Symbols in Simatic OPC Server?

Pete.S.

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Mar 2016
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I have an OPC server running that has unspecified connections to several different S7-300 systems.

I'm trying to understand how Siemens is thinking when it comes to symbols. I can access any data block but have to use absolute addressing and can't use any symbols.

What do I need to do to get the symbols from the S7 projects accessible from any OPC client (SYM:)?

Thanks for any help,
Pete
 
Hi,

the easiest way is to configure the PC station including the OPC server inside the Step7 project where you have also setup the PLC. Then you add the connections to the PLCs you want to communicate with. Inside the OPC server setup you can specify which symbols from the PLC should be exported. After compiling the project, you can download the configuration to the PC station, or you can import the .xdb file. Then the clients can access data via the symbols.
If someone is changing the address of a symbol inside the PLC, then he has to compile the PC station and download it. No manual work is needed.

It's also possible to add your own symbol file in the OPC server, but I haven't used it for myself. If you have Simatic Net installed, there should be this program somewhere inside the Siemens menu.
 
Hi Thomas,

the easiest way is to configure the PC station including the OPC server inside the Step7 project where you have also setup the PLC.

This is where I get lost. The OPC server is a standard PC server running only this software and it's completely separate from the multiple PLC's that it communicates with. The OPC server only has the minimal step7 software need to configure it which is what you get when you install it from the simatic net cd.

Then there are say five different S7 projects (one for each PLC). These comes from different vendors. The OPC server is not a part of these projects and the OPC server is not configured in any of these projects.

Do you mean that if I had one PLC with one OPC server I could/should put the OPC server inside the PLC project and configure both the PLC and OPC server from there?

Or do you mean that I could add the OPC server (a PC station?) to each of the five projects and then in each project I could download to the OPC server and the symbols from that project would automatically be transferred to the OPC?


It's also possible to add your own symbol file in the OPC server, but I haven't used it for myself. If you have Simatic Net installed, there should be this program somewhere inside the Siemens menu.

I'm going to look into that asap. Thanks!
 
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This is where I get lost. The OPC server is a standard PC server running only this software and it's completely separate from the multiple PLC's that it communicates with. The OPC server only has the minimal step7 software need to configure it which is what you get when you install it from the simatic net cd.

Then there are say five different S7 projects (one for each PLC). These comes from different vendors. The OPC server is not a part of these projects and the OPC server is not configured in any of these projects.

Do you mean that if I had one PLC with one OPC server I could/should put the OPC server inside the PLC project and configure both the PLC and OPC server from there?

Or do you mean that I could add the OPC server (a PC station?) to each of the five projects and then in each project I could download to the OPC server and the symbols from that project would automatically be transferred to the OPC?

Here is a Siemens article which describes how to add a PC station to an existing PLC project:
https://support.industry.siemens.com/cs/ww/en/view/17413251

But the article misses the relevant point: adding the connection between the PLC and the PC station (specified connection).

I know your problem with different vendors you have to include in your OPC server. I have similar projects, where I use therefore only absolute addresses instead of symbols.

I have searched for a simple solution for this with symbols, but there are always some disadvantages.

One solution is, that you can setup a Step7 multiproject. I don't know if you are familiar with this. With a Step7 multiproject you can combine several single projects to one multiproject, and add communications between the single projects. For your example, when you are the maintainer of the multiproject, you collect all single projects of the other vendors, and combine them to a multiproject. You can add your own project including the PC-station with the OPC server. Then you can synchronize the subnets from the single projects, so you can setup your connections from your PC-station including the OPC server to the single project PLCs. The main disadvantage is, that the symbolic mode is only possible with a specified connection. Means, that you have to download the connection information to the PLCs you want to communicate with. On a S7-400 you can do this in Run-Mode, most S7-300 needs a reboot.
If your OPC server is working as expected, you can "outsource" the single projects from your multiproject, and give them back to your vendors to work with. If they make a change in an address, they give you the project back, you integrate it back into the multiproject, generate system data and load your OPC server with the new informations.

It sounds a little bit complicated, but once you have setup the multiproject and know how to handle this, it's not a big deal. It's mainly used in PCS7 projects, where you may have to combine many PLCs and PC-stations.

That's the way you have to handle this, if you want to stay in the "Siemens universe".

But there are other vendors of OPC servers, which could readout the symbols from a Step7-Project.

Writing the symbol file for the Simatic Net OPC server was no solutions for me, because it makes no difference if I have to maintain the addresses inside the OPC server symbolic file, or inside the OPC client project.
 
What also is possible, but has a little bit of a hack:

You setup a Step7 project and add your PC station including the OPC server. Then you copy the PLCs you want to communicate with from the vendor projects into your Step7 project.

You don't need the full hardware configuration, it's also possible to add dummy-station which has only the correct IP address or DP-address if you are using Profibus DP (and rack/slot if you connect to S7-400).

Also I would delete all programm blocks, and only keep the symbol table, datablocks and UDTs.

Then you setup the all connections in NetPro, and generate the symbols you need. You need a specified connection to get the symbols from the PLC program you connect to.
Then you are done with your PC station setup. But the connections won't work, because the PLCs reject any connection request from your OPC server.

You have to note the connection parameters from your NetPro setup, and say all vendors, they should setup an unspecified passive connection to your OPC server, using the parameters (TSAPs) you have given them. If they have downloaded this to their PLC, the connection will work.
 
It is not a big deal, when you know what you have to do.

I never knew what you can do with multiprojects, since I have used in a PCS7 environment.

It is not big deal, I mean the method how you do it. You need to make project without PLCs, import some data from other projects and download, then you still need inform others to do exactly with these setting or everything stop working. And nothing is explaimed anywhere. And after modifications you need to do all again.

That is awkward way to do, when on other platforms you can to it, well more simple
 
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It is not big deal, I mean the method how you do it. You need to make project without PLCs, import some data from other projects and download, then you still need inform others to do exactly with these setting or everything stop working. And nothing is explaimed anywhere. And after modifications you need to do all again.

I think you have absolutely no clue what a Step7 multiproject is, and what you can do with this. How would you handle a big project which shares common ressources, without combining some informations? And how would you handle many different programmers working on this project, without combining and seperating them?

It's all explained how to use this, example:
https://support.industry.siemens.com/cs/ww/en/view/22258951

To establish a network connection, the partners need to know the communication parameters. On TCP/IP this is at least the IP-address and the port number if you use TCP sockets. Siemens uses additional TSAPs as communication parameters, as you can access different automation devices under the same IP.

I am curiuos what system you are using, which magically exchanges all this informations, whithout someone is doing anything.
 
I know what Siemens multiproject is. Siemens OPC is problem, you self saying that you use absolute addressing instead of symbols if there is several different step7 projects. (not multi)
 
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Thanks for you help guys. I'll research the different methods to see what fits the best.

The client have several OPC servers, each with a number of PLC's to each. All in all I think there are about 50 siemens PLCs, maybe more, but they are not all hooked up yet. OPC server goes to SCADA/DCS systems.
 

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