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Re: [TCML] Suggestions for a mini-TC?



A couple more questions...

Most large coils use exposed copper tube for the primary. There should be no problem using insulated wire for this, right? I'm also considering a design in which the high-voltage, high-current primary circuit is enclosed in a (ventilated) plexiglas box, with the primary coil mounted to the underside of the top of the box.

I've been looking at neon sign power supplies, and I see two basic types: big heavy clunky-looking boxes, and slim black plastic modules weighing a pound or two. Am I correct in believing the latter aren't actually transformers, but some sort of solid-state voltage multiplier arrangement, and therefore no good for TC use? (Going on the assumption that if they *were* good, everyone would be using them since they're tiny and cheap.)

How hard is it to go solid-state? I gotta admit I'm no expert on semiconductor circuits, ideally I'd like some widget that I plug into a circuit and it "acts like" a spark gap, but I'm sure I'd have to get more complicated than that. How much more?

Mixing quotes from several respondents:

Consider building a pair of coils configured as a Twin Tesla Coils. Each coil acts as a counterpoise to the other, and grounding of the bottoms of the connected secondaries can be a connection to your power line ground.

That looks like a fun arrangement: it'd also make the arcs more controlled, avoiding random strikes to the tabletop and nearby spectators. Two coils are safer than one, eh?

So basically all I'd need to do is wind either the secondaries or the primaries (but not both) in contrary directions in each coil, right?

I would consider using a 1.5 (7.5-9") or 2 (10 -12") form so that you can
get more turns on it with #30 and maintain the 5 or 6:1 aspect ration
suggested for small coils. Someone jump in here if I'm off, but usually we
like to see closer to 1000 turns to get the secondary inductance up.

I noticed that JavaTC was giving me a resonant frequency for this thing that was up in the MHz, and it makes sense that the frequency would go up as the coil and topload get small. Is there a fundamental problem with high-frequency coils?

A twin coil would help with this problem too, wouldn't it? The twin secondary circuit should have a resonant frequency half that of each coil alone.

I'm not sure a shoe box and in the
office is too good of idea for an "in the office toy"...for a ground plane
you could use a counterpoise which should fit a desktop.

It wouldn't *really* be turned on on my desktop, the odds that I'd nuke my computer are substantial. But something small enough to at least *display* on a desk would be nice.

Lastly, as you said, 1kv is hard to start an arc and a microwave oven
transformer is definitely a deadly toy if one gets bit(on the order of 2+kv,
~2kw) certainly enough to kill you.

Perhaps a 9kv 30ma old style neon transformer or an OBIT...anyone got one? I
like Steve's idea too.

MOTs and the big metal potted NSTs are physically waaay too big for this, and probably overpowered too.

I made a little coil with an approximately 1-1/2" diameter by 6" long secondary, wound with #36 wire as I recall. I did it just to see if I could get a decent winding and by luck I did. Works out to about 600 kHz resonant frequency with a 4" diameter toroid and puts out about 4 to 5 inch streamers when excited with a 2.8 kV, 20 ma transformer running about 50 watts input. Pictures of it somewhere in hotstreamer.

That sounds perfect. I looked for a link in hot-streamer.com but couldn't find it. Can you send me some details? I'm especially interested in the source for your power supply.

Here's a link to Gary's mini-coil page.

 _http://www.laushaus.com/tesla/minicoil.htm

That looks close to what I want to do, maybe a little too big. The power supply, an unpotted open core-and-coil neon sign transformer, looks like just what I'm after. Anybody know of a good source for these?
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