On the list of "cost effective methods", do you see any issues with using an photocoupler like this? Where the 5v side would power the LED/emitter, and that would close the collector circuit on the 3.3v side completing the grounding...
I think so, circuit A with the 5v button is the system we are monitoring, and when that button presses we want to ground or pull to zero a trigger on a different system. The trigger on system B can be set to look for a high (3.3v) or low (grounded) condition to trigger, the default is grounded...
I need to detect a 5v button press (single wire in/out on the button) on an alternative system, and close/ground a 3.3v circuit on the local system when that 5v button is pressed on the separate system. I am sure this is super basic but I am stumped, any help is greatly appreciated.
System A...