Stepper motors are brushless DC electrical motors that move a full rotation of equal steps. The position of the motor is controlled without the use of a feedback system (open-loop system). This makes stepper motors relatively inexpensive and popular for robotics, 3-D printers, and CNC-type applications.

The following is a crude diagram of the internal workings of a stepper motor:

By turning on and off the coils A and B in sequence, the Permanent Magnet (which is attached to the shaft of the motor) is spun. Precise steps are used, allowing precise control of the motor, as the number of steps may be controlled easily.

Stepper motors tend to be heavier and bulkier than other types of small motors.

The following photo shows a typical stepper motor used in a 3-D printer: