PC to PLC communication without using standard software from the makers

Hi all..
Well I'm very new to this field, and please excuse me if i post something stupid..
Can anyone please tell me how do we read and use data from a PLC without using the softwares given by the makers of the PLC.

Thanks,

Akshay.

Question not understanable.

Hi Akshay,
Your question not clear and understanable.
If you explore your question in details I will help you.
I am also from Pune. You may send me personal message I will give my cell number.
Bye,
Riyaz.

OPC

aceakshay said:

Hi all..
Well I'm very new to this field, and please excuse me if i post something stupid..
Can anyone please tell me how do we read and use data from a PLC without using the softwares given by the makers of the PLC.

Thanks,

Akshay.

Click to expand...

As long as we're talking about run-time stuff like setpoints and process variables, and not program uploading/downloading, OPC is your method of choice. Some OPC companies, such as MatrikonOPC and Kepware, offer OPC Servers as an alternative to vendor-supplied ones. Popular devices usually have the most alternatives.

We've got a pretty good tutorial for those new to OPC available at: http://www.matrikonopc.com/resources/opc-tutorials.aspx

I'll explain a bit further..

I'll explain a bit further...
Well the softwares given by the makers can read the data from the PLC, and also we can program the PLC as per the requirement using ladder diagrams etc.
What i need to ask is, is it possible to read the outputs of the PLC using Java and VB (Custom made software)?

Thanks for your posts..

Akshay.

It is possible, but probably not cost-effective. You will need to know the details of the communications protocol used by the PLC. Not all manufacturers publish the information.

Almost all PLC vendors provide (or sell) an OPC server that allows data access to their PLCs using third party equipment or applications. This is most likely the easiest way to satisfy your need. If you search google for 'opc visual basic' or 'opc java' there is a wealth of information on creating an OPC client in Visual Basic or Java.

An alternative way is to find out what protocols your PLC supports. If they support any open protocols you may be able to purchase or download the specifications for the protocol and develop a custom driver for accessing the data. Depending on how widely used the protocol is there may already be open source versions or free sample code floating around the net. There will almost certainly be a commercial version. One such vendor I have dealt with that sells solutions for several PLC makers is http://www.ingeardrivers.com

There are active-x objects that can be purchased from third parties that handle the communications between a PLC and PC. This allows easier development of an HMI in VB/C/C#..... if you want to.

I've worked on HMIs that used active x controls from http://www.automatedsolutions.com/products/activexcontrols.asp

It worked pretty well, but of course you'll pay money for the active-x control.

aceakshay said:

I'll explain a bit further...
Well the softwares given by the makers can read the data from the PLC, and also we can program the PLC as per the requirement using ladder diagrams etc.
What i need to ask is, is it possible to read the outputs of the PLC using Java and VB (Custom made software)?

Thanks for your posts..

Akshay.

Click to expand...

Possible, but depending on the PLC/protocol it could be very difficult to program. Something like Modbus wouldn't be too bad. If you are trying to hook into one of the more difficult to program protocols, you could use an OPC Server to handle the protocol part, and then you could use the "DA Automation" VB dll libraries to connect to the OPC Server.

Don't miss the open source options. Sometimes you can find drivers with source code at no cost. Search sites like these:

www.sourceforge.net
www.freshmeat.net
www.codeplex.com

Thanks a lot everyone...

Hey people..
Thanks a lot for your inputs.. its really helpful... i'm trying to do something with socket programming in Java.. this is only to communicate with the ports of the PC which will be connected to the PLC...
Lets see how it works...
More suggestions most welcome...
thanks again..
Cheers..

Akshay

If your PLC have a serial port, you can communicate directly. But you have to write the software yourself.