I took apart a scanner and found a stepper motor in it: it’s a Mitsumi M42SP-4NP (datasheet: http://www.scribd.com/doc/24950646/Motor-m42sp-4np-Datasheet#scribd). In the datasheet it says it’s a Unipolar motor that should be driven with 2-2 phase excitation. The motor has only 4 leads however. When I look online to see how to drive a unipolar motor they always have 5 or 6 leads. How do I drive a unipolar motor with 4 leads?
In the datasheet it says it's a Unipolar motor that should be driven with 2-2 phase excitation.
I think that is wrong. Otherwise test if the case is connected to the windings with a meter.
You are correct, the leads are not connected to the casing and I tried driving it like a bipolar motor and that works.