A stepper motor is one that is typically used to move the shaft a
precise number of degrees per 'step'. It is typically controlled by a
pulse-drive mechanism (i.e., you don't just apply a voltage to it for it
to work, there must be some form of control circuitry to apply the right
number of pulses, of the right amplitude, at the right time). If you
had a stepper motor that was one degree per step, for example, and you
gave it the right number of pulses for 360 degrees, it would turn one
full rotation. These motors are obviously used a lot in industry for
precise motions (the last time I did any 'real' work with them was in
the early nineties, on a medical laser program).
Unlike most types of motors, where you just apply power and the motor
turns for as long as the power is applied, you apply pulses of power
to stepper motors and they rotate a small distance (like one degree
for pulse). They're used in applications where you want to be able to
do a known rotation, without feedback. One of their really common
applications has been in disk drives, where you can get a pulse to
correspond to a track.
The implementation is a little bit more complex than this, but that's
the basic idea.
Joseph J. Pfeiffer, Jr., Ph.D. Phone -- (505) 646-1605
Department of Computer Science FAX -- (505) 646-1002
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