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DRV8825: How to reduce current on idle machine

amir manaster
Prodigy 20 points
Part Number: DRV8825


How can I reduce the motor current when the machine is idle, so the motor will keep some torque and not move, while not heating too much...

And resume current to full setting when the machine is running and needs full torque?

Can I put PWM on nENABLE pin????

Can I reduce Vmot to 4V or less, so the current will be low even if DRV8825 keeps its outputs ON all the time?

  • 0
    TI__Guru** 114905 points

    Hi Amir,

    VREF is the preferred method of reducing current. Once the motor stops, lower VREF to a holding current level.

    When ready to move, raise VREF to the desired current.

  • 0 in reply to Rick Duncan
    Prodigy 20 points

    Hi, Rick.

    Reducing Vref would be the best, but I forgot to mention that I´m using those little boards you buy on eBay to be usaed on 3D printers and CNCs.

    I wanted a non-invasive method, for I will need to solder a wire on the track of the adjust potentiometer´s wiper.

    If so, this wire would to to a CD4066 analog switch and then to another potentiometer connected to GND only. This new potentiometer will be in parallel to the low side of the original potentiometer, which acting as a voltage divider, and make the low side "heavier", driving Vref lower.

    The board is quite dense with tiny SMDs. After all, I think that changing Vmot is easier, as I need to change one place and this will refelct on all drivers at once.

    Thanks!

  • 0 in reply to amir manaster
    TI__Guru** 114905 points

    Hi Amir,

    Lowering VMOT to 4V disables the driver outputs. The minimum operating voltage is 8.2V.

    Another option is to use the nENBL input, which also disables the driver outputs when holding. There will be no holding torque in this case.

    If you need lower holding current and are willing to modify the board, consider using one of the MODEx inputs to lower the VREF. MODE1 may be a good choice using 1/16 or greater and MODE2 if using 1/8 or less. Connect the pin through a series resistor to the wiper of the potentiometer (VREF), and use a GPIO to set the lower holding current.