A Generator built from a Stepper Motor and Supercapacitors

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:
www.amazon.com/Zeberoxyz-Synchronous-Aluminum-Timi…


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

-3.3F / 2.7V Supercaps:
www.amazon.com/MCIGICM-Capacitor-capacitance-tacho…

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




STL Files:

www.thingiverse.com/thing:5241682


Music Used:

Kevin MacLeod - George Street Shuffle