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Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Whatever material you use to sound-deaden your spark gap, please make sure it's fireproof! You can combine blowers and soundproofing, by having the air flow through an acoustic silencer. The sound from a spark gap is mostly high frequencies, so it should be easy to deaden.
I'd also be interested to hear of your experiences in building simple HV supplies. I was wondering about the possibility of making a general-purpose regulated HVDC supply based around ignition coils driven in flyback mode by a TL494. They may not be as efficient as flybacks, and the lower frequency would make the output harder to smooth, but I think the toughness of oil-filled coils would make up for it. Plus I guess you can rectify it with a microwave oven diode, and easily change the polarity of the output by swivelling the diode through 180'. Just try that on a flyback with a built-in rectifier.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
I've found ignition coils to be pretty reliable (but I'm biased, I used to design electronic ignition for Lucas in the 70's) The main drawbacks are fairly high leakage inductance (about 10% for a typical 5mH coil) and audio noise as they need to be switched in the 1 to 4 kHz range for max power throughput (if a 12V battery/supply is used then the frequency needs to be in the 100's of Hz range) That's ok for a 'noob' supply since it gives a simple indication of operation and with a TC the noise is negligible. For a general purpose hv supply it can get a bit annoying after a while though.
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Spark Gap noise supression
You can combine blowers and soundproofing, by having the air flow through an acoustic silencer. The sound from a spark gap is mostly high frequencies, so it should be easy to deaden.