DC Power Over Ethernet (Injector Adapter) For: Router, AP, Switch, Hub




I created this adapter so that I could use a UPS (battery backup) located upstairs, to power a network switch located downstairs. The network switch provides a network/internet connection to my Xbox360, Modded original Xbox, and goes through the basement to a joining house. This solution keeps all of the network equipment powered up, in case I lose power.

This can also be used to power a router, switch, access point or hub that is located in a area that does not have power. For example, you may want to use this method to relocate a WiFi access point to the attic or in a drop ceiling at the office.

The Commercial Linksys POE power injector adapters go for around $40. Power injector adapter

I had the materials on hand which is what prompted me to do this project. You should be able to pick up the materials for under $8...given that you already have a spare Ethernet cable lying around.

Materials needed:
2 - RJ45 Ethernet (cat5) wall plate jacks.
1 - RJ45 Ethernet (cat5) patch cable.

Step 1: What Wires Are Actually Used for Data?

A ethernet (cat5) cable has 8 wires. 4 of the wires are used to transmit and recieve data. The other 4 are not used. The "unused" wires will carry the power from the AC adapter.

Step 2: Striping the Ethernet Cable and Sorting the Wires.

Cut the Ethernet (cat5) cable and strip the outer insulation from the cut end, about 1 inch should be enough. You will see 4 groups of wires that are bundled in 2's. Separate the wires. You are only going to use the Green, Green/White and Orange, Orange/White. The other wires can be cut away. Do the same to the other piece of cable.

Step 3: Cutting and Striping the AC Adapter Wires.

Find the middle of the AC adapter cord and cut it. Separate the wires by splitting them apart about 1 inch. Strip the ends of the wires about an 1/8 of an inch. These wires will be pushed onto the RJ45 jack. You will only need to expose a small bit of the wire to make contact on the ethernet jack. Do the same to the other cut piece of the AC adapter.

Step 4: Match the Colors to the Ethernet Jack.

Take the striped end of the ethernet cable and punch each wire into slot 1,2,3 and 6 of the Ethernet jack, using a punch tool or a narrow knife. I would hesitate to go by the colors marked on the ethernet jack. To ensure that the wire colors are correct on both the Ethernet jack and the Ethernet plug. Plug the other end of the Ethernet cable into the jack. This will help you see what color wire goes where on the Ethernet jack. Slots 4,5,7,8 should be empty. Do the same thing to the other ethernet jack and ethernet cable.

Step 5: Powering the Ethernet Jack

Take one of the striped ends of your ac adapter. You will notice that one of the wires will have a white stripe or writing on it. Lets take the marked (striped) wire and push it into slot #8 of the ethernet jack. Take the non-marked wire and push it into slot #4. Take the other striped piece from your ac adapter and do the same to the other ethernet jack.

You should now have 2 parts. One will have the AC adapter power block connected. The other will have the AC power plug connected. ( as pictured). Use electrical tape to secure the AC wire to the ethernet cable. This will help to relieve the strain on the AC wires.

Step 6: The End Results

My router and UPS are located upstairs. I plug the AC adapter into the battery side of the UPS. I then connect the ethernet plug into the router. I then plug in 30ft ethernet cable that runs downstairs to a network switch. The switch uses the other adapter to provide power and network connection.

This solution allows you to use any length of Ethernet (cat5) cable between the devices.
*Note -- This method may not work on Gigabyte devices, since all 8 wires are used. This should only be used on 10/100mbps base network devices. 



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    11 Discussions


    9 years ago on Introduction

    This is DC Power over Ethernet. It's not the same as commercial POE which is a misnomer because POE uses AC power to carry Ethernet (10/100) Signal.

    3 replies

    Reply 2 years ago

    POE is the correct term for this device, and you will never find a HomePlug device described as POE, please remove your comment. https://en.wikipedia.org/wiki/HomePlug


    Reply 9 years ago on Introduction

    I updated the title of the instructable and removed the reference to it being similar to commercial POE adapters.


    Reply 9 years ago on Introduction

    Actually the Commercial POE is the misnomer since theirs should be called EOP (Ethernet over Power). The Industry also has POE Injectors which is what yours project is. They also call them POE which confuse the heck out of consumers.


    9 years ago on Introduction

    You can use this to send power over your ethernet wiring if you control both the power provider and power consumer.  But it isn't "real PoE", and won't be compatible with commercial PoE devices.  Real PoE has a complicated and expensive protocol associated with requesting/supplying power, uses 48V over the wires (requiring a relatively expensive DC/DC converter at the consumer) and can actually send power and data over the same wires.

    1 reply

    Reply 3 years ago

    I'm using 24v from my UPS system to inject onto the Ethernet cable, using 4 wires.

    On the other end, I'm using an inexpensive Dc to Dc converter (LM2596 type from Ebay) to output 5v or 12v as needed at the power user end.

    This setup allows me to power most devices, without concern for voltage drop on the cable.

    I do suggest you make sure you don't exceed recommended current limits for the cable ..

    For future reference, what is the max amperage and voltage you can run over the ethernet cable.  Is it safer to install a fuse somewhere if you are putting a router in a location that is not easily accessible?

    3 replies

    Reply 7 years ago on Introduction

    I'm pushing 13.6 volts (to a12 volt wrt54g) used 4 wires 2 for positive and 2 negative on a 100 foot cat5 cable.
    But the linksys routers run on any voltage from 5 to 18 volts (I'm not brave enough to try above 18 volts)
    The main problem you might have is "voltage drop" with low voltage routers like 5-7 volts especially. you may need to use a higher voltage wall-wart to account for the drop.

    I don't remember the exact answer in watts you could pull through 2 strands of cat 5 but mine was way inside the safety buffer. but if you are going 100 meters on a single strand with a low voltage router you could have troubles. Most wall-warts provide less than an amp of current.


    Reply 7 years ago on Introduction

    Voltage is not as important as ampacity....


    Sending too much current will melt things. Since in cat5 we have a bundle of wires I would use the eclosed ampacity in the above referenced table. Most of the powered switches and routers that I have seen have a rated power of 1.5A or less. So if your cat-5 is 24guage or better, I would feel safe using it.

    I am not sure what the Max voltage is. The network switch that I am powering over the ethernet  is about 7volts.


    9 years ago on Introduction

     I did something very similar to this to carry telephone over the WB/B pair of a buried Cat5 to my camper...  should I both to make an instructible?