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I'm planning to build a simple XY plotter, and have been looking at the possibility of using a pair of small 5V 4-phase steppers to provide the movement. In my research, I've often seen stepper driver boards advertised, ranging from very big and expensive, through to quite small and cheap. Some of them actually look like little more than a darlington array on a PCB.

Do I really need one of those external driver boards, or can I control the steppers directly from my Arduino?

  • Do you have the datasheet for the steppers? What would be the DC resistance of the coils? You probably need a driver anyway, but sizing has to do with the power the stepper draws. I estimate you can only drive max 125mW from an Arduino directly, probably even less. – jippie Feb 21 '14 at 13:26
  • No part number, unfortunately, and minimal info from the supplier. I figured the current draw was likely to be too much, but thought it was worth asking anyway. – Peter Bloomfield Feb 21 '14 at 15:21
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Generally, stepper motors cannot be controlled by an Arduino pin. They have a current draw of over the 20mA any single pin can supply.

Kickback is also a problem. Because the motors have moving magnetic parts inside, they will continue to generate electricity after power has been cut. this will almost certainly cause enough negative voltage that is enough to fry your Arduino.

A solution is to use a motor driver chip or shield. This one is a good example. These have transistor based chips that can drive enough current to power a motor, and diodes to mitigate the kickback from the motors.

  • 2
    You do not need moving components to produce inductive kickback. All you need is inductance, which requires no moving parts at all. – Connor Wolf Mar 2 '14 at 7:13

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