Realevents writes –
The lunatic progress of the computer industry means that there are enormous numbers of small stepper motors in rubbish – most printers contain at least two. Larger ones from really big dot matrix and some laser printers can be used as small electricity generators, capable of outputs between several and twenty Watts. (See the page on steppers as generators) There are also great quantities of smaller ones which are not able to generate a really useful amount of power. On the other hand, they are made to a high quality standard and can operate effectively at very low rotation rates, so it’s tempting to find things to do with them.
While using a small motor to show some people how steppers could be used as generators, I made up a coloured LED display to demonstrate its multi-phase output. We quickly realised its decorative potential, and I went on to make an improved version which used a discarded plastic car hub disc to mount the motor and the LED’s. When the disc is spun with the spindle held still, the LED’s come on in a stationary pattern determined by the magnetic pattern in the motor’s rotor.
Stepper motor twirly disc – Link.