How can I write to a Siemens S7-300 PLC tag from OPC Server.vbai page by using a Knob object ?

[KemalKemal]

I am using NI OPC Server and I can read Siemens S7-300 PLC tags such as thermocouple values from the PLC. Additonally I can write manually a constant value to that tag by selecting it in the NI Distributed System Manager. And I can read the written value from NI Distributed System Manager or from NI OPC Server. But I can not write any value to the S7300 PLC tags such as by using a knob object at the NI Vision Builder AI Inpection (.vbai) page.

Any help is welcomed. Thanks in advance.

[ChristopheC]

The tutorial at the following location explains how to use Vision Builder AI as a OPC server.

https://decibel.ni.com/content/docs/DOC-18647

http://www.ni.com/white-paper/13574/en

To allow VBAI to connect to an OPC Server (i.e. act as an OPC client), you need to purchase and install the DSC Run-time System.

Once installed, you can create an OPC I/O client using the Distributed System Manager, create variables bound to OPC tags, then create VBAI network variables that are bound to these variables.

Another possible technical solution to connect to OPC Servers supporting Data Access 2.0 is to use the datasocket API in a Run LabVIEW step.

http://forums.ni.com/t5/Machine-Vision/Read-and-Write-with-OPC-through-NI-Vision/m-p/2048278/highlig...

Hope this helps.

-Christophe

[Paolo_Squillari]

Hi KemalKemal,

I have to comunicate with a Siemens S7 300, and I'd like to use the NI OPC Server. Can you explain me how to connect the PLC to a standard desktop PC?
Are you using a RS232-MPI adapter? My S7 300 has no ethernet connection, so I've to use the MPI port.

Thank you,

Paolo.

[alcava.cr]

Hi, try checking the manufactures page. I'm sure they can provide the reference.