Upgrading PLC2 to ....?

Electrically_Bound · Jan 31, 2008

We have got a couple on Mini-PLC2/16s in our facility that I would like to get rid of. Each of these PLC2s have approximately 40 discrete I/O points on them and the programs are under 100 rungs. These PLCs are located less than 100 feet away from a PLC5 that already uses several remote I/O racks. The program that resides in the PLC5 is very "messy" since it was converted from a PLC-3 and it contains a lot of unused code (I have not yet had time to clean it up). Some think that I should just turn the PLC2s into I/O racks by using an remote I/O adapter card and put their programs in the cluttered PLC5. I'm actually partial to replace each of these PLC2s with a Micrologix 1100 since I've already installed 3 of them. I would just need to add a couple AC input and AC output cards to each of them. What is the best and cheapest solution?

surferb · Jan 31, 2008

Ok - pay attention! I have some red legos, some blue legos, and a pile tinker toys. I need to fortify 3 GI Joe soldiers. What's the best and cheapest way to do so?

Well, it depends on your requirements and what you're comfortable with. How safely and efficiently can you re-write the program? Do you have any particular need for central logic or are you OK "stovepiping"? What will your future requirements be?

I get the feeling that you already fully understand the implications of your proposed design options. What you should know (and we don't) are your plant and requirements. Am I wrong?

Electrically_Bound said:
We have got a couple on Mini-PLC2/16s in our facility that I would like to get rid of. Each of these PLC2s have approximately 40 discrete I/O points on them and the programs are under 100 rungs. These PLCs are located less than 100 feet away from a PLC5 that already uses several remote I/O racks. The program that resides in the PLC5 is very "messy" since it was converted from a PLC-3 and it contains a lot of unused code (I have not yet had time to clean it up). Some think that I should just turn the PLC2s into I/O racks by using an remote I/O adapter card and put their programs in the cluttered PLC5. I'm actually partial to replace each of these PLC2s with a Micrologix 1100 since I've already installed 3 of them. I would just need to add a couple AC input and AC output cards to each of them. What is the best and cheapest solution?

dadalex · Jan 31, 2008

I worked for Rockwell for several years and have been in your situations on several occasions. I have implemented both so here are what I see as the advantages and disadvantages to both.

Convert to Remote I/O advantages: all programming is centrally located and easy to coordinate control between machines, simple programming Disadvantages: lots of time figuring out what code is there already and writing around it plus time spent cleaning up existing code.

Use MicroLogix (I did this before MicroLogix was out and used SLC but essentially the same methodology) Advantages: fairly quick turn around on programming, easy install with smaller footprint in the future you can network all the controllers to communicate Disadvantages: Slow update between machines when networked - this is relative because 1 to a few second may be fine in some applications.

Also consider cost. The 1100 is pretty cheap compared to buying the I/O adapter for your PLC2 and the I/O on the PLC is essentially an antique.

tomalbright · Jan 31, 2008

Change 'em. Even rewriting the programming in these will have to be done, but as you say, not big deals! Only thing to think about, is what comm do you have with these, and can it be upgraded?

Hint: Ethernet!

Electrically_Bound · Jan 31, 2008

Thanks dadalex and tomalbright for your replies. I think that I am going to push for the ML1100 solution. I should have mentioned that the the mini-PLC-2/16s are located adjacent to the equipment that it controls and that putting a ML1100 in the same place would aid in troubleshooting. If I put the programs in the PLC5 then the technicians would be about 100 feet from the action. The ML1100 have ethernet built into them so it would make it simple and inexpensive to network them and perhaps lay the groundwork for remote monitoring and troubleshooting. And I guess that getting away from the antique I/O is yet another major advantage.

Upgrading PLC2 to ....?

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