[SOLVED] Pololu pulsing issue

This is a pretty strange problem, but I'll try to explain as best I can. I'm sure that the root of the problem is my solder job, but I'm just curious if I can actually salvage the Pololu driver or if I need to use a new one.

Everything seems good at first when I connect to the printer and test each Pololu driver. One driver has issues, however. A few (maybe 10?) seconds after a successful test, it will start making this pulsing noise. It's not actually turning the motor, but if I touch the motor I can feel it shake on every other pulse. The pulsing is perfectly even from what I can tell, slightly over 2 pulses per second. This pulsing will continue until take away power from the arduino. If I do a test after the pulsing begins, the motor only moves on every other pulse (the same pulse where I could feel shaking earlier). In fact, I did a full print of a shot glass last night using this "halfway working" driver on the Z-axis. It looks like it is about half as tall as it should be, but it extruded the full amount of plastic so it's very dense/smooshed vertically.

Anyone ever had/heard of this problem before? At one point during soldering I accidentally touched the iron (very briefly) to a component on the board, so I'm assuming that's the problem, but I can't help but wonder if it might be caused by something fixable. I'm not very electronically savvy, but I thought that generally when electronics fail they fail catastrophically, not halfway like this.

Edited 1 time(s). Last edit at 06/14/2011 10:43AM by unicoder.

It sounds to me that the driver is overheating and going into protection then it cools and starts and then overheats....................................... Microstepping drivers always have current going to the motor even when stopped, it is what holds the motor between steps. If the driver is to hot to touch at the point when it starts to pulse you know your issue.

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Ok, but that doesn't explain why it pulses when I'm not sending any commands does it? Also, what would be the fix if that were the case? I already put a heatsink on the driver.

Yes it can overheat while stationary as that is when maximum current flows. You should be able to tell though as it will get get far too hot to touch.

If so turning the current down will stop it overheating provided you get enough torque.

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[www.hydraraptor.blogspot.com]

Wow. Stellar advice as always, guys. Thanks!
I didn't check for heat, but I assume that must have been the problem. I just went and turned the potentiometer about a full turn counter-clockwise and tested it. It wasn't getting enough power, so I turned it a half-turn back and BINGO! No more problems. I'm shocked that my ghetto soldering actually worked.
Thanks again guys! I've never been disappointed when I turn to the RepRap forums for help.

Looks like i have same problem. Is it possible, that crassh of some axis induce overheating and then pulsing? Because my pololus are not on maximum setting and i use small (6*5mm) heatsinks + fan....

No not really. Stepper motors take more or less constant power whether they are moving or not due to the constant current drive.

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[www.hydraraptor.blogspot.com]

Hey guys I am having a similar problem with my stepper motors, all seem to pulse or jerk when they move and you can hear them making a pulsing like noise when they aren't moving they all do this in sync, I have turned all of the pots almost all the way down and they still are pulsing as well as the led for the heat also pulse in sync with the motors. This problem just developed the other day out of the blue.
I am running a arduino mega 2560 ramps 1.4 and the marlin fw

As I came to this thread while searching for a solution to a similar symptom pulsing problem.
I'd thought I add my solution to a slightly different problem with similar symptoms:

Case:
When i first connected my motors it started turning but not consistently and stopped turning
and started vibrating. This was on RAMPS electronics with makerbot stepper motors.

Solution:
Big case of RTFM
I connected the steppers to the RAMPS assuming that the two loops of the motors needed to
be connected to A & B.
With the numbering of the ramps:
I did this:
1A -> loop1
1B -> loop2
2B -> loop2
2A -> loop1

This is the correct wiring:

1A -> loop1
1B -> loop1
2B -> loop2
2A -> loop2

Really obvious when you think about it but it had me baffled for at least a few hours.

Best Regards

Evert