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Put a TVS diode across Vmot on stepper motor driver boards


In another thread (https://forum.pololu.com/t/stepper-motor-deceleration-causing-large-voltage-spikes-15-20v-rise/9823), I mentioned that I found that decelerating a stepper spinning a big flywheel with your DRV8825 drivers caused massive voltage rises: my 20V supply line went to 40V for several tenths of a second due to back-emf. Even with several times the recommended capacitance.

While my DRV drivers survived, a set of A4988’s I was using in the same situation was destroyed by the over voltage.

Hence my suggestion: put a TVS diode across Vmot and GND on the boards that clamps the voltage to the limit for the driver. It might save boards from this sort of voltage spike, which can kill boards hooked up by your current recommended minimum wiring diagram.