Musical Tesla Coils Perform Zelda 82
heychris writes "You've gotta love the Chicago Tribune's story on Tesla Coil hobbyists from the first sentence. 'Under a starry Saturday sky behind a Lake Zurich warehouse, three men unload a small flamethrower, electric cabling, neon-tube "light sabers," about 80 pounds of chain mail and two 7-foot devices that look like monster-movie props.' So what does one do with 1.6 million volts and a Tesla coil or two? Play 110dB music, of course."
DragonCon (Score:5, Interesting)
They have a similar setup every year at DragonCon in Atlanta during the "Mad Scientist's Ball". I've never actually been that that particular track due to some insane lines (queue up 2-3 hours early if you want to get into that one), but speaking to other attendees it's been pretty cool, and certainly is popular every year.
Re:Epic ... (Score:3, Interesting)
I've seen a couple of these videos, and it really doesn't have the staying power of the flaming tuba [youtube.com].
Tesla Coil recipe using an old CRT (Score:3, Interesting)
You can easily make a Tesla coil if you have an old busted TV to rip apart. In general, the older and bigger the TV is, the better. And color TVs are better than black and white. This won't be a *great* Tesla coil, but it will throw a spark a few inches long and you can do all the standard Tesla coil tricks with it (St. Elmo's fire, etc.) without investing too much time or money.
Yank the flyback transformer out of the TV, and discard all its primary windings. Keep the big high voltage secondary winding (the one with the zillions of turns). It's usually encased in rubber and may look like a big rubber wheel. Its main lead has really thick insulation and connects to the side of the picture tube (where it looks like a stethoscope). The other lead (the ground) won't be as heavily insulated.
The only other parts you need are two NPN power transistors (2N3055), two 5W power resistors (20 ohm and 200 ohm), some wire, and a good supply of DC current (12-24 V). The circuit is a piece of cake. The first time I did it, I put the whole thing together with alligator clips.
This circuit has two primary windings around the flyback transformer core. The power winding is 8 turns, with a tap in the middle. The feedback winding is smaller (4 turns), also with a tap in the middle. The power winding leads connect to the collector leads on the transistors, with the center tap going to the +24 V DC power source. The feedback winding leads connect to the gate leads, with the center tap there going to +2-3 V DC (connect the resistors in series across the DC power to get the lower voltage in between). The emitter leads are grounded.
As current flows through one transistor, the changing field in the core induces a voltage in the feedback windings that turns that transistor off and the other one on. Then current flows the other way, and the same thing happens in reverse. So the circuit tunes itself to the proper frequency. But it also means that the first time you power it up you run a 50-50 chance of connecting the leads to the wrong transistor gates, in which case you get a stable DC circuit. So if it doesn't work the first time, try exchanging the gate leads.
This circuit is fairly well known, and doing a Google search for "flyback" and "Tesla" I found a schematic [aaroncake.net] for it right away. The guy mentions on that page that the transistors get really hot and he is not kidding- they do. Don't leave it running for more than a minute without a heat sink. The RF noise generated by Tesla coils is incredible, so expect to generate some interference. They make lots of smelly ozone. And if you let a spark go through paper, you can start a fire so be careful.
If you're lucky you can get 20-30 kV, which throws a purple spark a couple inches. (I only got about 4 kV out of mine- the spark was about a half inch long.) Pick up a neon bulb when you're at Radio Shack- these light up if they're around. If you touch one terminal of a fluorescent to ground then half of it will glow brightly between that end and the place you are holding it. The effect on a candle flame is interesting. Don't stick your bare finger near it because the spark does hurt if it hits unprotected skin. But if you hold a metal object and use that to touch it, you don't feel a thing (it's high frequency AC). Cool tricks include having sparks jump from the coil to a metal object in your hand, having sparks jump from a metal object in your other hand to ground (even a lousy ground), and having fluorescent tubes glow softly if you hold them in your other hand.