Hi.
Can you try to elaborate a bit more? I’m not sure I understood your question.
Regards,
Sara

I have a relay that needs to be controlled from two sources.  How can I connect the output from each of these sources to control the relay?

So, you want to connect the same relay to two Arduino boards?
Two Arduino boards control the same relay?

Yes.

Yes.

Hi again.
I’m not sure if that’s possible or the right way to do it.
I’ve found these discussions about that topic that might help:

• https://forum.arduino.cc/index.php?topic=495208.0
• https://stackoverflow.com/questions/34438225/how-to-control-one-relay-with-two-arduino-boards
• https://arduino.stackexchange.com/questions/55074/can-multiple-arduinos-be-connected-to-a-single-relay

Regards,
Sara

Yes, this is what I am looking for.  It really helps.  Many thanks.

Great!

Put a diode on each output and connect together both cathodes, this connection goes to one terminal of the coil, the other coil terminal goes to the negative common to both Arduinos

Thanks. Yes, that will work.

Thanks. Yes, that will work.