Stepper motor jerky with DRV 8824

Hello, I need a little help please. I am new to this and have tried to research as much info as i could find but have not seen anything to help me with my issue. Sooo…what’s making me crazy…LOL…

I have a DRV 8824 stepper motor driver
I have a Stepper Motor: Bipolar, 200 Steps/Rev, 35×28mm, 10V, 0.5 A/Phase
I am applying 12v to the driver and have adjusted the current limiter to 325ma
I am driving the step with PWM @ 50% duty cycle from a 18f2431 PIC micro

I have connected it up as per Pololu instructions and made the suggested current adjustments. The issue, is when I apply power and step, it turns slowly, not consistent and is jerky. I have tried different ranges of current but still no joy. I applied 12khz to the step and it wouldn’t work so I changed to 15khz and it acted the same way. I used 12KHz which is ~ 1 rps.

For the life of me I cannot figure this out. I haven’t tried different duty cycles yet but that should not matter as current will still be constant.

Any help I will welcome. Thanks!

[quote]I used 12KHz which is ~ 1 rps.[/quote]12 KHz on the step input would be 60 revolutions per second in full step mode. Way too fast.


The behavior you described makes it sound like the stepper motor could be having a hard time keeping up with the step signal you are sending, as Jim suggested. Could you try stepping at a much slower rate to see if that improves the inconsistent and jerky movement? If it does, there are a few adjustments you could make that might help it step faster, such as using a higher voltage, setting the current limit closer to the per phase current rating of your stepper motor, gradually ramping up the step rate, or adjusting the mechanical load (if any) on the output shaft of the stepper motor.


Thanks Jim and Brandon, I think I see where my calculations went south. Thanks for the fast response!

Too fast wasn’t the word for it! I ended up with 180htz @ 165ma.

Thanks again!