Nema 17, 1.3A, current limit question


I have a nema17 connected to an A4988 driver but I never even checked to see what current limit it is on. I was way too busy with the code :slight_smile: The motor seems to run just fine, but I’m not sure it is running at the correct setting.

Also, I was reading the specs on the A4988 and the continuous current limit is 1A, my stepper is rated 1.3A.
Using that vref calculation, the max current should be: Current Limit = VREF × 2.5, CL = 1.3/2.5, CL= 520mv

Is that correct? Or should I use a higher rated driver like the DRV8825?



It looks like your variables might have gotten switched around in your calculation, but to set the current limit to 1.3A on the A4988 carriers, the VREF voltage should be set to 520mV, like you mentioned. However, none of our A4988 carriers can continuously handle that current. We have a couple different versions of the A4988 carriers. If you have the version of the A4988 carrier, it is rated for delivering a continuous 1A per phase (without additional cooling). Since this is lower than your 1.3A per phase motor, you should set the current to the driver’s recommended maximum to avoid overheating and triggering the over-temperature thermal shutdown. Limiting the current to lower than the stepper motor’s rated current will slightly reduce the torque output of the motor, but if that is not a problem in your system, it should be fine.

If you need the extra torque, the DRV8825 stepper motor driver carrier can handle the full 1.3A per phase of your motor. Please note that the calculation for VREF on the DRV8825 carrier differs from the A4988 carriers. You could also consider the #2128 A4988 carrier, black edition, which is a higher performance version of the #1182 A4988 carrier and can handle a continuous 1.2A per phase.


Thank you very much Brandon. Torque is important, but I’d have to test in real life to see how much torque is lost with a lower current. I think I’m better off getting the DRV8825 so that if torque is an issue the 8825 can deliver it.

thank you!