Confusion about what exactly OPC server/client is

MattMatt9

Member
M
Join Date
Jun 2020
Location
Canada
Posts
119
So we are trying to read 3 meters on our line from a webpage. The 3 meters are on the network going to a PLC which is properly configured to read the values. I was advised to just create an opc server/client to read the values coming from the PLC so we can see all the values from the meters. I know OPC is a way a PC can communicate with devices such as PLCs. I am just kinda confused with server vs client and setting up?
 
It depends, sometimes...

The PC will be the OPC server.

Another PC/the PLC will be an OPC client.

Unless...

The PLC is Siemens S7-1500 as an example or Beckhoff, then the OPC server is "inside" the PLC

or...

You use Ignition SCADA, where the PC is the OPC server and OPC client and a driver connects to the PLC.

What PLC and OPC (DA, UA?) server do you plan on using?
 
Last edited:
I think we are using Ignition. So OPC UA.

So my confusion is, you say the client and driver "connect" to the PLC. What does this mean or look like?

And when you said PC/the PLC will be an OPC client, what does this look like? Like is there literally another PC that is connected to the PLC? And another PC as the server?

I feel like everything I read says something kind of different. Like I have read that the OPC server and client are on the same PC, but also heard what you just said that they are on different PCs.
 
With Ignition and Allen Bradley CPX/CLX as an example

The OPC UA server resides within the Ignition Gateway and the Logix driver also resides within the gateway. You create 3 device instances using the driver, drag and drop (browse OPC server in the Designer) your tags, create your screens linked to said tags, done by lunchtime and onto the next project.
 
I feel like everything I read says something kind of different.
Click to expand...

Because there is no one global way of doing it.

List your OPC UA and PLC in the OP and it would have been a less generic answer.

You can have Ignition gateway on one PC (server), KepServer OPC UA on another, etc, but with Ignition you don't need to because they make it so easy.

If your 3 PLCs are L8X ControlLogix with 50K tags in each, then yeah, you might want to divide and conquer with hub and spoke architecture. Again, it depends.
 
It is ignition OPC UA with a compactlogix PLC.

Here is the exact setup:
2 Meters daisy chained to an anybus device. Then the other side goes to the compactlogix PLC (I know of course there will have to be configuration done inside the PLC for the anybus and meters) but put that aside. So your saying all that has to be done in regards to OPC is to have a PC on the network with the Ignition software license and thats it?
 
Ya that makes sense. When it comes to actual interface designing is that all done within the software? I will obviously find out when it is set up but want to know beforehand how the designing works. And also what viewing of the PLC tags visually looks like within the software. Is it simple once I get it set up, am I just overthinking?
 
Speaking in general, server is an app/device that serves data to clients.

Think of some familiar server like SQL server or Web server.

in the context of OPC. OPC server servers data to OPC-Clients. OPC Client does not talk to PLC or other industrial devices directly, OPC-client gets industrial data by requesting it from the OPC Server.

PLCs <--> OPC-server <--> OPC Clients

A typical OPC client would be HMI or historian.
 
Currently there are several PLCs with OPC UA integrated server, and the future is going in that direction, since OPC UA is a superior protocol in several aspects.

Some PLCs that integrate it are:
  • Siemens S7 / 1500
  • Some Omron model
  • Those based on Codesys.

Furthermore, OPC UA is platform independent and truly independent of any automation Brand.

And not to confuse the outdated classic OPC (OPC DA) that could only run on Windows and OPC UA
 

Similar Topics

R
PZE X4P Safety Relay Y1 & Y2 Confusion
Hello, all, I am new here and pretty new to PLC'S. Closest thing I have to PLC experience is with avionics. At my new job I am a welding engineer...
Replies
4
Views
778
dwoodlock
dwoodlock
B
Point IO revision confusion
I am working on some documentation in preparation for updating firmware around our plant. On one particular PLC, the point IO has two different...
Replies
5
Views
679
bpcomp
B
W
FOR Instruuction Confusion
When enabling a FOR instruction does the index set to the initial value before the first execution of the Called Routine? e.g. Initial Value = 6...
Replies
4
Views
1,458
Contr_Conn
Contr_Conn
I
Some confusion with Factorytalk View Tags
Hello, My apologies in advance if this is a stupid question. I have done a fair amount of work in Factorytalk View machine edition, and I am...
Replies
2
Views
1,217
mylespetro
mylespetro
C
Mitsubishi software licensing confusion
I'm looking to purchase either GX works2 or works3 for a Q series rack I purchased off of ebay. Now the confusion comes from either purchasing...
Replies
2
Views
1,347
cherryfox
C
Back
Top Bottom