Stepper Motors
Stepper motors are synchronous, brushless electric motors that move in increments rather than turning smoothly, like conventional motors. Stepper motors have the capability of dividing a full rotation into a large number of steps, thus making them useful when something must be positioned precisely or rotated by an exact angle.
Stepper motors are essentially electric motors without commutators, which convert the electric current from DC to AC. All of the commutation handled externally by the motor controller can be stepped at audio frequencies, allowing them to spin quite quickly and be started and stopped precisely at controlled orientations.
The electromagnetic coils in a stepper motor may have either bipolar or unipolar arrangement. While bipolar motors have only two coils that have current flowing in opposite directions, unipolar motors have four separate coils, with current flowing in only one direction. Bipolar motors can switch between supply voltage, ground, and unconnected. Unipolar controllers, on the other hand, can only connect or disconnect a cable because the voltage is already hard wired.
Typically, stepper motors are small in size and used in positioning systems, in addition to many other uses. Stepper motors are commonly found in floppy disk drives, flatbed scanners, fluid control systems, printers, plotters, watches, and more.