Controllogix Configuration

[ECSI 17]

I am pricing a control panel with an AB Controllogix system and the IO configuration has been given to me by the customer but I'm not sure about a couple of things. The system requires approximately 22 digital IO modules. Since the biggest chassis is 17 slot, can I add a 10 slot chassis beside it to accomodate the extra modules? Is there a limit to the number of expansion racks? Also, do the expansion racks connect with a cable or with some type of communication module? I can't seem to find the answer on AB.com. Thanks Edited 8 Mar 2006 by ECSI

[jstolaruk 9]

No, the ControlLogix platform requires a little more than that. Ethernet/IP, ControlNet are two choices. For ControlLogix configuration, this is an excellent document: http://literature.rockwellautomation.com/i...sg001_-en-p.pdf Edited 8 Mar 2006 by jstolaruk

[navillusi 2]

For connection of extension racks, ControlNet is the preferred option as the backplane is classed as a "controlNet" backplane. Usual solution is to use a CNB module in each rack and connect with the proprietary cables. There is no limit to the number of racks that you can connect on controlnet, only limit is the number of connections in the processor

[TimWilborne 108]

Although from a rack point of view I would definately say there is not limit with Controlnet, there is a 99 node limit so if you start putting individual devices on the network, make sure you stay below 99. I have used Ethernet/IP to connect racks with no problems, so if the customer is already requesting an Ethernet connection, use it to also connect the racks. But one other thought, with 22 racks I'm thinking thats going to be a lot of hard wiring. Have you thought about distributed I/O?

[jstolaruk 9]

TW, please reread, he stated 22 digital I/O modules in 2 racks.

[TimWilborne 108]

I read the statement right, just posted my reply wrong With 22 I/O modules, I'm thinking thats going to be a lot of hard wiring. Have you thought about distributed I/O? Edited 8 Mar 2006 by TWControls

[ECSI 17]

Thanks everyone for the help. The system will include four control panels....the Main PLC panel and 3 remote IO panels. They are going to be networked by ethernet/IP modules. The issue I had was that two of the control panels require twenty or more IO modules so I was looking at how to add a second rack to these panels. I wasn't sure if I needed to add an ENBT module to each expansion rack or maybe there was an easier (cheaper) way to do it. I'll check out the CNB modules and cables and compare to the ENBT for pricing. Thanks for the selection guide link jstolaruk. You're right, lots of wiring, but there's no chance of distributed IO on this project. Oh well, it keeps the billable hours up!

[TimWilborne 108]

Since you are already networking the panels with Ethernet/IP it would probably more cost effective just to add a ENBT to the second chassis. Make sure you use good shielded Ethernet cable and industrial switches. Personally I like N-Trons switches

[Contr_Conn 4]

With this amount of I/o modules and racks you should definately look at controlnet. With Ethernet/Ip you may end up with 2 or more ENBT cards in the local rack to handle all I/o traffic. Plus don't forget to add cost of multiple industrial ethernet switches ($500+) each.

[ECSI 17]

yep, the design engineers already spec'd ethernet/IP and allowed for 2 ENBT's in the main rack as well as ethernet switches. The only thing they never allowed for was a second chassis in two of the panels, thats why I asked the original question. Thanks

[Contr_Conn 4]

2 ENBTs in the main rack possibly for diffrent reason: - One for I/O control, another for HMI or - One for I/O control and HMI another for plant IT network. Usually just a few people use packet/sec calculation to determine how many ENBTs necessary. RSNetworx for Ethernet can do it for you also - Yes! , we really can use this program! I usually do simple calculation: ENBT packets/sec = 2000 / RPI1 + 2000 / RPI2 + 2000 / RPI3+... All RPIs in mSec Do not exceed 4500 packet/sec per ENBT New EN2T will have 10000 pack/sec but it's 5 months away. Edited 8 Mar 2006 by Contr_Conn