Stepper motor on other motor direct shaft connection

Hi !

I have to drive step motor which is directly connected to other (main) motor shaft. So when main motor running, my stepper motor is also running. Main purpose of this application is to drive main motor (2 speed, three phase 380V AC motor) until some time I switsh it off, and then stepper motor take control of running the lead screw.

So when main motor running, stepper motor is acting as generator, which, I’m afraid can destroy drv8825 ? Or not ?
This is from documentation:

So If use these two pins, it seem to me as drv8825 is safe when motor pumping it with generated energy ?

I mean to use relay to disconnect motor completely, but if above procedure is secure, it will be easier to finish job.

Please advice!

Regards !


Hello, Mladen.

Even with the H-bridge disabled, back EMF will go through the body diodes of the MOSFETs and to your power supply, which could damage your other electronics. Disconnecting the stepper motor from the driver using relays might work and would probably be safer. You should make sure that power is not being supplied to the stepper motor (using the nENBL or nSLEEP pins) before disconnecting the motor from the driver.

- Jeremy