Compact logix with 20 remote I/O Ethernet Network

[ALI PLC 0]

Dear Friend I would like to controlled 20 Filter backwashing station by using 1 PLC type 1769-L36E with accepted 48 Node connections I planning to use 1734-AENTR for each node each node will be include 1 1734-AENTR 4 1734-IB8 2 1734-OB8 1 1734-IE2C My problem I needs to connect 20 HMI to Main PLC adding to 1 main HMI thats mean I will have 41 Nodes , Is that large number of nodes will effect the PLC processor ? I needs your advice Best Regards Ali Edited 27 Jun 2014 by ALI PLC

[ASForrest 12]

Hi Ali and welcome to the forums I don't think that setup will work for you. While you're correct that the L36 processor can have up to 48 nodes, a "node" is not quite as simple as how many devices you have plugged in. Take the example of one point i/o rack with 2x 1734-IB8 and 2x 1734-OB8. If you create a module connection to this rack, it would take up 4 nodes, one for each card. But there is another option - use Rack Optimisation. This effectively causes the PLC to look at the rack as one device, and read the whole thing in one go. So it becomes one node. The only problem is that you can't use Rack Optimisation for analog cards. Each of those would have to be a Module Connection. I'm not 100% sure, but I believe that you can set up a rack so that it reads all the digital I/O as one node on rack optimisation, and then reads the analog cards separately. I'm sure someone else here can explain more fully, but if you can do it that way, that would mean you would have 3 nodes at each station: a rack optimised connection for your digital I/O, a module connection to your analog input, and a third connection for your HMI. This would make for a total of 60 nodes, which is too much for any Compact Logix. To talk to that many devices you're going to have to go to a ControlLogix. The ControlLogix can pretty well have as many nodes as you want - if you need more you can just add another network card. Just be aware that the different network cards give you different amounts of nodes - the 1756-EBNT for example gives you 128 EtherNet/IP or 64 TCP. I'm not sure of what the difference between TCP and EtherNet IP is, but if someone who knows more about this than I do says that all your connections are TCP, well, with 60 nodes already accounted for, I'd be going for the next card up to give yourself some headroom. As far as processing power to drive that many nodes, I wouldn't presume to guess - I've never seen a setup with that many HMI's and I/O hanging off it. Chances are that somebody here has though, so hang around and hopefully someone else will be able to fill in the gaps that I've left :)

[Ken Roach 194]

What exact model of HMI are you using ? How much data do you need to exchange with the HMI ? 20 remote I/O nodes is within the capacity of a CompactLogix, but 20 HMI's may be too much. If these are PanelView Plus HMIs, they can establish up to five CIP connections each, which might overload the CompactLogix. If they're Red Lion G3's, they could form an I/O connection that would minimize the amount of unscheduled connections and buffer performance required.