PLC5 to Control Logix Conversion

KerryP

Member
Join Date
Dec 2010
Location
Urbana, IL
Posts
40
I’m preparing to decommission a PLC5 and replace it with Control Logix. This is a core process in our plant and there is no margin for downtime whatsoever. My best opportunity for availability will be in July when we have a bunch of 3 and 4 day weekends of downtime.

I’ve done this conversion a couple of times in the past with small systems and, after seeing the conversion results, ended up writing a new program for the CLX. I just ran the 58,000 words of PLC5 program through the converter and it is not pretty. The conversion results are an insult to the possibilities of Control Logix programming.

The existing architecture is a PLC5/80 Enhanced with 5 17-slot racks and a couple of PanelViews and a couple of PF70 drives on RIO. In addition there is an iFIX 32 HMI PC on DH+. I have recently installed the CLX with an ENBT and a DH/RIO. The CLX is reading new Ethernet IP laser rangefinders for the transport hoists and messaging the position data to the PLC5 over a DH+ channel that only has the two processors on it. The PLC5 is still doing all of the control. The ultimate goal here is to replace the PLC5 with a 1771-ASB. Replacing the 1771 I/O will happen in the next 3 to 5 years.

1. I think my first question is RIO sharing. Can I connect the CLX to the PLC5’s RIO channel? This would allow something of an incremental approach. I could write small chunks of CLX code and bring them on line one bit, one card, one VFD, or one rack at a time. I’ve reviewed the literature and some forums and I’m still not sure what is possible. The second option for the incremental approach would be ‘node-at-a-time’ by unplugging a node from PLC5 and connecting it to CLX.

2. My next question is about the “conversion”. I’ve never been happy with the results of a direct PLC/SLC to CLX converted program. Am I being prissy here? In the present case I have several thousand tags with names like I_002_Bit15 instead of LS-2711. I have not figured out how to get the address/instruction descriptions to convert and there are literally only about 20 symbols in the PLC5. Right now, the converted program in the Control Logix is 99.5% undocumented, no tag descriptions and no rung comments. Has anyone of you ever been pleased with this process? Is there a way to get all of the address/instruction descriptions or rung comments into the CLX that I am missing? I am using v19 of RSLogix 5000.

3. Finally, what am I going to do with this iFix 32 HMI? The data base is like 6,000 tags. I have the ‘Ghosted’ backup PC at my desk and I’ve been looking at the ABR driver configuration a little bit. The existing system is on DH+ and I would like to use Ethernet just to eliminate the cost/risk of the DH+ adapter in the PC. So far it looks like a tedious, manual database editing project to re-address the tags to CLX data, if it will work at all. Any suggestions?

Once again, I thank all of you in advance for any input whatsoever. In the recent past you helped keep me on the right path with those laser rangefinders on my transport hoists by affirming my approach. That project was successful and relatively painless and I have to give you guys credit.
 
I miss O'Malley's.

Thanks for the detailed post !

I did a project very similar to yours last winter, converting a PLC-5/80 to ControlLogix. We ended up spending about two man-months on it and did the switchover in five hours; twenty minutes for the switchover and four and a half hours hunting the final bugs.

The star of the conversion was a 1756-RIO module. Not the classic 1756-DHRIO; the 1756-RIO is based on a design from Quest Technical Systems in Florida (www.qtsusa.com). Quest sells a standalone EtherNet/IP to RIO module and the 1756-RIO has the same features but is integrated into the ControlLogix backplane and tied into RSLogix 5000.

The key features of the 1756-RIO are onboard block-transfer processing and "Ghost Mode".

Onboard block-transfer processing is important when you're doing a large RIO and DH+ system because of the native limits of RIO and DH+ messaging on the ControlLogix CPU itself. The rule of thumb is that you max out the Block Transfer messaging resources with just 16 analog modules (I can go into depth). With onboard block transfer processing inside the 1756-RIO module, there is no pre-set limit to Block Transfers. Our system had 30 analog modules, mixed among 1771, 1747, and 1794 adapters.

Ghost mode is what lets you do this conversion over time rather than in three screaming days in July. The 1756-RIO connects to the RIO network and listens to the Input and Output data as well as all of the Block Transfers. The best way to configure it is to take time for a system reboot and let the RIO module listen to the I/O connections getting set up, as well as all the block transfers executing. Many block transfer modules are configured to only send a BTW for configuration on power cycle, for example. If you are careful and thorough you can set up Ghost Mode by hand.

When you're running in Ghost Mode, you can observe and trend (or write logic to track) the difference between the results of the ControlLogix code and the results of the PLC-5 code, because you're seeing the PLC-5 output data tables in real time in the ControlLogix tag database.

That's one of the things I could have done better on that project. We scrubbed one switchover attempt because we couldn't get the PID tuning right. I had not carefully examined the PID configurations in the PLC-5 or compared their performance to the ControlLogix PID and several common issues with scantime versus Update Time bit us. If I had spent more time examining the PID instructions, or had run trends to compare the output of the ControlLogix instruction to the output of the PLC-5 instruction in ghost mode, I would have known about those before we attempted to do the switchover.

One of my colleagues did the Wonderware conversion. Because this HMI application had grown organically over the years, there were a lot of scattered data table reads and writes, as well as direct references to the .PRE and .ACC subelements of Timer and Counter files in the PLC-5. This doesn't translate effectively to ControlLogix, so we implemented a sort of middleman integer array for those elements. It was tedious, yes.

Another aspect of our project was controller-to-controller DH+ messaging. This system was stitched together with MSG instructions sending data God-knows-where. We spent a lot of time with the Frontline Test Equipment NetDecoder software trying to figure out which other controllers were writing or reading the PLC-5/80, and finding quite a lot of "that's never worked right" or "we tore that out years ago" functions.

In my opinion, the PLC/SLC conversion program should be used only to get bulk ladder logic converted between platforms. You ought to be able to get Descriptions to associate correctly with the autoconverted tag names, but there will probably be some manual conversion as well. I spent a lot of time writing and testing scripts in UltraEdit to do database conversion and cleanup.

There is a new revision of the PLC/SLC Conversion Tool included with RSLogix 5000 v20, but it may be aimed only at the SLC-500 controllers, as v20 also includes the new 1747-AENT adapter and EDS-based Add-On Profiles for the 1746 series I/O modules.

Early on in that project we made the case for spending additional money on the 1756-RIO and on consulting services from RA for the DH+ analysis and RIO module conversion. The issues that we discovered during "ghost mode" testing included damaged I/O modules, corroded RIO wiring, abandoned but still-active DH+ interlocks, and corrupted analog module configuration blocks. Any of those could have scuttled the conversion, mostly because we would have been looking at the converted logic instead of at the infrastructure.

I strongly recommend the use of the 1756-RIO module. By the time we switched over the system, the managers were congratulating themselves for having invested in the hardware and time up front.
 
Thanks for the detailed post !

There is a new revision of the PLC/SLC Conversion Tool included with RSLogix 5000 v20, but it may be aimed only at the SLC-500 controllers, as v20 also includes the new 1747-AENT adapter and EDS-based Add-On Profiles for the 1746 series I/O modules.

[FONT=&quot]1747-AENT eh, you might want to not mention that so openly. The last time I asked about the [/FONT][FONT=&quot]1747-AENT from my local rep I was told something about being located by their drones and that I should report to the nearest Rockwell "re-education camp". It's a myth, a legend, a figment of to many active imaginations and it's best you just keeping walking and pretend the idea never entered your mind. [/FONT]
 
[FONT=&quot]1747-AENT eh, you might want to not mention that so openly. The last time I asked about the [/FONT][FONT=&quot]1747-AENT from my local rep I was told something about being located by their drones and that I should report to the nearest Rockwell "re-education camp". It's a myth, a legend, a figment of to many active imaginations and it's best you just keeping walking and pretend the idea never entered your mind. [/FONT]

Huh? :confused:
 
All I'm saying is try searching the 1747-AENT on any Rockwell website or forum. It doesn't exist. It's kinda like the 300 mpg carburetor. Sure everyone saw one at Automation Fair, until the men in the lab coats came one night and suddenly it has just disappeared, only thing left behind are vague references of what could have been or someday might be in forums such as this.
 
Fortunately the OP doesn't have any 1746 I/O to migrate.

Maybe we should open another thread/betting pool on the shipment of that 1747 EtherNet/IP adapter.
 
Fortunately the OP doesn't have any 1746 I/O to migrate.

Maybe we should open another thread/betting pool on the shipment of that 1747 EtherNet/IP adapter.

Sounds like a good idea... other than the fact that we'll all end up with our names on a list in the cabin of some rusty old ore ship covered in cleverly disguised aerials ported somewhere in the Milwaukee Bay near West Allis WI. Then try to get one if they do come out.:rolleyes:
 
I did an upgrade last fall on a ControlLogix system from a DHRIO to a RIO card. Worked beautifully. Another more expensive option on the PLC5 system is to use ControlNet. But you would have to pull new wires and replace the adapter cards.
 
I did an upgrade last fall on a ControlLogix system from a DHRIO to a RIO card. Worked beautifully. Another more expensive option on the PLC5 system is to use ControlNet. But you would have to pull new wires and replace the adapter cards.

I am a proponent of the ControlNet. In our process (where we have done a pyramid integrator to controllogix conversion, and a subsequent project to replace the 1771 IO (rio) with 1756 (controlnet)), the IO update rates were important. There is a huge difference in the update rates that we experienced between the two bus technologies.
 
Re: the Fix32 node.. Upgrade that to iFix and get the IGS driver(or the OPC driver if you have RsLinx on the machine).
You can export the database from the Fix32 node to csv style files and modify it all at once.
 
Hey Ken,

Thanks for the tip about the 1756-RIO. Writing purchase requisition now. It looks like just the thing for this project. Once again, you rock.
 

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