Build one for under $20. Here's exactly how.

Magnet wire · Neodymium disc magnets · 2N3055 transistor · Rotor wheel · Resistors · Diode · 12V battery. Total cost: ~$20.

Wrap 20AWG magnet wire around a ferrite core. Wind a second strand alongside (bifilar) for your trigger lead. Coat with varnish to hold the windings.

Drill evenly-spaced holes in your rotor disc. Epoxy 4–6 neodymium magnets, all same polarity facing out. Let cure fully — balance matters.

Trigger coil → transistor base via 1kΩ resistor. Energizer coil → collector. Flyback diode across the coil. Connect 12V battery and give the rotor a spin.

Full step-by-step video tutorial — no soldering required for a first build. Subscribe and watch the whole series.