My First Tesla Coil
After nearly nearly five years, including a three year hiatus, I finally have a working Tesla Coil to show for my efforts! Now I will work on improving this design, all the while plotting to build my next bigger, badder coil...
The first component I acquired was the high voltage capacitor. I found this quite by accident! After having two RCA high voltage splitters go bad, I decided to destroy one with a sledge hammer. Inside, I found a rolled capacitor labeled .006mf / 30kv - exactly what I had been looking for! Or so I thought. I sealed the actual capacitor inside a piece of PVC pipe filled with silicone sealant. Two bolts provided connections to the capacitor.
Looks pretty good, huh? That's about all it did. After blowing two (maybe three - I lost count) of these capacitors apart, I had to switch gears. With a little help from my dad, we built up a beer-bottle capacitor out of, well, beer bottles.
The outer electrode is made from am interestingly bent piece of aluminum flashing that weaves itself around all of the bottles. The inner electrodes inside the bottles are formed from brass rod stock. The electrolyte, both inside the bottles as well as the plastic container, is a strong solution of Epsom Salt and water with a ¼" thick layer of vegetable oil poured on top to prevent evaporation and flash over - about ¾" thick in the bottles. Mineral oil would have been preferred, but I used what I had on hand.
Then comes the secondary coil - probably the most recognizable part of a Tesla Coil.
I'm not sure if I'm more proud of the coil or the device that I had to build to wind the coil. For the frame, I used the back of a computer monitor. A Power Wheels geared drive motor turns the coil form. To keep track of the number of turns I've wound, I made a disc with a notch cut out to interrupt an optical sensor which triggered the counter from a photocopier. And for the final touch, a plastic candy cane serves to hold the magnet wire feed spool.
Next I needed something to load the secondary with. Not being made of money, I can't afford a spun aluminum toroid, so I'm going to have to improvise.
I bought two frying pans from my local dollar store, ground the handles off and soldered the two pans together. I soldered a nut to one of them to make the top load easily interchangeable. I was going to weld the pieces together instead of soldering them, but the wire welder I have kept blowing holes through the thin metal. A 140 watt soldering gun and a little rosin did the trick. The only thing about this that bothers me is the ridge where the solder is. Since solder only goes surface deep, I couldn't grind that down smooth. I'm hoping it doesn't affect the coil any.
To minimize arcing, I used television high-voltage anode lead to connect all of the components together.
And finally, after all that... I present to you... My Tesla Coil!
Next I plan on building a rotary spak gap to use in place of the static two screw design I'm using now. I am also looking for a higher voltage neon transformer. The one I am currently using is 7.5kv although the coil is designed to run on 9 to 12kv.
If you would like to build your own, click here to download the plans.
When powering up your own Tesla Coil, make sure that there is nothing electronic within 20 feet of your coil. And if the coil isn't on it's own dedicated circuit, make sure that you have a heavy-duty filter inline with the neon transformer.
Let me tell you from experience that Tesla Coils are superb sources of Electro-Magnetic Pulses through the air and RF spikes over the power lines. After firing my coil up for the first time, I had to replace blown filter capacitors in a desktop computer and a scrolling LED sign that were on the same power line. A cordless telephone that was about fifteen feet away from the coil was scrambled and had to be reset. The worst / most expensive damage was done to my motorcycle that was about twenty feet or more away. Even though the bike wasn't running, the CDI ignition module was fried.