Mini Coil Complete! - Pictures

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Original poster: "Chris Roberts by way of Terry Fritz <teslalist-at-qwest-dot-net>" <quezacotl_14000000000000-at-yahoo-dot-com>


Hi everybody,

I tried to get some photos of the mini coil posted earlier but the digital 
camera I had just wouldn't pick anything up. So I ended up using some 35mm 
film and scanned them in. The first picture is the coil itself, along with 
the larger 6" coil that's currently out of service. It gives it a good 
scale though. The second picture is of the coil running full power with a 
couple of overhead incandesent lights on. I have a really long breakout 
wire on it mainly because I can mess around with what angle the sparks will 
come out easily. The last photo is of the coil running full power again in 
complete darkness while a flashlight "painted" light over the coil. This 
way, you get the sparks in full detail but can also see the coil in detail 
also. Both exposure times were about 2 sec.

<http://hot-streamer-dot-com/temp/miniattoribus.jpg>http://hot-streamer-dot-com/temp/miniattoribus.jpg

http://hot-streamer-dot-com/temp/mini2.jpg

<http://hot-streamer-dot-com/temp/mini1.jpg>http://hot-streamer-dot-com/temp/mini1.jpg

The coil stats are as follows:

Power Supply: a 3kV/20ma NST with all of the shunts removed. I don't know 
how much current it's running now.

Spark gap: 2 copper pipes with adjustable spacing. Simple.

Capacitor: 4 - .15 mfd geek caps with total capacitance at .0375 mfd. These 
were salvaged from the large coil when one cap died and I didn't have a 
spare. So the large coil is on hold for a while.

Primary: About 10 turns of 1/4" copper tubing, tapped at about 6-1/4 turns. 
As you can see in the photos, the primary is wound using coax cable 
connectors. The primary was originally sitting right on the spray paint 
which I thought was leaking power between the turns, so I recently put a 
layer of rubber underneath. That seemed to increase spark length by about 1 
or 2 inches.

Secondary: 1.9 OD pvc wrapped for 10-1/2" with 32 gauge magnet wire.

Top load: 3" flex duct with a 12" outer diameter. I know it's kind of large 
which is probably the reason there are no sparks without a breakout point, 
but it's what I had on hand.

Output: I get about 7-1/2" sparks from this thing when tuned properly. 
These aren't record breaking efficiencies, but it was a very fun thing to 
build and play around with. I have actually gotten to bring it to a high 
school orientation meeting for display for the electronics class. We got a 
few people to be brave enough and draw small amounts of corona to their 
fingers. The noise was enough though to make everyone in the room jump 
slightly when we first fired it up. (a couple of the cheerleaders that were 
doing their own display also freaked out a little : ) If you have any 
questions or see something that you think might help, feel free to ask/tell 
me. Thanks!


-Chris

"The trouble is not that the world is full of fools, it's just that 
lightning isn't distributed right." -Mark Twain

"Only two things are infinite, the universe and human stupidity, and I'm 
not sure about the former." -Albert Einstein