Megatronics v3 and Stepstick A4988 problem

I recently bought a prusa i3 kit from reprapword.com.
After getting everything set up i started calibrating.
All the motors where turning and it looked like everything was fine.

After a while tho some of the motors stopped turning and at this point non of them are.
I can still power the extruder and the heating bed and all the leds are responding so i don't think the megatronic its self is broken.
I am however thinking i may have burnt out the A4988 stepper drivers, i forgot to put on the heatsinks.
Properly not a real smart move.

So is there a way to check if the stepper drivers are really burnt out or if the problem is with the megatronics v3?

Normally the A4988 have some protection which should help to avoid killing them... but anyhow:

The easiest way to check if something is broken... change one hardware piece at a time and test again. The cheapest (and most likely damaged) part is the stepper driver. But before buying (and paying for "lessons learned") a new driver you should check the output current (by checking the contol voltage on the stepper driver).
Details for that are explained here:

[reprap.org]

So all the best and fingers crossed for the damage inspection!

Lutjanus

Hello, I am new on this forum but I hope you will able to help me.

I also have problem with A4988. I was running two Z mottors in series and they were working fine for a couple of minutes. Then both just started vibrating. I checked voltage on output pins when motors were iddle and there are 3 pins with over 12 volts and single pin with only 2.8V. The current on this pin is also much lower. Has anybody encountered similar problem and is it possible that A4988 just burned?

I tested this stepstick with single motor earlier and it was working pretty well.

Sorry for my english and thanks for any help!

ochkuba

You should not try use DMM to check the voltage on driver output to motors, because that is high frequency (range like 10's of Khz) while a digital multimeter reads like 3 times per second (3 Hz), so whatever the digital multimeter shows, the results ar not worthy of trust.

In conclusion, your motors just vibrate, your measured values are inconclusive. Because the motors vibrate in series, maybe one of them is skipping steps while the other doesnt, so they might fight each other sort of speaking. See that the motors are exact same type and same coil resistance & inductance, and also conductors wires are equal lenght to each coil. Maybe increase the current, or decrease it if needed. Turn them on and off and play with their angle, so their axial position will be both on full step when starting. Also if wired in series, the resistance increases (adds both coils) and if your coil resistance is like 6+ ohms, then in series will be double then the current wont have time to rise fast enough because the ohms law value is final value and that is just too close to the set point. So if the series connection doesnt work out because coil resistance is too much, then try parallel, but again preferably same wire length to both motors/coils.