OPC and Allen Bradley

so i normally deal with the machine level of controls a difficult customer is forcing me to level up. machine was built as a stand alone unit, no comments on the controls system design, heck when i ask the project engineers where the system spec information was i was told there isnt one. customer is now here and asking a bunch of questions asking for changes, problem is one unit is crated (these are large gas engine driven natural gas compressors) and should be in the air to India in a few days, the other one is being packed for air freight as well and the last one is going by boat in a few weeks. the customer is now telling me these three systems need to connect to a DCS which is all siemens and im AB. had they spoke up earlier i could have added a modbus module and they could get all the information they want.

so he is asking me about OPC compatibility, which from my research would an appropriate response be 'AB is OPC compatible via third party solutions' unless there is something i am missing?

In-Chassis OPC UA Server module ?

https://opcconnect.opcfoundation.or...pc-ua-server-in-the-controllogix-plc-chassis/

A licensed version of RSLinx also has the ability to be used for OPC communications.

lfe said:

In-Chassis OPC UA Server module ?

https://opcconnect.opcfoundation.or...pc-ua-server-in-the-controllogix-plc-chassis/

Click to expand...

it is a compactlogix system and since it was not in the scope to supply this type of communication, i am not spending any money on hardware or any development. just looking to point them in the proper direction.

blftech said:

A licensed version of RSLinx also has the ability to be used for OPC communications.

Click to expand...

i will look into that, thank you

Have them take a look at the Red Lion Data Station.
https://www.redlion.net/products/in...ollers-and-data-acquisition/data-station-plus

RSLinx as OPC server will be the obvious solution.
As far as I know RSLinx can do OPC DA, but not OPC UA (yet ?)

mobil1syn said:

it is a compactlogix system and since it was not in the scope to supply this type of communication, i am not spending any money on hardware or any development. just looking to point them in the proper direction.

Click to expand...

Ok.

I think it should be clear if the client will use the security features of OPC UA.
I doubt that the RSLinx server has them

There is an RSLinx OPC UA. Here's an example with Ignition.

https://www.godboutpcs.com/post/ignition-emulate-setup

Put in a Redlion data station or a an EXWare 705 ( https://www.exorint.com/en/product/exware705 and run this as a data aggregator to the DCS. I would avoid using RSLINX as this relies on a PC.. would be better with Kepware as it is more stable if you want a PC solution.

"The control system is OPC compatible via RSLinx Classic, FactoryTalk Gateway, and multiple third-party solutions. No OPC or other external interface was specified, described, or included in the scope of supply."

Kepware is generally my recommended OPC server if you're not going to use something native to Rockwell.

Most DCS systems have a more direct Rockwell interface, but again, that's up to the customer to configure and provide.

I recommend Kepware as well. In the last few years they made quite a few improvement including way to aggregate data and UA compatibility.

mobil1syn said:

so i normally deal with the machine level of controls a difficult customer is forcing me to level up. machine was built as a stand alone unit, no comments on the controls system design, heck when i ask the project engineers where the system spec information was i was told there isnt one. customer is now here and asking a bunch of questions asking for changes, problem is one unit is crated (these are large gas engine driven natural gas compressors) and should be in the air to India in a few days, the other one is being packed for air freight as well and the last one is going by boat in a few weeks. the customer is now telling me these three systems need to connect to a DCS which is all siemens and im AB. had they spoke up earlier i could have added a modbus module and they could get all the information they want.

so he is asking me about OPC compatibility, which from my research would an appropriate response be 'AB is OPC compatible via third party solutions' unless there is something i am missing?

Click to expand...

Short answer. Yes, AB is OPC compatible.

And NO, I don't recommend using it.

I have struggled with OPC since 2003. RSLinx is a decent server, but it gets confused sometimes and stops serving data. The tools inside OPC for monitoring the communication status are not reliable in telling you when it has stopped working. I now use a heartbeat, number of seconds since midnight, that is moved by the polling machine to another register that is written to the PLC.

I would recommend getting all of your OPC software from one supplier if you can. Otherwise, they argue about whose problem it is to fix any given issue that you find. That said, matrikon technically has support ... but they ask you to turn on logging for every problem, gather data for a week, and send them gigabytes of information. I don't recommend their software. Particularly the DataManager, which reads data from one source and writes it to another ... like reading from an ABB system and writing it to a ControlLogix for alarming.

I've spent a lot of money in the past few years getting anything that matters (in the control sense) off OPC and onto:
- a DeltaV VIM interface with the ControlLogix
- a DNP interface with our ABB hoist and power gear
- a Modbus/TCP interface to our power meters
- a serial modbus RTU interface with our standby generators

All of these solutions have been at least an order of magnitude (10X) more reliable than OPC. For the DeltaV VIM portion, it's more like 2 orders of magnitude more reliable (100X). I don't actually know what the issues are with OPC ... but between patches for the OS that the computer runs, patches for the various OPC software, security exceptions for the mis-behaved software that is part of OPC ... it just isn't reliable. *AND* no one seems to understand it all. There are not many tools in the toolbox for troubleshooting. Rebooting PCs, restarting services, and rolling back OS upgrades ... that's about it.

Our PI system will still be using RSLinx and an OPC connector to gather data. I think there is a connector running on our DeltaV Application station as well. Those are someone else's systems, and they deal with it when it stops working.

I should be OPC free, in our controls world, in about a month.

Important for me to clarify if you refer to OPC UA, or the outdated OPC DA.

If the customer wants to have the same OPC that Siemens has natively in S7-1500 then it will surely be OPC UA

Well, I honestly don't know how one get away from OPC these days or maybe we are talking about very different usage.

I would say OPC DA through DCOM is a completely mess and should NEVER be used in production environment. OPC DA between controllers are also to be avoided (maybe that's what you are saying). the problem is OPC DA runs on Windows and Windows only. UA is supposed to fix all that, in fact, Microsoft is supporting UA to run IOT devices and UA might also replace protocol like Ethernet/IP.

However, OPC as the com driver between controller and HMI or historian is about standard as it comes.

There are quite a few UA compliant OPC out there now. All Kepware OPC are supposed to be UA out of the box and Redlion's Edge controller also can convert something like hundred of protocol to UA.

lfe said:

Important for me to clarify if you refer to OPC UA, or the outdated OPC DA.

If the customer wants to have the same OPC that Siemens has natively in S7-1500 then it will surely be OPC UA

Click to expand...

My experience is with OPC DA. OPC UA was not around at all until ... 2008 is what the OPC foundation says. I don't remember actual products before 2010.

By that time I was not interested in converting anything *TO* OPC version anything.

Fool me once - shame on you. Fool me twice - shame on me.

When there is no other alternative to OPC, at any price ... I still won't install OPC since I'll likely be retired and won't care what my replacement does!

The OPC DA product family has cost me hundreds of thousands of dollars in production downtime, troubleshooting, upgrades, and general waste of time. It was supposed to be the answer to all problems with communications. It wasn't. Maybe OPC UA is now, but I don't care.

I would suggest anyone looking for a solution have the vendors SHOW YOU a working system. Not a product demo, a system with thousands of points working in a production environment. If they can't get any of their existing customers to show you a working system ... maybe they don't have one!