opto isolator to protect a micro's input

[david90]

Is there a point to using an opto isolator to protect a micro's input if the opto isolator's LED and the phototransistor DC return is tied together?

In other words, would the opto isolator still protect the micro's input if there's only one power supply and 1 DC return?

 

[hameeds01]

Re: opto isolator

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,

 

[Tahmid]

Re: opto isolator

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.