stepper motor - introduction

A stepper motor is a electromechanical device which converts electrical pulses into discrete mechanical movements. The shaft or spindle of a stepper motor rotates in discrete step increments when electrical command pulses are applied to it in the proper sequence. Stepper motors enable precise positioning without needing sensors to measure motor position.

Advantages

• The rotation angle of the motor is proportional to the input pulse.
• The motor has full torque at standstill(if the winding are energized).
• Precise positioning and repeatability of movement since good stepper motors have an accuracy of 3-5% of a step and this error is non cumulative from one step to the next.
• Excellent response to starting/stopping/reversing.
• Very reliable since there are no contact brushes in the motor. Therefore the life of the motor is simply dependent on the life of the bearing.
• The motors response to digital input pulses provides open-loop control, making the motor simpler and less costly to control.
• It is possible to achieve very low speed synchronous rotation with a load that is directly coupled to the shaft.
• A wide range of rotational speeds can be realized as the speed is proportional to the frequency of the input pulses.
  

Disadvantages

• Resonances can occur if not properly controlled.
• Not easy to operate at extremely high speeds.
• More complex to control than DC motors.
• Consume precious battery current even when not moving.