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Thread: 6 wire stepper motor - only need 4 wires to run?

  1. #1

    Lightbulb 6 wire stepper motor - only need 4 wires to run?

    I'm using a BS2e module, a Board of Education Development Board - Serial Version, and a 6 wire- 9.5 V stepper motor. The weird thing is I only connect the 4 phases only, without the 2 RED wires connected (Power wires) the motor still running. My question is do I need to connect all 6 wires? And does the torque of the motor decrease because of the RED wires not connected?
    Here is the diagram I connect for the 4 phases:

    ' P4 -> ULN2003.1, ULN2003.16 -> Phase 1 (Black)
    ' P5 -> ULN2003.2, ULN2003.15 -> Phase 2 (Orange)
    ' P6 -> ULN2003.3, ULN2003.14 -> Phase 3 (Brown)
    ' P7 -> ULN2003.4, ULN2003.13 -> Phase 4 (Yellow)

    Any help is appreciated. Thanks in advance

  2. #2

    Default Re: 6 wire stepper motor - only need 4 wires to run?

    Guy 20 San Jose, welcome to the forum!

    Now, there's something about your explanation that just doesn't make sense. The ULN2003 is an open-collector driver. It does not have any current-sourcing capability. Given your description, the motor should not run at all, since it's not being sourced with current. Are you sure you've provided an accurate description? Can you provide a full schematic?

    Short answer: yes, the red wires need to be connected to a positive supply.


  3. #3

    Default Re: 6 wire stepper motor - only need 4 wires to run?

    I agree with Phil on his point and I am going to expand his point it a little. The ULN2003 is an open-collector driver, which sinks to ground. This means the ULN2003 also needs it's ground, if you didn't connect it.
    William Stefan
    The Basic Stamp Nut with some Spin

  4. #4

    Lightbulb Re: 6 wire stepper motor - only need 4 wires to run?

    Like I said, only 4 phases are connected. As soon as I power up the Parallax board, the stepper motor run. Please prefer to the picture.
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  5. #5

    Default Re: 6 wire stepper motor - only need 4 wires to run?


    You did not describe your circuit accurately in the first post. The photo does not show a ULN2003, and the motor leads are connected directly to the BASIC Stamp. That changes everything, because the Stamp is sourcing current to the motor directly. That is a poor way to drive a stepper, because the coils are being energized in series, and you're effectively driving a 19V motor with 5V. I would recommend using the ULN2003 and connecting the red wires to a proper motor supply voltage.


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