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[TCML] Let's Get Small

With apologies to Steve Martin, I was hoping to inspire some discussion on
the small end of the Tesla Coil spectrum.  Not to suggest it's easy but
everyone knows if you throw 10KVA into a coil, you're eventually going to
get some big sparks.  Not much has been shared about the other end of the

Several years ago I threw together a palm-top sized coil powered by a yard
sale bug zapper transformer.  Bug zapper transformers are built just like
NST's, current limited but tiny.  Inspired by the recent Little Coil
thread, I dusted it off and made some primary coil tweaks and adjustments,
and finally got around to taking some pictures.  The performance is OK-ish,
maybe 2" to a nearby screwdriver, but I was really hoping to get some
similar sized sparks just wandering about the topload.  Yeah I have plans
to tweak some more, although such a small 4-turn primary is difficult to
adjust.  Looking for that round tuit.

Well, I was hoping to hear other successes in the micro-sized league and
what might be attainable.

Pictures and a short video are at:


Power source: 4.8kV/8.7mA Bug Zapper Transformer, modified to remove the
potted built-in ceramic capacitor across the secondary.

Primary C: .0094uF/8KV MMC (5x 47nF/1600V)
Primary L: Helical 4 turns PVC insulated 18AWG solid wire

Secondary L: 0.84”D x 4.43”L x #38AWG – 3.37mH
Top load: Pine disk, turned on drill press to form .75” x 3.4”
pseudo-toroid, Al tape covered

Spark gap: Single cylinder gap, .020” separation

Performance: 2.25” to a screwdriver blade (very little tuning performed)

Regards, Gary Lau
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