How to make a simple modification to a LAN switch, so it can deliver power via the LAN cable.


Old 100Mbps LAN switches are free nowadays, because most things run on 1Gbps.
They are easy to modify as PoE injector, so when using e.g. multiple security cameras, that only have a 100Mbps connection, it is a good idea to do the following modification.


A 100Mbps LAN only uses 2 of the 4 wire pairs in the LAN cable, so the simplest way to implement PoE is to use the 3rd pair for the positive side of the PoE voltage and the 4th pair for the negative side.
This can be accomplished by adding the following wiring to an existing 100Mbps switch:

LAN cable pin signal in switch PoE supply wiring
orange/white 1 RX+
orange 2 RX-
green/white 3 TX+
blue 4 shorted to 5 Vpos
blue/white 5 shorted to 4 Vpos
green 6 TX-
brown/white 7 shorted to 8 Vneg
brown 8 shorted to 7 Vneg


Here the above PoE wiring is added for ports 1,2 and 3 of a LAN switch.

PoE



Some standard 5.5mm DC connectors can connect to the original DC supply adapters that normally are plugged into your camera.

PoE


Here port1 delivers power over the LAN cable.

PoE


Final setup for one of the cameras:

webcam






This shows the pin numbering and colour followingorder of a LAN cable:

webcam



That's it!.








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