Integrator Uses OPC to Increase Flexibility

Feb. 1, 2005
A building automation supplier turned to OPC to solve the integration challenges involved with exchanging data among disparate systems.

A major supplier and integrator of building automation software is often faced with customer requirements they are not able to meet, given the capabilities built into the facilities’ automation systems. Customers are frequently demanding to know “Why can’t we do this when I have a 3 GHz, 1 GB of RAM PC on my desk at home, that has these capabilities?” To increase flexibility and solve a wide range of customer requirements, including adding functionality, integrating with other systems, and more, the building automation supplier has turned to a wide range of open manufacturing control technologies. OPC is one of the open technologies most commonly used by this supplier to solve integration challenges.

The supplier was installing a system for a large medical laboratory. The system managed lighting control, HVAC control, security systems and others. The project required that there be a touchscreen interface on each floor in the facility. From the touchscreens, users needed to be able to access data for their floor and for the other floors. Budget constraints meant the system had to be built as economically as possible.

Because the building was already wired for Ethernet, it was easy to obtain an extra network jack at each panel. The building automation system provided an OPC server interface as a means of moving data into and out of the system.

To move data between the remote panels and the Building Automation System, the integrator chose to use the open Modbus TCP Ethernet protocol as a fast and efficient means to communicate over the existing Ethernet connections.

On each floor, a Siemens Windows CE Multipanel operator interface was installed that runs an application using Siemens ProTool HMI software and an INGEAR Modbus Ethernet OPC server from Software Toolbox. Back at the Building Automation System, the user installed a copy of the TOP Server Modbus Ethernet Slave driver and the Software Toolbox Linkmaster OPC-to-OPC bridge. Linkmaster maps all necessary data from the Building Automation System to the Modbus Ethernet Slave. Each remote panel reads/writes data to and from the Modbus slave using the INGEAR Modbus Ethernet OPC server.

Easy data exchange

So how does all of this connectivity manage to easily and efficiently provide the necessary data exchange? Let’s look at some examples. Remember that all these steps are happening quickly over switched Ethernet, with software that was designed for the task of rapidly exchanging data among systems. Also, all configuration was done through point-and-click user interfaces. No custom code or programming was required.

The first example is writing data from the touchscreen to the Building Automation System. When the user wants to write a value to the Building Automation System, the HMI software writes the data to the INGEAR Modbus Ethernet OPC server, which in turn writes the data to the TOP Server Modbus Ethernet Slave. The Modbus Ethernet Slave automatically notifies Linkmaster of the new value, and Linkmaster in turn writes the data into the Building Automation System’s OPC server.

The second example is reading data from the Building Automation System, displaying it on the touchscreen and sounding alarms. When values change in the Building Automation System, its OPC server automatically notifies Linkmaster of the new value. Linkmaster notifies the TOP Server Modbus Ethernet Slave of the new value. The INGEAR Modbus OPC server on the Touchscreen is periodically polling the slave for new data. As soon as the new data is received, the INGEAR OPC Server notifies the HMI application which updates the user’s screen.

Through the use of open OPC protocols, the building automation systems integrator is able to provide solutions they were not able to provide before OPC without expensive and difficult to maintain custom code.