SLC to Compact or Controllogix?

[Tobi 0]

We currently have all SLC 5/05 with a few MicroLogix 1100 and 1400 all are connect to an Ethernet network and our SCADA software is RSView32. We are currently in the planning stage of adding a new plant process and I am thinking this would be a good time to start migrating away from the SLC and to one of the Logix PLCs. In most cases we have one PLC for every major machine or process, so there will not be large amounts of I/O for any one PLC. The entire plant process is a wastewater treatment plant so there is not a need for any advance functionality. The SLCs have been more than adequate for everything we have ever needed to do. We do have about seven CompactLogix at a separate water treatment plant and have been satisfied with them so far. Our consultant has recommend the ContolLogix but from what I have read and seen this will be overkill for what wee need to do. It appears the CompactLogix are a little bit cheaper than the SLCs and quite a bit cheaper than the ControlLogix. I know there is some benefits to the ControlLogix platform like the ability to hot swap I/O but really in our process this is not critical. I like to try and look at this as if this was my money what would I spend it on, since ultimately this is public money. Any thoughts or suggestions about the advantages or disadvantages of either would be appreciated.

[Chris Elston 79]

For small machine I/O I am a BIG FAN for Compact Logix L35E. You get an ethernet port "ethernet I/P", expandable rack. If you don't need motion the L35E is a sweet deal. I agree that Control Logix can be over kill for smaller machines. Or if you don't have motion, or the need for multi layers of communications. You can do motion with an L43 Compact Logix, but for straight up digital I/O, you don't need it. I would recommend the L35E Compact Logix. My favorite still today cost to performance wise, and I get to use RS logix 5000 software, which is killer compared to Rs Logix 500 software. User Define Tags in RS Logix 5000 saves me soooo much time, it's not even funny.

[rslam 1]

I would recommend the compactlogix, on the Controllogix you have always a backplane, from 4 till (I think) 10 cards, bij de compactlogix you only take the place you need. If you doesn't use the protocol DH+, i think its the best to use the compact. The switch to is quite easy, there are many programs to switch from slc to RSlogix5000. Even the RSview 32 is not so hard to switch to the visual studio. Succes with your choice.

[JRoss 84]

If CompactLogix has the speed and I/O count for the application, then by all means go for it. The only hesitation might be if you need to add capability later that would need the ControlLogix, such as coordinated motion, high I/O counts, lots of communications options... But I doubt you'll be adding much to a wastewater control machine, so you won't need that much expandability. As far as the additional features of the ControlLogix, simple applications don't really benefit. For example, hot-swapping is nice, but not usuallly necessary. I usually have to shut down all processes on a PLC anyway before swapping cards, for the simple reasons that yanking an I/O card can have unforeseen affects on the machine! So I like to power down anyway, if I can.