Fieldbus vs TCP/IP

[uuunnniiixxx]

I have just begun my career into industrial automation and hear a lot of term especially FieldBus. I had been programming Client / Server application using TCP/IP and understood that for communication between apps / desktop we can use of TCP/IP protocol. So depending whether we code a client / server - we would need to create a socket - bind / connect to it and communication (send / receive) can be started.

I am failing to understand why we cannot use TCP/IP communication in Industrial communication - I hear a lot of term like Fieldbus / ModBus / EtherCAT / ProfiNet etc. and fail to understand that how would they connect to devices - isn't it that they also follow the normal TCP/IP socket communication. If so then we already can connect to other apps / devices using Socket then why do we need a different protocol - is it that the Fieldbus / ModBus / EtherCAT / ProfiNet etc protocol do not make use of socket call for connecting to other side - but if they do then why these terms, can't we simply state its communication over TCP/IP.

So what is Fieldbus / ModBus / EtherCAT / ProfiNet etc and its way of connecting remote applications and sending / receiving data?

 

[kjv1611]

This might be a good place to start:

http://www.controldesign.com/articl...-the-right-network-for-the-right-application/

I've never heard of it myself, but sounds interesting nonetheless.

"But thanks be to God, which giveth us the victory through our Lord Jesus Christ." 1 Corinthians 15:57

 

[meneerB]

In our previous building, we used KNX. All those busses use proprietary cabling systems, 2 or 4 wire systems. I suppose it's like rs485, up to 1000yards cables or so. It's another bus system where you can find lots of info for on the net.

As a network guy, I see a lot of similarities. The systems use variants of the OSI layer to connect, although the users often don't know that.
For large topologies they use variants of routers and bridges to connect several subsystems to each other, because of the cable length limits or bus address limits.
Hope this helps to understand bus systems a little bit, because if you understand OSI and TCP/IP, you quickly understand how a specific bus systems works.

So to get something to work you need a gateway which is connected to the bus (and the other side to the network)

And I suppose depending on the gateway, you can use several ways to connect to the gateway, to fire all kinds of commands, which will then be forwarded on the bus.

We programmed an electric barrier system (PLC, TCP get I think we used) to count visitors, which was presented on the KNX console at the receptiondesk.
We found that the plc was way too slow to interact real-time.

I suppose the specs of the gateway are also very important.
This is what is also possible. Funny example.