stepper

A stepper, or stepper motor, is a brushless electric motor that converts electrical pulses into precise angular motion. It moves in discrete steps and can hold a position without feedback in open-loop control. Steppers are widely used for accurate positioning, timing, and repeatability in automated equipment.

Construction relies on a rotor with teeth and stator windings arranged in phases. Energizing windings in a specific sequence advances the shaft in fixed increments. The step angle determines the rotation per input pulse. Common values are 1.8 degrees (200 steps per revolution) and 0.9 degrees (400 steps).

There are several types: permanent-magnet, variable-reluctance, and hybrid stepper motors, with hybrids being most common due to higher torque and resolution. Steppers can be driven in unipolar or bipolar configurations; modern drivers often use bipolar operation. Microstepping divides steps into smaller increments to smooth motion and reduce torque ripple.

Advantages include high torque at low speeds and simple open-loop control. Limitations include torque falling with speed, resonance and cogging, and potential missed steps under heavy load unless properly driven or used with feedback.

Applications include 3D printers, CNC machines, robotics, laboratory instruments, and precise positioning stages where feedback is unnecessary or cost-prohibitive.