It is the idea of UK-based manufacturer Silvertel which has released a circuit and PCB layout for a 5V PoE adapter board and the information is available for free download and use by any manufacturer of accessories or general hobbyists.
As the adapter board can be used to power any 5V device, up to a power of 9W, it is suitable for powering a Raspberry Pi via a standard USB cable or DC connection.
This PoE splitter board has also been used to power the MarS i.MX6, Olimex A10-OLinuXino-LIME, BeagleBone Black, Element 14 RIoTboard.
Silvertel has made available through its website a bill of materials (parts readily available from on-line electronic component suppliers), a circuit schematic and the PCB layout.
Total compoent cost is less than £7 ($11 or €8.50), according to Silvertel.
The module provides an IEEE 802.3 compliant PoE input, capable of taking PoE power and data from any PoE injector. The 5V/1.8A output is provided on a USB connector or DC plug.
The board provides an IEEE802.3af signature to avoid any potential damage that could be caused by incorrect or shorted Ethernet cables. 5V-PoE-adaptor-board-back.
The board has mounting holes compatible with the Raspberry Pi board.