what type of load u r using is it inductive load?? 220v or what ? if it is just an inductive load then don't forget to use flywheel diodes, YES it will protect some how the inputs of ur controller even if u use a single power supply,
Hi david,
I guess maybe it does help sometimes. eg. If there is too much current flowing in the LED side due to high voltage, in that case, maybe your microcontroller pin will be saved, ie, if the optoisolator does not get shorted and the high voltage comes to the microcontroller pin.