# Pspice Underdamped RLC circuit

#### khvmaths

Joined Mar 23, 2017
14

The circuit below is drawn and the simulation is as above. The signal is supposed to be 10 V pp, 500Hz (square wave)

It is supposed to be something like this:

#### Motanache

Joined Mar 2, 2015
481
I did not simulate, but,
Increases signal ON/OFF time and reduces L1 inductance.

You wait for that damped oscillation.

#### khvmaths

Joined Mar 23, 2017
14
Yeah, but this is from our experiment sheet, the damping factor is 0.0001

#### crutschow

Joined Mar 14, 2008
25,645
I simulated the circuit and got the same waveform as you show.
The circuit is only slightly damped.
Are you sure those component values are correct?

To see a waveform more like you expected change L to 1 mH.

#### MrAl

Joined Jun 17, 2014
7,849
View attachment 127186

The circuit below is drawn and the simulation is as above. The signal is supposed to be 10 V pp, 500Hz (square wave)

View attachment 127187

It is supposed to be something like this:

Hello there,

The waveform shown does not look like the wave that should result from that network with those values.
Something is not being presented correctly.

#### MrAl

Joined Jun 17, 2014
7,849
Hello there,

The waveform shown does not look like the wave that should result from that network with those values.
Something is not being presented correctly.

Hi again,

Big mistake on all our parts. When in question, go back and read the directions

In this case, i think we all read the x axis as simply "t" instead of what it really is which is "w0*t".
If we do it the right way, we get a waveform that is like the one pictured although it does not damp as fast.

To simulate this you could either try to set the time axis to w*t or you could solve for w0 and change the exponential time 't' to 't/w' and then that would give the form:
A*e^(-a*t/w0)*sin(t)

but now 't' is really "t*w0". This is of course after solving for the time domain response of the circuit voltage in question. In any case though i think you have to solve for w0.

Try it again and see what you get.

Last edited:

#### crutschow

Joined Mar 14, 2008
25,645
Very interesting.
But it still seems like a problem with odd circuit parameter values to give newbies.

#### MrAl

Joined Jun 17, 2014
7,849
Very interesting.
But it still seems like a problem with odd circuit parameter values to give newbies.

Hi,

Yes, but sometimes unusual parameters are given to illustrate certain points of interest. Usually to eliminate a variable to make the equation or graph more general, or to illustrate a property that never varies with a given parameter. For this example it could be to try to eliminate w0 so that the waveform appears the same for any w0 we choose. I'd have to look at it in more detail to be sure, but that's the main idea sometimes. It could also be a mistake

What always bothers me is we almost never know what the OP background education is like unless they post really stupid questions or they post a lot so we get some idea. Never know exactly how to respond so it's a little bit like a guessing game unfortunately. This of course means i have to wonder what the OP;s background education is like here and just post something that seems appropriate.