stepper motor

A stepper motor is a motor that moves in tiny, exact clicks instead of a smooth continuous spin. A common stepper turns one fixed amount per pulse, so a typical 200-step model rotates exactly one full turn after 200 pulses — no more, no less. Each pulse of electricity advances it by one fixed notch, so you can position it precisely just by counting pulses, without any sensor watching where the shaft actually is. This is why steppers run the print heads of 3D printers, the trays of optical drives, and the axes of small desktop machines.

Inside, the motor's ring of coils is energized in a set sequence, and a toothed magnetic rotor snaps to line up with whichever coils are switched on. Switch them in order and the rotor steps around, one detent at a time, like the second hand of a ticking clock. Even when standing still and powered, it firmly resists being pushed off its spot — a useful property called holding torque that locks a load in place. To smooth out the steps and reach in-between positions, drivers use microstepping, blending the current across coils so the rotor settles partway between full steps; this gives finer motion and quieter running.

The big appeal is open-loop control: precise positioning with no feedback hardware, which keeps things cheap and simple. The big catch is the flip side of the same coin — if the load is too heavy or the motor is told to move too fast, it can quietly skip steps, and because nothing is watching, the controller never finds out it has fallen behind. Steppers also run warm and lose torque as they speed up, so they shine at low-to-medium speeds where dead-reckoning precision matters more than raw power or efficiency.