PoE (Power over ethernet) with Mikrotik Routerboards

If you want to connect your RB411, RB433, RB711Hn or any other routerboard that has POE enabled on it ports, and do not want to buy PoE injectors, this is how you can connect it if you have power supply with 12V or any other that is specified for your device.

NOTE! This is only for simple 100 mb PoE, not for IEEE 802.3af devices! They need special electronics that negotiate with 802.3af injectors.

100 MB ethernet uses only 4 wires out of 8 wires that are in standard ethernet cable. There are 4 pairs of wires and they are orange, green, blue and brown. For T-568B Straight-Through Ethernet Cable you use wiring like this:

In 100MB ethernet, blue, blue-white, brown and brown-white are not used, so they can be used to transfer power to device. For routerboards, blue wires are positive and brown wires are negative.

So how do you connect?
You crimp your cable like on picture above (using T-568B standard) and near place you want to connect power adapter you remove the insulation (only the outer white layer that are around all wires) and cut blue and brown wires. Then you remove the insulation from them, but only on ones that are going to your routerboard, and connect blue and blue-white together, and brown and brown-white together. Then you cut connector from your power supply and measure what is positive and what is negative wire. You can do that by using voltmeter(place range to 20V or more DC-direct current, black wire to ground, red wire to voltage measurement) and placing one wire on black and another on red wire. If your voltmeter show +12 or any other voltage, then connect wire that was on black wire to brown and from red wire to blue. On the other hand, if your voltmeter shown -12V then you should do the opposite: wire that was connected to red connect to brown wires, and wire that was connected to black connect to blue wires.

Here is how I connected to my computer. I used +12V from my computer as power supply from molex connector:

Here you see orange and green wires go to connector and other 4 wires go to molex connector connected to my power supply.Other end of UTP is connected to routerboard 411, crimped as shown in first picture.