PLC5 to Control Logix

[Matt the Canuck]

Hello All,
I am new to the forum.

I am part of a group upgrading PLC5 equipment to Control Logix. We have just started the upgrades and are looking for some different options.

One of the options we are looking at is taking a group of 3 PLC5/40 processors, that are currently in 16 slot racks that are full, just digital I/O, no analogue, and using a single 1756-L72 processor to control the racks. We would pull the 5/40 processors and install ASB's in the short term, and use 1756-RIO cards in the Control Logix rack.

My concern is that that the process is extremely time critical. I worry that the RIO network would not be fast enough to control the I/O in the racks compared to having its own processor doing this. Much of the I/O is hardwired to other pieces of equipment to achieve interlocking.
Does any one have ay experience with this? Any idea how to calculate RIO network times for a situation like this?

Thanks in advance for any "input"

 

[JaxGTO]

You should use the ControlNet adapter 1771-ACN15 rather then RIO. It's much faster and has other nice features for increasing speed and thru-put. I normally don't use ControlNet, but for your setup I would say it the better option. But they may not sell it anymore. I know they are phasing out the PLC5 cards.

*Update* I just put it in Proposal Works and it doesn't give a price, so it may not be an option. You may be stuck with 256K baud RIO. Contact your local distributor and see if they can still get it. Maybe talk to your local AB PLC Specialist to see if anything new is out that may help. If you turn in the old PLC5's they may cut you a break on the new hardware.

 

[Firejo]

This might be a better way to go. It’s going to cost more because you’ll have to buy I/O cards for the ControlLogix but speed will no longer be an issue and you’re not relying on old technology. The I/O cards you have now have to be at least a decade or two old and at some point in time will fail. When they do you may not be able to replace them so getting rid of them now, when you are changing things out anyway might make more sense.
http://www.ab.com/en/epub/catalogs/12768/229240/229268/10941496/9657432/Introduction.html

 

[Firejo]

So the more I look at this system the more I’m impressed. Basically you pull the old PLC5 out (leaving the wiring connected to the I/O plugs), mount the base plate, attached the adaptors to the base plate, plug the wiring connectors that plugged into the PLC5’s I/O, install the cover plat and then mount the ControlLogix to the cover plate.
http://www.ces-pasco.com/uploads/7/7/5/4/77541368/io_modules.pdf

 

[JaxGTO]

So the more I look at this system the more I’m impressed. Basically you pull the old PLC5 out (leaving the wiring connected to the I/O plugs), mount the base plate, attached the adaptors to the base plate, plug the wiring connectors that plugged into the PLC5’s I/O, install the cover plat and then mount the ControlLogix to the cover plate.
http://www.ces-pasco.com/uploads/7/7/5/4/77541368/io_modules.pdf

I have used that system a couple of times now. The only problem with it is if the original IO cards were not wired to terminal blocks and there are unused point. It gets very hard to add them later because they are now behind the new PLC. So if you use it make sure all of the spare points are wired to spare terminals.

 

[Paullys50]

So the more I look at this system the more I’m impressed. Basically you pull the old PLC5 out (leaving the wiring connected to the I/O plugs), mount the base plate, attached the adaptors to the base plate, plug the wiring connectors that plugged into the PLC5’s I/O, install the cover plat and then mount the ControlLogix to the cover plate.
http://www.ces-pasco.com/uploads/7/7/5/4/77541368/io_modules.pdf

Meh...I looked at it years ago and found I could replace PLC5 racks w/PointIO racks within the same footprint. Saved a bunch of money on hardware and labor increase wasn't much more. Plus this system doesn't work if your panels aren't deep enough.

I can't say I'd agree on the ControlNet suggestion because of the install requirement, maybe if you pull Ethernet at the same time to prep for future migration, but if you're doing that I'd just rip it all out at once. RIO was a PLC5 staple, unfortunately the ControlLogix isn't as capable in that regard. However my experience is only with the 1756-DHRIO card, perhaps a call to AB to see if the 1756-RIO card is a better performer.

With out applications specifics, hard for any of us to give you much feedback.

 

[Matt the Canuck]

We have used the conversion hardware a few times now and it does work well, very quick and easy to do the conversion.
Maintenance hates it though, the can no longer see the wire tag on the wire, or easily drop a meter on the I/o point with the wire label to measure.

 

[Firejo]

Meh...I looked at it years ago and found I could replace PLC5 racks w/PointIO racks within the same footprint. Saved a bunch of money on hardware and labor increase wasn't much more.

The primary concern is latency I.E. how much will be introduced by using RIO. Using the adaptors eliminates the latency issue. It might not be a problem with RIO but that’s why he’s asking.

 

[Ken Roach]

The 1771 ControlNet adapters (1771-ACN15 and 1771-ACNR15) were discontinued in July 2012. The 1771-ASB RIO adapter is scheduled to be discontinued in December 2013.

Both are available on the aftermarket.

The basic rule of thumb for RIO network scantime depends on the data rate:

Full Rack at 57.6 kb/s: 10 milliseconds
Full Rack at 115.2 kb/s: 7 milliseconds
Full Rack at 230.4 kb/s: 3 milliseconds

So using a 1771-DHRIO could scan those four racks in a minimum of 12 milliseconds.

A ControlNet adapter could happily do it in 2 ms.

I think that it would be wise to do some good analysis on exactly how fast "very time critical is", and consider migrating those chassis to modern 1756 series I/O.

 

[Paullys50]

The primary concern is latency I.E. how much will be introduced by using RIO. Using the adaptors eliminates the latency issue. It might not be a problem with RIO but that’s why he’s asking.

But that doesn't allow the OP to consolidate processors which is what is driving RIO option and subsequent latency question. 1 processor with ASB adaptors. Thankfully Ken's wisdom provides the OP a measurement reference which he can decide if it is fast enough for the system. From what I have read both the 1756-DHRIO and 1756-RIO card will meet the performance level of a PLC5 using RIO assuming guidelines are followed. Of course the OP has to remember to change the RPI settings from default

If the RIO speeds Ken listed aren't good enough, then yes the OP probably has to do a direct replacement and cannot consolidate processors.

 

[DHoltman]

I have used that system a couple of times now. The only problem with it is if the original IO cards were not wired to terminal blocks and there are unused point. It gets very hard to add them later because they are now behind the new PLC. So if you use it make sure all of the spare points are wired to spare terminals.

Be aware that some of the ControlLogix cards originally designed for this conversion system are now listed as obsolete, including:

1756-IT6I2 (replacement for 1771-IXHR & 1756-IXE)
1756-OF6VI (replacement for 1771-OFE)
1756-IF6CIS (replacement for 1771-NIS)
1756-OF6CI (replacement for 1771-OFE2 and 1771-NOC)