Day 14

Passive RC Circuit Natural Response

So what happens when you disconnect or connect a RC circuit to a voltage source? We observe the behavior of an RC circuit by building a simple RC circuit where we can easily connect and disconnect the voltage source. This process is so quick that the human reaction time will effect the results of the lab so we are introduced to "Triggering". In Analog Discovery we can set the oscilloscope to capture the plot of the discharge and charging of the circuit by setting a trigger event.

Here is the simple circuit design we are using for this experiment that we have set up on our breadboards. The top circuit is when a voltage source is applied to the RC circuit. The bottom circuit is when the voltage source is removed from the RC circuit (denoted at t=0).

This is the built circuit from the above diagram because we all like sexy circuit pics. We needed to use 3 capacitors in parallel (summing them up) so we can get an equivalent capacitance of 22uF.

Our oscilloscope reading as we discharged the capacitor by disconnecting the voltage source. This is plotted over one time constant tau.

This is the graph of voltage vs. time as we discharged the RC circuit.

Here we can see that our time constant (tau) is 0.020s. We had a theroretical value for tau at 0.015s. This shows an error percentage of 33.3%. This is probably due to experimental errors as we had a flying monkey throwing ninja stars at us while we were doing the experiment. For future experiments we need trained monkey body guards.