Stepper Motor Safety

Discussion in 'The Projects Forum' started by cremaster, Sep 6, 2010.

  1. cremaster

    Thread Starter New Member

    Jun 30, 2010
    19
    0
    Ive got two 6 wire stepper motors affixed to the knobs of an etch a sketch. I have connected the two common power wires and am controlling the motors via the ULN2003 with my parallel port. The motors are PF35T-48L4s and some information about them is here: (including data sheet)

    http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_171601_-1

    I believe these are rated at 7V, (it says 12V at the top, im not sure why). At 7 volts they struggle heartily with the knob of the etch a sketch and cannot make the cut. At 9 volts they work reliably, able to turn the knobs with success.

    I tried 9V hesitantly, as I was not sure what would happen. Is it dangerous to use the motor at 2V higher than its rated? (It may be rated at 12V after all, the above page is quite ambiguous).

    At any rate, the does heat up, but not excessively.
     
  2. sceadwian

    New Member

    Jun 1, 2009
    499
    37
    Stepper motors aren't really rated for a particular voltage (excluding the limits of their insulation) basically as long as it's not overheating badly you can apply as much voltage as needed. If you're going to apply much higher voltage than it says on the case then you'll probably want to monitor the temperature somehow, adding fans/heatsinks might not be a bad idea either that will increase the amount of power you can apply.
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Those motors are at least supposed to be 7 volt motors. What does your driver circuit look like?
     
  4. cremaster

    Thread Starter New Member

    Jun 30, 2010
    19
    0
    My circuit is exactly as pictured here:
    http://electronics-diy.com/electronics/stepper_motors.php

    I understand the ULN2003 can handle a maximum of 500mA, so I guess I need to be wary that the motor doesn't draw any more than this. Is this a problem necessarily, if I heatsink the ICs? Would they melt if I went way over this limit? The ULN2003s were not hot at all to the touch when the motor was running at 9 Volts.
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    The motor is spec'ed at 7 volts with 20 ohm windings. That should be no more than 350 ma/winding. If things run cool at nine volts, why not? That's still under the top current draw of the ULN2003.
     
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