How to transfer data PLC to PC through RS232 or 485

M

Thread Starter

m@z

Hi,

Would you pls give me some insight on how to trasnfer data from PLC to PC.

Suppose I have any PLC, at its basic let us programme with ladder logic. How do I have communicate my CP with this PLC to pick up WX or WY as well as DI or DO without using any PLC programming language.

In short, I have my PLC on the plant floor. Apart from basic HMI, for trouble shooting reasons, I want to get out certain data from the PLC and store in a PC for convenience of processing and the amount of data desired to be collected which is out of the scope of the PLC.

Hope I tried to explain the topic clearly.
Wish to fix the problem at the weekend...
rgds, m@z 050224
 
What a nifty weekend project...

Some of us use commercial software packages known as SCADA or HMI software which run under the PC's operating system, typically Windows, but there are Linux flavors, too.

The software communicates with the PLC via either a serial port or an ethernet port through either a model specific driver or in some cases, through an OPC server, which has to be compatible with the PLC. So the comm protocol may be open, like Modbus, or proprietary. Proprietary protocols require proprietary software.

SCADA packages are offered by all the PLC manufacturers, or there are independent companies that specialize in such.

There is some degree of effort in configuring the software so that you get what you want out of the PLC.

It may be time to call a vendor or two.

Bud
 
Find out what protocol you can use (Modbus, Profibus,etc) and what hardware is required (RS232, RS485, etc) then you have 2 choices:
1 - write from the scratch (let's say in VB) a driver to talk that protocol
2 - buy a ready-to-use driver or OPC...

If you have an HMI... maybe this can work as an OPC server... with some lines in VB or VBA you can access data from PLC.

Good luck.
 
T
There are several data Aquisition Programs on the market that will read and send data to the majority of manufactured PLCs. Wonderware, Intellution, National Instruments have leading version of DA programs that can run on an inexpensive personal computer. Various communications hookups apply. RS232, Data Hwy, RS485/422, ethernet and many other connections can be used. Depends on your PLC mainly. Wonderware and Intellution have advanced trending, alarming, data storage and machine display capabilities. If you have budget problems Wonderware, Intellution and NI are not cheap. Depends on the number of tags you want to read. There is usually a driver or I/O server program running on the PLC to gather the data for the Data Aquisition program from the PLC. These can be proprietary and costly. Wonderware offers some free I/O servers with its package but not all. An example would be AB TCP/IP and AB Serial. Several others. Again- depends on your PLC.
 
Hi,

It's difficult to access PLC and get the data to PC. How about ask ur programmer to get some info (Dedicated Protocol) or manual from PLC manufacturer and do some programming to get data.

Some softwares already exist on the market. They to do data logging, sounds like Mitsubishi PLC got MX Sheet to do data logging from PLC to PC (in Microsoft Excel format), in case, u have to do a lot of job and make changes in PLC program, it is a hard project.

Actually, I m soft. eng. and seems to do the Data Logging Project from PLC to PC, and more specialise in Mitsubishi PLC. I know u might in a hard way if u do yourself, I suggest u ask a vendor to do for u.
 
hi!!

I think we are close on the problem we are trying to solve, so that's why i am posting it here. Actually i need to simmulate a PLC on PC so that without using a PLC some initial testing can be done. Can you give me some indicators on where to find such a information e.g. book names or URLs for starters?

P.S. i am new to the field so i would be great if u can guide me.
 
Thx you for your comments,

I realised I have to be more specific about my project and I have to scale down the whole topic.

At first, my desire was to have kind of universal basic data acquisition for several data from PLC. However, your comments reminded me that this will need enoumous effort, that's the reason for the third party programs to save us.

Now I have concentrated one part of my project as follow. I will appreciate for your further comments if possible by all means for a quick fix.

On the field, AB FlexLogix 5434 CPU communicates both with Local2 Adapter 1794-FLA and with VersaView CE HMI operator console. I am novice on AB products. Your advise is higly welcome on tips and tricks to gather data from PLC to PC.

Have a nice weekend to all you there.
rgds, m@z 050306
 
Hi m@Z, let me just give you an idea of what can be done. I have solved exactly the same problem but with an OMRON CPM1/CQM1 PLC. Using VB, or any other programming language, you can use your PC's COM ports to send a command to the PLC and the PLC sends the current 'states' of any relay address in it, which you will specify in the command that you sent to it. What i mean with 'states' here is that when the relay is on, the PLC will send a '1' signal, and a '0' if the relay is off. From that, you can manipulate the data the PLC sent using the customized software. Timestamping can be done in your PC already should you want to log the time of day that a certain 'state' occurred.

Hope this help. Good luck.
 
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