LTspice simple RLC circuit

Thread Starter

fornaxxx

Joined Nov 21, 2015
3
Hi, I'm trying to simulate my first RLC circuit. Source, capacitor, resistance and inductor in that order. However, when I put them in this order in lt spice, the response is nothing like a sine wave slowly decaying. This is represented in the first image im uploading called RLC circuit problem.

Whats next is weird. By desperately trying to make this work, I interchanged the components of my circuit and managed to get a sine response, but then that is not exactly the circuit I have and i need the voltage across the inductor. This is represented in the second image im uploading called RLC circuit problem2.

Im just trying to get the sine wave response across the inductor in the first circuit. Is that too much to ask from LTspice?

Thanks
 

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crutschow

Joined Mar 14, 2008
25,269
LTspice is working fine. The error is in the cockpit. ;)
Your first circuit is over-damped so it will not oscillate.
Reduce the value of R1 to an ohm or less.

The reason the second circuit works is because the inductor is .02H not .02mH which reduces the damping factor.

Also check Skip initial operating point solution (uic) in the Simulation Command window so it does not solve for a DC solution at the start of the simulation.
 

Thread Starter

fornaxxx

Joined Nov 21, 2015
3
LTspice is working fine. The error is in the cockpit. ;)
Your first circuit is over-damped so it will not oscillate.
Reduce the value of R1 to an ohm or less.

The reason the second circuit works is because the inductor is .02H not .02mH which reduces the damping factor.

Also check Skip initial operating point solution (uic) in the Simulation Command window so it does not solve for a DC solution at the start of the simulation.
Thank you, I have to use the third and fifth bumps to generate a pulse in a comparator, and and other stuff, but i could continue without the exact values of those bumps. Is there a way to calculate by hand the max voltage of those bumps in the decomposing sine wave?
 

crutschow

Joined Mar 14, 2008
25,269
Thank you, I have to use the third and fifth bumps to generate a pulse in a comparator, and and other stuff, but i could continue without the exact values of those bumps. Is there a way to calculate by hand the max voltage of those bumps in the decomposing sine wave?
Here is some mathematical info on a damped sinewave.
I just let the computer do the calculations in an LTspice simulation and use the values from that.
 
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