Microstepping DRV8825 with NEMA 17 bipolar motor?

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1

I would like to use the DRV8825 in micro-stepping mode with an Adafruit NEMA 17 bipolar stepper motor. Adafruit specs the motor for 35 ohms per winding, 350 mA/winding max at 12V. I have measured the current for one winding using a hall-effect ammeter to be 295 mA at 12V in single-step mode with no stepping taking place, which is fairly close to the 0.7*Imax value you described (0.7 * 0.35 = 0.245).

I currently have the current limit set for .5V at VREF (1.0 Amp?), but after reading the Max. Step Frequency for #1206 Stepper?, it appears that to use micro-stepping I need to set the current limit to something lower. However, it wasn’t quite clear to me what that lower value should be. Should I set it to 0.245A (i.e. 0.122V at VREF) or something else?

TIA,

Frank

2

Hello, Frank.

We recommend you set the driver’s current limit so that the VREF voltage corresponds the rated current of the motor, 350mA (which would mean 0.175V at VREF). If you measure the actual coil current in full-step mode, you should see a current of 70% of that, which would be about 245mA in this case.

- Patrick

3

Patrick,

Thanks!

Frank

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