Introduction

Steppers motors are basicly a type of motor which can be controlled to a high degree of accuracy from a digital logic curucit or computer. They are used in many common computer devices such as printers, floppy drives, and older hard drives. So it is quite easy to get them cheaply. I pulled the stepper motors for the CPM out of an old HP dot matrix printer that my University was no longer using. There are many things you can do with these useful devices. Search the web or check out some of the links below for ideas.

Stepper motors are however harder to use than regular DC motors. There are two main types of stepper motor Uni-polar and Bi-polar. The ones I have used are Uni-polar. A Uni-polar motor as three or more sets of coils. Turning on these sets of coils in the right pattern cause the motor to move. Each motor has a step degree. This is the number of degrees that the shaft of the motor will turn when you switch it from a set of coils to the next. Bi-polar motors are similar except that they also use changing coil polarity to move the shaft. It is easy to test if you have a Uni-polar motor. There should be sets of three wires. The restance across two of the wires will be the sum of the resistance between the third wire and the other two. Between the sets of wires there should be no connection.

         C1
         |
A1---/\/\/\/\/\---B1


A2---/\/\/\/\/\---B2
         |
       	 C2
Resistance from A to B = resistance from A to C + resistance from C to B

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