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Old October 16th, 2020, 04:02 PM   #1
RonJohn
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PLC5 adaptor mode conversion to Logix

I have experience with converting PLC5 to Logix but this system has two PLC5s, one of which is used in adaptor mode. I'm wondering if someone here can help me figure out what needs done differently here.

The PLCs were originally the classic series (5/15, 5/25, etc.) since upgraded to a 5/80s with Ethernet side car. The Adaptor PLC5 was added in a remote rack containing nine total analog input & output modules and handles over a dozen PID loops because the original Scanner PLC5 didn't have the horsepower to handle all of the block transfers & PIDs, so I've been told.

We aren't granted a lot of time for changeover, so the 1771 IO stays put and the new Logix rack contains a processor, EN2T & one or more DHRIO cards. On other projects, we would install the PLC5 in a standalone rack, put an ASB in the old rack 0 and renumber it before converting the program. This way we don't have to worry about address differences and downtime is reduced. Not sure this will work with so many analog cards in one rack!

Any insights on how to address this dilemma and the Adaptor PLC in general will be greatly appreciated. Thanks in advance.
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Old October 16th, 2020, 04:17 PM   #2
Ken Roach
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Carefully re-addressing data tables and I/O modules is going to be necessary anyhow; I don't think that the old "Adapter 0" method to avoid re-labeling wires is really going to be helpful.

Even with multiple DHRIO modules and the modern L7x and L8x controllers, the capacity of the ControlLogix to handle RIO block transfers through the 17560-DHRIO remains (as far as I know) the ancient 16 module limit.

So my first suggestion is to use the 1756-RIO or the AN-X EtherNet/IP to RIO bridge, instead of 1756-DHRIO modules. Those handle block transfers onboard, rather than using the ControlLogix CPU's buffers and connections.

They also support "Ghost Mode", which would be more useful if you had analog I/O all talking to one PLC-5/80E rather than the blocks transfers between PLC5s.

Lots of graph paper, limber Microsoft Excel macro fingers, and a strong pot of coffee.
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Old October 16th, 2020, 04:47 PM   #3
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Ken, thanks as always for the rapid response! You've given me a lot to chew on...

So, I investigated the 1756-RIO module about 5 years ago but never used one (an A-B tech talked me into a DHRIO for that particular conversion). Are you saying the RIO can handle multiple BTs simultaneously to a remote rack? That seems to be the hang up I've seen in the past with the DHRIO, where we had to multiplex the block transfers within a particular ASB.

I'm not familiar with Ghost mode. Is that spelled out in the RIO manual or elsewhere? I'd say we're game for using one or two L8xE processors for this conversion as that seems to be our new standard.

The Scanner PLC does have block transfers to other analog modules & VFDs but they don't appear to be as time sensitive as the ones for PIDs. Of course, that may simply be what I was told.
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Old October 16th, 2020, 06:09 PM   #4
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It's been a while since I did one of these, probably ten years. My big screwup was not paying close attention to the PID trigger logic, which was basically running by coincidence because the PLC-5 scantime was roughly the same as the loop update time.

It's my understanding that the limitation for the 1756-DHRIO was in the type of connections across the backplane to a ControlLogix CPU that can be used for a BTR or BTW, rather than the block transfers on the wire, or between the 1771-ASB and the 1771 modules. You could do up to sixteen total, but if you needed more BT instructions, after that you had to stagger them.

The 1756-RIO instead handles the block transfers onboard, and uses ordinary big 1756 backplane connections to move that data to the ControlLogix.

The 1756-RIO and the AN-X are the same RIO circuits and basic hardware, with a different ControlLogix interface. QTS in Florida built them, and eventually settled on using Rockwell and Prosoft (respectively) for their sales and support channel.

"Ghost" isn't a word that actually appears in the literature; it's called "Monitor" mode.

That allowed us to listen to the Input and Output data, both discrete and block transfer, and run our ControlLogix program silently listening to the inputs. We then compared our outputs to the outputs that were actually going across the wire.

But frankly, we never did enough of the listening and comparing to benefit from it. The project timeline moved up, HMI migration took away resources, there was a snowstorm... you know the drill.

Get the 1756-RIO user manual and browse the Knowledgebase. Even if Monitor Mode doesn't help you, it's definitely the module that you want to base your architecture on if there are many block transfers on RIO.
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Old October 17th, 2020, 12:47 PM   #5
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Have you looked at PLC5 to ControlLogic conversion systems to save installation time? Unplug the swing arms, swap the rack, plug in the swing arms. Hang the 1756 rack and plug in. Fast way to all modern hardware.

https://literature.rockwellautomatio...g121_-en-p.pdf

You will need OEM or Gateway level RSLinx license to setup the 1756-RIO.
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Old Yesterday, 02:33 PM   #6
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Quote:
Originally Posted by 5618 View Post
Have you looked at PLC5 to ControlLogic conversion systems to save installation time? Unplug the swing arms, swap the rack, plug in the swing arms. Hang the 1756 rack and plug in. Fast way to all modern hardware.
Thanks for the reply. I had seen these before back in my integrator days and wasn't a big fan of the terminations buried behind the Logix rack. Not sure the enclosure is not quite deep enough, however, this may be worth another visit.

Quote:
Originally Posted by 5618 View Post
You will need OEM or Gateway level RSLinx license to setup the 1756-RIO.
I don't believe I was aware of that. Will check it out.
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