Re: [8023-POEP] Fwd: A timely article
Hi all,
I believe the pro's worth more the con's for the PoE technology.
Some of you admit that PoE is OK for low power applications.
I guess that what efficiency is the number 1 problem to those who don't
want more power.
The simple fact is:
If PoE is good for up to 12.95W according to 802.3af then from
efficiency point of view increasing the current and voltage to have more
power at the PD side for better cable such as in CAT5 (12.5 ohm)
compared to 802.3af 20 ohm cable resistance, allows more power with the
same efficiency.
So efficiency is not the issue.
The issue is the overall system cost and the value for customers and
their various applications.
It looks that there is a value and there is a growth in PoE market size
and applications which tells me that we are OK.
By the way, centralized power management saves much more power then
using wall wart for PDs that is working all the time. We have shown that
smart power management may increase average power capability by a factor
of 2 and yet using the same power supply size and cost.
Yair
-----Original Message-----
From: owner-stds-802-3-poep@xxxxxxxx
[mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Geoff Thompson
Sent: Thursday, November 09, 2006 9:17 PM
To: STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Subject: Re: [8023-POEP] Fwd: A timely article
Dan-
Thank you for so eloquently speaking to (and reenforcing) precisely my
point-of-view.
Geoff
At 09:44 AM 11/9/2006 , Dove, Dan wrote:
>Did I see a soapbox standing idle?
>
>I actually read (misread?) Geoff's reference to timliness a bit
>different.
>
>Here we are in a world that is growing more and more sensitive to
energy
>waste, and rather than working on a way to improve efficiency, we are
>simply putting out more power at a lower efficiency.
>
>Sending 50V through wires that were intended for low-power
>communications rather than high-power distribution is lossy.
>
>The current paradigm, taking AC power at 120/240VAC and converting it
to
>50VDC with an efficiency hit, then running it through a distibution
>network inside a switch (lossy again) then switching it through a FET
>(lossy again) then running it through UTP (lossy again) then a DC/DC
>converter (lossy again) seems to be going backwards.
>
>I think that PoE is a great technology for low-power devices that are
>hard to wire up, but makes little sense for devices that are easily
>attached to a wall outlet (laptop?). Rather than driving toward higher
>and higher PoE power, we should be driving toward lower and lower
>powered PDs... But that is not a standards issue, that is a product
>design issue.
>
>All that said, I am not trying to be negative here... But I do have my
>reservations about just how much power we should be stuffing down these
>data lines.
>
>Dan
>
>
>------------ Previous Message Below ------------
>
>-----Original Message-----
>From: owner-stds-802-3-poep@xxxxxxxx
>[mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Charles Palmer
>Sent: Thursday, November 09, 2006 8:01 AM
>To: STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
>Subject: Re: [8023-POEP] Fwd: A timely article
>
>Team - just my thoughts:
>
>Anything you can do to minimise the standby state power consumption
>(both ends) could represent many MWhr or GWhr over the years...
>
>And as for the power loss in those PD bridge rectifiers...
>
>This is big news in the UK at present:
>http://news.bbc.co.uk/2/hi/business/6096084.stm
>
>And: European legislation is on the way:
>http://ec.europa.eu/enterprise/eco_design/index_en.htm
>
>Regards - Charles Palmer
>
>Geoff Thompson wrote:
> > ...for our group too.
> >
> >
> >> Subject: A timely article
> >> To: <eee@xxxxxxxxxxxxxxx>
> >>
> >>
http://www.businessweek.com/globalbiz/content/nov2006/gb20061107_4475
> >> 69.htm
> >> ?chan=tc&campaign_id=rss_tech
> >
> >