don (04/29/83)
Subject: Tesla Coils I built several in High School. The biggest uses a 10 KV line transformer, but you can build small ones with Neon Sign transformers. (don't use Oil furnace transformers. I have burnt up many of them trying.) --------S ||| S---------> <-----S S S ||| S | S S S S ||| S --- S S T S ||| S --- C L1 S S L2 S ||| S | S S --------S ||| S-----------------S--S----(ground) T - 10 to 30 KV transformer C - Capacitor (I used tang jars wrapped in foil filled with salt water) S - Spark gap (half inch) L1 - a few turns of heavy wire coiled around base of L2 (but not touching). L2 - hundreds of turns of fine (28 gauge or more) wire on a plastic tube. (Say 2 inches in diameter and three feet long). You must tune the coil, so make sure C and/or L1 is adjustable. Adding or taking away tang jars was good enough when I did it. Try not to kill yourself! You can get much more sophisticated. My large coil had to have an air jet running on the spark gap to "quench" it, and the transformer drew about 200 amps. It was spectacular tho!
jj (04/29/83)
Two other things to note about building tesla coils: If you can make the spark gap adjustable, then do so. Needless to say, don't try to adjust it while it's running. Do try to set it so that that it's about 90% or so of the striking distance, that will eliminate the problem of quenching the arc. Run the coil only in a very well insulated room. The Ozone generation properties of a TC are phenominal, and the stuff isn't too good for you. Ohe yes... If you have an appropriately sized variac, try it on the primary of the neon sign transformer. You will find that for various tunings, the best drive will be attained at different drive levels. Adding more tang bottles (I use qt. coke bottles myself, don't forget the salt!) will make the drive level higher, so start with several, not one. Do be careful that you don't get breakdown along the edge of the tang (or coke) bottles, keep the outer foil (a wire into the salt water will do fine) at least 3 in or so away from the top. BZZZZZZZZZZZZZ