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Flaming tesla coil? (re. alcohol flame "triode")

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LAN_403

Conundrum

Fri Mar 13 2009, 10:15PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

Hi all.

Just saw this...

pretty neat. Kudos for the first person who builds a Tesla Coil using this effect..

Would think that the bitartrate would be required to get enough gain, but the sheer anusement of a TC with no semiconductors has to make it worth trying.

-A

Shaun

Sat Mar 14 2009, 12:06AM

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

Conundrum wrote ...

the sheer anusement of a TC with no semiconductors has to make it worth trying.

Funny you should mention this, I've actually built a TC without any semiconductors whatsoever. It was a simple HV transformer charging a capacitor which was in series with an inductor+spark gap to form an LC resonant circuit! Sound familiar?

But seriously, I remember reading about this on TDU's site (in the Failures section). It seems very simple to construct at home and would be really cool if it turned out to work well.

Frosty90

Sat Mar 14 2009, 08:49AM

Registered Member #1617 Joined: Fri Aug 01 2008, 07:31AM
Location: Adelaide, South Australia
Posts: 139

I gave the 'flame diode' a try today and the results are quite cool.

With a salt coated copper cathode and a steel anode, i was able to get about 10 microamps through it, and the rectification works quite well. Just from what ive noticed so far, the only thing that seems to limit the current is how hot you get the cathode (has the most effect, even the wobling of the flame causes a big change in current), the amount of salt on the cathode, and the surface area of the cathode. Using a bigger anode didnt help, but it also seems that the temperature of the anode has a big effect. Also the positioning of the cathode in the flame has a big effect, and for some reason i found it woked best with the cathode near the top of the flame and the anode in about the middle. I havnt tried the triode configurtion yet, thats next though.
The website also mentions that potassium compounds 'greatly increase' the conductivity, so I'll have to give that a go.
I think you'd be hard-pressed to get a tesla coil out of this, unless you built a huge one with a big burner and big electrodes and good compounds to coat the cathode with.
Very interesting to try though.

Cheers

Shaun

Sat Mar 14 2009, 08:52PM

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

Perhaps it would help to use some thoriated tungsten welding rods as the cathode? I'm sure that would increase the current, though it is probably not the ideal shape.

Conundrum

Thu Jun 04 2009, 09:17AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

idea:- connect multiple flame triodes in parallel like the arrangement in power MOSFETs...

could work, and should be fairly easy to set up using a continuous coated spring along one edge of the flames as the gate, and a thorium welding rod common anode at the top.
This approach should yield more current flow and ought to work with a simple VTTC setup, possibly even in push/pull mode with two devices.

Another interesting idea, what about plating thorium from a welding rod onto a spare piece of copper...
could work, and would multiply the gain many times.

Failing that, a "ghetto" way to make coated filaments is to preheat the heater to several hundred Celsius with an induction heater or soldering gun and dip into the tartratre- should work.

I want to see them try this one on "Mythbusters"..

-A

Mattski

Fri Jun 05 2009, 01:50AM

Registered Member #1792 Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527

The reverse breakdown voltage is rather high already (2kV), but it's apparently dependent on the anode temperature, which makes sense. Maybe it can be improved by using a length of copper tubing with water running through it as the anode. That way even though this is small current more power can be had.

I am also curious what kind of parasitic capacitances this device has. It has large components, but the separation is also large.

Frosty90

Fri Jun 05 2009, 06:26AM

Registered Member #1617 Joined: Fri Aug 01 2008, 07:31AM
Location: Adelaide, South Australia
Posts: 139

Maybe it can be improved by using a length of copper tubing with water running through it as the anode.

When i tried the diode version, a big anode (heatsink) definitely hepled. Im thinking that perhaps to get anymore than a few milliamps (i could only get a few microamps) you would need a huge supply of ions. Maybe a rather high preassure gas flame, and a small 'crucible' of molten salt in the base of the flame to supply a good volume of ions. You could use a graphite crucible and then this could be the cathode (although i seem to remember reading that molten NaCl corrodes graphite).

Failing that, a "ghetto" way to make coated filaments is to preheat the heater to several hundred Celsius with an induction heater or soldering gun and dip into the tartratre- should work.

I tried this, but it ended up to be more effective to simply dip the cathode in wet salt!

Tesladownunder

Sat Jul 11 2009, 03:25AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

As mentioned above, I had played with this before (based on that article) and it is on my "Failures" page.
Re-reading the article I seem to have completely missed the fact that cathode needed a salt coating. I was surprised I had such a negative result and presumably that is why.
So I am now going to fill my back yard with a massive array of propane powered burners with tungsten electrodes coated with lithium salts and hook it up to my big TC ...

Proud Mary

Sat Jul 11 2009, 04:08AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Well I never! I knew about electricity from hot gases, but an oscillator!

United States Patent 3873860

Mixed potassium-cesium seeding of a high temperature combustion gas is employed in production of electricity by means of an open-cycle MHD generator.

Presumably, you could try other twin triode oscillators, like the Franklin.

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