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Stepper Motor Guidance

Hello, thanks in advance for any guidance you can offer on how to use these stepper motors I have.

they are 4 wires, red, black, yellow, gray.

3.1v, 3.6 ohms, 7.5 degrees


I know how to operate servos with PWM, but steppers seem to be more complicated, some have 4, 6, 10 wires etc.  unipolar, bipolar, etc.

based on what I've said so far, what can you tell me about what I have here, and how to control them, hopefully with PMW like servo's?

thanks again,




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Thanks TinHead, thats exactly the guidance I was looking for.

now I know its bipolar (they got meds for that :-), and now I have to learn about dual h-bridges.

I will review that site.  

... get some head ache meds though :D

4 wires means bipolar so you need a dual H bridge to drive one motor such as l293 or l298 or something specialized if you can afford it.

I cannot locate a datasheet for this motor but 7.5 degrees means it has 24 steps per rotation, which might be enough depending on the application you wish to employ these motors on. 

Stepper motors work in a different way then servos or DC motors, well they step. So the rotational speed is controlled by the frequency you step them not trough varying the current. The catch is that as the frequency grows the torque decreases to the point the motor stops stepping, the maximum step frequency varies with the motor model.

For a stepper to step the two coils (4 wires means 2 for each of the coils) mus be energized in a certain sequence, have a look here for a very good description http://www.stepperworld.com/Tutorials/pgBipolarTutorial.htm

Hope this helps there is a ton of theory, cheers.