Depending on the scope of your requirements, Power over Ethernet (PoE) components can get pretty pricey. [Fire] wrote in to share a 4-port PoE solution he put together for under 20 euros (Ignore ...
PSE outputs are limited to 15.4 W per RJ-45 port. Because longer Ethernet links exhibit a significant drop, voltages as high as 57 VDC may be used with PoE injectors. Electrical specifications for PoE ...