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Name: Makomane
Status: Student
Grade: Other
Location: Outside U.S.
Country: South Africa
Date: March 2009

You can also see that the next logical step after "step 4" is to go back to the current flow shown in step 1. When this happens, the motor once again rotates ahead one step (it does NOT rotate backwards 3 steps!). If you continue to go through the 1-4 step sequence again and again, the motor will continue to rotate in steps, until you stop. The big advantage of a stepper motor, is that you can rotate it an EXACT number of rotations, simply by sending it the correct number of step sequences. So, for example, if you had a motor that rotates in 36° increments, and you wanted it to turn exactly 1.6 revolutions (16 steps), you simply send 16 of the above step sequences (that is, repeat steps 1 to 4, 4 times), then stop. The motor will then rotate one full revolution, then another 216° (0.6 of a revolution), then it will stop in this exact position.

The simplest stepper motors drive the hands in wrist watches. These motors have only one coil and each step is 180°, so the motor rotates 180° almost instantly, then stops for one second, then rotates another 180°, and so on. The motor is connected via gears to drive the hands.

More complex stepper motors have as many as 5 coils and very fine steps (1000 or more per revolution).


Bob Wilson


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