Best way for comunication PC-PLC

Mar 31, 2005 11 Replies

Hi all:



We are trying to develop a mixed control system with a OMRON PLC and some PC´s. The PLC will send messages to the PC´s, when the PC receive the message it must execute some processes. It is very important to syncronize communication between them, only some milliseconds of delay are allowed. Has anybody suggestions how we can implement this configuration?.



Thanks in advance Vicent Vidal


Is this the communication only that must be synchronized or the processing of data by the PC?

for the latter, you might consider using real time extensions such as Venturcom RTX for windows or RTLinux depending on your OS.

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For the former you could use PC cards that implement the protocol you are using.

Check out if this version of PLC is supporting PROFIBUS or CAN at frame level.

If this is the case you could use QNX6.3 on a PC in order to communicate with the PLC using PROFIBUS or CAN.

Best Regards

Armin

http://www,steinhoff-automation.com

communicate

This a valid option if the PC can be turned into a dedicated device. Otherwise if you must use a Windows base PC, you could use National instruments LabView real time extensions which also requires less low level programming.

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extension

Need more info on your needs.

Is this a one way trigger message to an addressed PC?

Same message trigger multiple PC's?

more specific's

Vicent wrote:

No, no ... The RTOS QNX6 doesn't turn a PC into a dedicated devive!

QNX6.3 has very nice desktop features and it is very scalable. The run-time system (including the GUI Photon) costs in the range of $300-$400. There is also available a free XFree86 based windowing system and lots of free third party software.

Regards

Armin

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device.

I won't argue about QNX user frendliness. I used it in the past for some projects without problems. Could the OP describe its requirements in terms of OS? Windows could be required and QNX would not be an option despite its capabilities.

There will be multiple PC´s in the networkk, maybe three or four and all of them have to response at the same time to the signal.

Thank you Vicent Vidal

configuration?.

Could you describe your requirements more precisely: What are the acceptable delays between sending of messages by the PLC and processing at the PC ? Should the time be met with 100% or 99.99% certainty ? Why can't you execute the process at the PLC and push out the results to the PCs for delayed background processing ? What are the required OS for the PC if any ? Must the process on the PC communicate with third party software, which ones ? What are the consequences of the processes being not executed at the same time ? What is the acceptable jitter? Are there safety levels to be considered ? Are the PCs connected and synchronised among themselves,=20 by what mean ?

You might want to have a look at Profinet. It is an industrialised ethernet using TCPIP for pretty fast coms or RT for the kind of high speed coms toy are looking for.

Yes, I suposse that this is a good definition.

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