Stepper Motor
•A stepper motor is a widely used device that translates electrical pulses into mechanical movement•The stepper motor is used for position control in applications such as disk drivers, dot matrix printers, and robotics, etc.
•Every stepper motor has a permanent magnet rotor (also called the shaft) surrounded by a stator .
•The most common stepper motors have four stator windings that are paired with a center-tapped common.
•This type of stepper motor is commonly referred to as a four-phase stepper motor
•The center tap allows a change of current direction in each of two coils when a winding is grounded, thereby resulting in a polarity change of the stator.
•The stepper motor discussed here has a total of 6 leads, 4 leads representing the four stator windings ,2 commons for the center tapped leads.
•As the sequence of power is applied to each stator winding, the rotor will rotate.
•The step angle is the minimum degree of rotation associated with a angles for various motors
•The step per revolution is the total number of steps needed to rotate one complete rotation or 360 degrees.
•The relation between RPM (revolutions per minute), steps per revolution, and steps per second is as follow
•Steps/Sec = RPM x Steps per revolution / 60
•After completing every four steps, the rotor moves only one tooth pitch
•The smaller the step angle, the more teeth the motor passes
•ex. In a stepper motor with 200 steps per revolution, its rotor has 50 teeth since 4 x 50 = 200 steps are needed .
Interfacing
•To allow for finer resolutions, all stepper motors allow what is called an 8-step switching sequence.
•It’s also called half-stepping, since each step is half of the normal step angle
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