I’ve seen a ton of bike lights that use the power of pedaling to provide bikers with nice array of lights as they drive down the road. Well, here’s another awesome bike hack that shows you how to add a stepper motor-powered LED light. I really like this one as I do actually have a bunch of unused stepper motors laying around. (and I am sure you do too if you hack around a bit…)
Steppers come with different resolutions. Virtually all steppers are either 1.8° or 7.5° per step; (200 steps or 48 steps per revolution) the difference can be felt easily if you turn the spindle by hand. The 1.8° ones are obviously better for generating at really low revs, but also ‘top out’ lower. The coils in steppers have a relatively large inductance, and beyond a certain speed the output frequency gets so high that the impedance of the coils starts to become significant and limits the current. When making a stepper based generator, you need to keep the motor speed to around a couple of hundred revs per minute – something like the normal speed of a bicycle wheel.