Bipolar stepper motor doesn't spin but vibrates

Question

I got a problem with controlling a bipolar stepper motor. It doesn't spin but vibrates. Here is the schematic of my stepper driver: DVDD supplies 5v DC.

Here is the wiring map from the motor's specification:

here are the motor and how I wired it up to my PCB:

There are some hints about acceleration and high torque in the specs as well.

Full disclosure: I am not sure what to do with this info, I am not an electrical engineer. Now, I have tried to write a simple python script to drive the stepper. However, all my best efforts ended up with the motor vibrating.

import RPi.GPIO as GPIO
import time
 
delay = 0.005# time to settle
 
drv_m1 = 8 #GPIO08
drv_step = 20 #GPIO20
drv_dir = 26 #GPIO26
drv_nfault = 21 #GPIO21
 
def setup():
   GPIO.setmode(GPIO.BCM)
   GPIO.setup(drv_m1, GPIO.OUT, initial=GPIO.LOW)
   GPIO.setup(drv_step, GPIO.OUT,initial=GPIO.LOW)
   GPIO.setup(drv_dir, GPIO.OUT, initial=GPIO.HIGH)
   GPIO.setup(drv_nfault, GPIO.OUT, initial=GPIO.HIGH)
 
 
setup()
 
try:
   while 1:
       GPIO.output(drv_step, 1)
       time.sleep(delay)
       GPIO.output(drv_step, 0)
       time.sleep(delay)
except KeyboardInterrupt:
   pass
GPIO.cleanup()

I have tried a varius delay values (between 0.0001 and 0.1) and tried out using PWM with frequencies as low as 100hz to 14000hz with no luck.

Any ideas what could be causing the problem here?

Answer 1

You're using the wrong chip. The DRV8428P that you're using is not a stepper driver, it's just a dual H-bridge. Your code is therefore simply switching one of the stepper motor's coils on and off, making it vibrate.

You need an actual stepper motor driver that has "step" and "direction" input pins. Alternatively, you'll have to generate the waveforms for the stepper coils manually.