Steppers

Steppers, or stepper motors, are a class of brushless DC motors that move in discrete angular increments called steps. They convert digital input pulses into precise mechanical rotation, enabling controlled positioning without feedback in many open-loop systems. A stepper motor typically consists of a rotor with permanent magnets or a toothed rotor, and a stator containing multiple windings arranged in phases. By energizing the windings in a specific sequence, the magnetic field rotates in steps, producing angular motion. Common step angles are 1.8 degrees (200 steps per revolution) and 0.9 degrees (400 steps), with microstepping offering finer resolution.

There are several motor fashions: permanent magnet (PM) steppers, variable reluctance (VR) steppers, and hybrid steppers. PM steppers use magnets on the rotor and have good torque at low speeds but lower detent-free smoothness. VR steppers have a windings-driven reluctance rotor and are simple but can have uneven torque. Hybrid steppers combine a toothed rotor with permanent magnets, offering higher torque and higher step counts, making them the most widely used in precision applications.

Driving and control: Step sequences include full-step, half-step, and microstepping. Stepper drivers convert input steps into a current waveform that energizes motor windings. Open-loop control works well for many applications, while closed-loop or servo-like systems add feedback to correct missed steps and improve reliability at higher speeds.

Applications include 3D printers, CNC machines, robotics, cameras, medical devices, and automation. Advantages include precise positioning, high holding torque at rest, and simple drive electronics; drawbacks include torque ripple, resonance at certain speeds, and reduced efficiency at high speeds.