Communication Types?

[shoelesscraig]

Ok, I have searched for a simple answer to this, but must be looking in the wrong spot. My question is simple (I think):

What is the real difference between DeviceNet, ControlNet, Ethernet, etc? Why would you choose one over the other? I know some are faster than other, but I don't know which.

 

[BobB]

You can check at
www.odva.net for Device Net, Ethernet I/P and ConpoNet.
Device Net is not quick, Ethernet is to me useless, Ethernet I/P is not bad, CompoNet is really excellent - it is a bigger and better Device Net at half the price - twisted pair - over 30 metres 1000 I/O updated in 1 ms - it ios also a token ring network, my favourite - no crashes.
How about Modbus - slow - Profibus - I do not like it much - a million others.
What do you want - remote I/O or peer to peer - if you want great remote I/O I would always prefer CompoNet but only one supplier has gone that way.
Device Net would probably be second choice but damned expensive!!!
Schneider have Advansys etc etc.
Why do you ask?

 

[rdrast]

This is by far not any kind of official definition, but a simple rule-of-thumb that I go by:

DeviceNet - Slow, cyclically polled, for talking to small Devices (encoders, limit switches, PushButtons, etc). Very robust, if you pay detailed attention to power supplies, cabling guidelines, and connectors.

ControlNet - Fast, scheduled on a per-block level, for handling control related I/O functions (remote racks, drives, etc). Extremely robust, even if redundancy is not used.

Ethernet (/IP) - Fast, wild as a jungle, can be sort-of scheduled, for handling HMI's, Database connections, programming, and massive data transfers. Subject to many externally caused failures.

 

[shoelesscraig]

Why do you ask?

Just learning, no particular reason. We have a few DeviceNet cards in our ControlLogix processors at work. Not really sure where they are going (the cable goes into the ceiling and out into the plant...somewhere). I never have to work on them, so they are still kind of a mystery to me.

 

[CBowman]

There are some excellent webinars on the following site... free to signup... and if you email them... they will provide TONS of excellent Support!

http://www.trelectronic.com/technicalresources.php#3