Stepper motor sends power to the Core when turned manually, can this damage it?

Hi, I have successfully setup my Core to control multiple stepper motors (thank you for all the great work in making this possible!). One thing I noticed, however, is that when I have my system turned off (no power connected to the Core or to the motors), and I move my motors manually (with my hand), I can see the RGB LED on the Core briefly flicker different colors. I understand this is because spinning the motors manually generates current, what I am wondering is could this possibly cause damage to the Core and/or corrupt the firmware programmed onto it? I haven’t actually noticed any issues… I am just wondering if there is any potential for this to cause issues? Thanks!

Yeah you can potentially damage the core if you spin too hard and cause a huge voltage spike.

How did you connect the motor to the core?

Hi Kenneth, I have control wires running from the digital pins on the Core to a L293DNE motor driver. The motors (when powered on) have a separate 12V power supply. So the risk is just from spinning it so hard it creates a large voltage spike (which I wouldn’t expect from the rates I was moving the motor manually)? There’s no risk of any issues related to the Core being partially powered up and then shutting off repeatedly?

There can be cases that the flash gets corrupted due to that but maybe someone else can chime in here :wink:

Hi @sddw

Sure, you could hurt something by spinning the motor but it is a bit unlikely. I think you are powering up the LED but not the core.

If you are worried about it or if the motors can be continuously back-driven in your application, then you should opto-isolate the motor controls from the core and use separate power supplies.

Another good idea would be a zener diode rated for some reasonable voltage like 3.9 or 4.4V across the core’s power supply. This will conduct if the voltage exceeds the zener voltage and make sure that voltage is not exceeded.

In one application I even had a relay that shorted out power to part of a circuit to protect it from dielectric absorption but that was a very strange application since the relay had to be controlled outside the shorted out zone.

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Hi bko, thank you very much for the input! I think this points me on the right path, I will especially look into your suggestion of using a zener diode as this seems to be a simple method to provide some protection. Much appreciated.