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Topic: POE mod for tp-link wr703n

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Here is how I plan to make mod for my wr703n:

wr703 poe mod

Just connect RJ45 pins 4,5 to usb pin 1 (positive) and RJ45 pins 7,8 to usb pin 5 (ground).

Thats it wink

I'll post images after this is done.

Yes, you need to unsolder R65 and R68!

Yes it does, I'll document that tomorrow and post pre and post images to wiki. Also there needs to an additional diode so if router is powered via usb that voltage doesn't go into RJ45 and to your PC or laptop...

(Last edited by valentt on 2 Apr 2013, 01:52)

Hate to grave rob, but poe is 48 volts right?

I dont believe the voltage converter can handle that...

I wouldn't advise this.

poe voltage depends on what power adaptor you use xD

you're right that the most used is (was??) 802.3af that is 48V but that's not a rule...

If you put more that 5V on WR703n you will fry it!!! Don't do it with 48V!!! WR703N doens't have input power regulator, and it expect 5V, anything more than 5.5V will fry it. You have been warned.

POE with 5V won't work on distances >5meters. Tested myself last year, I had to use 32V and a step-down module on the end

(Last edited by dabyd64 on 9 May 2014, 23:19)

dabyd64 wrote:

POE with 5V won't work on distances >5meters. Tested myself last year, I had to use 32V and a step-down module on the end

You don't have to use 32V. It also varies based on cable quality, device power draw and adapter configuration. You can have working passive PoE at 5v over good quality cables of 10m and 15m. At 50m 12v with 5v step down works fine, which'll be easier to do than 32v.

My router was at 20meters, the cable was not the best lol and I had to power a USB hard disk connected to the router, the power at 5 or 12V was not enough and caused random freezes or reboots.
The next power adapter I had was 32V (from an old printer), so I used it. And it worked wink
I used a PTN78020W from Texas instrument (Got it from free samples):
http://media.digikey.com/Photos/Texas%20Instr%20Photos/PTN7-DIP%20SERIES.JPG

It accepts up to 36V and can output up to 6amps. Nice and ultra tiny size!

(Last edited by dabyd64 on 23 May 2014, 02:31)

As I say it depends heavily on the setup, resistance over longer distances determines the maximum wattage that can be delivered at a given voltage. A highly efficient router that takes 2-3 watts will work over a cable of roughly four times the length of average routers that take 8-12w. Of course if you add a USB drive then the power requirements increase further, another 2-5w for a laptop drive and 5-20w for a 3.5" drive. Compared to my 3w router for example your maximum cable length could be reduced by a factor of ten. That's the main reason "true" PoE (802.3af) uses over 40 volts - so that it can reliably power any properly rated device over any properly rated cable of up to 100m.

Though on a side note, higher voltages are more efficient - less power is lost to the cable itself - though you have to account for losses in your downconverter.

(Last edited by qasdfdsaq on 23 May 2014, 04:53)

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