Brag about your Tesla Coil/s!

Discussion in 'General Electronics Chat' started by DerStrom8, Dec 15, 2013.

  1. DerStrom8

    Thread Starter Well-Known Member

    Feb 20, 2011
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    Moderator Comment:

    Thread split at OPs request.


    inwo, in the second photo of your second post, is that a Tesla coil under the dust cover?
     
    Last edited by a moderator: Dec 15, 2013
  2. inwo

    Well-Known Member

    Nov 7, 2013
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    Yes it is.
    Built before the web, and before I knew better.

    Powered with a 15,000v potential transformer.
    Ammo box capacitor. Oil filled. Aluminum plates. Dielectric is colored plastic from a sign making machine. Anything else I tried punched thru.:eek:

    Rotary gap inside an 8" pvc cap.
    Top load is from an early 1960s popular electronics van de graaff project that I never finished as a teen.

    Last fired in that room 10 years ago, before it was full of junk. Ceiling still has ground screen.

    Get a lot of requests to bring it to life. Not sure if I'm smart enough to rebuild it if it blows.:(
     
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  3. DerStrom8

    Thread Starter Well-Known Member

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    Nicely done! I've built several before and am in the middle of building one that I started almost a decade ago :eek: Just don't have much time on my hands anymore. Secondary is approximately 850-900 feet of 26 AWG enameled copper wire wound around a 4" PVC drain pipe. Powered by either a 9000v 60mA NST or a 12,000v 30mA NST. Still trying to get the capacitors right (currently have a dozen beer bottle capacitors with a saltwater solution) but they've been sitting for about 3-4 years. Probably no good anymore. Also trying to get my hands on some 1/4" diameter copper tubing/wire for the primary for cheap, but right now I just have some 12 AWG solid copper wire. Spark gap is currently static, though I have an old vacuum cleaner motor and a variac I use to adjust the speed. I'd like to make that into a rotary spark gap at some point. I'm using two MOTs as chokes. I've been considering changing out the circuitry for a dual resonant solid state configuration of my own design, but I still have to do some testing to make sure it'll work properly. I've had this project on hold for a long time and I would love to pick it up again. Unfortunately I have no idea when that will be....
     
  4. inwo

    Well-Known Member

    Nov 7, 2013
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    Made a really nice jig for winding.

    Just a couple threaded rods with timing sprockets and hand crank.

    Fed the wire under tension across the threads of one rotating rod.
    The other rod was the coil form axle.

    Have no idea how I got it right. Seemed easy back then. The ratio was just right to space turns correctly.

    When I say correctly, means, no idea!

    Started with secondary. (about a half dozen to get one to work)
    Then capacitor, sized according to what fit in the ammo box.

    Last was trial and error tuning with small nst and simple spark gap.
    What a great feeling when it came into tune.

    Kept improving until it's scary to run.
    4 to 5 foot arcs. More like arcs than streamers. Super loud crashing noises.

    Grand kids are 8-12 now and never saw it run.
     
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  5. DerStrom8

    Thread Starter Well-Known Member

    Feb 20, 2011
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    I am thoroughly impressed! I still haven't gotten my larger one to work. It stands about 5 feet tall on a wooden base I built. For winding I simply made two wooden end caps that fit into the secondary and mounted the whole thing on a woodworking lathe, but turned it by hand (never powered the lathe up for fear that it'd go too fast). Worked pretty well, though I had a large groove going along the length of my thumb, where I was guiding the wire, that stayed for a good 4-8 hours. Winding itself only took 1-2 hours, but then I left it on the lathe to put on several coats of varnish.

    Back to the caps, I've tried many different styles--soda bottles (which burnt through rather quickly), glass panels, waxed paper, sheets of plastic, etc. Still haven't found the best setup, though I haven't been able to really search for about 3 years. I'm leaning more and more towards a MMC or a single, large capacitor that's designed to operate at high frequencies. I hope I can get some free time to work on it.

    I wonder if we can move this thread to off-topic, since we seem to have digressed from the original question? I'll see about asking a mod.
     
  6. alfacliff

    Well-Known Member

    Dec 13, 2013
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    when trying different things with my small coil, 3 ft tall, 9 inch sparks, I found that if you have a punch through from secondary to primary, you are poerating on a harmonic of the primary. increase the number of turns on the primary to lower the frequency to that of the secondary.
     
  7. DerStrom8

    Thread Starter Well-Known Member

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    In order for a Tesla coil to run properly you need to operate at harmonic frequencies. That's how resonance works. A better idea would be to decrease the frequency of the tank circuit and increase the height of the secondary. Also putting in a strike rail above the primary helps prevent the secondary output from striking the primary.
     
  8. inwo

    Well-Known Member

    Nov 7, 2013
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    Thanks for that!
    I was about to apologize for the hijack, and let the tesla discussion die.:(
     
  9. inwo

    Well-Known Member

    Nov 7, 2013
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    Here is my spare capacitor.

    The one I'm using now, was able to squeeze a little more. .015uf
    Also soldered in a drain plug near the bottom for possible water removal.

    Only the one plate is shown. Can't find the other sample. It would be similar, but only one connection point in the middle. Connects to middle insulator.

    Dielectric plates rest on bottom. Aluminum plates hang from the top hardware.

    After stacking the plates, they are connected with long 6-32 hardware. Aluminum stand-off spacers between each plate.

    Squeeze in tightly. Fill with oil and put in oven. Wasn't to popular in the kitchen for a while, as I recall.:eek:

    Have no idea what type of plastic this is. Tried plexiglass and anything else I could find in junk pile. Even glass will break thru.

    Whatever it is, holds up well!
     
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  10. DerStrom8

    Thread Starter Well-Known Member

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    Many thanks to Bill for splitting off the thread!
     
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  11. Brownout

    Well-Known Member

    Jan 10, 2012
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    Where do you get the insulators?
     
  12. inwo

    Well-Known Member

    Nov 7, 2013
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    Old neon sign transformers.
     
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