I think I roasted the board, perhaps due to a bad motor. The motor is a Jazzy wheelchair motor and the power source two 12v 15Ah LiFePo batteries in series.
Motor 1 appeared to be working well, but not motor 2. I saw a fault reported on motor 2 during testing of motor 1 so disabled the fault check for motor2 example.py, so I could continue testing motor 1. Right after that, motor 1 stopped working as well and the board now seems to have a short circuit.
After this, I hooked the board up to a bench power supply with nothing else connected (not even a raspberry), I see the current go up to the maximum my supply can handle (a bit over 3A) with the input voltage dropping to less than 1 V.
Here are some thermal pics taken during this:
First pic is of the entire board, seen from the component side with the raspberry connector at the bottom:
The second image shows a little more detail of the area on the bottom left:
And the final image shows the back of the same area:
I have the following questions:
What does “fault” mean when reported by example.py? Is it a communication error or does it mean there is some sort of electrical problem?
It seems that the two chips on the bottom left of the board are getting very hot now. What is their function? Does it indicate they have failed or might there be an external short circuit (I’m hoping)?
If the board is destroyed, what is the most likely cause?
Why didn’t the current limiting circuit protect it?
What steps can I take to prevent this in the future? I’ve run the motor that the board wasn’t able to move directly of a battery and it worked.