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DRV10983 Speed Question

walter castellon
Prodigy 30 points
Other Parts Discussed in Thread: DRV10983, DRV8307, DRV10983EVM, DRV8308EVM

Hello,

I currently have the DRV10983EVM and am using it to evaluate a BLDC motor connected to an 8 blade fan.  the fan is used as an optical chopper and for the most part the DRV10983 works fine, my question was with regards to accurate control of RPM speed.  We use a photo-transistor to monitor the speed of the blade and I noticed using PWM control there's a minimum delta between my ability to control the speed of the motor, i.e. i have about a 4 hz step in blade speed and i'd like to reduce that down to at least 2 hz.  I was hoping to be able to write software to use a micro-controller to vary the Duty Cycle to achieve that resolution but i wanted to confirm that something like this was possible with DRV10983 or would something like the DRV8307 be more suitable for this application (i do have the option to switching to a motor with hall effect sensors).  Would the DRV10983 be able to respond to fast changes on its input speed pin?

Thank you for your time

  • 0
    TI__Expert 4435 points
    Hello Walter,

    Our experts have been notified and should reply soon. Thank you
  • 0 in reply to Luis Riveros
    TI__Expert 3010 points
    Hi Walter,

    DRV10983 has 9 bit register for speed input so basically you can control speed input with 511 unique steps. You can control speed using micro-controller by communicating through I2C (Refer section 9.4.5.4 I2C Mode Speed Control in datasheet )

    What is maximum electrical speed of operation and intended speed response time?

    Regards,
    Krushal
  • 0 in reply to Krushal
    Prodigy 30 points

    Hello Krushal,

    Thanks for the reply, my motor spins at 10,000 RPM and my speed response time can probably be very fast if needed, my motor is small, and the load is very light, just an 8 blade fan.  The motors Kt is about 40.3 and Phase Resistance is 2.32, for me stability would be the most important.  Does the DRV10983 react instantly to changes in its speed register?   10,000 RPM is about 19.56 rpm/step, If I'm switching the speed registers between two value's at a fast rate, will it just over shoot and undershoot my desired value?  

    Thank You,

    Walter

  • 0 in reply to walter castellon
    TI__Expert 3010 points
    Hi Walter,

    How many pole pairs does this motor have ?
    The reaction time of DRV10983 can be several mSec and it can vary based on mode of speed input selected and setting of some of the configuration parameters like closed loop acceleration acceleration current limit etc. Best way to find out it by testing it out on bench .

    Regards,
    Krushal
  • 0 in reply to Krushal
    Prodigy 30 points

    Thanks Krushal,

    Its a 4 pole motor, I've gone ahead and ordered the DRV8308EVM and a microcontroller to test both out, I appreciate the help.

    Walter.