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Author Topic: Cooking up some Coils  (Read 2018 times)
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Posts: 1089
Well it's science fair week here which means chaos will ensue and disaster is imminent. My son has decided to electromagnetically levitate Lego and my daughter has decided to build a 500,000 volt Tesla coil to see how it fairs against the Van De Graaff generator we built last year. Dusted off the old coil winder and my daughter wound the 24" 20ga 500 turn secondary for her Tesla coil and while we were at it I decided to turn a couple 24" 16 ga 450 turn primaries for my Cook Coil experiments next week after the science fair.

Here are a few pics, to turn coils I use my trusty 12v variable speed Dewalt drill in a rig I built. It works well and it only takes about 4-5 minutes to turn a 400-500 turn 24" secondary.

AC

« Last Edit: 2015-02-23, 18:50:55 by Allcanadian »


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"Great minds discuss ideas; average minds discuss events; small minds discuss people." - Eleanor Roosevelt.

Be careful when you blindly follow the Masses... sometimes the "M" is silent.
   
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Hey AC ! Very nice... I send "good luck wishes" to you and kids for their science fair projects!

Here's my favorite Tesla Coil Designer page:
http://www.classictesla.com/java/javatc/javatc.html

And the calculator actually works! If you load the "sample coil" then look at the bottom of the page you'll see a "picture" of the coil setup.
Then you can change the parameters in the various windows to match your design and check the "picture" to see how it changes.

Here's the latest coil I made using this calculator. It's powered by 24 VDC from 2 ea. 12V 5A-H batteries (UPS replacements) powering a Royer oscillator driving a flyback transformer for the primary power supply, and uses a stack of doorknob capacitors and a fixed, multielement spark gap made from some brass tubing segments.
http://www.youtube.com/watch?v=d_VtbfhyvUU
http://www.youtube.com/watch?v=aIZClhoU2Xk
   
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I do have an asynch rotary gap on my largest TC, a 2-kilowatt class coil with "magnifying" extra coil. I haven't run it in ages though, it requires more room than I have available here. Even my observa-yurt is too small for it.

I have a smaller rotary gap under construction, intended for use with the MOT-DC coil that currently uses a simple 2-element, compressed-air-quenched spark gap, and/or for the hybrid SS-SG coil in the video above. But I'm stalled on that, just out of lazyness mostly.

Yes, there are interesting interactions between the gap breaks-per-minute and the power throughput of the coil. I can't find the page that talks about this issue right off-hand; I've been working on SSTCs more lately.

   
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Posts: 1089
Hey TK

Awesome setup and video's, two thumbs up.

I started with a 6000v supply, spark gap and loose coupled 10 turn primary yesterday but didn't like where it was going because I didn't have enough HV caps. The supply was only 150 VA on the 120v primary side so I figured I was hooped but tested it anyways. It didn't surprise me because I seem to have real issues doing anything in a conventional sense. It just seems so much easier to make it up as I go tweaking along the way.

I'm going to use an auto-resonant circuit I developed a few years back which basically uses the HV field from the secondary to switch the mosfets on the primary. Which is really little more than a glorified joule thief circuit without the feedback coil using the field delay/threshold to switch the primary. It seemed to work very well at 60KV and generally starts very close to resonance at which point the threshold is set to bring everything into sync. I'm still throwing around idea's how to have the primary frequency always seeking the next best higher harmonic of the secondary frequency and settle out somewhere near max efficiency. I'm asking a lot, lol, and it remains to be seen if this can be done within the time frame I have which is about a week.

Ac



---------------------------
"Great minds discuss ideas; average minds discuss events; small minds discuss people." - Eleanor Roosevelt.

Be careful when you blindly follow the Masses... sometimes the "M" is silent.
   
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