Stepper motor just vibrates and gets hot

[neergmas]

I have a 5-wire unipolar J835L. I have not been able to find a data sheet on it, but I have found this diagram:

also, the motor has the following information printed on its label:

Uni-Polar, Bi-Filar
120 Ohms
7.5° per step or 48 full steps per revolution
JARL J835L PM 24P

I have connected a ULN2003A ("focus.ti.com/lit/ds/symlink/uln2003a.pdf"[/URL]) between my uC and the motor like this:

[ATTACH=full]130959[/ATTACH]

where:
B = blue wire
P = purple wire
Y = yellow wire
O = orange wire
W = white wire

I have tried driving the circuit in these two orders:

Step POBY and PYBO
1 1000 1000
2 0100 0100
3 0010 0010
4 0001 0001
5 1000 1000
. . .
. . .

Where 1 has been verified to be 10v and 0 is 0v. I set each step and then wait for .1ms. The motor then just vibrates. Can anyone give me a pointer?

Thanks!
Sam

 

[vk6kro]

That delay of 0.1 mS seems too fast.

Just for a test, try 500 mS.

 

[waht]

Could be a problem with timings or the run sequence. It could be going forward, then next step makes it go backwards.

 

[neergmas]

That delay of 0.1 mS seems too fast.

Just for a test, try 500 mS.

That was it! Thank you :)