ECE 35 Lab 4

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Jan 9, 2024

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ECE 35 Lab 4 Name 1 Huizhuo gan Name 2 Linh Nguyen In this lab you will investigate the RC and RL circuits. You will run simulations and experiments to test your hypotheses and draw conclusions based on your observations. Part A: Introduction to function generator and oscilloscope Below are a few short videos meant to help you familiarize yourself with oscilloscopes and function generators. These instruments are incredibly useful, so it is good to be familiar with how to control and adjust them. You will need this in your future classes. Watch the videos below. Watch them before starting the lab. 1) Oscilloscope tutorial: https://www.youtube.com/watch?v=lSHAE_Y6snc 2) Function generator tutorial: https://www.youtube.com/watch?v=mLKPwWGBtIw 1) Turn on both the oscilloscope and the function generator. After they boot up and are ready, connect the function generator cable directly to Channel 1 of the oscilloscope. 2) If Channel 2 is not off, turn it off by pushing Channel 2 Menu twice. In order to turn on Channel 2, push the Channel 2 Menu button once. In order to open the measurements menu, push the Measure button. You can change what measurements are displayed by pushing the button to the right of the screen corresponding with the field you want to change. 3) Set up the function generator to generate the following waveform: a sine wave with amplitude of 2.5V (Amplitude is not the same as peak-to-peak!), a frequency of 60 kHz, and no DC offset. 4) Make the following adjustments to the oscilloscope: a) Set volts/div to 2.00 V b) Set sec/div to 5.00 μsec c) Center graph on 2.00 V

Build the circuit below on your breadboard and attach the function generator as Vin. Then turn on the function generator. Generate a sine wave with a peak-to-peak of 5V, use a frequency of 200 Hz, and no DC offset. Adjust the oscilloscope so that the waveform is clearly visible. wdc44Measure Vin on Channel 1 and Vout on Channel 2 of the oscilloscope. For the input waveform on Channel 1 and the output waveform on Channel 2, use the cursor function on the oscilloscope to perform the following tasks. a) Measure the minimum voltage of the input and output waveform. The minimum voltage of the input waveform was 1 voltage and the minimum voltage of the output waveform was 49 mV. b) Measure the maximum voltage of the input and output waveform. The maximum voltage of the input waveform was 3V and the minimum voltage of the output waveform was 51V. c) Measure the peak to peak voltage of both waveforms. The peak to peak voltage of both waveforms was 1V. d) Measure the period of both waveforms. The period is 5ms.

Show your results to a TA before continuing to the next part. Part B: RC and RL circuits Do not build this circuit before reading the following: In this experiment, you will measure the value of the unknown capacitor in the following RC circuit using its step response. Find the equation of the output voltage as a function of time assuming the switch closes at t = 0. A single step response can be hard to measure, you can circumvent this problem by periodically repeating the event (i.e., in this case, by periodically opening and closing the switch). A function generator can be used to simulate a switch opening and closing. What kind of waveform and at what frequency range do you suggest setting up the function generator to run this experiment? (hint: frequency should be set so that you can observe the whole waveform include the transient and beginning of the steady state behavior of the capacitor) Sine waveform Frequency:1000 Hz

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Think of a way to measure the capacitance of an unknown capacitor C1 using the circuit above and then explain it to your TA. Build the circuit, perform your experiment and write your measured value of C1 here. Record a clear picture of the rising edge transition on the oscilloscope and place it here. Repeat the same experiment with a 1M ohm resistor instead of the capacitor. Write your observations below. Does it match with our theoretical analysis using ideal resistors? Now scale the time so that you zoom into the rising and falling edge of the waveform. Can you explain what is happening?

Using the same waveform for the voltage source as above, build the circuit with an inductor as shown below. A TA will give it to you. Do NOT throw the inductor away when you are finished with it, give it back to a TA . Measure the time constant and the value of the unknown inductor in this RL circuit. Remember that we are measuring the voltage across the inductor, so make sure that the waveform that you measure on the oscilloscope is what you expect to see for an inductor. Write your results here:

Show your results to a TA before continuing to the next part. Part C: RC circuit time constant Do not build this circuit before reading the following: In the circuit below, you will use a square wave signal with the frequency of 100Hz and amplitude of 2V as the voltage source. How would the shape of the output voltage change, if you change the 1K resistor to a 10K resistor? Is the effect the same if you change the 10nF capacitor to a 100nF capacitor? What is the effect when changing the capacitor from 10nF to 100nF and the 1K resistor to a 10K resistor? Compare the magnitude of the output voltage at t = for each case. 4τ Write a summary of the your expectations here:

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Build the circuit and test your hypothesis. Write your results in the space below. Show your results to a TA before continuing to the next part.

Part D: Steady state RC circuit Do not simulate or build this circuit before reading the following. In the RC circuit below, the switch is opened at t=0. Is V out greater at t=0 - (assuming it has reached steady state) or when the circuit has reached the steady state after the switch is opened? Write your answer and explanation here: Calculate by hand the steady state voltage V out for t = 0 - and for t > 0. Write your answers below.

Draw two schematics of the circuit in PSpice, one with the switch open and one with the switch closed, and run the simulation to see the steady state value of output voltage for the two cases. Summarize your observations below and compare them with your previous calculations. Show your results to a TA. Don’t forget to submit the lab and sign out.

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