I was clearing out the basement the other night and I found a box of stuff I’d put aside to build a Teeny Tiny Tesla Coil (TTTC).
Small Tesla coils are tricky, especially using the traditional “Spark Gap” approach as they tend to resonate at really high frequencies and this makes them difficult to tune.
Tuning involves moving a slider along the primary coil (the big one) until the LC primary circuit matches the secondary circuit – when that happens you get resonance and positive feedback and the shiny bedknob on top starts to spark – referred to as “streamer breakout”.
I calculated that the resonance of this coil (1″ diameter and 6″ high – 30 AWG wire) should be just over 2 Mhz. So after some serious fiddling around I managed to get somewhere close to that with the primary. None of my test equipment operates in the 2 Mhz range, so I had to do most of the adjustment through trial and error. For the technically minded the coil specs are here.
One unique side effect of this kind of coil is that it can make a cellphone drop calls, or at least give the user some nasty static, within a short range – so if building it on the kitchen table wasn’t enough to upset the boss, running it certainly does – especially during one of her lengthy phone chats.
Quick plug – If you are interested in building your own Tesla coil, check out “Teslastuff” on eBay (Alan) – he carries some great vintage looking parts to build traditional spark gap Tesla coils.