# Device Net



## dronai (Apr 11, 2011)

Had to reverse some cables that were already ran, I was told they have a polarity ? Thought that was digital ?
Analog signal ?


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## 51360 (Jun 9, 2014)

dronai said:


> Had to reverse some cables that were already ran, I was told they have a polarity ? Thought that was digital ?
> Analog signal ?


Yes, you must connect them correctly. Similar to data highway, and DH +, but supposed to be much better.

I liked Device Net for the ability to change drive parameters, and monitor other control devices, but I found communication slow in certain situations. 

On high speed candle lines, they often didn't update fast enough.

Technology changes so fast, it's difficult to keep up. Allen Bradley makes some amazing products! :thumbsup:

Borgi


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## IMM_Doctor (Mar 24, 2009)

*Read the instructions*

Devicenet is a multi-node, token-pass, serial data network. There is a single host Scanner, and numerous adapters (slaves) on the network.

There should be a termination resistor at each end of the trunk line, and there can be numerous node taps.

Check the AB web-site Literature Library for instructions for Device-Net media installation instructions.

Device-Net (AB), is cross compatible with CAN bus. (Google ODVA)


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## IMM_Doctor (Mar 24, 2009)

Oh, by the way. Device-Net is a legacy network.

Formerly, OEMs like AB and Siemens, and others, created proprietary networks to stitch IO to their ROBUST PLC equipment.

AB had "Remote IO" for control and "DH+" (Data Highway) for non-critical data.

Siemens had Profibus for IO.

Now, the BUS of the day is AB (ODVA) Ethernet/IP
Or
Siemens Profit-Net 

Both Ethernet/IP and Profinet are modifications to general office-grade Ethernet strategies, with extra layer modification, to achieve industrial control ROBUST and DETERMINISTIC control.


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## dronai (Apr 11, 2011)

Thanks for the info. I am just labor running the cables to the AB Armorstart VFD's 
Didn't think Data cared about a direction.


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## IMM_Doctor (Mar 24, 2009)

dronai said:


> Thanks for the info. I am just labor running the cables to the AB Armorstart VFD's
> Didn't think Data cared about a direction.


dronai,

If your task is merely routing and pulling the 4-wire cable from point-to-point, then follow your professional electrician guidelines. It is serial data, so keep long parallel runs away from power. It is ok to be in the same Raceway for short intersections.

When it comes to termination at each VFD, the design engineer should provide you with succinct documentation, if, and where termination resistors are required.


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## dronai (Apr 11, 2011)

IMM_Doctor said:


> dronai,
> 
> If your task is merely routing and pulling the 4-wire cable from point-to-point, then follow your professional electrician guidelines. It is serial data, so keep long parallel runs away from power. It is ok to be in the same Raceway for short intersections.
> 
> When it comes to termination at each VFD, the design engineer should provide you with succinct documentation, if, and where termination resistors are required.


Surprised this is a Legacy network, when this place is state of the art, spare no expense. 
All cables are in separate cable baskets away from power. There are T's at every controller, with pin type cables for quick connect.


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## JRaef (Mar 23, 2009)

You need to read and study the DeviceNet installation guidelines carefully. One of the drawbacks to DeviceNet is that the wiring requires very specific engineering with regard to trunk lines, wire gauges, drop lines (branches), total linear length, distances from power supplies etc. etc. etc. It's nowhere near simple.
http://literature.rockwellautomation.com/idc/groups/literature/documents/um/dnet-um072_-en-p.pdf


As to your question about communications needing polarity, this is a two-wire communications system (the Blue and White wires) but is bi-directional (full duplex), so if you cross the cables in a connector, it fouls everything up. The cables also include 24VDC power (the Red and Black wires) so because it is DC, it does have polarity.


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## dronai (Apr 11, 2011)

JRaef said:


> You need to read and study the DeviceNet installation guidelines carefully. One of the drawbacks to DeviceNet is that the wiring requires very specific engineering with regard to trunk lines, wire gauges, drop lines (branches), total linear length, distances from power supplies etc. etc. etc. It's nowhere near simple.
> http://literature.rockwellautomation.com/idc/groups/literature/documents/um/dnet-um072_-en-p.pdf
> 
> 
> As to your question about communications needing polarity, this is a two-wire communications system (the Blue and White wires) but is bi-directional (full duplex), so if you cross the cables in a connector, it fouls everything up. The cables also include 24VDC power (the Red and Black wires) so because it is DC, it does have polarity.


 This system has been engineered for all that you listed above. There is an on site engineer testing today at each motor/vfd location.


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## MWayne (Nov 8, 2010)

We spent several months tearing out all Devicenet from two our locations, it tended to "blink out" randomly for milliseconds to minutes and cause shutdowns. Experts aplenty were consulted without any improvement and getting replacement parts difficult to impossible.


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## dronai (Apr 11, 2011)

MWayne said:


> We spent several months tearing out all Devicenet from two our locations, it tended to "blink out" randomly for milliseconds to minutes and cause shutdowns. Experts aplenty were consulted without any improvement and getting replacement parts difficult to impossible.


 What is it being replaced with ?


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## MWayne (Nov 8, 2010)

dronai said:


> What is it being replaced with ?


A remote I/O and good old fashioned multiconductor PLC cable. It's been almost 2 years since the changeover without a problem, I saw where someone has been using an old firmware brick for a doorstop!


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## Jhellwig (Jun 18, 2014)

MWayne said:


> We spent several months tearing out all Devicenet from two our locations, it tended to "blink out" randomly for milliseconds to minutes and cause shutdowns. Experts aplenty were consulted without any improvement and getting replacement parts difficult to impossible.


 
There is nothing more fun that sitting on top of a tank farm in the rain isolating segments to find what keeps shorting out the whole run intermitently.:no:

I wish devicenet would die a firery death.


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