I have a bit of an odd question: Why would my A4988 based stepper controllers overheat almost immediately even when turned down to absolute minimum power?
A few more details for you - I’m re-purposing an old Sanguinololu v1.3a controller to a printer that only uses one axis. I’ve got it wired in to the single stepper and single endstop, and I’ve removed all other driver chips, so all it can do is control the one axis. And it does. Very well. But the stepper driver heats up instantly, even if not put under load, and will go into thermal shutdown after about fifteen to thirty seconds even with the power turned all the way down.
Is it doing this because I only have one stepper driver in place? Or is there something stupid simple that I’m missing?
Make sure the thermister for your hotend is working properly. Thermal shutdown is a result of your malfunction of the hotend control. Not you stepper motor controller
What @Mark_Rehorst said : Check the reference voltage with a voltmeter. I’ve used A4988’s, DRV8825’s and SD6128’s, and I can make them all overheat pretty quickly if I don’t have the voltage set correctly.
http://reprap.org/wiki/Pololu_stepper_driver_board#Tuning_motor_current
No, it’s really at min current, measuring the test points confirms that.
@Pulse_motor_generato I’m talking about thermal shutdown of the stepper driver, not the machine as a whole.
Look up the stepper motor volt settings for that stepper motor …if the volt settings are correct. That stepper driver is faulty. Most of the stepper drivers are made in china. I am not a big fan of that…they use alot of cheap components. Honestly i would spend a few more $$ and get a rambo mini or a Ramba …the parts on those motherboards are way easy to set up. And best of all you dont need to mess with the stepper drivers. Its all controlled by the firmware
Does it have a heatsink? Should not matter, but I would think the stepper driver may be bad. I’d swap it out wth another to verify.
I’ve tried it with three total previously known good stepper drivers, same behavior for all three.
Then it has to be something with the board.
Is the driver orientation correct? I suppose it would be if the axis works at all.
I believe it is, yes. If it were reversed it shouldn’t work, should it? It does properly drive the stepper, it just overheats very very quickly even with the current turned all the way down.
What kind of motor do you have hooked up? Like size, model, current and millihenry values.
It’s a 68 Oz. in. Wantai 0.9 degree NEMA 23 rated for up to 1.7A and the datasheet says it’s 2.8mH/phase. This specific motor was previously used as an extruder motor in another printer until about a month ago, and it worked without issue there. The electronics (including stepper drivers) were also the controller in that same printer until about two months ago, and they’ve spent the interim in an anti-static bag.
The only difference from how this motor and controller were used before is that the controller is only driving one stepper instead of four and all unused axes have had their drivers removed.
Confusingly, I seem to have fixed it. I changed the driver out many, many times; poked around in the firmware a bit; and ultimately unplugged the stepper, tested the connector (which was fine) and reconnected it.
While doing that last step, I noticed the stepper cable had gotten wrapped around an aluminum extrusion a couple times somehow, so I unwound it before plugging it back in. And then the overheating went away.
The only thing I can think is the loop set up an inductance on the line that kept the voltage high through the driver and made it overheat.
What a weird situation… But at least it all seems fine now.
@Stephen_Baird I’ve actually seen that phenomenon happen a few times with medical equipment power cords, elevated currents, which lowered reference ground readings. Weird, but can actually happen in real life.