| Author |
Message |
William P. N. Smith
Guest
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 Posted:
Sun Aug 21, 2005 6:07 am Post subject:
Linksys Lies! WAPPOE(12) isn't 802.3af !! |
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I got a couple of sets of the Linksys WAPPOE12 Power-Over-Ethernet
boxes for putting WiFi APs in distant places without needing AC power
nearby, and checked very carefully to ensure that they were 802.3af
PoE, as I didn't want one of the non-compliant PoE kludges, so I could
be sure that everything was compatable, and safe to use with old and
new equipment.
OOPS! I pulled the covers off the 'injector', the piece that connects
the 48V to the spare pairs _only_ when the client device is determined
to have PoE capabilities, and found
http://compusmiths.com/WAPPoeBARsm.jpg
Not a single semiconductor (well, except the power LED), switch,
current limiter, or anything. Just slap the 48V right across the
spare pairs and hope nothing blows up. The WAPPOE injector is the
same, with the exception of a blue plastic case.
Well, I guess I know why it was so cheap. Sigh. I dunno if I even
dare try to see if the splitter will work on 802.3af switches, which
supply phantom power over the data pairs...
Grrrr.... The vendor doesn't want returns, hopefully Linksys will be
open to a refund. |
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Jeff Liebermann
Guest
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| Posted:
Sun Aug 21, 2005 6:36 am Post subject:
Re: Linksys Lies! WAPPOE(12) isn't 802.3af !! |
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On Sat, 20 Aug 2005 21:07:30 -0400, William P. N. Smith <> wrote:
| Quote: | I got a couple of sets of the Linksys WAPPOE12 Power-Over-Ethernet
boxes for putting WiFi APs in distant places without needing AC power
nearby, and checked very carefully to ensure that they were 802.3af
PoE, as I didn't want one of the non-compliant PoE kludges, so I could
be sure that everything was compatable, and safe to use with old and
new equipment.
|
http://www1.linksys.com/products/product.asp?grid=33&scid=38&prid=680
If you look at the spec sheet that's inconveniently buried in Appendix
B of the installation instructions, it claims to be IEEE 802.3,
802.3u, and 802.3af compliant.
ftp://ftp.linksys.com/pdf/WAPPOE12-UG-Rev_NC%20web.pdf
I don't think so.... Incidentally, did you notice that the new and
improved Linksys web mess no longer includes data sheets on the
product pages? I wonder what other suprises they're hiding?
Incidentally, did you read my tests of the BEFW11S4 and WRT54G routers
running off anything from about 4.0VDC to 18VDC directly?
| Quote: | OOPS! I pulled the covers off the 'injector', the piece that connects
the 48V to the spare pairs _only_ when the client device is determined
to have PoE capabilities, and found
http://compusmiths.com/WAPPoeBARsm.jpg
Not a single semiconductor (well, except the power LED), switch,
current limiter, or anything. Just slap the 48V right across the
spare pairs and hope nothing blows up. The WAPPOE injector is the
same, with the exception of a blue plastic case.
|
Chuckle. Notice the four resistors in the upper photograph labelled
R2, R3, R4, and R5. Could I trouble you to supply the resitor values?
These will limit the current supplied. I'm curious to calculate what
the 12V maximum load might be. There's nothing in the spec sheet and
I'm guessing that they've exceeded the DC current limit for the RJ45
connectors.
| Quote: | Well, I guess I know why it was so cheap. Sigh. I dunno if I even
dare try to see if the splitter will work on 802.3af switches, which
supply phantom power over the data pairs...
|
It won't. There has to be a compatible PoE chip on the injector for
it to work.
| Quote: | Grrrr.... The vendor doesn't want returns, hopefully Linksys will be
open to a refund.
|
Nice work. Thanks for the clue. Post it to the Linksys support forum
on DSLReports. It might get their attention.
--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
AE6KS 831-336-2558 |
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William P. N. Smith
Guest
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| Posted:
Sun Aug 21, 2005 8:15 am Post subject:
Re: Linksys Lies! WAPPOE(12) isn't 802.3af !! |
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Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:
| Quote: | If you look at the spec sheet that's inconveniently buried in Appendix
B of the installation instructions, it claims to be IEEE 802.3,
802.3u, and 802.3af compliant.
|
Yeah, they lie.
| Quote: | Incidentally, did you read my tests of the BEFW11S4 and WRT54G routers
running off anything from about 4.0VDC to 18VDC directly?
|
Yes, I'm characterizing the WAP54G, looks like it'll do 4.20 to over
18.86V (as high as this supply will go). More news as it happens,
plus graphs and such.
| Quote: | Chuckle. Notice the four resistors in the upper photograph labelled
R2, R3, R4, and R5. Could I trouble you to supply the resitor values?
|
Those are 12 ohms, in series with the Ethernet input. Maybe some kind
of matching for the input? Wierd...
| Quote: | These will limit the current supplied. I'm curious to calculate what
the 12V maximum load might be. There's nothing in the spec sheet and
I'm guessing that they've exceeded the DC current limit for the RJ45
connectors.
|
On further inspection, there's a self-resetting fuse at SI1, with
"R110 4289S" marked on it. Note that they are feeding in 48V, and
using the "Power Splitter" at the other end to convert down to {12,5}V
for the device they are driving.
My programmable load is down, so I can't characterize the 12V output,
but since the WAP54G only draws about 3W (and the 802.3af PoE spec is
somewhere around 15W), I'm sure they aren't stressing anything. In
fact, at 48V, it's only drawing about 7mA (plus or minus the
inefficiency of the switching supply in the splitter).
The whole point of this exercise was to have less power (heat) at the
AP, but AFAICT the splitter dissipates more power than the AP, so I
suspect I'll go back to using a spare cable or pair to power the AP... |
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David Taylor
Guest
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| Posted:
Sun Aug 21, 2005 8:20 am Post subject:
Re: Linksys Lies! WAPPOE(12) isn't 802.3af !! |
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| Quote: | OOPS! I pulled the covers off the 'injector', the piece that connects
the 48V to the spare pairs _only_ when the client device is determined
|
Ignore comment about 12V, brain just engaged, it's not quite 8am. :)
David. |
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Jeff Liebermann
Guest
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| Posted:
Sun Aug 21, 2005 8:20 am Post subject:
Re: Linksys Lies! WAPPOE(12) isn't 802.3af !! |
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On Sat, 20 Aug 2005 23:15:05 -0400, William P. N. Smith <> wrote:
| Quote: | Incidentally, did you read my tests of the BEFW11S4 and WRT54G routers
running off anything from about 4.0VDC to 18VDC directly?
Yes, I'm characterizing the WAP54G, looks like it'll do 4.20 to over
18.86V (as high as this supply will go). More news as it happens,
plus graphs and such.
|
Methinks the WAP54G uses the same LM2941 LDO regulator as the WRT54G.
The radio runs on 3.3VDC. The regulator needs about 0.5VDC. You
should be able to run it down to about 4.0VDC.
| Quote: | http://cache.national.com/ds/LM/LM2941.pdf
|
My BEFW11S4v4 running on 3.8VDC:
| Quote: | http://802.11junk.com/jeffl/pics/drivel/slides/low-volt.html
Just ignore the mess. |
| Quote: | Chuckle. Notice the four resistors in the upper photograph labelled
R2, R3, R4, and R5. Could I trouble you to supply the resitor values?
Those are 12 ohms, in series with the Ethernet input. Maybe some kind
of matching for the input? Wierd...
|
Nope. Short circuit protection. Maximum short circuit current is:
48VDC / 24 ohms = 1A
That's divided between two pairs of contacts so the maximum connector
current is 0.5A. That's slightly under the rating for the connector
so the RJ45 connectors should be ok.
CAT5 is 3 ohms per 100ft per conductor. 300ft of CAT5 using 2 pairs
of wires for power is equal to 9 ohms of loop resistance. Adding the
9 ohms to the series resistors yields 21 ohms of total loop resistance
(assuming there's no additional resistance in the terminating end of
the PoE).
The WRT54G sucks about 0.3A at 13.6VDC input. I'll assume there's a 3
terminal regulator inside the terminating end of the PoE thing. It
would need about 15VDC on the input, at 0.3A to run a WRT54G.
Grinding the numbers:
Copper voltage drop = (0.3A * 21 ohms) = 6.3 VDC
Max voltage drop allowed = 48 - 15 = 33VDC
So, this should work just fine.
Assuming 0.3A per access point, this contraption should run:
(48 - 15) / 21ohms / 0.3A per AP = 5.2
which means that it could power 5 access points for a total of about
1.5A current drain.
| Quote: | On further inspection, there's a self-resetting fuse at SI1, with
"R110 4289S" marked on it. Note that they are feeding in 48V, and
using the "Power Splitter" at the other end to convert down to {12,5}V
for the device they are driving.
My programmable load is down, so I can't characterize the 12V output,
but since the WAP54G only draws about 3W (and the 802.3af PoE spec is
somewhere around 15W),
|
Well, the real 802.3af spec calls for 5ea different weird
"classifications" of load. I won't pretend to undestand why this is
necessary.
CLASSIFICATION:
CLASS PD POWER(W) R(CLASS)ohms 802.3af LIMITS(mA) NOTE
0 0.44 - 12.95 4420 ±1% 0 - 4 Default class
1 0.44 - 3.84 953 ±1% 9 - 12
2 3.84 - 6.49 549 ±1% 17 - 20
3 6.49 - 12.95 357 ±1% 26 - 30
4 - 255 ±1% 36 - 44 Reserved
| Quote: | I'm sure they aren't stressing anything. In
fact, at 48V, it's only drawing about 7mA (plus or minus the
inefficiency of the switching supply in the splitter).
|
48VDC * 7ma = 3.4 watts. Yeah, that's about right.
| Quote: | The whole point of this exercise was to have less power (heat) at the
AP, but AFAICT the splitter dissipates more power than the AP, so I
suspect I'll go back to using a spare cable or pair to power the AP...
|
I used to use DC to DC inverters to run a mess of AP's on top of a
tower. Lots of RFI from the inverters so I had to shielded power
supplies. Then I discovered the wide range of voltages that the
Linksys stuff will run on. I dumped the DC to DC inverter and lived
happily ever after.
--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
AE6KS 831-336-2558 |
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David Taylor
Guest
|
| Posted:
Sun Aug 21, 2005 8:20 am Post subject:
Re: Linksys Lies! WAPPOE(12) isn't 802.3af !! |
|
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| Quote: | OOPS! I pulled the covers off the 'injector', the piece that connects
the 48V to the spare pairs _only_ when the client device is determined
to have PoE capabilities, and found
http://compusmiths.com/WAPPoeBARsm.jpg
|
The label says 12V? |
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stephen
Guest
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| Posted:
Sun Aug 21, 2005 4:20 pm Post subject:
Re: Linksys Lies! WAPPOE(12) isn't 802.3af !! |
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"Jeff Liebermann" <jeffl@comix.santa-cruz.ca.us> wrote in message
news:i2ufg1p97t30d7t44tk0t9h0ncosgkhk76@4ax.com...
| Quote: | On Sat, 20 Aug 2005 23:15:05 -0400, William P. N. Smith <> wrote:
Incidentally, did you read my tests of the BEFW11S4 and WRT54G routers
running off anything from about 4.0VDC to 18VDC directly?
Yes, I'm characterizing the WAP54G, looks like it'll do 4.20 to over
18.86V (as high as this supply will go). More news as it happens,
plus graphs and such.
Methinks the WAP54G uses the same LM2941 LDO regulator as the WRT54G.
The radio runs on 3.3VDC. The regulator needs about 0.5VDC. You
should be able to run it down to about 4.0VDC.
http://cache.national.com/ds/LM/LM2941.pdf
My BEFW11S4v4 running on 3.8VDC:
http://802.11junk.com/jeffl/pics/drivel/slides/low-volt.html
Just ignore the mess.
Chuckle. Notice the four resistors in the upper photograph labelled
R2, R3, R4, and R5. Could I trouble you to supply the resitor values?
Those are 12 ohms, in series with the Ethernet input. Maybe some kind
of matching for the input? Wierd...
Nope. Short circuit protection. Maximum short circuit current is:
48VDC / 24 ohms = 1A
That's divided between two pairs of contacts so the maximum connector
current is 0.5A. That's slightly under the rating for the connector
so the RJ45 connectors should be ok.
CAT5 is 3 ohms per 100ft per conductor. 300ft of CAT5 using 2 pairs
of wires for power is equal to 9 ohms of loop resistance. Adding the
9 ohms to the series resistors yields 21 ohms of total loop resistance
(assuming there's no additional resistance in the terminating end of
the PoE).
The WRT54G sucks about 0.3A at 13.6VDC input. I'll assume there's a 3
terminal regulator inside the terminating end of the PoE thing. It
would need about 15VDC on the input, at 0.3A to run a WRT54G.
Grinding the numbers:
Copper voltage drop = (0.3A * 21 ohms) = 6.3 VDC
Max voltage drop allowed = 48 - 15 = 33VDC
So, this should work just fine.
Assuming 0.3A per access point, this contraption should run:
(48 - 15) / 21ohms / 0.3A per AP = 5.2
which means that it could power 5 access points for a total of about
1.5A current drain.
On further inspection, there's a self-resetting fuse at SI1, with
"R110 4289S" marked on it. Note that they are feeding in 48V, and
using the "Power Splitter" at the other end to convert down to {12,5}V
for the device they are driving.
My programmable load is down, so I can't characterize the 12V output,
but since the WAP54G only draws about 3W (and the 802.3af PoE spec is
somewhere around 15W),
|
15.x watts from the sending switch / injector, 13.y available to the device
(allowing for cable losses)
i dont have the exact numbers to hand here.
| Quote: |
Well, the real 802.3af spec calls for 5ea different weird
"classifications" of load. I won't pretend to undestand why this is
necessary.
|
the power classifications are to allow a switch using 802.3af with a
constrained PSU estimate aggregate load and shed any overload without being
too conservative.
if you work out worst case PoE load on a big chassis switch with 802.3af,
then the number get a bit painful (e.g. a cisco Cat6509 with 8 *96 port
10/100 blades works out at around 11.5 kWatts for PoE + power overheads +
the switch itself).
power sensing lets you only supply PoE active devices - but a lot of end
points dont need anything like 13W, and not many offices are already wired
for these kinds of power levels in a wiring closet.
| Quote: |
CLASSIFICATION:
CLASS PD POWER(W) R(CLASS)ohms 802.3af LIMITS(mA) NOTE
0 0.44 - 12.95 4420 ±1% 0 - 4 Default class
1 0.44 - 3.84 953 ±1% 9 - 12
2 3.84 - 6.49 549 ±1% 17 - 20
3 6.49 - 12.95 357 ±1% 26 - 30
4 - 255 ±1% 36 - 44 Reserved
class 0 is what you get if the device / switch or both dont understand the |
classify scheme.
the others are about the various expected ranges of load - for example some
Voip phones may report class 1 or 2.
some manufacturers make a big thing about finer grained power notifies using
non standard schemes - Cisco for one.
| Quote: | I'm sure they aren't stressing anything. In
fact, at 48V, it's only drawing about 7mA (plus or minus the
inefficiency of the switching supply in the splitter).
48VDC * 7ma = 3.4 watts. Yeah, that's about right.
The whole point of this exercise was to have less power (heat) at the
AP, but AFAICT the splitter dissipates more power than the AP, so I
suspect I'll go back to using a spare cable or pair to power the AP...
I used to use DC to DC inverters to run a mess of AP's on top of a
tower. Lots of RFI from the inverters so I had to shielded power
supplies. Then I discovered the wide range of voltages that the
Linksys stuff will run on. I dumped the DC to DC inverter and lived
happily ever after.
--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
AE6KS 831-336-2558
-- |
Regards
Stephen Hope - return address needs fewer xxs |
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William P. N. Smith
Guest
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| Posted:
Mon Aug 22, 2005 12:20 am Post subject:
Re: Linksys Lies! WAPPOE(12) isn't 802.3af !! |
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Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:
| Quote: | The WRT54G sucks about 0.3A at 13.6VDC input. I'll assume there's a 3
terminal regulator inside the terminating end of the PoE thing.
|
5-terminal, LM2576 HVS-ADJ "Simple Switcher", plus choke, diode, and
some caps. I can only imagine the WAPPOE and the WAPPOE12 have the
same design with a couple resistors to change the output voltage. |
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William P. N. Smith
Guest
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| Posted:
Mon Aug 22, 2005 12:20 am Post subject:
Re: Linksys Lies! WAPPOE(12) isn't 802.3af !! |
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Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:
| Quote: | William P. N. Smith <> wrote:
Those are 12 ohms, in series with the Ethernet input. Maybe some kind
of matching for the input? Wierd...
Nope. Short circuit protection. Maximum short circuit current is:
48VDC / 24 ohms = 1A
|
Those aren't in the power supply circuit, but in the Ethernet circuit.
Since these are doing "Midspan" power injection, they are leaving the
Ethernet pairs alone and applying 48V on the 'spare' pairs. |
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William P. N. Smith
Guest
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| Posted:
Mon Aug 22, 2005 12:20 am Post subject:
Re: Linksys Lies! WAPPOE(12) isn't 802.3af !! |
|
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Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:
| Quote: | I used to use DC to DC inverters to run a mess of AP's on top of a
tower. Lots of RFI from the inverters so I had to shielded power
supplies. Then I discovered the wide range of voltages that the
Linksys stuff will run on. I dumped the DC to DC inverter and lived
happily ever after.
|
Anyone make a CAT5 splitter to allow power over the spare pairs, or am
I going to have to make my own? Linksys almost does (a couple of
their WAPPOE "power injectors" back to back), but that's kinda pricey.
8*} |
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William P. N. Smith
Guest
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| Posted:
Tue Aug 23, 2005 12:20 am Post subject:
Re: Linksys Lies! WAPPOE(12) isn't 802.3af !! |
|
|
William P. N. Smith <> wrote:
| Quote: | The whole point of this exercise was to have less power (heat) at the
AP, but AFAICT the splitter dissipates more power than the AP, so I
suspect I'll go back to using a spare cable or pair to power the AP...
|
Not quite true, just characterised the "splitter". The power supply
is a regulated 48V supply, and the splitter draws 9.42mA DC with no
load, or about 0.45 watts.
When connected to the WAP54G V.2, which is a 3W load, the whole
assembly draws 95.0 mA, or about 4.56 watts. At this load, the
switcher in the splitter is about 66% efficient.
Still, not much point to having a power supply feeding some random
voltage to a device that'll accept something like 5-25VDC, so I'm
going back to splitting the cable between 10/100BaseT Ethernet and DC
power on the spare pairs for these particular devices. |
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