Hi all,
In addition to Martin
questions and being more specific regarding the following:
- What is the system grounding policy? i.e. if all system segments
PSE, PD, cables power supplies are on the same ground?
- If many PDs connected to a single Switch, are al PDs isolated from
each other? i.e. No Dc current even the lowest (<100uA) is flowing
through PDs via bad Isolation?
- What is the common mode noise between the positive and negative leads
to chassis? (in PSE and PD)?
- If the cable contains a shield, doe's the shield is isolated from
the PSE positive and negative leads?
- Is the bob smith terminations is separate per channel or the capacitor
part of the termination is common to many channels (ports) and is
channel/port/pin is connected to that capacitor via resistor so from DC
current point of view there is cross leakage current between ports
once a single port or more are on and mess the detection signal of other
ports?
Yair
Chief R&D Engineer
Analog Mixed Signal Group
Microsemi Corporation
Neve Ne'eman Industrial Zone
Hod
Tel: +972-9-775-5100,
Cell: +972-54-4893019
Fax: +972-9-775-5111
E-mail: <mailto:ydarshan@xxxxxxxxxxxxx>.
From:
owner-stds-802-3-poep@xxxxxxxx [mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Patoka, Martin
Sent: Wednesday, July 08, 2009
3:44 PM
To:
STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Subject: Re: [8023-POEP] Fw: Rejected
posting to STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Hi Bob,
It sounds like you have
additional information about the incident not included in the liason letter.
What can you tell us
about the electrical environment of the PSE, channel, and (non-PD) end-point
device discussed in the liason? What can you tell us about the physical
channel implementation?
Can you provide the
specific requirements that you allude to in your posting?
Thanks and Regards,
Martin
Systems Engineering Manager
O: 214-567-5487
mpatoka@xxxxxx
From:
owner-stds-802-3-poep@xxxxxxxx [mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Robert E Lounsbury
Sent: Wednesday, July 08, 2009
5:53 AM
To: STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Subject: [8023-POEP] Fw: Rejected
posting to STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
----- Message from Robert E Lounsbury <relounsbury@xxxxxxxxxxxxxxx> on
Wed, 8 Jul 2009 06:38:06 -0400 -----
|
To: |
|
|
cc: |
owner-stds-802-3-poep@xxxxxxxx,
STDS-802-3-POEP@xxxxxxxxxxxxxxxxx |
|
Subject: |
Re: [8023-POEP] Liaison letter from IEC
TC65/SC65C/JWG10 - Power over Ethernet performance in industrial environments |
Hello Hugh, Dave,
Please read the liaison letter. Please disregard the damaged device.
The damaged device only served to start the discussion in IEC. The
letter is asking two very basic questions that might precipitate some
considerations in the specification. First Dave mentions noise coming
from the device loads back onto the channel. This was one of the questions in
the letter. Dave alludes to violating the specification. Please
point to where in the specification where noise produced and coupled back to
the PoE channel is defined, limited or otherwise discussed. Second the
letter asks if the PoE TG has considered analyzed what might happen if there is
Radiated, conducted or other environmental noise in the area where the PoE
system is installed might cause problems during the probing process. This has
nothing to do with any design flaws of a product but merely the environment.
If you consider Industrial noise levels as defined by IEC out of the
scope for 802.3at, then please respond indicating so. Then we might be in a
position to disallow PoE in industrial. Thanks for your time
Regards
Rockwell Automation
Bob Lounsbury – Principal Engineer
Control and Visualization Business
Tel: +1.440.646.4297
Fax: +1.440.646.3076
Cell: +1.440.610.4485
email: relounsbury@xxxxxxxxxxxxxxx
|
07/07/2009 01:51 PM
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David,
I can see that the liaison from IEC has caused
some interesting
discussion amongst PoE experts (and myself),
however I think that we are
being asked to comment on what may well be design
flaws in specific
products and I do not think that is a healthy
discussion within 802.3.
I suggest that we should send a reply along the
following lines:
==========================================
The problems described in your liaison spurred
some vigorous discussion
amongst our task force members regarding possible
causes for the damage
that you describe. However the members are not
aware of any similar
reports that might indicate a systemic problem
with 802.3 compliant
equipment. It is the opinion of the members of
IEEE P802.3at Task Force
that the standard allows product manufacturers to
build reliable and
interoperable equipment that will meet the
requirements for supplying
power over Ethernet in many environments. However,
the standard does not
define how a manufacturer must build the product
to ensure reliability
or how an installer should ensure that the media
is suitable for correct
operation within the standard. We suggest that you
should work with the
equipment manufacturers involved to determine
whether the failure is the
result of a systemic problem with the standard and
whether a specific
amendment may be required.
With respect to the bit error rate performance of
802.3 links when power
is being supplied over the same link, the members
of IEEE P802.3at Task
Force believe that a compliant system supplying
power over an 802.3 link
will not perturb the channel sufficiently to
degrade the performance of
the underlying link. However, it is the
responsibility of the product
manufacturer to ensure that noise introduced by
the load does not couple
to the link and violate the power over Ethernet
specifications or the
channel specifications required for the link.
Similarly it is the
responsibility of the system installer that the
channel characteristics
are met in the presence of environmental noise.
===========================================
Hugh.
>All,
>
>The IEEE 802.3 Working Group has received a
liaison letter from IEC
>TC65/SC65C/JWG10, Industrial process
measurement, control and
>automation/Industrial networks with respect to
Power over Ethernet
>performance in industrial environments.
>
>I just wanted to inform you that I intend to
delegate the generation of a
>draft response to the IEEE P802.3at DTE Power
Enhancements Task Force
>during the plenary week in July. The draft
response will be consider and
>then voted upon at the closing IEEE 802.3
Working Group plenary as part of
>the IEEE P802.3at closing report. You
therefore may wish to review the
>letter prior to the meeting, the letter can be
accessed at the URL [
>http://www.ieee802.org/3/minutes/jul09/0709_IEC_SC65C_JWG10_to_802_3.pdf
>].
>
>Best regards,
>
> IEEE 802.3 Working Group Chair
>
>
>