CHAPTER 1

INTRODUCTION

1.1 INTRODUCTION:-

India is world’s largest democracy. It is perceived to be charismatic one as it

accommodates cultural, regional, economical, social disparities and still is able to stand on its

own. Fundamental right to vote or simply voting in elections forms the basis of Indian

democracy.

In India all earlier elections be it state elections or centre elections a voter used to cast his/her

vote to his/her favorite candidate by putting the stamp against his/her name and then folding

the ballot paper as per a prescribed method before putting it in the Ballot box. This is a long,

time-consuming process and very much prone to errors.

This situation continued till election scene was completely changed by electronic voting

machine. No more ballot paper, ballot boxes, stamping, etc. all this condensed into a simple

box called ballot unit of the electronic voting machine.

EVM is capable of saving considerable printing stationery and transport of large volumes of

electoral material. It is easy to transport, store, and maintain. It completely rules out the chance

of invalid votes. Its use results in reduction of polling time, resulting in fewer problems in

electoral preparations, law and order, candidates' expenditure, etc. and easy

and accurate counting without any mischief at the counting centre. It is also eco friendly.

Our EVM consists mainly of two units - (a) Control Unit (CU) and (b) Ballot Unit (BU) with

cable for connecting it with Control unit. Both the units consists of one microcontroller (8052)

each. The CU consists of one LCD, one hex keypad and a couple of switches, while BU

consists of a candidate panel, a votecast panel and a buzzer, etc.

This project is based on assembly language programming. The software platform used in this

project are Keil uVision3 and “C”Programming.

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1.2 BACKGROUND OF VOTING SYSTEM

1.2.1 DEMOCRACY AND VOTING

Democracy has come to be accepted as the most preferred form of political system all over the

world. However, the success of a democratic structure is to be judged by the successes that can

be solely attributed to this system. There are various challenges before democracy. These are

foundational challenges, challenge of expansion and deepening of democracy. All of these are

dependent on how the democracy is perceived by people who form the government, participate

in formation of government and are benefited by it.

As we all know that India is world’s largest democracy. It is perceived to be charismatic one as

it accommodates cultural, regional, economical, social disparities and still is able to stand on

its own. India follows a federal form of government. It means that governance power is not

residing with one authority, but is distributed at various levels. In India power is distributed

between states and central authority.

What forms the basis of such vast and complex system of governance?

One needs not to be an Einstein to guess the answer. It is fundamental right to vote or simply

voting in elections.

Indian constitution provide every adult above the age of 18 years irrespective of his/her

religion, region, caste, creed, color, economic status, education and sex the essential right to

vote and elect her/his candidate to represent her/him.

Hence voting can be termed as backbone of not just democracy in India but all around the

world. Voting can be done in various ways. In early Roman Empire voting used to be done by

raising hands in favor or against. In board rooms voting is done in similar way, some write

their vote down, some choose to speak, some choose to cast vote using latest technology.

1.2.2 VOTING TECHNIQUES

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In India all earlier elections be it state elections or centre elections a voter used to cast his/her

vote to his/her favorite candidate by putting the stamp against his/her name and then folding

the ballot paper as per a prescribed method before putting it in the Ballot box. This is a long,

time-consuming process and very much prone to errors.

This method wanted voters to be skilled voters to know how to put a stamp, and methodical

folding of ballot paper. Millions of paper would be printed and heavy ballot boxes would be

loaded and unloaded to and from ballot office to polling station. All this continued till election

scene was completely changed by electronic voting machine. No more ballot paper, ballot

boxes, stamping, etc. all this condensed into a simple box called ballot unit of the electronic

voting machine.

The marking system of voting was introduced in 1962 to make it possible for a substantial

number of illiterate voters to indicate easily their preferences in choosing their representatives.

Over the years, there was a pronounced increase in the volume of work: crores of ballot papers

had to be printed and lakhs of ballot boxes had to be prepared, transported, and kept in storage;

and a great amount of time was taken up by the conduct of elections. To overcome these

difficulties, the Election Commission of India (ECI) thought of electronic gadgets. The

Electronics Corporation of India Ltd. (ECIL), Hyderabad, and Bharat Electronics Ltd. (BEL),

Bangalore, developed the electronic voting machine in 1981.

1.2.3 THE ELECTRONIC VOTING MACHINE

The complete EVM consists mainly of two units - (a) Control Unit and (b) Balloting Unit with

cable for connecting it with Control unit. A Balloting Unit caters upto 16 candidates. Four

Balloting Units linked together catering in all to 64 candidates can be used with one control

unit. The control unit is kept with the Presiding Officer and the Balloting Unit is used by the

voter for polling.

The Balloting Unit of EVM is a small Box-like device, on top of which each candidate and

his/her election symbol is listed like a big ballot paper. Against each candidate's name, a red

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LED and a blue button is provided. The voter polls his vote by pressing the blue button against

the name of his desired candidate.

How the Vote is cast with this EVM? 

The entire process is very easy to understand:

Like in earlier system, your name is called and you are asked to sign or put your thumb

impression in a register.

After your identification is done by Election Officer, an ink mark is put on your finger,

same as earlier.

Then the Election Officer gives you a slip that bears the Voter register number where

you signed or put your thumb impression.

You hand over this slip to the presiding officer who confirms the serial number and

permits you to vote by pressing the button of the Control Unit of EVM.

You are not given any ballot thereafter, and are sent to the EV Machine placed behind a

card board in a corner. The machine is placed in such a way that your polled vote will

be a secret.

On the Balloting Unit of EVM, you press the blue button placed in front of your

favorite candidate and release.

As soon as the button is pressed, the red LED indicator lights up and a whistle sound

comes from the machine. This signifies that your vote has been casted rightly. Now you

can come out.

In case of red LED not working, press the Blue button firmly again. If finding it

difficult, consult the Presiding Officer.

Your vote is complete safe and secret and there is no room for error as well. You can

rest assured that your vote is not going to be invalid in any case.

The Voting Machine is attached to the 'Control Unit'. When the user presses the button,

his vote is registered in the control unit and the number of votes for the respective

candidates is calculated automatically.

What Happens after Voting is over?

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After the hour fixed for the close of the poll and the last voter has recorded his vote, the EVM

is closed so that no further recording of votes in the machine is possible.

At the counting place, only the control unit is required for ascertaining the result of poll at the

polling station at which the EVM was used. The balloting unit is not required. All this used to

happen every time election were held.

1.2.4 BOOTH CAPTURE

A remarkable advantage is that rigging is not possible with the EVMs. In the ballot paper

system, the intruders can mark hundreds of ballots and put them into the ballot box in a matter

of a few minutes. This is not possible in voting machines as the machine is designed to be

capable of recording a maximum of five votes per minute. (The pace of polling can be set to

any predetermined number before manufacturing.) Thus, even for recording about 100 bogus

votes it would take the booth captors 20 to 25 minutes, during which time the law and order

officials may intervene to stop the rot. Moreover, as soon as the presiding officer apprehends

any mischief, he can stop the poll by pressing the special switch after which no votes can be

recorded.

The presiding officer of the polling station is empowered to close the control unit of the voting

machine to ensure "that no further vote can be recorded." There is no possibility of any bogus

votes being polled after the close of the poll and during the transit of the machines from the

polling booth to the counting centre. A vote once recorded in an EVM cannot be tampered

with, whereas in the ballot paper system the votes marked and put into the box can be pulled

out and destroyed. The EVMs are capable of retaining the memory of the votes recorded for a

period of three years. If the machine is tampered with in any respect either during the poll time

or at any time before the counting of votes, which will be easily detectable so that a fresh poll

can be ordered.

The EVMs have following advantages:

the saving of considerable printing stationery and transport of large volumes of

electoral material,

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easy transportation, storage, and maintenance,

no invalid votes,

reduction in polling time, resulting in fewer problems in electoral preparations, law and

order, candidates' expenditure, etc. and

easy and accurate counting without any mischief at the counting centre

Eco friendly.

As a matter of interest, “Diebold Accuvote System”, is a smarter system over conventional

EVMs used in India.

It is a new system of voting adopted by US government is DIEBOLD. Diebold system works on

Microsoft software; it has no seals on locks and panels to detect a tempering. It has a keyboard

interface (!!!) and the server was tested to have “Blaster” virus. One report on Wired says a

lady stumbled upon some files from Diebold, and found that the votes were stored in MS

Access files. It also has a PCMCIA Scandisk card for local storage. A touch screen GUI and a

network connection to send the results to a server after encrypting it with DES.

CHAPTER 2

WORKING OF EVM BALLOT UNIT

2.1 INTRODUCTION:-

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The EVM consist of two units: ballot unit (BU) and control unit (CU). Following figure shows

the complete EVM system, including the constituents of both units as well as the signals

exchanged between them.

Figure 2.1 Block diagram of EVM

2.2 BLOCK DIAGRAM OF BALLOT UNIT

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Figure 2.2: Block diagram of ballot unit

2.3 WORKING OF EVM BALLOT UNIT SYSTEM:-

To start with EVM Ballot unit is divided into 2 main sub sections:-

1) Motherboard board circuit

2) votecast LED and feedback panel.

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Fig 2.3 Circuit diagram of Ballot Unit

Explanation of each unit:-

1) Motherboard circuit:----

Motherboard circuitry consists of following components. :------

a) Microcontroller

b) Crystal Oscillator

c) Optocoupler

d) Buzzer

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Fig 2.4 Mother Board Circuit

e) Amplifier

f) Resistor and a capacitor network for reset circuit of microcontroller.

2) Votecast LED panel—

A vote cast LED panel is a section which will be at the voters end for the voters to cast their

votes. Here there are following components:----

a)8 push to on switch

b)8 Red LED’s

c)8 green LED’s

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Additionally one more red LED and push to on switch has been added for a machine ready

signal. Ideally this push to on switch is at the control panel but since here we have only a ballot

unit therefore this button is mounted on this panel.

General working of the combined circuit.:-----

The switch combination of the circuit is like this.

Fig 2.5 EVM Front Panel

Now as we can see that the port is connected just after the LED and resistor network, so ideally

when a 5 volt supply is being given to resistor and LED ,at the port we get 0 potential. now

every time when we push the button ,the microcontroller should read the push sequence. So a

high bit is given at ports 21 to 28.so when the button is pressed the LED will glow and the

circuit will get a ground. As a result the bit at the port will also change from high to low and

thus the microcontroller will easily identify the push to button switch and can easily predict the

vote.

Now when the microcontroller identified the

push to button switch it sends a feedback signal at ports 1 to 8(green LED’s) and the buzzer.

Due to internal programming of the microcontroller there is a continuous sounding of the

buzzer as well as lighting of the green LED.

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Working of Buzzer section---

When the button is pressed at the votecast LED panel. Then a high signal will flow at pin

no.16.This will initiate the optocoupler.

Fig 2.6 Working Principle of Opto-Coupler

As shown in the fig., when initiated the LED in the optocoupler will glow and then here the

photons will be initiated. The amplifier in the optocoupler will change +5 volt supply into -5

volt supply. The output of the optocoupler will be connected to the base of the amplifier.

The amplifier emitter side will be connected to the +5 volt supply. So the emitter base junction

will be forward biased. Thereby amplifying current. The output from the collector side will be

connected to the positive section of the buzzer. So then the buzzer will beep.

Now as there is delay of two seconds in the internal programming of the microcontroller

therefore the buzzer will beep for two seconds specifying that the vote has been counted.

Working of vote signal switch-----

When we press the vote signal switch, then the circuit will get completed by connection

through ground. Therefore this LED will glow, until one vote has been casted.

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2.4 WORKING OF PROGRAMMING

1 #include<regx52.h> //header file for inclusion of functions.

2 void delay (unsigned int); //user defined function.

3 sbit ready = P3^5; //defining port 3,5 pin as ready pin.

4 sbit buzzer = P3^6; //defining port 3,6 pin as buzzer pin.

5 sbit LED = P3^7; //defining port 3,7 pin as LED pin(single bit)

6 void main (void) //program function.

7 {

8 P2=0xFF; //giving port 2 all pins as high bit.

9 P3=0xFF; //giving port 3 all pins as high bit.

10 while(1) //for continuous looping.

11 {

12 while(ready==1); //checking ready signal as high.

13 LED=0; //giving low to LED pin.

14 while (P2==0xFF); //checking port 2 as high bit.

15 LED=1; //giving high to LED pin.

16 buzzer=0; //giving low to buzzer pin.

17 P1=P2; //assigning status equal.

18 delay(2000); //function call.

19 P1=P2=P3=0xFF; //assigning high to ports 1,2,3.

20 }

21 }

22 void delay (unsigned int time) //function definition.

23 {

24 unsigned int i,j; //variable data type.

25 for (i=1;i<time;i++) //loop for time delay.

26 for (j=1;j<110;j++); //loop for time delay.

27 }

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To start with, here we will allot high signal to ports 2 and 3.The ports 2 and 3 are connected to

vote-cast push to on button section and opto-coupler section respectively. Then we will enter

into loops which will continuous in nature as depicted in line 10.Then the microcontroller

checks if the ready signal is high or not. If the signal is high then the program will be hung

itself up there but if the signal changes from high to low then the microcontroller will change

the LED pin status to low and then the LED will glow. Again when the microcontroller

traverses through line 14 it will check whether port 2 is high or not. If it is high then the

program will hung itself up there, but if it is low then it will turn the LED off by putting high at

LED pin. Again it will a lot low at buzzer pin so that the buzzer will buzz. After that delay

loop will start which will give a delay of 2 seconds.

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CHAPTER 3

BASIC COMPONENT

3.1 MICROCONTROLLER:-

3.1.1 INTRODUCTION

Circumstances that we find ourselves in today in the field of microcontrollers had their

beginnings in the development of technology of integrated circuits. This development has

made it possible to store hundreds of thousands of transistors into one chip. That was a

prerequisite for production of microprocessors, and the first computers were made by adding

external peripherals such as memory, input-output lines, timers and other. Further increasing of

the volume of the package resulted in creation of integrated circuits. These integrated circuits

contained both processor and peripherals. That is how the first chip containing a

microcomputer, or what would later be known as a microcontroller came about.

3.1.2 DEFINITION OF A MICROCONTROLLER

Microcontroller, as the name suggests, are small controllers. They are like single chip

computers that are often embedded into other systems to function as processing/controlling

unit. For example, the remote control you are using probably has microcontrollers inside that

do decoding and other controlling functions. They are also used in automobiles, washing

machines, microwave ovens, toys ... etc, where automation is needed.

The key features of microcontrollers include:

High Integration of Functionality

Microcontrollers sometimes are called single-chip computers because they have on-

chip memory and I/O circuitry and other circuitries that enable them to function as

small standalone computers without other supporting circuitry.

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Field Programmability, Flexibility

Microcontrollers often use EEPROM or EPROM as their storage device to allow field

programmability so they are flexible to use. Once the program is tested to be correct

then large quantities of microcontrollers can be programmed to be used in embedded

systems.

Easy to Use

Assembly language is often used in microcontrollers and since they usually follow

RISC architecture, the instruction set is small. The development package of

microcontrollers often includes an assembler, a simulator, a programmer to "burn" the

chip and a demonstration board. Some packages include a high level language compiler

such as a C compiler and more sophisticated libraries.

Most microcontrollers will also combine other devices such as:

A Timer module to allow the microcontroller to perform tasks for certain time periods.

A serial I/O port to allow data to flow between the microcontroller and other devices

such as a PC or another microcontroller.

An ADC to allow the microcontroller to accept analogue input data for processing.

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Fig 3.1.1: Showing a typical microcontroller device and its

different subunits

The heart of the microcontroller is the CPU core.  In the past this has traditionally been based

on an 8-bit microprocessor unit.

3.1.3 PIN DIAGRAM OF MICROCONTROLLER 8952 :-

Fig 3.1.2 Pin Diagram of 8952 Microcontroller

3.1.4 PIN DESCRIPTION OF 8952 MICROCONTROLLER:-

1.VCC :- Supply voltage.

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2.GND :-Ground.

3.Port 0 :-Port 0 is an 8-bit open drain bi-directional I/O port. As an output port, each pin can

sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high

impedance inputs.Port 0 can also be configured to be the multiplexed loworder address/data

bus during accesses to external program and data memory. In this mode, P0 has internal

pullups. Port 0 also receives the code bytes during Flash programming and outputs the code

bytes during program verification. External pullups are required during program verification.

4.Port 1 :-Port 1 is an 8-bit bi-directional I/O port with internal pullups. The Port 1 output

buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled

high by the internal pullups and can be used as inputs. As inputs, Port 1 pins that are externally

being pulled low will source current (IIL) because of the internal pullups. In addition, P1.0 and

P1.1 can be configured to be the timer/counter 2 external count input (P1.0/T2) and the

timer/counter 2 trigger input (P1.1/T2EX), respectively, as shown in the following table. Port 1

also receives the low-order address bytes during Flash programming and verification.

5. Port 2 :-Port 2 is an 8-bit bi-directional I/O port with internal pullups. The Port 2 output

buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled

high by the internal pullups and can be used as inputs. As inputs, Port 2 pins that are externally

being pulled low will source current (IIL) because of the internal pullups. Port 2 emits the

high-order address byte during fetches from external program memory and during accesses to

external data memory that use 16-bit addresses (MOVX @ DPTR). In this application, Port 2

uses strong internal pull-ups when emitting 1s. During accesses to external data memory that

use 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function

Register. Port 2 also receives the high-order address bits and some control signals during Flash

programming and verification.

6. Port 3:- Port 3 is an 8-bit bi-directional I/O port with internal pullups. The Port 3 output

buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins, they are pulled

high by the internal pullups and can be used as inputs. As inputs, Port 3 pins that are externally

being pulled low will source current (IIL) because of the pullups. Port 3 also serves the

functions of various special features of the AT89C52. Port 3 also receives some control signals

for Flash programming and verification.

7. RST:- Reset input. A high on this pin for two machine cycles while the oscillator is running

resets the device.

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8. ALE/PROG:- Address Latch Enable is an output pulse for latching the low byte of the

address during accesses to external memory. This pin is also the program pulse input (PROG)

during Flash programming. In normal operation, ALE is emitted at a constant rate of 1/6 the

oscillator frequency and may be used for external timing or clocking purposes. Note, however,

that one ALE pulse is skipped during each access to external data memory. If desired, ALE

operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active

only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting

the ALE-disable bit has no effect if the microcontroller is in external execution mode.

9.PSEN:-Program Store Enable is the read strobe to external program memory. When the

AT89C52 is executing code from external program memory, PSEN is activated twice each

machine cycle, except that two PSEN activations are skipped during each access to external

data memory.

10.EA/VPP:-External Access Enable. EA must be strapped to GND inorder to enable the

device to fetch code from external program memory locations starting at 0000H up to FFFFH.

Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset.

EA should be strapped to VCC for internal program executions. This pin also receives the 12-

volt programming enable voltage (VPP) during Flash programming when 12-volt

programming is selected.

11.XTAL1 :-Input to the inverting oscillator amplifier and input to the internal clock operating

circuit.

12.XTAL2: -Output from the inverting oscillator amplifier.

3.1.5 MEMORY UNIT

Memory is part of the microcontroller whose function is to store data. 

The easiest way to explain it is to describe it as one big closet with lots of drawers. If we

suppose that we marked the drawers in such a way that they can not be confused, any of their

contents will then be easily accessible. It is enough to know the designation of the drawer and

so its contents will be known to us for sure.

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Figure 3.1.3: Simplified model of a memory unit

Memory components are exactly like that. For a certain input we get the contents of a certain

addressed memory location and that's all. Two new concepts are brought to us: addressing and

memory location. Memory consists of all memory locations, and addressing is nothing but

selecting one of them. This means that we need to select the desired memory location on one

hand, and on the other hand we need to wait for the contents of that location. Besides reading

from a memory location, memory must also provide for writing onto it. This is done by

supplying an additional line called control line. We will designate this line as R/W

(read/write). Control line is used in the following way: if r/w=1, reading is done, and if

opposite is true then writing is done on the memory location. Memory is the first element, and

we need a few operation of our microcontroller.

The amount of memory contained within a microcontroller varies between different

microcontrollers. Some may not even have any integrated memory (e.g. Hitachi 6503, now

discontinued). However, most modern microcontrollers will have integrated memory. The

memory will be divided up into ROM and RAM, with typically more ROM than RAM.

Typically, the amount of ROM type memory will vary between around 512 bytes and 4096

bytes, although some 16 bit microcontrollers such as the Hitachi H8/3048 can have as much as

128 Kbytes of ROM type memory.

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ROM type memory, as has already been mentioned, is used to store the program code. ROM

memory can be ROM (as in One Time Programmable memory), EPROM, or EEPROM.

The amount of RAM memory is usually somewhat smaller, typically ranging between 25 bytes

to 4 Kbytes.

RAM is used for data storage and stack management tasks. It is also used for register stacks

(as in the microchip PIC range of microcontrollers).

3.1.6 CENTRAL PROCESSING UNIT

Let add 3 more memory locations to a specific block that will have a built in capability to

multiply, divide, subtract, and move its contents from one memory location onto another. The

part we just added in is called "central processing unit" (CPU). Its memory locations are called

registers.

Figure 3.1.4: Simplified central processing unit with three

registers

Registers are therefore memory locations whose role is to help with performing various

mathematical operations or any other operations with data wherever data can be found. Look at

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the current situation. We have two independent entities (memory and CPU) which are

interconnected, and thus any exchange of data is hindered, as well as its functionality. If, for

example, we wish to add the contents of two memory locations and return the result again back

to memory, we would need a connection between memory and CPU. Simply stated, we must

have some "way" through data goes from one block to another.

3.1.7 BUS

That "way" is called "bus". Physically, it represents a group of 8, 16, or more wires.

There are two types of buses: address and data bus. The first one consists of as many lines as

the amount of memory we wish to address and the other one is as wide as data, in our case 8

bits or the connection line. First one serves to transmit address from CPU memory, and the

second to connect all blocks inside the microcontroller.

Fig 3.1.5: Showing connection between memory and central

unit using buses

As far as functionality, the situation has improved, but a new problem has also appeared: we

have a unit that's capable of working by itself, but which does not have any contact with the

outside world, or with us! In order to remove this deficiency, let's add a block which contains

several memory locations whose one end is connected to the data bus, and the other has

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connection with the output lines on the microcontroller which can be seen as pins on the

electronic component.

3.1.8 INPUT-OUTPUT UNIT

Those locations we've just added are called "ports". There are several types of ports: input,

output or bidirectional ports. When working with ports, first of all it is necessary to choose

which port we need to work with, and then to send data to, or take it from the port.

Figure 3.1.6: Simplified input-output unit communicating with

external world

When working with it the port acts like a memory location. Something is simply being written

into or read from it, and it could be noticed on the pins of the microcontroller.

3.2 VOLTAGE REGULATOR:-

Description :- The MC78XX/LM78XX/MC78XXA series of three terminal positive

regulators are available in the TO-220/D-PAK package and with several fixed output voltages,

making them useful in a wide range of applications. Each type employs internal current

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limiting thermal shut down and safe operating area protection, making it essentially

indestructible. If adequate heat sinking

is provided, they can deliver over 1A output current Although designed primarily as fixed

voltage regulators, these devices can be used with external components to obtain adjustable

voltages and currents.

Features • Output Current up to 1A

• Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V

• Thermal Overload Protection

• Short Circuit Protection

• Output Transistor Safe Operating Area Protection

3.3 LED:-

Fig 3.3.1 LED

3.3.1 INTRODUCTION

A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator

lamps in many devices, and are increasingly used for lighting. Introduced as a practical

electronic component in 1962, early LEDs emitted low-intensity red light, but modern versions

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are available across the visible, ultraviolet and infrared wavelengths, with very high

brightness.

The LED is based on the semiconductor diode. When a diode is forward biased (switched

on),electrons are able to recombine with holes within the device, releasing energy in the form

of photons. This effect is called electroluminescence and the color of the light (corresponding

to the energy of the photon) is determined by the energy gap of the semiconductor. An LED is

usually small in area (less than 1 mm2), and integrated optical components are used to shape its

radiation pattern and assist in reflection.

LEDs present many advantages over incandescent light sources including lower energy

consumption, longer lifetime, improved robustness, smaller size, faster switching, and greater

durability and reliance. However, they are relatively expensive and require more

precise current and heat management than traditional light sources. Current LED products for

general lighting are more expensive to buy than fluorescent lamp sources of comparable

output.

They also enjoy use in applications as diverse as replacements for traditional light sources in

automotive lighting (particularly indicators) and in traffic signals. The compact size of LEDs

has allowed new text and video displays and sensors to be developed, while their high

switching rates are useful in advanced communications technology.

3.3.2 PRACTICAL USE:-

The first commercial LEDs were commonly used as replacements for incandescent indicators,

and in seven-segment displays, first in expensive equipment such as laboratory and electronics

test equipment, then later in such appliances as TVs, radios, telephones, calculators, and even

watches (see list of signal applications). These red LEDs were bright enough only for use as

indicators, as the light output was not enough to illuminate an area. Later, other colors became

widely available and also appeared in appliances and equipment. As the LED materials

technology became more advanced, the light output was increased, while maintaining the

efficiency and the reliability to an acceptable level. The invention and development of the high

power white light LED led to use for illumination (see list of illumination applications). Most

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LEDs were made in the very common 5 mm T1¾ and 3 mm T1 packages, but with increasing

power output, it has become increasingly necessary to shed excess heat in order to maintain

reliability, so more complex packages have been adapted for efficient heat dissipation.

Packages for state-of-the-art high power LEDs bear little resemblance to early LEDs.

Fig 3.3.2 Parts of an LED

Fig 3.3.3 The inner workings of an LED

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Fig 3.3.4 LED CHARACTERISTICS

3.3.3 COLOURS & MATERIALS:-

Conventional LEDs are made from a variety of inorganic semiconductor materials, the

following table shows the available colors with wavelength range, voltage drop and material:

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Colour Wavelength (nm) Voltage (V) Semiconductor Material

Red 610 < λ < 7601.63 < ΔV <

2.03

Aluminium gallium arsenide (AlGaAs)

Gallium arsenide phosphide (GaAsP)

Aluminium gallium indium

phosphide (AlGaInP)

Gallium(III) phosphide (GaP)

Green 500 < λ < 5701.9< ΔV <

4.0

Indium gallium

nitride (InGaN) / Gallium(III)

nitride (GaN)

Gallium(III) phosphide (GaP)

Aluminium gallium indium

phosphide (AlGaInP)

Aluminium gallium phosphide (AlGaP)

Table 3.1 Led Colour ‘S Materials

3.3.4 TYPES :-

Fig 3.3.5 Types of LED

LEDs are produced in a variety of shapes and sizes. The 5 mm cylindrical package (red, fifth

from the left) is the most common, estimated at 80% of world production. The color of the

plastic lens is often the same as the actual color of light emitted, but not always. For instance,

purple plastic is often used for infrared LEDs, and most blue devices have clear housings.

There are also LEDs in SMT packages, such as those found on blinkiesand on cell phone

keypads

The main types of LEDs are miniature, high power devices and custom designs such as

alphanumeric or multi-color.

3.3.5 ELECTRICAL POLARITY :-

As with all diodes, current flows easily from p-type to n-type material. However, no current

flows and no light is produced if a small voltage is applied in the reverse direction. If the

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reverse voltage becomes large enough to exceed the breakdown voltage, a large current flows

and the LED may be damaged. If the reverse current is sufficiently limited to avoid damage,

the reverse-conducting LED is a useful noise diode.

3.3.6 ADVANTAGES :-

Efficiency: LEDs produce more light per watt than incandescent bulbs.

Color: LEDs can emit light of an intended color without the use of color filters that

traditional lighting methods require. This is more efficient and can lower initial costs.

Size: LEDs can be very small (smaller than 2 mm2) and are easily populated onto

printed circuit boards.

On/Off time: LEDs light up very quickly. A typical red indicator LED will achieve full

brightness in microseconds. LEDs used in communications devices can have even faster

response times.

Cycling: LEDs are ideal for use in applications that are subject to frequent on-off

cycling, unlike fluorescent lamps that burn out more quickly when cycled frequently,

or HID lamps that require a long time before restarting.

Dimming: LEDs can very easily be dimmed either by Pulse-width modulation or

lowering the forward current.

Cool light: In contrast to most light sources, LEDs radiate very little heat in the form

of IR that can cause damage to sensitive objects or fabrics. Wasted energy is dispersed as

heat through the base of the LED.

Slow failure: LEDs mostly fail by dimming over time, rather than the abrupt burn-out

of incandescent bulbs.

Lifetime: LEDs can have a relatively long useful life. One report estimates 35,000 to

50,000 hours of useful life, though time to complete failure may be longer. Fluorescent

tubes typically are rated at about 10,000 to 15,000 hours, depending partly on the

conditions of use, and incandescent light bulbs at 1,000–2,000 hours.

Shock resistance: LEDs, being solid state components, are difficult to damage with

external shock, unlike fluorescent and incandescent bulbs which are fragile.

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Focus: The solid package of the LED can be designed to focus its light. Incandescent

and fluorescent sources often require an external reflector to collect light and direct it in a

usable manner.

Toxicity: LEDs do not contain mercury, unlike fluorescent lamps.

Disadvantages

High initial price: LEDs are currently more expensive, price per lumen, on an initial

capital cost basis, than most conventional lighting technologies. The additional expense

partially stems from the relatively low lumen output and the drive circuitry and power

supplies needed.

Temperature dependence: LED performance largely depends on the ambient

temperature of the operating environment. Over-driving the LED in high ambient

temperatures may result in overheating of the LED package, eventually leading to device

failure. Adequate heat-sinkingis required to maintain long life. This is especially important

when considering automotive, medical, and military applications where the device must

operate over a large range of temperatures, and is required to have a low failure rate.

Voltage sensitivity: LEDs must be supplied with the voltage above the threshold and a

current below the rating. This can involve series resistors or current-regulated power

supplies.

Light quality: Most cool-white LEDs have spectra that differ significantly from

a black body radiator like the sun or an incandescent light. The spike at 460 nm and dip at

500 nm can cause the color of objects to be perceived differently under cool-white LED

illumination than sunlight or incandescent sources, due to metamerism, red surfaces being

rendered particularly badly by typical phosphor based cool-white LEDs. However, the

color rendering properties of common fluorescent lamps are often inferior to what is now

available in state-of-art white LEDs.

Area light source: LEDs do not approximate a “point source” of light, but rather

a lambertian distribution. So LEDs are difficult to use in applications requiring a spherical

light field. LEDs are not capable of providing divergence below a few degrees. This is

contrasted with lasers, which can produce beams with divergences of 0.2 degrees or less.

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Blue hazard: There is a concern that blue LEDs and cool-white LEDs are now capable

of exceeding safe limits of the so-called blue-light hazard as defined in eye safety

specifications such as ANSI/IESNA RP-27.1-05: Recommended Practice for

Photobiological Safety for Lamp and Lamp Systems.

Blue pollution: Because cool-white LEDs (i.e., LEDs with high color temperature)

emit proportionally more blue light than conventional outdoor light sources such as high-

pressure sodium lamps, the strong wavelength dependence of Rayleigh scattering means

that cool-white LEDs can cause more light pollution than other light sources.

The International Dark-Sky Association discourages the use of white light sources with

Correlated Color Temperature above 3,000 K.

3.4 CRYSTAL OSCILLATOR:-

Fig 3.4.1 Connection Diagram of Crystal Oscillator

A crystal oscillator is an electronic 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

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

resonator used is the quartz crystal, so oscillator circuits designed around them were called

"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 small

devices for consumer devices such as wristwatches, clocks, radios, computers, and cellphones.

Quartz crystals are also found inside test and measurement equipment, such as counters, signal

generators, and oscilloscopes.

3.4.1 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

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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.

3.4.2 MODELING:-

Electrical model

Fig 3.4.2 Electronic symbol for a piezoelectric crystal resonator

Fig 3.4.3 Schematic symbol and equivalent circuit for a quartz

crystal in an oscillator

3.5 TRANSISTORS:-

3.5.1 INTRODUCTION:-

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In electronics, a transistor is a semiconductor device commonly used to

amplify or switch electronic signals. A transistor is made of a solid piece of a semiconductor

material, with at least three terminals for connection to an external circuit. A voltage or current

applied to one pair of the transistor’s terminals changes the current flowing through another

pair of terminals. Because the controlled (output) power can be much larger than the

controlling (input) power, the transistor provides amplification of a signal. The transistor is the

fundamental building block of modern electronic devices, and is used in radio, telephone,

computer and other electronic systems. Some transistors are packaged individually but most

are found in integrated circuits.

3.5.2 TYPES:-

The bipolar junction transistor (BJT) was the first type of transistor to be mass-produced.

Bipolar transistors are so named because they conduct by using both majority and minority

carriers. The three terminals of the BJT are named emitter, base and collector. Two p-n

junctions exist inside a BJT: the base/emitter junction and base/collector junction. "The [BJT]

is useful in amplifiers because the currents at the emitter and collector are controllable by the

relatively small base current."In an NPN transistor operating in the active region, the emitter-

base junction is forward biased, and electrons are injected into the base region. Because the

base is narrow, most of these electrons will diffuse into the reverse-biased base-collector

junction and be swept into the collector; perhaps one-hundredth of the electrons will recombine

in the base, which is the dominant mechanism in the base current. By controlling the number

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BJT

PNP NPN

Fig 3.5.1 Types of

transistor

of electrons that can leave the base, the number of electrons entering the collector can be

controlled.

3.6 RESISTORS:-

Fig 3.6.1 Resistor

Resistors are components that have a predetermined resistance.

Resistance determines how much current will flow through a component. Resistors are used to

control voltages and currents. A very high resistance allows very little current to flow. Air has

very high resistance. Current almost never flows through air. (Sparks and lightning are brief

displays of current flow through air. The light is created as the current burns parts of the air.) A

low resistance allows a large amount of current to flow. Metals have very low resistance. That

is why wires are made of metal. They allow current to flow from one point to another point

without any resistance. Wires are usually covered with rubber or plastic. This keeps the wires

from coming in contact with other wires and creating short circuits. High voltage power lines

are covered with thick layers of plastic to make them safe, but they become very dangerous

when the line breaks and the wire is exposed and is no longer separated from other things by

insulation.

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Resistance is given in units of ohms. (Ohms are named after Mho Ohms who played with

electricity as a young boy in Germany.) Common resistor values are from 100 ohms to 100,000

ohms. Each resistor is marked with colored stripes to indicate its resistance. 

3.7 CAPACITOR:-

Now suppose you want to control how the current in your circuit changes (or not

changes) over time. Now why would you? Well radio signals require very fast current changes.

Robot motors cause current fluctuations in your circuit which you need to control. What do

you do when batteries cannot supply current as fast as you circuit drains them? How do you

prevent sudden current spikes that could fry your robot circuitry? The solution to this is

+ -

Fig 3.7.1 Symbol of Capacitor

Capacitors are like electron storage banks. If your circuit is running low, it will deliver

electrons to your circuit.

In our water analogy, think of this as a water tank with water always flowing in, but with

drainage valves opening and closing. Since capacitors take time to charge, and time to

discharge, they can also be used for timing circuits. Timing circuits can be used to generate

signals such as PWM or be used to turn on/off motors in solar powered BEAM robots.

Quick note, some capacitors are polarized, meaning current can only flow one direction

through them. If a capacitor has a lead that is longer than the other, assume the longer lead

must always connect to positive.

3.7.1 ELECTROLYTIC CAPACITOR:-

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Fig 3.7.2 Electrolyte Capacitor

An electrolytic capacitor is a type of capacitor that uses an ionic conducting liquid as one of

its plates. Typically with a larger capacitance per unit volume than other types, they are

valuable in relatively high-current and low-frequency electrical circuits. This is especially the

case in power-supply filters, where they store charge needed to moderate output voltage and

current fluctuations, in rectifier output. They are also widely used as coupling capacitors in

circuits where AC should be conducted but DC should not.

3.8 BUZZER :-

Fig 3.8.1 Buzzer

A Buzzer or Beeper is a signaling device, usually electronic, typically used in automobiles,

household appliances such as microwave ovens, or game shows.

It most commonly consists of a number of switches or sensors connected to a control unit that

determines if and which button was pushed or a preset time has lapsed, and usually illuminates

a light on the appropriate button or control panel, and sounds a warning in the form of a

continuous or intermittent buzzing or beeping sound.

Initially this device was based on an electromechanical system which was identical to

an electric bell without the metal gong (which makes the ringing noise). Often these units were

anchored to a wall or ceiling and used the ceiling or wall as a sounding board. Another

implementation with some AC-connected devices was to implement a circuit to make the AC

current into a noise loud enough to drive a loudspeaker and hook this circuit up to an 8-ohm

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speaker. Nowadays, it is more popular to use a ceramic-based piezoelectric sounder which

makes a high-pitched tone. Usually these were hooked up to "driver" circuits which varied the

pitch of the sound or pulsed the sound on and off.

In game shows it is also known as a "lockout system" because when one person signals

("buzzes in"), all others are locked out from signalling. Several game shows have large buzzer

buttons which are identified as "plungers". The buzzer is also used to signal wrong answers

and when time expires on many game shows, such as Wheel of Fortune, Family Feud and The

Price is Right.

The word "buzzer" comes from the rasping noise that buzzers made when they were

electromechanical devices, operated from stepped-down AC line voltage at 50 or 60 cycles.

Other sounds commonly used to indicate that a button has been pressed are a ring or a beep.

3.9 OPTO-COUPLER :-

3.9.1 INTRODUCTION:-

In electronics, an opto-isolator (or optical isolator, optical coupling

device, optocoupler,photocoupler, or photoMOS) is a device that uses a

short optical transmission path to transfer an electronic signal between elements of a circuit,

typically a transmitter and a receiver, while keeping them electrically isolated—since the

electrical signal is converted to a light beam, transferred, then converted back to an electrical

signal, there is no need for electrical connection between the source and destination circuits.

Isolation between input and output is rated at 7500 Volt peak for 1 second for a typical

component costing less than 1 US$ in small quantities.

The opto-isolator is simply a package that contains both an infrared light-emitting diode (LED)

and a photo-detector such as a photosensitive silicon diode, transistor Darlington pair,

or silicon controlled rectifier (SCR). The wave-length responses of the two devices are tailored

to be as identical as possible to permit the highest measure of coupling possible. Other

circuitry—for example an output amplifier—may be integrated into the package. An opto-

isolator is usually thought of as a single integrated package, but opto-isolation can also be

achieved by using separate devices.

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Digital opto-isolators change the state of their output when the input state

changes; analog isolators produce an analog signal which reproduces the input.

3.9.2 CONFIGURATIONS :-

Fig 3.9.1 Schematic diagram of a very simple opto-isolator with an LED and phototransistor.

The dashed line represents the isolation barrier, over which there is no electrical contact.

A common implementation is a LED and a phototransistor in a light-tight housing to exclude

ambient light and without common electrical connection, positioned so that light from the LED

will impinge on the photodetector. When an electrical signal is applied to the input of the opto-

isolator, its LED lights and illuminates the photodetector, producing a corresponding electrical

signal in the output circuit. Unlike atransformer the opto-isolator allows DC coupling and can

provide any desired degree of electrical isolation and protection from serious overvoltage

conditions in one circuit affecting the other. A higher transmission ratio can be obtained by

using a Darlington instead of a simple phototransistor, at the cost of reduced noise immunity

and higher delay.

With a photodiode as the detector, the output current is proportional to the intensity of incident

light supplied by the emitter. The diode can be used in a photovoltaic mode or

a photoconductive mode. In photovoltaic mode, the diode acts as a current source in parallel

with a forward-biased diode. The output current and voltage are dependent on the load

impedance and light intensity. In photoconductive mode, the diode is connected to a supply

voltage, and the magnitude of the current conducted is directly proportional to the intensity of

light. This optocoupler type is significantly faster than photo transistor type, but the

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transmission ratio is very low; it is common to integrate an output amplifier circuit into the

same package.

The optical path may be air or a dielectric waveguide. When high noise immunity is required

an optical conductive shield can be integrated into the optical path. The transmitting and

receiving elements of an optical isolator may be contained within a single compact module, for

mounting, for example, on a circuit board; in this case, the module is often called an opto-

isolator or opto-isolator. The photo-sensor may be a photocell,photo-transistor, or an optically

triggered SCR or TRIAC. This device may in turn operate a power relay or contactor.

Analog opto-isolators often have two independent, closely matched output phototransistors,

one of which is used to linearize the response using negative feedback.

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3.10 PUSH TO ON SWITCH :-

Fig 3.10.1 Push to on switch

A Push Switch or Push to make switch, allows electricity to flow between its two contacts

when held in. When the button is released, the circuit is broken. So it is called a non- latching

switch.

Other forms are push to break which, does the opposite. I.e when the button is not pressed,

electricity can flow, but when it is pressed the circuit is broken.

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CHAPTER 4

PRINTED CIRCUIT BOARD

4.1 PRINTED CIRCUIT BOARDS

The use of miniaturization and sub miniaturization in electronic equipment design has been

responsible for the introduction of a new technique in inters component wiring and assembly

that is popularly known as printed circuit.

The printed circuit boards (PCBs) consist of an insulating substrate material with metallic

circuitry photo chemically formed upon that substrate. Thus PCB provides sufficient

mechanical support and necessary electrical connections for an electronic circuit.

Advantages of printed circuit boards: -

1) Circuit characteristics can be maintained without introducing variations

inter circuit capacitance.

2) Wave soldering or vapour phase reflow soldering can mechanize component

wiring and assembly.

3) Mass production can be achieved at lower cost.

4) The size of component assembly can be reduced with corresponding

decrease in weight.

5) Inspection time is reduced as probability of error is eliminated.

4.2 TYPES OF PCB’S: -

There are four major types of PCB’s: -

1) Single sided PCB: - In this, copper tracks are on one side of the board, and are the

simplest form of PCB. These are simplest to manufacture thus have low production

cost.

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2) Double sided PCB:- In this, copper tracks are provided on both sides of the substrate.

To achieve the connections between the boards, hole plating is done, which increase the

manufacturing complexity.

3) Multilayered PCB: - In this, two or more pieces of dielectric substrate material with

circuitry formed upon them are stacked up and bonded together. Electrically

connections are established from one side to the other and to the layer circuitry by

drilled holes, which are subsequently plated through copper.

4) Flexible PCB: - Flexible circuit is basically a highly flexible variant of the conventional

rigid printed circuit board theme.

4.3 PCB MANUFACTURING PROCESS: -

There are a number of different processes, which are used to

manufacture a PCB, which is ready for component assembly, from a copper clad base material.

These processes are as follows

4.3.1 PRE PROCESSING: - This consists of initial preparation of a copper clad laminate

ready for subsequent processing. Next is to drill tooling holes. Passing a board through rollers

performs cleaning operation.

4.3.2 PHOTOLITHOGRAPHY: – This process for PCBs involves the exposure of a photo

resist material to light through a mask. This is used for defining copper track and land patterns.

4.3.3. ETCHING: -The etching process is performed by exposing the surface of the board to

an etchant solution which dissolves away the exposed copper areas .The different solutions

used are: FeCl, CuCl, etc.

4.3.4 DRILLING: – Drilling is used to create the component lead holes and through holes in a

PCB .The drilling can be done before or after the track areas have been defined.

4.3.5 SOLDER MASKING: - It is the process of applying organic coatings selectively to

those areas where no solder wettings is needed .The solder mask is applied by screen-printing.

4.3.6 PRE METAL PLATING :–The plating is done to ensure protection of the copper tracks

and establish connection between different layers of multiplayer boards. PCBs are stacked

before being taken for final assembly of components .The PCB should retain its solder ability.

4.3.7 BARE BOARD TESTING: - Each board needs to ensure that the required connections

exist, that there are no short circuits and holes are properly placed .The testing usually consists

of visual inspection and continuity testing.

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4.4 PCB LAYOUT OF BALLOT UNIT:-

Fig 4.1 PCB Lay Out Of Mother Board Circuit

Fig 4.2 PCB Lay Out of EVM Front Panel

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CHAPTER 5 MICROCONTROLLER PROGRAMMING

“C” LANGUAGE CODE :-

#include<regx52.h>void delay (unsigned int);sbit ready = P3^5;sbit buzzer = P3^6;sbit LED = P3^7;void main (void){P2=0xFF;P3=0xFF;while(1){

while(ready==1);LED=0;while (P2==0xFF);LED=1;buzzer=0;P1=P2;delay(2000);P1=P2=P3=0xFF;

}}void delay (unsigned int time){unsigned int i,j;for (i=1;i<time;i++)for (j=1;j<110;j++);}

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RESULT AND CONCLUSION

1. The EVM consists of a control unit (CU) and ballot unit (BU), out of which CU is working

independently and in collaboration with microcontroller.

2. The BU is accepting vote signal in voting mode and is responding accordingly.

3. In voting mode, BU communicates with microcontroller in order to exchange various

signals.

4.In case of low ‘vote signal’ the ballot unit is not at all responding to push to button switch

which is an interfacing medium between the voter and the ballot unit.

5. An interfacing between the voter and the and balolot unit is running successfully with the

help of votecast LED panel.

6. Feedback system of the control unit is running successfully with the help of LED system.

In total, the complete system (including all the hardware components and software routines) is

working as per the initial specifications and requirements of our project. Because of the

creative nature of the design, some features can further be fine-tuned and can become more

user friendly. So certain aspects of the system can be modified as operational experience is

gained with it. As the users work with the system, they develop various new ideas for the

development and enhancement of the project.

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APPLICATIONS & ADVANTAGES

Fast track voting which could be used in small scale elections, like resident welfare

association, “panchayat” level election and other society level elections.

It could also be used to conduct opinion polls during annual share holders meeting.

It could also be used to conduct general assembly elections where number of

candidates are less than or equal to eight in the current situation.

It could be used at places where there is no electricity as the thing is operational with

the help of a simple 5 volt battery.

It could well become a fine example of using environment friendly resources as there

is no need for having lakhs of ballot papers as was used in older system of voting.

It involves very less time for a voter to actually cast its vote unlike conventional

method where it becomes very cumbersome to handle ballot papers.

It is more fast and reliable.

FUTURE SCOPE

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Number of candidates could be increased by using other microcontroller or an 8255 IC.

It could be interfaced with printer to get the hard copy of the result almost instantly from

the machine itself.

It could also be interfaced with the personal computer and result could be stored in the

central server and its backup could be taken on the other backend servers.

Again, once the result is on the server it could be relayed on the network to various

offices of the election conducting authority. Thus our project could make the result

available any corner of the world in a matter of seconds

In days of using nonpolluting and environment friendly resources of energy,it could pose

a very good example.

REFRENCES AND BIBLOGRAPHY

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1. Muhammad Ali Mazidi , Janice Gillispie Mazidi, Rolin D. Mckinlay. Second edition, “THE 8051 MICROCONTROLLER AND EMBEDDED SYSTEM”

2. K. J. Ayala. Third edition, “The 8051 MICROCONTROLLER”3.Millman & Halkias. “INTEGRATED ELECTRONICS”.4. www.wikipedia.com5. www.8051microcontrollerprojects.com6.www.datasheet4u.com7.www.rickey’sworld.com

DATA SHEET OF TRANSISTOR BC 557:-

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