Stepper motor, with torque the wrong direction

Forum 2005-2010 (read only) Hardware Troubleshooting
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I got a stepper motor working, it got 6 wires, two of them positive, and the rest negative.

When setting the pins 8 9 10 11 high and low in that order, it makes it go one way, opposite order the opposite way (dooh), but my problem is that it got no torque at all. Or it got torque, but only in the opposite direction of what it should have.

The motor is connected to a little gear, which is connected to a belt with a sledge on. It is VERY easy to stop it moving, and it can just exactly make it move, but when I try to push the sledge in the same direction it is moving, trying to force it to go slower, the motor is very strong.

The motor is connected something like this

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I am just using an external 12V power supply to drive it, and a ULN2803AG as driver.

Lastly I also tried to use the servo library, but can't get the motor to move more than one step, no matter how many steps I put in.

What can I have done wrong? Misunderstood how the motor should be wired maybe? Looked at the board in the scanner I got the parts from, and it got the two positive connected on the board, with a large diode in front, pointing at the pins, so that should be positive.

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Misunderstood how the motor should be wired maybe?

Yes.

It looks like your motor has a centre tap on each coil. This can be used if you want to wire the coils in parallel. If you want them in series leave them un connected. The way you have it wired you can't possibly reverse the current in the motor because of the centre taps all being connected to +5V.
Have a look at:-
http://www.thebox.myzen.co.uk/Workshop/Motors_4.html

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Hmm, I wonder they made it work in the scanner.

I am 100% sure that both positive was connected together, and that it was the plus coming in there.

How can I do it without connecting the two together? I tried to experiment a bit, but only two of the four wires. Or is it like it will then be the opposite?

So if it is set A and B, and common on set A is plus, then common on set B is negative, to make the two work together instead of only one pulling the motor round?

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It depends on if you have a bipolar stepping motor or a unipolar stepping motor.
That schematic was made for a unipolar motor, if you got it out of a scanner it is likely that you have a bipolar motor.

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