April 16. Passive RC/RL Circuit Natural Response

n this lab assignment, we examine the natural response of a simple RC circuit when we open and close the switch. 
Pre lab.
Following is the schematic of our RC circuit. We did calculated time constant since we were given R and C values. We estimated intital capacitor voltage and time constant for the circuit as shown below. R1=100. R2=47
. 
oscilloscope window showing the capacitor voltage response for the circuit shown in previous image where V+ is used as the voltage source. 

We use analog discovery to apply a 5V source ot the circuit. We get our oscilloscope graph as a linear part combined with a exponential part.

For part B

Part B prelab predictions. R1=978. R2=2150, C=22 uF

Part B measurements

in part B, we get maximum voltage of 3.4 V. Using the same method, we find experimental time constant to be 0.0172,which is about one fifth of the predicted value. the percentage difference would be 80%. 

Part B graph

We can see the shape of open switch and close the switch. 

signal input data

we apply a 2.5 V square wave, and with a offset of 2.5 V at a low frequency. This way, we do not need to plug and unplug the power supply ourselves.

ciucuit

after class DEMO.

Summery

As we can see, when we apply a square wave at a low frequency, it has a low percent difference. the results are not very good comparing to the expectation. That may due to the uncertainty of measure time from the graph and the inaccurate resistance since the inductor has some resistance which we are not considering in calculations. Overall, we learn the step response of circuit, calculate the time constant and visualize what happened when open and close switch.