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ethernet frequency and power on ethernet

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October 25, 2004 5:04:10 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Hello,
I am want know the frequency of the ethernet data so that i can decide
on the value of the inductor through which i can feed DC power.
I have heard the ethernet can range from DC to 10 Mhz (10TBase), in
this case i cannot feed power on ethernet. Yes i know about power on
ethernet but the power i want to transfer is 60 W, so i feed the power
directly to the line

I need what is value of the inductor i have to choose.

Waiting for reply
Regards
Praveen
Anonymous
October 25, 2004 12:11:08 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

praveenkumar1979@rediffmail.com (praveen) wrote:
>Yes i know about power on
>ethernet but the power i want to transfer is 60 W

I'm not sure you can, and still be legal. The ampacity of the wire is
going to limit your current, the various codes for low-voltage wiring
are going to limit your voltage, and the intersection of the two is
going to give you your maximum power (minus line losses). 802.3af
peaks out at about 20 watts input to the cable (15.4W per device),
though you might be able to cheat and use all four pairs to double
your power. The standards are a nightmare to parse, but it might be
possible. Dunno what standards you have in India, or if this is for
commercial operation or not. Can you pull another cable?
Anonymous
October 25, 2004 12:29:13 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <ff8a3afb.0410250004.3e8be6d1@posting.google.com>,
praveen <praveenkumar1979@rediffmail.com> wrote:
:I am want know the frequency of the ethernet data so that i can decide
:o n the value of the inductor through which i can feed DC power.
:I have heard the ethernet can range from DC to 10 Mhz (10TBase), in
:this case i cannot feed power on ethernet.

I don't know about DC, and I don't recall the details about 10BaseT,
but at the higher bit rates, the frequency is not just
1/(megabits per second): instead, they use a slower carrier and
more bits per symbol. Some error correction is used, so the raw
number of data points sampled exceeds the nominal bandwidth.

10/100/1000 BaseT are all async, so when there is no data going through,
there are no pulses on the line. I never looked deeply enough to
find out whether it uses a DC carrier or if the line floats free.

If you are using 10BaseT, then several of the wires on a typical
Cat5 8-wire RJ45 setup are not used at all (not even as grounds):
if you need to carry power, could you perhaps use those wires?
This might not help if you are running Cat3 instead of Cat5.

--
Can a statement be self-referential without knowing it?
Related resources
October 25, 2004 12:33:33 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

"praveen" <praveenkumar1979@rediffmail.com> wrote in message
news:ff8a3afb.0410250004.3e8be6d1@posting.google.com...
> Hello,
> I am want know the frequency of the ethernet data so that i can decide
> on the value of the inductor through which i can feed DC power.
> I have heard the ethernet can range from DC to 10 Mhz (10TBase), in
> this case i cannot feed power on ethernet. Yes i know about power on
> ethernet but the power i want to transfer is 60 W, so i feed the power
> directly to the line

do some hunting for 802.3af - standard for power over ethernet - it can
provide up to 13W or so to your device.

even if you dont use the standard, it explains how to do this....
>
> I need what is value of the inductor i have to choose.
>
> Waiting for reply
> Regards
> Praveen
--
Regards

Stephen Hope - return address needs fewer xxs
Anonymous
October 25, 2004 4:02:58 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

[Walter Roberson]

| 10/100/1000 BaseT are all async, so when there is no data going through,
| there are no pulses on the line. I never looked deeply enough to
| find out whether it uses a DC carrier or if the line floats free.

As far as I know, 100TX and 1000T are both synchronous - there is a
signal on the wire at all times.

Steinar Haug, Nethelp consulting, sthaug@nethelp.no
Anonymous
October 25, 2004 4:41:26 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Walter Roberson <roberson@ibd.nrc-cnrc.gc.ca> wrote:
> praveen <praveenkumar1979@rediffmail.com> wrote:
> :I am want know the frequency of the ethernet data so that
> :i can decide on the value of the inductor through which i
> :can feed DC power. I have heard the ethernet can range
> :from DC to 10 Mhz (10TBase), in this case i cannot feed
> :p ower on ethernet.

Well the maximum transition rate on 10baseT is 10 MHz, on
100baseTX is 100 MHz, and 1000baseT is 125 MHz. But these
are essentially encoded digital signals without carrier.
So actual lines in use see many "missed" transitions and
even longish runs (6+) without.

I think inductors would soak up too much of the signal.

> If you are using 10BaseT, then several of the wires on a typical
> Cat5 8-wire RJ45 setup are not used at all (not even as grounds):
> if you need to carry power, could you perhaps use those wires?
> This might not help if you are running Cat3 instead of Cat5.

It doesn't matter. Both 10baseT and 100baseTX only use two
pairs for signalling. Both Cat3 & Cat5 cables typically have
four pair. Only 100baseT4 (obsolete) and 1000baseT use all four
pairs. Watch-out, though. Some hubs/cards ground unused pairs.
And you'll be stuck with NEC low-voltage limitations.

-- Robert
Anonymous
October 26, 2004 8:18:45 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

William wrote:

> praveenkumar1979@rediffmail.com (praveen) wrote:

>>Yes i know about power on
>>ethernet but the power i want to transfer is 60 W

> I'm not sure you can, and still be legal. The ampacity of the wire is
> going to limit your current, the various codes for low-voltage wiring
> are going to limit your voltage, and the intersection of the two is
> going to give you your maximum power (minus line losses). 802.3af
> peaks out at about 20 watts input to the cable (15.4W per device),
> though you might be able to cheat and use all four pairs to double
> your power. The standards are a nightmare to parse, but it might be
> possible. Dunno what standards you have in India, or if this is for
> commercial operation or not. Can you pull another cable?

If it is 15W per pair then he should be able to get close
to 60W with four pair. (If it is limited by cable heating
then it will be a little less.)

I would have tried center tapped transformers before
using inductors to isolate it.

It is supposed to be that three phase AC makes the most
efficient use of its wires, so three phase between three
pairs might do it. That is, if you are limited by average
current squared and peak to peak voltage. It shouldn't
be much harder to keep 60Hz away from ethernet, though
it could run at a higher frequency if you have to generate
it anyway.

-- glen
Anonymous
October 26, 2004 3:46:46 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

glen herrmannsfeldt <gah@ugcs.caltech.edu> wrote:
>William wrote:
>> praveenkumar1979@rediffmail.com (praveen) wrote:
>>>Yes i know about power on
>>>ethernet but the power i want to transfer is 60 W

>> though you might be able to cheat and use all four pairs to double
>> your power.

>If it is 15W per pair then he should be able to get close
>to 60W with four pair. (If it is limited by cable heating
>then it will be a little less.)

It's actually pairs of pairs, so he could double the power. Google
for the PoE spec...
Anonymous
October 26, 2004 6:43:24 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Well, obviously there is no DC in 10BASE-T protocol as DC can carry no
signal. The actual spectrum analysis of a 10BASE-T signal would probably
show max energy at or around 5 to 7 MHz. Even then, I don't see how it
affects your power-over-CAT5 calculations. All you need to worry about is
max current, and not the frequency. You can run 1A of current on every pair
of a AWG24 cable, such as CAT5. Since two pairs are used already for
10BASE-T, you are left with two pairs or 2A, which would make it 30V for the
operating voltage. You will have to add few volts for the voltage drop,
depending on the length of your cable.



--

Dmitri Abaimov, RCDD

http://www.cabling-design.com

Cabling Forum, color codes, pinouts and other useful resources for

premises cabling users and pros

http://www.cabling-design.com/homecabling

Residential Cabling Guide

-------------------------------------

"praveen" <praveenkumar1979@rediffmail.com> wrote in message
news:ff8a3afb.0410250004.3e8be6d1@posting.google.com...
> Hello,
> I am want know the frequency of the ethernet data so that i can decide
> on the value of the inductor through which i can feed DC power.
> I have heard the ethernet can range from DC to 10 Mhz (10TBase), in
> this case i cannot feed power on ethernet. Yes i know about power on
> ethernet but the power i want to transfer is 60 W, so i feed the power
> directly to the line
>
> I need what is value of the inductor i have to choose.
>
> Waiting for reply
> Regards
> Praveen
>
Anonymous
November 7, 2004 6:43:55 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

praveen wrote:

> Hello,
> I am want know the frequency of the ethernet data so that i can decide
> on the value of the inductor through which i can feed DC power.
> I have heard the ethernet can range from DC to 10 Mhz (10TBase), in
> this case i cannot feed power on ethernet. Yes i know about power on
> ethernet but the power i want to transfer is 60 W, so i feed the power
> directly to the line
>
> I need what is value of the inductor i have to choose.

The frequencies used by 10baseT is about 10 - 20 MHz. However, you should
look at the PoE gear. Some of it may be suitable for what you need. My
biggest concern, is that you don't exceed the current capability of the
wire.
Anonymous
November 7, 2004 6:48:43 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Walter Roberson wrote:

> I don't know about DC, and I don't recall the details about 10BaseT,
> but at the higher bit rates, the frequency is not just
> 1/(megabits per second): instead, they use a slower carrier and
> more bits per symbol. Some error correction is used, so the raw
> number of data points sampled exceeds the nominal bandwidth.
>

10baseT, uses Manchester encoding, which means the frequencies used will
range between between 10 & 20 MHz.

> 10/100/1000 BaseT are all async, so when there is no data going through,
> there are no pulses on the line. I never looked deeply enough to
> find out whether it uses a DC carrier or if the line floats free.
>

???

I think you'll find there's always some signalling on 100baseT and faster.
No DC though.
Anonymous
November 7, 2004 6:50:11 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Robert Redelmeier wrote:

> I think inductors would soak up too much of the signal.
>

They'd isolate the DC circuit from the data. A properly selected inductor
will have a high impedance, at the desired frequencies.
Anonymous
November 7, 2004 11:51:17 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <kOidne9-d8GxFxPcRVn-hQ@rogers.com>,
James Knott <james.knott@rogers.com> wrote:

>
> 10baseT, uses Manchester encoding, which means the frequencies used will
> range between between 10 & 20 MHz.
>

Actually, for 10 Mb/s Ethernet (using Manchester encoding) the
fundamental frequency will be between 5 MHz (alternating ones/zeros) and
10 MHz (all ones/all zeros). The energy spectrum of a packetized
Ethernet signal using Manchester encoding at 10 Mb/s is concentrated
under 30 MHz, with signal energy down to (but not including) DC.


--
Rich Seifert Networks and Communications Consulting
21885 Bear Creek Way
(408) 395-5700 Los Gatos, CA 95033
(408) 228-0803 FAX

Send replies to: usenet at richseifert dot com
Anonymous
November 8, 2004 11:24:50 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Rich Seifert wrote:
> In article <kOidne9-d8GxFxPcRVn-hQ@rogers.com>,
> James Knott <james.knott@rogers.com> wrote:

>>10baseT, uses Manchester encoding, which means the frequencies
>>used will range between between 10 & 20 MHz.

> Actually, for 10 Mb/s Ethernet (using Manchester encoding) the
> fundamental frequency will be between 5 MHz (alternating ones/zeros) and
> 10 MHz (all ones/all zeros). The energy spectrum of a packetized
> Ethernet signal using Manchester encoding at 10 Mb/s is concentrated
> under 30 MHz, with signal energy down to (but not including) DC.

And including DC for coaxial ethernet. For 10baseT, though,
the energy should be pretty low at lower frequencies. They
still have to get through the transformer.

I still didn't get around to testing 10baseT with a common
mode 240V AC 60Hz voltage. (I will be sure to test it on
cheap parts, just in case.) If it works, I will believe it
will work with just about everything else that has been suggested
here before.

-- glen
Anonymous
November 8, 2004 1:19:33 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Rich Seifert wrote:

> Actually, for 10 Mb/s Ethernet (using Manchester encoding) the
> fundamental frequency will be between 5 MHz (alternating ones/zeros) and
> 10 MHz (all ones/all zeros). The energy spectrum of a packetized
> Ethernet signal using Manchester encoding at 10 Mb/s is concentrated
> under 30 MHz, with signal energy down to (but not including) DC.
>
>

I realized my error after posting. I had used info that I'd found in the
O'Reilly Ethernet book, by Charles Spurgeon. On page 118, it says "While
Manchester encoding makes it easy for a receiver to synchronize with the
incoming signal and to extract data from it, a drawback of the scheme is
that the worst-case signaling rate is twice the data rate. In other words,
a 10 Mbps stream of all ones or all zeroes results in a Manchester encoded
signaling rate of 20 MHz on the cable.". He was correct in the first
sentence, but wrong in the 2nd, where he confuses signaling rate with
frequency. I have worked with other systems that used Manchester encoding,
but that was almost 30 years ago.
!