APPLICOM OPC (Brad communication)

mad4x4

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Join Date
Mar 2009
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Trying to use the APPICOM OPC server that comes with Bradcommunications APPLICOM Card for wornderware.

When I "browse" the OPC tags I get Group and then group has tags such as

Code:
EBPLC\
         |-A*.*
         |-A*.*_*
         |-AB*
         |-AW*
         |-DB*
         |-DB*.DDB*
         ..
          \-EB*.*

HPUPLC\
         |-A*.*
         |-B*.*
         |-DB*.*
         ..
         \P*.*_P


I was expecting to see a list of the OPC Tags from the Scada similar to the Export list you can find when you use FSGateway. If I select all the branches, I seem to load up the Network to the PLC as it seems to be reading everything from the PLC and not buffering from the server. .... Any Clues?
 
When I "browse" the OPC tags I get Group and then group has tags such as... Any Clues?

This is called a "hint" string.

I have seen it a few times. For example, the number of item IDs for "A" is 20,000, the server would return a "hint" (-A*.*_*) instead of 20,000 item IDs.

I would check the device documents for "hint" item format.
 
OK - Finally, see - this OPC Server is opening PLC Tags rather than accessing the SCADA tags. So I would Read the specific tag

Code:
MKP.DB910.DBD120F

This would give me the float in that register in the PLC ( unscaled in theory)

but I cannot read tag below which would be the tag assigned in the SCADA via the Tag Dictionary and, therefore, would be "Scaled"

MKP.Layer1_Pressure

This now poses the problem that some of the tags I need to be published are "SCADA" tags (Calcs & SPs in Scada) and some are PLC Tags (Real IO) so this connection point will not work. How do I get OPC DA linked to the Tag Dictionary of Wonderware 2012?
 
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Disclaimer, I dont know Wonderware or the Applicom card or associated OPC server.

Maybe it is the creation of the OPC Tags that is the issue.

This is how it normally works:
The OPC server provides the connection (so far this seems to work)
'something' creates the OPC tags.
The OPC client attempts to read or write the OPC tags.
The OPC server then performs the reads or writes.

Usually it is the OPC client that creates the OPC tags. But there can be other ways. For example by some software tool that imports the PLC variables and uses these to create corresponding OPC tags.

I think you are creating tags in wonderware and expect that the OPC tags gets created automatically. It is not impossible that there are more steps necessary. I.e. some additional method in Wonderware has to be called, or the OPC tags have to be created by an external tool, or the tags have to be exported from Wonderware into an external tool.
 
Normally the OPC server is where the tags are populated, this can be done in two ways, browse the source or entered manually, the OPC client can import the tags from the server, i.e. normally in the Scada tag database, you select OPC, connect to the server, import the tags.
I'm only used to Kepware & since my last job using it some 4 or 5 years ago things may have moved on but normally the Scada is the client.
 
The OPC server provides the connection (so far this seems to work)'something' creates the OPC tags.

The OPC server creates all item IDs. The clients connect to the item IDs provided by the server.

It is possible a client could request connection to an item ID and the server create the item ID. I would be interested in any server that offers that option.
 
We have an in-house developed OPC client application.
The OPC client creates the OPC items by an internal list.
Technically it is the OPC server that creates the items, but it is a service the server provides to the client. So the client is the one that requests the server to create the items.

When you open an OPC test client, it is the same thing.
Even if an OPC connection is available, initially there are no OPC items, you have to proactively do something to setup the items, either by browsing or by specifying the items manually.

Mark- said:
It is possible a client could request connection to an item ID and the server create the item ID. I would be interested in any server that offers that option.
That is more or less how it works, as far as I can gleen from looking over the shoulder of the programmer of the OPC client application. But it is a 2-step process. Create the OPC item, then read/write the OPC items.

My experience is with Siemens and Rockwell.
 
Yes I believe the client can have the actual tags, I have never used it that way but Kepserver suggests you do not need to create the tags in the server, the client can initiate them, I once saw a system where the only things on the OPC server is what looked like a set of directories (if you could call them that, never really lookedinto it further but in the OPC server the only things in the tags were:
CH1
CH2
CH3
and some others I cannot remember.
I think this is to do with aliases.

Here is something else from Kepware:
The OPCClosedOpen Connectivity via Open Standards (OPC) is a set of standard interfaces based upon Microsoft's OLE/COM technology. The application of the OPC standard interface makes possible interoperability between automation/control applications, field systems/devices etc. server's ability to automatically generate tags for select communication drivers brings OPC technology one step closer to Plug and Play operation. Tag information can be read directly from a device, and tags can also be generated from stored tag data. In either case, users no longer need to manually enter OPC tags into the server.
 
We have an in-house developed OPC client application. ...That is more or less how it works.

A custom application and server can do as the designer wants.

That is more or less how it works...

That is not how the OPC specification defines the interaction.

Most OPC servers require the configuration of the "communications" channel/path to the external devices and the definition of all item IDs (name,type, access type (read/write/etc.), data type, source address, optional scan frequency, etc..

Siemens and Rockwell may automatically, create all possible item IDs in the server. For Siemens and Rockwell that is possible because each created the OPC server (custom server). For an OPC vendor, if the PLC does not offer a method to query the PLC for tag names/data type, a human must provide all the required configuration data. And the query is outside the OPC protocol/specification.

The above is for OPC DA.
 
Mark, that is not true. As I stated above, for example in IFIX, you can configure the tags & their address & data type, the OPC server can access them once the link has been set up. I personally have never done it that way but have seen it on a Mitsubishi system that used IFIX as the OPC server, the addresses etc. were in the IFIX for example MC1.D500 (plus the data type etc.) on the OPC server the only things in the tags were "MC1" (obviously this is only amy recollection of the structure but it did confuse me to start with as I was expecting the actual tags to be in the server.
One system I did, I configured the tags in the server (easy to import them via a csv file), then on the Scada, browsed the OPC server, imported the tags, however, it does seem that on certain drivers the tags can be configured only in the client.

I think it is something to do with this I found in rthe help file for Kepserver

iFIX Native Interfaces
Overview

The iFIX native interface simplifies the connection task by allowing a direct connection to the local iFIX application without the use of the iFIX OPCClosedOpen Connectivity via Open Standards (OPC) is a set of standard interfaces based upon Microsoft's OLE/COM technology. The application of the OPC standard interface makes possible interoperability between automation/control applications, field systems/devices etc. Power Tool. When supported, this interface also has the ability to refine the connection between the server and the iFIX Process DatabaseClosedA database is an organized collection of information in digital or electronic format, typically structured. (PDB).
 
Mark, that is not true.

Nothing you wrote disagrees with what I wrote.

I said "most". Some protocols like MODBUS, the user can configure the server communication channel and the requested item ID from the client "can" contain enough information (and use defaults for all other OPC settings). Example: <ch>.400001, <ch>.100001, obvious an analog and digital (data type) and the example item IDs provides the path to the data in the external device. In this example, the server "knows" all possible client IDs.

Example: <some name>.<some more text>.<final text> item ID from a client to a server has no configuration data, data type, path, etc., and unless the server has an exact match (can parse the text successfully) to the client ID text, the request to set up a link will fail.

And again, this is for OPC DA. I have never created a UA server and do not know the protocol options. OPC DA, I created my first server in 2001 and created several in the following years.
 
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Sorry Mark I mis-read your post, I took it as being the data "had" to be configured in the OPC server, as I said, on most systems now the OPC server does not need the tags to be configured on ly the channels.
I still prefer to do it in the OPC server, as the ones I have seen where this is done in the client i.e. Scada was because the systems were upgraded that used direct drivers, therefore there was no need to configure the tags in the OPC.
 

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