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DRV8711 noise problem at low speed.

dh Paeng
Prodigy 100 points
Other Parts Discussed in Thread: DRV8711, CSD18531Q5A

Hi,

I'm using DRV8711 and I step motor.

I have one problem. Help me please.

If I select that pulse speed (lower than 10kHz), motor have noise.

not noise  at high speed.

 

 schemetic

 

 step motor spec.

 

By the way, current waveform is different.

low speed waveform is not good but high speed waveform is bad.

What's the problem?

 

Thank you.

 

  • 0
    TI__Guru** 114905 points
    Hi DH,

    Can you provide additional information?

    What are the settings in the registers?
    What is the step rates in the scope captures?
  • 0 in reply to Rick Duncan
    Prodigy 100 points

    Hi Rick,

    Sure.

    CTRL Register : No action, 1/32 step, Internal stall detect, Gain of 10, 450ns dead time

    TORQUE Register : 0x12, 100 us

    OFF Register : 0x30, Use internal indexer

    BLANK Register : 0xB0, Disable adaptive blanking time

    DECAY Register : 0xF0, Use auto mixed decay at all times

    STALL Register : 0x0A, STALLn asserted after 4 steps, Back EMF is divided by 8

    DRIVE Register : OCP 250mV, OCP 1us, Low 500ns, High 500ns, Low 200mA peak, High 100mA peak

    In addition, I have question.

    I move step motor. same motor, same register and different load.

    Then noise is different at 8kHz.

    Should I start from low speed like 300hz? or more lower?

    Can I move without acceleration Rate?

    Don't have problem to MOSFET(CSD18531Q5A) or DRV8711?

    I think, If don't have no problem,

    I'll use with same condition that Starting Speed, Stopping Speed and Target Speed.

     

    Thank you.

     

  • 0 in reply to dh Paeng
    TI__Guru** 114905 points

    Hi DH,

    For your description, I am assuming this noise is more motor vibration. You can try raising the starting and stop speed to 200 x microstep level and the acceleration rate to 100 x microstep level. Also set the steps to stop at 200 x number of microsteps. Some experimentation may be required to fine tune.

    The difference between the low speed and high speed current waveform is the amount of time at each step. The current chopping level is reached and the next step is call for. The waveform should look better at high speed if the VM voltage is raised or the number of microsteps is reduced.

    Should I start from low speed like 300hz? or more lower?

    This depends on the motor and load. Some motors have a datasheet which shows the maximum starting and stopping speed with no load. This is sometimes identified as fs, and is full steps per second. This can be multiplied by the number of microsteps.

    Can I move without acceleration Rate?

    Yes, as long as the starting speed is within the motor specifications. You can change the starting speed to achieve this.

    Don't have problem to MOSFET(CSD18531Q5A) or DRV8711?

    I think, If don't have no problem,

    I'll use with same condition that Starting Speed, Stopping Speed and Target Speed

    I do not understand. Can you explain this in more detail?

  • 0 in reply to Rick Duncan
    Prodigy 100 points
    Hi Rick,

    I sloved problem.

    I changed that move without acceleration and microstep.

    I learned new truths.

    If motor has load, I can't remove noisy perfectly.

    Thank you.