Coil winder

Bench-tested

A stepper-driven bobbin winder for the Open Kalimba’s coils, and later for guitar pickups. Pi Pico, MicroPython, tested to 1,000 RPM.

The Open Kalimba needs a lot of identical coils wound with very fine magnet wire. I’d been winding on the lathe, which works but ties up the lathe, so I’m building a small winder for the home bench. It will also wind guitar pickups for the cigar box guitars.

Build

• Motor: a NEMA 17 stepper on a DRV8825 driver, with 12 V and 24 V supplies on hand.
• Controller: a Raspberry Pi Pico running MicroPython. (Two boards I thought were Picos turned out to be something else entirely; the real one arrived later.)
• Panel: a 1.3 in OLED turn counter, run/stop and direction toggles, a zero button, and a rotary encoder for speed.
• Frame: a plywood base on rubber feet with an upright for the motor, and a turned hub with a 4-40 set screw.

It’s single-axis on purpose: the wire is guided by hand, the way pickups have been wound for decades, so there’s no second traverse axis to build.

Status

The electronics and firmware work on the bench and run cleanly up to 1,000 RPM. Next: fit it all into the case, make the spools and winding arbor in the machine shop, and move the motor supply to 24 V.