A number of Access Point manufacturers are now offering Power over Ethernet add-on's for their Access Points. A PoE module inserts DC voltage into the unused wires in a standard ethernet cable (pairs 7-8 and 4-5). The idea is to supply the AP's power and UTP ethernet connectivity requirements via a single ethernet cable. This works great in areas where you may not have power and/or ethernet easily accessible, like a roof. There are currently two types of PoE adapters: a module jack or hub-like device for multiple access points. The following hack creates a simple PoE module pair.The most tricky part of the hack is selecting the right power supply to adjust for power loss.
That is, DC (like any other voltage or signal) looses it strength with greater distance. Thankfully most AP's can run between 12-16 volts (double check your AP's spec sheet or manual), our module must meet this threshold. Using a standard Cat5 (typically 22 guage wires) cable, 12 volts can travel ~100ft. Jameco sells a number of DC wall transformers. See the plot below for example cable distance to required power.
insert plot of cable distance to voltage WARNING: Don't try this at home, unless you have some electric clue. 12v isn't going to kill you, but you may cause serious damage to your access point and other equipment. Don't blame me if something goes wrong.
![[Surface Mount Image]](surfacemountbox.gif)
I bought two RJ45 "surface modular jacks" ($2.99/each) from Fry's (shame on me, any datacomm or electronics store should carry these). These break-out the each pair individually. You'll also need a spare ethernet cable to cut up. Standard hack tools such as multi-meter, wire cutters, and electrical tape apply.
- Started as a dare from BAWUG member Cliff Skolnick on 2000/10/29.
- Orinoco for giving away the unused pair numbers in the Active Ethernet data sheet.
- 2000/12/11 - First public release.