DRV8825 holding torque

HPB

Other Parts Discussed in Thread: DRV8825

I got my setup with the DRV8825 working nicely. I even did a few test prints for my laser cutter using grbl and they came very precise. I have one question though. Earlier I was using the Allegro A4988 drivers and every time I'd switch on the supply I would get a holding torque which would prevent me from moving the axes manually. However with the DRV8825 drivers I can still move the machine manually when the supply is switched on. Is this normal? The driver setup is mostly the stock reference from the datasheet. I've attached the schematic of how they are wired in my setup.

I'm using NEMA 17 motors that support upto 1.7A per phase and with the current limit set at 1.5A (Vref is 0.75V with 0.1R sense resistors).

over 9 years ago

0 Luis Riveros over 9 years ago

TI__Expert 4435 points

Hello,

Our experts have been notified and should reply soon. Thank you

0 Phil Beard over 9 years ago in reply to Luis Riveros

TI__Expert 4650 points

Hi HPB,

Do you know the state of ENBL when you power up? When ENBL is low the two H-Bridges are enabled, so a holding torque will be present. While ENBL is high, the device is enabled and the H-Bridges are HI-Z.

0 HPB over 9 years ago in reply to Phil Beard

Expert 1350 points

Hi Phil,

According to grbl's FAQ, apparently the steppers are enabled while the Arduino boots up and grbl initializes. This is for a about a second or two and the stepper enable pins are low. Once grbl initializes the stepper enable pin goes high and disables the steppers. I guess with my A4988s, I had left the enable pin floating and hence it was always low enabling an always ON holding torque. Thanks for helping me understand this.

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DRV8825 holding torque