Please could someone help me with a problem I am having connecting a Raspberry Pi to a DRV8825 controlling a Nema 17 stepper motor.
This is my first time using a forum so please bear with me.
I followed the wiring diagram on www.rototron.info/raspberry-pi-stepper-motor-tutorial/ except as I am using an older Raspberry Pi I connected the STEP pin to 17 and the DIR pin to 22.
I am using a Nema 17 stepper motor SY42STH47-1684A that has a rated voltage of 2.8V and a Rated Current of 1.68A. I connected the VMOT and the GND of the DRV8825 to a laptop power supply rated at 15V 5A and set the Vref of the DRV8825 to .84v before powering off and connecting the motor leads.
When I plug the laptop power supply back in powering the motor everything is OK until I turn on the power to the Raspberry Pi. It appears as soon as the Raspberry Pi’s 3.3v pin goes high and powers the SLP and STEP pin of the DRV8825 the stepper motor starts humming and juddering.
Any help with what could be wrong would be very much appreciated.