Classic OPC is based on COM, which is a technology in Microsoft Windows. Therefore, the information in this section only applies to Ignition Gateways installed on Windows. For other operating systems, OPC-UA must be used.
The OPC-COM module provides the ability to connect to OPC servers that only communicate using the older COM based OPC-DA standard. If you have an OPC server that is not capable of accepting OPC-UA connections and you need to talk to a PLC for which Ignition has no supported driver, you'll have to use the OPC-COM module to make your device data available in Ignition. Connections to OPC servers will be held open while the Ignition Gateway is running. All subscriptions to the server will use the same connection.
This section provides a brief walk-through of how to set-up a new Local or Remote OPC-DA server connection using the COM module. Due to the complications that Windows DCOM security settings can cause, this set-up guide is followed by the Troubleshooting OPC-COM Connections section that deals with an overview of how to deal with a faulted server connection due to DCOM security settings as well as other possibilities.
With the OPC Core Components now installed the next step is creating/configuring a new OPC-DA server connection.
In the case where your connection status is reporting Faulted, the troubleshooting process begins. As previously stated, configuring the DCOM settings on your machine can be a headache. The Troubleshooting OPC-COM Connections section next is an attempt to ease the process of determining why your connection is faulted and how to go about fixing the issue. If after exhausting the options presented to you, you are still having issues getting you server connection up, give our Inductive Automation tech support line a call and one of our representatives will be happy to assist you.
This section provides you with a list of common OPC-COM connection problems with their possible solutions. It would be impossible to give an exhaustive list of everything that can go wrong but this should give you a good start on the troubleshooting process. If you do not see your problem listed and your connection status is faulted, try following the steps outlined in the Ignition Server DCOM Settings and OPC Server DCOM Settings sections.
There are some cases in which an OPC Server that is installed will not show up in the generated list. This list is generated by the OPC Server Enumerator which is part of the OPC Core Components, so when a server you have installed on the machine does not appear in this list it is likely due to the OPC Core Components not being installed correctly.
Try reinstalling the Core Components and going through the process of creating a new server connection in Ignition again. If the server still does not appear and you have the ProgId (or the CLSID for a remote connection) for the OPC server, you can just select the Other Server option and then click Next. In this situation you will have to enter the ProgId manually on the New OPC-DA Server page.
With all the correct information about the OPC server we can sometimes still make a valid connection to the OPC Server even when it is not detected automatically. This however is rare. Most of the time when the server is not detected, any connection attempts Ignition makes will fail.
Usually this occurs when the DCOM settings for the machine on which Ignition is running are not correctly configured. DCOM connections go in both directions. Ignition must be able to send requests to the OPC server and the OPC server must also be able to callback to Ignition. If the DCOM settings on the Ignition server are not configured correctly those callbacks will fail and the server connection that initially had a status of “Connected” will either fault or all the tags that you have configured will come back with bad quality.
This is a problem that can affect both local and remote server connections.
Follow the steps outlined in the “Ignition Server DCOM Settings” section to ensure that you have correctly configured the DCOM security settings on the Ignition server machine.
It is important to note that Ignition runs as a service under the Windows System account. This can cause some issues with OPC servers that are meant to run interactively, meaning they run under the user account that is currently logged on. When Ignition attempts to make a connection to the OPC server, it will attempt to find an instance running under the same account and if it doesn't find one it will launch its own instance under the System account. Even if there are other instances running, Ignition will choose the one that was launched under the System account for its connection.
Many OPC servers maintain an instance running under the interactive user account that has been configured by the user and maintains all of the device connection information. When Ignition launches a new instance, this configuration information is lacking and none of the desired data can be seen or accessed. To get around this problem, you must specify in the DCOM settings for the OPC server that it always identify itself with the interactive user. Essentially this will force Ignition to use the currently running instance of the OPC server.
This is almost always caused by the OPC Core Components not being installed correctly. Download and install the correct version(s) for your system(s) from the OPC Foundation (www.opcfoundation.org). Remember, if you are making a remote connection you must install these components on both the Ignition server as well as the machine on which the OPC server is running.
Follow these steps to open up the DCOM security settings on the machine that is running Ignition:
Follow these steps to open up the DCOM security settings on the machine that is running the OPC server:
The process of connecting to an OPC-HDA server is similar to that of a DA server. Instead of going to the "OPC Connections" section, however, you define the server as a Tag History Provider.
Provides a connection to an OPC-HDA server.
|Provider Name||Name of the Tag History Provider.|
|Enabled||If the check box is selected (enabled), the provider is turned on and will expose historical data|
|Description||A description of the provider.|
|ProgId||A description of the provider.|
|Use Flat Browsing||Flat browsing returns all items at once. This is less efficient than normal browsing, but if a server only supports flat browsing, then this needs to be checked.|
|Remote Server||If selected, DCOM will be used to connect to the server on the specified Host with the given ProgId or CLSID.|
|Host Machine||The name or IP address of the machine hosting the server. Leave empty for local machine.|
|CLSID||The CLSID of the server. If not specified, will be obtained using the ProgId.|
A similar procedure can be used anywhere Tag History can be bound or used.