Download Lab Exercise on Thevenin and Norton Equivalent Circuits in Pre-Engineering 2250 - Prof. Je and more Lab Reports Engineering in PDF only on Docsity! Laboratory 4 Pre Engineering 2250 DC Thevenin and Norton Equivalent Circuits Purpose: To demonstrate equivalent circuits using computer simulations and actual circuits. Students should gain additional experience using computer simulations tools. Equipment and Components: • Prototyping board • Multimeter • Power supply • Resistors: 5.1 kΩ, 13 kΩ, 20 kΩ, 24 kΩ, 43 kΩ, 56 kΩ, 120 kΩ, and others depending upon your design Preliminary: Using the circuit shown in Figure 4.1, prepare the following 1. Calculate the Thevenin and Norton equivalent circuit by: a. Find the open circuit voltage (Voc) using node analysis. b. Find the short circuit current (Isc) using mesh analysis. c. Calculate the source resistance using Voc and Isc. 2. Use PSpice to determine the Thevenin and Norton equivalent circuits using the two different methods described below. Include output from your PSpice program in you lab book. a. Using PSpice, find the open circuit voltage (Voc) and short circuit current (Isc). From those two values, calculate the source resistant (Rs = Voc/Isc). However PSpice does not know how to handle loose nodes so you must insert effective resistors to model an open and a short. 1. The open circuit voltage can be determined approximately by adding a resistor between points A and B (called Rload) and setting Rload= 1.0x1012Ω or 1E+12 in Spice format (the approximate resistance of air) and examining the voltage across the load. 2. The short circuit current can be determined approximately by setting Rload=1.0x10-12Ω or 1E-12 in Spice format and examining the current through the load. Warning: When dealing with the extreme values keep in mind that the resulting matrixes may be ill-conditioned. Verify that the final answers do not violate KCL / KVL rules. If this is a problem try relocating the ground. b. Suppress the power supply (replace it with a short – 0V) and apply a test voltage source to the output. Using a 1 V source determine the current flowing into the circuit. The source resistance can be found by Rs = Vtest / Iforced. The Thevenin Voltage or Norton Current source are then found using the methods in part a. 3. Design a simple parallel and/or series network of two or three 10% resistors (of standard values) that produces an equivalent resistance to the source resistance calculated in part 1.c. Hint: They do not produce a 8.6 kΩ resistor but two 4.3 kΩ resistors could be connected in series to yield an equivalent 8.6 kΩ resistor. Procedure: 1. Create the circuit shown in Figure 4.1 on a prototyping board. 2. Measure the open circuit voltage (Voc) using a voltmeter and calculate the Thenvenin equivalent voltage source. 3. Measure and calculate the equivalent source resistance using the following three methods. a. Measure the short circuit current (Isc) using an ammeter and calculate Rs from the open circuit voltages measured in part 2. Warning: In practice it is a bad idea to short the output terminals of any random circuit. Before shorting any terminals, users must verify that the internal circuitry of the system can dissipate the resulting power. There is no need to do these calculations with the circuit provided in this lab. b. Suppress the voltage source in the circuit (replace it with a short circuit) and measure the input resistance (between terminals A and B) directly with an ohmmeter. Remember: When using a multimeter to measure resistances, all other source must be removed or the resulting values will be erroneous. This can complicate any circuit that requires a bias voltage, like transistors and op-amps.
