Stepper Motor

A stepper motor, also called a step motor or stepping motor, is a brushless DC electric motor that rotates in a series of small, discrete angular steps rather than turning continuously, and because each step is a known, fixed angle the motor can be positioned accurately without feedback sensors. It can be commanded to hold at any single step position or driven into continuous rotation by issuing step commands in rapid succession, and its resolution, torque, speed and size vary by design and application. A related, larger class of machine, the switched reluctance motor, uses the same basic stepping idea but with fewer poles and closed loop commutation rather than the open loop stepping control a true stepper motor uses. Because it can be positioned precisely without sensors, the stepper motor is a standard choice wherever a machine needs exact, repeatable motion at modest cost, from printers and disk drives to camera lenses and small robotics.