OPC is a software interface interoperability standard that allows secure and reliable exchange of data between Windows programs and industrial hardware devices. It is platform-independent and ensures the continuous flow of information across multiple vendor devices. eInfochips has successfully customized an OPC classic server for one of our clients in Building Integration Systems (BIS).
What is OPC?
The acronym "OPC" stands for "OLE (Object Linking and Embedding) for Process Control". OLE is based on the Windows COM (Component Object Model) standard.
OPC standard is implemented in server/client pairs. The OPC server is a program that translates the hardware communication protocol used by a PLC into the OPC protocol. The OPC client software is a program that connects to the hardware, such as an HMI. The OPC client communicates with the OPC server to receive data or send commands to the hardware.
How does OPC work?
OPC specification describes the interface between clients and servers, servers and servers, including access to real-time data, monitoring of alarms and events, access to historical data and other applications.
The classic OPC connection scenario is a single server-client connection on a single computer, but there are more options which include:
- Connecting an OPC client to several OPC servers. This is called OPC aggregation.
- Connecting an OPC client to an OPC server over a network. This can be done with OPC tunnelling.
- Connecting an OPC server to another OPC server to share data. This is known as OPC bridging.
The OPC DataHub is exclusively designed for all these tasks. A combination of OPC server and OPC client supports many connections. Thus, it can connect to several OPC servers at the same time for OPC aggregation and OPC bridging. Two OPC DataHubs can reflect data across a TCP network to provide OPC tunneling.
Technical Benefits of OPC
In addition to improving OPC server and client connections, the OPC DataHub can connect any OPC server or client to other applications as well, including Excel, a web browser, or any other database. And, it can be used to import OPC data into Linux or QNX.
Following OPC specifications are used in industries:
- OPC-DA (Data Access): Provides access to real-time data. We can query most recent
values of temperature, pressure, density, acceleration, and other types of process control data from OPC-DA server.
- OPC-HDA (Historical Data Access): This is used to retrieve historical process data for analysis. This data is typically stored in files, databases or remote telemetry systems.
- OPC-AE (Alarms & Events): OPC AE servers are used to accept and exchange
process alarms and events.
- OPC-DX (Data eXchange): It defines the way OPC server data is exchanged with other OPC servers.
- OPC-XML (XML Data Access): It defines schema and data representation formats based upon XML standard. This makes it possible to share & manipulate process control data across all operating systems – Windows, UNIX, Solaris, etc.
Benefits of using OPC standard are:
- Reduced load on the hardware device.
- Increased scalability of the system.
- Because of OPC server, client applications need not know anything about hardware protocol details.
- Though device need not serve multiple clients, So Increased life for the device.
- Interoperability (Unix/Linux and Windows - both platforms are supported by OPC)
eInfochips - OPC implementation
At eInfochips, we have provided embedded solutions for OPC’s industrial automation product line for our clients in embedded solutions.This includes detailed work on:
- BIS systems: Building Integration System , or BIS, is a software package that brings building automation, access control, video surveillance, intrusion, fire alarms and voice evacuation onto one convenient management suite. The classic OPC Server had implemented specific protocol over TCP/IP protocol to monitor and control different types of building integration system panels, which is able to interface with OPC client of the BIS system software.
- System alerts: In OPC Server, we had implemented OPC-DA (Data Access), OPC-HDA (Historical Data Access) and OPC-AE (Alarms & Events) specifications. For controlling and monitoring panels, OPC client fires different commands to the panels by using OPC server e.g. unlock door, lock door, arm area etc.
OPC server developed by eInfochips contains the following modules, functionalities and activities, listed below.
- Design, Development and Testing of OPC Classic server for different panels used in a building integration system with specific Automation protocol
- Implementation of following group commands on OPC Server,
- OPC server communication stacks integration (TCP)
- OPC server security - Command Authentication AES 256
- Client and status command implementation
We have also developed OPC Clients for our customers, running on Linux OS to communicate with OPC server over Ethernet. This further communicates with OPC server for Reading and Writing data/parameters. In OPC Client, we had implemented OPC-DA (Data Access), OPC-HDA (Historical Data Access) and OPC-AE (Alarms & Events) specifications. OPC Client will communicate with OPC Server for fetching data from the PLC. At the other end, it will send/receive historical and live data of temperature, pressure, density, acceleration etc. from the OPC server to the cloud for storage and analysis.
Darsha Naik is a Senior Engineer at eInfochips. Darsha has completed her M.C.A from Gujarat University, Ahmedabad. In her spare time, Darsha is interested in reading books and explore new places.
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