I'm interested in using the standard isolated rail occupancy detector trick to drive logic level input on an Arduino.
It sounds like the right way to do this is to use a relay (and an optocoupler wouldn't hurt). There have been some great forum threads on this topic (example), but from what I can tell they are more focused on driving LEDs/lamps directly. Is it any different to safely drive a logic level input?
For reference I'm looking at eBay #142155381144. The isolated rail would feed the IN pin (via a resistor, as shown in the linked forum thread), and the Arduino would be connected at the "output" end, essentially directly to the relay.
I think what's confusing me is that these modules are advertised as helping convert from logic level voltage (output from an Arduino) to a higher voltage, where I'm looking to do it the other way around.
Am I making this too complicated? Thanks!