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DRV8711EVM: Reaching Desired RPS with 1/2 step

Griffin Peterson
Prodigy 40 points
Part Number: DRV8711EVM

For my application, I need to be able to run my DRV8711EVM at ~60.1 rev/s. My understanding of reaching a desired angular speed is:

200 pulses/rev * steps/pulse * rev/s = steps/s

So for 12,000 steps/s and 1 step per pulse, I expect 60 rev/s (which is what I get!)

My issue is I need a bit more precision in my stepping frequency. If I go to 24,000 steps and 2 steps per pulse (half step mode) the motor stalls.

I'm running on 24V and when the motor stalls, I am drawing about 800mA of current - if it is a 3A motor why does it stall?

Thank you!

  • 0
    TI__Guru** 114905 points
    Hi Griffin,

    The motor can stall based on several events. Generally it is one of the following:

    the motor is accelerated/decelerated too quickly from one speed to another
    the current cannot be inserted or removed quickly enough as the step current is changed
    too little current is set for the motor

    If you have a current probe, please examine the current in the motor to determine if you are getting the specified amount. If you are not, this can be remedied by:

    Raising the VM voltage - this will allow more current at each step.
    Changing the step rate to full step, and lowering the pulses/second
    Slowly accelerating/decelerating from 0 to the desired speed.
  • 0 in reply to Rick Duncan
    Prodigy 40 points

    Hi Rick,

    I increased my VM voltage to 30V and reduced my acceleration rate - the motor now spins at 60rps in the half step mode.

    Thank you!

    Griffin Peterson