Power over Ethernet?

Hi, I am using the Nuelectronics Ethernet shield and wonder if there is any chance to wire it the way that i can use the currency from ethernet to the VIN.. has anyone ever tried this?

The 802.3af PoE voltage is normally 48 Volts. The PoE midspan/switch checks if the device in the end of the cable is cabable to take the PoE power in and gives the power only if the device responds correctly. So the voltage lines in ethernet cable are not always powered.

The device can be made with some components, but I think that easiest solution could be to buy an separate PoE Splitter, which extracts the power from PoE line to normal ethernet and 12VDC, for example.

Or if you are not using the standard PoE, you can always use the unused Cat pairs to transfer the power to the device.

I found these that are not too expensive: http://www.silvertel.com/poe_products.htm No personal experience...

Reviving an old thread, but I just wrote up a tutorial on how to do cheap home-brew PoE with Arduino in case anyone wants to give it a try:




I'm not sure about the "standards" for POE, but you can wire your RJ45 connectors for four conductor 10base-t operation, and use the other four conductors in the cat5 cable for what ever power setup you want to use.

Hi All

It’s perfectly easy to shove some extra power down the unused wires, as Jonathan Oxer says, but you also have to modify your powering device. I’ve used this very successfully with hand-modified ehternet hubs, but it’s pretty nasty. Real Power over Ethernet, following the IEEE 802.3af standard is tricky for a number of reasons (see the wikipedia entry for details, or follow links there to the real standards).

You can modify an existing board to do power over ethernet, but it’s fiddly. In briref you have to use a different Mag Jack and then you can get to the right signals to go to a POE modules: I used the Silver Telecom modules, which I found to be excellent.

The basic issue of the Mag Jack is that you need to get access to the centre-taps of the little transformers built into the socket. Most are not designed for this, so it’s impossible.

On my board I removed the Mag Jack, soldered wires to the holes, and took them to my new POE Mag Jack. From the additional pins of the POE Mag Jack I wired the POE module.

Happy to send a picture of my modified board (or upload it if I find out how).

In the end I made PCBs for my POE work, called the Imaguino, which you can read about here:


Hope that’s of some use.



Your Imaguino board looks very interesting !

The Imaguino page mentions that you would be happy to publish the circuit diagrams and other details of the boards. Could you please do so ? I'm trying to work out how to power both an LCD display and an Arduino over PoE and your Imaguino design seems to fit the bill.

Thanks John


Your Imaguino board looks like it is what I want for some tinkering projects. 802.3af POE is the cleanest form of power for my projects and I like what you did with the post clamp design as well.

The Imaguino page mentions that you would be happy to publish the circuit diagrams and other details of the boards. Could you please do so ?