A Stepper Motor is a brushless, synchronous DC motor which divides a full rotation into a number of steps.
For detailed information on working, types and stepping modes, refer the article on Stepper Motors. Here the operation of a unipolar Stepper motor with PIC18F4550 microcontroller has been explained.
As stated earlier, a Stepper motor rotates step by step. Each stepper motor has a defined step angle which is the minimum degree of rotation in a single step. This step angle depends on the internal construction of the motor. If a stepper motor has a step angle of 1.8°, then it would need 200 steps for a complete circular rotation. For control operation, construction and stepping modes, refer the article on Stepper Motors.
The stepper motor consists of a Rotor and four Stators. The stators are rounded with center-taped winding. The center-taped terminals are known Common terminals. Thus a unipolar stepper motor consists of total 6 wire-ends (four wires for coils and two for the common ends).