A Generator built from a Stepper Motor and Supercapacitors

2022-02-12

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In this video I'll show how i used a NEMA17 stepper motor as a hand-cranked generator to charge a supercapacitor bank, which can then be used to power all sorts of things like lights, radios, or even start a fire for a survival situation.

I found that using a stepper motor as a generator was far more effective than trying to build my own with magnets and coils. With a 3:1 overdrive on this small NEMA17 motor, I could easily generate 15-20V open circuit, or sustain around 2 watts of output without much trouble.

The generator uses a pair of parallel bridge rectifiers (one for each coil set on the stepper) to charge a supercapacitor bank to 5.4V. It takes about 130-150 turns to fully charge a 16.5F capacitor bank, which can be done in under one minute, and keep the main light on for close to 10 minutes.

To protect the capacitors against overcharging, i built a circuit using an op-amp comparator to turn on a MOSFET when the capacitor voltage goes above 5.3V and short the capacitors to prevent overvoltage. I found this to be a more effective solution than simply using a zener diode.

Notable Hardware:

-NEMA17 Stepper motor. Exact model doesn't really matter (i found mine in a junk drawer).

-GT2 belt & Pulley, 60T and 20T:

https://www.amazon.com/Zeberoxyz-Synchronous-Aluminum-Timing-20-60T-8B-6/dp/B08QZ4365D

-470F / 2.7V Supercaps are Illinois Capacitor model# DGH477Q2R7

-3.3F / 2.7V Supercaps:

https://www.amazon.com/MCIGICM-Capacitor-capacitance-tachograph-Electromechanical/dp/B07BLQGRQY/

-Bridge rectifiers were GBU808 harvested from random scrap devices. Really any bridge rectifier should work for this application, though.

STL Files:

https://www.thingiverse.com/thing:5241682

Music Used:

Kevin MacLeod - George Street Shuffle