PoE with Arduino

Is it posible to use PoE switches to give power supply to arduino with ethernet interface? Regards.

No. PoE modules tend to be large and expensive (more expensive than the arduino), and tend to be focused on providing enough power for relatively large devices like an IP phone.

I did find these folks http://www.silvertel.com/poe_products.htm who have some 5 to 10W 5V supplies at under $15 each. Watch out for the lack of isolation on the cheaper modules, though :-(

Nope. That is not supported on the ethernet shield.

PoE (standard PoE, anyway) offers a relatively high DC voltage of 48V; that's over the limit for a standard Arduino regulator.


It is apparently possible to buy or make small devices that fit between two non-POE devices and enable POE between the two devices but not to the devices. Essentially they inject and then remove the power from the line and then feed it into the normal power input on the target device.

I have no experience with such things though.


Follower said it right, there are power injectors that runs on Cat5 cables. They are used for Hiperlan antennas which allows to run only one cable for data and power to the antenna (which is an active device). Have a look on these http://eidusa.com/Electronics_Kits_PoE_injector.htm

My impression was that the original poster already had an Ethernet Switch that PROVIDED PoE, and was looking for the Arduino ethernet to be able to USE that power...

well, I am trying ti do a domotic installation including arduinos in each room to control, windows, temperature, light and so on. I am interconecting all of them trought a switch. My idea is minimize the wiring and avoiding install a small power supply for each arduino. I am activating signals for air conditioner or big loads thru a solid stage relays. I will read write in the diferent arduinos thru ethernet, and a tablet pc will have the main domotic program Regards.

Hi comander,

I'm using arduinos for exactly the same purpouse, and what I do (and I know its not a very "canonical" way of doing It is that I use the white-brown pair of the cat5 cable to supply 12V that will go straight to the different relays that the arduino controls and, throug a 7807 with a nice disipator, to the arduino.

This works perfect for me and it's been running for a couple years with no probs.

I was messing around to see if there was a nicer way to doit with PoE, but seems like there is no cheap solution.

Regards Chano

Hi conander,

I'm not aware of any ethernet shields that will split out the POE which is a real shame as that would be great, but you might be intrested in something like the D-Link DWL-P50 which is a 802.3af compliant splitter.

I got one a couple of days ago and tried it on my Arduino, it appears to work well receiving power from a 3COM POE switch.

I've put together a blog post about powering the Arduino from Power Over Ethernet if you want to read a bit more about.

Sorry but the links will have to be in the next reply, as it's my first post I'm not allowed to use links. :'(


Hi conander,

OK, second attempt, hopefully with links this time!

You can find more info on the D-Link DWL-P50 at http://www.dlink.com/products/?pid=368.

My blog post : powering the Arduino from POE with a DWL-P50.


I'm a bit late to the party ... but here goes

Of course, you could always make a custom Ethernet interface with POE

Can you give some pointers on how to do this? I am also looking into using an arduino type of solution for my home automation. I'm not (yet) familiar to board design or even to electronics. So a 101 would be welcome. I am familiar with programming though.

why do you think you NEED something like POE?

It's not because you go custom that you cannot use (good) existing technologies. For starters, I already own a PoE switch for my IP Phones and I have plenty of spare ports, so I already have hardware I can/want to use. Second, I don't want to risk blowing up any of my other switch ports by experimenting with power injection. Third, I prefer not to have clutter of injecting power on the required lines in my cable closet. PoE switch is a clean solution. Forth, it is probably more power efficient to have a single PoE switch than to have 15 power adapters and easier for UPS solutions. Fifth, the PoE switch has a web interface which allows me to restart any "frozen board" (if that exists) remotely and monitor power usage.

btw. I'm glad to absorb the $15-30 per board for a solution that gives me all of the above. Even for the 15-20 boards I'm looking for that is a "mere" $225-600 surplus. Ideally, it'd be a single board with everything integrated.

Is there anyone who can assist with building these boards? The things I want it to do (I want a single board per room if possible). - network enabled (needs to communicate with other boards) - PoE enabled - control 2-6 light points (on, off, dimmer) - check temperature (2-4 probes) - control shutters (open/close 2 relays?) - check magnetized "security" strips (input relays?) - smoke detector - LCD panel - 6-8 'buttons' for manual control - sufficient "power" to run it all (RAM/IOs/...)

"Specialized" additional boards: - rfid reader - open/close door lock

If anyone has experience with this, please don't hesitate to contact me.

PoE is a standard. 48Vdc on some combination of the wire pairs, with a relatively complex scheme to tell the switch that you're ready for power, and how much you're going to want. There are special chips ($4) with associated special transformers ($4), and before you know it you've spent quite a lot. A cheaper solution OUGHT to be possible... Meanwhile, the Silvertel modules look better and better...

Hi All

I've written up a brief description of the Imaguino, which is an industrial implementation of the Arduino Duemilenova circuit and the ethernet shield, with 802.3af Power over Ethernet (using the Silver Telecom modules).

They've been installed in a number of places and have been very reliable. Happy to share experiences, circuit diagrams and so on if there's any interest.


Any interest?

Regards, Jonathan

Hey, another Jonathan! Cool.

The Imaguino looks really nice as a highly-durable system. I can imagine you've had some painful experiences (or at least annoyances) with ad-hoc systems that then lead you to developing an integrated system that does exactly what you want. Nice work.

For something that's more like a traditional Ethernet shield but with PoE support (for people who want to add it to a Duemilanove or equivalent) this may also be of interest:

www.freetronics.com/power-over-ethernet-for-arduino www.freetronics.com/poe-injector-4ch www.freetronics.com/ethernet-shield

Yes, to be exact PoE is several different standards, and they are not interchangeable.

That’s what I like about “standards”, you have so many to chose from! :slight_smile:

Hi All

Richard: not sure what you mean when you say that POE is several standards. Could you tell us what ambiguities you've found?

As far as I'm aware, we have 802.3af (from 2003) and its later enhancement 802.3at (from 2009). Prior to 2003 a number of manufacturers did a lot of non-standard things, and lots of people have simply powered spare pairs for 10baseT and 100baseT.

I have tested 802.3af powered devices in lots of powering switches and the only difficulties I've ever had have been with Cisco power injectors and pre-802.3af phones.

Within the standard, a number of switches have a slight surprise in that they will only supply 7.5W per line instead of 13 W.

In passing, I notice that Netgear and Cisco now sell cheap 8-port switches with four powered sockets. I assume these are targetted at small office environments with a phone or two and maybe an access point or camera to power.

Regards Jonathan.

Hello all, Laventhol's Imaguino looks very nice! Me too fall into the reset issue with the eth shield and, after adding a capacitor (and a diode too, to quick discharge during POWER OFF), i got the "no reset after flashing" issue. So, the reset supervisor added in Imaguino is mandatory for reliable operation! I hope you will release the project and/or the TFTP bootloader that is VERY interesting too! Regards, Rino

That sounds like a really useful implementation Jonathan. Is it commercially available?

Could current become an issue here? Home automation sounds like driving things like relays, which are nasty guys for creating current spikes, that could not only interfere with the signals coming up the wire, but (assuming it is a standard Ethernet cable) could damage that too…

Note, never used PoE, so i’m not sure, but it sounds fraught with danger, I/O and high current shouldn’t go near each other if you ask me.
[edit]ok, I did some reading on wikipedia, and there are 2 official variant of PoE it would seem, one that can provide up to 25.5watts (IEEE802.3af2009) and one that can give up to 15 watts (IEEE802.3af2003) also, both are designed for constant draw applications like a switch, or a phone, not for home automation (relays, motors and other electromagnetic menaces) I should really consider using a separate power source.

A phone is by no means a "constant draw" application... A "good" PoE power supply puts a significant amount of isolation between the power-consuming device and the actual ethernet cables. As long as you stay within specs (15W isn't a lot by motor standards) and use an "isolated" PoE controller, you shouldn't have any more concerns than you do plugging an iPhone into a wall-powered charger.