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I am trying to control a 4 wire bipolar stepper with a PWM signal being output from a VEX cortex controller. I am planning on using 4 bipolar NEMA 17 12v steppers to drive a small remote controlled robot. (https://www.sparkfun.com/products/9238) I have found equipment to convert a 3 wire PWM signal to a (unipolar) 5-8 wire stepper output ( http://store.cunningturtle.com/collections/frontpage/products/radio-controlled-stepper-kit ), but nothing for 4 wire bipolar steppers. I am wondering if I would be better off looking for new motors or is there a way to control these motors easily with this controller.

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  • \$\begingroup\$ First, you need to decide if you're using bipolar or unipolar steppers. In the title you mention bipolar and in the text you mention both bipolar and unipolar. The two types steppers require different drive circuits. Also, it is not clear what you mean by '3 wire PWM signal' \$\endgroup\$ Commented Dec 3, 2013 at 19:08
  • \$\begingroup\$ I have no preference as to which type of stepper I use. Both types appear to be suitable as far as moving the robot is concerned. It is just a matter of which is easier to control (and how I would go about controlling it) I would be interested in knowing how to control both types of steppers in this situation. When I say "3 wire PWM signal" I am referring to a standard hobby servo input which uses 1 ground wire, 1 power wire and 1 PWM signal wire to control speed and direction. \$\endgroup\$
    – Carter
    Commented Dec 3, 2013 at 21:04
  • \$\begingroup\$ The controller you link is designed to control a unipolar motor, but the motor you link is a bipolar motor. Unfortunately, there is no easy way to make them work together. There are stepper motors that can be wired as either bipolar or unipolar. They will have 6 or 8 wires. I'd say your options are to find a different motor OR a different controller. Unless you're planning to build your own controller, this looks like a shopping question and is out of scope for this forum. \$\endgroup\$ Commented Dec 3, 2013 at 22:37

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You may need to build your own controller unless you can get the proper drive outputs from your controller. Generally, stepper motors are driven with step and direction signals as they allow very precise control over which direction the motor is rotating and precisely how far it turns. If you can't get access to the coil center taps, then you're probably going to have to either find a different motor or roll your own controller. It would not be very difficult to get an Arduino to read in the PWM pulses and drive a stepper or two with a motor driver shield.

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