IO power with ethernet

TConnolly · Jan 25, 2006

I'm desigining a system right now that uses ethernet IO and I need about 2 amps of 24VDC at the IO cabinet, which is 45' (14m) away, but the route is somewhat convoluted - a conduit benders nightmare. I'm planning on only a single 3/4" couduit.

Is there an adaptor which will allow me to supply the dc on the unused conductors of the Cat-5 cable?

Or is that a really really bad idea?

elevmike · Jan 25, 2006

Alaric said:
....Or is that a really really bad idea?

I'd think so. Considering the wire size of the cable I wouldnt feel comfortable with it. Also if it's a switching power supplies you may get some noise on the E-net.

Note: I've done this in our own building (about 200') and seemed to have gotten away with it, however I would never do it to a customer.

bernie_carlton · Jan 25, 2006

Google 'Power Over Ethernet'. It shows schemes that allows low wattage transmission of power for specific ethernet devices (hubs etc) at the other end. It probably wouldn't be prudent for your application though.

Contr_Conn · Jan 25, 2006

At 45ft voltage drop will be about 4V.
Plus it will put a lot of noise to the signal lines.

OkiePC · Jan 25, 2006

Before I did that, I'd pull a three conductor 18 gauge shielded cable with the cat5 cable in the same conduit. Probably not the right thing to do either though ... but it would most likely work fine.

jolio ST · Jan 25, 2006

I find this weblink really interesting. I will consider playing it around over the coming holidays!

If it is good I will incorporate it into the company's ever-failing network.
A little extra calculations, I should think it's not a bad idea.

TConnolly · Jan 25, 2006

OkiePC said:
Before I did that, I'd pull a three conductor 18 gauge shielded cable with the cat5 cable in the same conduit. Probably not the right thing to do either though ... but it would most likely work fine.

Well, that what I had planned on doing, but as I started thinking about wat a pain it was going to be to get the wires into this already convoluted conduit routing, I wondered if there was such a thing as power over ethernet.

MarkTTU · Jan 25, 2006

PoE is an IEEE standard now. Green and Orange are your data wires. PoE spec says that Blue + Blue/White is +vDC and Brown + Brown/White are -vDC.
http://www.altair.org/labnotes_POE.html
IEEE spec is 48v and 12.95W max. I've run 24vdc in one side and powered a 10" EZ-Touch screen (~1A) on the other a few times without problems at about 30-40 feet.

I'd go with a shielded CAT5 cable and a shielded 18ga cable for your power. Much more reliable in the long run.

IO power with ethernet

TConnolly

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