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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 tunneling
  • Connecting an OPC server to another OPC server to share data. This is known as OPC bridging

 

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.
Usage

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)
  • Standardization

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.

To know more about the IoT services and solutions

  • 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,
    • System
    • Panel
    • Door
    • Area
    • Output
    • Point
  • 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.

To know more about how we can help you with OPC implementation for your building automation needs, Learn more about our Industrial Automation Solutions or digital engineering services

 

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OPC Server from Tibbo Technology

OPC – «Open Platform Communications» – is a set of standards and specifications for manufacturing telecommunication. OPC specifies the transfer of real-time plant data between control devices from various producers. OPC was designed to process control hardware and support a common bridge for Windows-based software applications. OPC was aimed to reduce the number of duplicated effort performed by hardware manufacturers and their software partners.

 

The most typical OPC specification, OPC Data Access (OPC DA), is supported by Tibbo OPC Server. Any device compatible with the Tibbo AggreGate protocol can be a data source. AggreGate is a white-label IoT integration platform using up-to-date network technologies to control, configure, monitor and support electronic devices, along with distributed networks of such electronic devices. It also helps you collect device data in the cloud, where you can slice and dice it in alignment with your needs. In addition, the platform lets other enterprise applications transparently access this data via the AggreGate server.

Tibbo OPC server has embedded AggreGate network protocol. It can both interact with any Tibbo devices via AggreGate agent protocol and connect to AggreGate server. The AggreGate agent protocol open-source solution is published for Java, C#, and C++ programming languages, so your connection scheme is not restricted to AggreGate server  or Tibbo devices only.

 

Examples

A simple example: TPS reads Tibbit #29 (Ambient temperature meter) and forwards data to OPC server via AggreGate agent protocol.

A more complex example: we have a Windows-based PC controlling a wood processing machine by means of AggreGate server through the Modbus protocol. If Tibbo OPC server is linked with AggreGate server, the data from the machine is sent to Tibbo OPC server, and therefore, we can operate and monitor the machine via any OPC client.

Technical Specification

  • Compatibility with Windows XP/2003 or later (Microsoft Visual C++ 2013 redistributable is required - installed automatically)

  • Support of DA Asynchronous I/O 2.0 and Synchronous I/O with COM/DCOM technology

Tibbo OPC Server transmits the information on the Value, Quality and Timestamp of an item (tag) to the OPC Client applications. These fields are read from the AggreGate variables.

 

The process values are set to Bad [Configuration Error] quality if OPC Server loses communication with its data source (AggreGate Agent or AggreGate Server). The quality is set to Uncertain [Non-Specific] if the AggreGate variable value is empty.

In the following chart below you can see a concordance table of the AggreGate variables and the OPC data types:

AggreGate Data Type OPC Data Type
INTEGER VT_I4
STRING VT_BSTR
BOOLEAN VT_BOOL
LONG VT_I8
FLOAT VT_R4
DOUBLE VT_R8
DATE VT_DATE
DATATABLE OPC VT_BSTR (by default)
COLOR VT_I4
DATA VT_BSTR

To learn more about Tibbo OPC server, click here

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