Re: TESLA COIL ~ First Fire-Up

From: Blackbeard (Blackbeard_The_Great_at_Lycos.com)
Date: 02/05/05 

Date: Sat, 05 Feb 2005 04:59:59 GMT

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?

On Fri, 04 Feb 2005 14:22:26 -0700, Mark Fergerson <nunya@biz.ness>
wrote:

>Blackbeard wrote:
>> On Fri, 04 Feb 2005 08:02:15 -0700, Mark Fergerson <nunya@biz.ness>
>> wrote:
>
>>>Blackbeard wrote:
>>>
>>>>We built our caps using the salt water/beer bottle trick. When we
>>>>fired it up, the bottles started to glow purple.
>>>
>>> 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.
>
>> 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.
>
> 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.
>
>>>>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.
>>>
>>> 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.
>
>> 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.
>
> 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.
>
>>> 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.
>
>> 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
>> toroid.
>
> That may change once you get the toroid properly connected and the
>primary tuned.
>
>>> 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.
>
>> 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.
>
> 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...
>
>>>>So we're stymied. Don't have a clue why we have no streamers. We had
>>>>approx. 2mm on our spark gap.
>>>
>>> Might be too large a gap. Can you tighten it up a bit?
>
>> 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?
>
> Yeah, but that changes the amount of energy going into the cap each
>cycle. OK, if 12 mm is what the plans say.
>
><snip>
>
>>>>...No streamers.
>>>
>>> I warned you not to be surprised. Tesla coilers proudly (as you're
>>>learning, for good reason) proclaim "first light" when that happens.
>
>> 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.
>
> 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.
>
><snip>
>
>> 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.
>
> 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! ;>)
>
>> 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?
>
> It's certainly _a_ 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.
>
> Yep.
>
>> 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 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.
>
>> I'll try to get some close-up pictures in addition to the schematics.
>
> Wouldn't hurt, if for no other reason to make sure you are reading
>the diagram properly.
>
>> thanks for you help
>
> You're very welcome. I keep thinking back to my youth when I could
>have used some pointers.
>
> Mark L. Fergerson

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