PLC 2 System Upgrade

Have a customer with a small facility with a PLC-2 based system for all discrete control. All analog inputs and outputs have their own standalone controller. There is no HMI, so all changes are to be made at the local panel.

They would like to upgrade their system, which would allow the ability to make changes on a HMI and remotely.

Since they need about 8 IO cards, the 1769-L30ER (Compactlogix) is an option. The other option is to just upgrade the Analog side and keep the PLC-2 as a remote rack. What module would be used to make it a remote rack, and what comm module would i require in the main chassis.

A Redlion HMI for Analog Controls and IO was another option perhaps, but not sure if it can communicate to a PLC-2 rack.

They don't have much $$$ to spend, so looking for options with a potential to upgrade the other components later.

It was past time to upgrade that PLC-2 twenty years ago, so take promises about "there will be more upgrade work for you later" with a grain of salt.

It's likely that their PLC-2 is in a 1771 series chassis, and you can use a 1771-ASB Remote I/O Adapter in it, and scan that with a RIO scanner. Ideally, you should do a survey of the chassis and power supply part numbers.

The CompactLogix has no chassis-resident RIO scanner like the ControlLogix does (the 1756-DHRIO and 1756-RIO). You would need to use the Prosoft AN-X EtherNet/IP to RIO bridge.


Have you ever programmed a PLC-2 ? Do you have the PLC-2 software tools and connection devices that will let you upload a known-correct program from their controller ?

Ken Roach said:

It was past time to upgrade that PLC-2 twenty years ago, so take promises about "there will be more upgrade work for you later" with a grain of salt.

It's likely that their PLC-2 is in a 1771 series chassis, and you can use a 1771-ASB Remote I/O Adapter in it, and scan that with a RIO scanner. Ideally, you should do a survey of the chassis and power supply part numbers.

The CompactLogix has no chassis-resident RIO scanner like the ControlLogix does (the 1756-DHRIO and 1756-RIO). You would need to use the Prosoft AN-X EtherNet/IP to RIO bridge.


Have you ever programmed a PLC-2 ? Do you have the PLC-2 software tools and connection devices that will let you upload a known-correct program from their controller ?

Click to expand...

Thanks for the reply Ken. No i have not programmed a PLC-2, but they did acquire the software, so i do have a copy of it and a print out of the logic.

I will have to get details on their current PLC IO, but i believe the PLC-2 processor could have been replaced by a PLC-5, but i think it is a waste of time.

Upgrading to the Compactlogix is what they should really do, but just to avoid downtime, the PLC-2 as remote rack is a thought.

You can almost certainly put a 1771-ASB in place of the PLC that's installed, and run that I/O with a 1756-DHRIO or AN-X. I believe that *any* 1771 chassis and power supply combination will support the 1771-ASB. If the chassis is a pre-1978 model, then maybe it won't work.

I'm always skeptical that the program I am given is the currently running program unless I have uploaded it myself. I have literally never received the correct matching current running program from a client, even if they believed it was current.

I've only done a couple PLC2 1771 conversions - and its been a long time since - but I seem to recall having to replace the chassis on one of them - which really surprised me at the time. So if you are keeping the chassis - do a little homework and don't just assume.

The RA Knowledgebase includes some PLC-2 conversion and FAQ documents that I don't want to accidentally contradict or inaccurately summarize.

The most useful one is KB 16474, which includes some detailed truth tables and FAQs about compatibility of power supplies, chassis, and controllers.

The core principle of "get as much detail as you can about the system before bidding" is especially true of old systems.

Protip: get an extensible mechanic's mirror and a good compact flashlight; sometimes when you need to examine a part number on the side of a device with a narrow gap, even sticking your smartphone down there isn't good enough.

rajy2r said:

Have a customer with a small facility with a PLC-2 based system for all discrete control. All analog inputs and outputs have their own standalone controller. There is no HMI, so all changes are to be made at the local panel.

They would like to upgrade their system, which would allow the ability to make changes on a HMI and remotely.

Since they need about 8 IO cards, the 1769-L30ER (Compactlogix) is an option. The other option is to just upgrade the Analog side and keep the PLC-2 as a remote rack. What module would be used to make it a remote rack, and what comm module would i require in the main chassis.

A Redlion HMI for Analog Controls and IO was another option perhaps, but not sure if it can communicate to a PLC-2 rack.

They don't have much $$$ to spend, so looking for options with a potential to upgrade the other components later.

Click to expand...

The PLC-2 IO is .. 40 years old? ..

It is good, reliable equipment. I understand the temptation to touch as little as possible. But the wiring insulation may be getting brittle .. from AGE ... - just pulling the wiring arms off to check an IO card could cause issues ...

Please mention that a modern PLC of whatever brand, wired into their marshalling terminals and labelled properly, connected to a modern HMI ... is the reliable thing to do. Available spares, software that runs on something newer than Win95, and reliable wiring will keep their system running.

It's easier for mechanical/process people to show equipment in bad shape, that can cause downtime ... than it is to show electronics that have never failed so far, that will take a long time to fix. Or worse yet, unscheduled downtime that snow-balls. Replacing one piece jossles wiring and causes a failure in another piece ... as you try to replace things one at a time instead of according to a plan put in place that took into account commissioning and wiring issues.

They may not have the money to do it, but management has to make the decision with all of the info that they can get.

Just my 2 cents.

Please save yourself & customer a lot of headaches and get them to replace everything. We did some PLC-2 to PLC-5 upgrades in the ‘90’s and Rockwell said in addition to S/N’s and version #’s there were “MERI” numbers to worry about regarding compatibility.

Trying to reuse this old stuff would be a firmware matching nightmare fraught with all kinds of weird faults and startup problems. Trust me, from experience.

kekrahulik said:

I've only done a couple PLC2 1771 conversions - and its been a long time since - but I seem to recall having to replace the chassis on one of them - which really surprised me at the time. So if you are keeping the chassis - do a little homework and don't just assume.

Click to expand...

I was going to mention this, and you beat me to it.
The series of the parts makes a difference.

Sounds like a someone needs to part with some $$$ and get serious about what their situation is.

not to slam you, since you have no experience with a plc 2, here's what you will be facing.

1. the plc 2 program allows you to use real output addresses as internal bits, so you will have to look at the electrical schematics (if they exist) or actual wiring arms.
2. chassis slot addressing, 1/2 slot, 1 slot, 2 slot, complementary i/o. this can be found behind the right card of the local i/o chassis. look at the dip switch configuration. WARNING ! be sure you have uploaded the current plc program to the pc first, if the battery is dead, you will loose the current program when you turn the power off. i seem to remember that a plc2 will allow you to remove an i/o card while the unit is powered on, don't hold me to it. you will need a manual for this. i still have my plc 2 manuals, so i may be able to help with that. REMEMBER, the program in the plc is the master, all other pc programs may not be the current version.
3. there will not be any comments or rung descriptions. this is stored in the pc part of the program if you have the original program. Also, the rung comments may not match the rung logic. this can result when you attach the rung comment to the rung number, not the output. so be careful in that regard.
4. the plc 2 uses get and put statements to determine certain logic (sorry, it's been 25 years).
5. the timer and counter accumulation values are 200 addresses different from each other. for example, timer 1 has its preset at address 204 and the accumulation value is at address 404. the same for the counters.

your best option may be to contact your local distributor and tell him what is going on and that you will be buying parts from him. see if he can help with uploading the plc 2 program and saving it to the pc, and then print out a copy for you. also ask him what he would charge to convert the plc 2 program to a plc 5 and fix any conversion errors id the process. he can then save the file for conversion to the logix conversion.

hope this helps,
james

James Mcquade said:

not to slam you, since you have no experience with a plc 2, here's what you will be facing.


4. the plc 2 uses get and put statements to determine certain logic (sorry, it's been 25 years).


hope this helps,
james

Click to expand...

The classic [GET], [PUT], on the first rung.

Communications, for sure, and sometimes with Data Highway (i.e. the original Data Highway]

And, yes, it has been a long time.

jdbrandt said:

The classic [GET], [PUT], on the first rung.

Communications, for sure, and sometimes with Data Highway (i.e. the original Data Highway]

And, yes, it has been a long time.

Click to expand...

Also, aren’t many word values in a PLC-2 BCD or is it octal? I know the I/O addressing is octal.

Sort of job that could go either way, absolute best case is you swap the whole lot for new. Worse case is they absolutely don't want / can't spend that sort of money and you have to work with what you've got.

If it's the latter, you have to weigh up YOUR risk v reward, do you really want to be tinkering with a PLC-2 system, which may or may not die a death mid-tinker.

We would quote to retro fit the whole lot for new, but certainly would not to shoe-horn a semi-solution on something so old and obsolete.

If it's a £100k a year customer compared to a £2k a year panic phone caller once a year, then your opinion is likely to change.

But on paper, it has *****-show written all over it.

Quote"': "But on paper, it has *****-show written all over it."
++++1 on that.
Use the 1492 wiring conversion system.
https://literature.rockwellautomation.com/idc/groups/literature/documents/sg/1492-sg121_-en-p.pdf. That can reduce your risk of wiring errors and allow for a quicker install.