Currency Counting Machine With Fake Note Detection Project Report

Currency Counting Machine with Fake Note Detection

1. INTRODUCTION

The currency counting machine or CCM is one of the miracle of the science. The CCM

works on the principle on the breadth of the bundle of currency and there in an roller which

has rods in an continuous pattern and the roller moves these rods with a particular speed.

The speed remains constant as like in the ATM machine counting machine and these

rollers moves on the bundle of the currency and just move out the single currency one by

one at a constant and high speed and there is an transducers which detect that how many

single currency has passed out in front of it.

FIG- 1 500 rupees note with its various real identification mark.

Different range of counting machines like Basic Note counter, Intelligent Counting cum

counterfeit detection machines and Hi Speed Heavy duty cash counting machine are

available to suit different type of customers. Highly dependable and ideal for Banks, Big &

small business houses, Traders, retailers, jewellers and almost all types of business

establishment can use them according to their suitability.

IEC-CET/2008-2012 Page 1


The machine meant for detection of fake notes as prime function invariably should be

capable of not allowing any fake note to pass as genuine. It is possible only with the

detectors specially developed considering the large number of intricacies concerning to

Indian notes

The kind of machines Indian Banks at cash counters needed are the machine which can

verify not only the images but also can check the chemical and physical properties of

papers, inks, resins and other materials used in production of note. The machine should be

capable of not allowing any fake note to pass as genuine. It is possible only with the

detectors specially developed considering the large number of intricacies concerning to

Indian notes



2. LITERATURE REVIEW

Currency Counter provides a fast, efficient and accurate way to count stacks of currency.

Some models detect counterfeit bills either magnetically and/or using ultraviolet light.

Ultra Violet Light Detector is used in Currency counters. Currency created by a color

copier or printer produces an image that rests on the surface of paper that can easily be

seen when UV light is placed over it.

FIG- 2 A 500 rupees note under UV rays.

Tiny particles of toner outside the image can also be easily seen with a UV light. Bill

counters and counterfeit detectors have a UV light built into the machine. If a counterfeit

bill is run through the machine, an alarm or light will alert you that the banknote is

counterfeit. Magnetic sensors: Magnetic sensors run over each bill and are designed to

search for certain components of banknotes that cannot be seen by the naked eye.

Machines automatically detect and match the piece against the already-programmed

components of legitimate bills. When a suspicious note is found, the operator is notified

immediately.



FIG- 3 Noting the discrepancy.

Different range of counting machines like Basic Note counter, Intelligent Counting cum

counterfeit detection machines and Hi Speed Heavy duty cash counting machine

Highly dependable and ideal for Banks, Big & small business houses, Traders, retailers,

jewellers and almost all types of business establishment…

2.1 COUNTERFEITING TECHNIQUES

Counterfeiting, of whatever kind, has been occurring ever since humans grasped the

concept of valuable items, and there has been an ongoing race between certifier (banks, for

example) and counterfeiter ever since.



First-Line Inspection Methods

Varied-Density Watermarks

Ultraviolet Fluorescence

Intaglio Printing

Microtext

Holograms and Kinegrams (DOVIDs/ISIS)

Second-Line Inspection Methods

Isocheck/Isogram

Fibre-Based Certificates of Authenticity

Colour and Feature Analysis

First-Line Inspection Methods

First-line inspection methods are used on-the-spot by vendors and retailers to determine, at

best guess, the authenticity of currency being exchanged. The disadvantages of these

methods are that they are generally easier to counterfeit than second-line inspection

characteristics, since they’re just as visible to the counterfeiter as to the verifier, and the

methods used to apply them are usually inexpensive. However, the visibility of these

features means that the general population is aware of the security measures and can spot

many fraudulent notes quickly.

Varied-Density Watermarks

By varying the density of the paper a banknote is printed on in a controlled manner, thin

watermarks can be applied. These are visible when a bright light shines onto the rear of

banknote, and the varied paper density causes varying intensities of light to pass through,

causing the watermarked image to appear on the other side of the note.

Ultraviolet Fluorescence

Embedding fluorescent fibers into the paper, or printing ultra-violet ink onto the paper,

creates a form of optical verification easily used at counters, checkouts, etc. By exposing



the note to ultra-violet light, the ink or fibers fluoresce, revealing a coloured pattern not

visible under natural light.

Intaglio Printing

This gives a more complex and reliable first-line inspection method, since it is the printing

process itself that serves to vouch for the authenticity of the document. The note is

subjected to a high-pressure printing process that strengthens and slightly raises the paper’s

surface structure. Using different alignments of lines printed in this manner, a latent image

can be produced which changes appearance depending on the angle at which the note is

viewed. This method can also be used with optically-variable ink to produce interference

which shows different spectral colours when viewed from different angles.

Micro text

It is very common for banknotes to have incredibly small text printed at much higher

resolutions than most commercial copiers, scanners or printers are capable of. When a

copying or scanning attempt is made, the insufficient resolution causes the text to become

illegibly blurred, announcing the illegitimacy of the note. This method requires specialised

printing equipment but ultimately adds very little cost to the manufacture of the currency.

Holograms and Kin grams (DOVIDs/ISIS)

These techniques are becoming more and more regularly used in modern anti-

counterfeiting measures, once used mostly on credit/debit cards but now increasingly on

new bank notes and cheques. In producing diffractive optically-variable image devices

(DOVIDs), iridescent foils are added to the printed currency usually after printing. Kin

grams and holograms used in DOVIDs are produced by embossing micro profiles with

thermoplastic films.

The hologram itself is applied using the interference of light from different sources in a

specific pattern, and kin grams are produced with achromatic and polarisation effects. The

result is a seemingly 3D full-colour image when illuminated from different angles. ISIS

uses stacked quantities of thin films to create a similar effect, with each layer having

different refractive properties. The refraction of light when viewed is such that a spectral



pattern has been extracted and a full-colour image is produced which varies under different

viewing angles.

Second-Line Inspection Methods

A second-line inspection method is one that cannot be verified by the naked eye alone, and

requires an extra device to perform a verification function. These are more secure and

harder to counterfeit than visual methods, but the extra security adds extra cost at both the

manufacturing and verification ends.

Isocheck/Isogram

Related to intaglio printing (described above), these methods rely on a specific pattern of

dots and/or lines to cause a moiré pattern when printed or scanned. Hidden watermarks can

also be applied in these patterns such that when a special filter is placed between the

viewer and the note, the hidden verification is revealed and verifies the note as genuine.

Fibre-Based Certificates of Authenticity

Based on the characteristics of fibre-optic light transmission, this method makes use of

unique configurations of fibres embedded in the paper. Using a scanner to illuminate one

end of an embedded fibre, the other corresponding of that fibre will become illuminated.

By using the position of both illuminated ends (the one deliberately illuminated, and the

one illuminated as a result), the certifier has a “fibre signature”.

This string can then be converted into a bit string and combined with any extra data that is

required (e.g. value, serial number, source, etc.). This is in turn combined with a

cryptographic hash of itself and is signed using a private key, with the corresponding

public key made available. The final result of these steps can then be encoded onto the

banknote (this method is suitable for certifying a wide range of other documents too) in the

form of a barcode or verification number of some kind.

Verifying the authenticity merely involves inverting the above process. The control

number is verified using the public key corresponding to the private key initially used. The

hash function is inverted and the original data string extracted. The note is then scanned

using the same fibre illumination method described above, and if the extracted data



matches the scanning observations, the document is genuine. This technique can add a

large cost to the manufacturing process of banknotes, but is highly secure and very difficult

to illegitimately replicate. It may be excessive for smaller-value currencies, but for large-

value notes, cheques or money orders this method provides a guarantee of the authenticity

of the claim.

Colour and Feature Analysis

Several image-processing software packages now include a secret detection algorithm to

prevent banknotes from being manipulated in their applications. Possibly by searching for

a specific geometric pattern—five 1mm-large circles arranged like a four-pronged star is

the primary candidate, visible in Euro notes, pounds sterling notes and older now-obsolete

European currency—they classify images of banknotes and refuse any further processing.

Touch & Feel Inspection & Visual Inspection

In spite of such high complications involved with the notes whether genuine or fake it has

been largely observed that validity of notes has been checked by the cashiers

simultaneously while manual counting.

However the human aptitudes of visual & touch feel verification with or without handy

tools is having large numbers of natural limitations, not enough to serve the purpose of

detection at cash counters, as there have been many invisible, high end & “difficult to

forge” security features on the valid notes which invariably are supposed to be examined

accurately while verifying validity on the notes seems to have remain unchecked, requiring

highly sophisticated machine to examine the intricacies of security features of the valid

notes.

2.2 ESTIMATED EXPENDITURE

Although estimating the total expenditure for a project of this nature is a mean task in

itself, we try to present the facts in as comprehensive a manner as possible.

Following is a list of the hardware and processes used in the project along with their costs.



S.No. Name of device Quantity Cost per unit Total cost

1 AT89c51 1 40 40

2 LCD 1 250 250

3 DC Motor 1 400 400

5 Capacitor 6 2 12

6 Resistor 6 1 6

9 12 V Battery 1 800 800

11 Relay 7 35 105

12 ULN2003A 1 15 15

13 7805 1 10 15

14 Switch 2 2 4

Security Features of Indian Banknotes

Watermark

Security Thread

Latent Image

Microlettering

Intaglio

Identification Mark

Fluorescence

Optically Variable Ink

See through Register



Watermark

The Mahatma Gandhi Series of banknotes contain the Mahatma Gandhi watermark with a

light and shade effect and multi-directional lines in the watermark windowThere is also

the watermark of the price of currency it’s visible in presence of light & glow in uv.

Security Thread

Rs.1000 notes introduced in October 2000 contain a readable, windowed security thread

alternately visible on the obverse with the inscriptions ‘Bharat’ (in Hindi), ‘1000’ and

‘RBI’, but totally embedded on the reverse. The Rs.500 and Rs.100 notes have a security

thread with similar visible features and inscription ‘Bharat’ (in Hindi), and ‘RBI’.

When held against the light, the security thread on Rs.1000, Rs.500 and Rs.100 can be

seen as one continuous line. The Rs.5, Rs.10, Rs.20 and Rs.50 notes contain a readable,

fully embedded windowed security thread with the inscription ‘Bharat’ (in Hindi), and

‘RBI’. The security thread appears to the left of the Mahatma's portrait. Notes issued prior

to the introduction of the Mahatma Gandhi Series have a plain, non-readable fully

embedded security thread.

Latent image

On the obverse side of Rs.1000, Rs.500, Rs.100, Rs.50 and Rs.20 notes, a vertical band on

the right side of the Mahatma Gandhi’s portrait contains a latent image showing the

respective denominational value in numeral. The latent image is visible only when the note

is held horizontally at eye level.

Microlettering

This feature appears between the vertical band and Mahatma Gandhi portrait. It contains

the word ‘RBI’ in Rs.5 and Rs.10. The notes of Rs.20 and above also contain the

denominational value of the notes in microletters. This feature can be seen better under a

magnifying glass



Intaglio Printing

The portrait of Mahatma Gandhi, the Reserve Bank seal, guarantee and promise clause,

Ashoka Pillar Emblem on the left, RBI, Governor's signature are printed in intaglio i.e. in

raised prints, which can be felt by touch, in Rs.20, Rs.50, Rs.100, Rs.500 and Rs.1000

notes.

Identification Mark

A special feature in intaglio has been introduced on the left of the watermark window on

all notes except Rs.10/- note. This feature is in different shapes for various denominations

(Rs. 20-Vertical Rectangle, Rs.50-Square, Rs.100-Triangle, Rs.500-Circle, Rs.1000-

Diamond) and helps the visually impaired to identify the denomination.

Fluorescence

Number panels of the notes are printed in fluorescent ink. The notes also have optical

fibers. Both can be seen when the notes are exposed to ultra-violet lamp. When there is

fake note it’s letter and mainly the numeric values all are irregular in shape..For a genuine

currency note, the number will be regular and when scrutinized against ultra violet rays,

the letter printed with fluorescent ink shine ,for fake note number will be comparatively

smaller as compared the original one..

Optically Variable Ink

This is a new security feature incorporated in the Rs.1000 and Rs.500 notes with

revised color scheme introduced in November 2000. The numeral 1000 and 500 on the

obverse of Rs.1000 and Rs.500 notes respectively is printed in optically variable ink viz., a

colour-shifting ink. The colour of the numeral 1000/500 appears green when the note is

held flat but would change to blue when the note is held at an angle.

See through Register

The small floral design printed both on the front (hollow) and back (filled up) of the note

in the middle of the vertical band next to the Watermark has an accurate back to back

registration. The design will appear as one floral design when seen against the light.



2.3 RBI GUIDELINES CONCERNING TO FAKE NOTE

DETECTION

It has necessitated for the Banks to deploy such authenticators which can support Banks to

comply RBI guidelines concerning to fake notes detection. The machine should be 100%

accurate in detection of Fake Notes. No fake note should pass as genuine in all case, have

been the bottom lines for any machine which functions as authenticator unless the note is

of extremely bad quality.

The extremely bad quality of note should be rejected by the authenticators with error codes

“No judgment” since the TRUE validity of such notes due to bad quality can not be judged

except at forensic lab. Such bad quality of notes generally reflects overlapping of features

of genuine & fake note creating, uncertainty of accurate validation even though best

authenticators for not permitting deep scanning of such notes. No sorter or Currency

Verification Systems (CVS) possesses any separate pocket to separate fake notes except

pockets for separating notes of opposite criterion. Sorters just separate the notes which are

not matching with the sorting criterion set in the machine. Fit & unfit, oriented and non

oriented, face up & face down.

There are pockets for collecting opposite criterion notes but no separate pocket have been

there for collection of fake notes; although it has been claimed that sorters are best suited

for fake note detection. It is wrongly presumed that the opposite criterion pocket collect the

fake notes. There is every chance that fake notes matching the various set criterion as may

be set in the sorter will pass under such set criterion for many technical reasons.

The functions of AUTHENTICATION & SORTING are two mutually exclusive functions

carrying wide difference in their respective weight ages and money values involved in the

respective operations. Imperfect quality sorting of notes does not attracts loss of value

while as passing fake notes as genuine attracts direct loss of value and criminal procedures

under I PC and other provisions. Authentication function needs detailed analyses of

chemical & physical properties of Bank Note Paper, varied inks, resins, security threads,

chemical used in the printing process.



It includes checking of all security features on the face of the notes images, emblems,

portraits, logos, colours, designs, texts, covert and overt features etc Most accurate

authenticity check only is possible if the notes are checked length wise. Authenticators

must have capacity to scan the notes length wise back to back, to match with the large

number of length wise prints, texts, emblems, portraits, horizontal lines; patterns etc for

checking the continuity of such security features while as sorters are checking the notes

width wise loosing the continuity of scanning various lengthwise security features.

Most of the security features in any currency types are designed length wise and hence

without lengthwise scanning of the notes scientifically difficult to obtained 100% accuracy

during the detection of fake notes. Most of the note counting /sorting machines in the

international market have failed to offer 100% authentication accuracy for not having

facility to check notes length wise and scanning the notes width wise, as also have been

dependent on light & image based technology scanning the notes width wise, which have

been scientifically unfeasible. It is scientifically impossible to check highly complicated,

inter related security aspects in the notes with inter related large numbers of permutations

and combinations of each and every elements that constitutes a Genuine notes at the high

speeds of sorters which sorts the notes with Image & light sensor based technology.

Speed kills the authentication accuracy by note getting scientific time to pip into the

minute differences between genuine and fabricated security features. At the most can

detect very poorly fabricated notes but not skilfully fabricated fake notes being pumped in

our country by other state supports that have been having total infrastructures and notes

printing technology Authentication can only be carried out with high end light cum Image

cum digital technology. The fastest fake note detector that is available in the international

market takes minimum 3 seconds for thorough checking of notes. Such machines mostly

have facility for single note manual feedings.



3. MATERIALS AND METHODOLOGY

3.1 METHODOLOGY

The whole system is controlled by the microcontroller (AT89c51). The currency counting

machine or CCM .The CCM works on the principle on the breadth of the bundle of

currency and there in an roller which has rods in an continuous pattern and the roller

moves these rods with a particular speed

and these rollers moves on the bundle of the currency and just move out the single

currency one by one at a constant and high speed and there is an transducers which detect

that how many single currency has passed out in front of it.

FIG- 4- Complete circuit diagram.



3.2 COMPONENTS/PARTS USED:

AT89C51

LCD

DC motors (3)

Drill Motor

Relays

Transformer

Diodes

Resistors

Capacitors

A brief description of these components follows.

AT89C51 microcontroller

The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4

Kbytes of Flash Programmable and Erasable Read Only Memory (PEROM). The

device is manufactured using Atmel’s high density non-volatile memory technology

and is compatible with the industry standard MCS-51Ô instruction set and pin out.

The on-chip Flash allows the program memory to be reprogrammed in-system or by

a conventional non-volatile memory programmer. By combining a versatile 8-bit CPU

with Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputer

which provides a highly flexible and cost effective solution to many embedded control

applications.

The Intel MCS-51 (commonly referred to as 8051) is a Harvard architecture, single chip

microcontroller (µC) series which was developed by Intel in 1980 for use in embedded

systems. Intel's original versions were popular in the 1980s and early 1990s. While Intel no

longer manufactures the MCS-51, binary compatible derivatives remain popular today. In

addition to these physical devices, several companies also offer MCS-51 derivatives as IP

cores for use in FPGAs or ASICs designs.



Intel's original MCS-51 family was developed using NMOS technology, but later versions,

identified by a letter C in their name (e.g., 80C51) used CMOS technology and consumed

less power than their NMOS predecessors. This made them more suitable for battery-

powered devices.

FIG- 5 AT89C51 microcontroller.

AT89C51

Important features and applications of 8051 micro architecture.

The 8051 architecture provides many functions (CPU, RAM, ROM, I/O, interrupt logic,

timer, etc.) in a single package

8-bit ALU, Accumulator and 8-bit Registers; hence it is an 8-bit microcontroller

8-bit data bus – It can access 8 bits of data in one operation

16-bit address bus – It can access 216 memory locations – 64 KB (65536 locations) each

of RAM and ROM

On-chip RAM – 128 bytes (data memory)

On-chip ROM – 4 kByte (program memory)

Four byte bi-directional input/output port

UART (serial port)

Two 16-bit Counter/timers

Two-level interrupt priority

Power saving mode (on some derivatives)

One particularly useful feature of the 8051 core was the inclusion of a boolean processing

engine which allows bit-level boolean logic operations to be carried out directly and



efficiently on select internal registers and select RAM locations. This advantageous feature

helped cement the 8051's popularity in industrial control applications because it reduced

code size by as much as 30%. Another valued feature is the including of four bank

selectable working register sets which greatly reduce the amount of time required to

complete an interrupt service routine.

With a single instruction the 8051 can switch register banks as opposed to the time

consuming task of transferring the critical registers to the stack or designated RAM

locations. These registers also allowed the 8051 to quickly perform a context switch which

is essential for time sensitive real-time applications.The MCS-51 UARTs make it simple to

use the chip as a serial communications interface. External pins can be configured to

connect to internal shift registers in a variety of ways, and the internal timers can also be

used, allowing serial communications in a number of modes, both synchronous and

asynchronous. Some modes allow communications with no external components.

A mode compatible with an RS-485 multi-point communications environment is

achievable, but the 8051's real strength is fitting in with existing ad-hoc protocols (e.g.,

when controlling serial-controlled devices).Once a UART, and a timer if necessary, have

been configured, the programmer needs only to write a simple interrupt routine to refill the

send shift register whenever the last bit is shifted out by the UART and/or empty the full

receive shift register (copy the data somewhere else). The main program then performs

serial reads and writes simply by reading and writing 8-bit data to stacks.

MCS-51 based microcontrollers typically include one or two UARTs, two or three timers,

128 or 256 bytes of internal data RAM (16 bytes of which are bit-addressable), up to 128

bytes of I/O, 512 bytes to 64 kB of internal program memory, and sometimes a quantity of

extended data RAM (ERAM) located in the external data space. The original 8051 core ran

at 12 clock cycles per machine cycle, with most instructions executing in one or two

machine cycles. With a 12 MHz clock frequency, the 8051 could thus execute 1 million

one-cycle instructions per second or 500,000 two-cycle instructions per second.

Enhanced 8051 cores are now commonly used which run at six, four, two, or even one

clock per machine cycle, and have clock frequencies of up to 100 MHz, and are thus



capable of an even greater number of instructions per second. All SILabs, some Dallas and

a few Atmel devices have single cycle cores.Features of the modern 8051 include built-in

reset timers with brown-out detection, on-chip oscillators, self-programmable Flash ROM

program memory, built-in external RAM, extra internal program storage, bootloader code

in ROM, EEPROM non-volatile data storage, I²C, SPI, and USB host interfaces, CAN or

LIN bus, PWM generators, analog comparators, A/D and D/A converters, RTCs, extra

counters and timers, in-circuit debugging facilities, more interrupt sources, and extra

power saving modes.In many engineering schools the 8051 microcontroller is used in

introductory microcontroller courses.

Memory architecture

The MCS-51 has four distinct types of memory – internal RAM, special function registers,

program memory, and external data memory. Internal RAM (IRAM) is located from

address 0 to address 0xFF. IRAM from 0x00 to 0x7F can be accessed directly, and the

bytes from 0x20 to 0x2F are also bit-addressable. IRAM from 0x80 to 0xFF must be

accessed indirectly, using the @R0 or @R1 syntax, with the address to access loaded in R0

or R1.

Special function registers (SFR) are located from address 0x80 to 0xFF, and are accessed

directly using the same instructions as for the lower half of IRAM. Some of the SFR's are

also bit-addressable. Program memory (PMEM, though less common in usage than IRAM

and XRAM) is located starting at address 0. It may be on- or off-chip, depending on the

particular model of chip being used. Program memory is read-only, though some variants

of the 8051 use on-chip flash memory and provide a method of re-programming the

memory in-system or in-application. Aside from storing code, program memory can also

store tables of constants that can be accessed by MOVC A, @DPTR, using the 16-bit

special function register DPTR.

External data memory (XRAM) also starts at address 0. It can also be on- or off-chip; what

makes it "external" is that it must be accessed using the MOVX (Move external)

instruction. Many variants of the 8051 include the standard 256 bytes of IRAM plus a few

KB of XRAM on the chip. If more XRAM is required by an application, the internal

XRAM can be disabled, and all MOVX instructions will fetch from the external bus.



FIG- 6 INTEL 8051 block diagram.

Relay

A relay is an electrically operated switch. Many relays use an electromagnet to operate a

switching mechanism mechanically, but other operating principles are also used. Relays

are used where it is necessary to control a circuit by a low-power signal (with complete

electrical isolation between control and controlled circuits), or where several circuits must

be controlled by one signal. The first relays were used in long distance telegraph circuits,

repeating the signal coming in from one circuit and re-transmitting it to another. Relays

were used extensively in telephone exchanges and early computers to perform logical

operations.

A type of relay that can handle the high power required to directly control an electric

motor or other loads is called a contactor. Solid-state relays control power circuits with no

moving parts, instead using a semiconductor device to perform switching. Relays with

calibrated operating characteristics and sometimes multiple operating coils are used to

protect electrical circuits from overload or faults; in modern electric power systems these

functions are performed by digital instruments still called "protective relays".

Relay is a common, simple application of electromagnetism. It uses an electromagnet

made from an iron rod wound with hundreds of fine copper wire. When electricity is



applied to the wire, the rod becomes magnetic. A movable contact arm above the rod is

then pulled toward the rod until it closes a switch contact. When the electricity is removed,

a small spring pulls the contract arm away from the rod until it closes a second switch

contact. By means of relay, a current circuit can be broken or closed in one circuit as a

result of a current in another circuit.

Basic design and operation

Small "cradle" relay often used in electronics. The "cradle" term refers to the shape of the

relay's armature. A simple electromagnetic relay consists of a coil of wire wrapped around

a soft iron core, an iron yoke which provides a low reluctance path for magnetic flux, a

movable iron armature, and one or more sets of contacts (there are two in the relay

pictured). The armature is hinged to the yoke and mechanically linked to one or more sets

of moving contacts. It is held in place by a spring so that when the relay is de-energized

there is an air gap in the magnetic circuit. In this condition, one of the two sets of contacts

in the relay pictured is closed, and the other set is open. Other relays may have more or

fewer sets of contacts depending on their function. The relay in the picture also has a wire

connecting the armature to the yoke. This ensures continuity of the circuit between the

moving contacts on the armature, and the circuit track on the printed circuit board (PCB)

via the yoke, which is soldered to the PCB.

When an electric current is passed through the coil it generates a magnetic field that

activates the armature, and the consequent movement of the movable contact(s) either

makes or breaks (depending upon construction) a connection with a fixed contact. If the set

of contacts was closed when the relay was de-energized, then the movement opens the

contacts and breaks the connection, and vice versa if the contacts were open. When the

current to the coil is switched off, the armature is returned by a force, approximately half

as strong as the magnetic force, to its relaxed position. Usually this force is provided by a

spring, but gravity is also used commonly in industrial motor starters. Most relays are

manufactured to operate quickly. In a low-voltage application this reduces noise; in a high

voltage or current application it reduces arcing.

When the coil is energized with direct current, a diode is often placed across the coil to

dissipate the energy from the collapsing magnetic field at deactivation, which would



otherwise generate a voltage spike dangerous to semiconductor circuit components. Some

automotive relays include a diode inside the relay case.

Alternatively, a contact protection network consisting of a capacitor and resistor in series

(snubber circuit) may absorb the surge. If the coil is designed to be energized with

alternating current (AC), a small copper "shading ring" can be crimped to the end of the

solenoid, creating a small out-of-phase current which increases the minimum pull on the

armature during the AC cycle.[1]A solid-state relay uses a thyristor or other solid-state

switching device, activated by the control signal, to switch the controlled load, instead of a

solenoid. An optocoupler (a light-emitting diode (LED) coupled with a photo transistor)

can be used to isolate control and controlled circuits.

FIG- 7 Relay switch

Relay switch

Crystal Oscillators

A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of

a vibrating crystal of piezoelectric material to create an electrical signal with a very precise

frequency. This frequency is commonly used to keep track of time (as in quartz

wristwatches), to provide a stable clock signal for digital integrated circuits, and to

stabilize frequencies for radio transmitters and receivers. The most common type of

piezoelectric resonator used is the quartz crystal, so oscillator circuits designed around

them became known as "crystal oscillators."

Quartz crystals are manufactured for frequencies from a few tens of kilohertz to tens of

megahertz. More than two billion (2×109) crystals are manufactured annually. Most are



used for consumer devices such as wristwatches, clocks, radios, computers, and cell

phones. Quartz crystals are also found inside test and measurement equipment, such as

counters, signal generators, and oscilloscopes.

Crystal oscillators are oscillators where the primary frequency determining element is a

quartz crystal. Because of the inherent characteristics of the quartz crystal the crystal

oscillator may be held to extreme accuracy of frequency stability. Temperature

compensation may be applied to crystal oscillators to improve thermal stability of the

crystal oscillator. Crystal oscillators are usually, fixed frequency oscillators where stability

and accuracy are the primary considerations. For example it is almost impossible to design

a stable and accurate LC oscillator for the upper HF and higher frequencies without

resorting to some sort of crystal control.

Operation

A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a

regularly ordered, repeating pattern extending in all three spatial dimensions.

Almost any object made of an elastic material could be used like a crystal, with appropriate

transducers, since all objects have natural resonant frequencies of vibration. For example,

steel is very elastic and has a high speed of sound. It was often used in mechanical filters

before quartz. The resonant frequency depends on size, shape, elasticity, and the speed of

sound in the material. High-frequency crystals are typically cut in the shape of a simple,

rectangular plate. Low-frequency crystals, such as those used in digital watches, are

typically cut in the shape of a tuning fork.

For applications not needing very precise timing, a low-cost ceramic resonator is often

used in place of a quartz crystal.When a crystal of quartz is properly cut and mounted, it

can be made to distort in an electric field by applying a voltage to an electrode near or on

the crystal. This property is known as piezoelectricity. When the field is removed, the

quartz will generate an electric field as it returns to its previous shape, and this can

generate a voltage. The result is that a quartz crystal behaves like a circuit composed of an

inductor, capacitor and resistor, with a precise resonant frequency.

Quartz has the further advantage that its elastic constants and its size change in such a way

that the frequency dependence on temperature can be very low. The specific characteristics



will depend on the mode of vibration and the angle at which the quartz is cut (relative to its

crystallographic axes). Therefore, the resonant frequency of the plate, which depends on its

size, will not change much, either.

This means that a quartz clock, filter or oscillator will remain accurate. For critical

applications the quartz oscillator is mounted in a temperature-controlled container, called a

crystal oven, and can also be mounted on shock absorbers to prevent perturbation by

external mechanical vibrations.

Crystal structures and materials

The most common material for oscillator crystals is quartz. At the beginning of the

technology, natural quartz crystals were used; now synthetic crystalline quartz grown by

hydrothermal synthesis is predominant due to higher purity, lower cost, and more

convenient handling. One of the few remaining uses of natural crystals is for pressure

transducers in deep wells. During World War II and for some time afterwards, natural

quartz was considered a strategic material by the USA. Large crystals were imported from

Brazil. Raw "lascas", the source material quartz for hydrothermal synthesis, are imported

to USA or mined locally by Coleman Quartz. The average value of as-grown synthetic

quartz in 1994 was USD60/kg.

Two types of quartz crystals exist: left-handed and right-handed, differing in the optical

rotation but identical in other physical properties. Both left and right-handed crystals can

be used for oscillators, if the cut angle is correct. In manufacture, right-handed quartz is

generally used. The SiO4 tetrahedrons form parallel helixes; the direction of twist of the

helix determines the left- or right-hand orientation. The helixes are aligned along the z-axis

and merged together, sharing atoms. The mass of the helixes forms a mesh of small and

large channels parallel to the z-axis; the large ones are large enough to allow some

mobility of smaller ions and molecules through the crystal.

Quartz exists in several phases. At 573 °C at 1 atmosphere (and at higher temperatures and

higher pressures) the α-quartz undergoes quartz inversion, transforms reversibly to β-

quartz. The reverse process however is not entirely homogeneous and crystal twinning

occurs. Care has to be taken during manufacture and processing to avoid the phase



transformation. Other phases, e.g. the higher-temperature phases tridymite and cristobalite,

are not significant for oscillators. All quartz oscillator crystals are the α-quartz type.

Infrared spectrophotometry is used as one of the methods for measuring the quality of the

grown crystals. The wavenumbers 3585, 3500 and 3410 cm−1 are commonly used. The

measured value is based on the absorption bands of the OH radical and the infrared Q

value is calculated. The electronic grade crystals, grade C, have Q of 1.8 million or above;

the premium grade B crystals have Q of 2.2 million, and special premium grade A crystals

have Q of 3.0 million. The Q value is calculated only for the z region; crystals containing

other regions can be adversely affected. Another quality indicator is the etch channel

density; when the crystal is etched, tubular channels are created along linear defects. For

processing involving etching, e.g. the wristwatch tuning fork crystals, low etch channel

density is desirable. The etch channel density for swept quartz is about 10–100 and

significantly more for unswept quartz. Presence of etch channels and etch pits degrades the

resonator's Q and introduces nonlinearities. Quartz crystals can be grown for specific

purposes.

Crystals for AT-cut are the most common in mass production of oscillator materials; the

shape and dimensions are optimized for high yield of the required wafers. High-purity

quartz crystals are grown with especially low content of aluminium, alkali metal and other

impurities and minimal defects; the low amount of alkali metals provides increased

resistance to ionizing radiation. Crystals for wrist watches, for cutting the tuning fork

32768 Hz crystals, are grown with very low etch channel density. Crystals for SAW

devices are grown as flat; with large X-size seed with low etch channel density.

Special high-Q crystals, for use in highly stable oscillators, are grown at constant slow

speed and have constant low infrared absorption along the entire Z axis. Crystals can be

grown as Y-bar, with a seed crystal in bar shape and elongated along the Y axis, or as Z-

plate, grown from a plate seed with Y-axis direction length and X-axis width. The region

around the seed crystal contains a large number of crystal defects and should not be used

for the wafers.Crystals grow anisotropically; the growth along the Z axis is up to 3 times

faster than along the X axis. The growth direction and rate also influences the rate of

uptake of impurities. Y-bar crystals, or Z-plate crystals with long Y axis, have four growth



regions usually called +X, -X, Z, and S. The distribution of impurities during growth is

uneven; different growth areas contain different level of contaminants. The z regions are

the purest, the small occasionally present s regions are less pure, the +x region is yet less

pure, and the -x region has the highest level of impurities.

The impurities have negative impact on radiation hardness, susceptibility to twinning,

filter loss, and long and short term stability of the crystals. Different-cut seeds in different

orientations may provide other kinds of growth regions. The growth speed of the -x

direction is slowest due to the effect of adsorption of water molecules on the crystal

surface; aluminium impurities suppress growth in two other directions. The content of

aluminium is lowest in z region, higher in +x, yet higher in -x, and highest in s; the size of

s regions also grows with increased amount of aluminium present.

The content of hydrogen is lowest in z region, higher in +x region, yet higher in s region,

and highest in -x. Aluminium inclusions transform to colour centres with a gamma ray

irradiation, causing darkening of the crystal proportional to the dose and level of

impurities; presence of regions with different darkness reveals the different growth

regions. The dominant type of defect of concern in quartz crystals is the substitution of

Al(III) for Si(IV) atom in the crystal lattice. The aluminium ion has an associated

interstitial charge compensator present nearby, which can be a H+ ion (attached to the

nearby oxygen and forming a hydroxyl group, called Al-OH defect), Li+ ion, Na+ ion, K+

ion (less common), or an electron hole trapped in a nearby oxygen atom orbital. The

composition of the growth solution, whether it is based on lithium or sodium alkali

compounds, determines the charge compensating ions for the aluminium defects. The ion

impurities are of concern as they are not firmly bound and can migrate through the crystal,

altering the local lattice elasticity and the resonant frequency of the crystal. Other common

impurities of concern are e.g. iron(III) (interstitial), fluorine, boron(III), phosphorus(V)

(substitution), titanium(IV) (substitution, universally present in magmatic quartz, less

common in hydrothermal quartz), and germanium(IV) (substitution).

Sodium and iron ions can cause inclusions of aconite and elemeusite crystals. Inclusions of

water may be present in fast-grown crystals; interstitial water molecules are abundant near

the crystal seed. Another defect of importance is the hydrogen containing growth defect,



when instead of a Si-O-Si structure a pair of Si-OH HO-Si groups is formed; essentially a

hydrolyzed bond. Fast-grown crystals contain more hydrogen defects than slow-grown

ones. These growth defects source as supply of hydrogen ions for radiation-induced

processes and forming Al-OH defects. Germanium impurities tend to trap electrons created

during irradiation; the alkali metal cations then migrate towards the negatively charged

center and form a stabilizing complex. Matrix defects can be also present; oxygen

vacancies, silicon vacancies (usually compensated by 4 hydrogens or 3 hydrogens and a

hole), peroxy groups, etc. Some of the defects produce localized levels in the forbidden

band, serving as charge traps; Al(III) and B(III) typically serve as hole traps while electron

vacancies, titanium, germanium, and phosphorus atoms serve as electron traps. The

trapped charge carriers can be released by heating; their recombination is the cause of

thermoluminescence.

The mobility of interstitial ions depends strongly on temperature. Hydrogen ions are

mobile down to 10 K, but alkali metal ions become mobile only at temperatures around

and above 200 K. The hydroxyl defects can be measured by near-infrared spectroscopy.

The trapped holes can be measured by electron spin resonance. The Al-Na+ defects show

as an acoustic loss peak due to their stress-induced motion; the Al-Li+ defects do not form

a potential well so are not detectable this way. Some of the radiation induced defects

during their thermal annealing produce thermo luminescence; defects related to aluminium,

titanium, and germanium can be distinguished.

Swept crystals are crystals that have undergone a solid-state electro diffusion purification

process. Sweeping involves heating the crystal above 500 °C in a hydrogen-free

atmosphere, and the voltage gradient of at least 1 kilovolt/cm, for several (usually over 12)

hours. The migration of impurities and the gradual replacement of alkali metal ions with

hydrogen (when swept in air) or electron holes (when swept in vacuum) causes a weak

electric current through the crystal; decay of this current to a constant value signals end of

the process. The crystal is then left to cool, while the electric field is maintained. The

impurities are concentrated at the cathode region of the crystal, which is cut off afterwards

and discarded. Swept crystals have increased resistance to radiation, as the dose effects are

dependent on the level of alkali metal impurities; they are suitable for use in devices

exposed to ionizing radiation, e.g. for nuclear and space technology. Sweeping under



vacuum at higher temperatures and higher field strengths yields yet more radiation-hard

crystals. The level and character of impurities can be measured by infrared spectroscopy.

Quartz can be swept in both α and β phase; sweeping in β phase is faster, but the phase

transition may induce twinning. Twinning can be mitigated by subjecting the crystal to

compression stress in the X direction, or an AC or DC electric field along the X axis while

the crystal cools through the phase transformation temperature region.

Sweeping can be also used to introduce one kind of an impurity into the crystal. Lithium,

sodium, and hydrogen swept crystals are used for e.g. studying quartz behavior.Very small

crystals for high fundamental mode frequencies can be manufactured by photolithography.

Crystals can be adjusted to exact frequency by laser trimming. A technique used in the

world of amateur radio for slight decrease of the crystal frequency may be achieved by

exposing crystals with silver electrodes to vapours of iodine, which causes a slight mass

increase on the surface by forming a thin layer of silver iodide; such crystals however had

problematic long-term stability. Another method commonly used is electrochemical

increase or decrease of silver electrode thickness by submerging resonator in lapis solved

in water, citric acid in water, or water with salt, and using resonator as one electrode, and

small silver electrode as another.

By choosing direction of current, one can either increase or decrease mass of electrodes.

Details were published in "Radio" magazine (3/1978) by UB5LEV.Raising frequency by

scratching off parts of the electrodes is advised against, as this may damage the crystal and

lower its Q factor. Capacitor trimmers can be also used for frequency adjustment of the

oscillator circuit.

Some other piezoelectric materials than quartz can be employed; e.g. single crystals of

lithium tantalite, lithium niobate, lithium borate, berlinite, gallium arsenide, lithium

tetraborate, aluminium phosphate, bismuth germanium oxide, polycrystalline zirconium

titanate ceramics, high-alumina ceramics, silicon-zinc oxide composite, or dipotassium

tartrate; some materials may be more suitable for specific applications. An oscillator

crystal can be also manufactured by depositing the resonator material on the silicon chip

surface. Crystals of gallium phosphate, langasite, langanite and langanate are about 10



times more pullable than the corresponding quartz crystals, and are used in some VCXO

oscillators.

Resistors

Resistors (R), are the most commonly used of all electronic components, to the point

where they are almost taken for granted. There are many different resistor types available

with their principal job being to "resist" the flow of current through an electrical circuit, or

to act as voltage droppers or voltage dividers. They are "Passive Devices", that is they

contain no source of power or amplification but only attenuate or reduce the voltage signal

passing through them. When used in DC circuits the voltage drop produced is measured

across their terminals as the circuit current flows through them while in AC circuits the

voltage and current are both in-phase producing 0o phase shift.

Resistors produce a voltage drop across themselves when an electrical current flows

through them because they obey Ohm's Law, and different values of resistance produces

different values of current or voltage. This can be very useful in Electronic circuits by

controlling or reducing either the current flow or voltage produced across them. There are

many different Resistor Types and they are produced in a variety of forms because their

particular characteristics and accuracy suit certain areas of application, such as High

Stability, High Voltage, High Current etc., or are used as general purpose resistors where

their characteristics are less of a problem. Some of the common characteristics associated

with the humble resistor are; Temperature Coefficient, Voltage Coefficient, Noise,

Frequency Response, Power as well as Temperature Rating, Physical Size and Reliability.

In all Electrical and Electronic circuit diagrams and schematics, the most commonly used

resistor symbol is that of a "zigzag" type line with the value of its resistance given in

Ohms, Ω.

Capacitor

Just like the Resistor, the Capacitor or sometimes referred to as a Condenser is a passive

device, and one which stores energy in the form of an electrostatic field which produces a

potential (Static Voltage) across its plates. In its basic form a capacitor consists of two

parallel conductive plates that are not connected but are electrically separated either by air


http://www.electronics-tutorials.ws/resistor/res_1.html


or by an insulating material called the Dielectric. When a voltage is applied to these plates,

a current flows charging up the plates with electrons giving one plate a positive charge and

the other plate an equal and opposite negative charge. This flow of electrons to the plates is

known as the Charging Current and continues to flow until the voltage across the plates

(and hence the capacitor) is equal to the applied voltage Vc. At this point the capacitor is

said to be fully charged and this is illustrated below.

Capacitor Construction

FIG- 8 :Capacitor construction

The parallel plate capacitor is the simplest form of capacitor and its capacitance value is

fixed by the equal area of the plates and the distance or separation between them. Altering

any two of these values alters the the value of its capacitance and this forms the basis of

operation of the variable capacitors. Also, because capacitors store the energy of the

electrons in the form of an electrical charge on the plates the larger the plates and/or

smaller their separation the greater will be the charge that the capacitor holds for any given

voltage across its plates.

Liquid Crystal Display

A liquid crystal display (LCD) is a flat panel display, electronic visual display, or video

display that uses the light modulating properties of liquid crystals (LCs). LCs do not emit

light directly.



FIG- 9 A general purpose alphanumeric LCD, with two lines of 16 characters.

LCDs are used in a wide range of applications, including computer monitors, television,

instrument panels, aircraft cockpit displays, signage, etc. They are common in consumer

devices such as video players, gaming devices, clocks, watches, calculators, and

telephones. LCDs have replaced cathode ray tube (CRT) displays in most applications.

They are available in a wider range of screen sizes than CRT and plasma displays, and

since they do not use phosphors, they cannot suffer image burn-in. LCDs are, however,

susceptible to image persistence.

LCDs are more energy efficient and offer safer disposal than CRTs. Its low electrical

power consumption enables it to be used in battery-powered electronic equipment. It is an

electronically modulated optical device made up of any number of segments filled with

liquid crystals and arrayed in front of a light source (backlight) or reflector to produce

images in color or monochrome. The most flexible ones use an array of small pixels. The

earliest discovery leading to the development of LCD technology, the discovery of liquid

crystals, dates from 1888. By 2008, worldwide sales of televisions with LCD screens had

surpassed the sale of CRT units.

Overview



Each pixel of an LCD typically consists of a layer of molecules aligned between two

transparent electrodes, and two polarizing filters, the axes of transmission of which are (in

most of the cases) perpendicular to each other. With no actual liquid crystal between the

polarizing filters, light passing through the first filter would be blocked by the second

(crossed) polarizer.

The surface of the electrodes that are in contact with the liquid crystal material are treated

so as to align the liquid crystal molecules in a particular direction. This treatment typically

consists of a thin polymer layer that is unidirectionally rubbed using, for example, a cloth.

The direction of the liquid crystal alignment is then defined by the direction of rubbing.

Electrodes are made of the transparent conductor Indium Tin Oxide (ITO). The Liquid

Crystal Display is intrinsically a “passive” device, it is a simple light valve. The managing

and control of the data to be displayed is performed by one or more circuits commonly

denoted as LCD drivers.

Before applying an electric field, the orientation of the liquid crystal molecules is

determined by the alignment at the surfaces of electrodes. In a twisted nematic device (still

the most common liquid crystal device), the surface alignment directions at the two

electrodes are perpendicular to each other, and so the molecules arrange themselves in a

helical structure, or twist. This induces the rotation of the polarization of the incident light,

and the device appears grey. If the applied voltage is large enough, the liquid crystal

molecules in the center of the layer are almost completely untwisted and the polarization of

the incident light is not rotated as it passes through the liquid crystal layer. This light will

then be mainly polarized perpendicular to the second filter, and thus be blocked and the

pixel will appear black. By controlling the voltage applied across the liquid crystal layer in

each pixel, light can be allowed to pass through in varying amounts thus constituting

different levels of gray.

The optical effect of a twisted nematic device in the voltage-on state is far less dependent

on variations in the device thickness than that in the voltage-off state. Because of this,

these devices are usually operated between crossed polarizers such that they appear bright

with no voltage (the eye is much more sensitive to variations in the dark state than the

bright state). These devices can also be operated between parallel polarizers, in which case



the bright and dark states are reversed. The voltage-off dark state in this configuration

appears blotchy, however, because of small variations of thickness across the device.

Both the liquid crystal material and the alignment layer material contain ionic compounds.

If an electric field of one particular polarity is applied for a long period of time, this ionic

material is attracted to the surfaces and degrades the device performance. This is avoided

either by applying an alternating current or by reversing the polarity of the electric field as

the device is addressed (the response of the liquid crystal layer is identical, regardless of

the polarity of the applied field).

Displays for a small number of individual digits and/or fixed symbols (as in digital

watches, pocket calculators etc.) can be implemented with independent electrodes for each

segment. In contrast full alphanumeric and/or variable graphics displays are usually

implemented with pixels arranged as a matrix consisting of electrically connected rows on

one side of the LC layer and columns on the other side, which makes it possible to address

each pixel at the intersections. The general method of matrix addressing consists of

sequentially addressing one side of the matrix, for example by selecting the rows one-by-

one and applying the picture information on the other side at the columns row-by-row. For

details on the various matrix addressing schemes see Passive-matrix and active-matrix

addressed LCDs.

Voltage Regulator

The 78xx (sometimes LM78xx) is a family of self-contained fixed linear voltage regulator

integrated circuits. The 78xx family is commonly used in electronic circuits requiring a

regulated power supply due to their ease-of-use and low cost. For ICs within the family,

the xx is replaced with two digits, indicating the output voltage (for example, the 7805 has

a 5 volt output, while the 7812 produces 12 volts). The 78xx line are positive voltage

regulators: they produce a voltage that is positive relative to a common ground. There is a

related line of 79xx devices which are complementary negative voltage regulators. 78xx

and 79xx ICs can be used in combination to provide positive and negative supply voltages

in the same circuit.



FIG-10 Voltage regulator – LM 78xx

78xx ICs have three terminals and are commonly found in the TO220 form factor,

although smaller surface-mount and larger TO3 packages are available. These devices

support an input voltage anywhere from a couple of volts over the intended output voltage,

up to a maximum of 35 or 40 volts, and typically provide 1 or 1.5 amperes of current

(though smaller or larger packages may have a lower or higher current rating).

Advantages

78xx series ICs do not require additional components to provide a constant, regulated

source of power, making them easy to use, as well as economical and efficient uses of

space. Other voltage regulators may require additional components to set the output

voltage level, or to assist in the regulation process. Some other designs (such as a

switched-mode power supply) may need substantial engineering expertise to implement.

78xx series ICs have built-in protection against a circuit drawing too much power. They

have protection against overheating and short-circuits, making them quite robust in most

applications. In some cases, the current-limiting features of the 78xx devices can provide

protection not only for the 78xx itself, but also for other parts of the circuit.78xx ICs are

easy to use and handle but these cannot give a altering voltage required so Lm317 series of

ICs are available to obtain a voltage output from 1.25 volts to 37 volts.



Disadvantages

The input voltage must always be higher than the output voltage by some minimum

amount (typically 2 volts). This can make these devices unsuitable for powering some

devices from certain types of power sources (for example, powering a circuit that requires

5 volts using 6-volt batteries will not work using a 7805).

As they are based on a linear regulator design, the input current required is always the

same as the output current. As the input voltage must always be higher than the output

voltage, this means that the total power (voltage multiplied by current) going into the 78xx

will be more than the output power provided. The extra input power is dissipated as heat.

This means both that for some applications an adequate heatsink must be provided, and

also that a (often substantial) portion of the input power is wasted during the process,

rendering them less efficient than some other types of power supplies.

When the input voltage is significantly higher than the regulated output voltage (for

example, powering a 7805 using a 24 volt power source), this inefficiency can be a

significant issue.Even in larger packages, 78xx integrated circuits cannot supply as much

power as many designs which use discrete components, and are generally inappropriate for

applications requiring more than a few amperes of current.

Transformer

A transformer is a device that transfers electrical energy from one circuit to another

through inductively coupled conductors—the transformer's coils. A varying current in the

first or primary winding creates a varying magnetic flux in the transformer's core and thus

a varying magnetic field through the secondary winding. This varying magnetic field

induces a varying electromotive force (EMF), or "voltage", in the secondary winding. This

effect is called inductive coupling.



FIG- 11. Transformer windings

If a load is connected to the secondary, current will flow in the secondary winding, and

electrical energy will be transferred from the primary circuit through the transformer to the

load. In an ideal transformer, the induced voltage in the secondary winding (Vs) is in

proportion to the primary voltage (Vp) and is given by the ratio of the number of turns in

the secondary (Ns) to the number of turns in the primary (Np) as follows:By appropriate

selection of the ratio of turns, a transformer thus enables an alternating current (AC)

voltage to be "stepped up" by making Ns greater than Np, or "stepped down" by making

Ns less than Np.In the vast majority of transformers, the windings are coils wound around

a ferromagnetic core, air-core transformers being a notable exception.

Transformers range in size from a thumbnail-sized coupling transformer hidden inside a

stage microphone to huge units weighing hundreds of tons used to interconnect portions of

power grids. All operate on the same basic principles, although the range of designs is

wide. While new technologies have eliminated the need for transformers in some

electronic circuits, transformers are still found in nearly all electronic devices designed for

household ("mains") voltage. Transformers are essential for high-voltage electric power

transmission, which makes long-distance transmission economically practical.

A transformer is an electrical device that transfers energy from one circuit to another by

magnetic coupling with no moving parts. A transformer comprises two or more coupled

windings, or a single tapped winding and, in most cases, a magnetic core to concentrate

magnetic flux. A changing current in one winding creates a time-varying magnetic flux in

the core, which induces a voltage in the other windings. Michael Faraday built the first



transformer, although he used it only to demonstrate the principle of electromagnetic

induction and did not foresee the use to which it would eventually be put.

FIG- 12 Transformer core

DC Motor

A DC motor is an electric motor that runs on direct current (DC) electricity. DC motors

were used to run machinery, often eliminating the need for a local steam engine or internal

combustion engine. DC motors can operate directly from rechargeable batteries, providing

the motive power for the first electric vehicles. Today DC motors are still found in

applications as small as toys and disk drives, or in large sizes to operate steel rolling mills

and paper machines. Modern DC motors are nearly always operated in conjunction with

power electronic devices.

Two important performance parameters of DC motors are the motor constants, Kv and

Km.



FIG-13DC motor

DC motor

When a current passes through the coil wound around a soft iron core, the side of the

positive pole is acted upon by an upwards force, while the other side is acted upon by a

downward force. According to Fleming's left hand rule, the forces cause a turning effect on

the coil, making it rotate. To make the motor rotate in a constant direction, "direct current"

commutators make the current reverse in direction every half a cycle (in a two-pole motor)

thus causing the motor to continue to rotate in the same direction.

A problem with the motor shown above is that when the plane of the coil is parallel to the

magnetic field—i.e. when the rotor poles are 90 degrees from the stator poles—the torque

is zero. In the pictures above, this occurs when the core of the coil is horizontal—the

position it is just about to reach in the last picture on the right. The motor would not be

able to start in this position. However, once it was started, it would continue to rotate

through this position by momentum.

There is a second problem with this simple pole design. At the zero-torque position, both

commutator brushes are touching (bridging) both commutator plates, resulting in a short-

circuit. The power leads are shorted together through the commutator plates, and the coil is



also short-circuited through both brushes (the coil is shorted twice, once through each

brush independently). Note that this problem is independent of the non-starting problem

above; even if there were a high current in the coil at this position, there would still be zero

torque. The problem here is that this short uselessly consumes power without producing

any motion (nor even any coil current.) In a low-current battery-powered demonstration

this short-circuiting is generally not considered harmful. However, if a two-pole motor

were designed to do actual work with several hundred watts of power output, this shorting

could result in severe commutator overheating, brush damage, and potential welding of the

brushes—if they were metallic—to the commutator. Carbon brushes, which are often used,

would not weld. In any case, a short like this is very wasteful, drains batteries rapidly and,

at a minimum, requires power supply components to be designed to much higher standards

than would be needed just to run the motor without the shorting.

The inside of an electric DC motor.

One simple solution is to put a gap between the commutator plates which is wider than the

ends of the brushes. This increases the zero-torque range of angular positions but

eliminates the shorting problem; if the motor is started spinning by an outside force it will

continue spinning. With this modification, it can also be effectively turned off simply by

stalling (stopping) it in a position in the zero-torque (i.e. commutator non-contacting) angle

range. This design is sometimes seen in homebuilt hobby motors, e.g. for science fairs and

such designs can be found in some published science project books. A clear downside of

this simple solution is that the motor now coasts through a substantial arc of rotation twice

per revolution and the torque is pulsed. This may work for electric fans or to keep a

flywheel spinning but there are many applications, even where starting and stopping are

not necessary, for which it is completely inadequate, such as driving the capstan of a tape

transport, or any instance where to speed up and slow down often and quickly is a

requirement. Another disadvantage is that, since the coils have a measure of self

inductance, current flowing in them cannot suddenly stop. The current attempts to jump the

opening gap between the commutator segment and the brush, causing arcing.

Even for fans and flywheels, the clear weaknesses remaining in this design—especially

that it is not self-starting from all positions—make it impractical for working use,

especially considering the better alternatives that exist. Unlike the demonstration motor



above, DC motors are commonly designed with more than two poles, are able to start from

any position, and do not have any position where current can flow without producing

electromotive power by passing through some coil. Many common small brushed DC

motors used in toys and small consumer appliances, the simplest mass-produced DC

motors to be found, have three-pole armatures. The brushes can now bridge two adjacent

commutator segments without causing a short circuit. These three-pole armatures also have

the advantage that current from the brushes either flows through two coils in series or

through just one coil. Starting with the current in an individual coil at half its nominal

value (as a result of flowing through two coils in series), it rises to its nominal value and

then falls to half this value. The sequence then continues with current in the reverse

direction. This results in a closer step-wise approximation to the ideal sinusoidal coil

current, producing a more even torque than the two-pole motor where the current in each

coil is closer to a square wave. Since current changes are half those of a comparable two-

pole motor, arcing at the brushes is consequently less.

If the shaft of a DC motor is turned by an external force, the motor will act like a generator

and produce an Electromotive force (EMF). During normal operation, the spinning of the

motor produces a voltage, known as the counter-EMF (CEMF) or back EMF, because it

opposes the applied voltage on the motor. The back EMF is the reason that the motor when

free-running does not appear to have the same low electrical resistance as the wire

contained in its winding. This is the same EMF that is produced when the motor is used as

a generator (for example when an electrical load, such as a light bulb, is placed across the

terminals of the motor and the motor shaft is driven with an external torque). Therefore,

the total voltage drop across a motor consists of the CEMF voltage drop, and the parasitic

voltage drop resulting from the internal resistance of the armature's windings.

Speed control

Generally, the rotational speed of a DC motor is proportional to the voltage applied to it,

and the torque is proportional to the current. Speed control can be achieved by variable

battery tappings, variable supply voltage, resistors or electronic controls. The direction of a

wound field DC motor can be changed by reversing either the field or armature

connections but not both. This is commonly done with a special set of contactors (direction

contactors).The effective voltage can be varied by inserting a series resistor or by an



electronically controlled switching device made of thyristors, transistors, or, formerly,

mercury arc rectifiers.

In a circuit known as a chopper, the average voltage applied to the motor is varied by

switching the supply voltage very rapidly. As the "on" to "off" ratio is varied to alter the

average applied voltage, the speed of the motor varies. The percentage "on" time

multiplied by the supply voltage gives the average voltage applied to the motor. Therefore,

with a 100 V supply and a 25% "on" time, the average voltage at the motor will be 25 V.

During the "off" time, the armature's inductance causes the current to continue through a

diode called a "flyback diode", in parallel with the motor. At this point in the cycle, the

supply current will be zero, and therefore the average motor current will always be higher

than the supply current unless the percentage "on" time is 100%. At 100% "on" time, the

supply and motor current are equal. The rapid switching wastes less energy than series

resistors. This method is also called pulse-width modulation (PWM) and is often controlled

by a microprocessor. An output filter is sometimes installed to smooth the average voltage

applied to the motor and reduce motor noise.

Since the series-wound DC motor develops its highest torque at low speed, it is often used

in traction applications such as electric locomotives, and trams. Another application is

starter motors for petrol and small diesel engines. Series motors must never be used in

applications where the drive can fail (such as belt drives). As the motor accelerates, the

armature (and hence field) current reduces. The reduction in field causes the motor to

speed up until it destroys itself. This can also be a problem with railway motors in the

event of a loss of adhesion since, unless quickly brought under control, the motors can

reach speeds far higher than they would do under normal circumstances. This can not only

cause problems for the motors themselves and the gears, but due to the differential speed

between the rails and the wheels it can also cause serious damage to the rails and wheel

treads as they heat and cool rapidly. Field weakening is used in some electronic controls to

increase the top speed of an electric vehicle.

The simplest form uses a contactor and field-weakening resistor; the electronic control

monitors the motor current and switches the field weakening resistor into circuit when the

motor current reduces below a preset value (this will be when the motor is at its full design

speed). Once the resistor is in circuit, the motor will increase speed above its normal speed



at its rated voltage. When motor current increases, the control will disconnect the resistor

and low speed torque is made available.

One interesting method of speed control of a DC motor is the Ward Leonard control. It is a

method of controlling a DC motor (usually a shunt or compound wound) and was

developed as a method of providing a speed-controlled motor from an AC supply, though

it is not without its advantages in DC schemes. The AC supply is used to drive an AC

motor, usually an induction motor that drives a DC generator or dynamo. The DC output

from the armature is directly connected to the armature of the DC motor (sometimes but

not always of identical construction). The shunt field windings of both DC machines are

independently excited through variable resistors. Extremely good speed control from

standstill to full speed, and consistent torque, can be obtained by varying the generator

and/or motor field current. This method of control was the de facto method from its

development until it was superseded by solid state thyristor systems.

It found service in almost any environment where good speed control was required, from

passenger lifts through to large mine pit head winding gear and even industrial process

machinery and electric cranes. Its principal disadvantage was that three machines were

required to implement a scheme (five in very large installations, as the DC machines were

often duplicated and controlled by a tandem variable resistor). In many applications, the

motor-generator set was often left permanently running, to avoid the delays that would

otherwise be caused by starting it up as required. Although electronic (thyristor) controllers

have replaced most small to medium Ward-Leonard systems, some very large ones

(thousands of horsepower) remain in service. The field currents are much lower than the

armature currents, allowing a moderate sized thyristor unit to control a much larger motor

than it could control directly. For example, in one installation, a 300 amp thyristor unit

controls the field of the generator. The generator output current is in excess of 15,000

amperes, which would be prohibitively expensive (and inefficient) to control directly with

thyristors.

INFRARED SENSOR

In this IR detector and transmitter circuit the IC 555 is working under astable mode. The

pin 4 i.e. reset pin is when grounded via IR receiver the pin 3 output is low.



FIG-14 Infra red sensor with circuitry

As soon as the IR light beam transmitted is obstructed, a momentary pulse actuates the

relay output (or LED).The IR transmitter is simple series connected resistor network from

battery. The timing capacitor connected to pin 2 and ground can varied as per requirement

Switched-mode power supply

A switched-mode power supply (switching-mode power supply, SMPS, or switcher) is an

electronic power supply that incorporates a switching regulator to convert electrial power

efficiently. Like other power supplies, an SMPS transfers power from a source like the

electrical powergrid to a load (such as a personal computer) while

converting voltage and current characteristics. An SMPS is usually employed to efficiently

provide a regulated output voltage, typically at a level different from the input voltage.


http://en.wikipedia.org/wiki/Electric_current

http://en.wikipedia.org/wiki/Voltage

http://en.wikipedia.org/wiki/Personal_computer

http://en.wikipedia.org/wiki/Power_supply


Unlike a linear power supply, the pass transistor of a switching mode supply continually

switches between low-dissipation, full-on and full-off states, and spends very little time in

the high dissipation transitions (which minimizes wasted energy). Ideally, a switched-

mode power supply dissipates no power

FIG-15 Switched mode power supply circuitry

Unlike a linear power supply, the pass transistor of a switching mode supply continually

switches between low-dissipation, full-on and full-off states, and spends very little time in

the high dissipation transitions (which minimizes wasted energy). Ideally, a switched-

mode power supply dissipates no power. Voltage regulation is achieved by varying the

ratio of on-to-off time. In contrast, a linear power supply regulates the output voltage by

continually dissipating power in the pass transistor. This higher power conversion

efficiency is an important advantage of a switched-mode power supply. Switched-mode

power supplies may also be substantially smaller and lighter than a linear supply due to the

smaller transformer size and weight.

Switching regulators are used as replacements for the linear regulators when higher

efficiency, smaller size or lighter weight are required. They are, however, more



complicated, their switching currents can cause electrical noise problems if not carefully

suppressed, and simple designs may have a linear regulator provides the desired

output voltage by dissipating excess power in ohmic losses (e.g., in a resistor or in the

collector–emitter region of a pass transistor in its active mode). A linear regulator regulates

either output voltage or current by dissipating the excess electric power in the form of heat,

and hence its maximum power efficiency is voltage-out/voltage-in since the volt difference

is wasted. In contrast, a switched-mode power supply regulates either output voltage or

current by switching ideal storage elements, like inductors and capacitors, into and out of

different electrical configurations. Ideal switching elements (e.g., transistors operated

outside of their active mode) have no resistance when "closed" and carry no current when

"open", and so the converters can theoretically operate with 100% efficiency (i.e., all input

power is delivered to the load; no power is wasted as dissipated heat).

For example, if a DC source, an inductor, a switch, and the corresponding electrical

ground are placed in series and the switch is driven by a square wave, the peak-to-peak

voltage of the waveform measured across the switch can exceed the input voltage from the

DC source. This is because the inductor responds to changes in current by inducing its own

voltage to counter the change in current, and this voltage adds to the source voltage while

the switch is open.

If a diode-and-capacitor combination is placed in parallel to the switch, the peak voltage

can be stored in the capacitor, and the capacitor can be used as a DC source with an output

voltage greater than the DC voltage driving the circuit. This boost converter acts like

a step-up transformer for DC signals. A buck–boost converter works in a similar manner,

but yields an output voltage which is opposite in polarity to the input voltage.

Other buck circuits exist to boost the average output current with a reduction of voltage.

In an SMPS, the output current flow depends on the input power signal, the storage

elements and circuit topologies used, and also on the pattern used (e.g. pulse-width

modulation with an adjustable duty cycle) to drive the switching elements. Typically,

the spectral density of these switching waveforms has energy concentrated at relatively

high frequencies. As such, switching transients, like ripple, introduced onto the output

waveforms can be filtered with small LC filters.


http://en.wikipedia.org/wiki/LC_filter

http://en.wikipedia.org/wiki/Ripple_(electrical)

http://en.wikipedia.org/wiki/Spectral_density

http://en.wikipedia.org/wiki/Duty_cycle

http://en.wikipedia.org/wiki/Pulse-width_modulation

http://en.wikipedia.org/wiki/Pulse-width_modulation

http://en.wikipedia.org/wiki/Buck%E2%80%93boost_converter

http://en.wikipedia.org/wiki/Transformer

http://en.wikipedia.org/wiki/Boost_converter

http://en.wikipedia.org/wiki/Square_wave

http://en.wikipedia.org/wiki/Electrical_ground

http://en.wikipedia.org/wiki/Electrical_ground

http://en.wikipedia.org/wiki/Capacitor

http://en.wikipedia.org/wiki/Inductor

http://en.wikipedia.org/wiki/Heat

http://en.wikipedia.org/wiki/Ohm's_law

http://en.wikipedia.org/wiki/Voltage

http://en.wikipedia.org/wiki/Linear_regulator


Advantages and disadvantages

The main advantage of this method is greater efficiency because the switching transistor

dissipates little power when it is outside of its active region (i.e., when the transistor acts

like a switch and either has a negligible voltage drop across it or a negligible current

through it). Other advantages include smaller size and lighter weight (from the elimination

of low frequency transformers which have a high weight) and lower heat generation due to

higher efficiency.

Disadvantages include greater complexity, the generation of high-amplitude, high-

frequency energy that the low-pass filter must block to avoid electromagnetic

interference (EMI), a ripple voltage at the switching frequency and the harmonic

frequencies thereof. Very low cost SMPSs may couple electrical switching noise back onto

the mains power line, causing interference with A/V equipment connected to the same

phase. Non-power-factor-corrected SMPSs also cause harmonic distortion

Battery

An electrochemical battery - or, more precisely, a "cell" - is a device in which the reaction

between two substances can be made to occur in such a way that some of the chemical

energy is converted to useful electricity. When the cell can only be used once, it is called a

"primary" cell. When the chemical reaction can be reversed repeatedly by applying

electrical energy to the cell, it is called a "secondary" cell and can be used in an

accumulator or "storage" battery.

Certain cells are capable of only a few charge-discharge cycles and are, therefore,

technically "secondary" cells. Such is the case with certain silver oxide-zinc batteries.

These batteries are not capable of the repeated cycling required of a satellite battery

system, and are, therefore, considered to be "rechargeable primary" rather than storage

batteries. To define a battery in another way, it is an arrangement whereby an

"electrochemical" reaction can be made to take place so that the "electrical" part of the


http://en.wikipedia.org/wiki/Power_factor_correction

http://en.wikipedia.org/wiki/Harmonic_frequency

http://en.wikipedia.org/wiki/Harmonic_frequency

http://en.wikipedia.org/wiki/Ripple_voltage

http://en.wikipedia.org/wiki/Electromagnetic_interference

http://en.wikipedia.org/wiki/Electromagnetic_interference


reaction proceeds via the metallic path of the external circuit, while the "chemical" part of

the reaction occurs via ionic conduction through electrolyte.

The type of chemical reaction that can be used in an electrochemical cell is known as an

"oxidation-reduction" reaction - a reaction in which one chemical species gives electrons to

another. By separating the two species and controlling the flow of ions between them,

battery engineers make devices in which essentially all of these electrons can be made to

flow through an external circuit, thereby converting most of the chemical energy to

electrical energy during the discharge of the cell.

Some of the components common to all cells are:

1. The "cathode" or "positive" electrode, which consists of a mass of "electron-receptive"

chemical held in intimate contact with a metallic "plate" through which the electrons

arrive from the external circuit.

2. The "anode" or "negative" electrode, which consists of another chemical which readily

gives up electrons - an "electron donor" - similarly held in close contact with a metallic

member through which electrons can be conducted to the external circuit.

3. The "electrolyte," usually a liquid solution that permits the transfer of mass necessary

to the overall reaction. This movement takes place by "migration" of "ions" - positively

or negatively charged molecular fragments - from anode to cathode and from cathode

FIG- 16 Battery



A schematic diagram of these basic cell elements is shown above. The cell is shown

connected to a load - representing the discharge reaction. Charging is accomplished by

connecting an electrical source in place of the load, thereby reversing the entire process.

UV Detector

UV detectors function on the capacity of many compounds to absorb light in the

wavelength range 180 to 350 nm. The sensor cell usually consists of a cylindrical cavity

about 1 mm I.D and a few mm long, having a capacity that ranges from about two micro-

liters to eight micro-liters.

FIG- 17 UV detector

Light from a UV light sources passes through the sensor onto a photoelectric cell, the out

put from which is electronically modified and presented on a potentiometric recorder, a

computer screen, or printer. By interposing a monochrometer between the light source and

the cell, light of a specific wavelength can be selected for detection and, thus, improve the

detector selectivity.

Alternatively a broad band light source can be used and the light after passing through the

cell can be optically dispersed by prism or grating and allowed to fall onto a diode array.

By monitoring a specific diode, the detector can be made specific for those substances that

absorb at that particular wavelength. If the output from all the diodes is scanned then a UV

absorption spectrum can be obtained to aid in solute identification. The fixed wavelength

UV detector has a sensitivity of about 1 x 10-8 g per ml at a signal to noise ratio of two are

the UV detector (fixed and variable wavelength) the electrical conductivity detector, the

fluorescence detector and the refractive index detector. These detectors are employed in

over 95% of all LC analytical applications. These four detectors will be described and for

those readers requiring more information on detectors are referred to Liquid



Chromatography Detectors.

The UV Detector The UV detector is by far the most popular and useful LC detector that is

available to the analyst at this time. This is particularly true if multi-wavelength

technology is included in this class of detectors. Although the UV detector has some

definite limitations (particularly for the detection of non polar solutes that do not possess a

UV chromaphores) it has the best

CAUTIONS

(1) Cautions

1. The devices are UV light LEDs. The LED during operation radiates intense UV light,

which precautions must be taken to prevent looking directly at the UV light with

unaided eyes.

2. Do not look directly into the UV light or look through the optical system. When there

is a possibility to receive the reflection of light, protect by using the UV light

protective glasses so that light should not catch one’s eye directly.

3. Put the caution label on the cardboard box.

(2) Lead Forming

1. When forming leads, the leads should be bent at a point at least 3mm from the base of

the lead.

2. Do not use the base of the lead frame as a fulcrum during lead forming.

3. Lead forming should be done before soldering.

4. Do not apply any bending stress to the base of the lead. The stress to the base may

damage the LED’s characteristics or it may break the LEDs.

5. When mounting the LEDs onto a printed circuit board, the holes on the circuit board

should be exactly aligned with the leads of the LEDs. If the LEDs are mounted with

stress at the leads, it causes deterioration of the lead and this will degrade the LEDs.



(3) Storage

The LEDs should be stored at 30°C or less and 70%RH or less after being shipped from

Nichia and the storage life limits are 3 months. If the LEDs are stored for 3 months or

more, they can be stored for a year in a sealed container with a nitrogen atmosphere and

moisture absorbent material. Nichia LED leads are comprised of a gold plated Iron alloy.

The gold surface may be affected by environments which contain corrosive gases and so

on. Please avoid conditions which may cause the LED to corrode, tarnish or discolor. This

corrosion or discoloration may cause difficulty during soldering operations. It is

recommended that the LEDs be used as soon as possible. Please avoid rapid transitions in

ambient temperature, especially, in high humidity environments where condensation can

occur.

(4) Static Electricity

Static electricity or surge voltage damages the LEDs. It is recommended that a wrist band

or an anti-electrostatic glove be used when handling the LEDs. All devices, equipment and

machinery must be properly grounded. It is recommended that measure be taken against

surge voltage to the equipment that mounts LEDs. When inspecting the final products in

which LEDs were assembled, it is recommended to check whether the assembled LEDs are

damaged by static electricity or not. It is easy to find static-damaged LEDs by a light-on

test or a VF test at a lower current (below 1mA is recommended). The LEDs should be

used the light detector etc. when testing the light-on. Do not stare into the LEDs when

testing. Damaged LEDs will show some unusual characteristics such as the forward

voltage becomes lower, or the LEDs do not light at the low current. Criteria : (VF > 2.0V

at IF=0.5mA)

(6) Heat Generation

Thermal design of the end product is of paramount importance. Please consider the heat

generation of the LED when making the system design. The coefficient of temperature

increase per input electric power is affected by the thermal resistance of the circuit board

and density of LED placement on the board, as well as other components. It is necessary to



avoid intense heat generation and operate within the maximum ratings given in this

specification. The operating current should be decided after considering the ambient

maximum temperature of LEDs.

(7) Cleaning

It is recommended that isopropyl alcohol be used as a solvent for cleaning the LEDs.

When using other solvents, it should be confirmed beforehand whether the solvents will

dissolve the glass or not. Freon solvents should not be used to clean the LEDs because of

worldwide regulations. Do not clean the LEDs by the ultrasonic. When it is absolutely

necessary, the influence of ultrasonic cleaning on the LEDs depends on factors such as

ultrasonic power and the assembled condition. Before cleaning, a pre-test should be done

to confirm whether any damage to the LEDs will occur.

(8) Safety Guideline for Human Eyes

In 1993, the International Electric Committee (IEC) issued a standard concerning laser

product safety. Since then, this standard has been applied for diffused light sources (LEDs)

as well as lasers. In 1998 IEC 60825-1 Edition 1.1 evaluated the magnitude of the light

source. In 2001 IEC 60825-1 Amendment 2 converted the laser class into 7 classes for end

products. Components are excluded from this system. Products which contain visible

LEDs are now classified as class 1. Products containing UV LEDs are class 1M. Products

containing LEDs can be classified as class 2 in cases where viewing angles are narrow,

optical manipulation intensifies the light, and/or theenergy emitted is high. For these

systems it is recommended to avoid long term exposure. It is also recommended to follow

the IEC regulations regarding safety and labeling of products.

(9) Others

NSHU550B complies with RoHS Directive. This LED also emits visible light. Please take

notice of visible light spectrum, in case you use this LED as light source of sensors etc.

The LEDs described in this brochure are intended to be used for ordinary electronic



equipment (such as office equipment, communications equipment, measurement

instruments and household appliances).

Consult Nichia’s sales staff in advance for information on the applications in which

exceptional quality and reliability are required, particularly when the failure or malfunction

of the LEDs may directly. Jeopardize life or health (such as for airplanes, aerospace,

submersible repeaters, nuclear reactor control systems, automobiles, traffic control

equipment, life support systems and safety devices).User shall not reverse engineer by

disassembling or analysis of the LEDs without having the prior written consent of Nichia.

When defective LEDs are found, User shall inform to Nichia directly before disassembling

or analysis.The formal specifications must be exchanged and signed by both parties before

large volume purchase begins. The appearance and specifications of the product may be

modified for improvement without

ULN2003

ULN2003 is a high voltage and high current Darlington array IC. It contains seven open

collector darlington pairs with common emitters. A darlington pair is an arrangement of

two bipolar transistors. ULN2003 belongs to the family of ULN200X series of ICs.

Different versions of this family interface to different logic families.ULN2003 are for 5V

TTL, CMOS logic devices. These ICs are used when driving a wide range of loads and are

used as relay drivers, display drivers, line drivers etc.

ULN2003 is also commonly used while driving Stepper Motors. The ULN2003 is a

monolithic high voltage and high current Darlington transistor arrays. It consists of seven

NPN darlington pairs that features high voltage outputs with common-cathode clamp diode

for switching inductive loads. The collector-current rating of a single darlington pair is

500mA. The darlington pairs may be paralleled for higher current capability. Applications

include relay drivers, hammer drivers, lamp drivers, display drivers(LED gas

discharge),line drivers, and logic buffers. The ULN2003 has a 2.7kΩ series base resistor

for each darlington pair for operation directly with TTL or 5V CMOS devices.



FIG-18 ULN2003 Darlington using high-power stepper motor ..

FEATURES

500mA rated collector current(Single output)

High-voltage outputs: 50V

Inputs compatible with various types of logic.

Relay driver application



4. CODES

$mod51

org 0000h

mov p1,#0ffh

mov p3,#0h

mov p2,#0h

mov p0,#0h

mov r7,#02h

mov r6,#0h

mov r5,#0h

mov r4,#02h

setb p3.0

abc:jb p3.0,abc

setb p3.1

setb p3.2

setb p3.3

setb p3.4

setb p3.5

setb p3.6

clr p3.7

acall wel_lcd

ljmp main

wel_lcd:

mov a,#38h

acall comnwrt

acall delay

mov a,#0ch

acall comnwrt

acall delay

mov a,#01h



acall comnwrt

acall delay

mov a,#06h

acall comnwrt

acall delay

mov a,#80h

acall comnwrt

acall delay

mov a,#'R'

acall datawrt

acall delay

mov a,#'B'

acall datawrt

acall delay

mov a,#'I'

acall datawrt

acall delay

mov a,#' '

acall datawrt

acall delay

mov a,#'N'

acall datawrt

acall delay

mov a,#'O'

acall datawrt

acall delay

mov a,#'T'

acall datawrt

acall delay

mov a,#'E'

acall datawrt

acall delay



mov a,#'I'

acall datawrt

acall delay

mov a,#'R'

acall datawrt

acall delay

mov a,#' '

acall datawrt

acall delay

mov a,#'C'

acall datawrt

acall delay

mov a,#'O'

acall datawrt

acall delay

mov a,#'U'

acall datawrt

acall delay

mov a,#'N'

acall datawrt

acall delay

mov a,#'T'

acall datawrt

acall delay

mov a,#'I'

acall datawrt

acall delay

mov a,#'N'

acall datawrt

acall delay

mov a,#'G'

acall datawrt



acall delay

ret

main:

jb p3.0,fdf

cpl p3.1

fdf:jb p1.0,aa

ljmp anion

aa:jb p1.1,bb2

ljmp uv

bb2:jb p1.2,cc2

ljmp tmer

cc2:jb p1.3,tter

ljmp speed

tter:mov a,#1ch

acall comnwrt

acall delay

acall delay

acall delay

acall delay

ljmp main

anion:

cjne r6,#01h,wqw

mov r6,#0h

ljmp qwq



wqw:

inc r6

acall wel_lcd

mov a,#0c0h

acall comnwrt

acall delay

mov a,#'A'

acall datawrt

acall delay

mov a,#':'

acall datawrt

acall delay

mov a,#'O'

acall datawrt

acall delay

mov a,#'N'

acall datawrt

acall delay

setb p3.2

ljmp main

qwq:

acall wel_lcd

mov a,#'A'

acall datawrt

acall delay

mov a,#':'

acall datawrt

acall delay

mov a,#'O'

acall datawrt

acall delay



mov a,#'F'

acall datawrt

acall delay

mov a,#'F'

acall datawrt

acall delay

clr p3.2

acall delay2

ljmp wel_lcd

uv:

cjne r5,#01h,wqq

mov r5,#0h

ljmp qww

wqq:

inc r5

mov a,#01h

acall comnwrt

acall delay

mov a,#'U'

acall datawrt

acall delay

mov a,#'V'

acall datawrt

acall delay

mov a,#':'

acall datawrt

acall delay

mov a,#'O'

acall datawrt

acall delay



mov a,#'N'

acall datawrt

acall delay

setb p3.3

acall delay2

ljmp wel_lcd

qww:mov a,#01h

acall comnwrt

acall delay

mov a,#'U'

acall datawrt

acall delay

mov a,#'V'

acall datawrt

acall delay

mov a,#':'

acall datawrt

acall delay

mov a,#'O'

acall datawrt

acall delay

mov a,#'F'

acall datawrt

acall delay

mov a,#'F'

acall datawrt

acall delay

clr p3.3

acall delay2

ljmp wel_lcd



speed:inc r7

cjne r7,#03h,asd

mov r7,#0h

mov a,#01h

acall comnwrt

acall delay

mov a,#'S'

acall datawrt

acall delay

mov a,#'P'

acall datawrt

acall delay

mov a,#'E'

acall datawrt

acall delay

mov a,#'E'

acall datawrt

acall delay

mov a,#'D'

acall datawrt

acall delay

mov a,#':'

acall datawrt

acall delay

mov a,#'3'

acall datawrt

acall delay

setb p3.7

setb p3.6

setb p3.5

acall delay2

ljmp wel_lcd



asd:cjne r7,#02h,dsad

mov a,#01h

acall comnwrt

acall delay

mov a,#'S'

acall datawrt

acall delay

mov a,#'P'

acall datawrt

acall delay

mov a,#'E'

acall datawrt

acall delay

mov a,#'E'

acall datawrt

acall delay

mov a,#'D'

acall datawrt

acall delay

mov a,#':'

acall datawrt

acall delay

mov a,#'2'

acall datawrt

acall delay

setb p3.5

setb p3.6

clr p3.7

acall delay2

ljmp wel_lcd



dsad:cjne r7,#01h,rwe

mov a,#01h

acall comnwrt

acall delay

mov a,#'S'

acall datawrt

acall delay

mov a,#'P'

acall datawrt

acall delay

mov a,#'E'

acall datawrt

acall delay

mov a,#'E'

acall datawrt

acall delay

mov a,#'D'

acall datawrt

acall delay

mov a,#':'

acall datawrt

acall delay

mov a,#'1'

acall datawrt

acall delay

setb p3.5

clr p3.6

clr p3.7

acall delay2

ljmp wel_lcd

rwe:cjne r7,#0h,gfd



mov r7,#02h

acall delay1

ljmp main

gfd:ljmp main

tmer:ljmp main

comnwrt:

mov p2,a

clr p0.0

setb p0.1

clr p0.1

ret

datawrt:

mov p2,a

setb p0.0

setb p0.1

clr p0.1

RET

delay:MOV R2,#90

MOV R1,#162

TT1: DJNZ R1,TT1

DJNZ R2,TT1

RET

delay1:MOV R3,#4

MOV R2,#132

MOV R1,#116

TT11: DJNZ R1,TT11

DJNZ R2,TT11

DJNZ R3,TT11



ret

delay2:MOV R3,#15

MOV R2,#16

MOV R1,#221

TT12: DJNZ R1,TT12

DJNZ R2,TT12

DJNZ R3,TT12

RET

End



5. DISCUSSION OF RESULTS

The idea was to create an currency note counting machine with fake detection which

would circumvent the manual detection involved in detecting fake currency. Currency

created by colour copier or printer produces an image tht rest on the surface of paper that

can easily be seen when uv light is placed over it. Real notes notes are printed on optical

fiber paper fake ones on thick paper made of bamboo pulp. Money Counter & Counterfeit

Note Detector offers exclusive peace of mind. Provided with a top mounted numeric count

display screen as well as a detachable LCD display for customers, this helps keep your

counts accurate and quick. With built in UV and Thread detection, this unit prevents any

fakes from being passed on to you.

Detecting fake bills just by looking at it, is not exactly the most efficient or even reliable

way of knowing for sure if a bill is fake. Counterfeit notes are becoming more difficult to

detect with the naked eye, that's were advanced machines like this 2-in-1 multi-currency

money counter & detector comes in. This is a professional grade unit being offered

exclusively to our customers at a low factory-direct wholesale price, making this new

money counter and counterfeit detector a must-have-product for any small, medium or

large business.

FICN (Fake Indian Currency Note) is a term used by officials and media to refer

fake Indian currency notes circulated in the Indian economy. The fake notes of latest

Gandhi series are so perfect that it is hard to identify if it is fake or not. Though fake

currency is being printed with precision, CID sleuths say that they can be detected with

some effort. Currency printed by local racketeers can be detected easily as they use

photographic method, hand engraved blocks, lithographic process and computer colour

scanning.In counterfeit notes the watermark is made by using opaque ink, painting with

white solution, stamping with a dye engraved with the picture of Mahatma Gandhi. Then

the gangs apply oil, grease or wax to give the picture a translucent feel. In genuine notes

the security thread is incorporated into the paper at the time of manufacture.


http://en.wikipedia.org/wiki/Security_thread

http://en.wikipedia.org/wiki/Mahatma_Gandhi

http://en.wikipedia.org/wiki/Racketeer

http://en.wikipedia.org/wiki/Counterfeit_money


http://en.wikipedia.org/wiki/Indian_economy

http://en.wikipedia.org/wiki/Currency

http://en.wikipedia.org/wiki/India


But in fake notes, the security thread is imitated by drawing a line with a pencil or by

printing a line with grey ink or by using aluminium thread while pasting two thin sheets of

paper. Forgers find it difficult to reproduce the same shape of individual numbers again

and again with accuracy. The alignment of figures is also difficult to maintain. Spreading

of ink, smaller or bigger number, inadequate gaps, and different alignments in numbers

should be regarded with suspicion. In counterfeit notes, the printed lines will be broken

and there may also be ink smudges. Basic banknote counters provide a total count of the

notes in the supply hopper.

More advanced counters can identify different bill denominations to provide a total

currency value of mixed banknotes, including those that are upside down. Some banknote

counters can also detect counterfeit bills either magnetically and/or using backlights. Black

light (UV) based detectors exploit the fact that in many countries, real banknotes have

fluorescent symbols on them that only show under a black light. Also, the paper used for

printing money does not contain any of the brightening agents which make commercially

available papers fluoresce under black light. Both features make counterfeit notes both

easier to detect and more difficult to successfully produce.

A stack of bills are placed in a compartment of the machine, and then one bill at a time is

mechanically pulled through the machine. By counting the number of times a beam of light

is interrupted, the machine can count the bills. By comparing an image of each bill

to pattern recognition criteria, the machine can figure out how much genuine money was

placed in the compartment.


http://en.wikipedia.org/wiki/Pattern_recognition

http://en.wikipedia.org/wiki/Compartment


http://en.wikipedia.org/wiki/Banknote_counter

http://en.wikipedia.org/wiki/Aluminium


6. CONCLUSION

Fake currency poses a grave threat to national security and could also result in economic

destabilization. According to intelligence agencies, anti-national elements and crime

syndicates open several accounts and use the ATMs to deposit the fake currencies. If they

see that the amount has been credited to their account, they continue to deposit fake

money. If the amount is not credited they know that their game is up and no longer operate

that account. In the past, it was easy to detect fake currencies as they were printed by

people with limited expertise, using crude facilities. But with the forgers attaining a high

level of sophistication, it is increasingly difficult to detect fake notes.

The situation is scary, particularly after the recent detection of Rs 400 million from the

State Bank of India chest at one of its branches in the northern Uttar Pradesh state. Not

only the counterfeit notes were of high quality, but they also had the same serial numbers

as the genuine notes kept at the bank. It is estimated that around 1,69,000 crores of fake

rupees are in circulation all over India. Both Banks and Government are in a denial mode,

because probably they do not know what to do.

India has become the victim of another kind of terrorism from its neighbour, Pakistan. It is

economic terrorism in printing and circulating counterfeit Indian notes. The Pakistani

intelligence agency, ISI’s role in printing and circulation of fake Indian currency notes has

never been a secret.On its insistence, Pakistan Government has imported additional

currency-standard printing paper from companies located in London to pursue its nefarious

designs in India. Of late, Pakistan has been procuring currency-standard printing paper in

huge quantities from London-based companies much higher than normal requirement of

the country for printing its own currency. It is diverting it, to print fake Indian currency

notes. It is believed that Pakistan Government printing press in Quetta (Baluchistan)

Karachi’s security press, and two other presses in Lahore and Peshawar, are being used to

print out counterfeit Indian currency.

The ISI has, been using Pakistan International Airlines (PIA) to transport counterfeit

currency to its conduits in Nepal, Bangladesh and Sri Lanka. The modus operandi of the

ISI was revealed by two Nepali counterfeit currency traffickers who were arrested by



Thailand police sometimes back. During interrogation, the accused disclosed that they

were working for a prominent Nepali businessman. The fact that Nepali territory is being

used by Pakistanis to smuggle counterfeit currency is well known. The first such expose

was made when Pakistani diplomats were caught distributing fake Indian currency notes.

One Naushad Alam Khan, arrested in Dhaka on April 24, 2008, with fake Indian currency

notes worth Rs 50 lakh admitted his direct link with HuJI (Bangladesh) chief Mufti Abdul

Hannan. It was found that both Khan and Hannan had fought for Taliban in Afghanistan.

Fake Indian currency notes racket is being carried out by using the network of underworld

kingpin Dawood Ibrahim, not only in India but also in Sri Lanka, Bangladesh and Nepal in

close association with different terror outfits, according to one intelligence report. With Sri

Lanka, Nepal and Bangladesh being active partners, with India in probing fake Indian

currency notes (FICN) related cases, it is safe to assume that so far as the fake currency in

India is concerned, its source is Pakistan.Delhi police claims, to have busted a major ISI

network, sometimes back, which was reportedly being used to pushing fake currency into

our country. Three arrested men, by name, Nayeem, Wasim and Mohammed Muslim, have

revealed that Thar Express, so called, friendship train, running between Munnabao in

Pakistan and Jodhpur in Rajasthan, was being used to smuggle fake currency into India .

Investigation, uncovered, that the fake currency was arranged in Dubai. Fake currency to

the extent of Rs 33 lakh was seized from them.

They have confirmed that the Indian currency is printed in Pakistan and illegally pushed in

India through Nepal, Bangladesh, Sri Lanka, Malaysia and Thailand. The menace of finely

printed currency has achieved new heights, that quite often; the customers do get fake

currencies through ATMs. The worst is that when they approach banks with the complain

of receiving a fake note, bank official impound the notes. As per the law of land, the bank

should lodge an FIR with police, which would investigate the source of the fake currency.

Banks obviously have not been to cope with the problem. According to one Government

committee estimate, counterfeit currency amounting to Rs 169,000 crore is floating around

in the Indian financial system. This has been denied by the Reserve Bank of India. From

real estate transactions to ordinary grocery shopping, paying to sources and terrorist’s

expenses, these bogus notes are being used. Even if this figure is taken 20 to 25 per cent, as

correct, it is still a huge amount, and sufficient to damage India’s economy. “In 2008, the



CBI registered 13 cases having international/ inter-State ramifications relating to the

recovery/ seizure of fake Indian currency notes,”

According to the National Crime Record Bureau (NCRB), between January and August

2008, 1,170 cases had been registered across the country in connection with fake currency.

Bogus notes with a face value of Rs 3.63 crore had been seized. NCRB data shows 2,204

such cases were reported in 2007.Investigations into the Mumbai 26/11 attacks have

revealed that a large part of the money to fund the terror operation were obtained through

fake currency rackets and hawala channels.It is also believed that Pakistan’s Inter Services

Intelligence raises Rs 1,800 crore (Rs 18 billion) annually to fund terror operations and that

a major chunk of this amount comes in through fake currency rackets.

Intelligence sources believe that Rs 30 lakh of the Rs 50 lakh spent, on the attack on the

Indian Institute of Science, Bengaluru, in December 2005 was obtained through the fake

currency racket. This is big menace, which should be tackled with no holds barred, even if

it means walking with the devil till we have decimated this problem. It is rightly said, that

the poor of the world, cannot be made richer by redistribution of wealth. But, there are

some, who seek a short cut, to riches through crime and use of counterfeit currency.

Criminals believe, that whatever is worth doing is worth doing for the money.

Nevertheless, the truth is that the wealth is the product of industry, ambition, character and

untiring effort. The Special Task Force, (STF) of Uttar Pradesh, last year claimed to have

busted a major international racket involved, in supply of fake currency notes.

It seized counterfeit Indian currency worth a face value of Rs 16 lakh. The gang leader,

arrested in Lucknow with three of his aides, has confessed to have pumped into circulation

over Rs 2 crore in counterfeit currency in India in about two months. The gang members

arrested have been identified as Suhail Singh alias Ram Shanker Singh of Sikahira locality

under Khodare police station of Gonda-the gang leader-along with Sharma Paswan, Vinod

Kumar Misra and Sanjay Kumar Patel, all natives of Champaran in Bihar.

The gang was using a set of six women couriers from Champaran in Bihar and another set

of four hailing from Nepal. The fake currency notes had a different serial number. It

showed, that they had not merely been printed from a scanned image of a genuine note by

using coloured scanners and printers. In case the miscreants scan a genuine note and print



copies of it, the serial number of such counterfeit currency notes remain the same. Putting

a different serial number on each note explains that the counterfeit currency was being

printed at a very large scale.During interrogation, the accused revealed that the counterfeit

currency notes travelled to Uttar Pradesh from Nepal from two different routes: From

Nepal to UP via Bihar and directly to UP particularly through Sidhartnagar and

Maharajganj route. A Rs 1,000 denomination note was bought at the rate of Rs 500 to Rs

600 each while the Rs 500 denomination was bought for Rs 300 to Rs 400 each.

This whole ideology around economic terrorism? What is this guy serious or has India just

not had media attention for a while! And why would Pakistan want to effect the Indian

economy it does not make sense? The paper this stuff is printed on it worth too much to

allocate and even if they did print the notes it would take a shed load of an amount to

destabilise a economy. Take the example of England the amount of fake currency here is

ridiculous but it never has made news due to the amount it would take before and action

would be required. So take my advice and report something interesting such as India being

used by America and the uk to take control of all world matters and have total control of

individual states.



7. APPLICATIONS

Bank & financial Institution

Hospitals.

Schools & colleges.

Hotels & restaurants.

Shopping malls.

Indian railways.

Airport authority.

Other transport services.

Retail outlets & showrooms

Corporate

Co-operatives



8. APPENDIX

In this section, we touch upon a few things which may prove to be beneficial to avid

readers and who wish to take this idea a step further.

Microcontroller Interfacing Techniques:

Micro-controllers are useful to the extent that they communicate with other devices, such

as sensors, motors, switches, keypads, displays, memory and even other micro-controllers.

Many interface methods have been developed over the years to solve the complex problem

of balancing circuit design criteria such as features, cost, size, weight, power consumption,

reliability, availability, manufacturability. Many microcontroller designs typically mix

multiple interfacing methods. In a very simplistic form, a micro-controller system can be

viewed as a system that reads from (monitors) inputs, performs processing and writes to

(controls) outputs.

Interfacing relay to microcontroller

A relay is an electrical switch that opens and closes under the control of another electrical

circuit. In the original form, the switch is operated by an electromagnet to open or close

one or many sets of contacts. Because a relay is able to control an output circuit of higher

power than the input circuit, it can be considered to be, in a broad sense, a form of an

electrical amplifier.

Relay Operation

When a current flows through the coil, the resulting magnetic field attracts an armature that

is mechanically linked to a moving contact. The movement either makes or breaks a

connection with a fixed contact. When the current to the coil is switched off, the armature

is returned by a force approximately half as strong as the magnetic force to its relaxed

position. Usually this is a spring, but gravity is also used commonly in industrial motor

starters. Most relays are manufactured to operate quickly. In a low voltage application, this

is to reduce noise. In a high voltage or high current application, this is to reduce arcing.



9. REFERENCES

[1] Fake notes and its detection techniques using 89C51.Undergraduate final project no.

02010741/ELK/2005

[2] www.atmel.com

[3] en.wikipedia.org

[4] www.proteus.software.informer.com


Documents

Currency Counting Machine With Fake Note Detection Project Report