I have a motor controller that outputs a fault by pulling down its I/O pin (PIN 10). It will also go into fault if you external pull the pin down too.
The MC has two configurable pullups: A: The output pin is pulled high by a 100K resistor @ 30V. B: The output pin is pulled high by a 1K resistor @ 6V.
I require an isolated method of monitoring this voltage, my solution is to use an optoisolated that is supplied by the motor controllers 5V output via a 510R resistor.
When the motor controller goes into fault, it will pull down to the ground and turn on the opto. A diode prevents backfeeding of the 6V (B)/ 30V (A) into the motor controllers 5V rail.
I have tested this and it is working, but is there any negatives, or better solutions?