Opto coupler grounding query

[Umit45]

Hi everyone,

I wanted ask about the optocoupler circuit used to isolate a microcontroller and a motor driver board.Is it alright if I connect the input and output grounds together to make a common ground and connect it to the ground of the controller.
I was of the opinion that an opto coupler does not allow any high currents/voltages to go back to the controller in case of a malfunction of the driver board. But I am not sure about if should connect all the grounds together.
Please let me know your views about it.

Thanks,

 

[Audioguru]

An optocoupler isolates the grounds to prevent you from being electrocuted if the wiring has a fault and you touch a "grounded" part and you are grounded.

 

[srizbf]

the very purpose of optocoupler is to isolate the grounds , for noisy environments.

but if you want to connect both grounds together , you can do. there will not be any ground related advantages.
if already there is a shock prevention included in your design , then you should avoid it.

 

[KlausST]

Hi,

You may connect the grounds together (as long as there is no other connection of both supplies).
But then the optocoupler is useless somehow. Then you could do without an optocoupler.

Klaus

 

[Umit45]

Thanks to everyone for the replies!

I separated the grounds on my board but the output of the optocoupler was very noisy. I have used a ground plane in the board. Although there is no connection between the two grounds, the board ground seems to be affecting the input of the optocoupler. The input becomes nosiy after I switch on the supply.
I also implemented the circuit with two grounds on a breadboard and it gave accurate output.
Is there any other way other than remaking the board in such a case.