Hi Ken,
Glad to hear your back to coiling after your hiatus. You have such a
unique coil.
Terry Leonard
On 11/8/2013 11:04 AM, Ken Herrick wrote:
> Greetings-
>
> Single resonance still holds an appeal for me--in part since Tesla
> himself, with the benefit of solid-state technology, would surely have
> favored it. He didn't, after all, want sparks: he wanted to transmit
> power, not into wasteful sparks but out to the populace at large.
> Cockamamie idea, of course, and he and his investors lost a bundle,
> but he was still a genius.
>
> So here's what I'm working on--after some years' hiatus. To produce
> sparks, of course, not radiate power.
>
> Based upon my original notion, which worked but in hardware I made
> hopelessly complicated: 8, 1000 uF/450V capacitors arrayed together
> with 8 power MOSFETs in a ~12" diameter "ring" arrangement
> incorporating the equivalent of a 6-turn primary coil. The capacitors
> to be charged to full-wave-rectified and doubled mains voltage. This
> I've built and, driving it temporarily with 2 signal generators (to
> provide for pulse-bursts) and so far only at ~40 V charge, I find that
> it appears to work as simulated. The scheme is for the MOSFETs to
> connect 4 of the capacitors in series with the coil during each 1/2
> cycle, at the secondary's Fr. That yields, in simulation, ~240A p-p
> primary current at full capacitor voltage of ~300. I've devised also
> a simple constant-current capacitor-charge circuit so that I won't pop
> a circuit breaker trying to charge 8000 uF (plus another 2000 for the
> doubler) right off the mains from a cold start.
>
> The 12" x ~39" secondary coil I'll use is left over from my prior
> attempts, along with its 6 x 24" Landergren toroid. I have another,
> taller, coil as well.
>
> But in simulation I also found much that I wish I'd found out before:
> 1. All capacitors may be charged directly in parallel, with the
> inclusion only of a single 10 mH isolation inductor between the groups
> of 4. 2. All MOSFET sources may be (and are) tied together. 3.
> Each 4 drains may be (and are) tied together. And 4. All 8 MOSFETs
> may be (and are) driven from a single (D44H8/D45H8 H-bridge) source.
> I've built the H-bridge and it seems to do the job. Now I have to
> build the l.v. signal-processing part, which takes secondary-return
> current and amplifies and gates it to provide the MOSFET drive. I've
> so far simulated that successfully; it requires only 3-4 CMOS DIP ICs
> + the usual small parts--plus a l.v. power supply, of course, which I
> also have left-over.
>
> So circumstances allowing (I'm 85), I'll be making sparks again before
> too long. Since I won't use a breakout-point, the sparks very
> charmingly will dance all around the toroid (as they did before at
> 20/second or so), making lots of noise and ozone.
>
> Ken Herrick
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