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DRV8434A: Initial setup of stall detection

Joakim Innvær
Prodigy 10 points
Part Number: DRV8434A

I'm trying to setup stall detection for a Sanyo Denki 103H7823-5740 stepper motor (seems to be discontinued, so we will probably have to use something else in production).

Probably irrelevant, but in my setup, i have a PLC controlling the step/dir signal of a polulu driver carrier with all connections connected by soldering 0.75mm2 wire to all terminals, and connecting to everything via WAGO 221.

This setup works as normal without stall detection, but I don't quite understand how to enable the Stall detection.
I have tried following the datasheet as best i can. I Start the driver in torque count mode, and when I get a stable speed, I remove the connection to ground, so that the only connection to STL_MODE is the 1nF capacitor on the polulu stepper carrier. nothing is forcing TRQ_CNT/STL_TH or STL_REP to any value, i am only measuring with Analog inputs on the PLC and/or a multimeter. Still, not only is STL_REP not being pulled down after measuring, it is not even pulled up in the first place.

I also do not see any measurable voltage from the TRQ_CNT/STL_TH pin when in torque count mode, even when i pull STL_REP down to 0V.

I tried enabling stall detection mode with around 0,5v and 1v on the TRQ_CNT/ STL_TH pin, but it didn't do anything even when the stepper was completely stalled.

  • +1
    TI__Genius 14895 points

    Hey Joakim,

    It looks like you'll need to add an external pull-up resistor to the STL_REP pin with that motor carrier board to be able to read the STL_REP status since it doesn't have the resistor already.  

    Just to make sure, did you stall the motor after the driver has time to learn the steady count?  Following these steps

    You can also try it at a different speed, as the stall detection might not work at high/ low speeds. Let me know if any of these work.

    Regards,

    Yara

  • 0 in reply to Yara Al Shami
    Prodigy 10 points

    Yes, you seem to be correct, i can not see a pull-up resistor on STL_REP. do you recommend a specific resistance, or is it fine with for example a 10kohm resistor?

    I believe i let it learn the steady count, but it was a bit unclear what an electrical cycle means. i assume it is the same as the motor going 1 or 2 steps? or is it an entire rotation?

    i'm not quite sure what is meant by high or low speed. I'm guessing it's not possible to say specific rpm values since all motors are different, but i don't know if 1 rpm is too slow or if 1rps is too slow, and i have no clue what counts as normal or fast.

    Edit:  A 10kohm resistor worked fine, so it seems i do need a pull-up resistor connected to that driver carrier for stall detection to work.
    I found a speed value that works for my motor, its quicker than expected, i think it worked when i had 20 rotations per second on a 2A max stepper motor driving with 1A power limit.