Re: Linksys WET11 Power over Ethernet

That's a lot of good information about PoE!

It's important for people to know that sending any voltage higher than 5
volts to most access points without a regulator is asking for trouble. SOME
access points have a built-in regulator and some even have a built-in PoE
power picker, but most do not.

The best way to get power over Ethernet is to use about 48 volts on the
ethernet and put a good switching DC to DC voltage converter at the access
point to regulate the voltage to 5 volts. A good example of such a
regulator is the LM2576-HVS-5.0. This regulator requires a few external
components, so it may be beyond the capability of some to set it up
properly. A very simple, inexpensive regulator is available from Electronic
Goldmine here:
http://sales.goldmine-elec.com/prodinfo.asp?prodid=6377

This DC to DC converter is WAY OVERKILL, but it's less than $10 and very
simple to use. Just add a couple of sense wires and ground the enable input
and you're in business. It's a 300 Watt converter, but you shouldn't try to
send more than about 20 Watts over PoE. That's not a problem as long as the
load you connect is just an access point. This converter will need about 40
to 70 volts. Try to keep it at 48 volts.

Here is the reference info for the converter if you want to try it:
http://www.astec.com/reference/TRN/bm80.pdf

You won't find an easier to use DC to DC converter for PoE and the price is
a giveaway! Electronic Goldmine also has a great deal on a dual RJ45 for
the picker and injector (4 for $1.00!):
http://sales.goldmine-elec.com/prodinfo.asp?prodid=5764

Don W.


"radiotech" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> I'm starting to see a patern at wireless internet site installs using the
> Linksys WET11
> Using a method for power over ethernet devised on the LM7805 voltage
> regulator
> Linksys has a builtin 7805 (or similar) on some installs the wet11's
> internal regulator is fine
> on some installs the only way I could get the unit to work was by
installing
> an inline 2nd
> regulator usually with a large heatsink, or guess the voltage.....lol ex.:
> 7.5vdc
> Linksys ships with a 5.5vdc for runs 300'+ I use 12vdc1amp and reduce it
> with 2nd 7805
> for runs under 25-50 foot I just use the stock 5.5 powersupply
> for runs around 50-300 I usually could just use the 12vdc supply and
> internal regulator
> Well......popped one yesturday....lol Was there a design change? cheaper
> regulator?
> I know, I know Im really doing something with this unit Im not suppose
> to...... They always say "you cant do that"\
> Well I tried 5.5 not enough !!! I figure voltage drop at about 1.5volts
per
> 100 foot
> Results: -> (AP is about 4 miles away with 24DBi Grid Dish, PoE is about
> 125')
>
> 5.5 vdc --- Can see ap but cannot connect or DHCP --- Theory -- Receive
> doesnt need as much power
> and works but Transmitter is too low therefore cannot establish link -->
> Signal 85% Link 0%
> 7.5 vdc (no regulator) Everthing works great !!!! This is what stayed
> with....
> 10 vdc - no pop but could not access unit on network - no html - no
linksys
> setup
> 12 vdc POP! smoked the wett11 - lets not try that twice
>
> The funny thing is the unit was working at 12vdc I changed unit after
> rebulid job
> from hurricane damage were it jerked mast,ant, and coax off the house
> damaged the ant connector. never had problem with power
>
> Well in the past I could not access certain wett11's with html but could
> with linksys software
> they too were power over ethernet....
> Theory Im thinking:
> ] Between certain voltages only will the html communications work - Ideal
> ] Under voltage everything looks fine but, hehe theres always a but with
> wireless, u cannot establish link
> ] Over voltage and well you know POP - or - unit works fine just cant talk
> to it with html interface (overclocking...lol)
>
> worse case - 12vdc tried this at 1000' of cat5 - at wet11 end - LM7805
5vdc
> regulator attached to heatsink - power into wet11
> anyway take it for what its worth just thought I would share fried
equipment
> results with yall .... LOL
> (E-Mail Removed)
>
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