Laboratory Exercise on Electrical and Digital Circuits, Lab Reports of Computer Science

Download Laboratory Exercise on Electrical and Digital Circuits and more Lab Reports Computer Science in PDF only on Docsity! -- 1 -- Basic Electrical and Digital Laboratory Concepts Computer Science 240 Laboratory 1 The laboratory begins by investigating the operation of the PB-503 Proto-Board, the circuit design tool we will be using to perform experiments during the first few labs. By making some simple connections and measurements, the student is introduced to the use of the proto-board for constructing and testing circuits. You will also be introduced to simulating circuits using LogicWorks®, a digital design application which we will continue to use using for the rest of the semester. Voltage, Current, and Resistance 22 KW +5V ground Figure 1. A simple circuit Exercise 1. Connect the circuit in Figure 1 on your breadboard. Use the +5V voltage supply on your breadboard, a resistor, and some wires. IF we were to remove the resistor from the circuit and replace it with a piece of wire, what would happen (don't actually do it!)? What if we removed it and did not replace it with any device? Calculate the current in the circuit using Ohm’s Law, with the measured voltage value, and the known resistance value (use the current units to label the current): If the resistor had a larger value (voltage source the same) , would there be more or less current in the circuit? -- 2 -- If the voltage source had a larger value (resistor the same), would there be more or less current in the circuit? Assume a resistor has the following bands of color: Green Orange Yellow Gold What is the value of this resistor? Transistors Basically, a transistor is a switch that can be turned on or off. Transistors are used to implement circuits that produce basic logic functions. Exercise 2. Get 3 2N3904 transistors from the drawer. Each transistor has 3 leads, marked E B C. Connect one of the transistors and a 1.8K resistor as shown below (use PB1 for the A input): Figure 2. Transistor logic gate, version 1 -- 5 -- Basic Gates and Boolean Logic From lecture, you have learned that any Boolean function can be represented using three operations: NOT, AND, and OR. A NOT gate can be implemented with 1 transistor, AND/OR with 3 transistors, and NAND/NOR with 2 transistors. Also, NAND and NOR are universal gates, and can implement any of the primitive operations NOT, AND, and OR. Exercise 3. Draw a circuit which implements the function F=AB+BC (use the basic symbols for AND and OR gates): Gates come on a chip, or integrated circuit (IC) in standard packages. Only one type of gate is available on a chip (for example, four 2-input AND gates are available on a single, 14-pin chip, IC 7408, and four 2-input OR gates are available on IC 7432). Each chip also has +5V and ground inputs, which must be connected to power the chip. Build the circuit on your protoboard, using 3 DIP switches for inputs A,B, and C, and an LED display for output F. DON’T FORGET to connect +5V and ground for each chip. Record the results for all the possible input combinations, and verify that your results are correct: A B C F 0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 -- 6 -- Now, draw a circuit which implements F using NAND gates only: To build this circuit, how many gates will you need? How many transistors? How many chips? Compare your answer to what would have been required for the original circuit, using AND and OR gates. Describe the advantages and disadvantages of using a universal gate in a circuit design: LogicWorks Exercise 4: You can simulate circuits using the LogicWorks circuit design software installed on your workbench PC. Go to the PC and launch LogicWorks (from the Start menu, you can find it in the All Programs pop-up menu). When the application opens you will see Drawing and Simulation Toolbars at the top (as labeled below), a large Design Window below the toolbars, a Parts Palette on the right, and a Timing Window on the bottom: -- 7 -- There will not yet be a circuit in the Design Window – you will see a pop-up window asking you whether you want to create a new empty circuit. Begin by clicking on the Create button. Follow the steps below to simulate the circuit F = AB + BC: o Go to the Parts Palette, and select the Simulation Gates.clf library. o Find the AND-2 gate, and double click on it. o Move to the Design Window and place the gate somewhere in the window by clicking. Place a second gate by clicking again. Press the space bar to deselect. -- 10 -- Binary Arithmetic Exercise 6. Connect IC 7483 as shown below. Use the 8 DIP switches on the Proto Board as inputs to A4 – A1 and B4 – B1 (NOTE: A4 and B4 are the leftmost, or most significant bit, of each number) Figure 5. Circuit using IC 7483 Using the DIP switches, set A4 – A1 to the following value: 0001 Set B4 – B1 to the following value: 0001 Record the result for S4 – S1: Can you tell what function the 7483 is performing? What is the value of C (carry-out)? Is it correct for this calculation? Now, change A4 – A1 to: 1010. Change B4 – B1 to: 1111. -- 11 -- Record the result for S4 – S1: Assume two’s complement representation is being used. Is there a carry-out for this addition? How about an overflow? Is the result correct? Why or why not? Next, change A4 – A1 to: 0111. Change B4 – B1 to: 0111. Record the result for S4 – S1: Is the result correct? Why or why not? Experiment with entering different values at the inputs A4 – A1 and B4 – B1. Verify that the circuit gives you the correct result. List at least 3 sets of test values and results which you tried: