wirelessliquid
Member
Hi guys,
Just wondering if anyone has tackled an issue similar to this before: creating a redundant master on Modbus so I can have a redundant PLC in my unit.
I need to design a system where I have 2 PLCs (a shadow/redundant PLC with the same program on it) so if the primary PLC is to fail then the secondary PLC can take over.
The Comms protocol used is Modbus RTU (Carel Modbus RTU) and the controller of choice is Carel cPCO Mini. Each Controller has 2 Modbus ports.
With Modbus being a single master protocol, could I use the first Modbus port to connect the primary and secondary controllers together to create a heartbeat between the two controllers to detect if the primary is still alive and communicating. The Primary Controller will use the second Modbus Port and be set as a master to connect to all sensors and devices.
The Secondary Controller will also be set as a master on its secondary Modbus port but the port will be disabled if the heartbeat between the controllers on Modbus port 1 is healthy. If the heartbeat has an error detected, could I deactivate the Primary PLC Modbus port 2 and enable the Secondary PLC Modbus port 2. This way I should have a redundant master and only 1 master active at a time talking to the sensors and devices.
Will this work? am I barking up the wrong tree? am i missing some key info? I am not so familiar with Modbus as I have been mainly using Ethernet IP for the past 4 years.
Kind Regards,
Wirelessliquid
Just wondering if anyone has tackled an issue similar to this before: creating a redundant master on Modbus so I can have a redundant PLC in my unit.
I need to design a system where I have 2 PLCs (a shadow/redundant PLC with the same program on it) so if the primary PLC is to fail then the secondary PLC can take over.
The Comms protocol used is Modbus RTU (Carel Modbus RTU) and the controller of choice is Carel cPCO Mini. Each Controller has 2 Modbus ports.
With Modbus being a single master protocol, could I use the first Modbus port to connect the primary and secondary controllers together to create a heartbeat between the two controllers to detect if the primary is still alive and communicating. The Primary Controller will use the second Modbus Port and be set as a master to connect to all sensors and devices.
The Secondary Controller will also be set as a master on its secondary Modbus port but the port will be disabled if the heartbeat between the controllers on Modbus port 1 is healthy. If the heartbeat has an error detected, could I deactivate the Primary PLC Modbus port 2 and enable the Secondary PLC Modbus port 2. This way I should have a redundant master and only 1 master active at a time talking to the sensors and devices.
Will this work? am I barking up the wrong tree? am i missing some key info? I am not so familiar with Modbus as I have been mainly using Ethernet IP for the past 4 years.
Kind Regards,
Wirelessliquid