DVC72680

PLC5 to Controllogix Tricks?

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I have to replace a PLC5 with a new 1756-L73. There are (3) panels involved in system. The main panel controls (2) other panels remotely via each their own 1771-ASB module. Time is of the essence on this project so I am trying to find ways to reduce the required downtime needed to make the switch over. I am going with AB's new conversion method of using the existing swing arms assemblies into a mounting adapter then the c-logix rack on top of that.

Question - Can I convert the (2) remote panels first or can they only be done once the main panel with the PLC has been converted over? The remotes only have input & output cards in them.

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By doing the remote panels first, do you mean have the PLC-5 control the 1756 I/O? If so, I'm pretty sure that won't work. It *may* be possible for the DHRIO module to have routing tables set up inside it so it emulates an -ASB module, but I don't know if that's going to gain you much.

If you're ok with keeping the remote racks as-is, you can use a 1756-DHRIO in the home chassis to control the remotes via RIO. That would get you a quick upgrade of the CPU and its home chassis but would leave the existing 1771 I/O in place.

We did an upgrade not too long ago (a couple of years) that's similar to yours. We had a PLC-5 in its home chassis with 6 remote chassis on RIO. We replaced the 6 remote 1771 racks with 3 1756 racks and a FLEX I/O rack, all on Ethernet/IP. We saw the wiring kits you're talking about and decided not to try them. It added some time to our conversion, but I don't remember it being excessive. The wiring conversion kits will introduce extra wiring points that will be inaccessible for diagnostics (can't probe them with a meter since they're behind the 1756 chassis). If time is that much of a premium, that may not matter as much.

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You definitely cannot control 1756 ControlLogix I/O modules with a PLC-5 controller.   

You could leave the 1771 chassis in place with the RIO network cable, and convert to a ControlLogix CPU, using the 1756-DHRIO or 1756-RIO as your RIO scanner.     That would end up costing more in time and effort over the long run because you would have to convert and test your program with a 1771 I/O architecture, then change it to a 1756 I/O architecture later.

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