DIY : $2.00 Tiny Tesla Coil
Although it’s designed for 5VDC input (at up to 200mA or so,) actually it works down to around 0.5V. Most of them can tolerate a 9V battery just fine, and a few can make it all the way to +15V before running into problems. To smoothly alter the high voltage output, just change the voltage of the DC input.
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