Bipolar vs. unipolar stepper drive

Discussion in 'The Projects Forum' started by rdoty, Mar 3, 2010.

  1. rdoty

    Thread Starter New Member

    Feb 24, 2010
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    I'm putting together a stepper system based on the ST L6208 two phase bipolar driver. Can I drive a unipolar 6-wire motor with this driver and if so how do I configure the windings?
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Yes, you can drive unipolar stepper motors as bipolar. You can't always do the reverse; but some motors have eight leads.

    If you are driving a unipolar as a bipolar motor, you simply don't use the winding center taps. The voltage requirement doubles.

    The winding center taps are frequently red and green; the winding "end" colors are frequently yellow, orange (being one pair), black, and brown (being the other pair).
    Green is the center tap for black/brown.
    Red is the center tap for yellow/orange.

    If your wire colors are different, consult your motor's datasheet.
     
  3. shortbus

    AAC Fanatic!

    Sep 30, 2009
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  4. rdoty

    Thread Starter New Member

    Feb 24, 2010
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    Thanks for the clarification. I'm actually working with a bipolar motor but had some unipolar motors laying around and was curious.

    One of the motors I have is listed as Bipolar (series) and has six leads. Obviously one of the leads is a center tap but my question is: presuming you connect the two end leads to the driver output what do you do with the center lead and what is it's purpose?
     
  5. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Like I stated before go to the Jones site and read, it will explain it all.

    A 6 lead motor is a 'hybrid' it can be wired as a bipolar or a unipolar. The center taps are just taped on the end to insulate them when using as a bipolar.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Unipolar steppers are easier to drive because the center tap supplies the +V, and the individual coils are energized by grounding one of the coil ends in a sequential fashion (single stepping). This can be done by using four MOSFETs or Darlington transistors.

    With a bipolar stepper motor, you need to reverse the direction of current through the coil. Therefore, each coil must be controlled by an H-bridge configuration; you need two complete H-bridges to drive a bipolar stepper motor.
     
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