Common for All File

8/12/2019 Common for All File

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Resistors

Example:

Circuit symbol:

Function

Resistors restrict the flow of electric current, for example a resistor is placedin series with a light-emitting diode (LED to limit the current passingthrough the LED!

Connecting and soldering

Resistors may be connected either way round! "hey are not damaged by heatwhen soldering!

Resistor values - the resistor colour code

The Resistor

Colour CodeColour #umber

$lac% &

$rown '

Red

)range *

+ellowreen .

$lue /

0iolet 1

rey 2

3hite 4


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Resistance is measured in ohms5 the symbol for ohm is an omega !' is 6uite small so resistor 7alues are often gi7en in % and 8 !' % 9 '&&& ' 8 9 '&&&&&& !

Resistor 7alues are normally shown using coloured bands!

Each colour represents a number as shown in the table!

8ost resistors ha7e bands:

"he first band gi7es the first digit ! "he second band gi7es the second digit ! "he third band indicates the number of zeros ! The fourth band is used to shows the tolerance (precision) of the

resistor, this may be ignored for almost all circuits but further detailsare given below .

"his resistor has red ( , 7iolet (1 , yellow ( eros and gold bands!

;o its 7alue is 1&&&& 9 1& % !)n circuit diagrams the is usually omitted and the 7alue is written 1&

Small value resistors (less than 10 ohm)

"he standard colour code cannot show 7alues of less than '& ! "o showthese small 7alues two special colours are used for the third band : goldwhich means = &!' and silver which means = &!&'! "he first and secondbands represent the digits as normal!

>or example:
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Red , violet , gold bands represent 1 = &!' 9 !1green , blue , silver bands represent ./ = &!&' 9 &!./

Tolerance of resistors (fourth band of colour code)

"he tolerance of a resistor is shown by the fourth band of the colourcode! "olerance is the precision of the resistor and it is gi7en as apercentage! >or example a *4& resistor with a tolerance of ?'&@ willha7e a 7alue within '&@ of *4& , between *4& - *4 9 *.' and *4& A*4 9 4 (*4 is '&@ of *4& !

B special colour code is used for the fourth band tolerance:silver ?'&@, gold ?.@, red ? @, bro n ?'@!

f no fourth band is shown the tolerance is ? &@!

"olerance may be ignored for almost all circuits because preciseresistor 7alues are rarely re6uired!

!uzzer and !leeper

"hese de7ices are output transducers con7erting electrical energy to sound!"hey contain an internal oscillator to produce the sound which is set at about

&& for bu ers and about * % for bleeper s!$u ers ha7e a 7oltage rating but it is only approximate, for example /0 and' 0 bu ers can be used with a 40 supply! "heir typical current is about.mB!

$leepers ha7e wide 7oltage ranges, such as *-*&0, and they pass a lowcurrent of about '&mB!

$u ers and beepers must be connected the right way round, their red lead is

positi7e (A !


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"nductor (coil)

Bn inductor is a coil of wire which may ha7e a core of air, iron or ferrite (abrittle material made from iron ! ts electrical property is called inductanceand the unit for this is the henry, symbol ! ' is 7ery large so m and Fare used, '&&&F 9 'm and '&&&m 9 ' ! ron and ferrite cores increasethe inductance! nductors are mainly used in tuned circuits and to bloc% highfre6uency BC signals (they are sometimes called cho%es ! "hey pass DCeasily, but bloc% BC signals5 this is the opposite of capacitors !

nductors are rarely found in simple proGects, but one exception is the tuningcoil of a radio recei7er! "his is an inductor which you may ha7e to ma%eyourself by neatly winding enameled copper wire around a ferrite rod!Enameled copper wire has 7ery thin insulation, allowing the turns of the coilto be close together, but this ma%es it impossible to strip in the usual way -the best method is to gently pull the ends of the wire through folded emerypaper!

#arning$ a ferrite rod is brittle so treat it li%e glass, not ironH

Bn inductor may be connected either way round and no special precautionsare re6uired when soldering!

%oudspea&er

Loudspea%ers are output transducers which con7ert an electrical signal to

sound! Isually they are called Jspea%ersJ! "hey re6uire a dri7er circuit, suchas a ... astable or an audio amplifier, to pro7ide a signal! "here is a widerange a7ailable, but for many electronics proGects a *&&m3 miniatureloudspea%er is ideal! "his type is about 1&mm diameter and it is usuallya7ailable with resistances of 2 and / ! f a proGect specifies a / spea%eryou must use this higher resistance to pre7ent damage to the dri7ing circuit!

nductor (miniature

circuit symbol
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8ost circuits used to dri7e loudspea%ers produce an audio (BC signalwhich is combined with a constant DC signal! "he DC will ma%e a largecurrent flow through the spea%er due to its low resistance, possiblydamaging both the spea%er and the dri7ing circuit! "o pre7ent this happeninga large 7alue electrolytic capacitor is connected in series with the spea%er,this bloc%s DC but passes audio (BC signals!

Loudspea%ers may be connected either way round except in stereo circuitswhen the A and - mar%ings on their terminals must be obser7ed to ensure thetwo spea%ers are in phase!

Correct polarity must always be obser7ed for large spea%ers in cabinetsbecause the cabinet may contain a small circuit (a Jcrosso7er networ%Jwhich di7erts the high fre6uency signals to a small spea%er (a JtweeterJ

because the large main spea%er is poor at reproducing them!8iniature loudspea%ers can also be used as a microphone and they wor%

surprisingly well, certainly good enough for speech in an intercom system

for example !

'iodes

Example:

Circuit symbol:

Function


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Diodes must be connected the correct way round, the diagram may belabelled a or * for anode and & or - for cathode (yes, it really is %, not c, forcathodeH ! "he cathode is mar%ed by a line painted on the body! Diodes arelabelled with their code in small print5 you may need a magnifying glass toread this on small signal diodesH

;mall signal diodes can be damaged by heat when soldering, but the ris% issmall unless you are using a germanium diode (codes beginning )B!!! inwhich case you should use a heat sin% clipped to the lead between the Gointand the diode body! B standard crocodile clip can be used as a heat sin%!

Rectifier diodes are 6uite robust and no special precautions are needed forsoldering them!

Testing diodes

+ou can use a multimeter or a simple tester (battery, resistor and LED tochec% that a diode conducts in one direction but not the other! B lamp maybe used to test a rectifier diode , but do #)" use a lamp to test a signal diodebecause the large current passed by the lamp will destroy the diodeH

Signal diodes (small current)

;ignal diodes are used to process information (electrical signals in circuits,so they are only re6uired to pass small currents of up to '&&mB!

eneral purpose signal diodes such as the '# ' 2 are made from siliconand ha7e a forward 7oltage drop of &!10!

+ermanium diodes such as the )B4& ha7e a lower forward 7oltage drop of&! 0 and this ma%es them suitable to use in radio circuits as detectors whichextract the audio signal from the wea% radio signal!
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Bll rectifier diodes are made from silicon and therefore ha7e a forward7oltage drop of &!10! "he table shows maximum current and maximumre7erse 7oltage for some popular rectifier diodes! "he '# &&' is suitable formost low 7oltage circuits with a current of less than 'B!

!ridge rectifiers

"here are se7eral ways of connecting diodes to ma%e a rectifier to con7ertBC to DC! "he bridge rectifier is one of them and it is a7ailable in specialpac%ages containing the four diodes re6uired! $ridge rectifiers are rated bytheir maximum current and maximum re7erse 7oltage! "hey ha7e four leadsor terminals: the two DC outputs are labelled A and -, the two BC inputs arelabelled !

.ener diodes

Example:

Circuit symbol:a 9 anode, % 9 cathode


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Kener diodes are used to maintain a fixed 7oltage! "hey are designed toJbrea%downJ in a reliable and non-destructi7e way so that they can be used inreverse to maintain a fixed 7oltage across their terminals! "he diagramshows how they are connected, with a resistor in series to limit the current!

Kener diodes can be distinguished from ordinary diodes by their code and

brea%down 7oltage which are printed on them! Kener diode codes begin$K !!! or $K+!!! "heir brea%down 7oltage is printed with 0 in place of adecimal point, so 01 means !10 for example!

Kener diodes are rated by their brea%down 7oltage and maximum power:

"he minimum 7oltage a7ailable is !10! Mower ratings of &&m3 and '!*3 are common !

%ight /mitting 'iodes (%/'s)

Example:

Circuit symbol:

Function

LEDs emit light when an electric current passes through them!



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"he colour of an LED is determined by the semiconductor material, not bythe colouring of the Jpac%ageJ (the plastic body ! LEDs of all colours area7ailable in uncolored pac%ages which may be diffused (mil%y or clear(often described as Jwater clearJ ! "he coloured pac%ages are also a7ailableas diffused (the standard type or transparent!

Tri-colour %/'s

"he most popular type of tri-colour LED has a red and a green LEDcombined in one pac%age with three leads! "hey are called tri-colourbecause mixed red and green light appears to be yellow and this is producedwhen both the red and green LEDs are on!

"he diagram shows the construction of a tri-colour LED! #ote the differentlengths of the three leads! "he centre lead (% is the common cathode forboth LEDs5 the outer leads (a' and a are the anodes to the LEDs allowingeach one to be lit separately, or both together to gi7e the third colour!

!i-colour %/'s

B bi-colour LED has two LEDs wired in Jin7erse parallelJ (one forwards, onebac%wards combined in one pac%age with two leads! )nly one of the LEDscan be lit at one time and they are less useful than the tri-colour LEDsdescribed abo7e!

Sizes Shapes and ie ing angles of %/'s


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LEDs are a7ailable in a wide 7ariety of si es and shapes!"he JstandardJ LED has a round cross-section of .mmdiameter and this is probably the best type for general use,but *mm round LEDs are also popular!

Round cross-section LEDs are fre6uently used and they are 7ery easy toinstall on boxes by drilling a hole of the LED diameter, adding a spot of gluewill help to hold the LED if necessary! LED clips are also a7ailable to secureLEDs in holes! )ther cross-section shapes include s6uare, rectangular andtriangular!

LED Clip


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CapacitorsFunction

Capacitors store electric charge! "hey are used with resistors intiming circuits because it ta%es time for a capacitor to fill with charge! "heyare used to smooth 7arying DC supplies by acting as a reser7oir of charge!"hey are also used in filter circuits because capacitors easily pass BC(changing signals but they bloc% DC (constant signals!

Capacitance

"his is a measure of a capacitorJs ability to store charge! B large capacitancemeans that more charge can be stored! Capacitance is measured in farads,symbol >! owe7er '> is 7ery large, so prefixes are used to show thesmaller 7alues!

"hree prefixes (multipliers are used, F (micro , n (nano and p (pico :

F means '& -/ (millionth , so '&&&&&&F> 9 '> n means '& -4 (thousand-millionth , so '&&&n> 9 'F> p means '& -' (million-millionth , so '&&&p> 9 'n>

Capacitor 7alues can be 7ery difficult to find because there are many typesof capacitor with different labelling systemsH

"here are many types of capacitor but they can be split into two groups,polarised and 2npolarised ! Each group has its own circuit symbol !

,olarised capacitors (large values 13F *)

Examples:

Circuit symbol:
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/lectrol tic Capacitors

Electrolytic capacitors are polari ed and the must be connected thecorrect a round , at least one of their leads will be mar%ed A or -! "heyare not damaged by heat when soldering!

"here are two designs of electrolytic capacitors5 a ial where the leads areattached to each end ( &F> in picture and radial where both leads are atthe same end ('&F> in picture ! Radial capacitors tend to be a little smallerand they stand upright on the circuit board!

t is easy to find the 7alue of electrolytic capacitors because they are clearlyprinted with their capacitance and 7oltage rating! "he 7oltage rating can be6uite low (/0 for example and it should always be chec%ed when selecting

an electrolytic capacitor! t the proGect parts list does not specify a 7oltage5choose a capacitor with a rating which is greater than the proGectJs powersupply 7oltage! .0 is a sensible minimum for most battery circuits!

Tantalum !ead Capacitors

"antalum bead capacitors are polarised and ha7e low 7oltage ratings li%eelectrolytic capacitors! "hey are expensi7e but 7ery small, so they are usedwhere a large capacitance is needed in a small si e!

8odern tantalum bead capacitors are printed with their capacitance, 7oltageand polarity in full! owe7er older ones use a colour-code system which hastwo stripes (for the two digits and a spot of colour for the number of erosto gi7e the 7alue in F>! "he standard colour code is used, but for the spot,gre is used to mean = &!&' and hite means = &!' so that 7alues of lessthan '&F> can be shown! B third colour stripe near the leads shows the7oltage (yellow /!*0, blac% '&0, green '/0, blue &0, grey .0, white*&0, pin% *.0 ! "he positi7e (A lead is to the right when the spot is facing

you: J hen the spot is in sight the positive is to the right J!

>or example: blue gre blac& spot means /2F>>or example: blue gre hite spot means /!2F>>or example: blue gre gre spot means &!/2F>
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2npolarised capacitors (small values up to 13F)

Examples:

Circuit symbol:

;mall 7alue capacitors are Inpolarised and may be connected either wayround! "hey are not damaged by heat when soldering, except for oneunusual type (polystyrene ! "hey ha7e high 7oltage ratings of at least .&0,usually .&0 or so! t can be difficult to find the 7alues of these small

capacitors because there are many types of them and se7eral differentlabelling systemsH

8any small 7alue capacitors ha7e their 7alue printed but without amultiplier, so you need to use experience to wor% out what the multipliershould beH

>or example 041 means &!'F> 9 '&&n>!

;ometimes the multiplier is used in place of the decimal point:>or example: 5n6 means !1n>!

Capacitor 7umber Code

B number code is often used on small capacitors where printing is difficult: the 'st number is the 'st digit, the nd number is the nd digit, the *rd number is the number of eros to gi7e the capacitance in p>! gnore any letters - they Gust indicate tolerance and 7oltage rating!

>or example: 108 means '&&&p> 9 'n> (not 102pF )


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>or example: 5689 means 1&&p> 9 !1n> (N means .@ tolerance !

Capacitor Colour Code

B colour code was used on polyester capacitors for many years! t is nowobsolete, but of course there are many still around! "he colours should beread li%e the resistor code, the top three colour bands gi7ing the 7alue in p>!gnore the th band (tolerance and .th band (7oltage rating !

>or example:

bro n blac& orange means '&&&&p> 9 '&n> 9 &!&'F>!

#ote that there are no gaps between the colour bands, so identical bandsactually appear as a wide band!

>or example:

ide red ello means &n> 9 &! F>!

,ol st rene Capacitors

Colour Code

Colour #umber

$lac% &

$rown '

Red

)range *

+ellowreen .

$lue /

0iolet 1

rey 2

3hite 4


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"his type is rarely used now! "heir 7alue (in p> is normally printed withoutunits! Molystyrene capacitors can be damaged by heat when soldering (itmelts the polystyreneH so you should use a heat sin% (such as a crocodileclip ! Clip the heat sin% to the lead between the capacitor and the Goint!

Real capacitor values (the /: and /; series)

+ou may ha7e noticed that capacitors are not a7ailable with e7ery possible7alue, for example F> and 1F> are readily a7ailable, but .F> and .&F>are notH

3hy is thisO magine that you decided to ma%e capacitors e7ery '&F> gi7ing'&, &, *&, &, .& and so on! "hat seems fine, but what happens when youreach '&&&O t would be pointless to ma%e '&&&, '&'&, '& &, '&*& and so onbecause for these 7alues '& is a 7ery small difference, too small to benoticeable in most circuits and capacitors cannot be made with thataccuracy!

"o produce a sensible range of capacitor 7alues you need to increase the si eof the JstepJ as the 7alue increases! "he standard capacitor 7alues are basedon this idea and they form a series which follows the same pattern for e7ery

multiple of ten!The /: series (* 7alues for each multiple of ten10 88 56 then it continues '&&, &, 1&, '&&&, &&, 1&&, '&&&& etc!#otice how the step si e increases as the 7alue increases (7alues roughlydouble each time !

The /; series (/ 7alues for each multiple of ten10 1< 88 :: 56 ;= then it continues '&&, '.&, &, **&, 1&, /2&, '&&&etc!

#otice how this is the E* series with an extra 7alue in the gaps!

"he E* series is the one most fre6uently used for capacitors because manytypes cannot be made with 7ery accurate 7alues!


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ariable capacitors

0ariable capacitors are mostly used in radio tuning circuits and they aresometimes called Jtuning capacitorsJ! "hey ha7e 7ery small capacitance7alues, typically between '&&p> and .&&p> ('&&p> 9 &!&&&'F> ! "he typeillustrated usually has trimmers built in (for ma%ing small adGustments - seebelow as well as the main 7ariable capacitor!

8any 7ariable capacitors ha7e 7ery short spindles which are not suitable forthe standard %nobs used for 7ariable resistors and rotary switches! t wouldbe wise to chec% that a suitable %nob is a7ailable before ordering a 7ariablecapacitor!

0ariable capacitors are not normally used in timing circuits because their

capacitance is too small to be practical and the range of 7alues a7ailable is7ery limited! nstead timing circuits use a fixed capacitor and a 7ariableresistor if it is necessary to 7ary the time period!

Trimmer capacitors

0ariable Capacitor ;ymbol

0ariable Capacitor


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"rimmer capacitors (trimmers areminiature 7ariable capacitors! "hey aredesigned to be mounted directly ontothe circuit board and adGusted onlywhen the circuit is built!

B small screwdri7er or similar tool is re6uired to adGust trimmers! "heprocess of adGusting them re6uires patience because the presence of yourhand and the tool will slightly change the capacitance of the circuit in theregion of the trimmerH

"rimmer capacitors are only a7ailable with 7ery small capacitances,

normally less than '&&p>! t is impossible to reduce their capacitance toero, so they are usually specified by their minimum and maximum 7alues,for example -'&p>!

>ultimeters8ultimeters are 7ery useful test instruments! $y operating a multi-position

switch on the meter they can be 6uic%ly and easily setto be a voltmeter , an ammeter or an ohmmeter ! "heyha7e se7eral settings (called JrangesJ for each type ofmeter and the choice of BC or DC! ;ome multimetersha7e additional features such as transistor testing and ranges for measuringcapacitance and fre6uency!

Choosing a multimeter

"he photographs below show modestly priced multimeters which aresuitable for general electronics use, you should be able to buy metersli%e these for less than P'.! B digital multimeter is the best choice foryour first multimeter5 e7en the cheapest will be suitable for testingsimple proGects!

"rimmer Capacitor ;ymbol

"rimmer Capacitor

Li6uid-Crystal Display(LCD


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f you are buying an analogue multimeter ma%e sure it has a highsensitivit of &% Q0 or greater on DC 7oltage ranges, anything less is notsuitable for electronics! "he sensiti7ity is normally mar%ed in a corner of thescale, ignore the lower BC 7alue (sensiti7ity on BC ranges is lessimportant , the higher DC 7alue is the critical one! $eware of cheapanalogue multimeters sold for electrical wor% on cars because theirsensiti7ity is li%ely to be too low !

'igital multimeters

Bll digital meters contain a battery to power the display so they use 7irtuallyno power from the circuit under test! "his means that on their DC 7oltageranges they ha7e a 7ery high resistance (usually called input impedance of'8 or more, usually '&8 , and they are 7ery unli%ely to affect the circuitunder test!

"ypical ranges for digital multimeters li%e the one illustrated: (the 7alues gi7enare the maximum reading on each range

DC 0oltage: &&m0, &&&m0, &0, &&0, /&&0! BC 0oltage: &&0, /&&0! DC Current: &&FB, &&&FB, &mB, &&mB, '&B ! "he '&B range is usually unused and connected 7ia a special soc%et! BC Current: #one! (+ou are unli%ely to need to measure this ! Resistance: && , &&& , &% , &&% , &&&% , Diode "est!

Digital 8ultimeter


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Digital meters ha7e a special diode test setting because their resistanceranges cannot be used to test diodes and other semiconductors!

>ultimeters are easil damaged b careless use so please ta%e theseprecautions:

Blways disconnect the multimeter before adGusting the range switch! Blways chec% the setting of the range switch before you connect to a

circuit! #e7er lea7e a multimeter set to a current range (except when actually

ta%ing a reading !"he greatest ris% of damage is on the current ranges because the meter has a lowresistance!

Rela s

B relay is an electricall operated s itch ! Current flowing through the coilof the relay creates a magnetic field which attracts a le7er and changes theswitch contacts! "he coil current can be on or off so relays ha7e two switchpositions and they are double thro (changeover switches!

Circuit symbol for a relay

Relays
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Relays allow one circuit to switch a second circuit which can be completelyseparate from the first! >or example a low 7oltage battery circuit can use arelay to switch a *&0 BC mains circuit! "here is no electrical connectioninside the relay between the two circuits, the lin% is magnetic andmechanical!

"he coil of a relay passes a relati7ely large current, typically *&mB for a' 0 relay, but it can be as much as '&&mB for relays designed to operatefrom lower 7oltages! 8ost Cs (chips cannot pro7ide this current and atransistor is usually used to amplify the small C current to the larger 7aluere6uired for the relay coil! "he maximum output current for the popular ...timer C is &&mB so these de7ices can supply relay coils directly withoutamplification!

Relays are usually ;MD" or DMD" but they can ha7e many more sets ofswitch contacts, for example relays with sets of changeo7er contacts arereadily a7ailable!

8ost relays are designed for MC$ mounting but you can solder wiresdirectly to the pins pro7iding you ta%e care to a7oid melting the plastic caseof the relay!

"he supplierJs catalogue should show you the relayJs connections! "he coilwill be ob7ious and it may be connected either way round! Relay coils

produce brief high 7oltage Jspi%esJ when they are switched off and this candestroy transistors and Cs in the circuit! "o pre7ent damage you mustconnect a protection diode across the relay coil!

"he animated picture shows a wor%ing relay with its coil and switchcontacts! +ou can see a le7er on the left being attracted by magnetism whenthe coil is switched on! "his le7er mo7es the switch contacts! "here is oneset of contacts (;MD" in the foreground and another behind them, ma%ingthe relay DMD"!

"he relayJs switch connections are usually labelled C)8, #C and #):

C?> 9 Common, always connect to this5 it is the mo7ingpart of the switch!
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7C 9 #ormally Closed, C)8 is connected to this when therelay coil is off !

7? 9 #ormally )pen, C)8 is connected to this when therelay coil is on !

Connect to C)8 and #) if you want the switched circuit to be onhen the rela coil is on !

Connect to C)8 and #C if you want the switched circuit to be onhen the rela coil is off !

ST/, T@A/7 #B"%/ ,R/,@R"7+ C"RC2"T

"he main purpose of printed circuit is in the routing of electriccurrents and signals through thin copper layer that is bounded

fi rmly to and insulat ing base mater ial some t imes cal led the

substrata! "his base is manufactured with an integral bounded

layer of thin copper foil which has to be part ly etched or other

wise remo7ed to arr i7e a t a pre-des igned pat tern to su i te the

circuit connections!

>rom the constructors point of 7iew the main attraction of using

MC$ is its role as the mechanical support for small components!

"here is less need for complicated and t ime consuming metal

wor% or chassis construction except perhaps in pro7iding the

Smal enclosure! 8os t s t ra ight forward c ircuit des igns can be

easily con7erted into printed wiring layout the thorough re6uiredto carry out the con7ersion can often highlights any possible

error that would otherwise be missed in con7ention point to point

wiring! "he finished proGect is usually neater and truly a wor% of

art!


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"hrough proper design of MC$ can get noise

immunity! "he fabrication process of the printed circuit board

will determine to a large extent the price and rel iabil i ty of the

e6uipment! B common target aimed at is the fabrication of smallser ies of h ighly re liab le profess ional 6uali ty MC$s with low

in7estment cost!

There are t o t pes of ,C!$-

14 Single sided board

84 'ouble sided board

Single sided board

"he single sided MC$s are mostly used in endearment electronics

whe re manu factur in g cos ts h a7 e t o b e % ep t a t a minimu m

howe7er in industrial electronics! Blso cast factors cannot be

neglected and single sided boards should be used whene7er a

particular circuit can be accommodated on such boards!

'ouble sided boards

Double sided MC$s can be made with or without plated through

holes! "he production of boards with plated-through holes is

fairly expensi7e! "herefore, plated through hole boards are onlychosen where the circuit complexity and density dose not lea7e

any other choice!

%@ ?2T '/S"+7


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"he layout of a MC$ has to incorporate all the information on the

board before one can go on to the ar twor% preparation! "his

means that a concept, which clearly defines all the details of the

circuit, is a prere6uisite before the actual layout can start! "hedetai led c ircui t d iagram is 7ary ing important for the layout

designer but the must also be familiar with the design concept

and with the philosophy behind the e6uipment! 3hen designing

the layout one should obser7e the minimum s i e (component

body length and weight ! $efore start ing to design the layout

ha7e a l l the re6uired components to hand so that an accurate

assessment of space can be made care must be ta%en so as to

allow for ade6uate a ir f low after the components ha7e been

mounted!

t might be necessary to turn some components round to a

d ifferent angular pos it ion so that terminals are c loser to the

connections of other components! "he scale can be chec%ed by

positioning the components on the s6uad paper! f any connection

crosses , then one can rerou te to a7o id such condi tion ! B ll

common or earth lines should ideally be connected to a common

line routed around the perimeter of the layout this will act as the

ground p lane! f possibly t ry to rou te the outer supply l ine

ground p lane! f possibly t ry to route the o ther supply l ines

around the apposite edge of the layout or through the center! "hefirst s tep is to rearrange the circuit to el iminate the crosso7er

without altering the circuit detail in any way!

Mlan the layout as if loo%ing at the top side of the board first this


27/46

should be t rans la ted in re7erse later for the e tching pat tern!

Larger areas are recommended to maintain good copper adhesi7e!

t is important to bear in mind always that copper trac% width

must be at least to the recommended minimum dimensions andallowance must be made for increased width where termination

holes are needed from this aspect i t can become l i t t le tr ic%y to

negotiate the route for connections to small transistors! )ne can

effect the copper interconnection pattern in the under side of the

board in a way descr ibed below 8a%e the interconnec tions

pat tern loo%ing l i%e con7ent ional point to point writ ing by

routing uniform width of copper from component to component

/TCB"7+ ,R?C/SS

Etching process re6uires the use of chemicals , acid resistan t

d is hes and a run ning water s up ply ! > er ri c chlor id e i s t he

maximum used solution, but other enchants such as ammonium

sulphate can be used!

#itric acid can also be used but in general it is not used due to

the poisonous fumes! "he pattern prepared is glued to the copper

surface of the board using a latex type of adhesi7e that can be

cubed after use! "he pattern is laid fir mly on the copper, use 7arysharp %nife to cut round the pattern carefully and remo7e the

paper corresponding to the re6uired copper pattern areas! "hen

apply the resist solution clean outlines as for as possible! 3hile

the board is drying to test al l components! $efore going to the


28/46

next stage, chec% the whole pattern and cross chec% against the

circuit diagram chec% for any foreign matter on the copper! "he

etching bath should be in a glass or enamel dis%! f using crystal

of ferric chloride these should be thoroughly dissol7ed in waterto the proportion suggested! "here should be &!. Lt! )f water for

' . gm of crystal! "he board is then immersed in >eCl* solution

for ' hours, in this process only the non hidden copper portion

is etched out by the solution!

8FeCl: * 8B8? * :Cu 0 :CuCl8 * 8Fe (?B) 8

3aste l i6uid should be thoroughly diluted and buried in water

land ne7er pour down the drain! "o pre7ent particles of copper

hindering fur ther e tching , agi ta te the solut ions careful ly by

gently twisting or roc%ing the tray! "he board should not be left

in the bath a moment longer than is needed to remo7e Gust the

right amount of cooper! n spite of there being a resist coating,

there is no protection against e tching away through exposed

copper edges5 this leads to o7er etching! a7e running water

ready so that the e tched board can be remo7ed properly and

rinsed5 this will halt etching immediate!

#ow the paint is washed out by the petr ol! #ow the copper layouton MC$ is rubbed with a smooth sand paper s lowly and l ightly

such that only the oxide layers o7er the Cu is remo7ed! #ow the

holes are drilled at the respecti7e places, according to component

layout as shown in figure! Drilling is one of those operation that


29/46


30/46

Blthough transistors and integrated circuits are small items, there

are good reasons for lea7ing the soldering of these until the last

s tep! "he main point i s tha t these components a re 7arying

sensiti7e to heat and if subGected to prolonged application of thesoldering i ron, they cou ld be interna lly damaged! B ll the

components before mounting are rubbed with sand paper so that

oxide layer is remo7ed iron their t ips! #ow they are mounted

according to the components layout!

Soldering +uide

How to Solder

First a fe safet precautions$

7ever touch the element or tip of the soldering iron4 "hey are 7ery hot (about &&TC and will gi7e you a nasty burn!

Ta&e great care to avoid touching the mains fle ith the tip ofthe iron4

"he iron should ha7e a heatproof flex for extra protection! Bnordinary plastic flex will melt immediately if touched by a hot ironand there is a serious ris% of burns and electric shoc%!

@l a s return the soldering iron to its stand hen not in use4 #e7er put it down on your wor%bench, e7en for a momentH #or& in a ell-ventilated area4 "he smo%e formed as you melt solder is mostly from the flux and

6uite irritating! B7oid breathing it by %eeping you head to the side of,not abo7e, your wor%!

#ash our hands after using solder4 ;older contains lead which is a poisonous metal!

,reparing the soldering iron$

,lace the soldering iron in its stand and plug in4 "he iron will ta%e a few minutes to reach its operating temperature ofabout &&TC!


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'ampen the sponge in the stand4 "he best way to do this is to lift it out the stand and hold it under a

cold tap for a moment, then s6uee e to remo7e excess water! t shouldbe damp, not dripping wet!

#ait a fe minutes for the soldering iron to arm up4 +ou can chec% if it is ready by trying to melt a little solder on the tip!

#ipe the tip of the iron on the damp sponge4 "his will clean the tip!

>elt a little solder on the tip of the iron4 "his is called JtinningJ and it will help the heat to flow from the ironJstip to the Goint! t only needs to be done when you plug in the iron, andoccasionally while soldering if you need to wipe the tip clean on thesponge!

ou are no read to start soldering$

Bold the soldering iron li&e a pen near the base of the handle4 magine you are going to write your nameH Remember to ne7er touch

the hot element or tip! Touch the soldering iron onto the Doint to be made4

8a%e sure it touches both the component lead and the trac%! old thetip there for a few seconds and!!! Feed a little solder onto the Doint4 t should flow smoothly onto the lead and trac% to form a 7olcano

shape as shown in the diagram! Bpply the solder to the Goint, not theiron!

Remove the solder then the iron hile &eeping the Doint still4


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Bllow the Goint a few seconds to cool before you mo7e the circuitboard!

"nspect the Doint closel 4 t should loo% shiny and ha7e a J7olcanoJ shape! f not, you will need

to reheat it and feed in a little more solder! "his time ensure that both

the lead and trac% are heated fully before applying solder!

2sing a heat sin&

;ome components, such as transistors, can be damaged by heat whensoldering so if you are not an expert it is wise to use a heat sin% clipped tothe lead between the Goint and the component body! +ou can buy a specialtool, but a standard crocodile clip wor%s Gust as well and is cheaper!;oldering Bd7ice for Componentst is 7ery tempting to start soldering components onto the circuit boardstraight away, but please ta%e time to identify all the parts first! +ou aremuch less li%ely to ma%e a mista%e if you do thisH

'! Stic& all the components onto a sheet of paper using stic& tape4 ! "dentif each component and write its name or 7alue beside it!*! @dd the code (R1 R8 C1 etc4) if necessar 4

Crocodile clip


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! 8any proGects from boo%s and maga ines label the components withcodes (R', R , C', D' etc! and you should use the proGectJs parts listto find these codes if they are gi7en!

.! Resistor values can be found using the resistor colour code which isexplained on our Resistors page! +ou can print out and ma%e yourown Resistor Colour Code Calculator to help you!

/! Capacitor values can be difficult to find because there are manytypes with different labelling systemsH "he 7arious systems areexplained on our Capacitors page!

;ome components re6uire special care when soldering! 8any must be placedthe correct way round and a few are easily damaged by the heat fromsoldering! Bppropriate warnings are gi7en in the table below, together with

other ad7ice which may be useful when soldering!

>or most proGects it is best to put the components onto the board in the ordergi7en below:

Components ,ictures Reminders and#arnings

'Chip Bolders(D L soc%ets

Connect the correct around by ma%ing sure the

notch is at the correct end!Do #)" put the Cs (chips inyet!

Resistors #o special precautions areneeded with resistors!

* Small value capacitors(usually less than 'F>

"hese may be connected eitherway round!"a%e care with polystyrenecapacitors because they areeasily damaged by heat!

/lectrol tic capacitors('F> and greater

Connect the correct around4 "hey will be mar%edwith a A or - near one lead!

. 'iodes Connect the correct around4 "a%e care with germanium
http://www.kpsec.freeuk.com/components/ic.htmhttp://www.kpsec.freeuk.com/components/resist.htmhttp://www.kpsec.freeuk.com/components/capac.htmhttp://www.kpsec.freeuk.com/components/capac.htmhttp://www.kpsec.freeuk.com/components/diode.htmhttp://www.kpsec.freeuk.com/components/ic.htmhttp://www.kpsec.freeuk.com/components/resist.htmhttp://www.kpsec.freeuk.com/components/capac.htmhttp://www.kpsec.freeuk.com/components/capac.htmhttp://www.kpsec.freeuk.com/components/diode.htm


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diodes (e!g! )B4' becausethey are easily damaged byheat!

/ %/'s

Connect the correct a

round4 "he diagram may be labelled aor * for anode and & or - forcathode5 yes, it really is %, notc, for cathodeH "he cathode isthe short lead and there may bea slight flat on the body ofround LEDs!

1 Transistors

Connect the correct around4

"ransistors ha7e * JlegsJ (leadsso extra care is needed toensure the connections arecorrect!Easily damaged by heat!

2 #ire %in&s between pointson the circuit board! single core wire

Ise single core wire5 this isone solid wire which is plastic-coated!f there is no danger oftouching other parts you can

use tinned copper wire, this hasno plastic coating and loo%s

Gust li%e solder but it is stiffer!

4!atter clips , buzzers andother parts with their ownwires

Connect the correct around4

'&

#ires to parts off thecircuit board, includings itches , rela s ,

variable resistors andloudspea&ers ! stranded wire

+ou should use stranded wirewhich is flexible and plastic-coated!Do not use single core wirebecause this will brea% when itis repeatedly flexed!

'' "Cs (chips) Connect the correct around4 >an "Cs are static sensitive4
http://www.kpsec.freeuk.com/components/led.htmhttp://www.kpsec.freeuk.com/components/tran.htmhttp://www.kpsec.freeuk.com/components/connect.htmhttp://www.kpsec.freeuk.com/components/connect.htmhttp://www.kpsec.freeuk.com/components/connect.htmhttp://www.kpsec.freeuk.com/components/connect.htmhttp://www.kpsec.freeuk.com/components/switch.htmhttp://www.kpsec.freeuk.com/components/relay.htmhttp://www.kpsec.freeuk.com/components/relay.htmhttp://www.kpsec.freeuk.com/components/vres.htmhttp://www.kpsec.freeuk.com/components/ic.htmhttp://www.kpsec.freeuk.com/components/ic.htmhttp://www.kpsec.freeuk.com/components/led.htmhttp://www.kpsec.freeuk.com/components/tran.htmhttp://www.kpsec.freeuk.com/components/connect.htmhttp://www.kpsec.freeuk.com/components/connect.htmhttp://www.kpsec.freeuk.com/components/connect.htmhttp://www.kpsec.freeuk.com/components/switch.htmhttp://www.kpsec.freeuk.com/components/relay.htmhttp://www.kpsec.freeuk.com/components/vres.htmhttp://www.kpsec.freeuk.com/components/ic.htm


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36/46

14 #ith a desoldering pump (solder suc&er)

;et the pump by pushing the spring-loaded plunger down until itloc%s!

Bpply both the pump no le and the tip of your soldering iron to the Goint!

3ait a second or two for the solder to melt! "hen press the button on the pump to release the plunger and suc% the

molten solder into the tool! Repeat if necessary to remo7e as much solder as possible! "he pump will need emptying occasionally by unscrewing the no le!

84 ith solder remover ic& (copper braid) Bpply both the end of the wic% and the tip of your soldering iron to

the Goint! Bs the solder melts most of it will flow onto the wic%, away from the

Goint! Remo7e the wic% first, then the soldering iron! Cut off and discard the end of the wic% coated with solder!

Bfter remo7ing most of the solder from the Goint(s you may be able to

remo7e the wire or component lead straight away (allow a few seconds for itto cool ! f the Goint will not come apart easily apply your soldering iron tomelt the remaining traces of solder at the same time as pulling the Gointapart, ta%ing care to a7oid burning yourself!

First @id for !urns8ost burns from soldering are li%ely to be minor and treatment is simple:

"mmediatel cool the affected area under gentl running coldater4


37/46

See& medical attention if the burn covers an area bigger thanour hand4

"o reduce the ris% of burns: Blways return your soldering iron to its stand immediately after use! Bllow Goints and components a minute or so to cool down before you

touch them! #e7er touch the element or tip of a soldering iron unless you are

certain it is cold!

%>


38/46

than%s to i ts ease of use, low price, and good stabi l i ty! t is now

made by many companies in the orig inal b ipolar and also in low-

power C8); types! Bs of &&*, it was estimated that ' billion units

are manufactured e7ery year!

"he C was designed in '41 ' by ans Camen ind under contract to

;ignetics, which was later ac6uired by Mhilips!

Depending on the manufacturer, the standard .. . pac%age includes .

transistors, diodes and '. resistors on a silicon chip installed in an

2-pin min i dual -in- line pac%age (D M-2 !S U 0ar iants a7ailab le

include the . . / (a ' -pin D M combining two . . .s on one chip , and

the two . .2 V . .4s (bo th a ' / -p in D M combining four s ligh tly

modif ied . .. s with D ; V " R connected internally, and "R is

falling edge sensiti7e instead of le7el sensiti7e !

"he #E... parts were commercial temperature range, & TC to A1& TC,

and the ;E. .. par t number des ignated the mil itary temperatu re


39/46

range, W.. TC to A' . TC! "hese

were a7ailable in both high-rel iabi li ty

metal can (" pac%age and

inexpensi7e epoxy plast ic (0 pac%agepac%ages! "hus the ful l par t numbers

were #E...0, #E...", ;E.. .0, an d ;E. .."! t has been

hypothesi ed that the . . . got its name from the three . %X resistors

used within,S*U but ans Camen ind has stated that the number was

arbitrary!

Low-power 7ersions of the . . . are also a7ailable, such as the 1. . .

and C8); "LC. . . !S U "he 1 . . . is designed to cause less supplynoise than the classic .. . and the manufacturer claims that it usually

does not re6uire a YcontrolY capacitor and in many cases does not

re6uire a decoupling capacitor on the power supply! ;uch a practice

should ne7ertheless be a7oided, because noise produced by the timer

or 7ariation in power supply 7oltage might interfere with other parts

of a circuit or influence its threshold 7oltages!

,ins

Minout diagram

"he connection of the pins for a D M pac%age is as follows:


40/46


41/46

"he .. . has three operating modes: >onostable mode: n th is mode, the . . . functions as a Yone-

shotY pulse generator! Bpplicat ions include t imers, missing

pulse detection, bouncefree switches, touch switches, fre6uencydi7ider, capacitance measurement, pulse-width

modulation (M38 and so on! @stable (free-running mode: "he .. . can operate as

an oscillator ! Ises includ e LED an d l amp f la sh er s, p uls e

generation, logic cloc%s, tone generation, security alarms, pulse

position modulation an d so on! "he .. . can b e used as a

simple BDC , con7erting an analog 7alue to a pulse length! E!g!selecting a thermistor as t iming resistor al lows the use of the

. . . in a temperature sensor: the period of the output pulse is

determined by the temperature! "he use of a microprocessor

based circuit can then con7ert the pulse period to temperature,

lineari e it and e7en pro7ide calibration means! !istable mod e o r ;chmitt t r igger : " he . .. c an o pe ra te a s

a flip-flop , if the D ; pin is not connected and no capacitor is

used! Ises include bounce-free latched switches!

?perational amplifier %>:


42/46

Characteristics of a circuit using an op-amp are set by external

components with l i tt le dependence on temperature changes or

manufacturing 7ariations in the op-amp itself, which ma%es op-

amps popular building bloc%s for circuit design!)p-amps are among the most widely used e lect ronic de7ices

today, being used in a 7ast array of consumer, industrial , and

scientific de7ices! 8any standard C op-amps cost only a few

cents in moderate production 7olume5 howe7er some integrated

or hybrid opera tional ampli fi ers with special per fo rmance

specifications may cost o7er Z'&& I; in small 6uanti t ies! )p-

amps may be pac%aged as components, or used as elements of

more complex integrated circuits!

"he op-amp is one type of differential amplifier ! )ther types of

differential amplifier include the fully differ ential

amplifier ( si milar to the op- amp, but w ith two outputs ,

the instrumentation amplifier (usually built from three op-amps ,

the isolation amplifier (similar to the instrumentation amplifier,

but with tolerance to common-mode 7oltages that would destroy

an ordinary op-amp , and negati7e feedbac% amplifier (usually

b ui lt f ro m o ne or more o p-amp s and a r es is ti 7e f eedb ac%

networ% !

"he circuit symbol for an op-amp is shown to the right, where: ! A: non-in7erting input ! W: in7erting input ! ou t : output

! ;A : positi7e power supply

! ;W: negati7e power supply
http://en.wikipedia.org/wiki/Differential_amplifierhttp://en.wikipedia.org/wiki/Fully_differential_amplifierhttp://en.wikipedia.org/wiki/Fully_differential_amplifierhttp://en.wikipedia.org/wiki/Instrumentation_amplifierhttp://en.wikipedia.org/wiki/Isolation_amplifierhttp://en.wikipedia.org/wiki/Negative_feedback_amplifierhttp://en.wikipedia.org/wiki/Differential_amplifierhttp://en.wikipedia.org/wiki/Fully_differential_amplifierhttp://en.wikipedia.org/wiki/Fully_differential_amplifierhttp://en.wikipedia.org/wiki/Instrumentation_amplifierhttp://en.wikipedia.org/wiki/Isolation_amplifierhttp://en.wikipedia.org/wiki/Negative_feedback_amplifier


43/46

"he power supply pins ( ! ;A and ! ;W can be labeled in different

ways! )ften these pins are left out of the diagram for clarity, and

the power configuration is described or assumed from the cir cuit!

%> :


44/46

gain bloc%s and all the con7entional op amp circuits which now can

be more easi ly implemented in single power supply systems! >or

examp le , the L 8' .2 ser ie s can b e d irec tly o pera ted o ff o f the

standard A.0 power supply 7oltage which is used in digital systemsand will easi ly pro7ide the re6uired in terface electronics without

re6uiring the additional ?'.0 power supplies!

"he L8*.2 and L8 4& are a7ailable in a chip si ed pac%age (2-

$ump micro ;8D using #ational s micro ;8D pac%age technology !

2ni ue Characteristics

n the l inear mode the input common-mode 7ol tage rangeincludes g round and the ou tput 7o ltage can a lso swing to

ground, e7en though operated from only a single power supply

7oltage! "he unity gain cross fre6uency is temperature compensated!

"he input bias current is also temperature compensated!

@dvantages "wo internally compensated op amps

Eliminates need for dual supplies Bllows direct sensing near #D and 0)I" also goes to #D

Compatible with all forms of logic

Mower drain suitable for battery operation

Features B7ailable in 2-$ump micro ;8D chip si ed pac%age,

nternally fre6uency compensated for unity gain

Large dc 7oltage gain: '&& d$


45/46

3ide bandwidth (unity gain : ' 8 (temperature

compensated 3ide power supply range:

[ ;ingle supply: *0 to * 0 [ or dual supplies: ?'! .0 to ?'/0

0e ry lo w s up ply c ur re nt d ra in ( .& & FB [ es se nt ia lly

independent of supply 7oltage Low input offset 7oltage: m0

nput common-mode 7oltage range includes ground

Different ia l input 7ol tage range e6ual to the power supply

7oltage Large output 7oltage swing

?ther applications

audio- and 7ideo-fre6uency pre-amplifiers and buffers differential amplifiers differentiators and integrators filters

precision rectifiers precision pea% detectors 7oltage and current regulators analog calculators analog-to-digital con7erters digital-to-analog con7erters
http://en.wikipedia.org/wiki/Preamplifierhttp://en.wikipedia.org/wiki/Buffer_amplifierhttp://en.wikipedia.org/wiki/Differential_amplifierhttp://en.wikipedia.org/wiki/Differentiatorhttp://en.wikipedia.org/wiki/Integratorhttp://en.wikipedia.org/wiki/Filter_(signal_processing)http://en.wikipedia.org/wiki/Rectifierhttp://en.wikipedia.org/wiki/Peak_detectorhttp://en.wikipedia.org/wiki/Voltage_regulatorhttp://en.wikipedia.org/wiki/Analog_to_digital_converterhttp://en.wikipedia.org/wiki/Digital_to_analog_converterhttp://en.wikipedia.org/wiki/Preamplifierhttp://en.wikipedia.org/wiki/Buffer_amplifierhttp://en.wikipedia.org/wiki/Differential_amplifierhttp://en.wikipedia.org/wiki/Differentiatorhttp://en.wikipedia.org/wiki/Integratorhttp://en.wikipedia.org/wiki/Filter_(signal_processing)http://en.wikipedia.org/wiki/Rectifierhttp://en.wikipedia.org/wiki/Peak_detectorhttp://en.wikipedia.org/wiki/Voltage_regulatorhttp://en.wikipedia.org/wiki/Analog_to_digital_converterhttp://en.wikipedia.org/wiki/Digital_to_analog_converter


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