Need Opto Coupler between RX-TX because interface use different voltage

Using Arduino General Electronics
1

Hello,

I need to use a Opto Coupler between the Arduino Uno and a Interface of the Domotica system RX-TX pins
So i want to put the Arduino on his own power supply and cannot connect the GND of the Arduino with the GND of the domotica interface.
So i am looking for a working schematic so that i can put in between Pin 0 and Pin 1 .
I have read that there might be a problem because after use a optocoupler the signal is inverted.

so i am looking for a working schematic so when the signal that i put on input is the same on the output and use different power supply.

The interface on the domotica system (EIB KNX) has a voltage out of 5V but low current not enough to power the arduino UNO.
For the moment i have a test case with a Arduino Nano (this one is not using much power) and use only 1 input . the is working like i want it but now i need to put a optocoupler between the RX-TX and then i can use the arduino UNO without being connected to the same GND and 5V power.
So the Domotica interface is powering the Arduino Nano but has not enough power for the Uno and the RX-TX are connected to the TX-RX (crossed) of the domotica interface.

Is there someone who can provide me a simple schematic.

I have here Optocoupler ILD2 so if there is a schematic compatible with ILD2 this would be great ! Any other optocouplers are also OK of course but since i have here the ILD2 i dont need to order different one.

Already many thanks !!!

Didier

2

The interface on the domotica system (EIB KNX) has a voltage out of 5V but low current not enough to power the arduino UNO.

You do not power an Arduino through an input pin.

You might drive an input from your system but that is not the same thing. If you device has not enough power to drive an Arduino input it will not have enough power to drive an optical isolator as that in effect is an LED. Therefore you will need to amplify this signal before you apply it to the optical isolator with a transistor, thus giving you the inversion you need to cancel out the inversion from the isolator.