Unipolar stepper motor

Discussion in 'General Electronics Chat' started by nerdegutta, Nov 15, 2014.

  1. nerdegutta

    Thread Starter Moderator

    Dec 15, 2009
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    Is this a unipolar stepper motor? I couldn't find any datasheets online. It's from an old Star NX 1000 printer.

    The wires has these colors: Blue, Brown, White, Red and Yellow.

    If it is unipolar, and I don't connect the common wire, can I then use it as a bipolar?
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You should be able to if the windings match, that seems a little coarse for steps?
    Max.
     
  3. nerdegutta

    Thread Starter Moderator

    Dec 15, 2009
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    Coarse, you mean big steps, since it's 7,5 degrees for each step?
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The 'normal' full step is 1.8°/step or 200 steps/rev.
    Max.
     
  5. nerdegutta

    Thread Starter Moderator

    Dec 15, 2009
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    I'm planning of using this motor on a "proof of concept" or a test run application. Eventually I want 0.9 deg step motor.

    Thanks!
     
  6. RichardO

    Well-Known Member

    May 4, 2013
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    Since your stepper motor only has 4 wires, it is a bipolar stepper. Aa unipolar stepper has at least 5 wires: 4 phases and a common. Some unipolar steppers have 2 commons instead of 1 for a total of 6 wires.

    I have seen some stepper motors that bring out leads from the ends of all 4 of the windings -- 8 wires. These do not seem too common. That is a good thing because figuring out the wiring without a data sheet would be tricky.

    You can use a unipolar stepper as a bipolar stepper by leaving the common(s) unconnected but the torque ratings will be slightly less than an a bipolar-only stepper drawing the same amount of power. I am not sure but I think the maximum step rate of a unipolar is also poorer than an equivalent bipolar stepper.
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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    He shows 5 wires?
    Max.
     
  8. RichardO

    Well-Known Member

    May 4, 2013
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    Oops. "Blue, Brown, White, Red and Yellow." 1,2,3,4,5. 1,2,3,4,5. 1,2,3,4,5....
     
  9. RichardO

    Well-Known Member

    May 4, 2013
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    I realized after posting the previous reply that I had an oversight.

    A 5-lead stepper may not give even spaced steps if the bipolar drive voltage is not symmetrical. For example, the steps could be 6 degrees and 9 degrees on your 7.5 degree per step motor. The larger steps may decrease torque and reduce the maximum step rate.
     
  10. nerdegutta

    Thread Starter Moderator

    Dec 15, 2009
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    The project is put on the shelf for a while. Some other projects is stealing my time.

    Thanks for the relies!
     
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