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Dr. Shark

Thu Mar 09 2006, 02:51PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

I am aware that I am on thin ice starting what could be considered an "adult" topic here, but I explicitely checked the rules and they dont mention it, so here we go...

For those who don't know, a violet wand is a handheld tesla-coil that was popular in the 1920s or so as a quack medical device. These days it is mainly used as an "e-stim" sex toy in the SM community, but I am convinced it is also a must-have for any serious HV-enthusiast. Finally, you don't have to keep HV out of your bedroom!

Of course these units are extremely overpriced like anything in the adult market sector, any anyway, why would you buy something that you could build yourself? This leads to my question:
What kind of of tesla coil would be suitable for this sort of thing? My SSTCs usually give burn marks when I touch them, but thats not exactly what I would call "stimulating". Also I had the impression that it is impossible for high frequency electricity to cause any nervous sensations, so even if it does not burn you (low duty cycle or whatever), how is it going to cause any sensations? I suspect that modulating the TC at a lower frequency might do the trick, but I don't think it was done that way in the 1920s. So how does this work at all? Any guesses?

From what I have read, even nowadays these devices work with a spark gap / relay type of switch (Wager's Hammer) which I think is really lame. A state of the art Wand should of course be driven SS, and because the size of the secondary would have to be limited to approximately the size of a Vitamin C bottle, the high frequency would call for a Class E amp driver. Efficiency would not matter much, since we are only looking for a few W of output power (I think!), but of course it would be nice to drive it off batteries. This would also make fatal accidents highly unlikely, since the ist just no way for a bunch of AAs to put out enough power to kill you.

I think we all agree how absolutely sick, stupid and dangerous this is, so no need to discuss this. I think it would be much more fruitful to talk about what characteristics make a TC burn you, which make them kill you, and which just tingle you without any ill side-effects. Gosh, I might even have disguised as a "Safe to touch for classroom demonstrations TC" thread, but I guess the perceived privacy of the internet makes me to lazy.

Nik

Thu Mar 09 2006, 03:52PM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

The old violet wands were pretty low freq and that is why they didnt burn (much). As you get higher and higher freq you are more likely to get a burn. Violet wands were more like an ignition coil IMO, if you are going to build a 2006 modle I would sugest looking more at iggy coil drivers and designs rather then TCs. That said, the only TCs that I have ever seen any one have the guts to touch, safely, are VTTCs, so perhaps you should go in that direction if you are hell bent on the TC design.

Dr. Shark

Thu Mar 09 2006, 04:07PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

I already suspected that the design might be quite different from a "normal" TC and more like an ignition coil, thats actually the reason I didn't put this in the TC Board. I found another good source of informations here

including schematics. They state "Coils are wound on wooden or plastic cores, better materials include Phenolic, Bakelite, or Noryl." so this definitely is an air core thing. Also the fact that it lights up flourescent tubes is quite TC-ish. Only the Wagner's Hammer does not fit the picture. Weird.

Well, I am sure somebody here knows, since we surely have a few people collecting electrical antiquities here.

EDIT: From

it actually seems that during Teslas days, using mechanical interruptors instead of spark gaps was quite common. Funny noone does this these days, possibly it works well only with relatively small, low-voltage coils?

Wolfram

Thu Mar 09 2006, 04:36PM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971

I actually have a complete violet wand set, around 20 tubes I think. It's quite old, but I don't know how old, I'll see if I can find out. I paid 1000NOK (around 150 US dollars) for it. Interested in pictures?

Anders M.

Dr. Shark

Thu Mar 09 2006, 04:41PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Definitely. I suppose you don't want to take it apart, but if you do, I would be interested in the internals aswell. Oh, and would you mind hooking it up to an oscillosope to figure out what kind of waveforms it produces? This would be valuable information for the scientific comunity, since I don't think anyone has ever done that

BTW, you got that really cheap, if you ever want to get rid of it drop me a PM .

EDIT: Found some more information on how they actually work:
Another misconception is that Violet Rays contain transformers and spark gaps. They actually contain a "self-
induction coil" and "interrupter". The self-induction "magnet coil" is really a single layer of wire that magnetizes an
iron core. Whenever the core is magnetized, the bottom contact of the interrupter (which is attached to a steel
armature) is attracted to the core of the coil, thus breaking the contact of the interruption. At this point the
collapsing magnetism in the core of the coil induces a high voltage back-emf in its winding of around 1-2 kV.
This high voltage is used to charge a condenser and discharge it across the disruptive discharge "resonator coil".
The combination of inductance and capacity form a high frequency resonant circuit, and it is through resonance that
a small coil operating from a 110V source can yield an output of over 50,000V with very little wire. (from

)

vasil

Thu Mar 09 2006, 07:43PM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

Without the discharge tube and with an iron core, the violet wand would make a nice stun gun.

teravolt

Fri Mar 10 2006, 03:55AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

I also have one of thease coils and it works like an old modle-T coil. Only one of the tubes still works, prety neet. I think they were sapose to be therapudic at the time. At the end of the tube a glow emits a glow and not hevey sparks. When you take the tube out it is like a tazer. Units like this are comersialy available that are designed to emit aboue 20Kv worth of arch and have an aluminuim probe sticking out of it.

Thingmaker3

Fri Mar 10 2006, 04:03AM

Registered Member #124 Joined: Fri Feb 10 2006, 01:30PM
Location: Portland Oregon
Posts: 35

These "violet ray" generators were plasma globes, not TCs. The antique I got to play with certainly fit the plasma globe profile. The fellow demonstrating it held the same opinion. He said it ran off a "broadband mechanical square wave oscillator" - a vibrator & step-up transformer. Tesla played with those as well as resonant coils, so confusion is possible.

Dr. Shark

Fri Mar 10 2006, 10:39AM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

I think the violet wand actually contains both. An ignition coil to provide 10kV or so, and a Tesla coil to provide the actual output. the circuit I propose is the following: Edit: This is probably wrongl

The big difference to a normal SGTC would be the fact that there is no sparkgap necessary, since the tank cap is charged up with very short bursts as the magnetic field in the IC collapses. Therefore the TC primary does not short out the IC output. I am not sure if this is plausible (e.g. the high inductance secondary of the IC producing a puse so short that the low impedance primary of the TC looks like a high impedance? Unlikely...), but it's the best I could come up with.

I have also got a guess at what makes the discharge more pinfull than a usual TC would be: Just like a stun gun, it produces very short pulses with a low duty cycle, as the TC just "amplifies" the spikes put out by the IC. When you get zapped by static electricity, the discharge probably takes as little as 100ns, and contains no Fourier components below 10Mhz, but still you feel it. Maybe this works the same.

Marko

Fri Mar 10 2006, 11:40AM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Iggy won't actually fire 10kV without its own tank cap, and circuit without SG you drew also does nothing, cap never charges because its shorted with few turns of wire.

As I understood the abstract WW is most ordinary TC with relay substitute of SG.
In school we have similar one and it operates on 24V AC, and vibrator relay (dont remember how was the coil connected, but it was current coil with few turns, probably fires when tank is full as SG would do or just vibrates at 50Hz ?)
The rest is normal, mini TC that gives out couple of cm sparks when tuned to resonance.

Most first TC's were actually also powered by small relay, the one presented by lord kelvin was powered by 110V to give out about 100kV.

And small TCs are used today in electroteraphy, weak short-duration sparks from small SG or relay TC cannot actually do any harm and are felt as minor tingling, found pleasurable by some people.

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