Hey,

I want to build a device that charges a capacitor to full and then will discharge when a switch is held. I want it to detect when it discharges and make it so it will not discharge again till it is storing max energy and then repeat that cycle for as long as a switch is held. I am curious about a couple solutions...I think the easy way would be to use a PICAXE but is there another way to do this with just circuitry?

Thanks for any help!

 

My first thought is: why? My second thought is: what do you mean by "full"?

It's not a battery.

If by "full" you mean up to the supply voltage - well, of course, it never actually gets there. It charges asymptotically. But it will be getting fairly close after about 5CR.

And the same principal is true when it discharges. See:-
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capchg.html#c1

I think you could do what you want with 2 comparators and a bistable. Very similar to the internal workings of a 555. But with the charge and discharge thresholds set to say 95% and 5% of the supply voltage. Or possibly by detecting the charging and discharging currents through a resistor - when it falls to a sufficiently low value consider it "there".

 

You could use an op amp oscillator circuit, but it will only just get to full supply as there will be voltage drop across the charge resistor.

Or if you use a 555 timer circuit the capacitor will only charge to 1/3 and 2/3 of the supply.

http://www.google.co.uk/imgres?imgu...QNoeG0AX2lIHICA&sqi=2&ved=0CDUQ9QEwBQ&dur=476

 

It is for an experiment, I have a mouse problem in my shed and I want to put a strip on the ground near where I think they are getting in and zap them with a non-lethal dose of electricity. I don't want it to kill them so that is the reason for the interval but I am hoping it will cause them to turn 180 and go back where they came from...the alternative is using traps and killing them.

I am not sure how to do it with a 555...I think that would be the easier way because I could just size up the capacitor and/or batteries to make up for the 2/3 charge.