to himthere?" The advent of automatic tele-phone exchanges, however, soon put paidto this type of on-line intelligence.

BT (British Telecommunications) cur-rently invests upwards of 2% of its annualturnover in Research and Develop -ment(R&D). Its major research facility, BTL (BTLaboratories) at Martlesham Heath is ac-knowledged as the leading telecom-munications R&D establishment in Europe.

The main activity of BTL is in systemsand software development and its primepurpose is to provide world -class exper-tise via its well -directed R&D programmesin advance of customer needs. The demiseof the helpful operator has not escapedBTL's attention.

A major research project at BTL is di-rected to effectively restoring a service equiv-alent to that provided by the human op-erator but geared to the 21st century.The objective of this service would be ne-gotiation in finding the best deal for thecustomer in terms of facilities and costin the plethora of network types and ser-vices that confront him.


6

Mimic humanThe devices that will provide this serviceare known as intelligent agents, specialsoftware processed which mimic humanbehaviour in providing a simple and el-egant method of managing network com-plexity and providing an intelligent interfaceto the customer or his own intelligentagent.

It may be postulated that this aspectof network control should be centralized.However, this would involve a large data-base, high traffic density and low re-silience. The simple comparison shownmakes it evident that a simple distributedmodular system has much in its favour.

The distributed agents form a singlelayered system using the underlying fixednetwork for inter -agent communicationand can be grouped in three generic cat-egories:* Interface Agents - Customer Agent

(CA), Gateway Agent (GA);* Service Provider Agents (SPAs);* Network Management Agents - Fixed

Network Agent (FNA), Cell Agent (CLA).

The Interface Agent, CA1, mediates be-tween the system and the customer (C1)while GA links the agent system with an-other intelligent or non -intelligent man-agement system, owned perhaps by an-other telecom operator. Between themthey facilitate the transfer of informa-tion or requests between the agent sys-tem and the external world.

The Service Provision Agents are eachresponsible for a specific service. They man-age provider service information and ne-gotiate with those wishing to sell their re-sources: a customer may require spe-cific data which comes from a variety of

sources.

Security issuesIn principle, each agent is permitted tocommunicate with any other agent exceptSPAs which have communication chan-nels only with CAs. This measure takesaccount of security issues in that it doesnot allow SPAs responsible for specialservices provisioned through the resourcesof an external company to have access tonetwork management or customer in-formation.

The CA relays the customer request tothe SPA which then decides which cus-tomer agent (responsible for the resourcerequired) should be contacted at the otherend. Subsequently, the CAs contact thenetwork management agents that set upthe service.

The Network Management Agents aremainly responsible for managing resourcesin the fixed network or in the mobile (cell)network (CLAs). Cell agents can be ofvarious types and relate to the cell man-aged: Macro Cell Agent (CLA-M), Micro CellAgent (CLA-m), or Pico Cell Agent (CLA-p).They work cooperatively to integrate theiravailable local resources (in the form oflink capacities or cell bandwidth) in acomplete configuration required for aparticular service.

Constant updatingThey are also continuously updating thatresource configuration to cope with changesin the environment and service deliverypoint changes the customer moves around.The agents communicate by passing fixedformat messages. On receipt of a messagean agent will make its own decisions,triggering an internal task or deciding to

communicate with other agents sendingor requesting information.

An example of the role of agents maybe considered in the context of third gen-eration mobile phones that use macrocells of 10 km, micro cells of 500 m, andpico cells a few metres across. The capacityof each cell is the same but because thecustomers -to -cell size will differ, the ca-pacity to customer will differ. The customerdoes not know which cell he is in, simplythe services available - so the followinghappens.

When the phone registers the cus-tomer's presence in the radio cell or thephone is plugged into the fixed network,the agent managing that network calcu-lates the capacity and current cost andsends this information to a customer -facing agent representing the customer.This second agent intelligently comparesthe price and capacity available againstthe services the user is subscribed to andselects those that are acceptable. Relayedback to the customer the services areshown on the phone's LCD (liquid -crys-tal display) as a series of icons with theprices below. So, as the customber movesaround he can see at a glance all the ser-vices available and the price, if appropriate.

Maintain serviceWhen the customer selects a service andmoves to a new cell, the agent will nego-tiate to maintain service. This may be atan increased price if the service is not nor-mally available in that cell, or it mightinvolve downgrading the quality of, say,the video picture. On a data service, theagent may store the information untilthe user is again in a position to receiveit.

Produced and published by ELEKTOR Unit 4, Gibbs Reed Farm Overseas editions' NETHERLANDSELECTRONICS (Publishing) Pashley Road FRANCE Elektuur BV

TICEHURST TN5 7HE Elektor sarl Peter Treckpoelstraat 2-4Editor Len Seymour Telephone: (01580) 200 657 (National) Les Trots Tilleuts 6191 VK BEEKTechnical Editor, Jan Buiting or +44 1580 200 657 (International ) B.P 59, 59850 NIEPPI3 Editor. P.H.M Bagger

Fax: (01580) 200 616 (National) Editor G C.P. RaedersdorfEditorial & Administrative Offices: or +44 1580 200 616 (International) POLANDP.O. Box 1414 GERMANY Elektor ElektronikDORCHESTER DT2 8YH Head Office. Elektor Verlag GmbH 02-777 Warszawa 130England P.O Box 75 Stlsterfeld StraBe 25 Skrytka Pocztowa 271Telephone (01305)250995 (Natrona! ) 6190 AB BEEK 5100 AACHEN Editor W Maranialtor +44 1305 250 995 (International) The Netherlands Editor. E.J A KrempelFax (01305) 250 996 (National) Telephone: +3146 38 9444 PORTUGALor +44 1305 250 996 (International) Telex 56617 (elekt n1) GREECE Fen eira & Bento Lda

Fax* +31 46 37 01 61 Elektor EPE R D Estefani, 32-PU.K. Advertising Office Managing Director: Karaiskaki 14 1000 LISBOA3 Crescent Terrace Johan H Boermann 16673 Voula-ATHENA Editor: F Ferreira de AlmeidaCHELTENHAM GL50 3PE Deputy Managing Director Editor. E. XanthoultaTelephone. (01242) 510 760 Menno M.J. Landman SPAINFax. (01242) 226 626 Editor-In-Chief/PubKsher. INDIA Resistor Electromca Aplicada SA

Pierre E.L. Kersemakers Elektor Electronics PVT Ltd P., de la Castellana, 212-4° lzdaInternational Advertising Office: Commercial Manager: Chhotani Building 28046 MADRIDElektuur BY Kind van Noordenne 52C, Proctor Road, Grant Road (E) Editor: Agustin Gonzales BueltaP.O. Box 75 BOMBAY 400 0076190 AB BEEK Distribution: Editor C R. Chandarana SWEDENThe Netherlands SEYMOUR Electrotue Press AllTelephone +31 4638 94 44 1270 London Road ISRAEL Box 5505Fax. +3146 37 01 61 LONDON SWI6 4DH Elektorcal 14105 HUDDINGE

P 0 Box 41096 Editor Bill CedrumSubscriptions:World Wide Subscription Service Ltd

Printed in the Netherlands by NDB,Zoeterwoude

TEL AVIV 61410Publisher: M Avraham


Intelligent agents using advance AItechniques to communicate and coop-erate with each other are ideally suitedto maintain network integrity and opti-mization. When a fault occurs, they canwork together to heal the network and,in the worst case, they can ensure thatthe network degrades in a controlled fash-ion without catastrophic results.

BT believes that intelligent agents pro-vide the ideal means to supply customersand businesses with fast, transparentaccess to the global information which willsoon become the norm - anywhere, atany time, and in any format.

More computer aidfor the dumb

New computer software that lets dumbpeople participate in real communica-tions has been released for commercialuse after 10 years research and devel-opment. The TALK:ABOUT programme,developed at the MicroCentre of DundeeUniversity, allows the disabled to tell sto-ries about themselves at the single touchof a button. Software developer Mr DonJohnston, whose eponymous company isputting the research into the hands of theconsumer believes "we are standing onthe threshold of a new era for users of aug-mentative and alternative communication-an era of near -real-time communication".

Professor Alan Newell, director of theDundee MicroCentre, adds: "What makesTALK:ABOUT special is the way it can beused to communicate not just wants andneeds, but thought, ideas and the morepersonal elements of everyday conver-sation such as anecdotes. Conversationsencompass several components: fast so-cial interactions, beginning small talk, novelsentences, extended reusable talk, wrapups and farewells. TALK:ABOUT is the re-sult of at least four distinct projects thathave been developed in parallel to ad-dress different components of human in-teraction. It offers high -quality text -to -speech output or digitized voices and alsoworks with external speech synthesiz-ers".

The Dundee team is also working onanother development: ALADIN (AdvancedLanguage Device for Interaction) projectwhich speeds up computer assisted con-versations and adds synthesized voicefor people unable to speak.

Furhter information from Universityof Dundee, Dundee, Scotland DD1 4HN.Telephone +44 (0)1382 23181. Fax+44 (0)1382 23117.

Faster introduction ofdigital -qualitybroadcasting?

broadcast reception in the home and carmay be brought closer by a plan to developconsumer radio equipment to a new DigitalAudio Broadcasting (DAB) standard. TheDAB Receiver Develop-ment Club set upjointly by the Roke Manor Research andEnsigma companies will enable radio andaudio manufacturers to join forces toturn low-cost DAB receivers into reality.

The club will focus on the early avail-ability of low-cost DAB receiver chips andmulti -band radio designs in the light ofthe allocation of different frequenciesacross Europe. The aim is to develop a DABchip and a multi -band radio receiverboard containing this chip by the end ofthe year.

The formation of the club has beenwelcomed as a timely complement to theBBC's plan to launch network radio ser-vice using DAB in September this year.

Roke Manor Research is involved in rel-evant radio technologies as an acknowl-edged European centre of excellence inthe field of mobile radio and personalcommunications.

Ensigma, a specialist in real-time digi-tal signal processing, designed the TexasInstruments decoder chip now used in 80per cent ofJapanese-manufactured NICAMvideo recorders.

Further information from Roke ManorResearch Ltd, Romsey, Hants, EnglandS051 OZN. Phone +44 (0)1794 833 658.Fax +44 (0)1794 833 589.

New Cirkit catalogueCirkit's Winter 1994/95 edition of theElectronic Constructors' Catalogue isnow available. This enlarged, 280 -pageedition includes for the first time a newsection with feature articles, news and twoespecially comissioned projects: infraredcordless headphones and a PC -controlledlogic IC tester. These are published infull detail with complete kits availablefor both.

Many other new products have beenadded throughout the catalogue; the testequipment section, for instance, includesa wide range of new test gear from Kenwood,Hameg and TTi plus an RS232 multime-ter with interface and comprehensiveWindows software along with a new rangeof affordable thermometers and timers.

With 26 product sections, 280 pagesand some 4000 lines, the catalogue alsoincludes £21 worth of discount vouchersand is available from most largernewsagents or directly from CirkitDistribution, Park Lane, Broxbourne,England ENIO 7NQ .

Serial EEPROM Handbookfrom Microchip

Microchip's new Serial EEPROM Hand-book provides essential information and

valuable advice on Microchip's range ofserial EEPROM memories. The 480 -pagehandbook is the first comprehensive ref-erence tool for Microchip's Serial EEPROMs.Including 25 product specifications, 12application notes and nine qualificationreports, the handbook covers all of the com-pany's memory products and develop-ment tools.

The handbook, which is availablethrough any Microchip sales office, dis-tributor or representative, is an integralpart of the company's newly announcedSerial EEPROM Designer's Kit.Arizona Microchip Technology, Unit 3, TheCourtyard Meadowbank, Furlong Road,Bourne End, England SL8 5AJ. Phone(01628) 850 303; fax (01628) 850 178.

Sub note -book professionalprogrammer

Stag Programmers have annmounced anew, battery powered programmer, theOrbit 48. This is a portable program-mer with all the facilities found in a desk-top unit. It is, therefore, easily carried ina briefcase or tool -box for use in the field,but equally suited to general engineeringapplications in the laboratory.

The Orbit 48 offers an extensive rangeof device support which includes popu-lar devices from the world's major man-ufacturers in the following categories:CMOS PROMs, EPROMs, EEPROMs,FLASH and Intel style (87C51 family)Micros as standard and EPLDs via a low-cost docking module.

With a 48 -pin WideBlade ZIF socketand 4 Mbit of RAM, expandable up to16 Mbit, Orbit 48 can program 16 -bitEPROMs, MROM pinout EPROMs and8 -pin serial EEPROMs - all as standardand all from one socket. Eight, 16 and 32bit mode programming is made simple bythe use of 'Interlace 2', pioneered by Stagwhich is easier and faster than the cum-bersome 'split' and 'shuffle' technique.

In keeping with Stag's quality engi-neering philosophy, all the data requiredto program this vast array of devices isheld in FLASH (non-volatile) memory.This has two distinct advantages overother systems: (1) the data can not be cor-rupted in the way certain RAM -basedsystems do, and (2) updating the infor-mation can be performed without open-ing up the programmer - data transfer oc-curs via an I/O port or the programmingZIF socket.

The Orbit 48 contains a high-speedEPROM emulator which enables code tobe run in a target system without first hav-ing to commit time and resource to pro-gramming and erasing devices.

Further information from StagProgrammers - see advertisement onpage 39.

The prospect of near -CD -quality audio


8

LIGHT -EFFECTS GENERATORThis running light circuit drives a matrix consisting of 8 up to32 LEDs, and is primarily intended for playful and decorativeapplications. A wide variety of display patterns can beprogrammed with the aid of a simple plug-in adaptor.

Design by G. Kleine

ALTHOUGH the present circuit con-ains most ingredients found in a

typical running -lights generator, it ismarked by one fairly special feature:the display pattern can be pro-grammed with a plug-in adaptor. Thisadaptor sits between the driver IC andthe LEDs. It determines three func-tions of the generator: the order inwhich the LEDs light; whether one orseveral LEDs light at a time; andwhether or not a repeating pattern isshown. If you have had enough of acertain pattern, simply select a newone by plugging in the appropriateadaptor.

Circuit descriptionAs shown by the circuit diagram inFig. 1, the light -effects generator is asimple design by almost any standard.Even beginners should be able to buildthe circuit successfully because rela-tively few components are involved,and a ready-made circuit board isavailable. Building, programming and,most of all, using the circuit should befun.

The display consists of eight rows ofLEDs. Each row consists of a mini-mum of one LED (in which case it isnot really a row), and a maximum offour LEDs connected in series. Series

resistors R5 -R12 allow an LED currentof about 15 mA. The exact value de-pends on the number of LEDs con-nected in series.

The display is connected to LED dri-ver IC3 via adaptor K1. The latter isnothing but a good -quality 20 -pin ICsocket into which another 20 -pin ICsocket is plugged. The wires fitted onthe latter determine the display pat-tern as will be discussed further on.IC3 is an octal LED driver with opencollector outputs. The device is capa-ble of switching a total load of 500 mAto ground. The LED driver obtains itsinput signals from two cascaded shiftregisters, IC2a and IC2b. The first sevenoutputs of this double shift register(QA-QD of IC2a, and QA, QB and QC ofIC2b) are connected to the LED driverinputs as well as to the inputs of NORgate IC4. This is done to ensure that anew logic one is formed when the shiftregister is completely filled with zeroes,which would otherwise remain so aslong as the circuit is left on. This canbe exploited by interconnectingpins 11 and 12 on adaptor K1, inwhich case the output of the NOR gateis linked to the D input of shift regis-ter IC2a. To make sure that a pre -de-fined state exists in the shift register atpower -on, the reset input of IC2 re-ceives a reset pulse from network R2 -

C2. This pulse causes all shift registeroutputs to go low on reset.

Both clock oscillators in the circuitconsist of a Schmitt trigger NAND gateof which there are four in a the 4093integrated circuit. The oscillators areidentical except for the value of the ca-pacitor used. The oscillator aroundIC la supplies the clock proper for theshift register, while IC ib functions as akind of data generator to provide theflash function of the circuit. The flashpulse is available on pin 1 of K1, andcauses the LEDs to flash at a rate ad-justed with preset P2. The other preset,P1, allows the speed of the shift regis-ter to be adjusted within fairly widelimits.

The circuit may be powered by amains adaptor (with d.c. output) or di-rectly from a car battery. The supplyvoltage is cleaned by a filter consistingof L1, C4 and R13. The latter is a varis-tor or VDR (voltage dependent resistor)which is capable of suppressing fastvoltage surges. The varistor and chokeL1 may be omitted if the circuit is notused in a car. L1 is then replaced by awire link.

Programming the lighteffectsPins 2 through 8 of the adaptor socket,K1, are connected to the LED driveroutputs, while the data clock is avail-able on pin 1. Pins 9 and 10 are con-nected to ground. At the other side ofthe socket, pin 11 is connected to thedata input of the shift register. Pin 12is linked to the output of the NOR gate,and pins 13 through 20 to the LEDrows.

There are, in principle, three waysof programming the adaptor. If one ofthe LED row connections (pins 13-20)is wired to ground (pin 9 or 10), therelevant LED row will be on all time.Since that is not very appealing, it willbe a rarely used option. By connectingone of the pins 13-20 to pin 1, theLEDs in the relevant row will flash at arate set with P2. Finally, if one or moreLED row pins are connected to pins 2through 8, the relevant LED rows willlight in the rhythm of the shift register,whose shift speed is set with preset P1.

The latter option has three furtherpossibilities.

(1). Adaptor pin 11 is not connected.The data input of IC2 is then heldhigh all the time via resistor R4. Atthe first clock pulse which appearsafter the circuit is switched on, thefirst output of IC2 will go high, andremain high 'forever'. At the next


LIGHT EFFECTS GENERATOR 9

OIC1b

5

6 ff &

P2

C3

:1708

O

2

1M

IC1a

ff &

P1

-1hA-11111

C1 1M

IIC1 c

4

TR3

TR1

IC2a

15

SRG4C1/

10

10

-1-VS11

2

3

11 4

2

9

IC2b

7

loon

R2

SRG4>C1/

4

3

01

02

03

IC35 15 05615 ULN 062804

17 A 077

3

IC1 = 4093IC2 4015

10

2 3 4 9 10 11 12

818 08

VEE

5

C44078

K2

08 107 2

16 3

05 404 503 6'.12 7

\1 8

9

10

M1M

L1

K1

O

O

0O

O0O

O

O

O

O

OO

O

O

OO

20

19

2

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1001125V

R12

D1 - D32 = LED

44 44 44 44

-14-14-14-14-

VII

++ ++ ++ ++

mk9IC1 IC2 IC4

100n

940100 -11

100n

Fig. 1. The light effects generator consists mainly of two oscillators (1Cia and ICib), a dual shift register (IC2), an octal LED driver (IC3) and a

display which consists of 8, 16, 24 or 32 LEDs. The value of resistors R5 trough 1112 depends on the number and type of LEDs fitted.

clock pulse, the second shift regis-ter output goes high, etc.Therefore, when pins 14 through20 of K1 are linked to 8 through 2,respectively, LEDs D1 -D4 light atthe first clock pulse, followed byD1 -D8, D1 -D12, etc., until all LEDslight except those in the eighthrow, which are not used.

(2). Pin 11 is linked to pin 12. The datainput of IC2 is then connected tothe output of NOR gate IC4.Consequently, a '1' is clocked onlyif all outputs of IC2 are at '0'. Inother words, only one output of IC2is active at a time. Assuming thatpins 14-20 are again linked to pins8-2, the LED rows will light alter-nately. This pattern is repeated atthe end of the cycle.

(3). Pin 11 is linked to pin 1, so thatthe data input of the shift registeris connected to the output of thedata generator, IC1b. The dataclocked is random, and so is thelight pattern produced by this op-tion.

A number of programming examplesare shown in Fig. 2. The most obviousone is given in Fig. 2a. This results in arunning light, with one LED row mov-ing from the left to the right across thedisplay. If you want the row to move inthe other direction, use the adaptorshown in Fig. 2b.

The configuration shown in Fig. 2c

causes a `point' consisting of two LEDsto grow into a bar. If all 32 LEDs arefitted in the matrix, the effect is a ver-tical bar which widens from the centreof the display until the entire display

area lights. This variant is particularysuited to creating a third brake light ina car or on a motor cycle (note that theuse of such a light may be restrictedby laws).

K1

20 19 18 17 16 15 14 13 12 11

2 3 4 5 6 7 8 9 10

K120 19 18 17 16 15 14 13 12 11

0 0

1=IMIA 0 0 0 0 0

2 3 4 5 6 7 8 9 10

K1

20 19 18 17 16 15 14 13 12 11

1 2 3 4 5 6 7 8 9 10

0 0 0 0 0 0 0 02 0 0 0 0 0 0 0 03 0 0 0 0 0 0 0 04 0 0 0 0 0 0 0 05 0 0 0 0 0 0 0 06 0 0 0 0 0 0 0 07 0 0 0 0 0 0 0 08 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 02 0 0 0 0 0 0 0 03 0 0 0 0 0 0 0 04 0 0 0 0 0 0 0 05 0 0 0 0 0 0 0 06 0 0 0 0 0 0 0 07 0 0 0 0 0 0 0 08 0 0 0 0 0 0 0 0

1 0 0 0 0 0 0 0 02 0 0 0 0 0 0 0 03 0 0 0 0 0 0 0 04 0 0 0 0 0 0 0 05 0 0 0 0 0 0 0 06 0 0 0 0 0 0 0 07 0 0 0 0 0 0 0 08 0 0 0 0 0 0 0 0

K120 19 18 17 16 15 14 13 12 11

O 02 3 4 5 6 7 8 9 10

K120 19 18 17 16 15 14 13 12 11

O 0

0 0 0 0 0 0 0 0 02 3 4 5 6 7 8 9 10

O K120 19 18 17 16 15 14 13 11

O 01 2 3 4 5 6 7 8 9 10

O

0 0 0 0 0 0 0 02 0 0 0 0 0 0 0 03 0 0 0 0 0 0 0 04 0 0 0 0 0 0 0 05 0 0 0 0 0 0 0 06 0 0 0 0 0 0 0 07 0 0 0 0 0 0 0 08 0 0 0 0 0 0 0 0

1000000002 0 0 0 0 0 0 0 03 0 0 0 0 0 0 0 04 0 0 0 0 0 0 0 05 0 0 0 0 0 0 0 06 0 0 0 0 0 0 07 0 0 0 0 0 0 0 08 0 0 0 0 0 0 0 0

1 0 0 0 0 0 0 0 02 0 0 0 0 0 0 0 03 0 0 0 0 0 0 0 04 0 0 0 0 0 0 0 05 0 0 0 0 0 0 0 06 0 0 0 0 0 0 0 07 0 0 0 0 0 0 0 08 0 0 0 0 0 0 0 0

940100 - 12

Fig. 2. Six examples of wire configurations on adaptor K1, along with the resulting displaypatterns.


10 GENERAL INTEREST

Fig. 3. Track layout and component mounting plan of the PCB designed for the light effectsgenerator (board available ready-made through the Readers Services, see page 78).

The adaptor shown in Fig. 2dcauses the entire display to flash at arate set by P2.

Figure 2e shows an adaptor config-uration which causes a random dis-play pattern as with basic option (3)above.

Figure 2f, finally, results is a kind ofcombination of effect 2a and 2b: a run-ning light which moves continuouslyfrom the left to the right, and vice versa.Evidently, there are many more possi-bilities to wire the adaptor, and theseare left for you to discover and try out.

ConstructionThe printed circuit board designed forthe light effects generator is shown inFig. 3. Construction should not pre-sent problems if you stick to the com-ponent overlay and the componentslist.

So-called super luminosity LEDs arepreferred if you want to make sure thatthe light effect is visible from a dis-tance. These 5 -mm diameter LEDs pro-duce their highest light intensity at a

continuous current of 30 mA. However,to prevent damage to the LEDs at rela-tively high ambient temperatures, thevalue of resistors R5 -R12 is such thatabout half the maximum current flows.The resistor value is, of course, depen-dent on the number of LEDs connectedin series. Obviously, LEDs not fittedmust be replaced by a wire link.

A disadvantage of super luminosityLEDs is their fairly high price. If youwant to try the circuit with ordinaryLEDs first, that is, of course, possible.Since ordinary 5 -mm dia. LEDs aresatisfied with a current of about10 mA, the value, R, of R5 -R12 has tobe calculated from

R = (14-2n)// IkS21

where n is the number of LEDs con-nected in series, and I, the LED cur-rent in mA.

If economy as regards current con-sumption is an issue, you may con-sider using high -efficiency LEDs. Sincethese can make do with 2 to 3 mA, R5 -R12 can be given even higher values

Resistors:R1;R3 = 1042R2 = 1MC1R4 = 47k0R5 -R12 = 3901/ to 82052 (see text)R13 = S07K14 or equivalent 14V VDRP1;P2 = 1MS2 peset H

Capacitors:C1= 1pF MKTC2 = 100nF MKTC3 = 470nF MKTC4 = 100pF 25V radialC5;C6 = 100nF Sibatit or ceramic

Semiconductors:D1 -D32 = super -luminosity LED, e.g.,Sharp type GL5UR3K1IC1 = 4093IC2 = 4015IC3 = ULN2804AIC4 = 4078

Inductors:= 560pH, 160mA

Miscellaneous:K1 = two 20 -pin turned pin IC sockets.K2 = 2 -way PCB terminal block, raster5m nn.

Enclosure: Heddic 222.Printed circuit board, order code940100-1 (see page 78).

based on the above formula.The sockets used for the adaptor

and the one on the board (position K1)should be a good quality types, prefer-ably one with turned contacts. Thewire links should be soldered quicklyto the adaptor socket pins to preventdeformation owing to overheating.Thin enamelled copper wire is fine tomake the links. Check for the correctconnections before inserting the adap-tor into the socket on the board.

The completed board can be slidinto a transparent plastic case type222 from Heddic. No screws are re-quired to secure the board in the case,while the LEDs are clearly visible.

Finally, if you plan to power thelight -effects generator from a mainsadaptor, make sure enough supplycurrent is available. The currentdrawn by the circuit depends almostentirely on the type and number ofLEDs fitted. The full-blown version,with 32 super luminosity LEDs fitted,requires a mains adaptor with a capac-ity of at least 150 mA at 12 Vdc.

(940100)



ESR ELECTRONIC COMPONENTSStation Road, Cullercoats, DEPT. EETyne & Wear NE30 4PQTel. 091 251 4363 Fax. 091 252.2296

741S -Series

74L000740001740502740303740004740005741_008740S09740010740010774001097405117403112741_0113740511474001274001227400123740012574001267400137400132740S133740013674LS1387400139740014740014574001477400148740015740015174001537400154740015574001567400157740015874001607400161740016274001637400164740016574001707400173740017474001757400190741_01917400192740019374001957400196740019774002074002174002274002217400240740024174L52427400243740024474002457400247741_025174002577400258740026740026674LS27740027374LS279740030740032740036574003677400368740037740037374LS374740037574LS377740037874L538740039074LS3937400395740539974L04074LS42740047740551740867074007374007474LS7574007674LS83740085740S8674009074LS9274LS93

£0.22£0.14£0.14£0,14£0.14£0.14£0.14£0.14£0.14£0.23£0.21£0.17£0.21£0.21£0.21£0.14£0.31£0.31£0.21£0.21£0.14£0.21£0.18£0.16£0.24£0.25£0.18£0.56£1.26£0.70£0.14£0.25£0.25£0.70£0.250.360.25£0.25£0.32£0.32£0.32£0.32£0.26£0.48£0.30£0.24£0.24£0.24£0.25£0.24£0.42£0.24£0.24£0.24£0.24£0.16£0.14£0.14£0.36£0.32£0.32£0.32£0.32£0.32£0.36£0.32£0.24£0.24£0.24£0.14£0.14£0.14£0.32£0.25£0.14£0.14£0.21£0.21£0.21£0.14£0.32£0.32£0.34£0.32£0.62£0.14£0.25£0.24£0.26£0.62£0.14£0.257:0 72£0.14f 0.69£0.17SO 2500.19£0.25£0.31£0.35£0.20£0.23£0.35£0.25

ENAMELLEDCOPPER

WIRE

All 2oz Reels14 SWG16 SWG18 SWG20 SWG22 SWG24 SWG26 SWG28 SWG30 SWG32 SWG34 SWG36 SWG38 SWG40 SWG

£0.63£0,67£0.67£0.72£0.76£0.80£0.89£0.91£0.93£0.93£0.99£1.04£1 10£1.22

4000. Series

400040014002400640074008400940104011401240134014401540164017401840194020402140224023402440254026402740284029403040314033403440354040404140424043404440464047404840494050405140524053405440554060406340664067406840694070407140724073407540764077408140824085408640894093

40944095409740984099450245034508451045114512451445154516451845204521452645274528452945324534453645384541454345554556456045684572458445854724401064010940163401744017540193

£0.17£0.21£0.17£0.40£0.28£0.31£0.19£0,23£0.26£0.16£0.21£0.30£0.31£0.18£0.27£0.27£0.19£0.31£0.31£0.32£0.16£0.21£0.15£0.59£0.18£0.22£0.36£0.17£0.70£0.56£1.24£0.31£0.29£0.31£0.22£0.28£0.35£0.31L0.48£0.31£0.20£0.20£0.36£0.25£0.25£0.56£0.341:0 se£0.29£0.18£1.91£0.16£0.20£0.17£0.20£0.17£0.17£0.17£0.30£0.17£0.14£0.21£0.28£0.26£0.55CO.30£0.31£0.56£1.20_045£0.38£0.38£0.31£0.90£0.26L0.32£0.32£0.77L0.98£0.31£0.27£0.26£0.62£0.40£0.40£0.40£0,44£0.32E2.48£1.00£0.37£0.33£0.46£0.34£0.34£1,18£1.96£0.25£0.24£0.32£0.700.31£0.50£0.46£0.34£0.36£0.60

-2N1613 £0.31 BC186 £0.33 805342N1711 £0.26 BC204C £0.72 05352N1893 £0.29 002050 £0.72 BD5362N2218A £0.28 BC207C £0.72 BD6462N22194 £0.25 BC208 £0.72 BD6482N2222A £0.16 BC209A £0.72 BD6502N2646 £0.80 BC212 £0.08 1307072N2904A £0.25 BC212L £0.08 808072N2905A £0.23 BC212LB eacm BDX322N2907 £0.20 BC213 £0.08 BDX33C2N2926 £0.16 BC213LC £0.08 BDX34C2N3053 £0.27 BC214 £0.08 BOX53C2N3054 £0.90 BC2140 £0.08 BOX54C2N3055 £0.62 BC2378 £0.09 8E1802N3440 £0.50 BC238C £0.09 8E1822N3702 £0.09 BC239C £0.10 6E1852N3703 £0.10 BC251 £0.13 6E1942N3704 £0,10 BC252 £0.13 6E1952N3705 £0.10 BC261B £0.24 13E2442N3706 £0.10 BC262B £0.24 6E2572N3771 £1.44 BC2678 £0.30 6F2592N3772 £1.51 BC307 £0.10 6E3372N3773 £1.79 BC308 £0.10 6E3552N3819 £0.40 BC327 £0.10 6E4232N3820 £0.58 BC328 £0.10 6E4512N3904 £0.10 BC337 £0.10 6F4592N3905 £0,10 B C338 £0.10 6E4692N3906 £0.10 BC414C £0.13 BFX292N4036 £0,31 B C441 £0.40 BEX842N5296 £0,57 BC461 £0.40 BFX852N5321 £0.57 B C463 £0.29 BEY502146307 £0.60 B C478 £0.32 13E1'51AC125 £0.30 BC479 £0.32 BFY52AC127 £0.30 B C490 £0.24 BS107AC128 £0.28 BC518 £0.22 130170AC187 (0.45 BC517 £0.20 BSW66AC188 £0.37 BC527 £0.20 BU126ACY17 £3.84 BC528 £0.20 BU205AD149 £1.67 BC537 £0.20 BU208A40161 £0.92 BC546C £0.08 BU326AAD162 £0.92 BC547C £0.09 BU500BC107 £0.14 BC548C £0.08 BU508ABC1075 £0.15 BC549C £0.10 BU526BC108 L0.14 BC550C £0.08 BU806BC108A £0.14 BC556A £0.08 BUX84801080 £0 16 8C557C £0.06 IRF540130109 £0.14 BC558C £0.08 IRF740BC109C £017 BC559C £0.08 MJ11015BC114 £0.41 BC560B £0.09 MJ11016BC115 £0.41 BC637 £0.21 MJ2501BC116 £0.41 BC638 £0,21 MJ3001BC118 £0.41 60639 £0.21 MJE340BC132 £0.36 BC640 £0.21 MJE350BC134 £0.36 BCY70 £0.21 MPSA13B C135 £0.36 BCY71 £0.20 MPSA42B C140 £0.25 BCY72 £0.20 MRF475BC141 £0.27 B0135 £0.20 TIP121BC142 £0.31 00136 40.21 TIPI22

BC143 £0.34 80137 £0.22 TIP125BC149 £0.21 80138 £0.22 TIP127BC154 £0.36 BD139 £0.23 TIP132BC157 £0.12 BD140 £0.24 TIP137BC159 £0.12 80150C £0,82 TIP142BC160 £0.28 80185 £0.42 TIP147BC170 £0.16 80166 £0.35 TIP2955BC170B £0.16 80187 £0.39 TIP29CBC171 £0.11 90201 £0.40 TIP3055BC171B £0.16 80202 £0.40 TIP30C90172 £0.13 80203 £0.40 TIP31CBC17213 £0.13 60204 £0.40 TIP32CBC177 L0.18 00222 £0.40 TIP33CBC178 £0.18 80225 £0.42 TIP4I ABC179 £0.17 BD232 £0.38 TIP42C

C182 £0.08 BD237 £0,32 TIP47BC182L £0.08 BD238 £0.32 TIP48BC182LB £0.08 802408 £0.37 TIP50BC183 £0.08 BD243B £0.50 VN1OKMBC1830 £0,08 802444 £0.53 VN66AFBC18303 £0.08 BD246 £1.06 ZTX300BC184 £0.08 BD441 £0.41 ZTX500BC184L £0.08 B 0442 £0.41

TRIACS THYRISTORS20105DA £0.42 P0102AA £0.30TIC206D £0.65 TIC1060 £0.40TIC226D £0.73 TIC116D £0.66BTA08-6008 £0.84 T1C1260 £0.77TIC2360 £0.96DIAC £0.20

VOLTAGEREGULATORS78L057801278015790057901279015780578127815790579127915LM3I 7TL81723L200CVLM323KLM338K

£0.24£0.24£0.24£0.28£0.28£0.28£0,28£0.28£0,28£0.38£0,38£0.38/0.65£0.29£1,16£2.70£5.52

OPTO DEVICES5mm Red LED5mm Green LED5mm Yellow LED5mm Orange LED3mm Red LED3mm Green LED3mm Yellow LED3mm Orange LED5mm Flashing Red5mm Flashing Green511111, Bi Colour5mm Tri Colour5mm Plastic Bezel3mm Plastic Bezel0.3.7 Segment Display Redcommon anodecommon cathode

£0.09£0.10£0.10£0.10£0.08£0.120.13£0,13£0.50£0 54£0.36£048£0.04£0.05

£1.14£1.14

£0.47£0.48£0.65£0.52£0,52£0.53£0.42£0.80£1.78£0.46£0.50£0.47£0.50£0.31£0.31£0.31£0.19£0.19£0.35£0.33£0.33£0.36£0.38£0.13£0.1940.33

£0.36£0.29£0.31£0.31£0.29£0.26£0.28£0.21£0.21C1.35£1,70£1,82£1.73£1.80£2.32£1 .76£2.24£1.36£0.78C1.6041.80£2.11£2.11£1.60£1.52L0.40£0.42£0.12£0.17£6.21£0.3540.40£0.37£0.37£0.46£0.46£1.08£1.12£0.63£0,31£0,63£0,31f 0.34£0.32£0.72E0.48£0.38£0.48£0.62£0.53£0.44£1.5000.16£0.16

HARDWARE12 Box 75 x 56 x 25mro £0.82T3 Box 75 x 51 x 25mm £0.82T4 Box 111 x 57 x 22mm £0.98MB1 Box 79 x61 x 40mm £1.44M62 Box 100 x 76 x 41mm £1.56MB3 Box 118 x 98 x 45rnm £1.82MB5 Box 150 x 100 x 60mrn £2.50

LINEAR ICs

CA311ECA324CA555CA7410ECA747CECA3046CA3080CA3130CA3130ECA3140CA3240ICL7621ICM7555ICM7556LM301ALM348NLF351 N0E3530E356LM358NLM377LM380NLM381LM386LM387LM392NLM393NLM748CNLM1458LM3900LM3914LM3915MC3340MC4558NE531NE56614NE567NNE5532NE5534TBA1200TBA810STBA820MTDA2030T0061TL062T0064TL071 CPTL072CPTL074CNTL081TL082CPTL084CNUA733ULN 2003ULN2004ZN414ZZN425EZN426EZN427EZN428EZN435EZN448E

£0.28£0.35£0:22TO.28£0.39£0.37£0.72£0.98£0.98f0.56(1.12£1_70£0.4310.96£0.25£0.31£0.36£0.41L0.84

£0.27£2.57£1.12£2.70£0.48£1.60£0.79£0.28£0.31£0.2600.72£2.70C2.70£1 .60£0.36£1 .56£0.36£0.36£0.80£0.66£0.77£0.68£0,39£1.35£0.35£0.42£0.46£0.32£0.34£0.48£0.33£0.34£0.46£0.64£0.52£0.48£1.04£4.68£2.61£8.82£6.12£5.31£7.92

EPROMS &RAMS

271627322764.2527C64-2521728-2027C128.2027256.2027C256-20

27C51227C0106116.106264.1062256-104164-1541256.10511000-8514256-8

£4.46£4.84£3.00£2.8003.69£3.31£3.99E3.57

£3.69

£4.9701.53£3.06£4.8341.78C2.80£5.6105.61

DIL SOCKETS8 Pin14 Pin16 Pin18 Pin20 Pin24 Pin28 Pin40 Pin

£0.07£0.11£0.15£0.15£0.16£0.19£0.22£0.25

ELECTROLYTIC RADIAL CAPACITORS

uF0 47102247102247100220470100022004700

16V

£0105£0.05£0.06£0.06£0.09£0.15£0.22£0.37

25V

£0.05£0.05£0 06£0.09£0,12£0.19£0.29£0.57£1 11

63V£0.05£0.05£0.05£0.05£0.06£0.09£0.11£0.11£0.31£0.57

bow£0.07£0.06£0.06£0.08£0.08

450V

£0715£0.18£0.30£0.48

ELECTROLYTIC AXIAL CAPACITORS

uF 16V 25V 63V 10(ly 450V0.47 £0.151.0 £0710 £0.10 £0.192.2 £0.10 £0.10 £0.224.7 £0.09 £0.10 £0.10 £0.3410 £0.12 £0.12 £0.12 £0.4822 £0.09 £0.13 £0.17 £1.0647 £0.10 £0.11 £0.16 £0.20 £1.33100 £0.10 £0.13 £0.21 £2,46220 £0.13 £0.18 £0.42470 £0.21 £0,24 £0.691000 £0.33 £0.40 £1_052200 £0.52 £0.644700 £0.90

a

Antos Soldering irons BNC Solder Plug 505 £0.93M 12 Watt £8.00 BNC Solder Plug 75R £0.96C IS Watt 48.19 BNC Crimp Plug 50R £0.68G 18 Watt L8.75 BNC Crimp Plug 75R £0,68CS 17 Wart £8.65 BNC Solder Ski £1.08XS 25 Watt £5.75 BNC Chassis Skt £0.80GASCAT 15.87 PL259 5 2mm £0.68ST4 STAND £2.85 PL259 11nun £0.6235Watt Gas Iron £11.58 RND UHF socket £0.68Desolder Pump E3.00 SOP UHF socket £0.45Antistatic Pump £4.30 F Plug 8058 £0.3022SWG 0 5Kg Solder £7.40 F Plug RG6 £02718SWG 0 5Kg Solder £6.60 N Plug RG8 £1.601mm 3 yds Solder £0.62 N Socket RG8 £1.40Desolder Braid £0.87 BNC Crimp Pliers £15.50

PCB EQUIPMENTUV EXPOSURE UNITPLASTIC DEVELOPING TRAYPHOTO RESIST AEROSOL SPRAY (100044FERRIC CHLORIDE CRYSTALS (0 5K9)TIN PLATING POWDER (909)ETCH RESIST PENPCB POLISHING BLOCK

STRIPBOARD 0.1 PITCH64mrn x 25mm £0.2764mm x 95mm £0.9064mm x 431mm £3.2295mm x 127mm £1.5095mm x 95mm £1.1095mm x 431 mm £4.80100mrn x 160mm £1.60119mm x 454mm £6.20

PHOTO RESIST BOARD(G. Fibre)

£67.38£1.35£3.90£2.45

£10.80£0,72£1.84

BREADBOARD81mm s DOmm £3.06175mm x 42mrn £3.74175mm x 67mm £5.56203mm x 75mm includesmounung plate & posts £7.36

COPPER BOARD (G. Fibre)100mm x 160mm £0.90110mm x 22Ornm £1.24

PHOTO RESIST BOARD( Paper)

£0.86£1.62£2.09E2.41

CAPACITORSCeramm Mini Disc 100 & 63V

1 OpF to 100nF1pF-1nF £0.06, 1n2 -2n7 £0.07.3n3 -4n7 0.12.10n & 12n £0.07

Polystyrene 160V 5% 47pF to 10nF47p.2n2 00.09, 2n7.10n £0.12

D CONNECTORSPlug

9 Pin £0.291518n £0.3915 Pin M.D. £0.8123 Pin £0.4025 Pin £0.48

9 Way plastic cover15 Way plastic cover23 Way plastic cover25 Way plastic cover

Socket£0.30£0.39£0.90f 0.49£0.50

£0.30£033£0.36£0.36

BRIDGERECTIFIERS

W005 1.5A 50VW02 1.5A 200VBR32 3A 200VBR62 6A 200V1004 10A 400V

£0.19£0.20£0.36£0.70£1.39

x 10-

£0.67£1.24£1.58£4.63

SWITCHES3arnp 250v 6 4mrn i7 mountingSPST Toggle £0.58SPOT ToggleSPOT CO TogDPDT ToggleDPDT CO ToggleDPDT CO Toggle(biased} £1.20DPDT CO Toggle(biased 1 way) £1.20DPDT mini slide £0.15Rotary Wafer 11,12W. 2P -OW3P.4W. 4P -3W £0.78Key Switch SPST £2.70Push to make £0.25Push to break £0.28Latching Push Sgr £0.63PCB Tact 6 x 6mar £0.25

£0.60£0.64£0.68£0.76

RESISTORS025W 5% CF E12 Series £0.60/10005W 5% CF El 2 Series £0.95/100025W 1% M F E24 Series £1,72/100POTS Log or Lin 470R IMO 25rnm dia 0 25inshalt£0.42PRESETS Enclosed Hors

or Vert 1006 1 MO 0.15W £0.15PRESETS Skeleton Horz

or Vert 1006 1 MO 0 1W £0.11* PLEASE STATE VALUE REQUIRED *

MODESCOMPUTER ACCESSORIES

Parallel Primer Lead 2mRS232 Lead (all pins) Male Male

£6.90E3.75

Zener Diodes 2V7 33VBZY88400Mw £0.08

RS232 Lead (all pins) Female Male E3.80 BZX85 1.3W £0.14Centronics 36 Way Lead Male Male £4.78 1144001 £0,06Gender Changers 1N4002 £0.079 Way D Mini Female to Female £1.81 1N4003 £0.079 Way D Mini Male to Male £1.98 1N4004 £0.0725 Way D Mini Female to Female £2.23 1144005 £0.0725 Way 0 M1111 Male to Male9 Way 0 Female to Female

£2.23£2.33 1144006 £0.08

9 Way D Male to Male £2.33 1144007 £0.0825 Way D Female lo Female £2.71 1 N5400 £0.0925 Way D Male to Male £2.71 1 N5401 £0.09Adaptors 1 N5402 £0.099 Wav Male to 25 Way Female E2,71 1 N5404 £0.119WaV Female to 25Way Male £2.71 1145406 £0.1125 Way Male to 9 Way Female £2.33 1 N5407 £0.1425 Way D Male to 36 Way Centronic £3.56 1145408 £0,1525 Way Null Modem Female Female25 Way Null Modem Male to Female25 Way Null Modem Male to Male

£3.02£3.02£3.02

1619141N916

£0.06£0.06

RS232 Surge Protector Male Female £6.12 1N4148 £0.05RS232 Jumper Box Male to Female £3.02 BY133 £0.13RS232 Tester (7 LEDs) Male- Female £6.59 0A47 E0.28Data Switch Boxes 0A90 £0.07Serial Swath box 2 Way Ailil £9.20 0491 £0.10Serial Switch box 3 Way A/B/C £13.16 0A202 £0.29Serial Switch box 4 Way A/B/C/DSerial Switch box Cross overParallel box 2 Way A/B

E15.15£19.69£11.84

84157BA158

£0.10£0.10

Parallel box 3 Way A/13/C/ £17.11 BA159 £0.10Parallel box 4 Way A/8(C/D £18.43 1114149 £0.06Parallel box Cross over £20.42 04200 E0.10

ORDERING INFORMATIONAll prices exclude VAT.

Please add £1.25 carriage to all orders and VAT (17.5%).No minimum order charge.

Free Computer listing with all orders over £5.00.Please send payment with your order.

PO/Cheques made payable toESR Electronic Components VISAAccess & Visa cards accepted MIMI

Officbl orders from schools & colleges welcome

A I 11 III II II


PCB PRODUCTION: THE DIRECTTONER METHOD

Transferring a PCB layout from paper on to a circuit board iseither costly (photographic method) or cumbersome (usingsprays and the like). Moreover, the second method is known togive rather unpredictable results, but that can be changedradically by the use of a new transfer foil called TEC200.

By Dr. R. Milker

A widely used method for making..printed circuit boards is based ona photographic process. A transparentfoil with the copper track layout is puton a printed circuit board which has aphotosensitive layer covering a copperlayer. After exposing the film and theboard to ultra -violet light, the tracklayout is developed in a sodium -hy-droxide solution. Next, the copperwhich needs to be removed is etchedaway in a special solution. That leavesthe copper tracks as an exact copy ofthe original artwork.

Although several variants exist, theabove process is always marked by theuse of a photosensitive layer on a pieceof circuit board. This layer may be ap-plied with the aid of a liquid, a spray(`photolacquer') or a damping process(photo -resist film). In any case, thework then involves these steps: (1) af-fixing the artwork on to the board; (2)exposing to UV light; (3) developing; (4)fixing; (5) rinsing with water; (6) dry-

ing. The whole operation is cumber-some, fraught with pitfalls, and noteasily accomplished by the unexperi-enced. To make it even worse, the pho-tographic method is expensive,considering that, starting from a cer-tain size, a board with a photo -resis-tive layer on it costs about the same asthree equally sized ordinary boards.

The direct -toner methodThe crux is that toner as used in pho-tocopiers and laser printers has excel-lent etching resist properties. That initself is not surprising, because tonerconsists mainly of inert carbon powderand a highly acid resistant compound-ing substance (resin or polyethylene).A further advantage is the fact thatmost laser printers (with a resolutionof 300 dpi or more) are capable of pro-ducing PCB layouts at a scale of 1:1 atquite acceptable quality. Some PCBdesign programs also allow the art -

Fig. 1. TEC200 foil with the track layout copied on it.

work to be printed at a scale of 2:1 or4:1, all without the need of any photo-graphic work whatsoever.

The aim is, of course, to copy theimage formed by the toner on to thecopper side of the circuit board. Thatcan be achieved wonderfully well by theuse of a special type of foil calledTEC200, a transparent film which doesnot deform at temperatures up to150 °C. Thanks to its chemical prepa-ration, the film is capable of absorbingas well as reproducing toner. Thus, thefoil is capable of 'transferring' the tonerfrom the PCB layout to the circuitboard. With the aid of TEC200, theproduction process of a printed circuitboard is reduced to the following steps:- printing (laser printer) or photocopy-

ing (normal photocopier) 'reflected'PCB artwork on to a piece of TEC200foil, at a scale of 1:1;

- transferring the toner image on theTEC200 foil to the PCB surface,using some pressure, and heat;

- etching the board in the usual man-ner.

These steps are explained in greaterdetail below, using artwork found inElektor Electronics as an example.

Step 1: copyingThe copper track layout (reflected ornon -direct reading) is copied directlyfrom the magazine page on to theTEC200 foil (DIN A4 size). The TEC200sheet is simply inserted into the (exter-nal) paper tray of the photocopier.Since there is no emulsion side, thesheet can be inserted either way. Thecopier should be set to a give a quitedark copy, but not so dark as to causesmearing. This is best tested before-hand with plain paper. If necessary,the artwork can be made 'reflected'(i.e., not direct -reading) by first mak-ing a direct -reading copy on ordinarytransparent film, flipping the film onthe copier, and making a second copyon TEC200. Note that as of theSeptember 1993 issue of ElektorElectronics, PCB track layouts areprinted direct -reading, positive. Thatcan be verified by looking at the PCBorder number, which is legible.

TEC200 foil is capable of withstand-ing temperatures up to 150 °C withoutnoticeable shrinking. Provided you usea modern photocopier with high repro-duction accuracy, there should be nodifficulty in maintaining the original


size of larger components such as inte-grated circuits or pin headers.

PCB PRODUCTION: THE DIRECT TONER METHOD

Transferring the imageHaving copied the reflected layout onto the TEC200 foil, it is cut out of theA4 sheet (see Fig. 1). The piece of foilis turned 'image down' on to the sur-face of a piece of copper -clad board. Atone side, it is fixed to the board with apiece of sellotape. Next, the layout istransferred on to the copper, as fol-lows:- using an electric heater plate or aflat -iron turned upside down, thePCB is heated to about 140 °C;

- transfer the layout, exerting pressurewith the aid of a roller (obtainablefrom most photographic tools shops),see Fig. 2;

- leave the board and the foil to cool offto room temperature, then carefullypeel off the foil (Fig. 3).

In this way, even very narrow tracksare copied reliably on to the board.

In practice, it is recommended toput the PCB into the refrigerator for awhile before peeling off the foil.Alternatively, good results are also ob-tained by immersing the board withthe foil on it into the etching liquid.The foil will then come off automati-cally.

The layout copied on to the foil neednot be totally opaque, because whentransferred on to the board, the toneris melted again to form a lacquer -like,acid -resistant layer.

Figure 3 shows how the foil is care-fully peeled off from the track imageconsisting of toner on copper, after theheating phase. Next, the board is readyfor etching. The layout transferred onto the board is 'scratch -and -wipe' re-sistant to a certain extent, and bestprotected by the still weakly attachedfoil. That is why the foil should not beremoved until just before etching.

3. Etching the boardThe board may be etched directly aftertransferring the layout. There are norestrictions as regards normally usedetching solutions or methods. On fin-ishing the etching process, the boardis rinsed with water. Next, the toner onthe copper tracks is removed with ace-tone or similar. The direct -tonermethod described here enables you toproduce a printed circuit board from`reflected' artwork in just a couple ofminutes, offering the electronics hob-byist as well as the professional circuitdeveloper an interesting alternative totraditional production methods. Whynot give it a try - you'll be amazed!

(940096)

Note: TEC200 foil is supplied by PS Services, 217Prestbury Road, Cheltenham GL52 3ES, England.Phone/fax (01242) 254108. See advert on p. 57. Fig. 4. Ready etched board, cut to size.

Fig. 2. Transferring the toner from the TEC200 foil to the copper -clad side of a piece of circuitboard requires some pressure and a board temperature of about 140 °C. Here, a simple ther-mostatically controlled hotplate is used.

Fig. 3. The PCB after the copper track layout has been transferred from the foil to the coppersurface.



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TLX VICOM G FAX 081-552

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7414004351 1.04744074510 1.54744074511 094701074514 154744514515 3.81744074516 POA744074520 090744014538 1 02

74829974832374835074835274835374F365748366748367

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225 84951 1650

000270640.25 4.95

EEPROMS, 88 -- RESISTORS1.1440556

4056130.620.82 °09° _6613 7413 076 7410.77 044 7414-- '''"

74451637430164

0420.42

74407266 0.6674407292 1.10

7440740102 2.437440140103 1.48

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1.342.72

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0.903.73 13416C 949

0000000 28064.25 9130225 METAL FILM2.40 0.25W I%

4059640606

3.150.38

0100 1-080:01 POW

74147416

0640.48

7410.78741583

0.320.39

74153614 POA7410385 POA.8,,

74401657440166

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74107294 11074107600 1.98

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40671340686

228028

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774417

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74118656241,000.32:

774411.19:

7410393 0427410.395 POA

74404747414C1 757430181

0.420364 94

741407645 1.9874I1C40102 1 327414540153 I 12

MOUNT 748399748412748413747437

POAPOAP041,44

7401387451397744:1,40

0.97

0.9702

4,

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0A47 0 140890 Om

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24001 1.62

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4;730 0.22'40110 1.620114 3.40

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10.00000 2251100000 Y25

1009 to 255KPrice: 20.94 each

280044 20 40059011 104

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1.121.38

74151097410.1094

0.330.66

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7440204 0367410304 0.36128748539748540

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740195745240

2.642.31 8279307056.60

12 28800 2.6615 00000 225

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1 12

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4082840858

0.220.560.5640114

4°162 67240163 072

0.42

74474 1407451 0.577454 0.72

7410.112A74181137410.1134

0.660.360.42

7410468 POA74/5469 POA7410.490 POA

7430240

7440242

0.48

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0 78

0.98

74,10714 0.287440020 0 287440721 0.28

74,0740. 0.387440754 0.34743505wm 0 65

7485437485417 F 4574 5

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740244745257

45255

1.951 34

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212193C OR n1 66-

02793020 6.60BZY93024V6 60

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IMSC. MEMORIES

agegg 50840175 0.42 7470 0.54 7410114 036 74154914 POA-

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7440727 0.28 7410864 0313 748547 POA 745260 0.77 WM0333660 - - -.-24 00000 280-Tomo 0 113oom44 ' ' -

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0 2653340192

40191 P1380 62

7472 0.387473 0.58

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7410540 0807410541 050 7440244

74402450.480.08

74110030 0.287440032 0.26

730123AM 0.46743512514 0.46

748573748574

2782 78

7403737 44027

7662.66

8270301200/4S2%6109020 09 CRYSTALS104MISC.

OR.503.10011250R.

10014

6341.1) 4590.51214945(15 514

40956 07040193 074 7474 053 7410123 0.35 7410569 POA 74HC245A 7440742 0.40 741401324 0.42 74F579 859 740290 1.06 132X6023/009 Price: 23.85 erich A/4270281PC 3867,040194 POA 7476 061 7410.105 0.22, 7410573 102

7435251 0.36 7440173 0.387/84073868 030 747604 559 745283 209 ZENER /043/7 -- 101713018 1001000

40978 2 75 40195 POP 7476 0.64 7410.1254 0.32 7015574 1 02 7440253 052 730774 0.213 74351397A 0.39 748620 PGA 745374 2.17 DIODES I °X3399 699 NIGH PRECISION 102 7132LA.100P12 20400 0.04 4.0240 POA 7480 126 7410.128 0.32 5.09., 7410257 052 7440775 0.38 7410154W10 004 748624 POA 748394 2.31 "MO MINI CYLINDER gog.poggrryg 61384146 4.95

40996410484156134165044610

0.42

0 88100"''37,40374

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0.400.29oa50.781.50

874..1488,8599

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0.730.520 480.540 58

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7410085 0.647440086 0367460061887445193 0.607300107 0.4074107109 0.42

74101574 0.38038

74/01644 0 48- -744018514 0.57741017314 0.48

748623748646748676748921748823

POA3 90122POAPOA

745412 .2 31 2 4V 10 750

5584 6p each

ZEIVER DIODES500014

0.032768 0.88

WATCH0 032768 0.92

WIRE WOUND0.33 WATT 0.1%

Temp Con11.39 9"'

1404402705.3 0.804820914 POAN820126414 24938201534 5.80N925181AN 609

L, 1 7`701057sonep 134 CRYSTAL 1R.581.1014.208150R

40539 , 05026 POA 2421 2.58 74/5438 034 7415622 POA 7435290 0.92 741407112 0.42 74,1017411 038 7071325 POA 7/305 0.44 2.4% Ito 200V oSC MODULES pam t2.0..2. NMC6504.10 3.40

41740 1.20 45027 5 99- 7492 0.87 7410.139 0.42 2414623 3°4 7410283 076 74107133 064 7465221AM 0.65 748827 312 711054 033, Pe6e. 60 8440 4409306N 105

41750 1.14 45028 PO4 7493 0.60 74101394 0.42 7415624 2.1029 74HC7125 0.56 74/0240W11 0.55 747841 3.51 78058* 098

SpIn OIL 003_4203. 2503 P5101L.I 19074345040 140 74934 0.60 7410.145 066 730.625 POA 74,0290 0.3i 74407125 054 74,4c244wm 0.55 2606 060 ZENER DIODES Plastic 569 500R.114. 24. 511 1881800380 I 74

44008 05 45041 POA45100

7497 4.46 7410147 POA 7410626 POA7410627 POA

, 88' - 74401'132 aso 7302454W 0.8? 4AC SERIES 7808 134 1.3 WATT1TL 04.1puI 0K20K 11024940N 290

4410P 16 45 156 74104 0.67 7410140 037 748,03231.82 74407137 054 741025110 0.42 7009 134 2 7V lo 200V

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7460273M 05574000744502

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781273723

0.68000 .

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10550114 7507c..55044P.2 340.4F:4091:0

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7410.1547410.15S

1.230 38

7415431 POA7410.639 POA 7440356

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74407147 0.70741157151 0.52

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78157818

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0 4.9152. 6. 10.,2 03 a 2

. OMH875551748.2 4 2015.506581.15 3.60Dytuddic RNA

4419P POAV 517'2 1646 74119 POA 74/0156 0.38 7410640 POA 8'88 74400153 0.52 74140.3741W4 0.55 77 4ACtO 040 7824 1.12 7.511 to 2701/P110e, 23.66 0. T4540143131 340

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4:156P7 13 96

74121 10074123 0.138

74101577410.158

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741-V1.164 1 2074400157 0 45

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781.06

78L05A 0280 28price- -4 each

30gEg 01000524.32.40850146z

91k° 0194 96'

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74400158 0.5074101160 0.54

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0 46 7415642.1 POA735643 POA

74H,374 0.40 7414O7181 0 5474407182 0.84

74605734N 1 .097410574W/A 0.54

748074 048 78115 0.283 3g 200upr. ,...,*,,...,

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45403P POA1566.47

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7410162741016247410163

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0.300.48

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7401097401,274510,32740139

0 540.010.650.65

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20 WATT7.W

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1256-12 2 401264.15 2241464.12 4451413410 4 45

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5.108,87,, c818,8,10.,45414P POW

74153 090 7410.1634 0.647410652 POA

7440393 0 44 74400166 0 52 74404040m 0.44 74015 0 69 78412 0.70io 75V Rns spaced at 4464.10 2 80 ea VOLT

4497p 098 74154 2 60 7410164 04073'4669

74Hc4230.51 7444C1173 as2 741040464 168 740153 085 794124 0.70 Pace 04.94 ea comets 0 8031311 14256470 3 90. Case Size 1206

44998 696 74155 OBI 7415165 0 50 I'59 4 47 1052 POA 7471C7174 0.52 7414540601A 0.16 7 pc 374 I 0.81 7954138 140 BRIDGE crag.. m6. 025602.10 695 12641 25rnm450013 15.00

ar 74157 0.74 741S1643 0.50 7410.670 0.78 - _-730533 0.98 74407175 0 52 74104066W 0.e4 7405158 065 78415 078 RECTIFIERS 3.6884,8,10,124X254400055 845450410.3 0.44

RFA 74158 1.57 7410.164 POA 7414673 3°A 74140534 0.8 74115118t 3.24 7440163 090 78505 1 10 0.94/200VD11 Mar 04.99 *ash HM48418AP.15 1098 UP` 3.3..0 4,I3F

450284503845048

0.560.481 361002,8740,,,88.

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74159 3.0974180 0 94741614 0.74

741016973_51707418173

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7410540744054174,40563

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0 68

0.383.04/200V $11

0.5716.332432405:042Prloa: 33.84 each

0.60HM48416AP.20 4 25H45302561580

10008.22044.13548

'WE 'W°PF MX°33300.4760,57

450513 POA ."- 0.324011UE17 0.32741S68574163 128 7410.1734 0.52 7410684 3.85POA

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7445191 1 38 79054 098 64100V 011 100308.22030PFMOM,M anew

POA1535464158045068

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74164 1.1674 166 1 67

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74301193 0627 4400194 1.20

v 4474606 0.74

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1.0984200Y 511

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05088 1.68401561 014

741136 1.013

74174 1177410.1827415183

POAPOA

7410687 POA741_0688 10.8

7010574 0 84 74400195 1.2074351221 066

74807 0.7474808 0.26

7402447410245

0.921 10

791279124

068a9e

Sealed MOM410 Pkg

671351100045 8 451.g6670330 10300008Prim 189 each



MICROPROCESSOR& SUPPORT ICs

1001140E2 74010014100 aeo6303XP 8.766321P 4.41

63485CP32/SM 19.9563803X7 10.078502 3.768502A 3.98

0596390 1.98EF6821P 1.68EF6850P 1.68EF613/309EP 5.35EF68509P 4.73EF6802112 2.56EP610PC-35 POA401.0165-5 10.96HD146518AP 4.41003-6402-9 116I -03-6440S 189

PIC16C57RCIP 5.0001216064-04/P 13.98P1215264.200 23.85P1C16264-JW 3a88P1216271-160 194PIC16C84-10/P 1224P1217242-16JW 35.51855020P 5.9186520P 44086522 4.40R6522AP 5.32

SGS7P050 4.55SP145OB 176U101813029E1 680ULA2ORK008E15 972XR-T5683 160ZNA2L029J-BS 360ZNPCM1J-BS 8.95

C17652BCPC 824CL7652CPD 124

L7650604 268L7660SCPA 2.96

CL7662CPA 335CL76638CJA 578CL7663BCPA 5.10CL7664CPA 7,95

4,47CL717320A 1 260180520070 8.73

LM350T 4.7715351N 2,60LM35851 0.36LM359N 2.84L513606 7.72LM361M 5.40LM363H-100 18.50LM369051 3.821143690FIC 170LM3805 1.98LM381AN 7.88

NE5532AN 2.02NE5532N 062NE5534AN 1286E5555 0.40NE556/SMO 1.22NE5565 1.18NE558N 2.62NE5655 3.75NE5655 204905670 0.91555685 POA

7107402N 2.40TL074CN 097TL081CP 0.74TL08225 0.81TL084051 0.84TLC2712CD 1.9811497ACN 3.95TL507CP 5.98717702007 1.22TL77054CP 1.22717705CP 1.22

75176A 2.69751765 1.86751768T 2.1975177 2.6075178 41475182 2.9375183 23375188 0.0575189 0.5875169A 0.9875361 3-24

807430 1.9050185 1.1280)(628 2.78BDY966F195 -C 0.08BF199 0.22BF200 0.16BF2566 0.38BF258C 0.3613F259 0.40BF324 022

Personal Computer Products

MOTHER BOARDVESA 986 3V1slots,256kCache C 85

with ZIFF Socket for CPU and8x32 & 2472Pin SIMM Socketsaccepts 4865X/00/0X2-66 CPU(w0551 CPU&DRAM)

MICROPROCESSORS80486SX-33M07. INTEL £ 75804860X-33MH6 INTEL 2 125

LINEAR & MISCS.CL7665ACPA

35555M/55 345

6520P 4.40 003.6495-9 8.89 1965202P2 6.5449620/663 700CL8058AJD 1149 L53852.1.2 1.98 555705 7.53 TL7709ACP 2.04 75365 310 6F421 0.12 80486002-66M0z INTEL £ 160

6522 9.40 9044883 POA R65CO2P3 7.16 555-1151E8 0.40POACL8069DCSO

2180692200 419 LM385Z.2.5 1.98 NE571N 4.96757770-SC 3.82 75437A 3.26 60450 0.20 Heat Sink + Fan for 486CPU 2 10

6522A 5.32 6046505SP POA 06520274 13.956341-IJ741-0PAMP 0.18

283 LM386MI 1.65 505890 4.25 TL783CKC 7.53 754508 0.66 8F451 0-22 HARD DISK DRIVES6551 4.438651A 5.20

0346802P POA1-1063217 4.41

865010272 6.78865221132 5.46

40520361 POA270MBCL/3069DCZR 2.21CL8211CPA 149

LM38614/1 1.28LM38655 1.80

NE592/SMD 1.80NE592N 2.05

71215411N 1563TLC2201CP 5.50

75451 0.66754516 095

BF494 0.16 13msec 35" LP 0149

8.546520273 7.16

H0634850532 32.50HD63803XP 11.74

06522202 6.5136580232.16 6.98

AD524 21152AD534JH 48.27

018212270 274CM71701PG 114

LM386N4 2.60LM387AN 5.20

9E592514 2.005E60246 2.98

11222742N POATLC251CP 428

75452 0,665'65754528 0.98

BF759 0.2665202P2

BF9519F981 890

340MB 13rnsee 151 LP 5 179FLOPPY DISK DRIVES

65C102P2 8.78 /106800078 11.59 SAB80C32P 4.28AD537JH POA 25720741PD 10.35 1538861 4.25 NE604AN 8.98 710265207 198 75453 168 8F982 0.88

1.44MB 3.5' 0286522272 6.5165251E1 5.60

9068037 7.98HD6845SP 4.86

SA880253541 12.24SA88155 11 3.82

AD548J5 2.06A05746K0 54.57

CM72071P0 714CM7209IPA 6,99

LM389N POALM39005 1.02

NE6055 11.85NE612AN 3.40

TLC2654CP 598TL22712P 1 20

754536 0.9575454 0-05

BFG65 1.79BFR53-20-1. 0.48

1.2MB 125" £38GRAPHIC CARDS

652515.2 6.20 HD68552111 P06 5088259073-5° Pw°5A, CM7211AMIPL 5.25 1539096 2.12 93882113P 12.06 TLC272CP 2.18 75454B 0.98 BFR91-5OHZ 0.62 ISA TRIDENT TVGA 89000 1M13£ 4865000CP-12 9.65 HE/68621P 3.53 SAB82254-2-P 4.12

4A0D55878.57jHN5.52

97AD5815CSA 9.CM7212AMIPLCM7211MIPL 175 LM39146 3.25 070703 3.60 71227220 2.29 75462 1.31 6F591A-130621.20 ISA TRIDENT TVGA 9000 512KB £ 28

68000CP-8 8.786800015-10 7.41

0132159.5 20.985113-7159A-5 23.40

04882255A -2-P 4.00SC8024512C564

81158550 31.552572131PDA0592251 POA

6.129,11

LM393N 0.56153937 0.96

0007268 1.400707078 1.40

TLC274CN 3.0971033905 2.58

75463 1.1075468 3-15

8FW10 1.20

BFX48 0.49

VL Bus Graphic Card 1MB £55expandable to 2Mega Bytes

68000P-18 18.20 HM10422 14.30 1160 0055100 1655C5721650630.89 LM394CN 4.80 0P07EP 3,10 TLC372CP 1.95 75469 POA 9F885 009 MEMORIES (SIMM)

68008P-8 9.8568007 5.70

0822869 17.0656402017L 10.20

SC8725122E40 31100C87C51CC290 31' 95

00595AD 15.240064836 3.09

CM72175651 8.42C505721761311298

LM3999Z 3.21

153999 6.68OPIIGP 8.68OP177FP 3.71

TL2551CP 4.62TLC555CP 1.44

75470 PO475471 3.35

85588 0.908F489 1.59

i Mx9x3 CHIP 7Ons £ 2815 x36 (4MB 72P1N) 7006 £109680100-12 POA M640217L 7.75 SC52661021528 POA

00707J51 5'56CM72171J1 15.26 LM42501 11,82 OP27GP 4.17 1125552N 2.53 75472 8F750 0.34 2561Kx9 3 CHIP 8096 9 12

6802P 3.90 M64031PL 12,92 5C5266122528 POA60711.151 2'61

C57218613 9.30 LM555CN 0.68 OP42R 9.08 TLC7524CN 5.98 75473 3.35 80452 0.3488030I/O6805E3E 14,75

MS2600P.15 4.985082505 7.80

10625525N POATMP700251-2 4.97

40712354 3.57C5721841151 1682517218019 1195

LM565CN 2.481.111710CH 1.71

OP77GP 3.230150720 1.92

TLE2061CP 000TLE206220 POA

75474 2.2575477 210

)36-y00 0.9280107 0.28

CARDS with CablesIDE 21-1012F01201P/IG 5 15

6809P 4.AD724539/Kel5552505-B 7.90 TMP8085AP.2 5,98POA

80736M 6.21C547218E51 14.76 LM723CH 1.63 PCM63P-K 35.80 11E20642N POA 75491 0-80 80170 0.38 VL/B mob LaCard £ 25

138107 h15M82C51AP 5.89 TMS320CIONL 9,32CM7224IPLA074155 3.69142 LM723C,N 0.72 PM7548HP 17.99 TLE2161CP POA 75494 3.88 5825o KEYBOARDS 8 MICE

61521P 1.68 M558225412.6 657 75532022505L 17.23AD7523101 9 BD

CM7226AIJL 37.20 LM73308 2.85 FIC41365 0.80 T55347751 168 75855176 4.24 05860 102 UK Enhanced KeyBoard £ 1768407 3.22 MAB8331A612P 4.23 TMS320625GBL 7158 3,5,, 555.--"'" ..''''''

CM7226BIPL 3252 LM741CJ-14 2.20 8241945 2.15 TPIC2406NE 7.14 75ALS192 4.72 8SX20 0.38 102 UK High Duality Keyboard £ 256644P 17.20 MAB83351-1126P 158 TMS3477NL 6.68

6075371.51 POA2572491DM POA LM741CN 0.45 RC4207ON 1.92 TPIC2802KV 9.42 75ALS193J 4.72 80521 0.48 KeyBoarcl

6845P 4.86 MC10103P 2.89 TMS3700NS8 878 AD7542KN 39.35057555185 199 LM747CH 2.40 8C4558 0.91 TPIC6259N 128 7521154 4.06 BSX61 1.85 3 Sutton Serial Mouse £ 86845SP 4.86 812101151.. 385 TNIS3702ANS 8.78 AD7543JCWE POACM75551PA 018 L51747CN 0.74 RC455815 0.91 1P1062735 3.28 7501406 3.51 05136-600 1.10

680097 4.60 M010115P 2.89 7553835055 7.55 00757866 5051057556170 1.16 1578007 1.80 8160012P 3.48 771065955 128 752188 3.98 60546 9.94 IMPORTANT

88421P 1.98 M2146805E2P B.53 T51077601 NL 10.740084405 9.71

5640317E 12.92 LM79GCP 1.80 FIEF016P 7.40 752426270 POA 752188 132 Buz), 1.60 All prices are excluding V.A.T.684407 2.56 M268000P12 PDA TMS9900NL 24.40 ADC0804LCN 3.98

L272 2.74 LM833N 1.31 REPO2CP 4.96 TSC500CPE POP 752189A 232 BUZI1A 1.62 Postage &Packing Charges684507 2.98686007 7.68

MC68000016 18.20MC68010P10 KA

Th10990156 14.16TMS9902ANL 15.94

ADC804LCWM 12105252,8 2.3852838 3.82

LS285AB 2.40 REF03GP 5.42REF25Z 0.98

TSC7106CPL 681TSC7116CPL 7.68

75210980 23275182176 4.14

BUZ47A 6.901RFZ14 1.14

£3,0010r orders upto E40 exc. V.A T.688097 4.73 MC68010P12 POA TMS9914ANL 23.10

A0208202(55 19.93 529, 3.27 157210 POA 525600 POA TSC7126CPL 128 113F220 1.77and

688217 2.56681340P 3.20

M06802P 3.95MC6821P 509 T5159928056 7.40 ADC0834225 10,80

ADC84KG-10 38.9809, 6.90,..20,20 7.80

1T1006CNB 2.72LTIO10CT 4.58

504.1027 5.955001043P 9.60

TSC7650CPA 1.40L/10968 4.92

J113 2.39.1175 IN

MOO for orders over E40 cac.V.A.T.applicable to all goods under SoTRANSISTORS

60800 POA MC68407 5.05 U49636ACP 2.66 ADC908HP 18.42 L4805CV 3.40 117028088 7.98 50030497 10.98 520668 2 64 THYRISTORSJ270 D.92

heading of'Personal8085AH-2ADDAC80N5.98 MC6894P 1140 U6963701 2.363.76PDA

036201AM 7.59L487 11103220 4.70 MA50250 9.40 524006 550 & TRIACS

10101 0.48Computer Products..

8086 11.9280862 11.92

526845P 7.3854268507 3.35

549538CPU09639CP 2.38

ADOPO7CN 1.924510015219 17.20

14982 2.7917028

LT1070CT 10.98LT1083CP 8.82

50060020 10.80SAS560S 3.40

5022402N 2.79UA2240PC 279

MBD501 1.10MJE13070 1.10

POtilego & Packing will be charged at

cost for all destinations outside the UK.40406 1.60

80C286.81PLCC24.40 5068705837 25.35 05468456 435AY -3-1270 3.00

Uk6358 POA LT1086CT 3.91 SED2000FVA 9.60 5070907 0.85 40673 2.400.88 V A 1. 5 payable on Posatage 5, Poc585.

80C32-16592 6.98 MC68A0OP 712 559151 POAAY -5-1013 4.60

106510 4.88 17113405 8.14 SFC2301402 178 5070970 0,85 80107N8 517 50.16350 10 11==802327 9.28 50680097 712 UM9151.3 POA 07-5.10136 5.981.58320 5.22 1701052 7.97 502274102 030 5671560 4.50 861584i5A4'17 51J6520

802856 5.9180035A-2 697

MC68H205E0F61116MC8.314P 660

UP88238 POA0088282C 4.98 AY -5-1250 POA

5,5,32 POA5,5522 8.97

LTC1099CN 14.39L10485CN8 2.60

SG35245 1.66017560081 1.92

UA723CP 0.705673323 2.985100405861°9-646 545

60140.10 0.48MPS3638 0.18

0.12

New ReleaseA to 11 Converter with Software

5118-5251 7.6082254-2 4.10

MCM6810P 4.9852568410P 7.42

U05828460 4.9851508286C 4.98

67 -5,36510 -PRO 9.96006109 1.68806208 1.40

5,5088 9.7810111803 POA

112490 4.40M5218AL 3.20

SL1452 7.8501_23640 3.97

155741MP D.601.14741TC 0.28

80146810',,,99

82145 "4"'500013 D.12MPSA83 0.32

Introductory offer 5 85 eachask for leaflet for lull details

9313402 7.08 M5532006 4.73 570701082-10 9.10CA3046 5.54

L0'135080 13.65 55220 6.21 01.31176 POA 5074807 D.98 82157 5-54 MPS592 124 2 01911DIsplay Board for Turbo PCAM25LS2568P 2.68 51458167M 13.65 5PC/701082S 8.95

CA30413(SMC)55'6655

LF3116 8.87 M5238L 3.98 SL4860P 2.82 1.15,7700DUIC POA 86158 0,34 mpst.i05 2.21 Delays I 10 99, Jumper selectableAM25LS2569P 2.68AM2602PC POA

MA/581744N 14.82MM58274CN 9 59

UPD701162-10 12.9050070119c -a 9.20

CA3054'

CA3059 215

LF3476 1.34LF3515 0.48

515298P 6.22M706B1 1.92

SL490DP 2.60SL560CDP 2.62

1/6798TC 3.801:C5151300A 2.63

82168C 0.1450179 0.24

MTP8P08 2.80MTP8P10 2.80

Can be wired e.g. 251511-6 6 66541-15

48x56mm Special Intro. Offer £15.956526103102 2.30 M5M583285 511 500710550 4.77

CA3MIAT 3'94LF353N 0.61 MAX134CPL 17.95 SL6270C0P 297 06558014 3.96 82182 P53643 0.18 80195 7 Seg. LED MPX Display

AM26LS31 PC 1.26 MSM80235RS 410 UPD7201AC 693CA3079 1.20

LF3556 1.26 MAX1232CNG POA 516700CDP POA UDN2981A 3.15 861,2A 0. 1121065 0.78 Board fitted wft112x8Pin OIL HeaderA5276191602 10.20061270281PC 9.62

MS5480239350 145MSM80239RS 755

5707201050076562 5.42

263080E 0'9°LF355N 1.33LF357BN 2.98

MA01232CPANIAX1259CPE POA SN55451BJG 2,85

060129824 3.02U0561186 2.13

801828801821 0.08

TICP2013D 0.61 size 15X61rnm, supplied with HP

AM2964806 12.36 MS5802850 511 500784C.1 4.76CA30816630896

1.191.88

56365,0 2.40 MAX16242NG FDA 00212 122 00935015 700 B2182113 0.08

86183 0.08

TI201080 0290.55

1-10013 -7511 01' (7.6mrs) Oisplays.use Coin. Anode Display DriversAM296502 10.68 MSMI302850-2 5.98 UPC/8023911C 892

C03094AE 2.16LF3576 1.33 MAX232660E 112 SP16485/13 160 ULN2001AN 0.58 700121 0.68 ICM7216452 or 12517218/VCIEULale.0M2956P0 4.97 MSM80286 7.60 570815590 5.84

243096ELF398N 3.77 M0X2320PE 2.54 S74534 POA 55520026 018 001830 TIP145 1.32 Kit: C1866 Assembled( 524 ea.8529828X 5.98

AM68501 9.82AM8238PC 5.60

MS11481655 4.60555182251A 487MS582253-2 5.28

5708251600082536-2 3.98U0082532.5 3.98

CA30976.55t'''"CA3120E POA652050613B1041125 1.22

LF412CN 1.69LF441CN 0.82

MAX232EWE 360MAX23219 4.98MAX2802PA 6.94

57474007 446SP8560DP 496S7K414111 520

515200305 0180L5200405 056ULN20244 POA

D61831- 0080.

80188 0'09821949 0.08

7172955 0.88-81030 0.48-0....=

5D8

Vaccurn Fluorescent Displays20 Digit 557 Dot Matrix

AM9050CDC 4.95AM9050CPC 4.60

M5582253-5 138MS582254-2 4.20

01808286C POA0008741AD 12.52

,---'13"`" .`'-'

0.810A3130EAllCA3140AE

LF442251 1.48LF44406 135

MAX452CPA 138MAX627CPA 3,40

ST65151 1500STK417111 7.10

81520320 POAU15280165 a84

nng861841- 5-55--

86'941-C '''...

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591SE Japan, 175856mm C32 eachSpecial Products: P&P 61.20

059102070 2.82059114805 9.96

535822550280 5418MS10822595.2 3.98

UPC/87496C 14.74420-10562 9.10

16°043140E 5420.9819000205 13.04

15100320G 35,96MAX660CPA 6.30MAX59046PA 4.66

01564181-V 9.60076419211 7.60

515280305 0.84555100 1804

56212-18 0.08802120 0.08

11P47 0.806275LA10 192

254401 a18 2581052 1.20264403 0.18 2061155 1.5205955170 9.66

66196102PC 3.35MS54822844 4.42M05822844-2 9.95

020.8MHZ 8.95V30.1 OMHZ 12.90

243160E 1.49CA3240E 1.27

15110106 3.44151005 7.24

50069307E 6.6850X69427A 5.70

070427701 10.807072157 7.20

555101 4.520022110P PUS

862128 5'5BC212L 0.08

45010453 0.92VN66AFD 140

254921 1.40 2081238 0.82265401 0.16 2SB750A 1.60AY -5.5135 5.45 MS5482288 12.60 630-8MHZ 9.20

CA3240E1 3,00LM1119 5.21 M05697CPE 159 TA725814 2.60 X18110KP 11.54 8621215 5557

86213 VN90AB 296 255415 0.72 .255834 1.04AY -5.8136-006 6.4501164/SMD 4.98

51130C286-10/151 24.505802286-12131 2954

46103O7 7.8062010668 160 CA32606 3.04

15113600N 1.891513700N 1.58

MA/4721905G 7.88MAX8211CP0 2.28

7073687 POA7476587 1.20

31112/11 9.60YM36238 15.48

5545BC213L 0.08

V00104-513 0.92 255449 0.88 200949 1.48

C132316 59.00C8253 3.60

580L285802 36.20518235N 368

X6862055E/F6 11.95Z0800110PSC 1890

CA3280AE 5.94003260E 3.42

1M139115 1.985,5,335 3.95

MA090156130 POA5401377P 4.93

707800507 0.48TA8200AH 7.82

251034E 2.6625414Z 1.20

82214 5.5Y822141 0.11

40010042 0/8VP010453 092

255459 0.53 20E3950 1.40255485 0.48 2061079 5.80

CA8028513 5.980282685 9.62

58264N 3.685825 12805 5.58

Z0868112PSC 3.202180-MPU

CA555GE 040.

2A74 ICE 0.18LM14586 0.59LM149651 2.26

M214137 0.7450144117 14.25

TA84100 2.807084497 8.31

25415E POA25416E 2.32

062375°5'55

86239 0-15

2TX212 0.18270237 0.26

255876 1.32 2021115 4.00256034 172 2501129 0.48

CD820861-18 9.74CD156818AE 8.32

5320181F 10.0455164505 198

28001 B -CPU 11.96Z8018008VSC 825

CS5503-KD POA0.086075258 5555

LM1801N 7.92151188114 4.48

M014416L PDA50194957 6.98

70865905 12.227008610 FDA

Z5423 2.2025425E8 4.95

6230786321 908

ZTX300 a18ZIX,313L 0.28

256037 0.72 2501213 0.40256050 112 2001279 1.10

C0518136 8.45 NS15550AFN 12.60 Z80A-CPU 2.79D1692.1 POADAC0800LCN 3,40

1M1889N POA MC145406P 2.80 11361200 160 ZN426E8 135555

06228 5-55270320 0.38210510 ale

256051 149 2001318 0.60256054 2.20 20017905 0.4060581217 9.41 552800N-1 10.80 280A.CPU/cmos 3.97

DAC0832LCN 5.6015118945 POA MC14557 1.20 TCM152000 POA 2542708 11.35 862557 5.5555

8235625 D"270550 124 256056 1.94 20217410 0226P82254 8.42 P803246 4.62 330A.CTC 2.98 0000807 3.53

LM2186 POA 52145571 1.40 T6M1531P POA 3542806 6.40 215(551 0,36 256057 224 2801775 028CRT6009-001 9.85 0805104 11.20 280A -DART 49400008E7 4.85

152395 3.90 MC1458P 060 TCM1705AN POA ZN429E8 1.913 86485 55-2486450

TRANSISTORS 256058 268 20611345 028608205 8.9203232 188

11.92

P8052AH9BASIC24.99P80806 P00P80856-2 5.92

280550MA 1402800-710 2.60

DAC1008L2N 10.73DAC1222LCN 20.40

1529064 0.86158290351 0.86

501488L 2.405161488P 0.42

70531055 94272550875 144

25432E 21.492154480 2,05

5,3586516 12256017 025

THYRISTORS6 TRIACS

256109 178 2062009 0.44256125 2.88 25221805 8.98

08086 280601010 4.76DF1700P 17.91

15.4290451 016 M61489AL 2.25 10M5089N 3.44 254490 175 2 22196 028 256388 0.98 2022235 0.4008086-2 11.92 P8085662 6.88 28066051 2.60DG201ABK 3 83

1M29175.14 6.10 MC1489AN 9.80 11261023 230 Z5A134E 18.72 0254 0.05

86546A252222 a28 255517 034 202223810 0.76082020 POA 08088 8.80 2808-605/0503 4.66

243211CJ 1.361529176-8 3.64 M014891 2.20 70A1083 3,40 ZNA1345 12.73 0.05 2522226 0.22 256519 034 2022238B 0.708254-2 5.42

082846 3.90180231136 6.26080632/161EL 8.30

2130/3-6142 3.027808 -DART 4.93

06508AC41 3,47555,,,3.2555°2

L5429402115 POA1M2940C15 POA

MC14897 9.2851614965 1.76

70010850 3.80705110350 180

ZNA234E POA 865488 005BC547 0.08

252369 0.242523698 0.24

255668 1.40 2062240 02425696 am 2522275 0.64

75 SERIES08288 6.480826284-12 9.60

780251FA 1682P80C86AL.2 12.60

2808 -DMA 15042808-P10 3.00

0514885 0.800014088M/SM01.65

151298461 4161530105 0.54

5015581 3.325016487 12.40

TDA-1151 1.8870011708 154

BC547A 0.080654751 008

252484 0.32252894 0.75

25706A 148 2S222754 0.88256129/1. 5.24 2662278 1.180822284-8 7.85

0826288-10 10.961815514/2 6.9878205 2.60

MOB -010/0 4.92280600488 338 0S142885 1.47

LM30751 0.961M30851 0.91

510165/30 12.78MC17092151 1.20

70015150 4.9870015210 4.98

75107 , .68

751070

56547C 008832548 0.08

252905 0.32 2SK246Y 035 2522352 0.34

0826288.12 11.850822288-8 9.360874815 10.26

P8228 2.40P8228 240182518 415

284042 CMOS 6.602868131 6.79

D01428966 1.47HA12017 1-561513426 11 96'

5),..,31, 2.56LM31151 0.38LM311N-14

50172307 1,2050174167 0.45

11041576 4.9871.5115786 4.81

18875108 1.42

751080 184BC548B 8.08BC549 0.08565490 0.08

2529058 032252907 0302529070 0.302022577

35545 1.85 2522359 0.3635588 184 2022497 1.20

JAPANESE 1.842522579 3.20

TRANSISTORS2S22591 1.38

0782285 5.83015823851 6.72

78253 9.70P82556-5 3 90

LECOM &SPECIALFUNCTION ICs

9017723 1.4060751897 0.80

2.15,m3,2,4 8.95LM317AT 2.40

510324267 7.545033017 2.60MC3302P 2.46

7DA2086/A POA7002595 4.411043048N 1.85

751088 2,08

751098 2.4675110A 2.43

86555 3455BC550B 0.08

2N2923 am2N2243 a7e

2062603 0322140048Y 0.14008304BN 2.99 P8259 ass HEF4754V POA 5,531.8y 0.76 MC3340P 3.75 TDA3505 PO0. 75113 2.02 665556 5555

253053 034

013831114 8.51001221 8.11

782590 A05P8274 16.71

6200891518 am7071502020 5.25

HII-0201-5 6.4311111086-5 11.21

153171-17 2.645m3.000 3.12

51033577 3.95MC3403P 1.40

MA3810 POATDA440 POA

75114 2.2675115 2.26

86556 5.5880556A 0.08

253055 0.98253441 520

2062705 0442SA1096R 0.65 2522928 4.822501100 D.

DS1231-20 5.50051232 4.12

P8279-5 3.202.64

733W00124 5,25AMA1503608 418

1-111-549-5 POA1-111.5745110.5 42,50

455.5251.5 5'55

5,53138 2.68LM32OLZ-12 0.34

5103446AP 6.7554634797 7.92

7004510 3.381064563 4.98

75116 8,542.5975121253702805566 0.08

06557 0.08

253553 0.98253684 1.880102563182N

25231805 2.382061102 2.10 206318115 2602061104 2,40 16400348156 1.74

0534875 1.74

0828608286 3.60P82254-2 6.98

BAA1505551essey 2.20CLA25106PLCC 5.95 613-0509A-5 FDA

LM324AN 3.745,324, 1,71

MC3523U 5.80MC4024P 12.78

TDA4660 6.6011:6165797 POA

75122 park75136 FDA

965570 0.0886558 0.08

253704 010 2061111 D,882523243 ass2041115 D.

DS3428614 2.94 PAL1OL8CN 1.90 05105001G00 320 61111 2AD LM324N 038 NICT2 0.98 T0070107 PDA 75138 0,54 805580 0.08253705 0.10 2SC3281 272

2061145 0.4OS3428751 2.94 PAL12H6CN 1.90 KR9500P 1552 510574-40 1120

617104-18015126.085,325N 109 56111 1.18 1057052 2.52 75140 135 605555 544

253725 010253789 2.11

2523284 5.002SA12635 2063377 0.24053631N 9.35 PAL16154-15CN 298 50-49258/7100 5.92

617106071 310125133010 2.60 MF1OCIGN POA 1068702 8.22 75150 1.39 805595 0.138 253819 0.54 2SA12645 2.602003581 0.580336325 3.94 P611664865 117 MJ1454813 2.,

017107206 5.205513342 1.71 ML924 4.90 7E51045 POA 75150M 539 905598 0.08 253866 524 200126551 2.60 20,36.8 0.44

0S35335 3.9205363414 3.44

0412011025S 4.35P412005656 132

MK51755 3.80

06-147.7 2.40 6171090P1 11946171150151 853

5,533521.62

LM336Z-2.5 1.48615530951 5.75555310514 4.98

1E41060 4.201065620 1804

75152 83675154 1.33

805600 0.08665666 0.08

253909 0.11253905 0.12

?501283 0.28 200373 0.442S41295 7.32 2004987 4.2005369151 3.04 13208584P 12.22 PE30352303 6.40

CL7117CPL 11.02153362-5.0 1.48 55802955 1.44 TIPC2801KV 8.79 751545 1.39 001840 OMB 293200 050 2081302 3.74 200458 0.150038625 16.98 70085641 12.22 77342108 6.80

6171262PL 11.02553355 1.12 57757030 POA 7102607 1.84 75155 3.06 96771 0.22 253958 2.12 2061399 0.58 250485 1.88D0500012-12 3POA P6F8566P 8.28 04704 3.60

CL71352P1 12.1915133980 2.37 51002460 14.82 71062651 1.26 75157 4.40 50131 0.88 254037 148 2501482 0.78 2004, 5,

0056405 1.71 PCF85661 8.28 OMV16BP5 7.986L71362P1 11.02

5,333, 034 MUX24FP 14.82 TL062CP 130 75159 5.45 BD135 0.44215405 2.30 2041515 0.78 28,92

DS8820A14 1.920088325 3.

PCF857012 8.6370 085737 964

OM6182 8.80

Q5/182511 7.85 C17137CPL 11.02C67606215 12.24

L0.13400112 2.051613401-5 0.70

M650000 2.865660100 4.96

1106460 0.987L064C5 0.84

751806 6.15

751618002418 0.98130242C 0.52

254052 0.32264091 0.28

2061516 3.24 20,8380 1.06255733 250827 0.600058366 2. P6F8574P 7.18 054V18CW1 7.85

6178110608 1.41L7,4340112 0.70 516887037 7.96 TL06410/0513 2.10

6.157518M 55 212/243 0.50 254123 0.16 2568546 0.52 3062,8 0. 88

008837N 2.0300883851 2.750095366

PCF85741 718PCF8591P 1226PIC-16254542/P 3.60

0516256 8.42OMV62AW1 5.905453465.91 4.20

CL752100PA 1.98617622 POA017650670 5.68

1114340115 0.705,3438 9.22LIM34651 4.12

NE502015 11.68NE52751 4.635E5325 1.81

TL071ACP 1.57TL071CP 0.7811072007 1.041110720N

75172 2.46

75173 2,675174 2.48

60516 0.7860675 0.52130676 0.52

254124 0.20254125 0.192514128 0.32

256853 024 3S2826 0.822SA933S 200853 2255965 0.80 20,802

059637,400953855 118

51216255552(P 448P121625651255 442

64336931 3.22

SCM66115P 4/8 6176500600 5.8511143481515 0.64553625 164

NE5368 4.90NE55305 3.82

1727107227 130

75174510 4,21

75175

80679 054131)680 am 2542218 2 96 204968 5 256945 020

2509702.80 254236 3.72 0.322609710.313

We stock Capacitors, Resistors, D & DIN Connectors, Headers, LED & LCD displays, LEDs, Relays etc.

VIEWCOM ELECTRONICS PLEASE ADD.£1.20 P & P and then 17.5% VAT. OFFICIAL ORDERS from Govt. & Educational Establish-ments are accepted. VAT at 17.5% is chrageable to all orders received from EC Member Countries unless

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16

MIDI MULTIPLEXORDesign by P. Rigaill

Musicians appear to have a predilection for connections, aswitness the myriads of cables that can be found around and

on the stage when a pop concert is taking place. Themultiplexor described in this article enables interconnecting

of a number of MIDI instruments quickly and tidily.

Modern music groups make full useof instruments that generate elec-

trical signals or need such signals to gen-erate sound. Organs, synthesizers, se-quencers, amplifiers and what have youall operate with electrical signals.

Fortunately, nowadays there is a stan-dard, MIDI (Musical Instrument DigitalInterface), with associated protocol, ofwhich many musical instruments makeuse. Computer manufacturers have alsotaken the MIDI route, with the result thatcomputers are eminently suitable forcontrolling musical instruments. Theonly damper on all this is that these newinstruments need many cables to inter-act. Loose lying cables form a dangersince they can be tripped over and are eas-ily damaged. The multiplexor enablesstraightforward connections to be madebetween musical instruments that are tobe linked via a MIDI.

The multiplexor may also prove of useon the domestic scene. Computer userswhose computers have a sound card withMIDI connection can use the interface tobring about electrical isolation in thesystem, which obviates the likelihood of

damage to the computer when experi-ments are carried out at the MIDI output.

How it worksThe circuit diagram of the control panelis given in Fig. 2. The signals from the MIDIare applied to DIN buses K1 -K4. This digi-tal serial connection operates at a baudrate of 32 kbit/s. The interface uses cur-rent loops of a few milliamperes. This de-sign enables distances of several metres(up to 10 ft) to be bridged.

The LED in optoisolators IC 1, IC2, IC3and IC4 lights in rhythm with the digitaldata stream applied to the MIDI input. Itis protected by a diode in case a signal ofwrong polarity or a direct voltage is ap-plied to the input. However, this risk ex-ists only if home-made MIDI cables areused. When proprietary equipment andcables are interconnected, in principle,nothing can go wrong.

When the LED in the optoisolator lights,the associated phototransistor conductsin rhythm with the input signal. The out-put of the phototransistor is applied toone of four buffers in IC2. The buffered

digital MIDI signal is then available at theoutput of the relevant buffer.

Each output of IC2 is applied to fourmultiplexing circuits, IC6-1C9. For in-stance, IC2a is connected to pin 10, IC2bto pin 11, IC2c to pin 12 and IC2d to pin 13of these ICs. All four ICs are thus providedwith the four MIDI signals applied to theinputs. It should be noted that only halfof each IC is used in the present circuit.One half is disabled by a high level at pin1; the other half is enabled by the signalat pin 15. The outputs (pin 9) of the ICsare linked to the associated MIDI outputat all times. The four MIDI outputs areavailable at DIN buses K5 -Kg.

The output of HC devices can be useddirectly for generating the signal currentin the MIDI. If standard TTL devices hadbeen used, buffers would have been needed,since in these components the level of alogic low is not low enough, which wouldkeep the currents in the MIDI connect-ions below the required level.

Each multiplexing IC has two controlinputs, A and B, that are driven by a 4 -bitcounter, IC14a, IC 14b, IC 15a and IC15b, ofwhich only two bits, gc, and Q1, are used.

Fig. 1. Two views of the completed (prototype) boards; note the right-angle assembly of the boards.


MIDI MULTIPLEXOR

After the supply voltage has beenswitched on, a reset signal provided byR22 -C14 ensures that the counters areset to position 0. All multiplexing ICsthen pass the signal applied to their pin10 on to the output. In other words, afterswitch -on, the MIDI signal from K1 is

available at K5, K6, K7 and Kg.

The output signals of the counters arealso applied to BCD -to -decimal decodersIC10-IC13. Only inputs A and B of thesedecoders are used; C and D are held low.

Depending on the logic level at the in-puts, one of the four outputs, Q0 -Q3, is

high. The LED associated with that out-put then lights. The four LEDs associatedwith each multiplexing IC are connectedto ground by a common resistor.

There is a push-button switch, Si, S2,

S3 or S4, at the clock input of each 4 -bitcounter. When this switch is operated, thecontent of the counter is increased by 1.The capacitor shunting the switch actsas a debouncing element. Every time a push-

button is pressed, the next MIDI input islinked to the output. The associated LEDindicates which input is connected to theoutput. Summarizing this operation:when the supply voltage is switched on,input K1 is linked to output K5; when Siis pressed once, K2 is linked to K5; whenSi is pressed again, K3 is connected to K5;

when Si is pressed for the third time, K4is linked to K5; when S 1 is pressed for thefourth time, the circuit returns to itsstarting state (Ki to K5). The operation of

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Fig. 2. Circuit diagram of the MIDI multiplexor.


18 ELECTROPHONICS

the other switches is identical.The control panel needs a supply volt-

age of +5 V. This is readily obtained froma 9-12 V mains adaptor which must beable to provide a current of not less than100 mA. Supply on is indicated by anLED, D21, in on/off switch S5.

ConstructionThe circuit is intended to be built onthe printed -circuit board shown inFig. 3. Actually, it shows two board,which must be cut apart before con-struction is started. The smaller partis for the five push-button switchesand associated 17 LEDs. The remain-der of the circuit is housed on thelarger part.

As usual, start by soldering thewire bridges, then the passive compo-nents and finally the active ones. The

soldering points for the MIDI connec-tors are neatly in a row at the rear ofthe board. It is advisable to fit solder-ing pins in these holes: the wires link-ing the points to the DIN buses aresoldered to them later.

If a right-angle single -row pin -header is used for K1, the two boardscan be interconnected firmly as shownin the photographs of Fig. 1.

A suggested front panel for the en-closure into which the boards are fit-ted is shown in Fig. 4. Regrettably,the front panel foil is not availableready made.

When the supply voltage isswitched on, the upper four LEDs in-dicate which interconnections havebeen made. The signal applied to K1 isavailable at all four outputs. The vari-ous instruments are then interlinkedby operating the relevant push-button

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Parts list

Resistors:R1, R3, R5, R7, R9 -R17 = 220 S2R2, R4, R6, R8 = 4.7 kf2R18, R19, R21 -R23 = 10 IcS2R20, R24 -R26 = 330 C2

Capacitors:C1 -C4, C7 -C13 = 100 nFC5 = 100 pF, 25 VC6 = 10 pF, 25 VC14 = 10 pF, 63 V

Semiconductors:D2 -D5 = 1N4148D1, D6 -D20 = LED, rectangularD21 = LED, round, 3 mm (see text)D22 = 1N4001

Fig. 3. Printed -circuit board for the midi multiplexor.


Please mention ELEKTOR ELECTRONICS when contacting advertisers 19

KITS AND COMPONENTS FOR ELEKTOR ELECTRONICS PROJECTS

-.111111.

SURROUND SOUND PROCESSORdescribed in this issue

kit, incl. case and PCB, noel main franelorater 10.G 299 00, PAP 20.00

Individual parts also available2pF2 MKT 5mm.,100pF polystyrene100nF ceramic.:.1pF MKT 5mm4700pF 25V radisl100pH choke150pH choke.MV5491ANE5532N

MN3101MN3008

Februar 1994

TL072CP 1.75

, 1 15 14E571N 12.50246 TLOA4CP 1.80

040 TDA1074A 15.00..0.06 TDA2040 15.00

.175 Phono socket, 00Id-plated 2.35. 085 65102 4.75

085 V23037 -A2 -A101 relay 9.75...2 25 SK57/37 5mm heatsink 29.50

1.00 Cerrito washer A08220 1.95,12.95 Case 0132104 54.0065 00 PAP 15.00

Infra -red light dimmer300pH 3A choke 5.50680C1500 4.00TIC206D 1.80SFH506-36 11.50SAA3049 16.75CNY65 4.65SLB0587 9.75MIDI multiplexerKit, incl. PCB and case 129.00

P&P 20.00

Januar 19941 -to -3 -phase converterKit, incl. case, PCB, GALand EPROM 699.00

P&P 50.00

Mini audio DACKit, incl case and PCB 349.00

P&P 25.00Polystyrene C's (1%) 2.45 each2pF2 MKT 50V 1.9547pH choke 0.85BAT85 0.85138001500 4 0074HCU04 1.25YM3623B 85.00PCM1710U 90.0074HC86 0.95NE5532N 0.90PCB terminal block 1.25

G2 3-FT12 4.75VTR3209 transformer 27.5016MHz crystal 4 1011.2896 MHz crystal 9.75

V23042 -A2005 -B101 relay 12.50

Case ESM ET 24/04 39.00P&P 20.00

P.O.S.T. diagnostic cardKit, incl. PCB and GALs 119.00

P&P 12.50BAT85 0.85HD11070 5.005 -way DIP switch 3.25

Self -loading EEPROM X88C64 SLIC

80031 21.50X88064 SLIC 45.00MAX232N 5.959 -way sub -D PCB mount 3.506 -way mini -DIN socket 2.8511.0592 MHz crystal 4.10SLIC design kit 95.00

Debugging 8031/51 pC systems74HCT541 2.75MAX232N 5.959 -way sub -D PCB mount 3.503 -way jumper 1.25

December 1994ispLSl Starter kitOriginal Lattice kit 199.00

P&P 15.00In -car audio amplifier (3)Many parts can be supplied. See ourmini -catalogue for prices and availability

November 1994Solid-state diskKit, incl PCB, EPROM, OK RAM ....215.00

P&P 15.00611024 RAM (each) 39.00

Simple capacitance meterKit, incl. DVM module and case....169.00

P&P 15.00LM358LP-2.5 3.75BAT82 0.85Polypropylene C's 2.45 eachTLC279CP 6 75TLC274CP 2.85DVM module 39.50

October 1994TV line monitorLM1881 13.2574HCT221 1.75HD11070 5.00PCB mount RCA socket 2.45Digitast presskey w. cap 3.50

In -car audio amplifier (11Many parts can be supplied. See ourmini -catalogue for prices and availability

Se tember 1994Medium -fidelity power amplifier0.2212 5W low -inductance 4.95Transistor set T1 -T7 19.50SK85/75 heatsink 29.75Ceramic washer TOP3 1 95LM1037N 14.75NE5532N 4.50T709G gold-plated socket 2 35V23042 -A2005 -B101 relay 12.50SK129/25.4 heatsink 5.3510,000pF 50V radial cap 27.50Other parts can be supplied, pleaseenquire.

Anemometer and flow meterMPX10DP 49.7514(52 multiturn cermet 2.755k0 multiturn cermet 2.7525052 multiturn cermet 2.75BAT85 0.854 -way PCB socket 1.55

Jul /Au ust 199480C451 controller boardSC80C451CCA68 39.5074HCT573 2.75MAX232N 5.95

4 752 454.10

68 pin PLCC socket2CTL2 push-button12MHz crystal

Discrete preamplifierMATO2 17.50MATO3FH 18.50OP77GP 4.15BC56OC 0.60BC550C 0.60

BC337 40 2.80

BC327-40 2.80

Robust AF power amplifierSemiconductor set 19.50100pF bipolar C 4.75Heatsink set, incl. washers 47.50

p&p 10.002200pF 40V radial .6.75

General-purpose IR vol controlAlps 20KAX2 motor -driven stereo pot,20k0 log 85.00SFH506-38 11.50SAA3049 16.75BC639/640 0 954MHz crystal 4.10BS170 1.55

IgME800535 extension boardKit incl. PCB and disk,excl. LCD 165.00

P&P 12.50 (Europe)P&P 20.00 (outside Europe)

SAA3049 16.75PC08584 = PCF8584 18.50PCF8583 9.75

Fuel consumption meterKMX106 9.85

VHF/UHF RECEIVEREE May 1993. Kit, excl. Tr1 345.00All parts also available separately.

800535 SBC KITEE Feb. 1994. Complete with assemblercourse and '535 datasheet 225.00

P&P 12.50

We have much more than can be listed here CATALOGUE AGAINST ONE IRC

C -I Electronics P.O. Box 22089 NL-8380-118 NuthHolland Fax: (+91) 45 241877

Faxed enquiries may be answered by mail. Please l...'ays far, your complete addressEnclose one IRC with all correspondence. Prices via in Dutch guilders (NLG), subjectto change without prior notice, and exclusive of P&P.Private customers in EEC countries add BTW (sales tax) at 17.5%, then P&P.P&P components NLG 12 50 (Outside Europe): NLG 8.50 (Europe). P&P kits: asstated in advert or catalogue Extensive ordering info supplied with catalogue.

VISA - MASTER - ACCESS - EUROCARD orders welcome

IN I

IN2

1N3

1N4

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CICI

1

MIDI MULTIPLEXOR

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1=1

CICI

4 POWER

0

930101-F

Fig. 4. Suggested front panel for the MIDI multiplexor.


Integrated circuits:ICI, IC3-1C5 = CNY17-2IC2 = 74HCT08IC6-1C9 = 74HC153IC10-IC13 = 4028IC14, IC15 = 4520IC16 = 7805

Miscellaneous:K1 -K8 = 5 -way DIN socket for board

mounting (180°)K10 = 26 -way, single -row pin header

(90°)S1 -S4 = Digitast switchS5 = Digitast switch with hold contact

and integral LED (D21)Enclosure 80x100x130 mm

(31/8x4x51/8 in)Plug to receive mains adaptor socketPCB Order No. 93010-1

1930101]


LOW COST LASER NIGHT SIGHT just £79111Cheaper version of our £245 Cyclops model, works ok in low lightlevels or in complete darkness with the butt in Laser. ref 95/79PC CONTROLLED 4 CHANNEL TIMERControl (on/off times etc) up to 4 Items (8A 240v each) with this kit.Complete with Software, relays, PCB etc. £25.99 Ref 95/26

LOW COST RADAR DETECTORBuilt and tested pocket radar detector, ideal for picking up speed trapsetc. Why pay £70 or more? ours is just £24.99 ref 95/25.COMPLETE PC 300 WATT UPS SYSTEMTop of the range UPS system providing protection for your computersystem and valuable software against mains power fluctuations andcuts.New and boxed, UK made Provides up to 5 mins running lime inthe event of complete power failure to allow you to run your systemdown correctly. SALE PRICE just £119.00.SHOP WOBBLERSISmall assemblies designed to take D size batteries and 'wobble' signs,cardboard models about In shop windows! £3.99 Ref SEP4P2.

RADIO PAGERSBrandnew, UK madepocket pagers clearance peceisjust£4.99 each100x40x15mm packed with bits! Ref SEP6.

BULL TENS UNITFully buitt and tested TENS (Transcutaneous Electrical Nerve Stimu-lation) unit, complete with electrodes and full instructions. TENS isused forte relief of pain etc in up to 70% of sufferers. Drug free painrelief, sale and easy to use, can be used in conjunction With analgesics

etc. £49 Ref TEN/1

STEREO MICROSCOPE155X195MM, up to 600mm high, so Items up to 10"will fit under tense.Rack arid pinion focusing, 6 interchangeable rotating object lenses.Interchangeable eye pieces, 4 -scaled eyepiece for accurate measur-ing etc. Powerful low voltage illumination system with green fitter andvariable 'density, 100mm black/White + ground glass stage plate,70mm swivel mirror, adjustabe eyepieces (both focus and width).Magnification range 4.6-100.8, field of view 39-2.4mm).Price is £299 for complete setup. Ref 95/300.3D 35MM CAMERA SYSTEMComplete Milo convert a standard 35mm camera into a 3D version!,enable youto take 3D colour slides withyour own camera! Kit containsa prismassembly forthefrontof youreAstinglense, a sample 30 slide,a 30 slide viewer and 2 different tense mounts 49mm and 52min,(other sizes available from photo shops at about £3 ea) all you need

is standard slide film. Price for the complete kit is £29.99 ref 95/30.COMPUTER RS232 TERMINALS. (LIBERTY)Excellent quality modem units,Ilike Wyse 50,$) 2xRS232, 20 functionkeys, 50 thro to 38,400 baud, menu driven port, screen, cursor, andkeyboard setup menus (18 mends). £29 REF NOV4.OMRON TEMPERATURE CONTROLLERS (E5C2).Brand new controllers, adjustable from -50 deg C to +1,200 deg Cusing graduated dial, 2% accuracy, thermocouple Input long fife relayoutput ,3A 240v orp contacts. Perfectfor exactly controlling a tempera -

tee, Normal trade £50+, ours £15. Ref E5C2.ELECTRIC MOTOR BONANZA, 110x6Omm.Brand new precision, cap start (or spin to start), virtually silent andfeatures a moving outer casethat acts as a flywheel. Because of theirunusual design** think that 2 of these In a tube with some homemadefan blades could form the basis fora wind tunnel etc. Clearance priceIs just £4.99 FORA PAIR I (note -these wit have to be wired in seriesfor 240v operation Ref NOV1.

MOTOR NO 2 BARGAIN 110x90mm.Similar to the above motorbut more suitable for mounting vertically (leturntable etc). Again you wit have to wire 2 in series for 240v use.Bargain price Is just £4.99 FOR A PAIR!! Ref NOV3.

OMRON ELECTRONIC INTERVAL TIMERS.Minature adjustable timers,4 pole do output 3A 240v,HY1230S, 12vDC adjustable from 0-30 secs. £9.99HY1210M, 12vDC adjustable from 0-10 mins. £9.99HY1260M, 12vDC adjustable from 0-60 mins. £9.99HY2460M, 24vAC adjustable. from 0-60 mins. £5.99HY241S, 24vAC adjustable from 0-1 secs. £5.99HY2460S, 24vAC adjustable from 0-60 sees, £5.99HY243H, 24vAC adjustable from 0-3 hours. £8.99HY2401S, 240v adjustable from 0-1 secs. £9.99HY2405S, 240v adjustable from 0-5 secs. £9.99HY24060m, 240v adjustable from 0-60 mins. £12.99PC PAL VGA TO TV CONVERTER Converts a colour IV intoa basic VGA screen. Complete with butt in psu, lead and skiers.£49.95. Ideal for laptops or a cheap upgrade.

EMERGENCY LIGHTING UNIT Complete unit with 2 doublebulb floodlights, built in charger end auto switch. Fully cased. 6v BAHlead acid regd. (secondhand) £4 ref MAG4P 11.

GUIDED MISSILE WIRE. 4,200 metre reel of ultra thin 4 coreinsulated cable, 28llis breaking strain, less than lmrn thick! Idealalarms, intercoms, fishing, dolls house's etc. £14.99 ref MAG15P5300v PANEL METER 70X60X50MM, AC, 90deeeeescale. Goodquality meter. £5.99 ref MAG 6P14. Ideal for monitoring mains etc.

ASTEC SWITCHED MODE PSU BM41012 Gives +5 @ 3.75A,+1201.5A, -12@,4A. 230/110, cased, BM41012. £5.99 ref AUG6P3.TORRODIAL TX 30-0-30 480vA, Perfect for Mosfet amplifiersetc. 120mm die 55mm thick £18.99 ref APR19,AUTO SUNCHARGER 155x300mm solar panel with diode and3 metre lead fittedwIth a cigar plug. 12v 2watt £9.99 ea ref AUG1 OP3.

FLOPPY DISCS DSDD Top gustily 525" discs, these have beenwritten to once and are unused. Pack of 20Is £4 ref AUG4P1.ECLATRON FLASH TUBE As used In police car flashing lightsetc, lull spec supplied, 60-100 flashes a de £9.99 ref APR10P5.24v AC 96WATT Cased power supply. New. £13.99 ref APR14.MILITARY SPEC GEIGER COUNTERS Unused and straightfrom Her majesty's forces, £50 ref NAG 50P3.STETHOSCOPE Fully functioning stethoscope, ideal for fisteningto hearts, pipes, motors etc. £6 ref MAR6P6,OUTDOOR SOLAR PATH LIGHT Captures sunlight duringthe day and automatically switches on a Wein lamp atdusk. Completewith sealed lead acid battery etc.£19.99 ref MAR20P1.

ALARM VERSION Of above unit comes with built in alarm and pir

NEW BULL ELECTRONICS STORE IN

WOLVERHAMPTON55A WORCESTER ST TEL 0902 22039

to deter intruders. Good value at Just £24.99 ref MAR25P4.CLOCKMAKER KIT Hours of eel making your own clock, com-plete instructions and everything you need. £7.99 ref MAR8P2.CARETAKER VOLUMETRIC Aarm, will cover the wbole of theground floor against forcred entry. Includes mains power supply andintegral batterybackup. Powerful intemalsounder, will take extemalbellif req'd. Retail £150+, ours? £49.99 ref MAR50P1.TELEPHONE CABLE White 6 core 100m reel complete with apack of 100 clips. Ideal 'phone exits etc. £7.99 ref MARBP3.MICRODRIVE STRIPPER Small cased tape drives ideal forstripping, lots of useful goodies including a smart case, and tots ofcomponents. £2 each ref JUN2P3.SOLAR POWER LAB SPECIAL You getTWO 6"x6" 6v 130mAsolar cells, 4 LED's, wire, buzzer, switch plus 1 relay or motor.Superbvalue kit just £5.99 REF: MAG6P8SOLID STATE RELAYS WO switch 25Arnains. Input 3.5-26v DC57x43x21nwn with terminal screws £3.99 REF MAG4P10300DPI A4 DTP MONITOR Brand new but shop soiled so hencebargain priceiTTLJECL inputs, 15" landscape, 1200x1664 pixel corn-plete with circuit dog to help you interface with your projects. JUST£14.99. REF JUN15P2.BUGGING TAPE RECORDER Smallvoice activated recorder,usesmicro cassette completewithheadphones. £28.99 ref MAR29P1.ULTRAMINI Ewa MIC6mnmsG.5mm made byAKG..5-12v electretcondenser. Cost £12 ea, Our? four for £9.99 REF MAG10P2.RGB/CGA/EGA/TTL COLOUR MONITORS 12" in goodcondition. Back anodised metal case. £79 each REF JUN79ANSWER PHONES Returns with 2 faults, we give you the bits for1 fault, you have to find the other yourself. BT Response 200's £18 eaREF MAG18P1. PSU £5 ref MAG5P12.SWITCHED MODE PSU ex equip, 60w +5v @5A, 45v0.5A,+12vQ2A,[email protected] 120/220v cased24548x55mmiECinputsockel£6.99 REF MAG7P1PLUG IN PSU 9V 200mA DC £2.99 each REF MAG3P9PLUG IN ACORN PSU 19v AC 14w, £2.99 REF MAG3P10POWER SUPPLY fully cased with mains and o/p leads 17v DC900mA output. Bargain price £5.99 ref MAG6P9ACORN ARCHIMEDES PSU +6v a 4.4A. on/off sw uncased,selectable mains input, 145x100x45mm £7 REF MAG7e2GEIGER COUNTER KIT Low cost professional twin tube, com-plete with PCB and components. Now only £19 REF AUG19.9v DC POWER SUPPLY Standard plug in type 150ma 9v DC withlead end DC power plug. price for two is £2.99 ref AUG3P4.

AA NICAD PACK encapsulated pack of 8 AA !cad batteries(tagged) ex equip, 55x32x32mm. £3 a pack REF MAG3P1113.8V 1.9A psu cased with Irma. Just £9.e9 REF MAGI OP3PPC W)DEM CARDS. Theseare high specpiugincaresmadeforthe Amstrad laptop computers. 2400 baud dial up unit complete withleads. Clearance price Is £5 REF: MAG5P1INFRA RED REMOTE CONTROLLERS Originally made forhi spec satellite equipment but perfect for all sorts of remote controlprojects. Our clearance price is Just £2 REF: MAG2TOWERS INTERNATIONAL TRANSISTOR GUIDE. Avery meld book for finding equivalenttransIstors, leadouts, specs etc.£20 REF: MAG20P1SINCLAIR C5 MOTORS We have a few left without gearboxes.Spec is 12v DC 3,300rprn £30.

200 WATT INVERTER Converts 10-15v DC into either 110v or240vAC. Fullycased 115x36x156rnm, comptete vethheavydutypowerlead, cigar plug, AC outlet socketAuto overload shutdown, auto shortcircuit shut down, auto input over voltage shutdown, auto input is rilevoltage shut down (with audible alarm), auto temp control, unit shutsdown if overheated and sounds audible alarm. Fused reversed polarityprotected. output frequency within 2%, voltage within 10%. A extremely

well but unit at an excellent price. Just £64.99 ref AUG65.UNIVERSAL SPEED CONTROLLER KIT Designed by us forthe C5 motor but ok for any 12v motor up to 30A Complete with PCBetc. A heat sink may be required. £17.00 REF: MAG17MAINSCABLE Precutbiack 2 core 2metrelengths Idealtor repairs,projects etc. 50 metres for £1.99 ref AUG2P7.COMPUTER COMMUNICATIONS PACK Kit contains 100mof 6 core cable, 100 cable clips, 2 fine drivers with RS232 interfacesand at connectors etc. Ideal tow cost method of communicating be-tween PC's over a long distance. Complete kit £8.99,

MINI CYCLOPS PIR 52x62x40mm runs on PP3 battery completewith shrill sounder. Cheap protection at only £5.99 ref MAR6P4.

ELECTRIC MOTOR KITOomprehensiveeducational kitinciudesail you need to Meld an electric motor. £9.99 ref MAR10P4.

VIDEO SENDER UNIT. Transmits both audio and video signalsfromeither aiii.deo camera, videorecorder, IV or Computer etcloanystandard TV set In a 100' range! (tune 'TV to a spare channe1)1 2v DCop. Price is £15 REF: MAG15 12v psu is £5 extra REF: MAGSP2*FM CORDLESS MICROPHONE Small hand held unit with a500' rangei 2 transmit power levels. Reps PP3 9v battery. Tuneable toany FM receiver. Price is £15 REF: MAG15P1LOW COST WALKIE TALKIES Pair of battery operated unitswits rangeof about 200. Idealfor garden useor asan educalionaltoyPrice Is £8 a pair REF: MAC 8P1 2 x PP3 req'd.

*SOME OF OUR PRODUCTS MAY RE UNLICENSABLE IN THE UK

BULL ELECTRICAL250 PORTLAND ROAD HOVE SUSSEX

BN36QTMAIL ORDER TERMS: CASH PO OR CHEQUEWITH ORDER PLUS £3.00 POST PLUS VAT.

PLEASE ALLOW 7 -10 DAYS FOR DELIVERYTELEPHONE ORDERS WELCOME

TEL: 0273 203500 ntAFAX: 0273 323077

*MINATURE RADIO TRANSCEIVERS A pair of wa1kie talkiesv4tharange otupto2 km inopencountry. Unesmeasure 22)(52/155mm.Including cases and earp'ces. 2xPP3 req'd. £30.00 pr.REF: MAG30COMPOSITE VIDEO KIT. Converts composite video into sepa-rate H sync, V sync, and video. 12v DC. £6.00 REF: MAGSP2.LQ3500 PRINTER ASSEMBLIES Made by Amstrad they areentire mechanical printer assemblies inducting printhead, stepper mo-tors etc etc In fact everything bar the case and electronics, a goodstripper! £5 REF: MAG5P3 or 2 for £8 REF: MAG8P3LED PACK of 100 standard red 5m leds £5 REF MAG5P4UNIVERSAL PC POWER SUPPLY complete with Weeds,switch, fart etc. Two types available 150w at £15 REF:MAG15P2(23x23x23mm) and 200w at £20 REF: MAG20P3 (23)e23x23mm)

*FM TRANSMITTER housed to a standard working 13A adapter!!the bug runs directly off the mains so lasts forever! why pay £700? orprice is £26 REF: MAG26 Transmits to any FM radio.*FM BUG KIT Nevi designwith PCB embedded coil for extra stability.Works to any FM radio. 9v battery req'd. £5 REF: MAG5P5*FM BUG BUILT AND TESTED superior designto id Suppledto detective agencies. 9v battery req'd. £14 REF: MAG14TALKING COINBOX STRIPPER originally made to retail at £79each, these units are designed to convert an ordinary phone into apeyphone. The units have the locks missing and sometimes brokenhinges, However they can be adapted for their original use or used forsomething else?? Price is just £3 REF: MAG3P1

TOP QUALITY SPEAKERS MadeforHi Fl televisionsthese are10 watt 4R Jap made 4" round with large shielded magnets. Goodquality. £2 each REF: MAG2P4 or 4 for £6 REF: MAGBP2TWEETERS 2" diameter good quality tweeter 140R (ok with theabove speaker) 2 for £2 REF: MAG2P5 or 4 for £3 REF: MAG3P4AT KEYBOARDS Made by Apricot these quality keyboards needjust a small mod to run on any AT, they work perfectly but you wit haveto put up with 1 or 2 foreign keycaps! Price £6 REF: MAG6P3HEADPHONES ExVirgin Atlantic. 8 pairsfor£2 REF: MAG2P8SNOOPERS EAR? original made to clip over the earpiece oftelephone to amplify the sound -it also works quite well on the cablerunning along the watt Price is £5 REF: MAGSP7

DOS PACKS Microsoft version 3.3 or higher complete with allmanuals or price Just £5 REF: MAG5P0 Worth it just for the verycomprehensive manual! 5.25" only.DOS PACK Microsoft version 5 Original software but no manualshence only £5.99. 3,5" only.

PIR DETECTOR Made by famous UK alarm manufacturer theseare hi spec, long range internal units. 12v operation, Slight marks oncase and unboxed (although brand new) £8 REF: MAG8P5WINDUP SOLAR POWERED RADIO AWFLII radio completewith hand charger and solar panel! £17.99 REF: 14P2OORA

MOBILE CAR PHONE £5.99 Wet altms0 completeincar phoneexcluding the box of electronics normally hidden under seat. Can bemade to Illuminate with 12v also has built in light sensor so display onlyilluminates when dark. Totally convincing; REF: MAGSP6

ALARM BEACONS Zenon strobe made to mount on an externalbellboxbutcouldbeuseefforcaravans etc. l2voperation. Justconnectup and it flashes regularty) £5 REF: MAG5P11FIRE ALARM CONTROL PANEL High quality metal casedalarm panel 350x165x8Omm.Witt key. Comes with electronics but noinformation. sate price 7.99 REF: MAG8P66"X12" AMORPHOUS SOLAR PANEL 12v 155x310mm130mA. Bargain price just £5.99 ea REF MAG6P12.

FIBRE OPTIC CABLE BUMPER PACK 10 metresfor £4.99ref MAG5P13 Ideal for everimenters! 30 m for £12.99 ref MAG13P1HEATSINKS (fiireed)10220, designed to mount vertically on a pcb50x40x25mm you can have a pack of 4 for £1 ref JUMP/ I.INFRARED LASER NIGHT SCOPESImage intensifier complete with hand grip attachment with but Inadjustable laser lamp for zero light conditions. Supplied with Pentax42mnicameramountand normal eyepiece. 1.6kg uses 1xP P3,3xAA's

(at supptied)E245+Vat

NEW HIGH POWER LASERS15mW, Het un neon,3 switchablewave lengths .63um,1.15urn,3.39um(2 althorn are infrared)500:1 polarizer bulttin so good for holograpny.Supplied complete with mains power supply.790x65mm. Use withEXTREME CAUTION AND QUALIFIED GUIDANCE £3494 -Vat

WE BUY SURPLUS STOCK FOR CASH1995 100 PAGE CATALOGUE NOWAVAILABLE, 45P STAMP OR FREE

WITH ORDER3FT X 1FT 10WATT SOLAR PANELS

14.5v/700mA£44.95

(PLUS moo SPECIAL PACKAGING CHARGE)

TOP QUALITY AMORPHOUS SILICON CELLS HAVE AL MOST ATIMELESS LIFESPAN WITH AN INFINITE NUMBER OF POSSI-BLE APPLICATIONS. SOME OF WHICH MAY BE CAR BATTERYCHARGING, FOR USE ON BOATS OR CARAVANS, OR ANY-WHERE A PORTABLE 12V SUPPLY IS REQUIRED.

PORTABLE RADIATION DETECTOR

WITH NEW COMPUTER INTERFACE.

£59.00A Hand held personal Gamma and X Ray detector.This unit contains two Geiger Tubes, has a4 digit LCDdisplay with a Piezo speaker, giving an audio visualindication. The unit detects high energy electromag-netic quanta with an energy from 30K eV to over 1.2MeV and a measuring range of 5-9999 URM or 10-99990

MM. Supplied complete with hand book.Ref . NOV 18.



POWER AMPLIFIER MODULES -TURNTABLES -DI MERS-LOUDSPEAKERS-19 INCH STE 0 CK M I

OMP MOS-FET POWER AMPLIFIERSHIGH POWER, TWO CHANNEL 19 INCH RACK

THOUSANDS PURCHASEDBY PROFESSIONAL USERS

'A*

THE RENOWNED MXF SERIES OF POWER AMPLIFIERSFOUR MODELS:- MXF200 (100W + 100W) MXF400 (200W + 200W)

MXF600 (300W + 300W) MXF900 (450W + 450W)ALL POWER RATINGS R M S INTO 4 OHMS, BOTH CHANNELS DRIVEN

FEATURES: *Independent power supplies with two toroidal transformers * Twin L E D Vu meters *Level controls * Illuminated on/off switch * XLR connectors * Standard 775mV inputs * Open and short circuitproof * Latest Mos-Fets for stress free power delivery into virtually any load * High slew rate * Very lowdistortion * Aluminium cases * MXF600 & MXF900 fan cooled with D C loudspeaker and thermal protection

USED THE WORLD OVER IN CLUBS, PUBS, CINEMAS, DISCOS ETC

SIZES:- MXF200 W19"x143' x (2U)sD1 1"MXF400 W1 9"x115' a (3U)xD1 2"MXF600 W1 9xH5r. (3U)xD1 3"MXF900 W1 9"xli5r. (3U)xD14r,"

PRICES:- MXF200 £175 00 MXF400 £233.85MXF600 £329 00 MXF900 £449.15SPECIALIST CARRIER DEL F12 50 EACH

I :21:(01(1-1 I 1; I 4Nc157/.VE X it I 43:101--1---III'll:,

Advanced 3 -Way Stereo Active Cross -Over, housed in a 19 x 1U case Each channel has three level controlsbass, mid & top. The removable front fascia allows access to the programmable DIL switches to adjust thecross -over frequency, Bass -Mid 250/500/800Hz Mid Top 1 8/3/5KHz, all at 24dB per octave Bass invert switcheson each bass channel. Nominal 775mV input/output Fully compatible with OMP rack amplifier and modules

Price £117.44 + £5.00 P&PI = * ECHO & SOUND EFFECTS*

STEREO DISCO MIXER with 2 x 7 bandL & R graphic equalisers with bar graphLED Vu meters. MANY OUTSTANDINGFEATURES:- including Echo with repeat &speed control, DJ Mic with talk -overswitch, 6 Channels with individual fadersplus cross fade, Cue Headphone Monitor. 8Sound Effects. Useful combination of thefollowing inputs:- 3 turntables (mag), 3mins, 5 Line for CD, Tape, Video etc.

Price £144.99 + £5.00 P&P SIZE 482 x 240 0120mm

-SERVICE * LARGE (AC BOp STAMPED FOR CATALOGUE *

I V

'937,I9,',141-11J4111;161','I4:11.U1:1111J1:11,',I$1.111114- SUPPLIED READY BUILT AND TESTED.

These modules now enjoy a world-wide reputation for quality, reliability and performance al a realistic price. Fourmodels are available to suit the needs of the professional and hobby market i.e. Industry, Leisure, Instrumental and Hi-Fietc. When comparing prices, NOTE that all models include toroidal power supply, integral heat sink, glass fibre P.C.B. anddrive circuits to power a compatible Vu meter. All models are open and shod circuit proof.

THOUSANDS OF MODULES PURCHASED BY PROFESSIONAL USERSOMP/MF 100 Mos-Fet Output power 110 wattsR.M.S. into 4 ohms, frequency response 1Hz - 100KHz-3dB, Damping Factor >300, Slew Rate 45V/uS,T.H.D. typical 0.002%, Input Sensitivity 500mV, S.N.R.-110 dB. Size 300 x 123 x 60mm.PRICE C40.85 + £3.50 P&P

ifs

N.

OMP/MF 200 Mos-Fet Output power 200 wattsR.M.S. into 4 ohms, frequency response 1Hz - 100KHz-3dB, Damping Factor > 300, Slew Rate 50V/uS,T.H.D. typical 0.001%, Input Sensitivity 500mV, S.N.R.-110 dB. Size 300 x 155 x 100mm.PRICE £64.35 - £4.00 P&P

OMP/MF 300 Mos-Fet Output power 300 wattsR.M.S. into 4 ohms, frequency response 1Hz - 100KHz-3dB, Damping Factor >300, Slew Rate 60V/uS,T.H.D. typical 0.001%, Input Sensitivity 500mV, S.N.R.-110 dB. Size 330 x 175 x 100mm.PRICE £81.75 + £5.00 P&P

OMP/MF 450 Mos-Fet Output power 450 wattsR.M.S. into 4 ohms, frequency response 1Hz - 100KHz-3dB, Damping Factor > 300, Slew Rate 75V/uS,

yr T.H.D. typical 0.001°A, Input Sensitivity 500mV, S.N.R.-110 dB, Fan Cooled, D.C. Loudspeaker Protection, 2Second Anti -Thump Delay. Size 385 x 210 x 105mm.PRICE £132.85 - £5.00 P&P

OMP/MF 1000 Mos-Fet Output power 1000 wattsR.M.S. into 2 ohms, 725 watts R.M.S. into 4 ohms,frequency response 1Hz - 100KHz -3dB, DampingFactor > 300, Slew Rate 75V/uS, T.H.D. typical0.002%, Input Sensitivity 500mV, S.N.R. -110 dB, FanCooled, D.C. Loudspeaker Protection, 2 SecondAnti -Thump Delay. Size 422 x 300 x 125mm.PRICE £259.00 - £12.00 P&P

NOTE: MOS-FET MODULES ARE AVAILABLE IN TWO VERSIONS:STANDARD - INPUT SENS 500mV, BAND WIDTH 1 OOKHz.PEC (PROFESSIONAL EQUIPMENT COMPATIBLE) - INPUT SENS775mV, BAND WIDTH 50KHz ORDER STANDARD OR PEC.

L Join the Piezo revolution! The low dynamic mass (no voice coil) of a Piezo tweeter produces an improvedtransient response with a lower distortion level than ordinary dynamic tweeters. As a crossover is not requiredthese units can be added to existing speaker systems of up to 100 watts (more if two are put in series. FREEEXPLANATORY LEAFLETS ARE SUPPLIED WITH EACH TWEETER.

TYPE 'A' (KSN1036A) 3" round with protective wire mesh. Ideal forbookshelf and medium sized Hi-Fi apeakers. Price 04.90 + 50p P&P.TYPE 'B' (KSN1005A) 3Y," super horn for general purpose speakers,disco and P.A. systems etc. Price £5.99 - 50p P&P.TYPE 'C' (KSN1016A) 2"x5" wide dispersion horn for quality Hi-Fi sys-tems and quality discos etc. Price 06.99 - 50p P&P.TYPE 'D' (KSN1025A) 2"x6" wide dispersion horn. Upper frequencyresponse retained extending down to mid -range (2KHz). Suitable for highquality Hi-Fi systems and quality discos. Price 09.99 + 50p P&P.TYPE È' (KSN1038A) Viii" horn tweeter with attractive silver finish trim.Suitable for Hi-Fi monitor systems etc. Price 05.99 l 50p P&P.LEVEL CONTROL Combines, on a recessed mounting plate, level controland cabinet input jack socket. 85x85mm. Price £4.10 - 50p P&P.

TYPE

TYPE 'C

TYPED

0 0

A new range of quality loudspeakers, designed to take advantage of the latestspeaker technology and enclosure designs. Both models utilize studio quality12" cast aluminium loudspeakers with factory fated grilles, wide dispersionconstant directivity horns, extruded aluminium corner protection and steelball comers, complimented with heavy duty black covering. The enclosuresare fated as standard with top hats for optional loudspeaker stands.

POWER RATINGS QUOTED IN WATTS RMS FOR EACH CABINETFREQUENCY RESPONSE FULL RANGE 45Hz - 20KHz

fbi FC 12-100WATTS (100dB) PRICE 0159.00 PER PAIRitrl FC 12-200WATTS (100dB) PRICE C175.00 PER PAIR

SPECIALIST CARRIER DEL. £12.50 PER PAIR

OPTIONAL STANDS PRICE PER PAIR C49.00Delivery £6.00 per pair

IN -CAR STEREO BOOSTER AMPS

PRICES 150W £49 99 250W C99 99400W C109 95 P&P C2 00 EACH

THREE SUPERB HIGH POWERCAR STEREO BOOSTER AMPLIFIERS150 WATTS (75 -r 75) Stereo, 150WBridged Mono250 WATTS (125 I 125) Stereo, 250WBridged Mono400 WATTS (200 + 200) Stereo, 400WBridged MonoALL POWERS INTO 4 OHMSFeatures:* Stereo, bridgable mono * Choice ofhigh & low level inputs * L & R levelcontrols * Remote on -off * Speaker &thermal protection.

LOUDSPEAKERS LARGE SELECTION OF SPECIALIST LOUDSPEAKERSAVAILABLE, INCLUDING CABINET FITTINGS, SPEAKERGRILLES, CROSS-OVERS AND HIGH POWER, HIGHFREQUENCY BULLETS AND HORNS, LARGE (A4) S.A.E.(60p STAMPED) FOR COMPLETE LIST

McKenzie and Fane Loudspeakers are also available.

ALL EMINENCE UNITS 8 OHMS IMPEDANCE8" 100 WATT R.M.S. ME8-100 GEN. PURPOSE, LEAD GUITAR, EXCELLENT MID, DISCO.RES. FRED. 72Hz, FRED. RESP. TO 4KHz, SENS 97dB. PRICE 032.71 4 C2.00 P&P10" 100 WATT R.M.S. ME10-100 GUITAR, VOCAL, KEYBOARD, DISCO, EXCELLENT MID.RES. FREQ. 71Hz, FREO. RESP. TO 7KHz, SENS97dB. PRICE C33.74 -4 C2.50 P&P10" 200 WATT R.M.S. ME10-200 GUITAR, KEYB'D, DISCO, VOCAL, EXCELLENT HIGH POWER MID.RES. FRED. 65Hz, FRED. RESP. TO 3.5KHz, SENS 99dB. PRICE 043.47 I C2.50 P&P12" 100 WATT R.M.S. ME12-100LE GEN. PURPOSE, LEAD GUITAR, DISCO, STAGE MONITOR.RES.FREQ. 49Hz, FREO. RESP. TO 6KHz, SENS 100dB. PRICE 035.64 + C3.50 P&P12" 100 WATT R.M.S. ME12-100LT (TWIN CONE) WIDE RESPONSE, P.A., VOCAL, STAGEMONITOR. RES. FREO 42Hz, FRED. RESP. TO 10KHz, SENS 98dB. PRICE C36.67 + C3.50 P&P12" 200 WATT R.M.S. ME12-200 GEN. PURPOSE, GUITAR, DISCO, VOCAL, EXCELLENT MID.RES. FRED. 58Hz, FRED. RESP. TO 6KHz, SENS 98dB. PRICE 046.71 C3.50 P&P12" 300 WATT R.M.S ME12-300GP HIGH POWER BASS, LEAD GUITAR, KEYBOARD, DISCO ETC.RES. FREQ. 47Hz, FRED. RESP. TO 5KHz, SENS 103dB. PRICE C70.19 - C3.50 P&P15" 200 WATT R.M.S. ME15-200 GEN. PURPOSE BASS, INCLUDING BASS GUITAR.RES. FRED. 46Hz, FRED. RESP. TO 5KHz, SENS 99dB. PRICE 050.72 C4.00 P&P15" 300 WATT R.M.S. ME15-300 HIGH POWER BASS, INCLUDING BASS GUITAR.RES. FRED. 39Hz, FREQ. RESP. TO 3KHz, SENS 103dB. PRICE 073.34 - £4.00 P&P

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Pi

AUTOMATIC LIGHTING TIMER

"

" I

' "- -

-

Design by E. Quinet

CIRCUITS such as this one are oftenused in hotels and restaurants.

They serve only one purpose: saving onthe electricity bill by cutting off thelight in hallways, toilets and staircaseswhen there is nobody around. In mostcases, the switch takes the form of apush-button, and is fitted with a weakneon light to help you find in the dark.After pressing the switch, the lamp isswitched on for a certain period,which, hopefully, is long enough tofind your key and open the door ofyour hotel room. In most cases, thatwill work just fine. A visit to the toilet,however, can become an embarassingexperience if the relevant room is fittedwith such a timer.

Still, the idea behind a lightingtimer is not bad. After all, it also hap-pens that lights in and around thehome (hallway, staircase, cellar, recep-

tion hall, garage) are left on longerthan strictly necessary. Such negli-gence causes money and energy to goto waste, and there is a clear point infavour of installing a lighting timer asdescribed here at several places in thehome. The negative aspects hinted atabove are easily overcome by using aslightly larger 'on' time than themiserly one or two minutes one gets inhotels and the like. Moreover, if theswitch is extended with an early warn-ing signal, frustration and awkwardsituations will seldom occur.

A flipflop and a timerThe block diagram in Fig. 1 shows theessential ingredients of the lightingtimer: a push-button, a flipflop(bistable), a timer and a relay. Thepush-button is the light switch. When

it is pressed, the flipflop is set, and therelay is energized. At the same time,the complementary flipflop outputclears the reset input of the timer,causing it to start its countdown cycle.

Just before the set timer periodelapses, an oscillator is started whichsupplies an acoustic warning signal.When the full time has elapsed, theflipflop is reset via the last timer out-put, so that its outputs toggle to theiroriginal state. The relay is de -ener-gized, the lighting is switched off, andremains off until the push-button ispressed again.

Circuit descriptionFigure 2 shows how the block diagramhas been translated into a practicalcircuit. A few things have been addedto make the circuit even more versatileand easier to use. One of these extrasis the possibility to reset the flipflopmanually. Also, the acoustic warninghas been extended, and an option isadded to enable automatic or normaluse.

The result of the design work isshown in Fig. 2. The mains voltage ar-rives in the circuit via the terminals ofK1, and is output again via K2, towhich the lamp is connected. The lampvoltage is switched by the contact ofrelay Ref, which is controlled by driverT2 and an S/R (set/reset) flipflop con-sisting of IC2, and IC2d. This flipflop isset by pressing SI, and reset by eitherthe timer or S2. Network C2 -D12 -Rioserves to reset the flipflop at power -on.Diodes D8 and D9 form a kind of by-pass around the flipflop, allowing theuser to press Si and so reset the timerwhile the light is on. This may be doneto start another òn' period, giving youextra time.

The timer is formed by the well-known 4060 oscillator/ripple counter(IC 1). The oscillator works with exter-nal parts P1, R1, R2 and C1. The preset,P1, allows the oscillator frequency tobe adjusted between about 7 Hz and45 Hz, which results in a `lights on' pe-riod of between 2 and 10 minutes.

The oscillator/counter is disabledby keeping its reset input logic high.When S1 is pressed, the oscillator isstarted, and the binary counter startsat state '0'. When a counter state withQ3, Q6 -Q9 and Q11 high is reachedjust before the counting operation isended, an AND gate consisting ofdiodes D1 -D6 ensures that oscillatorIC2a-IC2b is started via D7 and T1. Theoscillator frequency is adjustablearound 1 kHz with the aid of preset P2.The acoustic warning signal is made


AUTOMATIC LIGHTING TIMER

ductor, etc.). Surprisingly, the fre-quency at the counter output marked`Q3' is the clock frequency divided by16, and not, as one would expect, 8(23). It is true, however, that the 'high'and low' periods of the Q3 outputequal eight clock periods. That is apoint to remember if a time interval isto be created with the aid of a diode -AND gate, as in the present case.

The output of the AND gate isformed by the anodes of the six diodes.Transistor T1 starts to conduct if Q11,Q9, Q8, Q7, Q6 and Q3 are all logichigh at the same time. That happensafter the following number of clock cy-cles:

Fig. 1. The automatic lighting timer consistsof only two functional blocks: an electronicswitch and a timer. An acoustic signal is pro-duced just before the 'on' time is over.

audible via transistor T3 and loud-speaker LS1.

At the above mentioned counterstate, four short beeps are produced inthe rhythm of counter output Q3.These beeps indicate that the'lights on' period is nearly over. Theydo, however, allow plenty of time topress the button again. If the button isnot pressed, the remainder of thecounter cycle is completed, and fourbeeps are produced again. After thelast beep, Q12 goes high, causing theflipflop to be reset, and the relay to bede -energized.

Since it is desirable in some cases tobe able to bypass the timer, switch S3has been added to the circuit. In posi-tion 'A', the relay driver transistor, T2,is driven all the time via R16.Consequently, the light is on all thetime, irrespective of the states of theflipflop and the counter. In position 'C',the base of T2 is tied to ground, so thatthe light is always out. If you do notneed the bypass function, simply omitswitch S3.

The power supply has no surprises.It consists of a transformer, Tr1, a rec-tifier, B1, a smoothing capacitor, C5, athree -pin voltage regulator, IC3, and apair of decoupling capacitors, C3 -C4.

Diode AND gateThe operation of the diode AND gatewhich provides the early warning func-tion of the circuit deserves a separatediscussion. To begin with, however, letus have a look at the designations ofthe outputs of counter IC1, since thesehave given rise to a lot of confusion inthe past.

This confusion is caused mainly bynomenclature differences betweenmanufacturers of the 4060 (SGS,Motorola, Philips, National Semicon-

2,048+512+256+128+64+8 = 3,016.

Since the counter has a total of 4,096states, the early warning sounds atabout three-quarters of the availabletime. The absence of Q5 and Q6 in theabove 'AND' series causes the fourbeeps produced by the loudspeaker,while the absence of Q10 on the 4060provides the division between the firstand the second state of four beeps. Theend of the light on' period is reachedwhen counter output Q12 goes high.That happens after exactly 4,096 clockcycles.

ConstructionThe artwork of the printed circuitboard used to build the lighting timer

is shown in Fig. 3. This PCB is avail-able ready-made through the ReadersServices. The board accommodates allcomponents, except the switches andthe loudspeaker.

Since the circuit is connected to themains, special attention should begiven to safety. Terminal blocks K1 andK2 should be mains -rated types. Themains and lamp wires connected tothese blocks should be fitted with ap-proved grommets and strain reliefs.The enclosure used may only be plas-tic type with the appropriate insulationspecifications as regards mains -pow-ered equipment. The loudspeaker andthe control elements, Si, S2 and (op-tionally) S3, may be fitted on the coverplate. The connections of these exter-nal parts are clearly marked on theprinted circuit board overlay. Sinceonly small currents are carried bythese wires, ordinary light -duty insu-lated wire may be used.

AdjustmentsThe circuit has two adjustment pointsin the form of presets on the board.The most important of the two is P1,which determines the oscillator clockfrequency, and thus the length of the'light on' period. This preset is best ad-justed empirically until the desired 'on'time is reached. The relevant compo-nent values shown in the circuit dia-gram and the parts list result in aperiod which is adjustable between 2

D1...D13 = 1N1448

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940098-11

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K2

Fig. 2. Circuit diagram of the automatic lighting timer.


24 GENERAL INTEREST

COMPONENTS LIST

Resistors:R1;R6;R9 = 1001(51R2;R3;R 10;R 12 = 1MS2R4;R11;R14;R16 = 10162R5 = 221d1R7;R8 = 41(07R13 = 82kS2R15 = 2252P1 = 500162 preset HP2 = 251d2 preset H

Capacitors:C1;C2;C3 = 100nFC4 = 100pF 16V radialC5 = 220pF 25VC6 = 1nF

Semiconductors:D1-1)13 = 1N4148B1 = B80C1500*T1;T2 = BC547T3 = BC557IC1 = 40601C2 = 4001IC3 = 7805

Miscellaneous:K1;K2 = 2 -way PCB mount terminalblock, raster 7.5mm.S1;S2 = push -to -make button.S3 = 1 -pole 3 -position switch.Tr1 = mains transformer, 9V, 1.5VA,short-circuit proof (e.g., Block VR1109or Monacor VTR1109)*.Ls1 = loudspeaker, 852, 0.2W.Re1 = V23057 -A1 -A101 (coil voltage:6V) (Siemens).Printed circuit board, order code940098 (see page 78).

C -I Electronics, P.O. Box 22089, NL-6360 AB, Nuth, Holland. Fax: (+31) 45241877.

and 10 minutes. If you find 10 minutestoo short, C1, R1 and/or P1 may bemade a little larger. If you want a pe-riod of less than 2 minutes, give thesecomponents a smaller value.

The frequency of the acoustic warn-ing signal is adjusted with the aid ofpreset P2. Temporarily interconnectthe collector and emitter terminals ofT1, so that the oscillator is perma-nently on. Then adjust P2 until the de-sired tone frequency is obtained.Finally, a tip. If a certain applicationrequires more 'on' and 'off buttons atdifferent locations, the appropriatenumber of switches may be connectedin parallel with S1 and S2. (940098)

10 - Ref

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Fig. 3. Track layout and component mounting plan (overlay) of the PCB designed for thelighting timer (PCB available ready-made through the Readers Services).

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Windows' wave (.way) file compatibility. Multi -media users can listen to their waveforms or capture soundsamples for Fourier analysis or filtering. Binary output option makes ROM programming easy.PWL non-linear enhancements saves calculating polynomial coefficients for those awkward functions.

Make sure you know what you are missing by asking us for a copy of the demonstration program and booklet.Subscribers to the SpiceAge maintenance service will be receiving their new version along with a copy of the newmanual.

Please contact Those Engineers Ltd, 31 Birkbeck Road,LONDON NW7 4BP.Tel 0181-906 0155, FAX 0181-906 0969. I]mgonwo le

4.. 4ix', Ns


26

SURROUND SOUND PROCESSOR

Based on a design by D. Laues

The processor described in this article expands the sound ofan existing stereo TV receiver or audio installation with acentre channel and a surround channel. It does not usespecial Dolby ICs. Additional output amplifiers are notneeded, because they are provided in the processor.

reating surround sound in a domesticroom can be approached in two ways:

by a processor that generates the four sig-nals required: left-hand, right-hand, cen-tre and surround, or by one that adds thetwo missing channels, that is, centre andsurround, to the existing stereo sound. Thefirst is the most elegant, but also themost complicated and most expensive.Moreover, it requires an additional lineto return the left-hand and right-hand sig-nals to the input of the TV/audio equip-ment. The second way is much morestraightforward and has proved in prac-tice to give an excellent spatial effect.Moreover, it can be accomplished in acompact and fairly inexpensive unit. Thedesign in this article is of the secondkind.

The basic setup in a domestic room isshown in Fig. 1. The left-hand and right-hand channels are reproduced as be-fore, that is, via the loudspeakers in theTV receiver, as shown, or bythose of the audio installationto which the TV receiver is con-nected. The extra items are theprocessor and three loud-speakers. The inputs of theprocessor are linked, possibly viathe SCART connector, with the lineout terminal of the TV receiver,or audio amplifier, while theextra loudspeakers are connectedto the outputs of the processor.The processor contains two in-tegral amplifiers each of whichprovides 20 W output into 4 S2:quite sufficient for the centreand surround loudspeakers.

As briefly discussed in lastmonth's article on Dolby sur-round sound, the additionalloudspeakers need be no morethan compact (bookcase type) hi-fi types that are not too expensive.If possible, however, choose typeswhose efficiency is about thesame as that of the main loud-speakers: this affords rathermore freedom when the systemis set up as a whole.

Basic design

Ablock diagram of the basic design is givenin Fig. 2. The design of the processor issimilar to that of the active decoder dis-cussed in last month's article on Dolbysurround sound. There are some differ-ences between the two, since the presentprocessor not only functions as a de-coder, but also provides the signals forthe centre and surround channels andcontains two output amplifiers.

As explained last month, the two ad-ditional channels are processed (whencethe name of the unit) from the sum anddifference of the two stereo channels.The centre channel is the simpler to pro-duce, because it suffices to add the left-hand and right-hand channels togetherand apply the sum to a suitable outputamplifier via a voltage -controlled ampli-fier (VCA).

To produce the surround signal, theright-hand signal is deducted from the left -

Fig. 1. Basic setup of a surround sound systemin a living room.

hand signal (or vice versa) and the resultingsignal is applied to a delay network via alow-pass filter. The delay can be presetbetween 10 ms and 30 ms. The signal isthen applied to an expander via a band-pass filter. The expander is essential be-cause the surround signal is compressedduring recording. The output of the ex-pander is applied to a second outputamplifier via a VCA.

The dynamic compensating network,in conjunction with the VCAs, reflectsthe difference between an active and a pas-sive (matrix) design. In this network, thecorrelation between the two stereo chan-nels is analysed continuously. The re-sults of the analysis are converted intocontrol signals for the VCAs which con-stantly adjust the levels of the centre andsurround signals. This arrangement en-sures a much larger channel separationthan possible with a passive design.

Centre channelFrom the inputs of the left-handand right-hand channels, K1and K2 in Fig. 5, the signalsare taken via buffer amplifiersIC la and IC lb to R51 and R52,and then summed in preset P6.From there, the signal is ap-plied to pin 5 of IC9. This ICcontains four electronic po-tentiometer circuits (of whichonly two are used) which func-tion as VCAs; their amplificationis governed by a control voltageat pins 9 and 10. The output ofone of the circuits is availableat pin 7, from where it is ap-plied to output amplifier IC10.This circuit provides an out-put of up to 20 W into 4 CI.

The output of IC io is appliedto the centre channel loudspeakervia relay contact Re lb. The relayis controlled by a simple delaycircuit, Ti, and obviates anyclicks and plops in the speakercaused by the switching on andoff of the processor.


SURROUND SOUND PROCESSOR

left-handtrack V

(R51/R52/P6)

right-handtrack

EO

dynamiccompensation

(IC7/1C8)

V(IC2b)

--0 LP(IC2a)

At(IC4)

BP(IC5b/C43) -0 expander

(106)

1

(1C9) 1

VCA

(IC9)

VCA

(IC10)

(IC11)

centre

surroundI #

950012 - 12

Fig. 2. Block diagram of the surround sound processor.

Surround channel

The signals at the outputs of ICia andIC lb are also applied to the inverting andnon -inverting inputs of IC2b respectively,so that the output of the op amp is the dif-ference of the two stereo signals (L -R).The difference signal is applied to a 4th -order low-pass filter based on IC2a, whichlimits its upper bandwidth to 7 kHz. Thisanti-aliasing filtering serves to obviatethe formation of spurious mixing productsof the signal and the clock of the follow-ing delay line, which is based on IC4. ThisIC is a 2048 -stage bucket brigade device.The rate at which the internal electronicswitches are operated is determined byIC3. This CMOS-IC is designed especiallyto generate a low -impedance, double -phase clock. The specified values of its fre-quency -determining components, R15,R16, C9 and Pi allow a delay between 10 ms

and 30 ms to be set with P1.The outputs of IC4 are applied via

buffer IC5a to a low-pass filter based onIC5b (identical to that based on IC2a) whichfilters out any residue of the clock signal.The cut-off frequency is 7 kHz. The sig-nal is subsequently fed to companderIC6, whose input network contains ahigh-pass filter, R55 -C43, the specifiedvalues of which give a lower cut-off fre-quency of about 50 Hz. The overall effectof the low-pass and high-pass filters is,of course, that of a band-pass filter as shownin Fig. 2.

The compander IC contains two circuitseach consisting of a rectifier, a variablegain cell and an op amp. In the presentprocessor only one of these circuit is usedand that as an expander. The values ofexternal components R27 -R32 and C23 -C29allow for an expansion factor of 1:1.3.

The surround signal is then applied to

the second electronic potentiometer cir-cuit in IC9, whose output is available atpin 17. From there, the signal is fed to out-put amplifier IC11, whose amplificationis identical to that of IC 10. The output ofIC11 is applied to the surround loud-speaker(s) via a second contact on Re .

Dynamic compensationThe outputs of buffers ICia and IC lb arealso applied to twin comparators IC7band IC7, via C31 and C32. The output ofeach of these comparators is a rectangularvoltage the frequency of which is a mea-sure of the variation in the relevant inputsignal. Both outputs are applied to XORgate IC8c. (Remember that an XOR gate hasan output only when its inputs are dis-similar). Integration of the output pulsesof the gate by R37 -C36 results in a directvoltage whose amplitude is a measure of

Fig. 3. Completed prototype board.


Fig. 4. Completed prototype processor.

R3*

11.1K

12p2

4V7

* see text

2n2

2n2

C32

C31

C6

C4

=IM

Mni

1N4148

8V E

t_v1;41-1

C12

O

79

100n

100n

MN

3008

C13

C14

!loon

4p73v

4775V

2x 12V

80VA

K3

IC1 =

NE

5532IC

2 = N

E5532

IC5 =

TL072

IC7 =

TL084

IC8 =

4030

1 N4004

C15

MIM

:70p

10k0

RS10k0

IC8c

=1

MIM2

n2

2n2

821

R22

R23

R24

12VC60

47p :5V

IC12

16V8V

270k

I

R26

C25

222

C27

2a2

R27

C41

100115VN

E571

16V

7808

0

C61

loll

630

C62

102

63V

8V8V

11852

TD

A1074A

1

112113114

68n

P7Ok

C30

00n

C28

63VC29

220p

220,

C48

C47

25V

100n

R59

C50

C49

2202 25V

100n

C55

C54

220, 25V

100n

R63

2214

R65

8V ®

IC1

IC2

Ii20

ICJ

IC8135

C5C

70

10 n0100n

8V

C8

70n

® Toon

C34

L2

T00n 100pH

AA

A/

Op

250

100n

16V

BC

51 7

rein

960

LSP

C

R64

Re1 = 023037-60002-6101

950012 - 13

LSP

S

SURROUND SOUND PROCESSOR 29

K3 (3:141°C68

1013

tC12 063AAI

C61

C62

001C64

01 L2 10

4

021C19

C35

F124b °D6C18

1.° C"Di

I CM 10 10 CO, C4

049 3agiro

7, gCE

C36

CC co

CC

C50

R4

s IC11

0; 055C56

Ot R63 10 a

136 R4 .--eR 01 IR47 10 9. a

to C221114cc

C71 G__

4- 0,141006C ICaR31

cc

31

(3-- R13

6-6Fine_ "ad)

lamR9 7,,,0occ

P7 P6

Di

C29

CB

t;R7 D4

R5

R6 f1/43- R2

R1

IC1

R4

C40

a

K2

Fig. 6. Printed -circuit board for the surround sound processor. (See also next page)

the phase difference betweenthe two stereo signals.

This direct voltage is ap-plied via IC7d (inverted) andIC7d (non -inverted) to the con-trol inputs (pins 9 and 10) ofIC9. This arrangement ensuresthat when a mono signal ispresent at the inputs (no orhardly any phase difference),the amplification of the VCAcontrolling the centre channelis raised. Conversely, when asurround signal is present(large phase difference), the am-plification of the VCA con-trolling the surround channelis increased.

The degree to which the am-plification of the VCAs is in-fluenced by the control sig-nals is preset by P2 and P3.When the wipers of these con-trols are at earth potential,the amplification is fixed; whenthey are at the opposite end oftheir travel, control is maxi-mum.

Presets P4 and P5 serve toshift the operating point ofthe VCAs to some extent. Theythus make the preset rangewider and, in fact, supportthe operation of P6 and P7. If,for instance, P7 has already setthe surround level to maxi-mum, P5 enables this to beincreased slightly. The sameapplies to P4 insofar as thelevel of the centre channelpreset with P6 is concerned.

The currents through R45and R46 and those throughR48 and R50 are simply addedtogether: there is, therefore, nointeraction between P2 and P4nor between P3 and P5.

Further circuit detailsResistors R3 and R4 and diodesD1 -D4 limit the level of theinput signal to a safe valueand are imperative if the stereosignals are taken from theloudspeaker outputs of theTV receiver. Note that evenline out terminals sometimesprovide a signal at a level wellabove 1 V. If it is absolutelycertain that the line output levelis I V, and this is the onlyinput, the resistors can be re-placed by a wire bridge and thediodes may be omitted.

Bi-colour LED D6 functionsas a kind of signal monitorthat shows the change fromsurround channel to centrechannel and vice versa. In thecase of a surround signal, theoutput of IC8, is high. Since


30 AUDIO & HI-FI

one output of IC8d is at +8 V,both inputs of this XOR arethen high, so that its outputis low. This results in the redsegment of D6 lighting. In thecase of a centre signal, pin 12of IC8d is low, so that its out-put is high, resulting in thegreen segment of D6 lighting.In practice, the changes betweenthe signal are so rapid thatthe LED shows a fluent tran-sition from red to green andback to red again.

The power supply providesthree different voltages. The sec-ondary of the mains trans-former is connected to K3. The12 V input, after rectificationand smoothing, results in asymmetrical supply of ±16 V,which is used to power outputamplifiers IC 10 and IC 11.

From the ±16 V lines, volt-age regulators IC12 and IC13 de-rive a supply of ±8 V, which isused to power the remainderof the circuit.

The 12 V line for the relayis taken directly from K3 andrectified by D8 -D9.

ConstructionThe processor is best con-structed on the PCB illustrated in Fig. 6.Since this board is double sided andthrough -plated, it is not possible to makeit without special tools and equipment.

Populating the board is straightfor-ward and should not present undue dif-ficulties. Note that when the specifiedenclosure is used, capacitors C65 andC66 must be not higher than 38-40 mm.

Use gold-plated connectors for K1 andK2 to ensure good, lasting connections.The positions for these connectors are atthe edge of the board so that all that isnecessary when fitting the board into theenclosure is drilling a few holes in the back

panel through which these sockets canprotrude. Note that they must not touchthe enclosure.

Output amplifiers IC 10 and IC 11 arelocated at the edge of the board so thatthey can be fitted readily to a heat sink.The ICs must be electrically isolated fromthe heat sink by ceramic washers and heatconducting paste.

The photograph in Fig. 3 shows the com-pleted prototype board.

The main requirements of the enclos-ure are that it is made of metal and thatit provides adequate space for the fin-ished board.

Elektor DEFAULT

3.0000

0.0

-3.000

-6.000

-9.000

-12.00

-15.00

-18.00

-21.00

-24.00

-27.00

-30.00

10

AMPL(dB ) vs FREQ(Hz) 27 OCT 9413:14:19

Ap

100 1k 10k 20k

950012 -17

Apart from K1 and K2, fit suitable sock-ets or spring -loaded terminals at the backof the enclosure for connecting the cen-tre and surround loudspeakers. Linkthese terminals with heavy-duty insu-lated wire to points 'C' and 'S' and the ad-jacent earthing points on the board. Thespecified mains entry with integral fuseholder should also be fitted at the backof the enclosure.

The mains on/off switch and D6 shouldbe fitted at the front panel (for which a ready-made foil is not available). The diodeshould be connected to the relevant pointson the board via lengths of flexible

Elektor DEFAULT

3.0000

0.0

-3.000

-6.000

-9.000

-12.00

-15.00

-18.00

-21.00

-24.00

-27.00

-30.00

10

AMPL(dBr) vs FREQ(Hz) 27 OCT 94 11:24:15

A p

100 lk 10k 20k

950012 -18

Fig. 7. Frequency response of the centre channel. Fig. 8. Frequency response of the surround channel.


SURROUND SOUND PROCESSOR Eil

stranded wire.Finally, link the centre pin of K3 to the

mass of the enclosure with the aid of asolder tag.

The completed prototype is shown inthe photograph of Fig. 4.

The output amplifiers are suitable foroperation with load impedances Q,but not lower ones. Thus, for the sur-round channel, two 8 Q loudspeakersmay be connected in parallel only if it isabsolutely certain that the impedance is8 Q. If it is not, connect the speakers inseries: this is safer. It is essential that thetwo speakers are in phase: the +terminalsmust go to the same terminal on theboard: whether this is earth or 'S' doesnot matter.

The centre loudspeaker must be inphase with the main speakers. Since therelevant VCA functions as an inverter, the+terminal of this speaker must be con-nected to the earth point on the board;the -terminal to point 'C'.

CalibrationStart by setting presets P2 -P7 to the cen-tre of their travel, and PI to maximum(fully clockwise).

Inject a (mono) speech signal and ad-just P6 until the sound appears to comefrom the centre speaker. Wait for a sur-round signal (indicated by the red segmentof D6 lighting) and turn P7 till sound ema-nates from the surround speakers. Do notset the level too high, because this leadsquickly to an exaggerated effect. If, how-ever, it is felt that the desired level cannot be obtained with P6 or P7, as the casemay be, adjust P4 or P5, or both, as re-quired.

Next, create a spatial effect by slowlyturning P2 and P3 until the centre channeland the surround channel seem well 'sep-arated'. It is more than likely that P6and/or P7 must then be readjusted. Notethat these controls give an instinctive`wrong' feel: turning them clockwise re-duces the level.

If the surround speakers give exag-gerated reverberation, reduce the delaywith P 1 . In the average living room, adelay of 25 ms appears correct: this cor-responds to P1 being almost at its maxi-mum setting.

Do not be surprised if after watchingand listening to a number of films, somereadjustment of the controls are found de-sirable.

CharacteristicsThe curves in Fig. 7 and 8 show the am-plitude vs frequency characteristics ofthe centre channel and surround channelrespectively. The curves were obtained withan audio analyser. It is evident that theycorrespond closely with the descrip-tions. The -3 dB point of the centrechannel is at 30 Hz. The -3 dB points ofthe surround channel are at 50 Hz and

6 kHz; the -6 dB bandwidth is roughly30 Hz to 7 kHz.

Figure 8 shows that it does not makesense to use tweeters with a linear char-acteristic up to 20 kHz for the surroundchannels.

Both curves make it clear that a sub -woofer must be connected to the main chan-nels and not to the centre channel or sur-round channel.

Parts list

Resistors:R1, R2, R27, R28, R45, R50, R53 -R56 = 47R3, R4 = 1 k52 (see text)R5 -R8, R11, R23 = 10.01(Q, 1%R9, R21 = 11.8 ki2, 1%Rio, R22 = 11.01(Q, 1%R12, R24 = 6.98 kQ, 1%R13, R25 = 4.32 kQ, 1%R14, R26 = 5.62 k4, 1%R15 = 18 kitR16 = 22 kitR17, R18, R36 = 100 lc.QR19, R20 = 5.6 k4R29, R31 = 2.21(QR30, R32 = 6.8 k4R33, R34, R37, R42, R57, R59, R61, R63 = 10 kQR35= 1004R38 = 2.7 icQR39 = 270 k4R40, R41 = 560 IcQR43= 15k4R44 = 12 lcQR.46, R48 = 39R47, R49, R51, R52 = 1 k4

R58, R62 = 560 QR60, R64 = 4-7 QR65 = 5.6 MQR66= 104P1 = 50 ic4 presetP2 -P7 = 10 k4 preset

Capacitors:C1, C2, C25, C27, C45, C52 = 2.2 pF,

polypropylene, pitch 5 mmC3, C5,C16, C18 = 2.2 nFC4, C17 = 3.9 nFC6, C19 = 1 nFC7, C8, C20, C21, C30 -C34, C39, C44, C47,

C49, C51, C54, C56, C58 = 100 nFC9 = 100 pF polystyrene, axialC10, C11, C13, C35, C63, C64, C67 -C70= 100 nF,

ceramicC12, C36, C60 = 47 pF, 25 V, radialC14, C26 = 4.7 pF, 63 V, radialC15 = 270 pFC22 = 68 pFC23, C59, C61, C62 = 10 pF, 63 V, radialC24 = 1 pF, polypropylene, pitch 5 mmC28 = 1 pF, 63 V, radialC29 = 220 pF, 10 V, radialC37, C38 = 47 pF, 16 V, radialC40, C41 = 100 pF, 25 V, radialC42 = 150 nFC43 = 68 nFC46, C53 = 22 pF, 40 V, radialC48, C50, C55, C57 = 220 pF, 25 V, radialC65, C66 = 4700 pF, 25 V, radialC71 = 820 nF

Inductors:L1, L2 = 100 pHL3= 150 pH

Semiconductors:D1 -D4 = zener diode, 4.7 VD5 = 1N4148D6 = bi-colour LED (green/red)D8, D9 = 1N4004B1 = SB102, 10 A, 100 V, for PCB

mountingT1= BC517

Integrated circuits:IC1, IC2 = NE5532IC3 = MN3101IC4 = MN3008IC5 = TL072IC6 = NE571IC7 = TL084IC8 = 4030IC9 = TDA1074AIC10, IC11 = TDA2040IC12 = 7808IC13 = 7908

Miscellaneous:K1, K2 = audio socket for PCB mountingK3 = 3 -way terminal block, pitch 5 mmRe1 = relay 12 V, 5 A, 270 QHeat sink SK57, 37.5 mm high*Ceramic washers Type AOS220*Enclosure 300x45x210 mm (WxHxD)

(117/8x13/4x81/4 in)Mains transformer with 2x12 V, 80 VA

secondaryMains entry with integral fuse holder and

500 mA slow fuseLoudspeaker terminals (spring loaded)or suitable audio socketsMains on/off switchPCB Order No. 950012-1

[950012]

* Available from Dau (UK) Ltd, 70-75Barnham Road, Barnham P022 OES,telephone (01243) 553 031



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SPECIAL INTERESTINTEL SBC 486/133SE Multibus 486 system. 8Mb Ram £1975Zeta 3220-05 AO 4 pen HPGL RS232 fast drum plotter £19503M VDA - Video Distribution Amps.1 in 32 out £375Trio 0-18 vdc bench PSU. 30 amps. New £470Fujitsu M3041 600 LPM band printer £1950 Brand new and boxed 230 volts 1 KVa uninterruptible power supplyVG Electronics 1035 TELETEXT Decoding Margin Meter £3750 from system from Densei. Model MUD 1085-AHBH. Complete withAndrews LARGE 3.1 m Satellite Dish + mount (For Voyager!) £950 . . . .

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VISAESTABLISHED

25 YEARS

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Upper NorwoodLONDON SE19 3XF

A

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V21,V22, V22 BIS

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All prices for UK Mainland. UK customers add 17.5% VAT to TOTAL order amount. Minimum order £10. Bona Fide account orders accepted from Government,Schools. Universities and Local Authorities - minimum account order £50. Carriage charges (A).£3, (A1)=£4.00, (B)=£5.50, (C)=£8.50, (0)=212.00, (E)=515.00,(F)=E18.00, (G)=CALL. Allow approx 6 days for shipping - faster CALL. Scotland surcharge CALL. All goods supplied to our Standard Conditions of Sale andunless stated guaranteed for 90 days. All guarantees on a return to base basis. All rights reserved to change prices / specifications without prior notice. Orderssubject to stock. Discounts for volume. Top CASH prices paid for surplus goods. All trademarks etc acknowledged. 0 Display Electronics 1995. E & 0 E. 1/11



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Electronics Workbench dictates wire placement toyou. EWB limitsyour overall "workbench" layout to1 x 2 pages. EWB has no bussing, page connectors,pa,gebreaks, print scaling, labeling free text fields,netlisting, zoom, undo, and no Toolbar or Toolbox.

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34

UPGRADE YOUR CAR BATTERYCHARGER

Many car battery chargers costing not more than £12-E15 arepretty spartan devices. Car owners should beware of usingsuch chargers which offer no protection whatsoever. Thisarticle describes a simple upgrade circuit that adds voltageand current limiting, and polarity reversal protection, to suchinexpensive chargers.

Design by L. Lemmens

IN spite of their low price, manycheap battery chargers look, well,

impressive because of their smartlyfinished case, heavy-duty switches,solid connecting cables and robustclamps. Considering that the case con-tains a powerful mains transformer,such a charger is certainly not too dearat a price between and £15. A pity,though, that these chargers lack anyform of voltage or current regulation.Chargers which offer these featuresare, of course, more expensive, typi-cally between £25 and £30.

So why not design an upgrade cir-cuit for all those cheap chargers, andmake them competitive with their reg-ulated, but much more expensive,counterparts? As illustrated by Fig. 1,most cheap chargers have plenty ofspace inside to fit a printed circuitboard and some warning devices tosignal overload or error conditions.

The board described here does not

require complex modifications to thelow-cost charger. In fact, it is simplyconnected in series with the output.

How it worksThe circuit diagram of the batterycharger upgrade is shown in Fig. 2.The circuit is intended for 12-V charg-ers with a maximum capacity of about7 A. The essential ingredients are avoltage regulator, IC1, a current lim-iter, IC2, and a 'big' output transistor,T2. The latter functions as the powerstage for both the voltage and the cur-rent limiter, and performs the actualregulation. Two potentiometers areavailable to set the maximum batteryvoltage and the maximum charge cur-rent. If the set values are exceeded, thecharging current is interrupted, and aLED lights to tell you that something isamiss. Similarly, a buzzer soundswhen the battery is accidentally con-

nected the wrong way around.The connections shown at the left-

hand side of the circuit diagram areconnected to the output of the batterycharger, while those at the right-handside go to the battery terminals.

A high -power diode, D5, is insertedinto the positive line to make sure thatno damage can be caused by connect-ing the charger outputs the wrong wayaround to the inputs of the circuit.Interestingly, the diode also allows theexisting bridge rectifier in the chargerto be skipped, and the inputs of theupgrade circuit to be connected di-rectly to the secondary of the mainstransformer. The diode is followed bytwo large reservoir capacitors, C7 andC8, which smooth the direct voltage.

The charging current drawn fromthe mains transformer is fed to thebattery via power resistor R11 andtransistor T2. As already mentioned,the transistor is part and parcel of thevoltage limiter and the current limiter.Since voltage limiting is the most im-portant function for a battery charger,it will be discussed first.

Voltage divider R8 -P1 -R9 is con-nected in parallel with the battery. Thescaled -down battery voltage is com-pared to a fixed reverence level of 4.7 Vby comparator IC1. The reference volt-age is obtained from a zener diode, D2.As long as the voltage at the -input ofIC1 is lower than the reference level atthe +input, the comparator output willbe high. Transistor T1 is then switchedon and consequently supplies basecurrent to T2. The result is that thecharging current is allowed to flowfrom the mains transformer to the bat -

Fig. 1. Bleak House! Although they repre-sent good value for money, most off -the -shelf car battery chargers have a prettybarren interior.


IMPROVE YOUR CAR BATTERY CHARGER

tery. If, after some time, the batteryvoltage rises above the threshold setwith P1, the comparator output swingslow, causing T1 and T2 to be switchedoff. Since the cathode of diode D 1 isthen pulled to ground, this LED drawsjust enough current (via R4) to light.

Transistor T2 remains off until thebattery voltage drops below the setthreshold again. That happens as a re-sult of self -discharging, or because aload starts to draw current. The divideratio of the voltage divider is ad-justable between 2.2 and 3.25 with theaid of potentiometer P1. Multiplyingthese values with the reference voltage(4.7 V), a voltage limiter span of 10.4 Vto 15.2 V is obtained. A fully chargedbattery normally supplies 13.8 V.

The current limiter function is pro-vided by comparator IC2 and currentsensing resistor R11. The inputs of IC2are connected to voltage dividerswhose divide ratios are nearly equal.One, however, has a potentiometer(P2), and is connected behind series re-sistor R11 instead of ahead of it. Whenthe charging current rises to an abnor-mal level, for instance, because of afaulty cell in the battery, the voltage atjunction R1 -R10 drops below that atjunction R2 -R3. Consequently, the out-put of comparator IC2 drops low, draw-ing away the base current of T1. Thiscauses the series regulator to beswitched off and LED D4 to light thatand the current limiter has been actu-ated. In other words, an overload con-dition has been detected.

Because of the instability of thecharging current and the voltageacross C7 and C8, the onset point ofthe current limiter is far less accu-rately defined than that of the voltagelimiter discussed above. The chargingcurrent drops when the battery voltagerises, while the input voltage dropswhen the charging current rises.Fortunately, accuracy is not terriblyimportant in this respect. The currentlimiter built around IC2 really acts as a`dead stop' in case a serious problemoccurs, and is perfect for that func-tion.

The opamps are powered by a sup-ply which takes its input voltage fromthe charger's mains transformer. The12-V supply is entirely conventional,being based on a three -pin fixed volt-age regulator type 7812 and the usualdecoupling capacitors.

Finally, the polarity of the con-nected battery is detected in the sim-plest possible way. If the battery isconnected the wrong way around,diode D7 conducts, and buzzer Bz 1sounds.

ConstructionThe upgrade circuit is best built on theprinted circuit board shown in Fig. 3.

D6

HIC3

1N4001

05

BYW29-100

7812

C4 12

74207100n0V

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6

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4

C1

4V7

Bz1

12V

P1

10k 7

1N4148

940111 - 11

Fig. 2. The main components in the circuit are two comparators and a high -power darlington-type series transistor. Resistor R11 functions as a current sensor.

Construction should not present prob-lems. Resistor R11 must be mounted alittle above the board surface becauseit may run fairly warm. Similarly, tran-sistor T2 must be fitted with a heat -sink, or it may be secured against theinside of the charger enclosure withthe aid of a good -quality electrical in-sulation set.

The extension circuit is simple to in-stall in the battery charger. Disconnectthe rectifier bridge outputs from thebattery output wires. Connect the in-puts (open arrows) of the extensionboard to the bridge rectifier outputs.Next, connect the outputs of the cir-cuit (solid arrows) to the battery out-put wires. That is all. Use heavy-dutywire for the connections - a cablestrength of 2.5 mm2 or greater is rec-ommended.

AdjustmentThe circuit is adjusted as follows.

(1) Connect an adjustable power sup-ply instead of a battery. Shunt thepower supply with a 27-Q, 5 -wattresistor.

(2) Set the power supply to the voltagelevel at which the voltage limitershould act, for instance, 13.8 V.

(3) Set P1 for minimum resistance, andswitch on the battery charger.

(4) Adjust P1 until LED D1 just startsto light.

Next, proceed with the current limiter

adjustment. This requires an ammeterand a 'flat' battery or an adjustablehigh -power resistor. The resistor ismore handy of the two, although itmay be hard to find because of its rat-ings: adjustable between 2 t1 andabout 5 Q, and capable of dissipatingup to 100 W.

(5) Connect the load resistor to thebattery terminals, and insert theammeter in the circuit. Switch theammeter to the 10-A range.

(6) Switch on the battery charger, andadjust the power resistor for the de-sired maximum current, for exam-ple, 5 A.

(7) Adjust P2 until LED D4 just startsto light. If the span of the preset istoo small, resistor R10 may be madea little smaller.

Practical useThe circuit offers a reasonable degreeof protection against misuse. It is, forinstance, capable of withstanding re-verse polarity at the input as well asthe output. If D3 lights, either theinput voltage or the battery is con-nected the wrong way around. If D3lights and the buzzer sounds, the erroris at the battery connections.

Finally, a word about the voltagelimiter adjustment. Referring back towhat has been said about the maincharacteristics of lead -acid batteries inthe article 'Motive -battery charger'


36 POWER SUPPLIES AND BATTERY CHARGERS

I I7 7

Fig. 3. Printed circuit board artwork (board available ready-made through the ReadersServices).

ttr

r

41.

tit

COMPONENTS LIST

Resistors.R1;R2;R5 = 47k0R3;Ro = 27162

R4 = 10k0R6= 11625R7 = 21(122

135 = 12k0Rio = 221(11Rii = 0.112 5WP1:P2 = 10k0 preset H

Capacitors:C1;C6 = 1nFC2;C3 = 100nFC4 = 220pF 40VC5 = 22pF 25VC7;Co = 2200pF 40V

Semiconductors:Di;D4 = low -current LED (red)02 = 4.7V 0.4W zener diode03 = LED, greenD5 = BYW29-10006 = 1N400107 = 1N4148

= BC547T2 = BDV64B1C1;IC2 = CA3130IC3 = 7812

Miscellaneous:Bz1 = d.c. buzzer, 12V.Heat -sink for T2, e.g., Fischer typeSK59, 7K/W.Printed circuit board, order code940111-1 (see page 78).

(Ref. 1), a battery is normally 'fullycharged' if the cell voltage is between2.2 V and 2.3 V. The voltage level fortrickle charging of lead -acid batteriesis, therefore, normally set to 13.8 V.Also, as a rule of thumb, the amount ofenergy to be put into the battery isabout 1.1 to 1.2 times the amount ofenergy drawn from it. For example, acompletely discharged 40-Ah batteryhas to be charged 12 hours at a cur-rent of 4 A.

The maximum current that can besupplied by the present upgrade boardis about 7 A. Larger currents will de-

llo' stroy diode D5 because it has a maxi-mum rating of 8 A. Transistor T2 iscapable of passing up to 12 A. If thecircuit develops a malfunction, it is,therefore, advisable to check D5 first.

(940111)

Reference:Fig 4 If you have finished soldering, your 1. Motive -battery charger, Elektor

board should look like this. Electronics October 1994.



lifBursting with new ideas(The 94/95 Electromail Catalogue

Now available

Part 1More ...Semiconductors, Surface MountTechnology, fuses, batteries,potentiometers, capacitors

Part 2More ...Fire & security, wiringaccessories, lights, plugs,fittings, Datacom products

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40

FOCUS ON: COMPUTER -ASSISTEDDESIGN (CAD) OF SCHEMATICSAND PRINTED CIRCUIT BOARDS

Computers have evolved rapidly over the past few years, and are now used fordesign work that was long thought to be possible by hand only. In modern CAD

systems, for instance, computers have taken over from the traditional pen, paperand ruler. These tools are now completely replaced by advanced screen

operations. In the field of electronics, too, many aspects of design have beentaken over by the computer. The aim of this article is to show how an electronic

circuit plus associated printed circuit board can be designed rapidly andefficiently with the aid of a computer.

By our design and editorial staff.

MHE times when electronic circuits.1 were designed with pen and paper on

a drawing board are a few years behindus. Not only has the computer moved cir-cuit drawing, copying, fault checkingand editing to the desktop monitor, it hasalso greatly simplified and improved thedesign process. Furthermore, new possi-bilities have been added. It is now possi-ble, for instance, to simulate and checkthe operation of an electronic circuitwithout soldering a single component.The thermal behaviour, too, of compo-nents is simple to predict, and 'hot spots',

which are potential sources of trouble,are simple to locate beforehand.

Most electronic designers have twomain requirements as regards computer -aided design: (1) software to produce cir-cuit schematics and (2) software toproduce printed circuit board artwork.Both programs are usually supported bya library editor and a netlist converter.The former is used to edit existing com-ponent parameters stored in libraries,and to create new component libraries.The netlist converter is necessary when-ever data has to be exchanged between a

schematic drawing program and a PCBdesign program from a different manu-facturer. The netlist is a file which con-tains descriptions of all parts used, andthe way they are interconnected. In casethe two programs are related, i.e., pro-duced by the same software house, prob-lems with exchanging data via the netlistfile are unlikely to occur.

The drawing boardThe very first stage of each designprocess is drawing the circuit diagram. Anumber of programs are available forthat purpose. These typically include anumber of libraries which contain com-plete component families. The most obvi-ous of these are passive components,transistors, analogue ICs, TTL, CMOS,etc., although microcontrollers, memo-ries and even sensors may also be in-cluded in the more up-market programs.The description of each component in alibrary comprises its enclosure and thepin functions. In many combinationproducts, this information is divided be-tween two separate libraries: one for thecircuit drawing program, and another forthe PCB design program.

In the process of entering the circuitinto the computer, the user picks thecomponents he or she wishes to use fromthe different libraries. Next, the compo-nents are interconnected to create anelectronic circuit. In some cases, it is pos-sible to include the enclosure and pinoutinformation in the circuit diagram al-ready. That may be very useful becausemany logic integrated circuits, for in-stance, are now available in SMD (sur-face mount device) packages, in additionto the standard DIL case. The pin num-bering may still be the same, however,and the choice of enclosure is not usuallyan issue until the board is designed.Consequently, many programs do not


COMPUTER -ASSISTED DESIGN (CAD) OF SCHEMATICS AND PRINTED CIRCUIT BOARDS

allow you to make your choice until youhave arrived at the PCB design phase.

41

Early warnings!Design faults may already be detectedwhile the circuit is being entered into thecomputer. For instance, the program willalert you to an integrated circuit whosesupply pins are not connected, or ICswhose outputs are interconnected. Theso-called error file produced by the pro-gram's ERC function (electrical rulechecking) tells you if the circuit containsconnections which are less usual.Suspicious, but electrically acceptable,links are retained, however, and the de-cision whether or not modifications arein order is left to the user.

Some programs have two error report-ing levels. An 'error' indicates a grossmistake in the circuit, for instance, ashort-circuit on the supply lines, or a sig-nal which runs from a component outputterminal directly to the ground line. A`warning' is produced if the program hasreasons to suspect that a certain configu-ration can not work. Error and warningreports enable you to debug a circuit inthe early stages of design, which is sureto save time and money later.

Drawing bits and piecesA useful feature of many circuit drawingprograms is their ability to create, storeand retrieve sub -circuits (also calledmodules) which allow circuits to be di-vided into segments. This function pro-duces circuit diagrams which are legibleand, therefore, understandable, despitebeing very complex. Moreover, modulesmay be copied and saved for use in othercircuits, or run off on the printer on sepa-rate sheets. The use of labels and sym-bolic names for certain junctions in thecircuit enable other designers (and your-self, after a couple of months...) to readthe circuit diagram without problems.

There are also systems which enablesignal groups (supply lines, address bus,databus, etc.) to be set off from the rest ofthe circuit. Furthermore, it is often possi-ble to highlight the selected signal group(for example, a microprocessor's addressor data bus) on the screen, giving you animmediate indication of the function of aparticular link or group of links.

In a CAD environment, making alter-ations to a circuit is easy by first break-ing existing links and then entering thenecessary changes. This is in stark con-trast with the traditional pen and paperdesign methods, which are really unsuit-able for making large changes to an ex-isting circuit.

Hard copyFor documentation purposes, it is essen-tial that a circuit diagram can be movedfrom the screen to a printer. Any circuit

I

Fig. 1. A computer makes it possible to draw electronic circuit diagrams quickly and effi-ciently. Thanks to the netlist export option, other programs may use this circuit diagram also(screen snapshot of Orcad/SDT3).

(edif ADFS::HardDisc.$.Design3.Netlist

(edifVersion 2 0 0)

(edifLevel 0)

(status

(written

(timeStamp 1994 11 15 22 04 35)

(program "CadMust-NetConvert" (Version "100"))

(comment " by Usarc, the Netherlands.")

(comment " (c) copyright 1992")

(comment "Input file created at 13 July 1994, 10:07:25"))

)

(library AllComponents

(edifLevel 0)

(technology Unspecified)

(cell root

(view ADFS::IDEDisc4.8.Work.Usarc.Man_cor.PCBs.Example3.Schema3

(viewType NETLIST)

(interface

)

(contents

(instance Cl

(property DEVICE (string "C"))

(property PARTS (integer 1))

(property VALUE (string "10 nF"))(property PACKAGE (string ""))

)

(instance D1

(property DEVICE (string "DIODE"))

(property PARTS (integer 1))

(property VALUE (string "1N4148"))

(property PACKAGE (string ""))

)

Fig. 2. This text file shows the structure of an EDIF file. EDIF allows programs from differentmanufacturers to communicate with each other.


42 GENERAL INTEREST

drawing program should offer a widerange of drivers to support at least themost popular of today's bewilderingrange of printers. If the program runsunder a graphics user interface, for in-stance, Windows, use is made of theprinter drivers offered by the 'shell' pro-gram. The number of CAD software pro-grams running under Windows is on theincrease recently. The computing powerof today's 486 and Pentium -based ma-chines allows these complex programs torun smoothly on a Windows platform.Hard copy of the circuit diagram(s) andthe text files which contain, among oth-ers, a list of all parts used, are invaluablefor documentation purposes.

In many cases, the final aim is not toprint the circuit diagram on paper, but touse it to produce a printed circuit board.That, obviously, requires a means of ex-porting the output data of the circuitdrawing program to a PCB design pro-gram. The step from electrical design(circuit diagram) to physical design (cop-per tracks on a board) is made with theaid of a netlist.

Export/import: the netlistAS already hinted at, the netlist has akey function in each CAD environment.It is used to convey information betweensub -programs in the CAD system. Inpractice, each CAD system has its ownnetlist format, which allows a quick ex-change of data between sub -programs inthe same design environment. The bigdisadvantage is that conveying the sameinformation to a different hardwareand/or software platform without cor-rupting the data is fairly difficult.Fortunately, over the past few years acouple of standard formats have evolvedfor netlists. The most important of theseare EDIF (electronics Design Inter-change Format) and Spice. The latter isof particular interest if you want to feedyour schematic drawing program into anelectronic simulation program. That isachieved by including, in the netlist file,information on the electrical behaviourof the relevant components.

As far as transferring informationfrom a circuit drawing program to a PCBdesign program is concerned, EDIF is theobvious choice because all well -estab-lished programs support this format. Itshould be noted, however, that advancedoptions such as back -annotation (i.e.,comparing the connections list producedby the circuit drawing program with theactual connections on the PCB, and viceversa) are not always possible whenEDIF is used.

Spice and EDIF are 'all -ASCII' for-mats which can be read and modified byalmost any word processor. As such, theyhave essential functions in documentinga project. Figure 2 shows an extractfrom an EDIF listing.Some of today's more advanced CAD

Fig. 3. After importing the netlist, all compo-nents are thrown haphazardly on the board.The result is called a rats nets (screen snap -snot, zoomed in, program: Ultiboard).

packages also offer macro functions togenerate the netlist. Such macros enablecommunication with almost any designsystem.

Printed circuit boarddesignBased on what sales people will tell you,you could be lead to believe that design-ing a printed circuit board with the aid ofCAD software is a trifle. 'Well Sir, juststart by selecting a standard PCB size

ESOP

and the desired number of copper layers.Next, load the netlist produced by thedrawing program, and away you go withthe automatic component placer. Oncethat function is finished, the componentsare at the appropriate positions on theboard, and the auto -router may be calledto finish the job. All you have to do is waituntil a perfect PCB layout appears on thescreen. That gives you just enough time toswitch on your laser printer and tele-phone around for the cheapest PCB man-ufacturer.'

Alas, things are a little more compli-cated in practice. Although many soft-ware suppliers boast about the power oftheir component placers and autorouters,few PCB designers will rely on thesetools for the full 100 per cent. In manycases, the work is split between the com-puter and the designer. Supply tracksand 'critical' analogue networks are thenpositioned manually, and the rest of thework is left to the autorouter to sort out.

In practice, a PCB designer starts byselecting the board size, and then thenumber of layers. Once that is done, thescreen displays an image which repre-sents the empty board. Each layer usu-ally has its own colour. The next step isto import the netlist produced by the cir-cuit drawing program. The result is arat's nest of components thrown on theboard with a all interconnections tangledin a heap. Figure 3 shows an example.At this stage, it is wise to check that theparts are in the right enclosures. Inmany cases, that is very simple because aparticular component comes in one caseonly. The enclosures available for a cer-tain component should be defined in the

Fig. 4. Most programs allow a component to be picked up and moved to another location onthe board (program: Ultiboard).


COMPUTER -ASSISTED DESIGN (CAD) OF SCHEMATICS AND PRINTED CIRCUIT BOARDS 43

File Edit View Tools Options Library Symbol Help

L.g.i Le_121Z Round p,id 0.essn

Y120 x1110 Loaded a 6.311 Schematic qle

Fig. 5. Schematics drawing in the Windows era: Quickroute Pro+.

View Tools Options Library Symbol Help

A OL.J2J

component library. The program willthen automatically tell you the alterna-tives with each component.

Once the component enclosures havebeen decided on, components whose loca-tion can not be allowed to change, for in-stance, connectors, are 'fixed' on theboard. Next, the automatic componentplacer may be called up. Depending onthe conditions you set up for this utility,this utility is capable .of establishing theoptimum position of the components onthe board. Although quite a few condi-tions and design rules may be defined forthe component placer, most designerswill prefer to do the component place-ment themselves. An interesting compro-mise between automatic and manualcomponent placement is the ability ofsome programs to start by locking criti-cal components at a certain position onthe board. Next, the automatic place-ment tool is allowed to move the less crit-ical parts across the circuit board.Alternatively, some programs allow theauto -locator to operate on a selectednumber of components only.

Rotating components, or swappingpins and gates with logic ICs, may helpto simplify finding the best possibleboard layout. Some CAD program enableyou to define 'keep out' areas on theboard, where no components or copper

LTJ Round pad 0.0551n tracks are allowed. Such areas may benecessary to enable a hole to be drilled orfraised later. Alternatively, they mayhelp to improve the screening betweentwo sub -sections of the circuit. In mostcases, the software is capable of manag-ing keep -out areas quasi -automatically.The use of a grid, finally, makes for aneat component arrangement on the

IIboard.

Enter the autorouterWhen, after careful editing, the best pos-sible component locations have been es-tablished, the links between thecomponents have to be turned into cop-per tracks. Like component placement,this so-called `routeing' may be donemanually or automatically. The softwareindicates each track drawn by showing athin line on the screen, or by highlightingthe copper pads which are being inter-connected. In this way, the user is able tofind the optimum route for a track acrossthe board, without running the risk offorgetting a connection. Should a partic-ular connection turn out to run lessfavourably, it is often possible to relocatethe routeing, or undo it. By doing so, the

I Y1.50 23456 -MT B II 'x1.00 Loaded a 17.6K NI -

Fig. 6. Example of a PCB design producedwith the aid of a CAD system (screen snap-shot, zoomed in, of Quickroute 3.0 Pro+).Note that this particular program allows wirelinks to run diagonally across the board.


44 GENERAL INTEREST

le

Advanced Schematic CaptureEdit place Library Tools Options Zoom Into Window Help

I ii,tf dd

ell li7-1-71 Preferences...Sheet...Hot Keys...Auto -Pan..Memory Monitor...

I

(inflate Current TemplateSet Template File Name.

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ri 0,/ Status BarJ Command Status BarZ Scroll Bars

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J Project Manager,/ Component Browser

JVisible GridZ Snap GridJ Electrical Grid

Open...Save As..

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Text 11 Jump JI,Edit

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X240 Y 440 Setup System Preferences

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Fig. 7. Protel Advanced Schematic Capture in action.

relevant component may be repositionedon the board, or a different track routemay be defined.

While the track pattern is being built,screening areas may be defined betweentracks. With large copper areas, it is im-portant that the program allows them tobe given a raster to facilitate soldering (asmall copper area is easier to heat than alarge one). Screening between parallelrunning tracks considerably reducescross -talk levels. To ensure that the PCBlayout has a one-to-one correspondencewith the circuit diagram, the PCB designprogram should produce a netlist also.The so-called back annotation utility ofthe CAD program then compares thePCB netlist with the circuit diagramnetlist. If there are no differences, thePCB layout is a one-to-one electrical copyof the circuit diagram. The program willalso check for short-circuits betweentracks, or tracks which are too close toanother. If the PCB is modified with re-spect to the circuit diagram (for instance,as a result of pin or gate swapping), thatwill be abundantly clear in this phase ofthe design process.

A feature called forward annota-tion, also referred to as ECO (engineerchange order) appears to be a less wellknown than back annotation. Forwardannotation makes it possible to importchanges made with the aid of a circuitdrawing program into an existing boardlayout. This is achieved by combining thenetlist of the modifications with that ofthe printed circuit board. Unfortunately,because the ECO function is fairly diffi-cult to implement, only a few high -endCAD packages actually support this use-ful function.

The final product

The last step in the design phase in-volves producing transparent filmswhich can be used by the PCB manufac-turer. Such films are usually producedwith the aid of a file written in theGerber format. Traditionally, this is anarea dominated by plotters, in particu-lar, Gerber photoplotters which are thede facto standard in the PCB productionindustry. These plotters use an x -y coor-dinates system and have a built-in li-brary containing standard images ofcopper spots. These spots are on a trans-parent disc, and are transferred to thephotosensitive layer with the aid of aflash light. The copper tracks consist oflines draw between two coordinates.

Meanwhile, modernized versions ofthe Gerber photoplotter have arrived,which copy the track image into a mem-ory, just like a laser printer. Next, the in-formation is transferred onto film by anexposure operation.

Gerber files are accompanied by a doc-ument containing additional informationon technical specs including the metricstandard and the accuracy of the Gerberdata. This information may be requiredby the PCB manufacturer to do his pro-duction equipment settings. Informationrepresenting the hole pattern (ExcellonNC drill files) and the component mount-ing plan is supplied in separate files.Furthermore, a document is suppliedwhich states the total number of holes tobe drilled, and their sizes.

Finally, more up to date file formatssuch as Postscript are reported to gainrapid acceptance in the PCB productionindustry. (950001)

Addresses

UlitiCap & Ultiboard:Ultimate Technology UK Ltd., 2Bacchus House, Calleva Park,Aldermaston, Berkshire RG7 4QW. Tel.(01734) 812030, fax (01734) 815323.

PCB Designer (Windows 3.1):Niche Software, 22 Tavistock Drive,Belmont, Hereford HR2 7XN. Tel.(0432) 355 414.

Easy -PC (Schematic and PCB CAD)Number One Systems, Harding Way,St. Ives, Carobs PE17 4WR. Tel.(01480) 461778, fax (01480) 494042.

BoardCapture, BoardMaker,BoardRouterTsien (UK) Ltd., Aylesbury House,Wenny Road, Chatteris, Cambs PE166UT. Tel. (01354) 695959, fax (01354)695957.

Orcad/SDT31049 S.W. Baseline St., Suite 500,Hillsboro, OR 97123, U.S.A. Tel. (+1)503 640 5007.

QuickRoutePOWERware, 14 Ley lane, MarpleBridge, Stockport SK6 5DD. Tel./fax(061) 4497101.

Protel Design System for WindowsProtel Technology Inc., 4675 StevensCreek Blvd, Suite 200, Santa Clara, CA95051-6764, U.S.A. Tel. (+1) 408 2438143, fax (+1) 408 243 8544.

LayolBaas Electronics by, Rijksstraatweg 42,NL-3281-LW Numansdorp, Holland.Tel. (+31) 1865 4211, fax (+31) 18653480.

Programs for analogue simulationonly:

Electronics WorkbenchRobinson Marshall (Europe) PLC,Nadella Building, Progress Close,Leofric Business Park, Coventry,Warwickshire CV3 2TF. Tel. (0203)233216, fax (0203) 233210.

SpiceAge for WindowsThose Engineers Ltd., 31 BirkbeckRoad, London NW7 4BP. Tel. (0181)9060155, fax (0181) 906 0969.

vt.0-4


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46

NEW BOOKSDigital Logic DesignBy Brian HoldsworthISBN 0 7506 1615 6Price £ 19.95 (soft cover)This third edition of a classic student text reflects the devel-opments that have taken place in the digital field in recent years.For instance, the introduction of programmable logic, MSI cir-cuits and VLSI circuits has resulted in the virtual eliminationof circuit design using discrete gates. None the less, studentsshould have a firm grasp of the basic principles of logic de-sign, and for this reason the chapters dealing with the elementaryaspects of the subject have been retained from the earliereditions.

Another important change has been the introduction of newfunctional logic symbols as detailed in BS3939, Part 12. It isstill common practice in many educational establishments toteach logic design in terms of the old symbology and unfor-tunately there are few textbooks available that use the newlogic symbols. However, manufacturers data sheets now de-scribe their products with the aid of the new symbols and itis, therefore, important that students of the subject shouldbe able to interpret these symbols when they encounter them.

Incorporating these changes, and others, this book re-mains an excellent source for anyone studying digital tech-niques.Published by Butterworth -Heinemann*.

Principles of Transistor CircuitsBy S.W. AmosISBN 0 7506 1999 6Price £ 17.95 (soft cover)This eighth edition of a book that was first published more thanthirty years ago remains of importance. The previous editionshave provided students and practitioners with a text theycould rely on to keep them at the forefront of transistor circuitdesign. This seminal work, now presented in a clear new for-mat, has been completely updated to include the latest devicessuch as laser diodes, Trapatt diodes, optoisolators, GaAs tran-sistors, as well as the most recent line output stages andswitch -mode power supplies.

Although integrated circuits have widespread application,the role of discrete transistors is undiminished, both as im-portant building blocks which students must understand andas practical solutions to design problems, especially where ap-preciable power output or high voltage is required.

New circuit techniqes in this edition include current -dump-ing amplifiers, bridge output stages, dielectric resonator os-cillators, crowbar protection circuits, thyristor field timebases,low -noise block and SHF amplifiers in satellite receivers, videoclamps, picture enhancement circuits, motor drive circuits invideo recorders and camcoders, and UHF modulators.Published by Butterworth -Heinemann*.

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Build your ownElectronic Test Instruments

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Short course 8051/8032Microcon-trollers and assemblerThis book presents a course whichdescribes the hardware and thesoftware to make a completemicrocontroller system. The controllerused is selected from the MCS-51family produced by Intel and others.

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SMT ProjectsThis book describes the specialfeatures of surface mount technologyand how to work with surface mountdevices on the workbench. It includesover 20 construction projects, all ofwhich have many practicalapplications in and around the homeand workshop.

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For testing and inspecting electrical and electronicequipment a multitude of electronic test instruments isrequired. Most of these instruments are, of course,commercially available. However, for all kinds of reason(cost, challenge, for instance) many reserachers,enthusiasts and experimenters like to build suchinstruments themselves.This book will help them: it contains detailed designs for17 measuring instruments, seven generators andanalysers, ten miscellaneous instruments and a numberof ancillary and auxiliary circuits.

The designs range from a simple multicore tester to asophisticated logic analyser. Most of the designs containa special printed circuit (or circuits), full-scale drawings ofwhich (with some exceptions) are given in an appendix tofacilitate the photographing and subsequent production ofthe boards.Beginners in electronics will find the first chapter, dealingwith measurement techniques, a good introduction to thefascinating world of electronic test and measurement.

450 pages; 332 illustrations;235 x 170 mmISBN 0 905705 37 8Price £ 15.95 ($ 29.50)

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Databook 5: Application NotesThis book contains a large number ofcollected Application Notespublished by well-known European,American and Japanese chipmanufacturers. The notes cover bothanalogue and digital circuits and forma rich source of inspiration for allelectronic designers.

320 pages; illustrated;210x140 mmISBN 0 905705 33 5Price £ 10.95 ($ 20.25)

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48

MOSFET LOGIC INVERTERS

WiENEVER you need a single in-verter in a digital circuit, con-

sider using a MOSFET, which is oftencheaper and easier to fit on the boardthan a six -fold inverter 4049 IC ofwhich five gates remain unused.

Figure 1 shows two logic invertersbased on n -p -n and p -n -p bipolar tran-sistors. The base circuit of both tran-sistors contains a relatively high valueresistor (for instance, 10 kS1), whichserves to limit the base current. At theoutput, a low -value resistor (here,2.2 k52) is inserted in the collector lineto drop the output voltage. That bringsthe parts count of a transistor -basedlogic inverter to a total of three.

The above inverter circuits may besimplified by using MOSFETs (metaloxide semiconductor field effect tran-sistor), which operate with zero -powerdrive signals. Since MOSFETs, unlikebipolar transistors, have a very highinput impedance, they do not need acurrent limiting resistor at the gate.The inverter's component count istherefore reduced to two. Figure 2shows schematics of two MOSFET in-verters. The one to the left is based onan n -channel MOSFET (equivalent toan n -p -n transistor), and the one to

By G. Kleine

the right, on a p -channel MOSFET(equivalent to a p -n -p transistor). TheMOSFETs listed in the drawing aretypical examples of so-called enhance-ment (or 'normally off) types.

The MOSFET may be looked uponas a switchable resistor, which as-sumes a very high value at Ugs=0 V.Starting at a certain value of Ugs (theso-called pinch -off voltage, Up), thedrain -to -source junction resistancebegins to drop rapidly (see Fig. 3).

MOSFETs typically used for logic in-verters are the BS170 (n -channel) and

BS250 (p -channel), which are suppliedin TO92 packages. If you need SMD(surface mount device) versions, usethe respective equivalents BSS123 andBSS84 which come in SOT23 cases.The pinning of the four devices isshown in Fig. 4. Whenever you handleMOSFETs, be sure to observe precau-tions against damage caused by staticelectricity.

BS170 BSS123BS250 BSS84

AA

S

G

S G

D

TO92 SOT23

950013-14

The oscillograms in Fig. 5 clearly il-lustrate the superiority of MOSFETsover bipolar transistors when used inlogic inverters. The bipolar type BC550(Fig. 5a) responds slowly to the nega-tive -going edge of the input signal(upper trace), causing a too short andbadly defined inverted output signal.Although the response of a dedicatedswitching transistor type BSX21(Fig.5b) is a great improvement on theBC550, the best results are obviouslyobtained with a BS170 MOSFET (Fig.5c) which ensures very fast responseand crisp signal edges. (950013)

5a

Chan 1 : 1 ps / 2V Chan 2 : 1 ps / 1V 950013-15

5b Chant : 1 ps / 2V Chan 2 : 1 ps / 1V

950013-16

5c

Chan 1 : 1 ps / 2V Chan 2 : 1 ps / 1V 950013-17


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Pico Releases PCPotentialPico's Virtual Instrumentation enable you to use yourcomputer as a variety of useful test and measurementinstruments or as an advanced data logger.

Hardware and software are supplied together as a package- no more worries about incompatibility or complex set-upprocedures. Unlike traditional 'plug in' data acquisition cards,they simply plug into the PC's parallel or serial port, makingthem ideal for use with portable PC's.

Call for your Guide on 'Virtual Instrumentation'.

PicoLogAdvanced data

logging software.

PicoScope'Virtualinstrument'software

Pond temperature

(

NEW 541-16 Logic Analyser NEW 7fre-/00 Virtual InstrumentPocket sized 16 channel Logic Analyser Dual Channel 12 bit resolution

Connects to PCserial port.

High Speed-up to 50MHzsampling.

Internal andexternalclock modes.

8K Trace Buffer.

5.611- /6with software, powersupply and cables £ 219

"ove-lo fove-,/1 Channel 8 bit 11 Channel 10 bit

Digital Storage Scope Spectrum Analyser

Frequency MeterChart RecorderData Logger

VoltmeterThe ADC -100 offers both a high

sampling rate (100kHz) and a highresolution. It is ideal as a general

purpose test instrument either in thelab or in the field. Flexible input ranges

(±200mV to ±20V) allows the unit toconnect directly to a wide variety of signals.

riVe-/00 with PicoScope £199with PicoScope & PicoLog £209

)47)e-121 Channel 12 bit

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Lowest cost Digital output High resolution Highest resolution Up to 22kHz sampling Up to 18kHz sampling Up to 17kHz sampling 2Hz sampling - 16bit 0 -5V input range 0 -2.5V input range 0 -5V input range ± 2.5V input rangeThe ADC -10 gives yourcomputer a singlechannel of analog input.Simply plug into theparallel port and yourready to go.

/417,e-/0 withPicoScope £49PicoScope &PicoLog £59

The ADC -11 provides11 channels of analoginput in a case slightlylarger than a matchbox.It is ideal for portabledata logging using a"notebook" computer.

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Carriage UK free, Overseas £9Oscilloscope Probes ( x1, x10 ) £10Existing ADC 10/11/12/100 users can add PicoLog for £25

The ADC -12 is similar tothe ADC -10 but offers animproved 12 bit (1 partin 4096) resolutioncompared to the ADC -10's 8 bit (1 part in 256).

74De-/2 withPicoScope £85

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The ADC -16 has thehighest resolution of therange, it is capable ofdetecting signal changesas small as 40 pV. Pairsof input channels can beused differentially toreject noise. Connects toserial port.

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SURVEILLANCEPROFESSI4NVAL 011ALITY KITS

Whether your requirement for surveillance equipment is amateur, professional or you are just fascinated by this unique area ofelectronics SUMA DESIGNS has a kit to fit the bill. We have been designing electronic surveillance equipment for over 12 yearsand you can be sure that all our kits are very well tried, tested and proven and come complete with full instructions, circuitdiagrams, assembly details and all high quality components including fibreglass PCB. Unless otherwise stated all transmittersare tuneable and can be received on an ordinary VHF FM radio.

Genuine SUMA kits available only direct from Suma Designs. Beware inferior imitations!UTX Ultra -miniature Room TransmitterSmallest room transmitter kit in the word! Incredible 10mm x 20mm including mic.3-12V operation. 500m range £16.45

MTX Micro -miniature Room TransmitterBest-selling micro -miniature Room TransmitterJust 17mm x 17mm including mic. 3-12V operation. 1000m range £13.45

STX High-performance Room TransmitterHi performance transmitter with a buffered output stage for greater stability and range.Measures 22mm x 22mm including mic. 6-12V operation, 1500m range £15.45

VT500 High -power Room TransmitterPowerful 250mW output providing excellent range and performance. Size 20mm x40mm. 9-12V operation. 3000m range £16.45

VXT Voice Activated TransmitterTriggers only when sounds are detected. Very low standby current. Variable sensitivityand delay with LED indicator. Size 20mm x 67mm. 9V operation. 1000m range £19.45

HVX400 Mains Powered Room TransmitterConnects directly to 240V AC supply for long-term monitoring. Size 30mm x 35mm.500m range £19.45

SCRX Subcarrier Scrambled Room Transmitter

Scrambled output from this transmitter cannot be monitored without the SCDM decoderconnected to the receiver. Size 20mm x 67mm. 9V operation. 1000m range £22.95

SCLX Subcarrier Telephone TransmitterConnects to telephone line anywhere, requires no batteries. Output scrambled sorequires SCDM connected to receiver. Size 32mm x 37mm. 1000m range £23.95

SCUM Subcarrier Decoder Unit for SCRXConnects to receiver earphone socket and provides decoded audio output toheadphones. Size 32mm x 70mm. 9-12V operation £22.95

ATM Micro Size Telephone Recording InterlaceConnects between telephone line (anywhere) and cassette recorder. Switches tapeautomatically as phone is used. All conversations recorded. Size 16mm x 32mm.Powered from line £13.45

*** Specials ***OLT/UBLRX Radio Central SwitchRemote control anything around your home or garden, outside lights, alarms, pagingsystem etc. System consists of a small VHF transmitter with digital encoder and receiverunit with decoder and relay output, momentary or alternate, 8 -way dii switches on bothboards set your own unique security code. TX size 45mm x 45mm. RX size 35mm x90mm. Both 9V operation. Range up to 200m.Complete System (2 kits) £50.95Individual Transmitter DLTX £19.95Individual Receiver DLRX £37.95

IM1X-1 Micro BroadcasterNot technically a surveillance device but a great ideal Connects to the headphone outputof your Hi-Fi, tape or CD and transmits Hi-Fi quality to a nearby radio. Listen to yourfavourite music anywhere around the house, garden, in the bath or in the garage andyou don't have to put up with the DJ's choice and boring waffle. Size 27mm x 60mm.9V operation. 250m range £20.95

A

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UTLX Ultra -miniature Telephone TransmitterSmallest telephone transmitter kit available. Incredible size of 10mm x 20mm!Connects to line (anywhere) and switches on and off with phone use.All conversation transmitted. Powered from line. 500m range £15.95

TLX700 Micro -miniature Telephone TransmitterBest-selling telephone transmitter. Being 20mm x 20mm it is easier to assemble thanUTLX. Connects to line (anywhere) and switches on and off with phone use. Allconversations transmitted. Powered from line. 1000m range £13.45

STLX High-performance Telephone TransmitterHigh performance transmitter with buffered output stage providing excellent stabilityand performance. Connects to line (anywhere) and switches on and off with phone use.All conversations transmitted. Powered from line. Size 22mm x 22mm.1500m range £16.45

TKX900 Signalling/Tracking TransmitterTransmits a continous stream of audio pulses with variable tone and rate. Ideal forsignalling or tracking purposes. High power output giving range up to 3000m. Size25mm x 63mm. 9V operation £22.95

CD400 Pocket Bug Detector/LocatorLED and piezo bleeper pulse slowly, rate of pulse and pitch of tome increase as youapproach signal. Gain control allows pinpointing of source. Size 45mm x 54mm. 9Voperation £30.95

CD600 Professional Bug Detector/LocatorMulticolour readout of signal strength with variable rate bleeper and variable sensitivityused to detect and locate hidden transmitters. Switch to AUDIO CONFORM mode todistinguish between localised bug transmission and normal legitimate signals such aspagers, cellular, taxis etc. Size 70mm x 100mm. 9V operation £50.95

QTX180 Crystal Controlled Room TransmitterNarrow band FM transmitter for the ultimate in privacy. Operates on 180 MHz andrequires the use of a scanner receiver or our QRX180 kit (see catlogue). Size 20mm x67mm. 9V operation. 1000m range £40.95

QLX180 Crystal Cointrolled Telephone TransmitterAs per OTX180 but connects to telephone line to monitor both sides of conversations.20mm x 67mm. 9V operation. 1000m range £40.95

11SX180 Line Powered Crystal Controlled Phone TransmitterAs per OLX180 but draws power requirements from line. No batteries required. Size32mm x 37mm. Range 500m £35.95

QRX180 Crystal Controlled FM ReceiverFor monitoring any of the 'CF range transmitters. High sensitivity unit. All RF sectionsupplied as a pre -built and aligned module ready to connect on board so no difficultysetting up. Outpt to headphones. 60mm x 75mm. 9V operation £60.95

A build-up service is available on all our kits if required.UK customers please send cheques, POs or registered cash. Please add£1.50 per order for P&P. Goods despatched ASAP allowing for chequeclearance. Overseas customers send sterling bank draft and add £5.00 perorder for shipment. Credit card orders welcomed on 0827 714476.

OUR LATEST CATALOGUE CONTAINING MANY MORE NEWSURVEILLANCE KITS NOW AVAILABLE. SEND TWO FIRSTCLASS STAMPS OR OVERSEAS SEND TWO IRCS.

rr


Digital circuits operate ondata: facts and numbers

(which are a kind of fact).Unless a circuit 'knows' somedata, there is nothing for it towork on; it is just a useless col-lection of wires and compo-nents. This month, we studythe ways in which digital cir-cuits can be supplied withdata.

SwitchesOne of the simplest ways ofsupplying data to a digital cir-cuit is to use a single -polesingle -throw switch, althoughvarious types of switch can beused. In the circuits of Part 1we suggested the use of a mi-croswitch to inform a digitalcircuit whether a door is openor closed. Similarly, a push-button switch on the door in-forms a door -alert system (andthe occupants of the house)that there is somebody waitingoutside the door. A switch inthe form of a pressure -padmay be used to inform a secu-rity system that there is an in-truder in the room.

MICRO -SWITCH

TO COUNTER

940120 - III - 27

Fig. 17

Although an ordinary push-button may be adequate for in-putting information to a door -alert system, there are circum-stances in which this is toosimple a solution. Take the ex-ample of the door and mi-croswitch and suppose that, in-stead of simply lighting a lampto show the state of the door,we want to know how manytimes the door has beenopened. The switch is to beconnected to a digital counter

THE DIGITAL SOLUTIONPart 3 Acquiring Data

By Owen Bishop

In this series we look closely at digital electronics,what it is, what it does, how it works, and its

promise for the future.

circuit. There is more to besaid about counters in a laterissue but, for the moment, allwe need to specify is that thecounter state is to be increasedeach time its clock input de-tects a change of level fromhigh to low. Figure 17 is a cir-cuit that provides a high out-put level when the switch (anddoor) is shut and a low levelwhen the switch (and door) isopen. Opening the door causesthe level to change from highto low and advances thecounter. Closing the doorcauses a change from low tohigh, but this has no effect onthe counter.

+U

a.

0

DOOR DOORSHUT OPENING

DOOROPEN

TIME940120 - II - 28

Fig. 18

One of the disadvantages ofmechanical switches is thattheir contacts open and closeseveral times when the switchis open and when it is closed.When the switch of Fig. 17 isopened, the output from thecircuit may show severalswings between +V and 0 V be-fore it finally settles to 0 V(Fig. 18). It may take severalmilliseconds to do this and pro-duce numerous short pulses.This is no problem when weare using a switch to controlan indicator lamp for the eyecan not detect the flickering ofthe lamp. But the digital

counter has a very short re-sponse time and is easily ableto count all the pulses shownin Fig. 18. Counters work fastand detect every change ofvoltage. It appears to thecounter that the door has beenopened and closed three timesbefore it is finally left open.The effect is know as contactbounce and is a source of error.

MICRO -

SWITCH b 1100n

INPUT

Fig. 19

TO COUNTER

940120 - III - 29

The cure for contact bounceis debouncing. Figure 19shows one way of debouncingthe switch of Fig. 17. The logicgate is a NOT gate, so the mi-croswitch and resistor havebeen interchanged. An ordi-nary NOT gate can be used, butit is preferable to use one witha Schmitt trigger input as indi-

OUTPUT

cated by the symbol in the box.When the door is opened, theswitch opens and the voltageinput to the gate rises. Thegate output falls, which in-creases the counter state byone as before. The effect of thecapacitor is to make the volt-age level at the input of thegate change more gradually; itpartially smoothes out the for-mer discrete pulses (Fig. 20).The input voltage rises but, be-cause of the Schmitt triggerinput, there is no change inthe state of the output until itrises above the upper thresh-old. When the voltage fallsagain, it has no effect on theoutput unless it falls below thelower threshold. The capacitorprevents the voltage changingto this extent, so there is onlyone change of state when theswitch is openend, and onlyone opening of the door is reg-istered. Similarly, there is onlyone change when the switch isclosed. The circuit would workwith an ordinary NOT gate, butthe advantage of using aSchmitt trigger gate is that thethresholds are set furtherapart, so the debouncing ismore effective. Debouncingcomplies with the general prin-ciple of digital circuitry thatlogic levels are to be high orlow and that intermediatestates are to be eliminated asfar as possible.

The drawback of the circuitof Fig. 17 is that it relies onthe capacitor to smooth overthe irregularities of the opera-tion of the switch. This intro-

I UPPERTHRESHOLD

/11 II II N

I

(1%

11I LOWERTHRESHOLD----------------

/INPUT

Fig. 20

TIME940120 - Ill - 30


THE DIGITAL SOLUTION - PART 3

940120 - - 31

Fig. 21

duces a time factor, for there isa minimum time required forthe capacitor to be eithercharged or discharged to allowthe voltage level to change.The larger the value of the ca-pacitor and of the resistors, thelonger the time and the moreefficiently the key is de -bounced. But this makes it im-possible for the circuit to re-spond to genuine rapidchanges in the state of the key.Figure 21 shows an alterna-tive debouncing circuit whichis more complicated but allowsfor almost instant repetition.The heart of the circuit is aset -reset (R -S) bistable (US:flip-flop). We shall say moreabout bistables in a futureissue, but for the present takea bistable to be a digital sub -

circuit with two inputs (S andR) and an output Q. When S ismade high, the bistable is setand Q goes high. When R ismade high, the bistable isreset and Q goes low. In thiscircuit the inputs are heldhigh, except when the switchconnects them to 0 V. In thestate shown in Fig. 21, reset isheld high so the bistable is inthe reset state with output Qlow. When the switch is moved,the S input immediately goeshigh and the bistable changesstate to 'set' with Q high. Thishappens on the first occasionthe contact is broken. It is aproperty of the bistable that,once it has been set, it can notbe reset except by a low inputto its reset terminal. Any sub-sequent makes and breaks atthe set terminal have no effect.

KeyboardsWhen the input to a digital cir-cuit is by way of more than onekey, the circuit is required todetect which key has beenpressed. For example, considerthe 6 -pad key of Fig. 22. Thekeys are numbered 0 to 5. Theoutput comes from a set of fourR -S bistables, each of whichprovides one binary digit (bit)to make up the output. Thekeys are connected to the

14: Ptl: W. PI: ttl: Prl:

At '44t At . FF D 0 D

At At At At..

FP c

I0At AtAt At sit

B

R FF B

At AtAt lit

0 APP A

OUTPUT = DCBA

Fig. 22

D

o+

OB

940120 - Ill - 32

Fig. 23

anodes of a diode matrix. Theset and reset inputs are con-nected to the cathodes. Theconnections are such that,when a key is pressed, certainbistables are set and certainothers reset. The Q outputstake on the values of the ap-propriate binary number. Forexample, if key 5 is pressed,the set inputs of bistables Aand C are made high and thereset inputs of bistables B andD are made low. The outputfrom the bistable array is0101, the equivalent of decimal5. Actually, we need only threebistables to encode six keys.With the four bistables shownin Fig. 22, it is possible to en-code a keyboard of up to 16keys.

In Fig. 22 the keys are notdebounced. Debouncing cir-cuits can be added, but usuallyit is preferable, in devices thatare complicated enough to re-quire several keys, for the cir-cuit to undertake the debounc-ing function automatically. Thestate of each key is monitoredregularly, several times a sec-ond, and registered in the cir-cuit. If the state of a key haschanged since it was last moni-tored, it is checked again to seeif it has settled to a new state.If so, the new state is regis-tered. This is known as soft-ware debouncing and is com-monly used in computers.

One snag with this type ofkeyboard is what to do whenthe operator presses two keysat the same time. This can eas-ily happen with fast typing

940120 - - 33

since one key may not havebeen released before the nextone is pressed. The solution tothis is to use a priorityencoder. This is a logic circuitthat gives priority to oneinput, usually that of highermagnitude. Thus, if keys 3 and5 are pressed at the sametime, the output of the prioritycoder is 5.

Keyboard encoders areavailable as integrated circuits(ICs) containing all the logicnecessary to produce a binaryoutput related to the numberof the key being pressed. Thesimplest version is a 16 -to -4 -line encoder (Fig. 23) This ac-cepts inputs from up to 16keys; one of the 16 input linesis made high when a key ispressed. The circuit producesan output on four lines; theoutput corresponds to one ofthe 4 -bit binary numbers 0000(=Ow) to 1111 (=1510). As mightbe expected, a large number oflogic gates is required to per-form this operation, but thereis plenty of room for these onan IC. To illustrate the princi-ple, Fig. 24 shows the logic ofa 3 -line to 2 -line encoder.Pressing any one of the keys 1to 3 automatically generatesthe binary numbers 01 to 11 onthe output lines. No key is re-quired for zero, since the re-sistors pull all inputs down to0 V when no key is pressed. Anencoder such as that in Fig. 23has additional outputs for pre-venting errors. One of these isa strobe output, which is nor-mally high but which goes low


54 GENERAL INTEREST

Fig. 24

1.

940120 - 111 - 34

when any key is pressed. Thisoutput is connected to a delaysub -circuit which prevents theoutput from the other linespassing to the remainder ofthe circuit until sufficient timehas elapsed for the key state tobecome stabilized. This is aform of debouncing. There isalso a rollover output whichgoes low when two or morekeys are pressed at the sametime, allowing the circuit torecognize and take steps to ig-nore the consequent decodingerror.

The most complex keyboardencoders can accept inputsfrom the 80 or more keys of acomputer keyboard, and in-clude the circuitry for debounc-ing and for rollover avoidance.They may also include a mem-ory so that the most recentkeystrokes are stored if the op-erator occasionally types fasterthan the computer can re-spond.

Keyboard scanningWhen a large number of keyshas to be encoded, we do notprovide each key with an indi-vidual input to the encoder. Weresort to keyboard scanning.There is no dependence on spe-cially wiring -up the keyboardwith diodes or other devices.Scanning is another exampleof software taking over thefunctions of hardware. A typi-cal remote control IC (based onPlessey's Type MV500) isshown in Fig. 25. It uses key-board scanning for a keyboardof 32 keys (though not as manykeys as this need actually beinstalled). The IC has threeoutputs which are currentsources and eight inputs thatare current sinks. The sourcescorrespond to the rows of thekeyboard and the sinks corre-

spond to the columns. Eachsource in turn produces apulse, so scanning the rowsone at a time. As each row isscanned, the sinks are moni-tored to see which one, if any,is receiving a pulse, so scan-ning that row. If a pulse is re-ceived by a sink, it indicatesthat the key being pressed con-nects that source to that sink.This identifies the number ofthe key being pressed. The col-umn decides the two digits atthe extreme right and the rowdecides the three digits at theextreme left. Thus, pressingthe shaded key in the diagramgives the output 01101. The ICcycles rows and columns re-peatedly, producing an appro-priate output whenever a keydepression is detected.

Pulse detectionA remote control transmitter,such as the one referred toabove, produces an output ofcoded pulses depending onwhich control key is pressed.This output is transmitted tothe controlled device, such as aTV set. The electrical pulsesfrom the IC may be convertedto pulses of infra -red (IR) light,or ultrasound, or sent as volt-age levels on a wired connec-tion. We shall have more to sayabout long-distance line trans-mission of digital signals in alater issue but, for the mo-ment, let us look at some of theproblems associated with thereception and recognition ofdigital signals from nearbysource.

A digital signal does notnecessarily consist of a pulse,as such. The essentials of adigital input are that there aretwo distinct levels and there isan almost instantaneouschange of state from one levelto the other. We have alreadydescribed how pressing a keycauses a change in voltagelevel from low to high. A ther-mistor circuit such as that inFig. 26 has an output which isnormally low but which goeshigh when the temperature(perhaps room temperature)rises above a preset level. Thismay provide one of several in-puts to a digital logic systemcontrolling central heating.Note the Schmitt trigger gate,which is intended to give apositive action to the circuit. Itacts as an amplifier, for a verysmall change input voltage

O 0

O 0 1

O I IME=MI0 1 1

MBEINEEMIO 1 0 0 MrlIE=MINI

1 1 1:=MIERIEMIARMOR.'

-11b-040120 - III - 35

A 0 0

B 0 1 0

COLUMNS a =

Fig. 25

around one of its thresholdsproduces a swing in outputvoltage from high to low, or lowto high. The other aspect of theSchmitt trigger action is itshysteresis, described earlier.Once the temperature has ex-ceeded a certain level, it needsto drop several degrees belowthat level before the output re-verts to its original low -tem-perature state. The reverse ap-plies as the temperature falls.This is the equivalent of de -bouncing a switch; it preventsthe room heating from beingswitched on and off for veryshort periods when the tem-perature is hovering aroundthe transition point. Lookingat this from a different point ofview, the trigger circuit, in con-junction with the fact that sig-nificant temperature changesare usually slow, acts as afilter. It ignores short-termvariations in temperature, butresponds to long-term changes.Similar circuits can be used tomonitor other physical quanti-ties such as light (photodiode),

940120 - - 36

Fig. 26

mechanical strain (straingauge), magnetic field (Hall -ef-fect device), and vibration(piezoelectric crystal, micro-phone). In the case of a circuitdesigned for detecting lightlevels, we may need to includea high-pass filter to eliminatethe effects of long-term light-ing changes such as thosebrought about by weather con-ditions or the time of day. Yet,the circuit responds to therapid changes of level pro-duced by arriving pulses. Thehigh-pass filter may need acut-off frequency as low as20Hz so as to eliminate the ef-fects of mains -frequency inter-ference, either electromagneticeffects or, in the case of lightsensors, the fluctuations ofroom lighting, particularlywhere fluorescent tubes are in-stalled.

Summarizing the foregoing,a typical circuit has a sensor,an amplifier and a device tosharpen the response. ASchmitt trigger gate is onlyone way of processing the sig-nal from the sensor. Manyother designs of circuit are de-ployed, using comparators oramplifiers with special charac-teristics. The amplifiers mayalso incorporate a filter ofsome kind. Finally, an inputcircuit needs an interface sothat signal levels within thedetector circuit may be con-verted to those of the logic sys-tem to which it is connected.

A typical infrared detectorcircuit is shown in Fig. 27. Itcould be used for detecting thepulses transmitted from a TV


THE DIGITAL SOLUTION -3 ea5V

TDA81 60

Fig. 27

940120 - III - 37

remote controller (Fig. 25). The sensor isa reverse -biased IR photodiode. The diodeelement is enclosed in a plastic packagewhich permits only IR light to enter. Asmall reverse current passes through thediode; this is very small in the absence ofIR light and increases when a pulse ar-rives. It flows to the IC where it is ampli-fied and causes the output to switch be-tween low and high logic levels. In thecase of remote control, the signal is a se-ries of pulses. The pulses are all of thesame width, so that it is only necessaryfor the circuit to detect the arrival of apulse, not its exact duration. The circuithas to detect only a sudden increase in IRlevel against the continuously changingbackground levels and interference fromother devices such as filament lamps andheaters. It is the duration of the intervalbetween the arrival of one pulse and thatof the next pulse that is used to code thecontrol signal. This is known as pulse po-sition modulation (PPM) and will be de-tailed in a later issue.

A similar circuit is used in a bar codereader. The source of light is a laser beamof red light, which is of high intensity andvery narrow. The high -intensity spot oflight is used to scan across the bars.Since it is laser light, which is monochro-matic, there are no blurring effect owingto differential refraction in lenses and

S N

Fig. 28

940120 - Ill - 38

mirror in the system. The barcode is read by swiping thecode panel across the beam orby scanning a deflectablebeam across the panel. The re-flected light is monitored by adetector circuit. The bars andthe gaps between them are ofdifferent widths. It does notmatter whether the scanningis exactly perpendicular to thearray of bars, nor is the exactspeed of the scan important,for it is the relative lengths of the pulsesand pulse intervals that are decoded.

TONEBURST

HIGH e -A-- - - - - -

LOW

Magnetic sensorFigure 28 illustrates a sensor circuit fordetecting the presence of a ferromagneticobject or a magnet. The IC includes aHall -effect device and an am-plifier whichproduces a binary output compatible withlogic ICs. This sensor has many applica-tions in the control of machines becauseit is able to detect when metal parts (ornon-metal parts bearing a small magnet)are in a certain position. If a magnet isattached to rotary parts and the Hall-efect device is placed so that the magnetsweeps past it at each rotation, the num-ber of pulses generated can be counted. Atiming circuit counts the number ofpulses within a set period of time and thecircuit functions as a tachometer.

The output of a Hall -effect deviceswings sharply up or down when themagnetic field changes in a certain way.For example, IC Type TL170C is sensitiveto field direction. It is switched on (outputgoes logic high) when the field strengthexceeds 25 mT. To switch it off, the fieldmust reverse to become -25 mT. By corn-parision, the TL172C is sensitive to fieldstrength. It is turned on when the fieldstrength exceeds 45 mT, and is turned offwhen the field strength falls below 22 mT.The action shows hysteresis, and is thesame as that of a Schmitt trigger. One ap-plication of this is to make bounce -freekeys. The base of the key contains a Hall -effect device and a small magnet ismounted in the key -top. When the key ispressed, the magnet is brought closer tothe Hall -effect device, which is turned on.There is no making or breaking of con-tacts but just a single transition from lowto high, ideal for input to a logic circuit.

Phase -locked loopIn many environments, there is the diffi-culty of sensing pulses against a noisybackground. Take the detection of lightpulses as an example. The noise may beof the random type, for example, flashesof light or interruptions of light caused byobjects and people moving in the areasurveyed by a light sensor. Or it may beby regular pulses generated by varioussources such as a mains -powered lamp ora remote controller for some other digital

PULSE INTERVAL

Fig. 29

940120 III - 39

circuit, It is usually easy to deal with thesecond type of noise, either by filtering asexplained earlier or by operating differ-ent remote control circuits with differentpulse timings so that each circuit recog-nizes only its own controller. Randomnoise is more difficult to anticipate andignore. The solution is to contrast therandomness by the use of signals thathave a high degree of regularity. Then thedetecting circuit will be most easily ableto distinguish between noise and signal,even if the amplitude of the noise is of thesame order as that of the signal.

A very successful approach to thisproblem is to superimpose the signal(which is very regular in form) on to acarrier signal (which is even more regu-lar). The highly regular modulated signalis more easily detected against randombackground. The carrier signal has ahigher frequency than the digital signaland is 100% modulated by it to give a se-ries of tone bursts instead of a series ofpulses (Fig. 29). The detector circuitlooks for the carrier signal and detectswhether it is present (=pulse) or absent(=interval between pulses).

The carrier signal is detected by aphase -locked loop, a circuit that can betuned to the carrier frequency. A block di-agram of a circuit based on the Type 4046

phase -locked loop IC.is shown in Fig. 30.The input to the circuit comes from thesensor (such as a photodiode or piezoelec-tric vibration sensor) and consists of anominally square wave at the carrier fre-quency, modulated by the digital signal.

Fig. 30

940120 - III - 40



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The PLL has its own local oscillator gen-erating a continuous square -wave signal.Its frequency is controlled by a voltageinput, so it is a voltage -controlled oscilla-tor (VCO). The frequency may be divideddown by a counter, the degree of divisiondepending upon the application. In someapplications, there is no no division, andwe will assume this is the case in this de-scription. At the phase detector stage, theincoming signal is compared with the sig-nal from the VCO. In one form of PLL thephase detector consists simply of an XORgate. If the incoming signal has exactlythe same frequency and phase as the sig-nal from the VCO, the output of the gateis continuously zero. But this is unlikelyto be the case: the signals are more likelyto be out of phase and possibly out of syn-chrony, too. The bigger the difference be-tween the signals, the greater he averageoutput voltage from the phase detector.This voltage is filtered and sent backaround the loop to control the VCO. Theresult of this is that the frequency of theVCO is increased or decreased until itgradually latches on to the frequency ofthe incoming signal, and eventually runsin phase with it. Random noise on thissignal may cause instantaenous changesin the output from the phase detector, butthese are filtered out by being averaged

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over several cycles. Overall, the VCO iskept in step with the incoming signal. Ifthe incoming frequency changes, the VCOtracks the change.

The centre frequency of the VCO ispreset by a suitable choice of capacitorand resistor so that it equals the knownfrequency of the incoming signal (for ex-ample, from a remote controller with itscarrier tuned to a set frequency). TheVCO is thus able to home on and trackthe incoming signal rapidly, and usuallyto ignore signals from controllers operat-ing on different carrier frequencies.

The incoming signal is usually dis-torted in shape with spikes on it owing torandom noise in the environment, but thelocally generated signal from the VCO isa crisp square wave of identical fre-quency. If the incoming signal fades for afew cycles, or is totally masked by aneruption of interference, the VCO contin-ues to oscillate with relatively littlechange in frequency. It is the signal fromthe VCO which is sent to the digital cir-cuit for analysis.

In the foregoing we have looked atsome of the ways in which binary (on -off)information may be detected and fed to adigital circuit. Next month we discusshow analogue information is processed toprepare it for digital analysis.

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58

PARAMETERS OF MMIC WIDEBANDRF AMPLIFIERS

Microwave monolithic integrated circuits (MMICs) are nowfirmly established components in wideband RF amplifiers.These devices offer excellent matching, high gain and afabulous bandwidth at very low cost. This article provides anintroductory overview of MMICs, and discusses their basiccharacteristics.

By G. Kleine

MMICs are drop -in amplifierswhich can be used up to very

high frequencies. Some versionspacked in ceramic enclosures operateup to 30 GHz and higher, while low-cost variants in plastic cases can beused up to about 2 GHz. Since the in-troduction of MMICs about seven yearsago (Ref. 1), the same technology hasalso produced one -chip mixers and os-cillators for SHF applications.Furthermore, electronic switches andattenuation pads are now available asMMICs, which use Gallium -Arsenide(GaAs) technology for the most part.

MMIC basic circuitsAn MMIC requires an absolute mini-mum of external parts to come to life.Figure 1 shows the three supply op-tions for these devices, which are oftenreferred to as gain blocks by theirmanufacturers. The configuration inFig. la is generally recommended foruse with a positive supply voltage, UB.All you have to do is calculate thevalue of resistor R as a function of theMMIC operating voltage, Ud, and theoperating current, Id:

R=(UB-Ud)/Id

To cope with all thermal instability andindividual device tolerances, the sup-ply voltage, UB should be at least 2 Vhigher than the typical operating volt-age, Ud. If that is not possible, the cir-cuit of Fig. lc should be used. Thiswill be reverted to below. The value ofthe choke is uncritical. The function ofthe choke is to decouple the supply re-sistor, R, from the RF signal at theMMIC output. The choke may be omit-ted if the value of R is large with re-spect to the output impedance (whichis usually 50 Q.). In practice, the chokeis not used when R>500 52.

The basic circuit for negative supplyvoltages is shown in Fig. lb. Here, theMMIC output is tied to ground (d.c.-wise, that is) via the choke, so that theground terminals of the MMICs are at-Ud. These two terminals are decou-pled for RF signals by two capacitors.In some cases, a number of capacitorswith different values must be con-nected in parallel to prevent resonanceeffects. Series resistor R is connectedbetween the MMIC's ground terminalsand -UB. Its value is calculated as withthe circuit in Fig. la. The observationsas regards the choke are the same asfor the positive supply variety. Thechoke may not be omitted, however,when a negative supply is used.

When the supply voltage varies by acouple of volts, or when it is less than2 V above the MMIC operating voltage,an active supply as shown in Fig. lcmay be used. The p -n -p transistorforms a constant current source to-gether with resistor RE and the voltagedivider at the base. The MMIC operat-ing current, /d, equals U/RE. The levelof U (see Fig. 1c) is determined by thevoltage divider, and is about 0.7 Vlower than the transistor's base volt-age. A silicon diode, D, is added as athermal compensation for the transis-tor's b -e junction. When U is of theorder of a couple of volts, the diodemay be omitted. As with the two previ-ous supply options, the value of thechoke is uncritical.

MatchingThe input and output matching char-acteristics of MMICs are usually ex-pressed in a VSWR (voltage standingwave ratio) value or a reflection damp-ing value (in dB). The VSWR should beas close as possible to 1 (for instance,1.5), while the reflection dampingshould be as high as possible (for in -

Fig. 1. Power supply options for MMIC RFamplifiers.


PARAMETERS OF MMIC WIDEBAND RF AMPLIFIERS 59

stance, 15 dB). These two values indi-cate the amount of power reflected bythe MMIC input as a result of an im-pedance mismatch. The same goes forthe MMIC output. For cable TV net-works, the reflection damping shouldbe at least 20 dB, which equals aVSWR of 1.2.

Although MMICs are simple to useas gain blocks, special attentionshould be given to the geometry oftheir input and output lines if youwant to ensure that they are properlymatched. As discussed in Ref. 2, 50-51stripline techniques should be appliedin all cases where the input and out-put connection are not very short. Thematching properties are also affectedby the way the MMIC's ground termi-nals are connected. These should besoldered flush on the ground plane.

1 -dB compression pointAll amplifiers may be driven to a cer-tain maximum as regards their outputsignal level. The absolute maximumsignal level that can be achieved is, ob-viously, determined by the supply volt-age. Before that level is reached,however, distortion will occur whichmakes the amplifier useless at outputsignal levels way below that of the sup-ply voltage.

From a certain drive level onwards,saturation will occur in any amplifier,when the output voltage will not rise inproportion with the input voltage anymore. Consequently, the amplifier'slarge -signal gain is lower than thesmall -signal gain. When the input levelis increased beyond the saturationlevel, the output level remains virtuallyconstant. The saturation effects thengive rise to harmonics and distortion,the negative effects of which will be re-verted to below.

The 1 -dB compression point (P1dB) isthe output level at which the theoreti-cally constant gain has dropped by1 dB. Figure 2 shows an example. The1 -dB compression point is foundwhere the output level deviates 1 dBfrom the (theoretically) straight line.The actual value of PidB is about13.7 dBm.

Intermodulation productsand 3rd order interceptpointDistortion occurs in any amplifier,particularly at high drive levels, and isfirst noticed from the presence of har-monics. As illustrated in Fig. 3, anamplifier driven with two frequencies,fi and fi, produces its first harmonicsat 2fi and 2f2. The harmonics have alower level than the wanted signals.The levels of the higher harmonics, 3f,4f, etc. drop rapidly with increasingfrequency, and need not be taken into

Pout[dBm]

+15

+14

+13

+12

+11

Pus tta

+12de

Pin Pout

-1 0 +1 +2 +3 +4 +5 Pin

950025-12 [dBm]

Fig. 2. Graphic representation of the 1 -dBcompression point.

account. The ratios of the harmonicslevels allow you to estimate the degreeof distortion which occurs in the MMICamplifier. The presence of strong odd -numbered harmonics (3f, 5f, etc.) indi-cate that a sine -wave input signal isbeing distorted into a rectangularshaped signal. Time to reduce theinput level!

The two-tone input signal of Fig. 3also produces intermodulation prod-ucts, which are weaker than the har-monics. Intermodulation also occursat relatively high drive levels, and iscaused by non-linear behaviour of theRF amplifier. The IM products are clas-sified according to their 'order', a num-ber obtained from the multiples of thebasic frequencies present in the IMsignal. In the output spectrum, fre-quency lines caused by (nfi±mf2) arereferred to as the (m+n)-order IM prod-uct. In Fig. 3, the second -order IMproduct, fi-Ff2, appears between thefirst two harmonics.

Harmonics and second -order inter -modulation products rarely causeproblems in narrow -band RF ampli-fiers, such as intermediate frequency

0dB

-10dB

-20dB

-30dB

-35dB T I2f1 -f2 t1 f2 2f2 -ft 2ft ft+f2 2f2 f

950025-13

Fig. 3. Intermodulation products caused bynon-linear amplification.

(IF) amplifiers in radios and TV sets. Inwideband amplifiers, however, thesespurious signals are far more trouble-some. Third -order IM products in par-ticular need to be kept as small aspossible because they fall within thesame frequency range as the wantedsignal(s). The third -order IM productsare components 2f1 -2f2 and 2f2 -2f1,which are very close to the two-tonecomponents fi and f2 (Fig. 3). Complexsignals, such as an amplitude -modu-lated TV signal with a sound subcar-rier, consist of a large number ofindividual components. Because of theamplitude modulation, the differencesbetween the levels of the wanted sig-nals and those of the IM productsmust be sufficiently high. The termused to express this parameter is 'in-termodulation distance'. In Fig. 3, ithas a value of 35 dB. In cable TV net-works, the IM distance should be atleast 70 dB for all amplifiers.

Because the effects discussed so farare dependent on the degree to whichthe amplifier is driven, the design of anamplifier forces you to select a devicewhich guarantees the desired third -order intermodulation distance at therequired output level.

In order to obtain a generally validparameter to describe the performanceof an RF amplifier in this respect, it isnecessary to gather the different drivelevels and the respective intermodula-tion distance values into one specificquantity. This is aided by the followingrule of thumb which applies to thedrive range below the 1 -dB compres-sion point: if the wanted signal rises by1 dB, the levels of the third -order in-termodulation products rise by 3 dB.When both the level of the wanted sig-nal and that of the third -order IMproduct are entered into a graph likethe one in Fig. 4 (large drive signalrange assumed), you get two straightlines with different rates of rise. Theone to the left is the gain curve alreadyshown in Fig. 2, which starts to moveinto the horizontal saturation line atthe 1 -dB compression point. The curveto the right represents the level of thethird -order IM products. The qualityparameter mentioned earlier is foundby extending both lines. The theoreti-cal output level at which the wantedsignal and the third -order IM productshave the same level is found where thelines cross. This is called the third -order intercept point, or IP3. In the ex-ample of Fig. 4, the IP3 level is about15.5 dBm.

Although an intercept point mayalso be defined for the second -orderintermodulation products, it is rarelyused because these products fall out-side the relevant channel bandwidth.

When the intercept point is statedas referring to the input, the output in-tercept point may be obtained by sim-


60 COMPONENTS

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MSA 0104 DC -0.8 GHz 17 dB +14 dBm 5.0 V 17 mA HP (Avantek)+1.5 dBm

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MSA 0404 DC -2.5 GHz 8 dB +11.5 dBm +24 dBm 5.3 V 50 mA HP (Avantek)

MSA 0886 DC -3 GHz 25 dB +12.5 dBm +27 dBm 7.8 V 36 mA HP (Avantek)

MSA 0986 0.1 -3 GHz 7 dB +10.5 dBm +26 dBm 7.8 V 35 mA HP (Avantek)

MSA 1105 0.05-1.3 GHz 12 dB +17.5 dBm +30 dBm 5.5 V 60 mA HP (Avantek)

AM -184 10-2000 MHz 20 dB +12.0 dBm +22 dBm 15 V 60 mA M/A-COM

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NE 5205 DC -600 MHz 20 dB +4.0 dBm +17 dBm 6.0 V 24 mA Philips

CA 2820 1 - 520 MHz 30 dB +26.5 dBm +37 dBm 24 V 330 mA Motorola

CA 5800 10-1000 MHz 15 dB +30.0 dBm +40 dBm 28 V 400 mA Motorola

Table 1. Technical data on generally used MMICs from different manufacturers.

ple addition of the nominal gain of thedevice in dB. For example, with refer-ence to Fig. 4, the third -order input in-tercept point is 3 dBm, and the gain is12 dB. It is safe to assume that theoutput intercept point then lies atabout 15 dBm.

The advantage of estimating an am-plifier's performance for a particularapplication with the aid of the IP3 levelis that this figure allows you to calcu-late the desired operating conditions ina simple way. The assumption for thismethod is the (theoretical) fact that thethird -order IM products have the samelevel as the wanted signal if the output -level equals IP3. For example, when thewanted signal is 10 dB lower than theIP3 level, the levels of the third -orderIM products have dropped by 30 dB.Consequently, the third -order IM dis-tance becomes 20 dB. Similarly, keep-ing the wanted signal 20 dB lower thanIP3 results in an IM distance of 40 dB.This method enables both the requiredIP3 for a certain output level as well asthe expected IM distance at a given IP3level to be determined with quite ac-ceptable accuracy.

Practical use: today'sMMICsTo help you understand and use thevalues and parameters mentioned inthe datasheets, Table 1 shows themain technical characteristics oftoday's most popular MMICs.Originally designed by Avantek,MMICs are now available from a num-ber of manufacturers. Especially the

Fig. 4. Graphic representation of the third -order intercept point.

MSA devices from Avantek (nowHewlett Packard) have found wide ac-ceptance with RF designers and radioamateurs. Not surprisingly, a numberof second sources have emerged forthese popular devices.

The table clearly indicates that lowdistortion can be achieved at the costof (relatively) high current consump-tion only. Conversely, all low -currentMMICs have relatively low IP3 values.

The table also lists the main specsof two hybrid amplifier modules fromMotorola, which are used in cable TVmaster amplifiers with a capacity of 30to 40 AM TV channels. These specs areincluded as a reference to comparewith those of MMICs. Clearly, the hy-brids achieve sufficient linearity at

high output levels only at high supplyvoltage levels and high current.

(950025)

References:1. MMICs revolutionize wideband RFamplifier design, Elektor ElectronicsJanuary 19882. Using the MAR -x series of MMICs,Elektor Electronics October 1992.



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DEVELOPMENT SOFTWARE E19.95Develop software on your IBM PC for other Microprocessors, Controllers, Pic's, etc. Software hasfully integrated Text editor, Assembler, Disassembler and Simulator. The simulator displays allregisters along with disassembled code program counter, Condition code register. The user can single

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TEL (OR FAX) 0532 537 507

ACCESSVISA


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OPERATIONAL AMPLIFIERS REVISITED

he operational amplifier (often abbre-viated to op amp) is an extremely sta-

ble, usually direct -coupled, linear amplifieroriginally developed for performing math-ematical operations. Nowadays, it is widelyused in computers, although it is not al-ways realized that this is but one of itsmany applications. It comes in many shapeswith varying specific parameter: one, twoor even four in one enclosure.

An op amp is basically a differentialamplifier typified by two complementary in-puts: an inverting one (-)and a non -in-verting one (+). It tends to hold its inputsat the same potential, and when a differencebetween the two occurs, it produces an out-put that tends to nullify that difference.Its amplification is determined by feedingback part of its output signal to its invert-ing input.

Use as inverting amplifierFigure 1 shows how an op amp may beused to form an inverting amplifier. Theinput signal is applied to the invertinginput via R1. The + input is connected to thereference voltage via R3. The reference volt-age is usually equal to half the supply volt-age. If the supply voltage is symmetrical,the reference potential is zero. This is whyin many op amp circuits this point is at 0 V.

[R1 /1 R2]

R2

Fig. 1.

OV

Feedback in Fig. 1 is effected via R2. Theamplification, a, is calculated from

a =

The relationship between input and outputis shown by the characteristics inFig. 2. Points A, B and C on the x-axis cor-respond to those indicated in Fig. 1.

Since the level of the potential at the-input is always identical to, and is deter-mined by, that at the + input, no voltage vari-ations will be discerned at the - input of aninverting amplifier. This is also evidentfrom the characteristics in Fig. 2, whichshow that both input and output voltage vary,but the potential at B remains constant.

The characteristics also show at aglance that they pertain to an inverting

U..=+

U;=0

amplifier, because as soon as a line con-necting input and output passes through B,the polarity reverses.

Furthermore, they show how the am-plification setting works: the ratio of sectionsA -B and B -C corresponds to that of thevalues of R1 and R2. (A line drawn from Ato C through 0 shows that C is further from0 than A. In other words, the larger B -C, thatis R2, relative to A -B, that is, R1, the higherthe output voltage).

Use as non -inverting amplifierThe circuit in Fig. 3 is identical to that inFig. 1, but the input signal is applied to its+ input. This arrangement has far-reach-ing effects on the characteristics shown inFig. 4. A, the point of origin in Fig. 2, hasbecome a pivot, while the new point of ori-gin is somewhere between A and C. Because

OV

OV

0

R1

R2

Fig. 3.

R2

C

Ui=+

U1=0

Fig. 4.

A = [R2..R1] / R1

U.=+

U.-0

950002 - 14

By J. Markus

R1 R2

ic?

A = - 92 / R1

U..+

U.-0

950002-12

of amplification, the swing of C relative to0 is larger than that of B, but both move inthe same direction. This means that a non -inverting amplifier does not cause polarityreversal, so that input voltage and outputvoltage have the same polarity.

The amplification, a, is

a = (R1+R2)/R1.

This shows that if the values of the re-sistors are the same as those in Fig. 1, theamplification will be greater.

Fig. 2. Use as voltage followerThe circuit in Fig. 5 is not an amplifier inthe true sense of the word, but a voltage fol-lower. In this, the output is connected di-rectly to the inverting input. This means thatthe potential at the output is identical to thatat the - input; whence the name voltage fol-lower. This circuit is comparable to that ofan emitter follower.

Ui = U.950002 - 15

Fig. 5.

Load presented by an op ampThe op amp is no exception to the rule thateach and every circuit presents a load to thepreceding circuit or signal source. In the caseof an op amp, this load depends on the con-figuration of the op amp.

In Fig. 1, generator G is loaded by the se-ries network of R1, R2 and RL (the load re-sistance) to 0 V-see Fig. 6a. Since theinput resistance of the op amp is high com-pared with the values of R1, R2 and RL, ithardly affects the value of the network.This is also true of RL, since its value is in-variably much lower than that of R2. Itmight, therefore, be though that the inputresistance is determined by R1 and R2. Inreality, this is not so, because B is at 0 V(called virtual earth). The circuit maythus be simplified as shown in Fig. 6b. It

OV

Invertinginput

Fig. 6a.

OV

950002 - 16a

'11111111R VVVVI tDU 100(

OPERATIONAL AMPLIFIERS REVISITED 65

is evident that the input resistance is de-termined almost exclusively by R1.

The matter is even simpler in the caseof a non -inverting amplifier: in Fig. 3, theinput signal is loaded by the series net-work of R3 and the (very high) input resis-tance of the op amp. It is evident that thetotal resistance of this network is very high

01/

CIV

Fig. 6b.

OV

950002 - 16h

(in excess of 1 MQ, often as high as 10 Mf2).As far as the input impedance or ampli-

fication of a non -inverting amplifier circuitis concerned, the value of R3 does not seemto matter much. In practice, however, itdoes, because op amps are not as ideal aswe would like them to be. In fact, they causesmall errors which are minimal, however,when the value of R3 is equal to that of theparallel connection of RI and R2-see Fig. 7.

Fig. 7.

Note that, seen from the signal source, R1and R2 are in series, but seen from B thisis not so. Since, invariably, the internal re-sistance of the signal source is negligible rel-ative to R1, the 'free' ends of these re-sistors, seen from B, are at 0 V, that is, theyare in parallel as drawn in Fig. 7. To obtainsymmetrical operation, the value of R3 willthus have to be equal to that of the paral-lel combination.

OV

OV

R1 R2

invertingamplifier

non -invertingamplifier

OffsetSo far we have assumed that the 0 -axis ofthe input signal is at the same level as the0 V line of the op amp. This is not alwaysso, however: for example, if the input sig-nal has a direct voltage component. The op-eration of the op amp is then as illustratedin Fig. 8. This shows that the output (C) isno longer at 0 V, but at a different level.The result of this is that symmetry is lostand that maximum amplification can nolonger be attained. This is because the volt-age swing at one end is much smaller thanthat at the other end. If the amplificationis arranged at maximum notwithstanding,the negative part of the output of an in-verting amplifier will be distorted, becausethe signal can not exceed the lower limit ofthe negative supply line. This difficulty isavoided by correcting the position of the0 -axis of the input signal in such a way thatit is at the same level again as the 0 -axis ofthe op amp. This is done by superimposingit on to a direct voltage, called the offset volt-age. The level of this voltage is determinedempirically with a preset in the circuit.

This in itself raises a further difficulty:the resistance of the preset affects theinput resistance of the op amp and this inturn affects the amplification and the sym-metry. The only way to obviate this diffi-culty is to use a preset with an internal re-sistance of 052, which can be done only byadding a voltage follower to it-see Fig. 5.This has the effect of combining a very highinput impedance with a very low (nearly 0 Q)output impedance. For this reason, the volt-age follower is sometimes called impedancetransformer. It is frequently used with sig-nal sources that must not, or hardly, be

- ideal characteristic

characteristic with--- direct voltage

component

characteristic- - - corrected with

offset

950002-18

loaded by the stage to which it is connected.In Fig. 8, the voltage characteristics

are given relative to the zero line of theop amp. When this line is 'clean', the char-acteristics are horizontal. When the inputsignal has a positive direct -voltage compo-nent, the output voltage of an invertingamplifier will be negative. In the case of anon -inverting amplifier, the output volt-age will be at the same side of the 0 -line asthe undesired direct -voltage component.Both examples in Fig. 8 assume a positivedirect -voltage component; if the componentis negative, the characteristics are simplyturned around.

It is, of course, possible to use an offsetvoltage if for some reason it is required thatthe average output voltage is not on the0 -line. This is achieved by applying theinput signal to the amplifier input and ad-justing the relevant preset until the outputvoltage has the required deviation. Notethat it is almost impossible to do this accu-rately without an oscilloscope.

FinallyWhen experimenting with op amps on thebasis of the foregoing, do consult the rele-vant data sheet( s ). Also, note that notevery op amp is suitable for use as a volt-age follower: some may show a tendency tooscillate. Types like the 741, the 324 (quad),the TL0821 (single) and the TL084 (quad)are eminently suitable. Types like theLM3900 should definitely not be used,since these have current inputs that arequite different from those of most op amps.

[950002]

IF AN---'ADVERT IS IN

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68

INFRARED CONTROLLED DIMMER

These days it is perfectly normal for complex functions of TVand audio equipment to be controlled from the couch orarmchair. Unfortunately, that luxury is not extended to lighting,although dimmers may be available. Time to do a littlecombinatorial thinking. The dimmer circuit discussed hereresponds to commands from the infrared remote controlsupplied with, say, your TV set.

Design by U. Reiser

REMOTDEMOTE control is commonplaceEdays, with telephone an-

swering machines, garage doors andcentral locking systems for cars re-sponding to infrared remote controlssmall enough to fit in your pocket.Although infrared remote controltransmitters and receivers have beenthe subject of a number of previous ar-ticles in this magazine, none so far wasspecifically geared to lights on/off andintensity control. That deficiency ismade good by the present design.

The circuit discussed here is a com-bination of (1) a sensitive infrared re-ceiver responding to signals from RC5compatible remote controls and (2) adimmer for ordinary light bulbs as wellas halogen lamps. The two units maybe fitted into a single case and in-stalled near, for instance, a table lamp.The receiver is easily programmed torespond to one particular button onthe remote control. This button may beone for a rarely used function on the

relevant audio/visual equipment. If anumber of IR controlled dimmers areused, it is, however, worthwhile to usea remote control reserved for that pur-pose only.

Two sub -circuitsThe schematic in Fig. 1 clearly showsthe two sub -circuits that make up theinfrared controlled dimmer. The in-frared receiver is shown to the left ofthe dashed line, and the dimmer cir-cuit, to the right. Since the two arelinked via an optoisolator, it is possibleto locate the receiver at some distancefrom the dimmer, without running intoproblems as regards electrical safety.The two sub -circuits are then con-nected via a short cable. Obviously,the receiver must be able to 'see' thetransmitter, hence the relocation op-tion.

As far as the receiver circuit is con-cerned, since this is based on an ear-

lier design (Ref. 1), its operation willnot be explained in great detail here.However, for those who have not seenthe earlier article, a brief description isgiven.

The infrared signal receiver used isa type IS1U60 from Sharp. Receivedinfrared signals are first amplified in alow -noise input stage and then fedthrough a 38 -kHz bandfilter whichserves to suppress interference. Nextcome a limiter and a demodulator. Thedemodulated signal is available atpin 1 of IC1, and is fed to the decoder.The IS1U60 may be replaced by simi-lar, but not pin -compatible, deviceslike the SFH505A or SFH506-36 fromSiemens. Although these have differ-ent pinnings, they can all be connectedto the board without problems.

The decoder is the familiar SAA3049from Philips Semiconductors. This ICis capable of storing and analysingsignals supplied by the infrared re-ceiver. The RC5 codes contain infor-mation on the system address and thecommand, which are transmitted insuccession. The SAA3049 is pro-grammed to operate in one of twomodes. Here, the 'single -system mode'is used. This is achieved by tying theCA input/output, pin 19, to the posi-tive supply voltage via resistor R5. Inthis mode, the decoder only suppliescommands via its outputs if the re-ceived system address matches theone programmed on pins AO -A4. Inthis way, it is possible to define thetype of transmitter the decoder will re-spond to. The code which belongs tothe button pressed on the remote con-trol appears on outputs A -F.

A jumper, JP1, is available to enableyou to select between RECS80 (pulseposition modulation) and RC5 (biphasemodulation). Normally, RC5 will beused, which is selected with thejumper connected to ground.

The clock frequency is obtainedfrom a 4 -MHz quartz crystal, X1, whichoperates in conjunction with C3, C4and R4. The combination C2 -R3 pro-vides a reset signal at pin 14 when thecircuit is switched on. The supply volt-age is decoupled by R2, C5 and C6. ICIhas its own decoupling network, RI -C1. Five 10-1d2 resistors contained intwo SIL arrays, R9 -R10, ensure that ad-dress inputs AO -A4 are logic high if therelevant jumpers are not fitted.

The received code is applied to theP inputs of comparator IC3, whichcompares the applied levels with thoseat its Q inputs. A pin header and somejumpers allow you to program the codeof the button to which the system is to


INFRARED CONTROLLED DIMMER 69

respond. Output P=Q of IC3 goes low ifthe received code matches the pro-grammed code.

The circuit around T1 and T2 hasbeen added as an extra protectionagainst noise, and to detect the recep-tion of a new command. The CA pin ofIC2 supplies a rectangular signal whena system address is detected. This sig-nal is low for 15 ms, and high for105 ms. Because of network R8 -C7, T2functions as a rectifier, and keeps itscollector terminal low as long as IC2supplies a rectangular wave at pin 19.As soon as this signal disappears, IC3is disabled.

When pin 19 of IC3 goes low, bothLED D2 and the LED in the optoisola-tor light. An optoisolator is used toguarantee complete electrical isolationbetween the IR receiver/decoder andthe lamp dimmer, which is connecteddirectly to the mains. Furthermore, thereceiver/decoder is accommodated ona separate printed circuit board, sothat it need not be co -housed with thedimmer circuit.

The SLB0587 from Siemensarranges everything to do with phaseangle control. This IC is specially de-signed to dim mains -operated (induc-tive) loads. Its internal blockschematic is given in Fig. 2. In addi-tion to the logic which supplies thetrigger pulses, the IC also contains anumber of protection sub -circuits. Forinstance, it checks whether the 'on'time of the triac does not become toolong, depending on the set phaseangle. The IC also checks whether thetriac has actually been switched onafter a trigger pulse. If not, a new trig-ger pulse is applied after 1 ms. After15 trigger faults, the triac is switchedoff. A soft -start circuit is also providedto reduce current surges when theload is switched on. This helps to in-crease the life span of the lamp, and isparticularly important with halogenlamps. The SLB0587 is also capable ofdetecting whether the mains voltagehas disappeared, when more thanthree successive periods do not arrive.If the mains is restored within a sec-ond, the IC does a soft -start, and auto-matically recalls the previously setlamp intensity. If the mains remainsabsent longer than one second, or thesupply voltage drops below 3.6 V, thetriac is disconnected.

Switching, reducing and increasingthe brightness of the load are all con-trolled by applying a logic level topin 6. The exact action depends on thelogic level applied to pin 2, as will bediscussed further on. Since the IC of-fers a fixed phase angle range of 45° to152°, it is a simple matter to derive the5 V supply voltage from the mains. Thevoltage across the triac will always besufficient, even when the load is fullydimmed. The combination D4-C14-R2o

Fig. 1. The circuit diagram of the infra -red remote controlled dimmer consists of two parts:the left-hand side shows a sensitive infra -red receiver, and the right-hand side an intelligentdimmer circuit based on phase angle control.


70 GENERAL INTEREST

ProgrammingInput

OExtension

Input

0 0

0SensorInput

InputControl

Signal Evaluationand Recognition

Types A, B, C

Synchron-isingInput

0-0

iNT-C1

O

SynchronisingSignal

Conditioningand

Triac VoltageSampling

Control Logicfor Timing

S nc

PLL

Brightness StorageStep Counter

(SC)

SC -Status

Clocks

Comparator -0- Trigger PulseOutput Logic

Reset

SafetyTurn -Off

OutputStage

920111 13

TriggerPulse

Output

Fig. 2. Block diagram of the SLB0587 intelligent dimmer integrated circuit from Siemens.

derives a voltage of about 5 V from themains, and is smoothed by C5. DiodeD3 chops off the negative half -periods.The current consumption of theSLB0587 is only 2 mA.

In addition to the external controlinput to which the phototransistor isconnected (pin 6), IC5 also has a sen-sor input which allows the lampbrightness to be controlled with theaid of a touch -key. This sensor, whichtakes the form of a metal plate to-gether with two 4.7-MQ series -con-nected resistors, functions only if thelive' (L) wire is connected to fuse F1.

Of the other components aroundIC5, R18 and C11 determine the re-sponse of the internal PLL. The statusof the triac is monitored via R19, whichalso serves to synchronize the PLL tothe mains frequency. L1 and C16 re-move high -frequency components fromthe signal so that the mains lines re-main reasonably clean, while networkC15 -R21 limit fast voltage transientswhich would otherwise the endangerthe life of the triac. Finally, there istriac Trii, a TIC206D, which switchesthe mains voltage on and off. Diode D5ensures that the gate of the triac is dri-ven with negative pulses only by theSLB0587. Without a heat -sink, thetriac is capable of controlling loads upto about 200 W. At higher powers (upto about 700 W) the device has to befitted wit a small heat -sink.

The control characteristic of theSLB0587 may be described as follows.If the touch -key or the button on theremote control is briefly operated (50-400 ms), the dimmer is switched on oroff. Operating one of these controlslonger than about 400 ms causes adimming cycle to be started. Thelength of a complete cycle (for in-stance, from off to maximum bright-

ness) is about 7.6 s. The touch -key orremote control button is released whenthe desired lamp brightness isreached. Depending on the voltage atpin 2 (which can be defined with theaid of a jumper), there are three modesof operation:

(1). Pin 2 connected to ground. Whenthe dimmer is switched on, thelamp is powered at maximumbrightness. Dimming starts atminimum brightness, and is thencontrolled up and down continu-ously. After releasing the buttonon the control, the dimming 'direc-tion' is the same as with the previ-ous dimming operation.

(2). Pin 2 open -circuited. The IC mem-orizes the set brightness, which iscalled up automatically when thedimmer is switched on again. Thedimming `direction' is reversedeach time the button is released.

(3). Pin 2 connected to the supply volt-age. As with mode (1), the dimmerswitches to maximum brightnesswhen it is powered up. As withmode (2), the dimming 'direction' isreversed each time the button isreleased.

In all three modes, a single button is,therefore, sufficient to dim a lamp aswell as to switch it on and off.

ConstructionThe printed circuit board shown inFig. 3 consists of two sections. Thecomponent allocation corresponds tothe division indicated in the circuit di-agram. After separating the two sec-tions (with the aid of a jig -saw), youcan start mounting the components.Some parts are mounted upright as in-

dicated on the component overlay. Donot forget the wire links on the smallerboard, particularly those under IC2.Also make sure that PCB terminalblock K3 is not taller than Tr1 and Li.For the rest, the construction is allpretty straightforward soldering work.Connector K5 is a three -pin PCBheader which is mounted upside downso that the long pins protrude from theunderside of the board. As illustratedin Fig. 4, the exact connections of theIR sensor depends on the type used(Sharp or Siemens).

The enclosure is a type with amoulded mains plug at one side, and amains socket at the other. The largerboard is fitted on to the bottom plate ofthe case, in such a way that the opto-coupler is above the mains plug. Donot secure the board yet, because themains wiring still needs to be installed.The smaller board is then fitted on topof the optoisolator section of the largerboard with the aid of two 2 -cm longPCB mounting pillars. The boards areinterconnected with three isolatedwires with a length of about 5 cm. Ifthe boards are in position, these wirescross straight from connector K4 to K5.Drill a small hole in the cover for indi-cator LED D2, and a larger hole to en-able the lens of the IR sensor to `see'the transmitted signal. Depending onthe position of this hole, the sensormay have to bent 90°.

If you want to fit the touch controlas well, mount a decorative nail or aminiature wander (`bonona') socketinto the cover. The touch control isconnected to terminal 'S' on the largeboard. If you want to play it absolutelysafe as regards the mains voltage, con-nect resistor R15 directly to the sensor,and use a short length of insulatedwire to connect through to R14 on theboard. In the unfortunate event of thewire coming loose in the case andtouching a part at mains potential,there is always R15 to protect youagainst the risk of an electrical shock.

Finally, install the mains wiring.The earth pin of the plug is connecteddirectly to the earth pin of the socket.Next, the live and neutral pins are con-nected to the centre and outer pin ofthe PCB terminal block, at the side ofthe fuse. The remaining pin and thecentre one are then connected to thelive and neutral pins of the mouldedsocket. Once this wiring is fitted, theboards may be secured in the case.

The circuit is then nearly ready foruse. All that remains to be done is tofit the jumpers and close the case. Alsoprogram the system address of the re-mote control you wish to use (K1), andthe button you wish to use (K2). On K1,an installed jumper represents a '0',while on K2 it represents a '1'. Bothpatterns are set in binary coding. Inmost cases, a TV remote control will be


INFRARED CONTROLLED DIMMER El

Fig. 3. The printed circuit board (available through the Readers Services) consists of two parts, which are separated by cutting.

Resistors:R1 = 47 f2R2 = 2522R3,R6 = 681d2R4 =1MS2R5 = 331(52

R7 = 5k06R8 = 1011/1S2

R9 = 4x10kf2 -array SILR10,R11 = 8x101c52 array SILR12,R20 = 1162R13 = nninR14,R15 = 4M527R16 = 4701d2R17 = 1201d2R18 = 100k0R19 = 1MQ5R21 = 1005/

Capacitors:C1 = 220pF 10V radialC2 = 1pF 63V radialC3,C4 = 27pFC5 = 10pF 25 V radial

111

C6 = 47nFC7 = 22nFC8,C11 = 100nFC9 = 47pF 25V radialC10 = 470pF 25V radialC12 = lOnFC13 = 1000 10V radialC14 -C16 = 100nF 250 VAC (630 VDC)

Inductors:L1 = 300pH 3A

Semiconductors:D1,D5 = 1N4148D2 = low current LED (red)D3 = 1N4007D4 = 5.6 V 0.4 W zener diodeB1 = B80C1500T1,T2 = BC5478Tri1 = TIC206D1C1 = IS1U60 (or SFH506-36, SFH505)1C2 = SAA3049 (Philips)1C3 = 74HC688IC4 = 1110 (or CNY65)

IC5 = SLB0587 (Siemens)106 = 78L05

Miscellaneous:JP1,JP2 = 3 -way pin header withjumperK1 = 10 -way pin header with 5jumpersK2 = 12 -way pin header with 6jumpersK3 = 3 -way PCB terminal block, 7.5mm rasterK4,K5 = 3 -way connector (SIL)X1 = 4 MHz crystalTr1 = mains transformer, sec. 9 V/0.35VA (e.g.. Hahn BV200009)F1 = fuse 3.15 AT + PCB mount holder1 case (with moulded mains plug andsocket)Printed circuit board 940109-1 (seepage 78).


GENERAL INTEREST

D p D09 00000

000

SFH506-36

SFH505A

IS1 U60

K5 4'.6 + .6+07,0 10g2ACZ;00 ;;Agaiii

Q. *---)119 401 It"ae-®42(3.1 NQI`.043i 170-01

940109 12

Fig. 4. The circuit is suitable for use withthree different types of infrared receiver, twofrom Siemens (SFH types) and one fromSharp (IS1 type). These devices are con-nected as shown here.

used, whose system address is 0 (fivejumpers installed on K1) For instance,if you decide to use the 'mute' buttonto control the infrared dimmer, thiscorresponds to address 13 Conse-quently, jumpers have to be fitted onrows 1, 3 and 4 of connector K2 (13=bi-nary 8+4+1). The table opposite showsthe button codes as standardized forRC5 (Philips/Sony) remote controlsFinally, a jumper is fitted in positionJP1 to select the type of infrared codeused (RC5: jumper to ground)

(940109)

Reference:1. General-purpose IR volume control,Elektor Electronics July/August 1994

Address

0

1

2

5

6

8

System component

TV set 1

TV set 2Teletextvideo recorder 1video recorder 2Satellite TV receiver 1

10 Satellite TV receiver 212 Compact Disc/Video player14 Photo CD player16 Audio preamplifier 117 Radio receiver18 Analogue cassette recorder19 Audio preamplifier 220 Compact disc player21 Audio rack or recording apparatus

Common commands for all addressesCommand Description0

1 1

2

3

45

6

7

8

9

1617

1819

22232425

2

3

4

5

6

7

8

9

volume +volume -brightness +brightness -bass +bass -treble +treble -

Fig. 5. Prototype just before final assembly The rear side of the moulded mains socket in thefits in the free space above the dimmer board

26 balance right27 balance left63 system select77 linear function incr78 linear function deer.80 step up81 step down82 menu on83 menu off84 disp AN syst status85 step left86 step right87 acknowledge

Commands for TV 1 and TV2Command Description10 1/2/3 digits 1011 freq./grog./ch./1112

standby13 mute/de-mute14 personal pref15 display20 colour saturation +21 colour saturation -28 contrast +29 contrast -30 search +31 tint/hue -32 chiprog. +33 ch /prog -34 Altem /eh35 1/2 language36 spatial stereo37 stereo/mono38 sleep timer39 tint/hue +40 RF switch41 store/execute/vote42 time43 scan fwd /therem44 decrement46 sec. con/menu47 show clock48 pause

49 erase/correct50 rewind51 go to52 wind53 play54 stop55 record56 external 157 external 259 advance60 TXT sub-mode/1261 sys standby62 crispener70 speech/music79 sound scroll104 PIP size

105 plc scroll106 act on/off107 red

108 green109 yellow110 cyan111 index/white112 next113 previous122 store open/close126 movie expand127 parental access


A

6.00

CACul]

2,00

OSCILLOSCOPE LIVE CHOP Page 0.0046.6 U

4uA.0 0

33.34.0 psec

0.00;

10.0 psec26.6

20.0 nsec

-2.00 50.0 nsec 20.0

-4.000,1 nsec

0.2 nsec13,3

-6.00 0,5 nsec 6.66

-0.001.0 nsec

2,0 nsec0.00

-10.0 5.0 nsec 6.66

J30(psec) 12.00 10.0 nsec

CH2 S20.0 nsec

50.0 KeeFREEZE ONE SHOT MODE CH1 SET

TIME/DIV TIME-MAG. TIME-OUT HYSTERESIS SLOPE 0'1sec

0,2CH 1

PRINT COMMENT READ DISK WRITE DISK DEUIC NGS

A 1 " 1rConnect the HANDYPROBE to the parallel printer portof the PC and start the software Measuring can becarried out at once The HANDYPROBE does not needan external power supply Some technical parameters0.5-400 V softwareselect input range;one input channel;8 bits resolution(overall accuracy 2%1;A complete softwareprogram consisting ofa digitalstorage oscilloscope,spectrum analyzer,voltmeter and atransient recorderis provided.The HANDYPROBE iseminently suitable forservicing andeducational purposes.

The TP5008 is an interface cardthat provides an analogueoutput in addition to two inputchannels. This output incombination with the twoinputs may be used for thesetting up of a completecontrol loop The outputmay also be used as afunction generatorThe TP5008 has aresolution of 8 bitsand a sampling rateof 200,000 samples/sec (200 kHz) The input range may be set to 0.5-20 Vfull-scale deflection. The output range covers 1.25-2.5 V.The TP5008 is fitted with BNC connectors and isdelivered complete with a user manual and softwareSeparately available are 1 1-1 10 probesand 1 100 oscilloscope probes 197

TiePie engineering manufactures a completerange of computer -controlled measuring instrumentsConnecting these units to a PC (MS DOS 3 0 or higher)results in a number of compre-hensive test instruments - oscilloscope;

- voltmeter;- spectrum analyzer;- frequency meter;- transient recorder.

All measured data can be storedon disk or run off for documentation Because of themany trigger possibilities, a variety of signals can bemeasured, while the powerful software enables amultitude of measurements to be carried out in astraightforward manner Application areas includeservice, medical research, automatic test systems,research and development, and education

A A I P

The HANDYSCOPE is connected to the parallel printerport This makes it possible to carry out measurementswith a laptop or notebook PC Because of its highresolution (12 bits), the HANDYSCOPE is a very accurateinstrument The measuring rate is 100,000 samples/secEither of the two channels can be set independentlyover a range of 0 5-20 V (with a 1 10 probe up to 200 V)The advanced software enables many measurements tobe carried out Two probes (switchable 1 1-1 10) areprovided The HANDYSCOPE is constructed as a smalltable model with two BNC connectorsThe length ofthe cablelinking thePC and theHANDYSCOPEis 1 8 m,which can beextendedto 3 8 m

The TP208 is an interface cardwith a measuring speed of2x20 Megasamples/sec(8 bits) Phenomena shorterthan one millionth of asecond can still bemeasured wellThe completely digitizedtriggering ensures verystable triggering withmany triggerpossibilitiesThe TP208 has aninput range of5 mV/div to 20 V/div in 12 steps and an auto calibrationfunction Since both channels may be sampledsimultaneously, phase differences can be measuredvery accurately Even single phenomena can bemeasured since each channel has a32 KByte memory Comprehensivesoftware is provided

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74

GOVERNOR FOR INDUCTION MOTORSDesign by H. Bonekamp

The induction motor may be regarded as practically a constant -speed machine: the difficulty of varying its speed economically

constitutes one of its main disadvantages. This drawback isovercome by the circuit described here: it enables the

speed to be lowered in small steps.

.C. motors have the great advantagesf being relatively inexpensive and

very reliable. Induction motors in particularare very robust and therefore used inmany domestic appliances such as wash-ing machines, vacuum cleaners, waterpumps, and others.

In an induction motor, the higher thespeed of the rotor, the lower is the speedof the rotating field relative to the rotorwinding and the smaller is the e.m.f. gen-erated in the latter. Were the speed of therotor to attain the synchronous value, therotor conductors would be stationary rel-ative to the rotating flux. There wouldthen be no e.m.f. and no current in therotor conductors and consequently no

torque on the rotor. Thus, the rotor couldnot continue rotating at synchronousspeed. As the rotor speed falls more andmore below the synchronous speed, thevalues of the rotor e.m.f. and current,and therefore of the torque, would con-tinue to increase until the latter is equalto that required by the rotor losses andby any load there may be on the motor.

The speed of the rotor relative to thatof the rotating flux is called the slip. Fortorques varying between zero and thefull -load value, the slip is practically pro-portional to the torque. It is usual to ex-press the slip either as a per -unit or frac-tional value or as a percentage of the syn-chronous speed:

per -unit slip = (rti-ni.)/ ni ,

and

percentage slip = (nr-nr)/ ni x 100 ,

where n1 is the synchronous speed and

R3

T1

P1

R4

U

47k

C1

7 6

11

10

9 N

RX/CX CXR 5

111

ICib

2xBSX20

C2MIMo117n

IC1 = 74HC221

C3

JP2 120n

CTRDIV10/DEC

1J 1

IC2 21214

143

7

L10

13 104

5

1 3 .s%%

14 Cr.

tits'515

CT -0 67

41:3\

774HCT4017 8

R5 119

s12CT?5

R6

00

C4120n

15 114

RX/CX CX

1n

IC1a

R2

BSX20

B

A2

100k

7805

6 ic3C6 C

IC2 IC1TOOn

10V

R1

100k

5

D1

Mop

R7 F1

II

L1

40pH3A I

4

13 A2

R8

ToTIC216M Al

\ I

2A T

z

Tri1

,

-1

R9

C9

K1

7117n630V 0 S

B40C1500

TO On

sy ®

TOO 01125V

B1

rn

T

O

O

940095-11

L

N

Fig. 1. Circuit diagram of the induction motor governor.


GOVERNOR FOR INDUCTION MOTORS

Frequency spectrum of signal with reduced frequency

_T2

T24CT2

940095 - 12

The output signal of the governor can be dissected by Fourier analysis. In thefollowing analysis the frequency -reduction factor is k (which in the presentdesign may have a value of 3, 5, 7 or 9).

The signal is

or

t = 4

it=0

an cos' nt + b sinT

u(t)=I{ancosr2=-0

2 214 nt) + b. sink

wheref=fak and T= kTo.Since the signal is shift -symmetrical, u(t) -n(t-2/)1, It consist of sinusoidal

as well as cosinusoidal voltages. This symmetry makes the computation of thecomponents much simpler, since integration over a half period is all that isneeded. Since over a full period the signal, as far as area is concerned, is thesame above and below the x-axis, the direct voltage component is zero.

Components an and br, are

irk= U MT Jo

From these expressions the spectrum of the signal reducedcalculated.The amplitude spectrum is

or

4U k

rc k2 nOs

n

2k

can U/k (n k and n = °cid)

The phase spectrum is

(n<>k and n= odd

eirls

As an illustration of the above (for those who do not like too many calculations),the amplitude of the computed frequency components for a reduction factor of 3is shown in Fig. 2.

nr is the rotor speed. Note that the syn-chronous speed =f/p, where fis the fre-quency of the applied voltage (mains) andp is the number of pairs of poles of the sta-tor.

The value of the slip at full load variesfrom about 6% for small motors to about2% for large machines. This shows that,as already stated, the induction motor ispractically a constant -speed machine.

Governing the speedSince the speed of the motor dependsprimarily on the frequency of the appliedvoltage (normally the mains voltage), itis readily governed by altering the fre-quency. This is not so simple, however,because the mains frequency is interna-tionally agreed to be 50 Hz (Europe andmost parts of the world, except the USAand Canada where it is 60 Hz). Beforethe upsurge of electronics, complex tech-niques (such as the Ward -Leonard circuitfor 3 -phase motors) were developed togovern the speed of a. c. motors. With theaid of electronics, however, it becomes farless complex. The present circuit enablesthe frequency to be lowered as desired bya factor 1/2,1/3, 1/5, 1/7 or 1/9. Greaterprecision is not necessary since thespeed varies in any case as a functionof the load. The factor 1/2 should betreated with some circumspection sinceduring tests by the designer some motorsdid not respond well to this reduction.

The circuit diagram of the governor isshown in Fig. 1. The circuit uses stan-dard, inexpensive components. The mainsas well as the motor is connected to K1.The mains voltage is reduced by resistorsR1 and R2 and then applied to transistorsT1 and T2. Transistor T1 is on during thepositive half period of this voltage and T2during the negative half. The instant atwhich the transistors begin to conduct de-termines the width of the pulse at pin 9of IC lb. This instant depends to a largeextent on the values of R1 and R2. In the

Fig. 2. Amplitude vs motor speed of thefrequency components generated when

the reduction factor is 3.


76 GENERAL INTEREST

present design, these values are low, butthe transistors are fast switching types.This results in narrow, positive pulses withsteep edges that occur exactly at the zerocrossing point.

These pulses, which are synchronouswith the mains frequency, trigger mono -stable IC 1b. This is not retriggerable andits mono time is set to just below 10 mswith P1. This arrangement ensures thatspurious pulses can not, or hardly, enterthe circuit. In fact, this can happen onlywhen the monostable is inactive, whichis when the mains is going through itszero crossing. An RC filter can not beused for the suppression of spuriouspulses because this would create phaseshifts that would be more troublesomethan these pulses. As it is, the circuitprovides clean trigger pulses at a fre-quency of 100 Hz at pin 5 of IC lb.

The mains frequency can be madevariable by a special arrangement, hereprovided by IC2. In this arrangement,whole periods of the mains voltage are sup-pressed regularly. This results in a lowermains frequency - see the Fourier ana-lysis in the box. on the previous page.In this box, the composition of the sig-nal is derived for the reduction factors usedwith the exception of 1/2. Table 1 showshow the periods of the sine wave are sup-pressed. A + indicates that the positivehalf of a period is applied to the motor anda - that the negative half is applied to themotor; a 0 indicates that the motor is notconnected to the mains.

Circuit IC2 counts the incoming clockpulses. After a reset, output Qo is active,after one clock pulse, Q1, and so on.Assume that rotary switch S1 is in posi-tion 1. Every time a trigger pulse arrives,it is applied to the B input of IC ia via Si,.It also arrives at the reset input of IC2 viadelay network R5 -C2. This delay is nec-essary to ensure that the signal is appliedto the monostable during thold This isactually of importance only when the ro-tary switch is in positions 2-6. At the in-stant that a pulse arrives at the B inputof IC la, the monostable is triggered. ItsQ output is then high for about 8 ms,which causes triac Trli to conduct. At thesame time D1 lights. Because of the ig-nition pulse, the motor is connected tothe mains for the instantaneous half pe-riod. Once the triac has fired, it remainson until the current through it dropsbelow the hold level. In practice thismeans that, owing to the lagging cur-rent, the triac remains on for a short in-stant after the mains has gone througha zero crossing.

With Slin position 1, all trigger pulsesare passed on, so that the triac is on per-manently and the motor runs at maxi-mum speed. Network R9 -L1 -C9 suppressesany spurious pulses and prevents any like-lihood of the triac going into spontane-nous conduction.

When S1 is in positions 3-6, the num-ber of clock pulses, that is, half periods,

nnnn

Fig. 3. Printed -circuit board for the induction motor governor.

Fig. 4. Completed prototype of the governor.


GOVERNOR FOR INDUCTION MOTORS

that needs to be received before the triacbegins to conduct, is 2, 4, 6 or 8 re-spectively. Position 2 of SI is a special one.Only in that position does the secondwafer of the switch have a function. Thisconsists of connecting C3 and C4 in par-allel which results in a lenghtening ofthe output pulse from 8 ms to 16 ms. Inpractice, this means that whole, alternateperiods of the mains voltage are appliedto the motor. During tests on prototypes,it was found that some motors do notfunction properly in this situation.Therefore, jumpers Jp1 and Jp2 havebeen provided to disable this setting ofthe switch. When Jp2 is closed and Jp1open, and C3 removed, positions 1 and2 of S1 are identical. The motor thenrunds at full speed.

Power for the circuit is provided bytransformer Tr1, bridge rectifier Bi andvoltage regulator IC3. Note that the groundconnections of the circuit must NOT belinked to mains earth, since they areconnected to the Neutral line.

ConstructionThe circuit is intended to be built on theprinted -circuit board shown in Fig. 3.Populating this is straightforward, butnote that the triac must be fitted on a heatsink via a ceramic washer.

Since parts of the circuit are linked di-rectly to the mains, the unit must be fit-ted in a synthetic fibre case (plastic, ABS).It is strongly recommended to connect themotor permanently to the governor (K1).In many applications, this is in any casethe most convenient. The photo of Fig. 4shows how this is all accomplished.

The red or brown wire of the mainslead must be connected to pin L(ive) andthe blue or black wire to N(eutral). Asstated before, the ground of the circuit mustNOT be connected to mains earth (E). Themotor must be connected between L andS(witched). A double -pole mains switchwith integral neon indicator is recom-mended.

Do not connect the motor to the cir-cuit before this has been set up correctly.This is to prevent direct current flowingthrough the motor, which does not do itany good.

Setting up the circuit is done with theaid of the LED on the board. Note thatthis diode MUST be fitted on the board andNOT on the enclosure, since it is con-nected to the mains and its colouredplastic lens does NOT provide sufficientprotection.

Set S1 to position 1 and turn P1 fromone end of its travel to the other. At somepoint, the LED will turn from flashing tolighting permanently. The preset shouldbe set a little past that position. In switchpositions 2-6 the LED will always flash,but at a rate that is different for each po-sition.

Finally, connect the motor to the cir-cuit and close the case.

There is a very small risk that themotor you are using is not suitable for usewith the present governor. This mani-fests itself by the motor getting very hot.This is caused by the core becoming sat-urated, which results in very high cur-rents. It is not possible to say beforehandwhether a motor is suitable or not, but,as already stated, the risk of it happen-ing is very small, indeed.

Parts list

Resistors:R1 R4 = 100 k52R5= 10 kS1R7 = 1 Ii52R8 = 560 52R9= 100 Q1'1= 47 kS2 preset

Capacitors:C1, C3, C4 = 120 nFC2 = 47 nFC5 = 1000 pF, 25 V, radialC6= 10 pF, 10VC7, C8 = 100 nFC9 = 47 nF, 630 V

Inductors:L1 = 40 pH, 3 A

Semiconductors:D1 = LED, high efficiencyB1 = B40C1500 bridge rectifierT1, T2 = BSX20Tril = TIC216M

Integrated circuits:ICI = 74HC221IC2 = 74HC4017IC3 = 7805

Miscellaneous:Jp1, Jp2 = jumper (wire bridge)K1 = 3 -way terminal strip, pitch 7.5 mm

= 2 -pole, 6 -way rotary switchS2 = single -pole, single -throw switch with

integral neon lampTr1 = mains transformer with 9 V, 1.5 A

secondary, e.g. Velleman 1090018M(from Maplin)

F1 = fuse holder for PCB mounting with2 A slow fuse

1 off heat sink for Tri120 K W-11 off non-metal enclosure 75x126x53 mm

t/n 1 1/2 1/3 1/5 1/7 1/9 (3x5x21/16 in)PCB Order no. 940095-1

0 + + + + + + 194009511 - 0 0 0 02 + 0 0 0 0 03 - 0 0 0 04 + + 0 0 0 05 0 0 06 + 0 + 0 0 07 - 0 0 0 08 + + 0 0 0 09 - 0 0 -0 + 0 0 + 0 01 0 0 0 0 02 + + + 0 0 03 - 0 0 0 04 + 0 0 0 + 05 0 0 06 + + 0 0 0 07 0 0 0 08 + 0 + 0 0 +9 0 0 0 0 0

Table 1. Illustrating how the half sinusoidal periods are switchedas a function of the delay.


78 The publishers reserve the right to change prices without prior notification. Prices shown in this issue supersede those in previous issues. E. & 0.E.

READERS SERVICESExcept in the USA and Canada, all orders, except for sub-scriptions and past issues (for which see below), must besent BY POST to our Dorchester office using the appropriateform opposite. Please note that we can not deal with PER-SONAL CALLERS, as no stock is carried at the editorial andadministrative office.Readers in the USA and Canada should send orders, exceptfor subscriptions (for which see below), to Old ColonySound Lab, Peterborough NH, whose full address is given onthe order form opposite. Please include shipping cost ac-cording to total order value. For surface delivery in the USA,if order is less than $50, include $3; $50+, $4. For Canadasurface, if less than US$50, include US$5; US$50+,

US$7.50. For air or other deliveries, please inquire. Pleaseallow 4-6 weeks for delivery.All other customers must add postage and packing chargesfor orders up to £25.00 as follows: UK and Eire £1.95; sur-face mail outside UK £2.45; Europe (airmail) £2.95; outsideEurope (airmail) £3.70. For orders over £25.00, but not ex-ceeding £100.00, these p&p charges should be doubled. Fororders over £100.00 in value, p&p charges will be advised.

SUBSCRIPTIONS & PAST ISSUES

Subscriptions and past issues, if available, should be or-dered from Worldwide Subscription Service Ltd, Unit 4,Gibbs Reed Farm, Pashley Road, TICEHURST TN5 7HE,England. For subscriptions, use the order form on the oppo-site page.Prices of past issues (except July/August and December), in-cluding postage for single copies, are £2.70 (UK and Eire);£3.00 (surface mail outside UK); £3.20 (air mail Europe);£3.95 (airmail outside Europe). Prices of past July/Augustand December issues, including postage for single copies,are £3.75 (UK); £4.00 (surface mail outside UK); £4.25 (air-mail Europe); and £5.00 (airmail outside Europe).

PAST ARTICLES

Photocopies of past articles are only available in combina-tion with the associated printed circuit board (see ProductOverview). The price of the photocopy is that of a past issue,which is sent in the first instance. If the relevant past issue isno longer available, you will receive a photocopy. Pleasestate 'plus photocopies' when ordering a printed circuitboard using the order form opposite.We regret that photocopies can not be supplied (1) sepa-rately, (2) if the relevant article does not describe a project ofwhich the printed circuit board is still available.

COMPONENTS

Components for projects appearing in Elektor Electronics areusually available from appropriate advertisers in this maga-zine. If difficulties in the supply of components are envis-aged, a source will normally be advised in the article. It

should be noted that the source(s) given is (are) not exclu-sive - other suppliers may also be able to help.

BOOKS

For book availability, see advertisement on page 51.

SLIPCASEElektor Electronics slipcase £2.95 $6.00

FRONT PANEL FOILS

PROJECT No. Price Price(£) (US$)

4MB printer buffer card 920009-F 8.25 16.50LC meter 920012-F 11.45 22.90Guitar tuner 920033-F 8.80 17.60NICAM decoder 920035-F 8.25 16.5012VDC to 240VAC inverter 920038-F 16.15 32.30Audio DAC 920063-F 10.00 20.00Digital audio/visual system 920022-F1 10.00 20.00

920022-F2 19.40 38.80920022-F3 28.80 57.60

1.2 GHz multifunctionfrequency meter 920095-F 13.80 27.60U24006 NiCd battery charger 920098-F 8.75 17.50Workbench PSU 930033-F 17.00 34.00Inexpensive phase meter 930046-F 17.25 34.50AF rms voltmeter 930108-F 17.25 34.50

PROJECT No. Price

(E)

Price

(US$)

EPROMS / PALS / GALS / CONTROLLERS

Multi -purpose Z80 card:BIOS (1 x EPROM 27128) 6121 15.30 30.60

1.2 GHz multifunctionfrequency meter(1 x 27C256) 6141 11.45 22.90

Digital audio/visual system(1 x 27C256) 6171 10.30 20.60

TV test pattern generator(1 x 27256) 6151 13.00 26.00

DiAV system. Package:1 x 27512; 2 x GAL; 1 xfloppy disk (MSDOS) 6181 30.50 61.00

PAL test pattern generator(1 x GAL 20V8-25) 6211 9.40 18.60

800535 assembler course(1 x EMON52 EPROM and1 x disk 1811) 6221 17.05 34.10

Watt-hour meter (1 x 27256) 6241 10.00 20.00

Four fold DAC (1 x GAL) 6251 10.75 21.50

Multipurpose display decoder(1 x 2764) 6261 11.50 23.00

Telephone -controlled switch

(1 x 2764) 6271 14.50 29.00

Relative humidity meter (1 x 2764) 6301 14.50 29.00

535 card with EPROM emulator(1 x PAL and 1 x GAL) 6311 26.00 52.00

Copybit eliminator (1 x GAL 16V8and 1 x MACH110) 6321 42.25 84.50

RDS decoder (1 x 27C64) 6331 14.50 29.00

I2C tester (1 x GAL 6001) 6341 30.75 61.50

Mains signalling system (1 x 27C64) 6371 13.25 26.50

8751 programmer (1 x 8751) 7061 46.40 92.80

Microcontroller NiCd charger(1 x ST62E15) 7071 10.00 20.00

Maxi micro clock (clock) 7081 11.50 23.00

Maxi micro clock (darkroom timer) 7091 11.50 23.00

Maxi micro clock (cooking timer) 7101 11.50 23.00

Mini micro clock (clock) 7111 11.50 23.00

Mini micro clock (darkroom timer) 7121 11.50 23.00

Mini micro clock (cooking timer) 7131 11.50 23.00

VHF/UHF TV tuner (1 x 87C51) 7141 25.75 51.50Microntroller-driven UART(1 x ST62T10) 7151 17.25 34.50

PIC programmer (1 x PIC17C42and 1 x disk) 7161 52.75 105.50

MIDI swell pedal (1 x 27C64) 946635-1 13.75 27.50

P.O.S.T. diagnostic card (PIC-1)946639-1 11.00 22.00

(PIC-2)946639-2 13.00 26.00

1 -to -3 -phase converter (GAL) 946640-1 12.25 24.50(EPROM) 946640-2 15.75 31.50

Solid-state disk (1 x 27256) 946641-1 23.50 47.00TV line monitor (1 x PIC16C54) 946643-1 20.25 40.50

DISKETTES

GAL programmer (3 disks; upgrade;see June 1993 issue) 1701 11.15 22.30Multi -purpose Z80 card 1711 7.65 15.30Fuzzy Control One 1721 7.75 15.50Pascal library for MMC 1751 9.70 19.40

Speech/sound memory 1771 7.65 15.30PC -aided transistor tester 1781 7.50 15.00

IR receiver and DTMF decoderfor 80C32 SBC 1791 9.00 18.00

800535 assembler course 1811 8.80 17.60

I2C opto/relay card 1821 7.65 15.30Video digitizer for PCs 1831 14.50 29.00GAL programmer for Amiga 1841 11.00 22.00

I2C alphanumerical display 1851 8.50 17.00Philips preamplifier 1861 8.50 17.00

GAL programmer (excl. OpalJr. disks) 1881 10.75 21.50Precision clock for PCs 1871 8.50 17.00X2404 -to -8751 interfacing 1891 8.50 17.00RC5 software emulation 1901 10.75 21.50Mains signalling system 1911 9.75 19.50SIM - an 8051 simulator 1931 34.25 68.50800535 SBC extension 1941 9.75 19.50Small loop antennas 1951 10.75 21.50800535 SBC I2C display 946197-1 9.75 19.50PIC programming course 946196-1 9.75 19.50RC5 transmitter with 800535 946199-1 9.75 19.50Debugging 8031/8051 micro -controller systems 946203-1 11.50 23.00ispStarter kit from Lattice 946204-1 9.75 19.50

PROJECT No Price Price(£) (US$)

PRINTED CIRCUIT BOARDS

Printed circuit boards whose order number is followed by aC are only available in combination with the associated soft-ware item, and can not be supplied separately. The indicatedprice includes the software.

FEBRUARY 1995

MIDI multiplexorAutomatic lighting timerInfrared dimmerLight -effects generatorUpgrade your car batterychargerSurround sound processorInduction motor governor

930101

940098-1940109-1940100-1

940111-1950012-1940095-1

15.0010.75

9.75

6.50

7.0018.75

7.50

30.0021.5019.50

13.00

14.00

37.5015.00

JANUARY 1995Mini Audio DAC 940099-1 14.75 29.50

1 -to -3 -phase converter (incl.GAL & EPROM 946640-1 and -2) 940077-C 52.75 105.50P.O.S.T. diagnostic card (incl.GALs 946639-1 and -2) 950008-C 29.25 58.50

Self -loading EEPROM type

X88C64 SLIC 940116-1 8.25 16.50

Debugging 8031/8051 micro -controller systems (incl. disk946203-1) 940117-C 15.00 30.00

Quasi -analogue clockwork 930024 37.25 74.50

DECEMBER 1994

In -car audio amplifier (3) 940078-2 30.25 60.50

RF immune power supply 940054-1 9.00 18.00

ispStarter kit from Lattice 940093-C 21.50 43.00

Proximity detector 940108 Not available

30m QRP CW transmitter 944020 Not available

Temperature. protection forhigh -power resistive loads 944014 Not available

Electret microphone fortelephone mouthpiece 944003 Not available

Current probe 944093 Not availableStand-alone copybit eliminator 944052 Not available

NOVEMBER 1994Single -wire communication 940055-1 4.00 8.00

In -car audio amplifier (2) 940078-2 30.25 60.50

Solid-state disk (incl.EPROM 946641-1) 940085-C 47.50 95.00

Simple capacitance meter 940091-1 10.00 20.00

OCTOBER 1994

Motive -battery chargerIntegrated AF amplifier

Tester for IR remote controlIn -car audio amplifier (1)TV line monitor (incl.PIC 946643-1)

SEPTEMBER 1994

Switchable a.c. supplyAnemometer & flow meterCompact frequency meterRevolution counter

940083-1

936062-1936062-2940084-1940078-1

7.25

9.5028.25

6.5014.00

14.5019.00

56.5013.00

28.00

940065-C 26.25 52.50

934004 6.50 13.00

940017 6.25 12.50

940051-1 9.00 18.00940045-1 6.00 12.00940068-1 5.50 11.00

JULY/AUGUST 1994General purpose IR volumecontrol 930099 9.00 18.00

IR controlled switch 936066 9.75 19.50MIDI swell pedal (incl.EPROM 946635-1) 940019-C 26.75 53.50Charge meter 940033 5.75 11.50Water softener 944011-1 6.00 12.00Joystick -to -mouse adaptor 944040-1 7.00 14.00Discrete preamplifier 944063-1 8.50 17.00Centronics I/O interface 944067-1 8.75 17.5080C451 controller board 944069-1 15.00 30.00Robust AF power amp 944075-1 9.75 19.50PC over -temperature alarm 944076-1 4.25 8.501-4 MByte SIMM adaptor 944094-1 15.50 31.00Optical doorbell 944080-1 6.25 12.50PIC experimenting board 944105-1 17.75 35.50RC5 transmitter with 800535(incl. disk 946199-1) 944106-C 13.00 26.00

A list of all PCBs, software products and front panels available through the Readers Services IS published In the 1March, June, September and December issues of Elektor Electronics


xr

79

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80

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COPYRIGHTAll drawings, photographs, articles, printed -circuit boards, EPROMS, and cassettes publishedin our books or magazines (other than in third -party advertisements) are copyright and maynot be reproduced or transmitted in any formor by any means, including photocopying andrecording, in whole or in part, without the priorpermission of Elektor Electronics (Publishing)in writing. Such written permission must alsobe obtained before any part of these publica-tions is stored in a retrieval system of any na-ture.

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February 1995J


81

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Etektor Electronics (Publishing) reservethe right to refuse advertisements withoutgiving reasons or without returning them,

FOR SALE. ROM emulator by GreenhillSystems, 2716 to 27256 via printer port. Asnew, manual. £35. Phone (01322) 350 205.

FOR SALE. PIC programmer (ElektorElectronics, March 1994) £100.00 o.n.o..Please ring Mike Mee in New Zealand +6403 7500 016 (mornings GMT).

FOR SALE. Sage Supermos, one module. Caninclude two 500 VA PSUs and four 68000 pFcapaciors. Phone John Turner on (01278)652 641.

IFAN ADVERTIS IN PRINT,

IS ITPROPER?Most advertisements are

perfectly proper. A few are not.The Advertising Standards

Authority not only monitorsover 850 advertisements everymonth, it ensures compliancewith the rules in the strictCode of Advertising Practice.

So when you questionan advertiser, they have toanswer to us.

To find out more about therole of the ASA. please write toAdvertising Standards

Authority,Dept X, Brook House.

Torrington Place,London WCIE

AThis spare Is donated In the Interestsof high standards In advertisements.

WANTED. Manual for Rohde & SchwarzLRU610D Inductance meter. Loan/purchse;reasonable costs met. Please write to P.Redway, 169 Ballards Walk, Basildon, EssexSS15 5JU.

FOR SALE. Datac PM160 panel printers.New. Par?ser I/F 24 ch. wide. Multimode. Fulldata. RR £125; my price £25. Phone Mrd'Oliveira on (01942) 893 888.

FOR SALE. Thandar SC110A portable scope,£125. Also Fluke 87 true-rms multimeter,£125. Both in Al condition. Phone (0181)423 2224.

FOR SALE. RF Signal generator, PrecisionGold, still boxed, £45. Also Marconi univer-sal brridge TF2700, solid-state, with manual,£25. Phone (01272) 407 599 (evenings).

FOR SALE. Oscilloscope Farnell DTV60, 3 -channel, 8 -trace, 60 MHz, with manual, probesand case. Current model, fabulous condition,£365. Phone Peter on (01272) 407 599.

WANTED. Formant information or similarsynthesizer OTA, VCO circuit diagram, etc.Also UA726C or equivalenmt. Buy for cashor swap. Phone Chris on (01235) 534 152.

FOR SALE. HF, VHF satellite communicationequipment of marine. Write to T. Dasan,FA111 Alembic Colony, Baroda-3, Gujarat,India.

WANTED. Data sheet for EEPROM MN010.Cash waiting. Phone Mr Smith on (0191)385 2316.

Send this coupon toElektor Electronics (Publishing)

P.O. Box 1414Dorchester DT2 8YH

England

B ock capitals please - one character to each box

ELEKTOR ELECTRONICS 02/95

Name and address MUST be given

WANTED. Circuit for active tone controls forpreamp for guitar amp. Bass, middle & treble;all ±21 dB. Also presence control. PhoneMr Cropley on (01202) 731 962.

Books from Elektor Electronics (Publishing)

The following books are currently available:How to build your own Electronic Test Instruments £15.95 $29.50Short course 8051/8032 Microcontrollers and assembler £9.95 $18.50SMT Projects £ 9.95 $18.50301 Circuits £9.95 $18.50302 Circuits £9.95 $18.50303 Circuits £10.95 $20.25304 Circuits £12.95 $23.95305 Circuits £14.95 $27.70Microprocessor Data Book f10.95 $20.25Data Sheet Book 2 £9.95 $18.50Data Book 3: Peripheral Chips £10.95 $20.25Data Book 4: Peripheral Chips £10.95 $20.25Data Book 5: Application Notes £10.95 $20.25All prices are exclusive of p&p, for which see page 78 (top 1st column)

How to order:UK and Overseas private customers (NOTin USA and Canada) from:Elektor Electronics (Publishing)PO Box 1414 Dorchester, England DT2 8YHTelephone (0305) 250 995Fax: (0305) 250 996

UK and Overseas bookshops, schools,colleges, universities and bulk orders

(NOT in USA and Canada) from:Gazelle Book Services LtdFalcon House, Queen Square, Lancaster,England LA1 1RNTelephone (0524) 68765Fax: (0524) 63232

USA and Canada ONLY from:Old Colony Sound - please see order formon page 79 for details


82

ELEKTOR ELECTRONICS is available from, among others:CRICKLEWOOD D.P. HOBBS (NORWICH) BEBEK ELECTRONICS TABACCARIA BRITANICA

ELECTRONICS LIMITED LTD Hirsimetsantie 26 Praca do Duque da40 Cricklewood Broadway, Electronic component SF -15200 Lahti 11 Terceira 19

London NW2 3ET specialists. Amateur radio Finland 1107 Lisboa, PortugalTelephone 0181 450 0995 equipment. Telephone (18) 33 99 46 Telephone 932 4752

Fax 0181 208 1441 13 St. Benedict Street,Norwich NR2 4PE,

Telephone 01603 615786 HELMHOLT ELEKTRONIK MK KNJIGARNAGREENWELD Farvevej 2 Slovenska 2927 Park Road DK-7600 Struer, Denmark Ljubljana

Southampton SO1 3TB OMNI ELECTRONICS Telephone 97 85 26 11 SloveniaEngland

Telephone (01703) 236 363Stock a wide range of

electronic components.Telephone 061 150 196

Fax (01703) 236 307 174 Dalkeith Road,Edinburgh EH16 5DX,

Telephone 0131 667 2611

RCE ELECTRONICCENTRE

Boulevarden 34TECHNICAL BOOKS &

MAGAZINESL.P. HANNEY DK-9000 Aalborg, Denmark 289-299 Swanston Street

Your electronic component Telephone 98 16 07 10 Melbourne, Australia 3000specialist for AAGE NIELSEN Telephone 663 3951

Avon, Wilts & Somerset. 1 Sortedam Dosseringen77 Lower Bristol Road,

Bath, Avon,DK-2200 Copenhagen,

Denmark,VEJLE RC ELEKTRONIK

Sdr Brogade 42 INEL Co.Telephone 01225 424811 Telephone 01 39 30 10 P 0 Box 332 P.O. Box 1397

Fax 031 39 05 02 DK-7100 Vejle, Denmark JL. Hariang Banga No. 3Telephone 75 83 25 33 Bandung 40116

Indonesia

Advertising Standards AuthorityBadger BoardsB H SystemsB K ElectronicsBull ElectricalC -I ElectronicsCricklewood ElectronicsCrossware ProductsDisplay ElectronicsElectromailElektor ElectronicsESR Electronic ComponentsExpress ComponentsHart Electronic KitsInstrutekLabcenterMaplin Electronic SuppliesMicroAmpsMicro CallMorrison MicrosNiche SoftwareNumber One Systems LtdPico Technology LtdPOWERwareP S ServicesRobinson MarshallSmart CommunicationsSpeaker BuilderStag Programmers

INDEX OF ADVERTISERS

57, 62, 81625721201956563237

38, 46, 47, 8111

6667

33, 7361

Back cover25576262

4506357

Inside back cover456239

Stewart of ReadingSuma DesignsThose EngineersTsien (UK) LtdUltimate TechnologyViewcom Electronics

25512549

Inside front cover14, 15

ADVERTISING SPACEfor the March 1995 issue may be reserved

not later than12 January 1995 by

Elektor Electronics (Publishing)Advertisement Office3 Crescent Terrace

Cheltenham GL50 3PEEngland

Telephone (01242) 510 760Fax (01242) 226 626

to whom all correspondence, copy instructions andartwork should be addressed.

Focus article in the March 1995 issue will beCD-ROM



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Analog Module: Tuning tin RF front end.

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Electronics Workbench is a highlyproductive bench where you design andverify circuits in a fraction of the time.Connections are always perfect.Wiresroute themselves. And the simulatedcomponents and test instruments workjust like the real thing.

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Digital Module: Analyzing a logic circuit.

It's faster than building with actualcomponents because you changeconnections and component valuesinstantly. And since the simulatedcomponents are free, you don't need toreplace burnt -out parts or keep anextensive inventory. The result: You saveprecious time and money. Guaranteed!

The standard for simplicity and power forover six years, Electronics Workbench is themost popular tool of its kind. It has gainedworldwide acclaim as the ideal complementto any test bench. Fact: Over 90% ofour customers recommend it totheir friends and colleagues.

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Over 800 colour packed pageswith hundreds of Brand New

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OUT OFTHIS WORLD

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Available from all branches of WHSMITH, John Menzies in ScotianONLY, Eason El' Son in N. Ireland ONLY, and Maplin stores nationwideThe Maplin Electronics 1995 Catalogue - OUT OF THIS WORLD

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