A DIY PoE solution

[FriendtoGeoff]

<Usual disclaimers about breaking your pi etc. apply>

I have just completed a successful hack to use this PoE module:

http://uk.farnell.com/infomart-it-solut ... dp/1902521

to power my pi direct from a Netgear FS108P PoE Ethernet switch

I could have replaced the Ethernet socket on the pi with a magjack PoE replacement such as:

http://uk.farnell.com/stewart-connector ... dp/1901301

but I fancied a challenge. It turns out to be possible to disassemble the Ethernet socket on the pi, to replace the quadpack 75ohm resistor with 2 0603 75ohm and to bring out two wires from the mid points of the TX and RX transformers. Hook these into the PoE module and Viola! working PoE.

Photos and further details available on request.

[agreenhalgh]

It would be great to see the details of your hack.

[CoDeRs]

I would also like to see some more details on your modifications. Photos would be a great start

[thipi]

Many thanks for sharing this.
Me as well really would like to get the pictures and additional docu/guidance.
Could you please provide it as offered in your post.
If you prefer PM you can send it to 'thirsch "at" benelog "dot" com'

[FriendtoGeoff]

Hello,

Sorry for the delay in responding to the requests, and thanks for all the interest. I've now done two of these and they are both happily in use.

This will definitely void your warranty. I chose to implement a Mode-A solution, with the PoE distributed as DC on top of the signalling pairs. The key here is that the standard Ethernet connector does not include the taps required to take off the PoE connections at the transformer mid-points, however these nodes are available inside the Ethernet connector. Some disassembly, tweaking and re-assembly is all that is required.

(in-case stripping and re-building the Ethernet socket is not quite your cup of tea can I recommend removing the old socket and replacing it with the MagJack PoE socket linked in my original email - probably best mounted on it's back and patched into the Rx/Tx pairs).


1) desolder and remove the Ethernet connector
2) remove the shielding shell from the connector
3) prize apart the 2 halves of the plastic chassis

IMG_1477s.jpg (51.19 KiB) Viewed 6802 times

4) locate the quad pack 75ohm terminating resistor and remove
5) fit 2 75ohm 0603 resistors to the righthand most pairs of pads
6) attach some hookup wire to the lefthand most pads

IMG_1481s.jpg (58.06 KiB) Viewed 6802 times

7) trim the plastic chassis and metal shield to provide a path for the hookup wire out of the socket
8) reassemble the socket

IMG_1482s.jpg (59.06 KiB) Viewed 6802 times

9) refit to the board
10) wire the hookup wires to the PoE module, and the output of the PoE module to the +5v and Gnd nets of the PI - a good place is at at C6.

Schematic to follow.

[FriendtoGeoff]

Here is a [very] rough schematic of the modification made to the Ethernet socket

schematic.png (56.95 KiB) Viewed 6790 times

[FriendtoGeoff]

It occurred that a picture of the PoE mod working might help inspire any of you who are thinking of trying this:

IMG_1523.jpg (51.67 KiB) Viewed 6762 times

This is a PI that is going into a very tight spot, hence the HDMI and audio connectors have been removed. The PoE module is the black circuit board sitting on top. I could't think of a better way to mount it so I just cyno'd it onto the processor

[RaTTuS]

... hence the HDMI and audio connectors have been removed. The PoE module is the black circuit board sitting on top. I could't think of a better way to mount it so I just cyno'd it onto the processor

you mean RCA + Audio removed

and why did you not power via the GPIO then you could of sat the board on the GPIO

but nice work

[bullen]

Nice, wish the foundation did this on all Raspberries but directly without transforming and we'd make 5V switches!

[Whytehorse]

I have 14 rpis+cameras running on PoE DIY. I use an ATX power supply and a 24V supply. They break down as follows:
Short: 16ft 5V direct
Long: 100ft 24V stepped down by dc-dc converter

The 24V worked for a while and then died on a couple. I think the power supply wasn't providing enough current so I ran 24AWG directly with 12V and stepped down to 5V and it works.

[jojozhouxq]

Ha, I also made a document about PoE Splitter used in Raspberry Pi. All by myself ! Very proud.... Emmm, I am not professional, so if there is any mistakes, please let me know ~~~ https://drive.google.com/open?id=0B87o5 ... 1pUSElYS0U

[jojozhouxq]

It is easy. Just find a PoE Splitter with DC48V input and DC5V output.