Help to debug wierd problem with VHN5019 shield

The symptom of my problem is that the board appears to work just fine without motors connected, i.e. red & green LEDs light up as expected fwd/reverse, both channels.

But when I connect motors to them, the LEDs don’t light up any more. (yes I power down first, and can swap repeatedly between ‘working’ and non-working leds, by connecting/disconnecting motors.

I’ve confirmed there is nothing wrong with the hardware, I can run the demo program and it drives 2 motors fine. But in my application I now want to use only 1 brushed motor, plus one stepper motor, which I’m driving with a A4988 breakout board on another shield. Presumably I’ve got some conflict with pin allocations, with the VHN5019 library fighting me for some pin, since. But I can’t figure out why connecting the motors ‘turns the leds off’.

thanks in advance


Since the Pololu Dual VNH5019 Motor Driver Shield for Arduino uses many pins, there is likely to be a conflict. Please note that connecting shields without considering what pins they use is a recipe for damaging your electronics. If luckily nothing has been damaged, it is not likely for anything to work until you resolve any conflicting connections and code. You can compare your A4988 breakout shield’s pin usage against the Shield Connections section of the motor driver shield’s user’s guide and the shield library source code with the other code you are using.

- Ryan