OPC data collection

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Thread Starter

Break_thru

I already read tutorial in OPC, then I decided to know more about it.

I also have a question: how can we collect data, for example from our PLC, and receive to PC? Do they need Profibus or just simple 2 wire (RX and TX) or RS232 connection? Can u give me the detailed information? Thanks.
 
S
Hi dear,

First of all you should check both software and hardware protocols supported by your device. For example most of the devices follows Modbus protocol. you should have I/O server installed on your PC. This server needs register mapping of your device to be fetched. On this basis it can read the device.

Second thing, RS232 or Rs485 or whatever it may be. They are for serial communications only. But at the same time your I/O server should have the serial protocol configuration like device baud rates, parity, data bits, etc.

Thanks,

Sunny
 
Give us a detailed description of your PLC (make/model, protocols supported, etc.), and I'm sure many here would be glad to help.
 
M

Marc Sinclair

Hi, Why have you decided to use OPC? many PLCs can now send data via FTP or WEB Services. I send data from PLCs using TCP/IP to a central server as .csv files, these can be read by spreadsheets, Database programs or javascript to display data on webpages. All platform independent, and the graphs look lovely on macbook screens :)

Marc Sinclair
 
V
Every PLC needs some protocol to communicate with the PC. The Hardware aspects of the protocol will decide what kind of connection you will need from the PC to the PLC and the sofware aspects will define the driver you will need on the PC.You need to consult your PLC documentation to know these details.

OPC is a COM based technology which will allow you to write programs in VB, VBA, VB.Net, C# etc. to read/write data from your PLC and do much more using an OPC Server. The OPC Server can be divided into 2 parts. One part is a set of standard functions which are common to all OPC Servers and is written as per the OPC Specifications.

This makes it possible for your programs to read data from any OPC Server using the same code since these functions are the same for all OPC Servers. The other part is implemented as per the protocol for which the OPC Server is written. So it will vary from protocol to protocol. This part actually communicates with the PLC and makes data available to other applications using the standard functions set.

Most PLC vendors have their own OPC Servers developed. So you can consult your PLC vendor if they already have an OPC Server for the PLCs you have. It may be either free or licensed decided by the PLC vendor.

You can get more information about OPC at http://www.opcfoudation.org.
You can contact me if you need more help.

Vipul Shah
eGenietech Software Services
http://www.egenietech.com
[email protected]
 
N

Nathan Boeger

There's much more info at the OPC Foundation web site. The nice thing about an OPC client is that you don't need to worry about the communication layer as much. OPC Servers support many different communication protocols including serial (RS232), ethernet, and many other industrial protocols.

To get data into a PC, you use a program that acts as an OPC Client. FactorySQL, for example, transfers data between an OPC Server (PLC source) and SQL databases. HMI programs tend to "transfer data to a PC" by visualizing it on the screen. If you're writing your own program you can do whatever you want.

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Nathan Boeger
http://www.inductiveautomation.com
Total SCADA Freedom
 
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