Ethernet as control cable

Bolt · Jan 14, 2014

Does anybody have experience using regular ethernet cable for automation purposes, namely pushbuttons, and maybe some LED indicators?

The pros I see: readily available, 8 conductors, easily field terminated, easily run through conduit, swappable, etc.

Any reason why it wouldn't work? Any slick way to go from an rj45 connector to wire terminals?

Thanks for any advice!

James Mcquade · Jan 14, 2014

Bolt,

all work must be done in accordance with NFPA70 - national electric code and NFPA 79 - electrical standard for industrial machinery.

as far as i know, ethernet cable is not approved for such uses.

regards,
james

Bolt · Jan 14, 2014

I see, I figured with the prevalence of power over ethernet devices today, that there would be some sort of low voltage approval out there.

shooter · Jan 14, 2014

cable is fine if voltage is below 24 volts.
i use it for 5 volts.
The cable is only one strand so impossible to have it moving.
even POI works great <1 amp.

Bolt · Jan 14, 2014

Actually, I have some braided 23 awg cat 6 cable that I've been using for all my networking for a while. That way flexing won't be as big an issue either.

Helliana · Jan 14, 2014

shooter said:
cable is fine if voltage is below 24 volts.
i use it for 5 volts.
The cable is only one strand so impossible to have it moving.
even POI works great <1 amp.

There is also stranded Cat5e and Cat6 used for making patch cables. We keep both in stock and use punchdown blocks on the soild, then use stranded from the punchdowns to the switch.

rpoet · Jan 14, 2014

Bolt said:
Does anybody have experience using regular ethernet cable for automation purposes, namely pushbuttons, and maybe some LED indicators?

The pros I see: readily available, 8 conductors, easily field terminated, easily run through conduit, swappable, etc.

Any reason why it wouldn't work? Any slick way to go from an rj45 connector to wire terminals?

Thanks for any advice!

Don't do it. Just don't. Use like cables and ESPECIALLY connectors for like signals. The next guy is going to expect Ethernet cable to be used for Ethernet, not 24v I/O. I've spent the last two years cleaning up just this kind of mess where I work. The last guy used stripped out CAT5 for everything. It's hard to put into terminal blocks without stray strands, and hard to strip without damaging the conductors. Use Ethernet for data, and use 18ga wire for I/O. I recommend MTW wire for use in a panel, and if pulling wire though conduit, THNN or THWN are good choices.

Please don't be cheap and use CAT5 for I/O wiring. Beyond everything else, it looks terrible and cheap.

-rpoet

yasirkhi · Jan 14, 2014

Never

Please do not use twisted pair cable for IO.

PLC Pie Guy · Jan 15, 2014

As an electrician I have always strived to keep my panels and projects neat and give the appearance that shows a class of workmanship. Plant or home environment! I to have spent hours pulling out old CAT5 that somebody previous to me had used for I/O in my plant. It just shows that the person that did the work was obviously not qualified or experienced enough to be doing the work. Definatley not done by an electrician.

JesperMP · Jan 15, 2014

Bolt said:
The pros I see: [...] swappable

You mean that ethernet cables terminated with RJ45 connectors are easy to swap.
Consider M12 connectors. This is the closest to an industry standard that I know of.
There are both cables with prefitted M12 connectors, and M12 connectors with terminals to be fitted onsite.

Bolt said:
Any slick way to go from an rj45 connector to wire terminals?

So you intend to keep the c**p plastic RJ45 connector, and somehow via an adapter branch out to regular terminals.
Suggest this to your colleagues, and they will loose any respect that they may have had for you.

Since you are in the US, I think there is also an issue with minimum wire gauge, even for low voltages.
Again I suggest M12 connectors. There are prefitted cables+M12 connectors that are UL certified.

Bolt · Jan 15, 2014

Points taken. I don't think a well done ethernet install would be an shoddier looking than using 18-8 thermostat cable.. And properly done, it should not be hard to realize it is not network related. Don't have room for the bulk of a 18-8 SO cable, trying to find an alternative. M12 QD gets too complex, need to run a junction block, trying to save on space, and the connectors are hard to run through conduit. Trying to replace existing pneumatic controls with 24vdc.

JesperMP · Jan 15, 2014

Bolt said:
M12 QD gets too complex, need to run a junction block, trying to save on space

Then place M12 bulkead connectors in the block.

Bolt said:
and the [M12] connectors are hard to run through conduit.

Not harder than RJ45 connectors, and you can opt to use separate M12 connectors to be fitted onsite, just like RJ45.

Ethernet as control cable

Bolt

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James Mcquade

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shooter

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