View Full Version : DIY POE (Power Over Ethernet)
WARNING: Don't try this unless you know what you're doing...
I used a 20 meter ethernet cable, and tried to power the WL500g with +5v using the extra 2 unused pairs in the cable (wires 4,5,7,8).
I did get +5v on the other end, but, the router just lights up and flashes the power button...
btw, I did CUT the wires 4,5,7 and 8, so that the only wires that go into the ethernet plug are 1,2,3 and 6...
I guess the voltage drop is to high... I'll have to figure out a way to make it work..
more info:
http://www.nycwireless.net/poe/
http://www.gweep.net/~sfoskett/tech/poecalc.html
Hi
The NYC Wireless Method is quite good, and may work if used with equipment powered by 12V, but at 5V the drop is likely too high to get the switching sircuit in the Router to work well.
I think you should put 12V into the Cable and use a secound 5V regulator direkt in front of the Router. Hmm, a usual 7805 Regulator will not be powerfull enough i think (1,5A maximum), you habe to design something youself, grab it from the internet or use a readymade module from radioshack, conrad or so :)
I would be interrested in the results of your work.
Greets
Antiloop
01-06-2005, 16:04
and what about when using a PoE adapter (thus 48v) ?
and what about when using a PoE adapter (thus 48v) ?
Electrically that would mean a much lower current (considering the same power is required) and therefore a lower voltage drop over the 20m line. But on the receiving end (the router) that would mean you have transform the 48V back to 5V (or whatever the input voltage should be).
Transforming the 48V (or 12V) back to 5V using a 7505 would produce quite a lot of heat because the 7505 voltage regulator is quite simple and the voltage difference is dissipated as heat. Therefore a 7505 would be unusable IMHO when the voltage difference is greater then 5V, especially when requiring 2A@5V. Using a switching circuit to transform the voltage back would be a better idea, but swiching regulators are quite expensive.
For me the question is: How do other manufacturers handle this?
Antiloop
01-06-2005, 20:49
Electrically that would mean a much lower current (considering the same power is required) and therefore a lower voltage drop over the 20m line. But on the receiving end (the router) that would mean you have transform the 48V back to 5V (or whatever the input voltage should be).
Transforming the 48V (or 12V) back to 5V using a 7505 would produce quite a lot of heat because the 7505 voltage regulator is quite simple and the voltage difference is dissipated as heat. Therefore a 7505 would be unusable IMHO when the voltage difference is greater then 5V, especially when requiring 2A@5V. Using a switching circuit to transform the voltage back would be a better idea, but swiching regulators are quite expensive.
For me the question is: How do other manufacturers handle this?
well it seems that the WL300g does support this, as it should be 802.3af compatible according to specs
seems to be handled internally, also power is only 48V DC and 400mA
specs i think :)
http://www.chupa.nl/ieee/802.3af-2003.pdf