Passive PoE Injector Cable Set
Now available from PMD Way are these great Passive PoE Injector Cable Sets. They're a great idea and useful for projects that use Ethernet and need power.
You can use these cables for your own projects that don't need to meet official "Power over Ethernet" standards.They are not for official 48V Power over Ethernet.
The first cable - the Injector - has an Ethernet socket and a 2.1mm DC socket. Connect a power supply and the power is fed to Ethernet pins 4 and 5, with GND connected to 7 and 8.
The second cable - the Extractor - is the opposite, and takes the power out to 2.1mm DC power plug.
The other cable (the extractor half) does the opposite, splitting off pins 4,5 and 7,8 and bringing them to a 2.1mm DC barrel plug. You can then use the DC plug to power your projects as if it was connected directly to the wall adapter.
As the DC power uses Ethernet pins 4, 5, 7 and 8 you cannot use Gigabit Ethernet. 10/100 Ethernet is fine.