Stepper motor just vibrates and gets hot

AI Thread Summary
The user is experiencing issues with a 5-wire unipolar J835L stepper motor that vibrates and overheats when connected to a ULN2003A driver. The motor specifications include a 120 Ohm resistance and a stepping angle of 7.5 degrees. Initial attempts to drive the motor involved a 0.1 ms delay between steps, which was suggested to be too fast for proper operation. After increasing the delay to 500 ms, the motor functioned correctly. The solution highlights the importance of timing in stepper motor control.
neergmas
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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:

293yi5j.jpg


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
 

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That delay of 0.1 mS seems too fast.

Just for a test, try 500 mS.
 
Could be a problem with timings or the run sequence. It could be going forward, then next step makes it go backwards.
 
vk6kro said:
That delay of 0.1 mS seems too fast.

Just for a test, try 500 mS.

That was it! Thank you :)
 
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