STH-39D236-02 Stepper Motor?

Discussion in 'General Electronics Chat' started by tracecom, Jun 10, 2013.

  1. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    I have a stepper motor with six wires: two beige, one yellow, one red, one blue, and one white.

    It is marked as follows.

    STH-39D236-02‎
    1.8 DEG/STEP 30Ω

    So, I know it's 1.8° per step, and I assume its unipolar. Does anyone know the operating voltage or any other specifications?

    Thanks.
     
  2. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    The two beige wires are the common wires (centre taps of the unipolar windings).

    The 39 is the motor size, that means 39mm or NMEA size 14. A small motor!

    Google for motors of the same package size, see their ohms and maps which will tell you the wattage per winding. A size 14 motor is somewhere around 2W per winding, maybe 2.5W, depending on motor brand and length.

    Then measure the ohms of a unipolar half winding from beige to any wire. Once you know winding watts and ohms you can calc the volts and amps of that winding using ohms law.
     
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  3. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    The motor windings measure 32Ω. The scanner that it came from has a power supply that produces 5V, 12V, and +/- 15V. I think that the motor must be for 12V, which would mean the current per winding is 375mA, and the wattage is 4.5W. Given that the motor is about 35mm long, I think that's reasonable.

    For the benefit of anyone who lands on this thread in the future, the winding wire color order is blue, red, yellow, white for CW rotation.
     
  4. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    4.5W sounds a bit much per winding on a size 14 motor? That would be an average 4.5W * 1.414 (if microstepped) and 6.4W sounds a lot for that package. I would think about 50-60% of that power is more likely.

    The stepper driver chips would be supplied with 12v, but they limit winding current as their main operating principle, so the operating voltage and current in each winding would likely be less than 12v and less than 375mA.
     
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