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Connecting together all PLCs of different vendors in your facility.

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Some basic advice to help you on your research... (Note this is old article, technology options have changed a little in the last ten years. :)


Networks | concentrators | server | additional sources


slc 500


From this




Part of your solution is dependent on how many plcs you have from each vendor. The first step is to get all plcs of each vendor type on their own respective network. (ie: mitsubishi's melsecnet, ab's devicenet, modbus, omron's hostlink, etc.) if you only have one plc of a particular vendor, then you might consider an sst x-link converter for that one plc or an ethernet adapter card for that specific plc, or a universal solution like Woodhead's da server. (example: you have 12-mitsubishi, 6-omron, and only 1 i-dex. Get converter for i-dex so it can rest on mitsubishi network or use ethernet to run directly to your computer software.)


The next step is connecting all of the networks together, via ethernet. Depending on the details of how many of what vendors will determine other factors. Such as setting up a "data concentrator" (plc or bridge computer) for one line or section of the plant. With only a few plcs, you may decide to run ethernet to each plc and avoid the data concentrator.


The third step would be deciding your method of reporting data, accessing all plcs, etc. Step two above has to be considered while considering this step. You may use wonderware of some other prepackaged pc software. (more info below) Top


proprietary plc networks:

This is the plc vendor's way of connecting their brand of plcs together to share information. As each plc vendor has their own protocol, programming references, addressing, and instructions. Some vendors differ in these protocols amongst their own models. Most plc vendors have one proprietary network that works on all models of their own plcs. Allen Bradley has two basic networks that move can be connected to more advanced networks. (ab micrologics interconnect via devicenet, devicenet can connect to controlenet for example. Put it all together and it equals controllogix gateway) ab's plcs greater than mico size can connect via dh+ (datahighway plus).


Some other plc networks:
siemens -profibus
mitsubishi - melsecnet, cc-link, profibus
Allen Bradley - controlnet / devicenet
omron - hostlink


Alt solution - sst x-linx converter: converts proprietary protocol of one plc vendor network to another. Put an ge plc on a data highway plus for example. (sst currently has ethernet drivers for plc (programmable controller) networks including allen-bradley, modicon, reliance, ge, siemens. Fieldbus connectivity, i/o si)


Alt solution 2 - implement modbus network with ab plcs  (via module by prosoft).


Alt solution 3 - serial hubs can be connected to ethernet making rs-232 connections and rs-422/485 networks 'transportable'. (use fiber optic converters to convert the rs422, 2.5 miles noise free


Alt solution 4 - omron plcs can be tied in by rs-485 or multi-port point-to-point and alias to blocks of registers in an emulated plc5 that resides on the dh+ bus. Or use cimquest.


Cool solution - ever think you would be accessing omron, ab, mitsubishi, or modbus with a palm pilot?  Top


data concentrators:

Data concentrator are responsible for polling the individual plcs and presenting the data in a consistent way to the server.

Plcs as data concentrators collecting data from over 100 plcs over the proprietary comm. Network supplied by the plc manufacturer. The data concentrators plc is then connected via ethernet tcp over an isolated sub-lan server. (typically running under unix).

Some examples we have found are using a siemens s7-300 plc with a profibus card to connect to those plcs which have a profibus port. A s7-215 with a profibus dp connection to the scada node for small amount of i/os being monitored. Siemen's sinec h1 is yet another choice, there are a lot of development in this area as you can see from just one plc vendor example. You will need a different plc concentrator for other plc proprietary networks like controlnet or mitsubishi's melsecnet.

An alternative option if you have less than 80 plc's is to run ethernet to each plc and avoid the data concentrator. Above 80 plcs the update time may be beyond acceptable limits. Note: serial hubs can be connected to ethernet making rs-232 connections and rs-422/485 networks 'transportable'.  Top


the server:

The server or a workstation connected to it, is where you would access any plc in you plant. Although we would recommend only in a read only configuration, you could link servers together for corporate wide monitoring or even condition monitoring via the internet. The option of monitoring plant processes via the internet is becoming quite popular. also companies like provide automated email and phone notification based on user set alarm algorithms.


The software on your server to collect the data should be a commercial scada software like wonderware, kepware, fix or genesis (see the scada list). Standard dde protocol servers, (like wonderware or kepware), allow the connection of any dde aware software. These type can pass on the information to any application you have on your computer now or in the future.


One suggestion was a software-based solution. If you have access to opc servers for your plcs, a software gateway (or bridge) can be used to move data between the plcs. The gateway and opc servers would run on one or more windows-based pcs. The servers communicate with the plcs. The gateway moves the data between the plcs.


In addition to the plcs, data is also collected from inspection cmms, operator input, production scheduling systems, and mainframe systems either directly through the ethernet sub-lan or by serial comm. Through the plcs.  Top


This article written many , many years ago.


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