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Skidog

Slc 5/03 To Plc5/remote Rack Configuration

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After much complaining and foot stomping I have convinced my boss to allow me to upgrade 2 automotive stamping assembly lines. Current configuration is 6 SLC 5/03's on DH-485 for each line. New configuration will be 1 PLC5 with a scanner card and 5 adapter cards to replace the 5/03's. I'm not asking for anyone to engineer this for me, rather I was hoping to get feedback from anyone who may have done something similar in the past. I realize I'll be in front of my PC for the next few months doing find and replace operations etc, but was hoping I might avoid overlooking something incredibly simple by putting this up for discussion. I'm in my 2nd year with regards to PLC programming, installation, setup and maintenance. I've had all the AB schools for both SLC's and the PLC5. I'm not an engineer but I play one at work. :-p I already have a PLC5 and SLC rack set up in the shop to try this out. From what I have seen so far, this will work. If you disagree please speak up and post a reply. As I said, I'm still learning.

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Hi there- Sounds like a pretty fun project. It should keep you busy for a while. I have a couple of things you might want to look into/out for if you haven't already. What communication network do you plan to use from the PLC5 to the SLC racks? How much I/O is in each rack? You may need to be careful of data transfer times and I/O update rates, especially if you have any analog or specialty I/O (counter cards, thermocouple cards, etc) in the racks. If you need real speed, ControlNet is the ticket. How big are the current programs in the SLCs? What is the average scan time in the current SLCs? While a PLC5 will be somewhat faster than the current SLCs you have, it most likely isn't 6 times faster in real applications. You may end up with a pretty big scan time if you toss all this stuff together. What processor model do you plan to use (5/20, 5/40, etc)? While this won't affect your scan time it will affect available memory as well as number of remote racks you can access if you plan to use the built-in Remote I/O network. If you do run into speed issues you might want to consider ControlLogix. It means an expensive step in development software, but ControlLogix is a serious brand of FAST compared to the other AB processors. I hope this helps. Good luck, Keith

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One of the paperwork things will be the numbering system; SLC's number their I/O slots and points in decimal format, just like the rest of us 10-fingered apes do. But the PLC-5 inherited it's I/O structure from the PLC-2, so it's I/O memory for slots and bits is numbered in octal format. This makes for some re-labeling at the terminal strip. Good luck with the search-and-replace; if I were doing the project I would change the code first in RSLogix 500 to use non-conflicting addresses, then copy-and-paste it into RSLogix 5. This is one of the most crash-happy procedures RSLogix performs, so back up early and often. Hopefully your individual SLC's aren't running super-fast routines for positioning or cutting or something of that sort; that kind of function seldom survives a centralization of processing. Edited by Ken Roach

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Another caveat... I heard a story once about a 5/04 project that had used up all 64k and so they upgraded to a PLC5/80, only to find that they still had little or no memory left. The implication is that SLC code takes less memory than the equivalent PLC5 code - something to be wary of. Another thing to worry about with memory usage: on the PLC5, be miserly with allocation of program and data files. Especially don't leave huge gaps in your numbering. Each file adds 6 words of memory to "overhead" (as shown on the controller properties display). BUT, if you create a file 10 and a file 100 with nothing in between, there will be 6 words of overhead allocated for each of files 11 to 99 even though they don't exist. The SLC does not do this - gaps in SLC file numbering don't carry the memory use penalty. Hope you got a PLC5 that's big enough! Check out the possibility of using the SFC's - they can potentially reduce ladder complexity and scan times.

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