Wednesday, April 13, 2011

How it's done volume 5: Charging that cap

Of course, you'll have to charge those shiny bad-ass capacitors. This is pretty easy if you're going to be plugging it into the wall: Buy an old microwave and strip out the transformer. Those guys can give like a thousand volts last I checked.

But what if you're using a DC battery? I've personally found that all the DC-DC products out on the market are pretty much shit. So I chose to build my own. There are a lot of DC-DC transformer designs out there on the market. They also seemed pretty shitty. So I designed my own. It's a pump charger that runs at variable frequency. I've seen this kind of charger setup to run at constant frequency but I found that to be pretty inefficient.

Essentially this circuit pulls current through the inductor to ground till it senses that it's got a certain amount, then it kills the connection to ground and lets the inductor force the current through the capacitor. It makes a lot of EM noise but it can also get a 12V source up to 1000V without a lot of hassle. I did a test of pumping it out of one capacitor and into another maybe 2 years ago and remember getting a number like 80% efficient or so. If anyone can find a place to buy such equipment let me know. Otherwise, this is definitely an area that I feel the market is letting us down.

Of course, the schematic I have is a vague recollection. I'd have to go back and actually map it... or dig the exact design out of my file drawer. It also doesn't show a current limiting circuit which you'll also want. At this point, I leave both of those to the reader. If you can figure out how to finish the circuit, you're allowed to use it for your projects :) And if you find a way to sell it, I want a cut!

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