In my project i will have 8 digital outputs from arudino which will be used by an OMRON PLC (supplied by 24VDC).
I have a board with 8 relays:
My idea is that:
- Supply the relay board from arduino +5V and GND
- IN1-IN8 are arduino digital outputs. ( I tested that the relay signal is okay for Due's 3,3V).
And now there is a part for the output of the relay. I can use the +24VD from PLC so let's say the +24V (one wire) comes in from PLC and i split it in relay (COM and NO) for example the wire comes to COM and comes out from NO to the output like this
BUT because my project will be basically an IO module for PLC I am thinking, what with the GND from PLC ? I am not sure if i should connect it somewhere in my module or not and if I should connect it should I just connect it to the output so the user can take and use this GND to some other parts.. BUT I do not know how I should connect the GND and where.
Do i need to use the GND and if I need then in what way ?
PS I think I also need some fuse at the +24VDC wire and maybe some resistors, can someone provide me some values?
Or I should add the GND wire like this :