Changeover Relay for Switching Modbus (RS485) Signals


Thread Starter

Phillip Kristensen

I have a situation where I have a redundant GE Fanuc PLC with each PLC rack having PCM cards talking Modbus Master to other equipment, via an RS-485 link. There is a chance that both PCM cards could be "on the line" at the same time, so I want to put in a changeover relay to make sure that there is only one master on the link at any any given moment. Does anyone out there in the ether have any recommendations for a relay to do this sort of thing? It would need to have the capacity to switch very low current. I would like to run this relay coil off either 24Vdc or 110Vdc. Are there any other ways of solving this problem? Thanks.