Mini Projects for ECE

Electronic Voting Machine

Introduction: WHY EVM'S INSTEAD OF PAPER BALLOTS?

Voting is the keystone of a representative democracy. The people have the power to choose who will lead the government by going to the ballot box. It is a civic responsibility to vote, whether it's casting a ballot for senators, the governor, our Washington delegate or a referendum. And yet Guam, like the rest of the nation, has seen a steady decline in voter turnout. To help reverse this trend, voting needs to be as easy and convenient as possible. This will better assure that more people will take an active role in choosing our government officials and thus better ensure those officials are truly representative of the community and will act in our best interests. Senators discussed two measures regarding voting in local elections: one would bring back the use of electronic voting machines; the other would eliminate early in-office voting except for those who fill out an affidavit with a reason they are casting an absentee ballot.

Description: Electronic voting machine has now days become an effective tool for voting. It ensures flawless voting and thus has become more widespread. It ensures people about their vote being secured. It avoids any kind of malpractice and invalid votes. Also such kind of system becomes more economical as consequent expenditure incurred on manpower is saved. It is also convenient on the part of voter, as he has to just press one key whichever belongs to his candidates.

Block Diagram: 

Description in detail: The “Electronic Voting Machine“basically consists of four main blocks; these are keypad, micro controller, display and control switches 

1) Keypad: Keypad is basically a 4 X 4 matrix keypad. Thus it has one key specified for one candidate. This block is used in both voting and counting mode, in voting mode key of respective candidate is pressed, the corresponding signal is sensed by micro controller. In counting mode this keypad is used to check the votes of respective candidate. The key given for candidate is pressed and micro controller senses the corresponding signal. 

2) Micro controller: Micro controller senses the signal given from switches and decides the mode of operation in voting mode it increments the data for corresponding key i.e. respective candidate as well as it sends signal to display block to indicate one key is pressed. In counting mode micro controllers fetches data from memory location and send it to display devices. 

3) LCD: Liquid Crystal Display which is commonly known as LCD is an Alphanumeric Display it means that it can display Alphabets, Numbers as well as special symbols thus LCD is a user friendly Display device which can be used for displaying various messages unlike seven segment display which can display only numbers and some of the alphabets. The only disadvantage of LCD over seven segment is that seven segment is robust display and be visualized from a longer distance as compared to LCD. Here I have used 16 x 2 Alphanumeric Display which means on this display I can display two lines with maximum of 16 characters in one line. 

4) Control switches: There are three control switches: I. Clear Votes. II. Controller switch. III. Total Votes

Circuit Diagram:

Operation or Working of Project: 

1] Power on: When supply is turned on RED LED glows. 

2] Mode selection: i. Voting mode: toggle switch on VCC ii. Counting mode: toggle switch on GND. 

Voting Mode: When toggle switch is in voting mode “Voting mode” is displayed followed by “Please vote”. After a vote being given, “Please wait for authority switch” is displayed and again enable for voting after Control switch being pressed by the voting Authority. 

Counting Mode: When toggle switch is in counting mode “Counting mode” in displayed on the screen, and total number of votes to respective candidate can be displayed on the screen by pressing the respective key assigned to them. 

3] Clear mode: Press clear switch when all entries are required to be erased. Clear switch should be pressed before voting procedure. 

4] Buzzer indication: Pressing of key in voting mode is indicated by a buzzer sound. 

5] Controller switch: This switch is provided for enabling the keypad in voting mode. This switch is under the control of voting authority.

Advantages: 
1. It is economical 
2. Less manpower required 
3. Time conscious, as less time required for voting & counting 
4. Avoids invalid voting 
5. Saves transportation cost due to its compact size 
6. Convenient on the part of voter 

Application: This could be used for voting purpose at any required place.

BIPOLAR TRANSISTOR TESTER

         

         This tester is primarily meant to test bipolar transistors. It can indicate the type of the transistor as well as identify its base, collector and emitter pins. The circuit is very simple. The direction of current flow from the terminals of the transistor under test (TUT) is indicated by a pair of LEDs (green-red). An npn transistor produces a red-green-red glow, while a pnp transistor produces a green-red-green glow, depending on the test point that connects to the terminal of the transistor. 

Emitter and collector are differentiated by pressing pushbutton switch S1 that actually increases the supply voltage of the circuit by about 5.1V.

         At the heart of the circuit is ICCD4069 (IC3), which oscillates and produces pulses required to test a pair of transistor leads for conduction in both the directions. Different combinations are selected by an arrangement of counter CD4040 (IC1) and bilateral switch CD4016 (IC2).

         Fig. 1 shows the circuit of the bipolar transistor tester. A pair of LEDs is connected to each test point through which current flows in both the directions. Each LED corresponds to a particular direction. In this manner, both junctions of the transistor can be tested. The LEDs are arranged to indicate the type of the semiconductor across the p-n junction. The counter is clocked by the AC generator built around gates N5 and N6. This makes the LEDs glow continuously for easy observation, revealing the direction of current flow between different test points. So if the red LED connected to certain point glows, it means that n-type of the junction is connected to that test point, and vice versa. Thus a red-green-red glow indicates npn type of the transistor, while a green-red-green glow indicates a pnp transistor. From this observation, you can easily detect the base. Collector and emitter are differentiated based on the principle that the base-emitter junction breaks down under reverse bias much more easily than the base-collector junction. Thus under increased AC voltage, you can easily see that the emitter conducts more in the reverse direction (associated LED glows significantly) than the collector. Use of transparent or semi-transparent LEDs is recommended.

        Adjust preset VR1 (2-megaohm) to get equal glow when any two test points are shorted. Unregulated 15V-18V is regulated by the zener-transistor combination to power the circuit.

        The testing procedure is simple. Normally, the transistors can be plugged in any orientation as they come in a variety of possible arrangements of base, collector and emitter pins, such as CEB, BEC and CBE. Simply plug the TUT in the possible combinations of three points. A red-green-red glow means that it is npn transistor and the pin associated with green LED is base. To identify the emitter and collector, simply press switch S1 and observe green LEDs adjacent to already glowing red LEDs. The green LED glowing with a high intensity indicates the emitter side, while the low-intensity LED indicates the collector side.

Fig. 1: Circuit of bipolar transistor tester

Fig. 2: Author’s prototype of bipolar transistor tester

Similarly, a green-red-green glow means that the transistor is pnp type and the pin associated with the red LED is the base. To identify the emitter and collector, simply press switch S1 and observe red LEDs associated with the already glowing green LEDs on the sides. The LED glowing with a high intensity indicates the emitter side, while the low intensity

LED indicates the collector side. Assemble the circuit on a general purpose PCB and enclose in a small box. Keep the preset knob in the middle. In order to make it easy to plug the TUT, you can increase the number of test points as shown in the author’s prototype in Fig. 2.