PoE is somthing fairly common in many business/office spaces. For example, many wireless access points in office buildings and universities use the technology so they don't have to run a power receptacle to wireless access points. For this instructable though, we're going to use PoE in a residential setting. Even the big router companies are starting to sell these adaptors to consumers like this Linksys WAPPOE12. But I think it costs way too much and is kinda bulky. If you're into the DIY bulky thing though/have a need for an external PoE injector, you could try this option.
Applications for this instructable are up to your imagination. You might be relocating your wireless router to the centre of a house for better reception even though the cable modem installer might have put the cable modem say in the basement/some other inconvenient spot. Another useful application might just be to make an all weather-sealed outdoor access point with the famous WRT54G router inside it.
In my case, I will be using a 5 year-old WIRED router that I had lying around. Have no fear though, the points where we will be soldering are identical on every router/switch that you can get today. I should note that we're using cat5 here. If all you have is cat6, you can still go ahead and use that. But I should note, if you're connecting to a gigabit ethernet device, this instructable won't work. Luckilly, cable modems don't work at GigE speeds and I doubt the WAN port on your router supports GigE.
To begin we'll need some basic things:
1. A router
2. A length of cat5 cable (length depending on your location...mine was 10 ft.)
3. RJ-45 connector ends (...ok 8P8C for you technical people)
4. RJ-45 cable booties
5. A wall wart (power supply brick)
6. Some heat shrink tubing (I just used some random scraps I had lying around)
7. Your trusty soldering iron and some solder
Step 1: Open It Up!
Next, we'll open up the router. Be careful though before you, start prying off the plastic casing and it snaps. There's usually a screw hidden under the label with the serial number, etc... on the bottom of the unit. It's the indicator for the manufacturer to see if you've voided your warranty. Oh, and by the way, this instructable\ will definitely void your warranty. Something I take no responsability for.
Step 2: Bypass the DC Power Input
In my case, I wasn't sure if I'd want to use my router as an actual router or simply as a switch. With that in mind, I decided to make the first port on the router's built-in switch the "injector port." If you were connecting your wireless router to a cable modem you'd just connect it to the port labeled WAN/Internet instead. The process is the exact same as the one I'm following though, just the port is in a different spot. Cycle through the pictures and you'll see the modified instructions for using the WAN port instead of the first port on the switch.
Regardless of what port you chose to use, you must solder pins 4 and 5 to the red (or POSITIVE) lead. Then you solder pins 7 and 8 to the black (or NEGATIVE) lead. Be careful though, ensuring that you don't get sloppy with your soldering and say, link pins 6, 7, 8 together. It can be a little difficult soldering areas that are so close and so small.
The next part is a little hard to explain just in words so definitely check out the pictures. In the bottom of the first picture, you'll see the DC power input area. Normally, the barrel connector from your power brick would connect here to the router. We're going to eliminate the need for that barrel connector port here though. In this particular example, the barrel connector port is facing DOWN. This matters quite a bit. Many of you might be soldering with it point up. Don't want to mix the polarities up at all.
Mouse-over the pics to see what pins need to be soldered where and definitely zoom in.
In my case,
Step 3: Make the Power Adapter End
1. Measure out about 15 feet of cat5 cable. I say 15 feet as a guideline...some believe anything over 15 with this technique is dangerous. However it's debatable. The above linked wikipedia article makes references to this, but before you solder (anything) measure the resistance of your length of cable in step 3 of this list.
2. Use a cat5 cable stripper (come free with many jacks) or an Xacto knife to gently score the sheathing of the cat5 cable 3-4 feet before the cable ends. This is the end that will connect your DC power supply to the computer's power bar and the ethernet port on the computers network interface card/motherboard. Be careful when stripping though, you don't want to nick any of the twisted pairs inside the cable sheathing.
3. Pull the last 3-4 feet up to give you 3 inches of cable exposed. Now we can see the twisted pairs. Cut the blue and brown pairs out as illustrated. Strip the 4 pairs of their sheathing and then twist brown and brown-white together and push off to the side. Then twist the blue and blue-white pairs together. If you want to see the resitance of your cable, connector your multimeter's teast leads to one of the twisted pairs and check on the short end of the cable.
4. Before you break out the soldering iron, prepare the DC injector end by cutting the cable in half (or any other length you prefer...longer might be better if the power bar is say, on your desk). Then strip off the plastic about half an inch or so on both ends. Pull the two wires apart for about a 3 inches and then slip about 1.5 inches of shrink tubing down both ends.
4. However, before we solder anything make sure you have the right polarities figured out. The twisted together blue/blue-white wires get soldered to the positive wire. In our case, this is marked with some writing on it by the manufacturer. Simply twist the two together and solder. Then repeat the process, twisting together the brown/brown-white wires with the negative wire on the connector.
5. We're almost done here. Now, just slip the shrink wrap over the wires you just soldered and use a heat gun or torch to shrink. TIP: I couldn't find my heat gun...so I just moved the soldering iron down the tubing leaving half an inch or so of space between the tubing and iron. Next, slide up the wider piece of shrink tubing (in my case it's white) up to cover those shrunk connections. I'm usually quite thorough with this step of the process -- you don't want anything making contact and shorting out.
6. Last, we'll slip on some cable booties and terminate the ends on this injector cable.