Once upon a time, sparkfun sold this device:
It took 5V 3A DC in, and out the other end came a loud, bright series of sp arks at maybe 30-50Hz. The spark gap could be up to a half inch wide, so I' m guessing it generated something near 30,000v at peak. The effect was an i mpressively "fat" spark that looked more or less continuous but wasn't, and buzzed loudly.
They stopped selling them because they tended to fry themselves after very little use. Unfortunately, that happened after I'd designed a device that u ses them, so now I'm searching for a replacement, and having no luck. Part of the problem is the replacement device has to be about the same size and shape as the original, so anything involving a car ignition coil is off the table.
I tied to open one of the original devices up. It was fully potted and I do n't have appropriate tools, so I ended up shredding it without learning muc h, but:
The output is from a transformer, made of two squarish coils joined by an i ron U core. No way to tell what the ratio is; I damaged the coils. Both sid es seemed to have a fair amount of wound copper, which surprises me because I'd have expected a huge ratio.
Driving the transformer is two capacitors, possibly in serial. Unclear exac tly how they connected to the transformer. Driving the capacitors... I hav e no idea what it was, given how badly I shredded it. Possibly 1 or 2 didoe s or resistors and some sort of small blue blob which I assume was some kin d of oscillator, but for all I can prove it's where the voltage step-up hap pens and the transformer is just for isolation. I think that's the full set of components. The caps contained some kind of foil and didn't look electr olytic. They were longish, fattish rectangles, not disc or can shaped.
When one unit failed, one of the two caps more or less exploded, deforming the case, if that's a clue to the design. The unit would self destruct rapi dly if asked to drive a gap of over 1/2", but they tended to die sooner or later anyway.
I realise this is not enough to go on, but I'm hoping someone can derive wh at the circuit was likely to be. I will experiment from there. I want a fin al circuit that is stable and long lasting.
YES, I know a half inch of spark represents a dangerous amount of energy. I 'll take due care in my experimentation.
Thanks in advance.