Circuit help SOLVED

So this is my circuit, but it's not working as I believe it should. It's supposed to charge up the two caps which are in parallel, and then discharge through the resistor. While the 'out' value records the voltages.

Could anybody tell me what is wrong please?

by HarryTorry
March 18, 2012

You've got it close again, but now you've placed your measurement point "out" on the ground node, so you read zero volts. Since you want to read the V across the capacitor, place ground at one end, your measurement point on the other.

Also, you have a 7 minute time constant here. Although the unit "mF" was, in ancient times, used for microFarad, in modern metric notation microfarads are uF and a mF ia a milliFarad, a really huge value. (Very old schematics might also use mmF for micromicroFarads, now called picoFarads, pF, (10^-12 F).

by CarlSawtell
March 18, 2012

Here's one I made that's similar but discharges and charges through a resistor:

It's not a very elegant looking circuit and I'm sure there's a better solution than all the switches, but you can watch the voltage and current change in both directions on a 10s time constant.

by joelmathewson
March 18, 2012

Hi Harry,

Looks like you've edited the circuit since you asked the question and not kept a copy of the original. The circuit you have at the time of this posting works. Carl's comment about the very long time constant still holds but the circuit does show the voltages as you'd expect. You just need to extend the simulation time or reduce the capacitor values.

The way you have connected the switch and the DC supply, the caps start life charged up to -16V and then discharge to 0V when you open the switch. Is that what you intended?

by signality
March 19, 2012

Post a Reply

Please sign in or create an account to comment.