Flame Triodes Don’t Need Any Vacuum

There is a rich history surrounding the improvisation of electronic components. From cats-whisker foxhole radio detectors using razor blades through radio amateurs trying antique quartz lenses as crystal resonators and 1950s experimenters making their own point-contact transistors, whenever desirable components have been unavailable the ingenuity of hackers and makers has always sought to provide.

In an age when any component you might wish for is only a web browser and a courier package away, you might think there would be no need for such experiments. But it is in our curious nature to push the boundaries of what can be made without a factory at our disposal, so there are still plenty of ingenious home-made components under construction.

One such experiment came our way recently. It’s a few years old, but it’s a good one. [Nyle Steiner, K7NS] made a working triode without any form of vacuum, instead its medium is a flame. He’s demonstrated it as a rectifier, amplifier, and oscillator, and while it might not be the best triode ever it’s certainly one of the simplest.

In a traditional vacuum triode the current flows as electrons released from a hot cathode and are able to cross the space because there are no gas molecules for them to collide with. The flame triode has an abundance of gas, but the gasses within it and its immediate surroundings are also strongly ionized, and thus electrically conductive. Flame ionization detectors have exploited this phenomenon in scientific instruments for a very long time.

A roaring flame might not be the most practical thing to keep in your electronic equipment, but [Nyle]’s experiment is nonetheless an impressive one. He’s posted a video showing it in action, which you can see below the break.

This is our first flame triode here at Hackaday, but we’ve featured quite a few home-made vacuum tubes from a simple effort using an automotive bulb to some very sophisticated tubes made to a professional standard over the years. If you fancy something from the semiconductor world though how about trying to build Rufus Turner’s design for a home-made transistor?

37 thoughts on “Flame Triodes Don’t Need Any Vacuum

      1. I think so too, but if it were a candle or a piece of wood I wonder how much electricity would flow through the smoke. I mean, they have detectors for that. Can’t seem to remember what they are called…

  1. This is a fairly classic experiment, I remember seeing a video on this in high school
    I have never seen it actually used for anything but a meter showing current flow so this is neat!

  2. This is fantastic! Does anyone know what fuels would create the best err, ion transfer medium? If propane or butane are good enough then I have some experiments to do. I can imagine a radio where the amplifier section is on fire! We need more articles like this.

      1. Works for me either way. Going to have to try burning wood anyway, just to compare/contrast. Those multi-hour alcohol gel cans seem perfect if the flame is protected from the wind.

    1. Problem is, as far as I remember from reading that page ages ago (it’s in my bookmarks), is that the triode has a gain of <1. So it's not a lot of use for the kind of amplifying where you make signals larger, unfortunately. It's still interesting, and the oscillator is a nifty use for it. Wonder if you could get RF and transmit from it? Even just CW.

      1. So, use it as a buffer stage?

        “Got an impedance mismatch you just can’t get to behave? Fix it with FIRE!!!” <— Now *that* would be a smokin' ad campaign for a Hi-Fi company that wanted to go a little paleo! Users could upgrade to different alcohol fuel mixes to bring out the best air and soundstage in their music of choice. YWIA, audiophiles.

    2. The best device would also use electricity to split water and have a H2 + O flame, but you may not even need a flame if you are using a helicon antenna plasma source. For extra nerd points you would reuse the waste heat with a thermo-acoustic generator. I’d go for thoriated tungsten for the emitter (a “red” TIG welder rod) and gold or platinum for the rest of the heat exposed wires. You only need two triodes for a NOR gate, which is universal, then you are good to go with your hydrogen flame powered computer. Needs some form of storage, preferably something else equally exotic. Any ideas?

  3. While parts for just about anything are a search and a parcel away. I believe the majority of us got our hacker spirit from wanting to do things we seen readily available but not having the funds to do so. Aside from that, a triode made with a flame in open air, much cooler than some small black package with pins sticking out of it.

  4. I haven’t had any luck building this triode, so far.
    I did with the zinc oxide detector diodes and the (different) zinc oxide tunnel diodes. I was able to make several very effective regenerative receivers for the AM Broadcast Band using the tunnel diodes I made at home. Great for DX, but take some patience to adjust.

  5. What really would have added to the coolness factor would have been a 1 gallon metal tin filled with water and a TEG (or a few ThermoElectric Generator’s) – a fully flame powered radio, it would sell very well to preppers.

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