Joule Ringer!

[Pirate88179]

Great to see you Xee2, it has been a while.  Surely there is some work around for this as you have described it?  What about a larger farad cap in parallel?  If we got the specs right, could we not take advantage of that where it dumps into the second cap and that keeps the current flowing but then helps recharge the primary cap?

Bill

[hartiberlin]

I do not think you are interpreting the waveforms correctly. What they are showing is the voltage developed across the internal resistance of the capacitor due to current flow. You can consider this to be a small resistor in series with the capacitor. When current is flowing out of the capacitor the voltage developed across the resistor subtracts from the static voltage of the capacitor. When current is flowing into the capacitor the voltage adds to the static voltage of the capacitor. The area under the curves is the energy leaving the capacitor and the energy returning to the capacitor. The interesting thing that the waveforms show is that the energy going back into the capacitor is almost the same as the energy coming out of the capacitor during each cycle. Thus the net loss of capacitor energy is very small in spite of the currents flowing out of it (since most of the energy is returned).

If you try to put a switch on the capacitor, the voltage will disappear as soon as the switch is opened since there would no longer be any current to generate the voltage.

Hi Xee2,
normally the cap has a resistor parallel to his plates in the compensation circuit diagramm.
What you are referring to would be an additional inductance or okay, an additional series
resistor.
Okay, could be that these spikes show voltagedrops at these internal series resistor or
inductances.

But that is why I asked for the dual channel scope shot of showing also the current
on the shunt.
Only this will tell us, what current is really flowing into or out of the cap and
thus we will know, if the cap gets really recharged in some spikes.

Looking forward to see such scopeshots.

Many thanks.

Regards, Stefan.

[hartiberlin]

Here is the internal compensation circuit diagramm
of an electrolytic capacitor:

http://upload.wikimedia.org/wikipedia/commons/5/58/Electrolytic_capacitor_model.svg

We really need to see the current on the shunt in the circuit to
say more.

Regards, Stefan.

[conradelektro]

Two channel scope shots as suggested by Stephan

The attached photos should tell it all (look at the circuit, third picture). I went back to the circuit with the resistor-capacitor combination instead of the bifilar coil and the blue cold cathode lamp. The frequency is about 300 Hz, varying between 280 and 340 Hz. Frequency goes slowly down when the power supply is disconnected and the circuit winds down on the 4700 uF cap.

The scope shot with 2 usec is without power supply, the circuit runs on the 4700 uF cap.

The bifilar coil does not change much, power consumption is slightly higher (2 mA instead of around 1 mA) and the frequency is a bit higher up to 500 Hz.

Greetings, Conrad

[hartiberlin]

Many great thanks Conrad.
Please give me a few minutes to analyse them !
Regards, Stefan.