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DRV10983: Changing speed through I2C but motor speed is unchanging

Allan Gu
Prodigy 10 points
Part Number: DRV10983
Other Parts Discussed in Thread: MCF8316D, MCF8315C, MCF8315D, MCF8316A

Tool/software:

Hello,

Our group is currently working on design a motor driver PCB using the DRV10983 IC to control our BLDC motor. We were able to get the motor to rotate (although very jittery) but our main question currently is adjusting the speed settings SpeedCtrl (0x00) with an override set to 1 to use I2C, writing to the speed control with any speed value from 1-511 doesn't seem to change the actual rotation speed of our BLDC motor.

Our motor phase to phase resistance measured 0.4 Ohmns (Which we believe may be causing issues since it is out of the range specified in the documentation)

Our eeprom values are: [0x1C, 0x04, 0x1A, 0x00, 0xC0, 0xFF, 0x88, 0xB0, 0xAE, 0xC9, 0x0C, 0x1F]

If we could get any help on this, that would be greatly appreciated.


  • 0
    TI__Mastermind 23542 points

    Hi Allan Gu,

    Resistance is outside the recommended range, what about phase-to-phase inductance?

    How is KE measured? Is it according to tuning guide / data sheet suggestion?

    You can try adjusting the Lead time, it is very low 50u in the setting.

    Please refer to application note for lead time and test again.

    Have you looked at other product MCF8315C, MCF8316C, MCF8315D, MCF8316D these are FOC based control?

    Thanks and Best Regards

    Venkatadri S

  • 0 in reply to Venkatadri Shantaram84961
    Prodigy 10 points

    Hi Venkatadri S,

    Yes, the KE was measured according to the tuning guide which we found around 4mV/Hz.

    Sorry for our inexperience, but can you send a link for where this application note for lead time was?  From what we saw, decreasing the lead time resulted in a less jittery motor. 

    We're currently looking into the MCF8316A and MCF8315C.

    The LR constant (shown below) measured from one of the motor phases was around 2A using the tuning guide but we aren't sure how LR translates to lead time:




    Thank you for your time. 

  • 0 in reply to Allan Gu
    TI__Mastermind 23542 points

    Hi Allan Gu,

    Please check this link for the app not Tuning Lead Angle in DRV10x Sensorless BLDC Drivers

    When you are able to rotate motor try to read the BEMF constant which device is estimating, you can read the value in display window by enabling Auto refresh.

    Is your motor on no load when you are testing? Some motors can run to full speed even for small command when on no load and we don't see effect of command.

    I also notice another thing, Close Loop Disable is enabled, this may be main reason, it remains in open loop.

    Thanks and Best Regards 

    Venkatadri S