REPORT on Electronic Voting Machine evm.doc (Size: 1.01 MB / Downloads: 1783)
India is worldâ„¢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 CProgramming.
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 worldâ„¢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
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 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
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,
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
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.
WORKING OF EVM BALLOT UNIT
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
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.
Fig 2.3 Circuit diagram of Ballot Unit
Explanation of each unit:-
1) Motherboard circuit:----
Motherboard circuitry consists of following components. :------
b) Crystal Oscillator
Fig 2.4 Mother Board Circuit
f) Resistor and a capacitor network for reset circuit of microcontroller.
2) Votecast LED panelâ€
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 LEDâ„¢s
c)8 green LEDâ„¢s
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 LEDâ„¢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.
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.
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.
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.
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.
22 void delay (unsigned int time) //function definition.
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.
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.
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.
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.
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.
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.
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.
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.
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 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.
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 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:-
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 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.
Â¢ Output Current up to 1A
Â¢ Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V
Â¢ Thermal Overload Protection
Â¢ Short Circuit Protection
Â¢ Output Transistor Safe Operating Area Protection
Fig 3.3.1 LED
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 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 LEDs were made in the very common 5 mm T1Ã‚Â¾ 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
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:
Colour Wavelength (nm)
Voltage (V) Semiconductor Material
610 < < 760 1.63 < V < 2.03 Aluminium gallium arsenide (AlGaAs)
Gallium arsenide phosphide (GaAsP)
Aluminium gallium indium phosphide (AlGaInP)
Gallium(III) phosphide (GaP) Green
500 < < 570 1.9< V < 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 ËœS 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 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 1,000â€œ2,000 hours.
Shock resistance: LEDs, being solid state components, are difficult to damage with external shock, unlike fluorescent and incandescent bulbs which are fragile.
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.
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.
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 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 (2Ãƒâ€”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.
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.
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
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 transistorâ„¢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.
Fig 3.5.1 Types of transistor
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 of electrons that can leave the base, the number of electrons entering the collector can be controlled.
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.
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.
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:-
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 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 :-
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 isolatedâ€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 circuitryâ€for example an output amplifierâ€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.
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 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.
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.
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 PCBâ„¢S: -
There are four major types of PCBâ„¢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.
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: â€œ 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: â€œ 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 :â€œThe 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.
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
C LANGUAGE CODE :-
void delay (unsigned int);
sbit ready = P3^5;
sbit buzzer = P3^6;
sbit LED = P3^7;
void main (void)
void delay (unsigned int time)
unsigned int i,j;
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 Ëœvote signalâ„¢ 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.
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.
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
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.
DATA SHEET OF TRANSISTOR BC 557:-