PLC2/30 Upgrade

I have a PLC2/30 system and need to upgrade to later technology. I am looking at the ControlLogix solution. Now I am at the point to determine whether or not to replace the existing I/O modules. Can someone give me some pros and cons on whether or not to replace the I/O modules? Thanks.

sltan said:

I have a PLC2/30 system and need to upgrade to later technology. I am looking at the ControlLogix solution. Now I am at the point to determine whether or not to replace the existing I/O modules. Can someone give me some pros and cons on whether or not to replace the I/O modules? Thanks.

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Time and money. If you have both , then do it . If not , then use can re-use all 1771 I/O providing the racks have 1771-ASB RIO adapters. The Contrologix would connect via 1756-DHRIO card.

Next best would be to place 1771 Controlnet adapter in the 1771 I/O racks and connect using 1756-CNB on the contrologix

Ian

Curlyandshemp,

Thanks for you suggestion. Are there any downside to keep the existing I/O modules? The system have some ladder logix codes. I plan to keep the codes.

sltan said:

Curlyandshemp,

Thanks for you suggestion. Are there any downside to keep the existing I/O modules? The system have some ladder logix codes. I plan to keep the codes.

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1771 I/O is still supported, so there is no down side to keeping it. "If it ain't broke, don't fix it".

Sounds like you have been given an unlimited budget, and as much time as you need to do the conversion.

Advantage of keeping the existing I/O is realized during program development. You can schedule down time for the PLC2 and switch the RIO cable over to the Contrologix, do testing, then when finished put the RIO cable back onto the PLC2.

Every conversion I have done, this procedure has take place for about a week, during the day shift I can test and debug, and at night I can sleep peacifully knowing the original equipment is still running.


How many racks of I/O are you looking at?

Ian

I am looking at 3 racks with 22 I/O modules and about 1600 rungs of codes.

sltan said:

I am looking at 3 racks with 22 I/O modules and about 1600 rungs of codes.

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The number of rungs of code will drop by utilizing RSlogix instructions. The GET and PUT are replaced by MOV.

I have seen plenty of PLC2 code that uses an entire rung to create a One Shot which is replaced by the bit Clgx ONS.

Only issue to watch for is the PLC2 code uses OCTAL for its addressing, whereas the Contrologix uses decimal.

Ian

Thanks for your advise, curlyandshemp.

Just a few words of caution, do your homework. I think there were some issues upgrading PLC-2's to PLC-5's and having 1771 I/O racks and P7 power supplies that were the wrong rev #. There may be similar issues with PLC-2 and ControlLogix.

Get all of the #'s you can off of the existing 1771 hardware and get with Rockwell's tech support to see if it is compatible. Otherwise at startup you may be in for some surprises.

Good luck and keep us informed on how this went.

dogleg43,

I am not too clear what are the #'s on the hardware mean? Thanks.

by "#'s" he is referring to "part numbers"...get all the exact and complete part numbers from your existing system including any revision levels too.

What dogleg43 is referring to is the fact that old PLC-2 power supplies for 1771 chassis don't work when you put a PLC-5 controller into the chassis. You need a PLC-5 specific power supply. There's also a difference between the original 1771 chassis and the far more common 1771 Series B chassis.

You can find specifics details on hardware compatibility in Rockwell Knowledgebase article # 16474.

When you do your hardware inventory, be as specific as you can. A-B part numbers from the dim past can be confusing to people who are unfamiliar with them. The best thing you can do, in my opinion, is take a bunch of photos.