track occupancy detection for computers

Greg-

If I am following, you want the output voltage from the relay to the input on the PLC/computer to be no more than 5V DC. If so then you can use any kind of relay (most use SPDT "ice cube" relays with 12V DC coils with insulated sections), but you will need to add a rectifier and a +5VDC voltage regular (LM7805 for example) to ensure the input to the PLC will be a maximum of +5VDC.

If you like, I can provide a wiring diagram and parts list to help with your project.

-John

See Professor Chaos' post of April 18 4:11PM:

https://ogrforum.ogaugerr.com/t...se-arduino-on-layout

Note how he uses an AC-input opto-coupler.  Likewise when you see guys using relays for same purpose, they either need to use an AC-coil relay.  These AC-input devices are usually harder to find, more expensive, etc.

An alternative is to use an isolated DC supply such as a surplus wall-wart and have that be the voltage "switched" across the wheels into the isolated track sections.  Then you can use a DC-input opto-coupler (or a "regular" DC-coil relay).