[SOLVED] Stepper motor turning only in one direction, stalling in opposite direction

[Boloar]

Components in use for project: Arduino Mega --> StepStick --> 28BYJ-48 5V Stepper

The stepper is 5V but I am using it at 8V since the A4988 driver requires a minimum motor voltage of 8V. It's a 5-wire unipolar motor, but I opened up the cover on it and cut the trace connecting the 2 coils, so it should be operating as a 4-wire bipolar stepper.

I am testing it with the AccelStepper library for Arduino, running a program to make it turn one direction and then reverse every few seconds.

The issue: it turns fine in one direction, I can feel/hear/see it turning correctly, and then it simply stalls when it's supposed to turn in reverse. When attempting to reverse I can feel the pulsing/jerking of the motor coils seemingly out of step, while in the 'forward' direction it feels perfectly synchronized.

The driver should be fine to the best of my knowledge, as I hooked up some LEDs to the stepper drive pins to check if the pulses were coming out alright, and they seem to be in sequence just fine. While keeping the LEDs plugged in, I reconnected the motor one wire at a time, and the pulses kept coming in order ... until I plugged in the fourth wire of the motor. Then, the pulses for the 'reverse' direction seemed to be stalled, while still coming out alright for the 'forward' direction. I reconnected the stepper wires in all possible configurations, and the only result was that the stepper then turned in reverse, but stalled on forward motion instead.

I have no idea what could be wrong, and I don't have easy access to more stepper motors or drivers.
I managed to scrounge an old regular bipolar stepper from a printer ... same problem. It has to be the driver. As long as the stepper is NOT connected to the output, the stepping signals come out fine. If I connect the wires one by one, the signals still come out fine. But, as soon as I plug in the 4th wire of the stepper, it goes haywire.

I took a video - the stepper is supposed to go one direction for two seconds and reverse for 2 seconds. See the pattern of the LEDs flashing.

 

[barry]

It sure sounds like you're not connecting your motor properly.

 

[Boloar]

Trust me when I say, I wish that were the answer. And I would be *this* close to shooting myself (if I had a gun), if it somehow turned out to be the case.

I have two A4988 drivers on different spots my breadboard, and I've hooked the steppers up with short lengths of copper wire from an ethernet cable. I've checked the resistance of the phases (55ohms) and I've hooked up the 4 stepper wires in all 24 combinations to each driver, and the same problem persists.

It was working a month ago, then I put this project on hold for some other work, and now it's not working. I've ordered new stepper drivers, but using the LEDs on the stepper outputs show the signals coming out right. Everything works fine as long as at least one wire of the stepper is left unconnected.

HELP.

 

[barry]

Oh,so it WAS working? That's a pretty important bit of information, don't you think????? That means SOMETHING HAS FAILED!
You've got 3 choices: the motor, the driver, the Arduino. You've checked a second motor with the same results, so that kind of eliminates the motor as the problem. Since it works in the forward direction, that kind of says the Arduino is ok. That only leaves one last thing.

 

[Boloar]

I kind of already said it has to be the driver (albeit not very obviously), at the end of my first post.
What I fail to understand is WHAT, exactly, has failed, and how, since this setup was barely used before, and how it is affecting both independent drivers at the same time, and only when all 4 stepper wires are connected.

I drove the steppers back and forth just fine with 4 direct wires from the Arduino, so yes, the Arduino is fine and so are the steppers. Still waiting on my replacement drivers, but in the meantime it would be nice to imagine that this issue can be fixed, and perhaps hypothesize a cause so that the new ones don't suffer the same fate. I'm not made of money, and these things are unnecessarily expensive where I am.

 

[barry]

What you said was: "The driver should be fine", and, "I have no idea what could be wrong."

What do you mean by "it is affecting both independent drivers at the same time." WHAT independent drivers?

My guess is that even though it seems to be working in the forward direction, you may have a defective MOSFET on one of the driver channels. It would be VERY useful if you could look at some signals with an oscilloscope.

 

[Boloar]

What I said was:
"The driver should be fine to the best of my knowledge", and in the second-to-last paragraph I noted "It has to be the driver". Yes I did say I have no idea what could be wrong, because that's true. I have no idea what has failed or why.

"Independent drivers" as in my second post, where I said"I have two A4988 drivers on different spots my breadboard ... and the same problem persists" (I should have added "the problem persists for both drivers". Fine, my lack of information, sorry, let's move on.)

Unfortunately I don't have an O-scope - rather out of my budget. If it is a damaged MOSFET, hopefully the new set of drivers don't suffer the same fate. I have no idea why that would have happened.

 

[Boloar]

Currently ticked the **** off, after re-wiring at a different position on the breadboard ALL IS SUDDENLY WELL.
I hate to stereotype, but **** Indian hobby electronics suppliers.