A4988, stopped working

I’m using an A4988 to drive a 2.8V, 1.65A per phase stepper, feeding it 12V (from a bench supply). I can post a photo of the circuit tomorrow, but I’m pretty sure it was ok, given that it ran fine for a while (consuming about 0.75A, which sounds about right?). At some point I turn it off, turn it back on - and nothing happens. I check all the connections, try again - nothing. I swap the driver with another one, and it works. Seems like that driver just mysteriously died on me. I’m really stumped here.

I need to get this to work ASAP and I can’t afford to lose another driver. Any idea what would cause something like this to happen? I had the impression that these drivers were practically indestructible… :confused:

Thanks!

  • forgot to mention that I can still see voltage on one of the coils, but I’m not sure what that means (something like 6V if I remember correctly - will verify tomorrow).

Hello.

I’m sorry to hear you are having trouble with your stepper motor driver. I think a picture of your setup could be very helpful. Can you be more specific about how you “turned it off” and back on? How long are your power cables? Do you have access to an oscilloscope?

The driver has various built-in protections, but those can only go so far, and it is certainly not indestructible. If anything, you should consider components like this fragile, and it’s a good idea to have a spare or two around in case you accidentally kill one. There are many ways you can instantly and permanently kill such electronics components: voltage spike outside the parts maximum limit, accidental short circuit of two independent nodes, connecting power backwards, electrostatic discharge (i.e. zapping it with your finger as you pick it up), etc.

- Ben

“Turn it off” meaning cut the power (logic, then motor). I doubt there were any voltage spikes considering I was using a pretty reliable switching power supply. Power cables were short (maybe 5"?) and I do have access to a scope.

I overnighted two boards this time to make sure I have a spare one. I’ll post a picture of the circuit soon. What would I use the scope for?

Did you turn power off by turning off the power supply, or by disconnecting the power supply cables? If it’s the latter, are you completely sure you didn’t accidentally touch another pin with one of your power lines as you were disconnecting it? If it’s the former, in general, there can be all sorts of noise/voltage spikes on power supply outputs when you turn them on and off; even good power supplies don’t necessarily have great turn-on characteristics (you could use a scope to see if this is indeed the case). I strongly recommend disconnecting your power supply from all circuits before you turn it on and off.

Also, what are you using to power your logic?

- Ben