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TESLA COIL ~ First Fire-Up

Discussion in 'Electronic Basics' started by Blackbeard, Feb 4, 2005.

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  1. Blackbeard

    Blackbeard Guest

    We built our caps using the salt water/beer bottle trick. When we
    fired it up, the bottles started to glow purple.

    We never got any streamers. At the toroid, we noticed some slight
    sparking between the magnet wire and the connection to to toroid. Out
    of curiosity, we place a florescent bulb on top of the toroid. The
    bulb glowed on our test....but still no streamers. Since the bulb
    glowed, I assume it was getting power to the toroid. But we let the
    thing run for at least 30 seconds and never saw lightening.

    So we're stymied. Don't have a clue why we have no streamers. We had
    approx. 2mm on our spark gap.

    Here's how it's built...

    Primary coil - 15 turns using 1/4OD Copper tubing
    Secondary - 1500 turns using 24-gauge wire
    Magnet wire from secondary connect to toroid at the top
    Magnet wire from bottom of secondary goes to ground

    Capacitors = 6 bottle filled with salt water, wrapped with aluminum
    foil all daisy-chained together with wire.
    One single wire on the daisy chain connects to the transformer
    The second wire on the transformer connects to an aluminum pan that
    makes a connection with those bottles where the aluminum makes contact
    with the aluminum pan.

    Spark Gap - the spark gap doesn't make a whole lot of sense to me. We
    pulled a second wire off the two posts from the transformer and the
    spark gap was not connected in-line with anything. This is how our
    plans show this is supposed to be done.

    It sparked at the spark gap
    Bottle glowed purple
    florescent light lit up
    ....No streamers.

    We have to be close. Doesn't that florescent light glowing suggest I'm
    getting power up there?

    the toroid is made from a piece of semi-rigid aluminum duct attached
    to a 5-gallon paint buck lid to hold it's shape. We connected the
    toroid using an a plastic toilet flange connected to that 5-gallon
    bucket lid. The tolet flange fits right onto the 4" PVC pipe we used
    for the secondary coil.

    Any help or suggestions would be appreciated.
  2. That's not a good sign. Is the glass itself glowing, or the air
    around them? If the latter, that's just corona (air excited into glowing
    visibly, the electrical equivalent of pressure-caused leakage). If the
    former, you may be producing x-rays.
    Good powers of observation! Sparks where the secondary connects to
    the toroid indicates a poor electrical connection. Is it soldered,
    bolted, duct-taped, what? Did you remember to strip the insulation off
    before making that connection? I ask because we've all made these mistakes.

    The bulb lighting does indeed indicate several things; first, you're
    getting some power transfer from primary to secondary, thence to the
    bulb, so the thing is _trying_ to work.

    As for not getting lightning, likely it isn't tuned properly, among
    other things. BTW, try running it in poor lighting (make damn sure you
    know where everything is, including the main cutoff switch FIRST).
    That'll allow you to look the entire setup over for corona. Corona
    anywhere but the toroid is a Bad Thing.

    Side note; remember that the toroid is one plate of a capacitor whose
    value depends partly on its surface area. Once you do get the thing
    tuned, putting a fluorescent or anything else on or near the toroid will
    detune it somewhat from resonating with the primary.
    Might be too large a gap. Can you tighten it up a bit?
    Fine so far.
    Your post announcing the schematic showed up in the binaries group,
    but not the schematic itself. Does your ISP not allow you to send
    binaries? I'd _really_ like to see it.
    Good sign
    bad sign
    good sign
    I warned you not to be surprised. Tesla coilers proudly (as you're
    learning, for good reason) proclaim "first light" when that happens.
    Yep, just not enough.
    Sounds sturdy, which is a good thing.
    Show us the schematic!

    Mark L. Fergerson
  3. Blackbeard

    Blackbeard Guest

    It looked like the water was glowing. But I've never seen a tesla coil
    fire in real life and I wasn't about to get too damn close. The glass
    wasn't glowing. It must have been the air inside.
    No - I assume when you asked about stripping the insulation, you mean
    did we remove the fine film that coats that magnet wire. And no, we
    didn't. How do I do that without messing up the wire? It is not
    soldered. He used a piece of electrical tape to tape it directly to
    the aluminum part of the toroid. Wow...that wire stripping thing could
    make a huge different I would think.
    We fired the thing at night. The only visible things we observed were
    (or course) the spark gap and the purple glow in the bottle capacitors
    and a very faint spark where the connection goes from secondary to
    I gotcha. So as a test, I can use the light to see if we're getting
    any power at all. But we have to remove it or we've screwed the
    frequency. Makes sense. That didn't occur to us last night.
    We were told 2mm gap for a total of 12mm by having several gaps. I had
    the thought of building a spark gap that was only 1mm and doubling the
    length of the gap. I figured that using alligator clips, you could
    adjust the gap just by clipping on the desired pieces of copper. So
    the gap could be adjusted by 1mm quickly and easily. Is that a
    workable solution?
    The kid was a bit disappointed, but the glowing florescent suggest to
    him that he was on the right path. I think he'll pull it off with a
    little tweaking.
    I'll have to get the schematic from the kid when he gets home from
    school today. I'm trying to keep him in the drivers seat on the
    project. I'm pretty excited about it myself. I can imagine that his
    excitement is about 100-fold since he built the thing.

    I'll get that schematic and post later. We'll try removing the coating
    on that magnet wire where it connects to the toroid. Any chance that's
    the problem?

    I read that "tuning" can be done by adjusting the spark gap and by
    moving the connecting wire to different locations on the primary.
    Somebody mentioned using some sort of tesla coil math to figure out
    the "sweet spot". I don't have the slightest clue where to start on
    tuning this thing.

    I'll try to get some close-up pictures in addition to the schematics.

    thanks for you help
  4. Yep. X-rays is an extreme outside possibility, but I had to ask.
    Still, that corona is power wasted instead of going to the secondary.
    You bet it will. 24 gauge is easy to strip if you're careful. Scrape
    with an exacto knife or similar tool, just don't scrape copper off if
    you can help it. Electrical tape is fine for testing, but it really
    should be more firmly attached so that the copper is in direct contact
    with the toroid before it goes to school. Copper won't solder to
    aluminum without special solder and flux. One way to do it mechanically
    is to run a self-tapping sheetmetal screw into the toroid and wind the
    stripped part of the wire onto the screw just before tightening it down.
    That may change once you get the toroid properly connected and the
    primary tuned.
    Putting the bulb won't screw it up past saving, just detune it enough
    to make it work a little harder. Don't expect to get lightning while
    you're lighting the tube. FTM you can always retune it to work with the
    bulb on it...
    Yeah, but that changes the amount of energy going into the cap each
    cycle. OK, if 12 mm is what the plans say.

    From your discussion of his previous experience in school, some
    encouragement is definitely in order. Even if nobody else praises his
    efforts (many will rag him without admitting it's because he did
    something they can't) the satisfaction of "first light" will boost his
    self-confidence dramatically.

    Good for both of you. Just riding along can be a thrill, and knowing
    that the fruit of your loins can do things like this won't hurt _your_
    self-confidence, either! ;>)
    It's certainly _a_ problem.
    I could point you to webpages with equations all over the place, but
    it's likely a bit beyond your son unless he's in a high-school honors
    math program. Save that until after he wants to know how to build a
    really big one, then he can work them backwards to discover why you
    won't pay for an extra 100 amp power hookup.

    The plans you have should suggest where on the primary coil to attach
    the connection going to it, and that's a good place to start. Watch for
    corona on the toroid as you adjust the tap. The point where you achieve
    resonance (and breakout) will be unmistakable.
    Wouldn't hurt, if for no other reason to make sure you are reading
    the diagram properly.
    You're very welcome. I keep thinking back to my youth when I could
    have used some pointers.

    Mark L. Fergerson
  5. Blackbeard

    Blackbeard Guest

    I think I may have found a problem with the design. The bottles used
    for the bottle capacitor had two wires running down inside the bottle
    instead of just one. The idea was to daisy-chain. But having the two
    wires down inside each bottle, it looked like there was an arc between
    those two wires. He's re-doing the bottle capacitor with only a single
    electrode inside each bottle. That should eliminate that arc problem.
    And I assume that might have been the source of a major power draw and
    possible why the bottles were glowing purple.

    We did shave the coating off the magnet wire. At this point, the only
    problem that was noticable was the arc problem inside the bottle
    capacitors. And I'm not sure my "best guess" on that is correct. But I
    guess we'll see.

    It feels like we're getting closer. Might have streamers before the
    weekend is out. Any other ideas?
  6. Vidor Wolfe

    Vidor Wolfe Guest

    Blue/purple glow suggests corona discharge.
    Power is being robbed here.
    The cap is very leaky (as I suggested it would be.)
    2mm is not enough gap.
    The cap is not getting a high enough charge before the gap fires.
    Do you mean 2mm total, or 2mm between each pipe? 7 pipes = 12mm if you're
    going with your original gap design.
    The toroid should stop sparks at the top of the coil, so either you have a
    poor connection or the toroid needs to be larger.
    A glowing bulb is not a brilliant indicator of tune or power transmission. A
    gas filled bulb can be excited by the energy fronm the gap alone.
    However, I think that maybe you're going the right way.
    Do you get flashoever between the primary and lower secondary or sparks
    jumping between the turns in the middle of the secondary?
    Do you actually know the value of the capacitor or is this a poke and hope
    The gap is the essential.
    It's a switch to switch the power from the capacitor to the primary coil.
    The cap charges to the breakdown point of the gap and current flows back and
    forth round the primary till the voltage is low enough to stop the flow and
    the cap charges again.
    Mark H.
  7. Vidor Wolfe

    Vidor Wolfe Guest

    One wire in the bottle, one wire outside the bottle. This connects to the
    next bottles inside wire etc.
    That'll give you 6 in series. Can't say what the value is off the top of my
    head, but I'm sure someone on the list knows the dialectric constant of
    bottle glass.
    Work out the glass area and you can work out the value.
    All you have with the original setup is a high voltage gas generator. Bad,
    especially with sparks around.
    Another poster mentioned X-Rays.
    I think (IMHO) this is not an issue.
    The bottles are not under vaccuum. Hoever, a lightbulb that's not gasfilled,
    that's on the toroid should be avoided. Likewise old vaccuum tubes.
    If there's any green glow from the glass... Switch off.
    The X-Rays should only be soft, but you never know and you'll not know the
    accumalative amount either.
    Mark H.
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