Elipse Knowledgebase

• Uniformity of interface with different networks and protocols: with the use of OPC servers for different networks, access to process data is managed with no need adjust the drivers of each network, avoiding setup time.
• Full integration to the network: most of the time, OPC servers are created by the manufacturers, who will likely include all network features in this software, i.e., even when protocol changes are implemented, OPC will be updated by the manufacturer.
• Communication drivers are not needed: depending on the complexity, the creation of communication drivers may take months. Plus the costs involved are often prohibitive. Some devices or protocols may not have native Elipse drivers, but support communication through OPC Servers.
• Integration between different supervision tools: OPC makes a simple way of integrating different supervision tools available. For example, Elipse Scada can enter a network like OPC Client while the E3 works as the server, or vice-versa.

However, there are some disadvantages that should be noted for systems implementation with the OPC:

• Communication speed: OPC software may perform slower than those using communication drivers because of the involvement of a larger number of systems.
• Higher processing demands: As well as using different software, OPC Servers use Operating System services, which may require a larger investment in network machines or equipment when the OPC Server works remotely.
• Maintenance: maintenance of systems communicating within the OPC introduces a greater number of variables into the process. Failures of the communication services in Windows, for example, can be, and often are, the cause of stoppage in systems that run OPC.

2) Setup Procedure

The first step for communication in OPC is to have a locally or remotely available OPC Server installed and accessible. In the procedure described here, a standard application that can be created in the E3 Studio was used, and the Siemens Simatic Net installed in the same machine as the local E3 Server was used as the OPC server.

To communicate with this software, Simatic Net software was installed and configured, and adjustments made for communication with an Industrial Ethernet network.

The first step for OPC to access a piece of equipment is to insert a new "Driver de Comunicação OPC" (OPC Communication Driver) through the Organizer. Figure 1 illustrates this procedure.


Figure 1 – Inserting OPC communication driver


Next, go to the inserted DriverOPC (OPCDriver), right click and select the propriedades (properties) option. A window with many tabs will be opened. Go to the "OPC Driver" tab and click "Selecionar" (Select) (Figure 2).


Figure 2 – OPC driver properties


All available OPC servers will be shown as local or remote. Notice that the E3 appears in the list of available servers but will not be used for this exercise.

Select the existing option installed on your PC or on the network.


Figure 3 - List of available OPC servers


To ensure the configuration was done correctly, click "Ativar Comunicação" (Activate Communication) and then "Informações" (Information). This will open a window containing server data (version, status, etc.) and the local server time, illustrating the correct communication functioning.


3) Tags Importation

There are two different ways to use values that are available in OPC servers. The first one is to execute the process manually, inserting groups, OPC tags and OPC Block tags one by one and configuring their characteristics as described by the manufacturer.

The second is tags importation – a quick and efficient process of selecting which data will be monitored and controlled by supervisory control. To initiate the data importation process the server must be active and the OPC driver be correctly setup for your project. If everything is correct, activate the communication between OPC driver and OPC Server. This can be done in the OPC driver properties or by right clicking the driver and selecting the "Ativar Comunicação" (Activate Communication) option.

After the communication is activated, select the "Importar Tags" (Import Tags) option, as shown in Figure 4.


Figure 4 – Import Tags Option


A good justification for using tags importation is that it is possible to immediately check the exact moment of the importation, provided the process tags are correctly setup and available in the OPC Server. If data setup was done manually, there could be questions about where the problem is in the event of process failure.

In the importation tags window some filter options will be shown, but the most important are the two trees of data that appear as "Projeto Corrente" (Current Project) and as "Servidor OPC" (OPC Server). In this second option, all tags available for the filter in use are listed.

When locating a tag to be used in the E3, click and drag it to the grupoOPC (OPCgroup) where it will be used. Otherwise the tag will not be imported and communication to that tag will not occur.


Figure 5 - Tags available at the time of importation


The organization of tags in groups can be very helpful for good communication performance. There are some other points to be noted when dealing with communication, such as memory map organization, grouping of similar types, etc. Another important item is the search in which OPC Groups are read. This influences the application performance directly: the more priority a tag, the less time to search for it.

After importing the tags of interest, press "OK". You will notice that all imported tags will be listed in their groups just below the OPC driver.

To follow up tags values without launching the project, double click the OPC Driver. The list of driver tags will open on the right side of the E3 Studio working area. Activating OPC communication will list the tags values, which will be read according to the searching options setup of each OPC group.


Figure 6 - Tag in communication with the OPC


The reading result will be in blue when the reading succeeds (Quality = 192), and in red when an error occurs. For example, Figure 6 shows a communication error with the selected tag because the OPC that contained that network address was not available.


4) Conclusions

The use of the OPC as a communication interface brings advantages and disadvantages that should be noted when the project is defined. A good plan of elements such as tags quantity and memory mapping, just like in any project, will bring great benefits to OPC-based systems. This will ensure faster development with fewer risks than development involving drivers to protocols. In addition, as E3 is an OPC Client in every version, the investment in communication drivers can also be used for other purposes.