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

Hello
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
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Comments

  • 5 Comments sorted by Votes Date Added
  • edited February 2011 Posts: 0Vote Up0Vote Down
    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.

    -Phil
    “Impossible is just a big word thrown around by small men who find it easier to live in the world they’ve been given than to explore the power they have to change it. Impossible is not a fact. It’s an opinion. Impossible is not a declaration. It’s a dare. Impossible is potential. Impossible is temporary. Impossible is nothing.” –Muhammad Ali
  • edited February 2011 Posts: 0Vote Up0Vote Down
    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
  • edited February 2011 Posts: 13Vote Up0Vote Down
    Phil
    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.
    Thanks
    1024 x 768 - 84K
  • edited February 2011 Posts: 0Vote Up0Vote Down
    Guy20,

    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.

    -Phil
    “Impossible is just a big word thrown around by small men who find it easier to live in the world they’ve been given than to explore the power they have to change it. Impossible is not a fact. It’s an opinion. Impossible is not a declaration. It’s a dare. Impossible is potential. Impossible is temporary. Impossible is nothing.” –Muhammad Ali
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