Created Date: November 20,2008

Created by: Shimmy

Link: http://www.machineryautomation.com.au/automation-technology/devicenet-vs-ethernet.html

DeviceNet: The Do-All FieldBus for Low and Mid-Level Factory Networking

Origin: Allen-Bradley, 1994

Maximum number of nodes: 64

Connectors: Popular ‘Mini’ 18mm and ‘Micro’ 12mm waterproof quick-disconnect plugs and receptacles, and 5 pin phoenix terminal block

Distance: 100M to 500M

Baud rate: 125, 250 and 500 Kbits/sec

Maximum message size: 8 bytes of data per node per message

Messaging formats: polling, strobing, change-of-state, cyclic, and others; producer/consumer-based model

Supporting trade organisation: Open DeviceNet Vendor Association, www.odva.org

Typical applications: Most commonly found in assembly, welding and material handling machines. Single-cable wiring of multi-input sensor blocks, smart sensors, pneumatic valves, barcode readers, drives and operator interfaces

Advantages: Low cost, widespread acceptance, high reliability and efficient use of network bandwidth, power available on the network

Disadvantages: Limited bandwidth, limited message size and maximum length

Ethernet: The Worldwide Defacto Standard for Business and PC Networking

Origin: Digital Equipment Corporation, Intel and Xerox, 1976

Implemented on multitudes of chips produced by many vendors. Based on IEEE 802.3

Formats: 10 Base 2, 10 Base T and 100 Base T, 100 Base FX, 1 Gigabit; copper (twisted pair / thin coax) and fibre

Connectors: RJ45 or coaxial

Maximum number of nodes: 1024, expandable with routers

Distance: 100M (10 Base T) to 50 KM (mono mode, fibre with switches)

Baud rate: 10M to 100M Bit/sec

Message size: 46 to 1500 bytes

Messaging format: peer-to-peer

Supporting trade organisation: Industrial Ethernet Association ( www.IndustrialEthernet.com ) and IAONA ( www.iaona.com ).

Typical applications: Almost universal in office / business LANs. Widely used also in PC to PC, PLC to PLC and supervisory control applications. Gradually working its way toward “sensor level” in plant floor applications

Advantages: Ethernet is the most widely accepted international networking standard. Almost universal worldwide. Ethernet can handle large amounts of data at high speed and serve the needs of large installations

Disadvantages: High overhead to message ratio for small amounts of data; no power on the bus; physically vulnerable connectors and greater susceptibility to EMI/RFI than most fieldbuses; confusion based on multiple open and proprietary standards for process data.

I like ethernet because it is very convenient and cheap and easy to use. In the above summary they list an advantage of DN is that is is low cost. In my opinion, compared to ethernet, that is not true.

My pros and cons:

DN pros:

Stable, good support, easy to use

DN cons:

Cost, number of nodes, slower speed

ENet pros:

very low cost, very common, easy to intergrate into a PC system, fast, can be wireless, lots of nodes

ENet cons:

Slightly more unstable than the "industrial " protocols, inefficient data xfer (though the speed makes up for it)

Created Date: November 20,2008

Created by: jesawyers

ksmith...one thing you must determine before jumping into a industrial protocol is do you need determinstic data transfer.

Ethernet by it's nature is not determinstic and I'm not sure about DN.

I'm currently working as a contractor for a major OEM and they use MODBUS/TCP for those devices that do not need determinstic behavior and canOpen for those devices that need to be determinstic.

If you don't need determinstic behavior, go with MODBUS/TCP. It's simple, easy to understand, and is not tied to a vendor's particular hardware.

John