The stepper motor is a motor with precise positioning, so that each electric impulse of the power signal corresponds to a fixed angle of rotation.
The stator is made of four poles and the rotor and a permanent magnet and to understand the operation of this motor, we will consider that when energizing the windings, pole 1 is a south magnetic pole and pole 3, a north pole.
Under these conditions, the magnet will move until it is aligned with that field. If, at the next pulse, pole 2 and south and pole 4 and north, the rotor (magnet) will perform another 90 ° turn, taking another step.
This synchronization of steps is possible because the rotor is also made by poles, but in an odd number, not even, like the stator; thus the stator and rotor poles will never be aligned at the same instant.
Then the pitch angle will be determined by the number of poles of the stator and the rotor, usually between 1.8 ° and 30 °. Sequences may be used to drive a stepper motor: full step and half step.