What common methods are there for interfacing a PLC to..

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arbj

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Hi,

We have designed several RS 485 (proprietary protocol) based systems for use in industrial environments.

We provide some basic 0-24 V DC level inputs/outputs for interaction with PLCs.

I am interested to know what communication methods are used, apart from PROFIBUS, MODBUS etc.

Are parallel input-output ports also used...??

thanks
a
 

Parallel I/Os with dedicated command signals as start/stop and respective status signals as ready/busy/error are still the most common interface technique in industrial applications, also analog standard signals 4-20 mA or 0-10V for setpoints and measurements. Obviously they involve less projecting effort and are understood by most engineers, which unfortunately isn't the case with bus interfaces. For small installations, the overall costs are typical smaller with classical interfaces. (Even in First World countries!).
 

I would look at I/O to I/O interfaces such as what you refer to as a brute force method. Yes it is used, but here in the US (I am not adequately familiar with other markets) generally some type of communications medium is used. Especially when if your are planning on sending/receiving any analog information. That can get expensive having to double up on I/O just to pass the info back and forth. The most popular communications medium right now is Ethernet I/P. It is easy to setup, fast and flexible. Maybe if you post a little more about the number of points and an idea of what you are doing with the information, I can be more specific. For example, a couple discrete points would not really warrant any communication setup.

Russell
 

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