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olePigeon · Jan 12, 2006, 12:15 PM

And if it's different for Cat 5, 5e, and 6. I tried Google, but it's saturated with PoE articles. I'm just looking for the voltage for a run of the mill ethernet.

Anyone know?

olePigeon · Jan 12, 2006, 12:20 PM

Oh, and in the context of networking. Not running video or whatever.

Tesseract · Jan 12, 2006, 12:43 PM

I Googled ethernet voltage and first result is a white paper that suggests it is 2.2 volts. I'm not entirely sure that I'm interpreting what I read correctly, but the voltage is in the range of what I would have expected.

I doubt it would differ for Cat5(e) vs. Cat6 because those are just different grades of cable.

Why do you want to know, anyway?

olePigeon · Jan 12, 2006, 12:51 PM

Originally Posted by Tesseract

I Googled ethernet voltage and first result is a white paper that suggests it is 2.2 volts. I'm not entirely sure that I'm interpreting what I read correctly, but the voltage is in the range of what I would have expected.

I doubt it would differ for Cat5(e) vs. Cat6 because those are just different grades of cable.

Why do you want to know, anyway?

An invention I came up with.

I'll let you know what it is after I patent it and make my first few million.

olePigeon · Jan 12, 2006, 12:58 PM

The white paper was moving from 10Mb to 100Mb ethernet. From 2.2v to 3.15v. I guess Gigabit would be close to 4v at 1000Mb. I don't know a thing about electronics. I guess the best thing to do would be to hook up an Ohm meter.

DeathToWindows · Jan 12, 2006, 04:04 PM

I've seen some pretty peverse ethernet hacks... are we just talking sourcing voltage over the bus?

If that's the case, get a multimeter.

mdc · Jan 12, 2006, 04:13 PM

it hurts, that's all i know.
i was working behind my computer and needed a free hand, so i put the network cable in my mouth. no, i wasn't thinking. shocked my tongue so badly.

Tesseract · Jan 12, 2006, 04:35 PM

Originally Posted by mdc

it hurts, that's all i know.
i was working behind my computer and needed a free hand, so i put the network cable in my mouth. no, i wasn't thinking. shocked my tongue so badly.

At least it wasn't the phone cord. If the phone had decided to ring, that would be a pretty nasty shock.

olePigeon · Jan 12, 2006, 06:29 PM

Originally Posted by Tesseract

At least it wasn't the phone cord. If the phone had decided to ring, that would be a pretty nasty shock.

He's lucky it wasn't PoE, he'd get a full 120 volts.

Spliffdaddy · Jan 12, 2006, 07:52 PM

I routinely run 15VDC@500 mA through cat5 cable when doing closed circuit camera installations using baluns. I'm not sure of the current limit of cat5, but all you'd need to know was the wire gauge (diameter). It's probably 22ga - just guessing.

olePigeon · Jan 12, 2006, 08:03 PM

I wanted to light up an ethernet cable with an LED or something when it's plugged into the jack. So out the back of my PowerBook I'd have a blue LED light up when it's connected.

I've seen USB cables like that, but I know USB definitely has the power to do that. I just wasn't sure about the ethernet cable.

ghporter · Jan 12, 2006, 08:29 PM

You can find ethernet cables that light up by searching the Internet. I think they use LEDs in the connectors and fiberoptic jackets...

In any case, the signaling voltage is differential, meaning that each twisted pair carries data by changing which wire has the more or less positive voltage. It does NOT carry a fixed DC voltage you could use to light something without some sort of adaptation.

Tesseract · Jan 12, 2006, 08:44 PM

And you'd probably wreak havoc on the signal by trying to draw power from it (especially in a naive way), leading to a bunch of dropped frames (at best).

nerd · 11:13 AM

I got bored at work (had to come in to babysit people) so I cut open a cable and put a scope on it. This was from a Mac Mini to a Powerbook 1.67. 2.24v p-p for this line. Here's a capture for kicks.