RE: Power over ethernet

[<nick.rees@diamond.ac.uk>]

I would be concerned about running this sort of power over Cat5 because of the current limits. Wikipedia puts the current rating of Cat5 at 0.577A per conductor, so if you use all 4 pairs that is 2.3A, which is right on the limit for 120W with a 48V supply.

If you factor in the fact that most structured cabling installations are far from ideal, and how stupid you look when everything goes up in smoke because of a cable fire, then being a bit conservative makes sense.

Having said that, we make extensive use of PoE on Diamond beamlines for diagnostic GigE and web cameras. Beamlines either have a stack of Avaya 5520 or Avaya 5650 PoE switches (depending whether they have 2*1GbE or 2*10GbE uplinks to the core network).


Cheers,

Nick Rees
Principal Software Engineer           Phone: +44 (0)1235-778430
Diamond Light Source                  Fax:   +44 (0)1235-446713



-------- Original message --------
From: Emmanuel Mayssat <emayssat@outlook.com>
Date:
To: "Boyes, Matthew" <mboyes@slac.stanford.edu>,"Hill, Bruce" <bhill@slac.stanford.edu>
Cc: tech-talk@aps.anl.gov
Subject: RE: Power over ethernet


Got it, that device is actually to add PoE to a non PoE switch.
The link aggregation discussion I was looking at was for another product.

________________________________
From: emayssat@outlook.com
To: mboyes@slac.stanford.edu; bhill@slac.stanford.edu
Subject: RE: Power over ethernet
Date: Wed, 31 Jul 2013 11:11:26 -0700
CC: tech-talk@aps.anl.gov

This switch supports PoE and PoE+... and is crazy cheap!
But the docs available before buying is almost non existent.
I use link aggregation/trunking for my network backbone and even so it says it is supported, I am wondering how many links can be aggregate and whether to expect compatibility issues with my other switches.

Moving forward with PoE, I found a company which offers Ultra and even Mega PoE.
http://www.midspans.com/
http://www.midspans.com/pages/products.php
http://www.axis.com/products/video/about_networkvideo/poe.htm
I am not sure those are standard yet,  but up to 120W on CAT5 that's worth talking about!
So this morning, over coffee I shared the news about those PoE switches with the electronics guy.
To my surprise, one of them started drooling.
Granted, that was quite a sight, but I know what that meant: like me, he wanted one!

________________________________
From: mboyes@slac.stanford.edu
To: bhill@slac.stanford.edu; emayssat@outlook.com
Date: Tue, 30 Jul 2013 17:43:01 -0700
Subject: RE: Power over ethernet
CC: tech-talk@aps.anl.gov


Hello Emmanuel,



For LCLS-II electron controls we are moving to Gig-E cameras powered via PoE. We have successfully tested the following 24 port PoE injector with our new beamline camera system. It does support the IEEE 802.3at High Power PoE standard as well as the IEEE 802.3af standard.  We hope to deploy a system this summer into LCLS-I.



HPOE-2400G 24-Port 802.3at 30w Gigabit High Power over Ethernet Injector Hub<http://planetechusa.com/power-over-ethernet/poe-hubs/hpoe-2400g-24-port-802-3at-30w-gigabit-high-power-over-ethernet-injector-hub-full-power-500w.html>



Hope that helps,



Matt



From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of Bruce Hill
Sent: Tuesday, July 30, 2013 4:53 PM
To: Emmanuel Mayssat
Cc: tech-talk@aps.anl.gov
Subject: Re: Power over ethernet



Hi Emmanuel,
We've been using POE for webcam's and gigE cameras for
several years now and find it very useful, particularly
at our experimental chambers where we often need to move
cameras around.    Most of these devices are class 2, < 3.8W,
and we power them by adding POE modules to our Foundry
switches.   There's also available POE injectors which can be
added inline if your switch doesn't support POE.

We haven't used POE+, so I have no direct experience, but with
the small gauge of the wires in the ethernet cables you may
need to limit your cable lengths for higher power devices.

Regards,
- Bruce

On 07/30/2013 04:07 PM, Emmanuel Mayssat wrote:

Hello,



After pushing for it, I was 'authorized' to investigate and test power over ethernet.

PoE is basically 48 V DC / 400 mA over CAT5/6, i.e. for <13Watt devices.

Is anyone of you using PoE? or PoE+ (<25W) ?

If so, any comment?



My long term goal is to have, with a minimum hassle,  embedded linux/EPICS in each of my chassis.

--

Emmanuel





--

Bruce Hill

Member Technical Staff

SLAC National Accelerator Lab

2575 Sand Hill Road M/S 10

Menlo Park, CA  94025

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