PLC5 upgrade to Control Logix

Hello Gents,

I'm tasked with preparing the replacement of our current "fleet" of PLC5's with something modern and we're going with the Control Logix platform for it.

I tried the conversion tool on RS Logix 20.01 to convert one PLC5 project to RSLogix and the result wasn't very good. There were some platform dependent errors that I was expecting, but the conversion basically creates a tag array with the N, F, B file types and unloading the code in a routine that is then ran at a set rate of 500ms with a timer to trigger it.

One issue the original code has is that whoever commented it wasn't descriptive and I am starting from a poorly commented code and with very few variable names/descriptions that make sense.

Has anyone done this conversion with a more recent tool of the code converter? And for the ones familiar with the AB platform, what would be your advice for this replacement?

Well, I would not have chosen V20.01 for a start....there were issues with that version and then V20.03, that they brought out V20.04 eventually to resolve the issues..

The conversion tool is not perfect and leaves you with a number of statements as "check this" and "check that" as there are certain items it will not convert fully.

I suppose it depends on how complex your hardware and programme is, but we have used it a couple of times and it needs work done, but it covers the basics, and leaves legacy references to old data files - which our guys like as they can then refer to the "old system", to the bits they knew and tweaked...sometimes I have caught them running the offline PLC5 program alongside the new Studio5000 programme, so they can relate the new to the familiar.

I have a great number of upgrades to plan for, and I was planning on using the tool to start me off. I also have Panelviews and drives to upgrade.
So trying times ahead......

Yes I have worked on a PLC5 to Controllogix conversion project before. It was about 5 years ago so I forget the details. We started by using the RSLogix5 to RSLogix5000 software converter, after that a lot of logic still had to be rewritten (changing tag names like "N7" to more understandable tag names etc). Pretty much the issues you describe. We also used these converter cables to avoid rewiring, see info below. This may be something to consider.

The I/O Conversion System includes:
• Conversion Modules (Ex: Cat No: 1492-CM1771-LD001)
• Cables (Ex: Cat No: 1492-CONACAB005X)
• Conversion Mounting Assembly (Ex: Cat No: 1492-MUA4-A13-A17)

http://literature.rockwellautomation.com/idc/groups/literature/documents/sg/1492-sg121_-en-p.pdf

Yes, I am quite a fan of the migration kit - used in on 3 full 1771 racks so far, all full of 32 channel digitals with blue panel wire, unmarked...

only issue we had with one of the digital output converters was the fact that there are 4 fuses on the converter, and one of them blew during comissioning. These fuses are not a Rockwell part, and Routeco could not get them for us. They are a "LittelFuse", and we finally sourced some through Farnell from the USA.

Changeover of each of the racks took about half a day maximum, whereas our near neighbours went for the total rewire route, and it took them much longer...

We have a couple of L55 and one L61 that are both obsolete now and a whole bunch of PLC5/40. Considering that all are obsolete, my take would be to upgrade to the latest RSLogix (or RSStudio) and start from there. 20.01 is what I have available at the moment.

I've went through Rockwell's documentation on how to upgrade and we'll most likely go with those rack adapters. One thing that will happen is consolidating processes in one PLC, what is now 2 PLC's will fit in one.

To be honest, I find the software on these really cryptic as most of the bits used have no description, there is a lot of logic for the remote IOs on DH+ that are just as cryptic. Hence why I don't want to go down the code conversion route as I'll then have to support something even more alien to me when we could have a program in place with proper comments and some of the newer features of the PLC (like AOIs).

I was just wondering if the results would be better with a more modern version, but guess not.

As for the complexity of the process, I don't think it's that complex (apart from adjusting the PID blocks) to translate. The only problem would really be understanding what and how it was programmed in the first place.

Any other tips?

I suppose it depends then what processor you are heading for....

if you future proof with the L81 series, then I think you will need the latest version, if it is an L71 series, then we are happy with V24 at the moment, as that captures our needs regarding hardware, although corporate want us to do a project (replacing 3x PLC5/80C processors) with an L81, so we will need version 30....

The Hardware upgrade is straightforward with the rack adapters, you will lose your 1771 wiring arms as they are needed. Some say that is a potential failure point, and the last project we never fully converted all the cores, so had to take it partly apart again to complete the wiring.

L55/L61 may be obsolete, but still very usable, depends what you are needing done. We had to update an L55 to an L71, due to issues with adding a Wonderware 2014 system which started giving serious memory errors on the PLC. The upgrade did fix it.

On one system we did buy 1756DHRIO cards to communicate with the RIO Flex racks, which works fine, but then we have many 1794-RIO adapters spare from another upgrade. I do want to upgrade these to Ethernet racks at some point, but require to check cable lengths as some of our RIO racks are scattered about the site

I suppose it comes down to the planning of what you need. See what you have and what you need.

Combining 2 PLCs into one is fine, we made sure the logic was separated in the new PLC so that the guys could follow what was done, although prefixing the tags can sometimes be confusing for them.

cardosocea,

As was already pointed out, version 20.01 has issues.
before even starting to upgrade the plc, I would upgrade the software first
to avoid an issues in that software version. if you use version 20.01, and then upgrade to a newer software version, you will then have to deal with the program issues in version 20.01 that were corrected.

Note that the L8X processor with Ethernet requires logix 5000 studio and is version 30 if memory serves me correctly.

james

James Mcquade said:

cardosocea,

As was already pointed out, version 20.01 has issues.
before even starting to upgrade the plc, I would upgrade the software first
to avoid an issues in that software version. if you use version 20.01, and then upgrade to a newer software version, you will then have to deal with the program issues in version 20.01 that were corrected.

Note that the L8X processor with Ethernet requires logix 5000 studio and is version 30 if memory serves me correctly.

james

Click to expand...

Thanks.
I'm downloading the latest and greatest today as I've only today been informed that we have a support contract that should cover the RSLogix license upgrade.

I had a chat about it with the colleague that was in charge of the software and knows who wrote it 20 or so years ago and he agrees that it's not well documented and the process the guy followed, although logical at a time is not so easy to figure out due to the lack of documentation.
However, one thing he did highlight was that at least he was consistent in how stuff was written, so I have to crack the first one and the others should follow.

James Mcquade said:

Note that the L8X processor with Ethernet requires logix 5000 studio and is version 30 if memory serves me correctly.

james

Click to expand...

L81E and L83E processors will run v28 if you want a version that's had a little more time on the market. I haven't ran into any major issues with v30 yet though.

cardosocea said:

Hello Gents,

... but the conversion basically creates a tag array with the N, F, B file types and unloading the code in a routine that is then ran at a set rate of 500ms with a timer to trigger it.

Click to expand...

Not real way of getting around that, it's mimicking the structure of a PLC5 as it has no other reference.

cardosocea said:

One issue the original code has is that whoever commented it wasn't descriptive and I am starting from a poorly commented code and with very few variable names/descriptions that make sense.

Click to expand...

Pretty common.

cardosocea said:

Has anyone done this conversion with a more recent tool of the code converter? And for the ones familiar with the AB platform, what would be your advice for this replacement?

Click to expand...

Code converter can only do so much, and with your situation I'm not sure what you are really expecting. Converting something that is already ~15-20 years old onto modern hardware, well cheap is what you get. My personal option, start re-writing it all together with modern practices. Not always an option as it will impact HMI/SCADA systems and such. Plus management always thinks it's too expensive as is.

Paully's5.0 said:

My personal option, start re-writing it all together with modern practices. Not always an option as it will impact HMI/SCADA systems and such. Plus management always thinks it's too expensive as is.

Click to expand...

This is my opinion too. The SCADA side of things should be easier as I can export the tags for that one area, convert the address in Excel, configure the driver to link to the new PLC and import the modified tags.

Actually, it can be even easier than that. You didn't mention what HMI you are using. If you are using FTView then its objects connect directly to tags in the ControlLogix. There are very few tags created in the HMI.

One issue I have with the conversion modules on old PLC-5 systems is: It forces you to use the exact same IO layout as the old PLC-5. Do you really want 8-point digital input cards in your new ControlLogix system?

mellis said:

Actually, it can be even easier than that. You didn't mention what HMI you are using. If you are using FTView then its objects connect directly to tags in the ControlLogix. There are very few tags created in the HMI.

One issue I have with the conversion modules on old PLC-5 systems is: It forces you to use the exact same IO layout as the old PLC-5. Do you really want 8-point digital input cards in your new ControlLogix system?

Click to expand...

We're using iFix. As long as I keep the same tag names, the driver will take care of the translation to the PLC. As much as I wanted to put the tagnames matching (as much as possible) between PLC and HMI, that would be a fairly big task to fix the images.

About the IO, I still need to check what is actually installed after 30 years with little drawing updates and decide on it. Since one PLC will cover the job of quite a few current ones, we'll have remote IO modules replacing current IO racks.

I've done the hardware conversion both ways- with the adapters and without. I prefer without. The PLC5 is taller than a CLX so you're left with plenty of extra wire length. And the end result is much cleaner, basically a brand new install with no new failure points and no ugly PLC5 rack sticking way out. It really didn't take much longer to wire directly to the new CLX modules.

Also, we had an issue once where we received a bad batch of conversion cables- one conductor was missing from each module! Took a while to figure that one out!

rupej said:

I've done the hardware conversion both ways- with the adapters and without. I prefer without. The PLC5 is taller than a CLX so you're left with plenty of extra wire length. And the end result is much cleaner, basically a brand new install with no new failure points and no ugly PLC5 rack sticking way out. It really didn't take much longer to wire directly to the new CLX modules.

Click to expand...

That's a good point. I believe Rockwell's guide to migrating mentioned something about using the adapters to speed up migration and breaking it in chunks to reduce downtime. I also believe they recommended at the end to remove the adapters as the rest of the system had been proven and then the final step would be cleaning up the installation.

Thanks for your input.