I'm building a coil-gun in my high school engineering class and am having a little trouble charging the 5 250-volt, 1000 microfarad capacitors. Would it be possible to connect the wall to a voltage doubler, and then just hook that up to the capacitors(obviously with a fuse along the way for safety)? I'll only be using the circuit under careful supervision, so reasonable danger is OK.
Electrical – Charging 250 volt capacitors without flash camera circuit
capacitorcapacitor charging
Best Answer
What voltage do you have at the outlet? If is 110-120V, the peak voltage which the capacitors will take will be approx 150-160V which is too less. If outlet is 230V, the voltage will be 325V which is too much. If you want 250V dc, the transformer you'll need is to be one who deliver in secondary 250V / sqrt(2) = 175V ac (which will not be easy to find).
A "dirty" approach will be to just use from 230V (outlet or transformer) a simple diode as a rectifier (yeah, is just as simple) series with a large resistor (something alike 22-33 kiloohmi/1W) and you'll observe carefully the capacitors voltage with a multimeter and stop charging when its reaching 240-250V. It shall take about two minutes to charge to that voltage (will approach time constant T=RC, thats 5000uF x 22k = 110 seconds if i don't miss). Edit: i missed, its very late now in Romania; rectification is single way, time will be more than double, also considering the voltage should arrive close to top of the RC courve; use a 5-10 kilo resistor, at 5W.