Hi,

Can someone point me in the right direction.

I need a circuit to toggle the polarity of a battery across a capacitor.

The positive switch open, negative switch closed.

The negative switch open, positive switch closed.

One is open when the other is closed.

Any help much appreciated.

Thanks

 

DPDT? double pole double throw switch?
Max.

 

I need a circuit to toggle the polarity of a battery across a capacitor.

How quickly do you need to do this? 1Hz, 1MHz ? How big a capacitor?

It would help to know why you want to do this.

 

Hi Max and Wayneh,

I need the circuit to flip flop back and forth with out manual switch.

The frequency to be 20khz min.

Capacitor is 200 pf +/-.

I am experimenting with some alt. energy.

Thanks

 

Do you truly need reverse polarity, or just charge and discharge? The latter could be done with a simple 555 timer IC. The former is a bit trickier but not bad.

 

Hi Wayneh,

It is not charge - discharge.

Let me put it this way. I need to expose the positive terminal of the capacitor to the positive terminal of the battery-closed switch, while not exposing the negative terminal of the capacitor to the negative terminal of the battery-open switch. Then flop it the other way negative exposed to negative, while positive not exposed. There is not a reversal. The terminals are never connected at the same time. Does that help?

Thanks

 

You're losing me. What is the "unconnected" end of the capacitor connected to? Changing the potential of one side of a capacitor won't change its store of energy unless the circuit is completed somehow.

But I suppose you could accomplish this with the 555 output directed to 2 diodes, one forward and one reverse biased. The low side of the capacitor would see a path to ground when the timer output goes to ground, and the high side would see the 555 output voltage (less the diode drop) when the timer goes high. The capacitor would quickly achieve a steady state charge, though, so again I don't see the point.

 

Thanks Wayneh. I will check it out.

Thanks Again

 

I can't put my finger on it but this smells like another perpetual motion project. I hope you're not wasting (y)our time on such a thing.