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DRV8876: back emf to detect obstacle

inya_lake1
Prodigy 165 points
Part Number: DRV8876
Other Parts Discussed in Thread: DRV8231A

Hi,

 I'd like to use DRV8876 to control my motor. However, I'd like to know if there is a obstacle in the way during motor operation. Similar to car garage door, when obstacle is present, I want motor to roll backwards. It is traditionally accomplished by detecting back emf. Is there similar function in DRV8876 to detect such conditions. I noticed current sense function in DRV8876 but not sure it can detect obstacles or not. If not, would you be able to recommend a part that has a way to detect motor is not moving forward as instructed due to obstacle or something along it's track.

Thanks

  • 0
    TI__Mastermind 37683 points

    Hi,

    The DRV8876 does not have a direct way of detecting when motor stalls due to an obstacle. However, you can use the current sensing to create a simple way of detecting when motor stops by monitoring the current. The IPROPI voltage can be monitored with an ADC channel of a microcontroller. If you know the stall current of your motor, you can have the MCU switch the control logic whenever the current goes above that stall current limit. There are a few other things that need to be considered. For example, during initial start-up, the current can go above this stall limit so you'll have to set a delay to ignore this initial in-rush current.

    We provide an design example in section 9.2.2.2.1 of the drv8231a datasheet. Please read that section and let me know if you have further questions.

  • 0 in reply to Pablo Armet
    Prodigy 165 points

    Thank you. That was very helpful.