I want 4 arduinos to get an input from the same relay (standard mechanical relay). Using 4x relays is not an option so would this work?
Why the relays? What is their purpose? How are they connected? Shit dude, there's a TON of detail you're not giving us. Please try to understand that we can't see your project or anything you've got. You've got to give us something to go on. Relays are for sending a signal from Mega to the Uno's. Is there another reliable way of doing this?Mega Output --> Relay --> Uno Input (Input_Pullup and GND connected to NO and COM)There are multiple audio/light tracks, each relay corresponds to one track, Relay1 for Track1, Relay2 for Track2 and so on. When Track2 starts, the Mega will close Relay2, the 4 Uno's will all read the input from Relay2 and start Track2 at the same time.
Just make sure you don't ever configure that pin on the UNO as an output and try to write it opposite the state on the mega.