This project allows you to control the speed, direc-tion, and step size of a unipolar four-phase step-per motor. The controller is capable of handling motor winding currents of up to 1.25 amps per phase and it operates from a single supply voltage of 6-30 volts DC.
If you are interested in robotics, motion control, or just want to learn about stepper motors, then
you should try building this versatile stepper motor controller.
Source: Electronics Lab