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Voltage needed for small tesla coil

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Sedgewick17

Mon May 21 2007, 11:14PM

Registered Member #796 Joined: Mon May 21 2007, 10:53PM
Location:
Posts: 2

I am trying to build a Tesla coil that is around 1ft tall,and about 6in. wide.I don't want to use 10,000 volts because I think it would be to dangerous,but at what voltage will a Tesla coil stop working?

Sulaiman

Tue May 22 2007, 12:03AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

A spark gap Tesla coil needs at least 330V at normal atmosphere.
Unfortunately this requires an impractically small spark gap and has near zero efficiency.
So many kV are required to make a practical (STP atmosphere) spark gap Tesla coil.

If you substitute a gas discharge tube or semiconductor device such as a sidac then operation at around 120V is possible but inefficient.

You can drive a Tesla coil with any small voltage (at the resonant frequency) and it will produce a larger output voltage than the input voltage.

Assuming that you mean 'Voltage needed for arcs/sparks'
IN MY OPINION
Voltage isn't dangerous, it's current through the heart that's dangerous.
If you have a high voltage source that can only supply a small current (a few tens of milliamperes) then you can get a non-lethal electric shock.
Even up to 10 Joules at any voltage is supposed to be non-lethal (but incredibly painful) so the energy stored in a small TC primary capacitor is non-lethal (theoretically)
I don't think anyone has died of electrocution from a TC powered by a Neon Sign Transformer (NST) or an Oil Burner Ignition Transformer (OBIT), but they both scare me.

The main danger is an arc connecting you to the mains electricity supply by an unexpected/unprotected route.

P.S. Have a look here

Shaun

Tue May 22 2007, 12:58AM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

Sulaiman is absolutely right. There's an old electician's saying: "Volts jolt, but mils kill." Mils meaning milliamperes. A good example is you take direct hits from a 400,000 volt Van de Graaff generator and feel just a little tic on your skin. That's because it's at most a few hundred microamps.

I personally have gotten one or two nice shocks from my 15kV 30mA NST (only through one hand though, not through the heart). It hurts like hell, but I'd do it again for $20. With a coil the size you describe you would probably use much less power than an NST this size, but that's up to you.

Even the final output arcs of the coil are near nowhere near lethal (however they will cause painful RF burns).

I'm not saying go touch your NST's leads and see how much it hurts. You should be able to avoid all danger by just using a little extra insulation and some common sense.

Bjørn

Tue May 22 2007, 01:00AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

We have some information about electrical safety here:

A reasonably small TC that is well constructed is quite safe if operated with some care.

sparky

Tue May 22 2007, 01:58AM

Registered Member #530 Joined: Sat Feb 17 2007, 07:56AM
Location: Victoria BC, Canada
Posts: 178

current is the true killer... as everyone has stated here. Voltage is simply a measurement of electron density on a conductor. I have been shocked by 100,000 volts AC ---even a Million or so as well....never felt a thing because the current was

a. very low
b. current frequency was very high

...on the other side I have also been shocked by 60 Volts AC but the frequency was low and the current was quite high.... that sent me to the hospital! Nearly killed me!!!

Part Scavenger

Tue May 22 2007, 03:12AM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

Personally, If I were in your shoes, I'd play around with some flyback circuits and get a taste of HV. They'll put about about 20kV, and you'd surprise me if you could injure yourself with something run off a couple 9V batteries. You could do it with a capacitor BTW, just so you know... but that's about all I can think of. But even then, I got shocked across the heart with a 1nF bottle cap I had made @ 26kV and I lived. It was extremely painful and scary though. I got salt water all on the rug too... LOL. It taught me to be careful with HV.

Flybacks are pretty safe in general, and you'll probably get shocked a few times, and learn what you can and can't touch. My first tesla coil was an 80W driven by a flyback and that 1nF bottle cap, I think I got 2" or so, and ran a super lightbulb plasma globe complete with a K'NEX base and everything.

Oh, and to answer your question in practical terms, 2kV if you're really good with spark gaps and ballasting, 4kV is doable but still now what I would call easy for a beginner.

Coronafix

Tue May 22 2007, 09:48AM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Is there any reason you are using a 2:1 ratio for your coil, a 6in former
only 12 inches high? What gauge wire are you using?
How long are you hoping the streamers to be?
If you really have no idea about HV, then as Part Scavenger
said, you should play around with some flybacks or ignition coils.
They make plenty pretty sparks.

Sedgewick17

Tue May 22 2007, 10:26PM

Registered Member #796 Joined: Mon May 21 2007, 10:53PM
Location:
Posts: 2

Thanks for all the help. I was concerned about safety because some websites said that a Tesla coil will fry you, and the other said that the electricity is so high that it will vibrate around you. The 1/2 ratio is coincidental itâ€™s this small because I wanted the Tesla coil to be portable, so that I would be able to conduct experiments. I would say my knowledge of high voltage is basic, and that I have a good idea of what not to touch. I am not yet a expert on all the technical terms, but if I don't know a word or symbolâ€™s meaning I will look it up before working with it.

Ken M.

Wed May 23 2007, 12:23AM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

I have a small TC based on Steve wards Micro circuit. It weighs about 5-7 pounds with all the plexi glass and top load, e.t.c, All for the same reason you want portability! and it uses a 8in tall by 2.5in coil. It's somewhat big, but still very portable, if the topload was removed to move the whole thing, the power in is only like 80-100watts. It'll still burn skin readily and its painful, but it'll still do decent discharges off a pointed breakout point, out a decent arc to ground.

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