DRV8825 and unipolar motor setup

hello, i am new on pollulu/motor and i am try to use 3 or 4 old stepping motor kp56lm2-097
Unipolar / 2 phases 6 Volts DC (nom) 1.2 Amps / Phase (nom) 2.4 Amps /
Motor 1.8 Degree/Step 80 oz/Inch
200 steps per rev.
2 1/4 inch. diameter 2 1/4 inch. length (excluding shafts) Size 2.2 sqi Double shaft NEMA 23 size motors
11/16 inch Shaft length.

i made it a new cnc router and the controller will be a cnc arduino shield v3.0 with 4 dvr 8825
i am try to figure out the right Vref. i set it the vref at 1.2vdc and the motor its not going hot but the drv8825 start to get hot. i am not sure if i need a bigger power supply or not. i use 12vdc right now.
i only tested on one stepper motor so far .

did i set the vref right or wrong , whats the formula to figure out the right Vref and the power supply should i get something higher that 12vdc. ???
thank you.


VREF is set too high. The DRV8825’s maximum current per phase is 1.5A without additional cooling, as stated on its product page. With your VREF voltage, you are trying to set the current limit to 2.4A. I think you might have calculated VREF using the combined current rating of both coils (2.4A) instead of the current rating per coil (1.2A). VREF should be set to 0.6V. You can find the formula and details for current limiting for the DRV8825 under the “Current Limiting” section on its product page.

Can you post pictures clearly showing all your connections in your setup? Please note that the DRV8825 is a bipolar stepper motor driver, so you need to connect your stepper motor in bipolar mode (if you have not already). If you are not sure how to do that, see the “How do I connect my stepper motor to the DRV8824 or DRV8825 stepper motor driver carrier?” question under the “FAQ” tab on the DRV8825’s product page.

- Amanda

Thx, for the help. Now works , I set it the Vref a .600mv . Thank you.