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uk.comp.home-networking (UK home networking) (uk.comp.home-networking) Discussion of all aspects of computer networking in the home, regardless of the platforms, software, topologies and protocols used. Examples of topics include recommendations for hardware or suppliers (e.g. NICs and cabling), protocols, servers, and specific network software. Advertising is not allowed.

Testing Power over Ethernet?



 
 
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  #1  
Old April 23rd 14, 07:51 PM posted to uk.comp.home-networking
Henry Law
external usenet poster
 
Posts: 46
Default Testing Power over Ethernet?

[Apologies; I meant to post this here originally and posted by mistake
to u.c.homebuilt, so this is a duplicate post and not cross-posted. I
undertake to do penance in front of the Internet gods ...]

The charity for which I am, it seems, IT manager, network technician, PC
builder and fixer, chief cook and bottle washer has a wireless access
point high up on a wall and powered by PoE. I managed to get a look at
it earlier today: no lights! That might explain why wireless doesn't
work too well.

It's possible that it's patched wrongly and that the Power is
disappearing Over some other Ethernet but assuming not how do I test it?
I can hardly bung my trusty meter across the terminals ...

It's a separate PoE injector, not a PoE switch. The injector is a
little box with a power plug, and two RJ45s, one input and the other output.

I googled but all the hits are for professionals who can afford
sophisticated test kit. I don't even have some other PoE-powered device
to use as "known good".

--

Henry Law Manchester, England
  #2  
Old April 24th 14, 03:48 AM posted to uk.comp.home-networking
GlowingBlueMist
external usenet poster
 
Posts: 6
Default Testing Power over Ethernet?



On 4/23/2014 12:51 PM, Henry Law wrote:
[Apologies; I meant to post this here originally and posted by mistake
to u.c.homebuilt, so this is a duplicate post and not cross-posted. I
undertake to do penance in front of the Internet gods ...]

The charity for which I am, it seems, IT manager, network technician, PC
builder and fixer, chief cook and bottle washer has a wireless access
point high up on a wall and powered by PoE. I managed to get a look at
it earlier today: no lights! That might explain why wireless doesn't
work too well.

It's possible that it's patched wrongly and that the Power is
disappearing Over some other Ethernet but assuming not how do I test it?
I can hardly bung my trusty meter across the terminals ...

It's a separate PoE injector, not a PoE switch. The injector is a
little box with a power plug, and two RJ45s, one input and the other
output.

I googled but all the hits are for professionals who can afford
sophisticated test kit. I don't even have some other PoE-powered device
to use as "known good".

If you can, purchase one of these cheap Ethernet testing kits.
You will find it really pays for itself when you suspect wiring
problems, even with store bought cables. Sorry about the long URL but I
don't use those URL shortening sites for security reasons. You might
find the tester all by itself a little cheaper but at GBP 7.90 plus
shipping it really comes in handy.

http://www.ebay.com/itm/RJ45-Cat5e-N...item35c7271c34

Like you I volunteer at a charity doing IT work. I had to use one of
these testers on an access point high up on a wall in a gymnasium just
last week. As we thought, the cable connectors had been wired
incorrectly, in this case at both ends of the cable. Replaced one end
and then the test pattern showed a different pattern, still bad, so we
replaced the other end of the cable and now the access point is
connected to the network at 1000Mbps rather than the 10Mbps it was
running at.
  #3  
Old April 25th 14, 01:39 PM posted to uk.comp.home-networking
[email protected]
external usenet poster
 
Posts: 83
Default Testing Power over Ethernet?

Henry Law wrote:
The charity for which I am, it seems, IT manager, network technician, PC
builder and fixer, chief cook and bottle washer has a wireless access
point high up on a wall and powered by PoE. I managed to get a look at
it earlier today: no lights! That might explain why wireless doesn't
work too well.

It's possible that it's patched wrongly and that the Power is
disappearing Over some other Ethernet but assuming not how do I test it?
I can hardly bung my trusty meter across the terminals ...

You probably can, it certainly won't do any harm, I'd guess the
regulation (from nominal 12 volts is common) down to 5 volts is in the
'destination' so I'd expect to see 12 volts or so across two of the
ethernet wires.

In fact, unless it's Gigabit aren't there spare pairs?

The Wikipedia areticle at http://en.wikipedia.org/wiki/Power_over_Ethernet
has useful information, though might not be *directly* relevant as the
voltages they talk about for POE are higher than I have on my devices.

This link provides some detail on TP-Link POE:-
http://www.dd-wrt.com/phpBB2/viewtopic.php?p=722310

If you have 'passive' POE then it uses the spare pairs in the ethernet
cable to carry power and thus you can check it simply with your meter.


It's a separate PoE injector, not a PoE switch. The injector is a
little box with a power plug, and two RJ45s, one input and the other output.

That's pretty common, I have three of them, two for outdoor WiFi
access points and one for a router.

--
Chris Green

  #5  
Old April 25th 14, 06:39 PM posted to uk.comp.home-networking
[email protected]
external usenet poster
 
Posts: 83
Default Testing Power over Ethernet?

Rob Morley wrote:
On Fri, 25 Apr 2014 12:39:43 +0100
wrote:

Henry Law wrote:
The charity for which I am, it seems, IT manager, network
technician, PC builder and fixer, chief cook and bottle washer has
a wireless access point high up on a wall and powered by PoE. I
managed to get a look at it earlier today: no lights! That might
explain why wireless doesn't work too well.

It's possible that it's patched wrongly and that the Power is
disappearing Over some other Ethernet but assuming not how do I
test it? I can hardly bung my trusty meter across the terminals ...

You probably can, it certainly won't do any harm, I'd guess the
regulation (from nominal 12 volts is common) down to 5 volts is in the
'destination' so I'd expect to see 12 volts or so across two of the
ethernet wires.

While there are various versions of PoE, the "proper" voltage is around
40V IIRC.

Yes, the Wikipedia article I cited says that, however all of mine are
actually 12 volts.

It depends really whether the OP's system is "proper professional" one
(e.g. Cisco or some such) which goes with the standards and thus is 44
volts or is a "cheapie" (e.g. TP-Link) which is more likely to be 12
volts.

Same applies to both though, if it's passive POE then the voltage is
provided by the 'spare' CAT5 wires so should be relatively easy to
check.

The voltage on all of mine is shown on the POE 'supply' box, the one
with two RJ-45 connectors and a power in connector.

--
Chris Green

  #10  
Old April 28th 14, 02:55 PM posted to uk.comp.home-networking
Henry Law
external usenet poster
 
Posts: 46
Default Testing Power over Ethernet?

On 27/04/14 10:24, wrote:
That sounds as if it should be compatible


Swapped it in this morning, access point has blinking lights and works.
Thanks to all.

--

Henry Law Manchester, England
 




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