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PoEPi: Pi Zero Power over Ethernet with PHY

It can power the Raspberry Pi Zero over Ethernet. The board also adds an Ethernet Phy to the Raspberry Pi Zero to give you full Ethernet

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PoEPi is a power over Ethernet Raspberry Pi Zero board, it uses power injected into a Ethernet cable and uses it to power itself and other things. I think one of the reasons that the PiZero was designed without major USB features was to push developers towards creating connected devices that don't have direct user interaction (hence the low number of USB ports).

After I realized that my PiZero USB hub was a silly project (why not just buy a normal Pi :P) I decided I wanted to make a project that had no USB connected components at all. On an Ethernet network the PiZero can be used as a remote sensor, remote lighting control or remote audio control.

- ENC28J60, because its cheap and there is native support in Linux
- IEEE 802.3af Power over Ethernet (Max 15W, more than the Pi Needs)
- A 3.3v Linear regulator for the PHY
- Back power protection (if i can fit it)
- Using the PiZero is cheaper than an Ardunio so it can be used for simple tasks as well


Project Status

  • Designs finished
  • Waiting on boards for first prototype
  • Docs almost done

Concept

Ever since the Pi Zero arrived people have had issues with Wifi and the USB connectors. We have seen a good deal of people hacking on USB connectors and Wifi modules. I think that using the Raspberry Pi as a computer has had to many people focused on the applications of using it as small desktop. If you want a small computer just use the Raspberry Pi 2.


I wanted to use the Raspberry Pi Zero in a different way. I wanted to enable the Raspberry Pi to easily and safety be used as a Linux machine that you can be implement as more than just a computer. Putting the Raspberry Pi Zero on a PoE injected network allows you to do all kinds of things with the Pi. The only draw back is the slight increase in system cost (and even that can be argued for)

  • Power and communicate with the Pi over a single cable
  • High reliability system design
  • Power external features with the remaining power (about 12W!)
  • Centralized UPS system (each Pi doesn't need its own battery)
  • Pi can be placed far from PoE switch or existing network
  • You do not need to be an Electrician to install

What is PoE?

Power over Ethernet is a method of injecting power into an Ethernet line and recovering it on the other end while making no disruption to the data on the line. PoE has been used for a long time and you can get PoE routers and injectors from any local computer store.

Board Design

The design of the hardware for this device is critical because it provides the backbone for all of the Pi's functionality, mainly power. When I first had the idea of putting the Raspberry Pi Zero on PoE I first went hunting for the best PoE solution. I wanted a system that could fit in the Pi Zero board size and was also simple enough that people wouldn't be afraid to develop with it on there own. Some of the main features that where considered at the beginning of the process where;

  • current limiting for the PoE (may be seen in some applications)
  • PoE isolation. Most cheap modules don't do this and it could kill the Pi
  • resettable fuse
  • off board Ethernet connector (could be used to bring the design to HAT specs)
  • 100T-Base Ethernet (still possible)
  • DC/DC 3.3V supply (opted for LDO instead)

Ethernet Selection

This was a heated discussion between me and a couple friends who have been giving me input. Two of them do kernel dev work so they where pretty upset about my choice of the ENC28J60 (its slow). My reason for this selection at the moment is that there is a lot of magnetics in a small area. Once I can scope it and see whats going on I will be able to upgrade the Ethernet. I dont see any reason why I wouldn't be able to use the ENC624J600.

PoEPi Derivatives

These are boards that are designed around the PoEPi template. They are based on applications that I could see myself needing at home and work over the next year or so. When thinking of these applications I also try and thing of the alternative solutions

  • PoEPi WS2812 controller and power supply (Done, boards ordered)
    • Supply a chain of about 70 WS2812s while still powering the Pi
    • Level shifting and protection on the GPIO that controls the Din pin.
  • PoEPi servo controller (probably working on it right now)
    • control and power up to 8 servos
    • current limiting to prevent Pi from restarting
  • PoEPi speaker amplifier (Done)
    • uses the Pi audio output (mono)
    • integrated amplifier based on LM4871
    • amplifier selected to eliminate the need for additional power supplies.
    • amplifier shutdown pin controlled by the Pi
    • RC circuit to act as DAC for PWM signal to amplifier

KiCad_speaker-amplifier.tar.gz

KiCad Design files for the board and project based libraries

gzip - 97.35 kB - 02/19/2016 at 13:32

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KiCad_ws2812-controller.tar.gz

KiCad Design files for the board and project based libraries

gzip - 86.63 kB - 02/19/2016 at 13:32

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KiCad_servo-controller.tar.gz

KiCad Design files for the board and project based libraries

gzip - 95.85 kB - 02/19/2016 at 13:32

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Photo_Render.blend

Blender scene to render images of the board

package - 10.46 MB - 02/13/2016 at 01:35

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  • It works! But then I broke it :(

    julien07/09/2016 at 21:41 2 comments

    After a good amount of time spent soldering and testing I plugged the PoePi into an Ethernet PoE switch and it worked! I was getting 4.8v out of the header which is barley enough to run the Pi (based on the USB standard). The low voltage can be accounted for by changing one of the bias resistors dividing the signal going into the opto coupler.

    So I decided to change the resistor and fix some other components that looked a little ugly. During this process I accidentally left a trail of solder between the end of a cap and a resistor. This cause the transistor driving the isolation transformer to sink a whole bunch of current. So its dead.

    Luckily I have to make another DigiKey order tomorrow so hopefully its back up and running.

    If you are going to build of this design you can probably start using the PoE part of the design. But I still havnt actually tested the Ethernet communications so I would be weary of that.

  • Boards are made, now to populate

    julien06/28/2016 at 19:02 1 comment

    This project has been sitting for over 3 months now and I feel bad. I got completely floored at work and then took some time off to travel and decompress. But I am back at it now and thanks to some help from a fellow hackaday'er' this is the first project on my list. Like I mentioned in the beginning of this project there is a lot of excitement around wireless, batteries and general IoT mumbo jumbo. And that all well and good but sometime you just need more current, and you need it all the time. Some solutions just arnt going to be battery powered. Thats why I made this board!

    Please ignore the fancy ESD rated table cloth. The boards turned out great, they are from that company that gives you big discounts if you blog about how great they are 'cough PCBway'. For the money the board quality is good. The silkscreen is hit and miss, sometimes its to blotchy to read the refDefs and the pad adhesion is pretty bad. I have had a pad become detached during baking which is pretty weird.

    I also got my first meter of WS2812s!

    The components for this board should show up this week and hopefully I can populate it some time in the evening.

  • How to Remap Audio with .dts

    julien02/23/2016 at 09:40 0 comments

    Device tree worked used to always scare me but once you have done enough of it on the BBB its pretty straight forward. The documentation for the device tree remapping is finished. The doc is on the git wiki. I’m still a little upset that the git wiki formatting hasn’t been made to match actual wiki syntax.

    Check it out here

    Take a look and let me know if anything is off. Maybe ill make a script to automate this... but then again no one would learn anything.

  • Docs are up!

    julien02/19/2016 at 13:26 0 comments

    I have been working on some docs for this project on the Wiki. Im excited to get this project going and waiting for the boards is killing me, wish I could afford fast shipping.

    I have been working on some docs using the Github wiki feature. Its very nice except that you cant seem to do nested lists. Most of the docs are done but I am still working on the Audio board. The device tree remapping of the audio is a bit more complex for users than just installing a python package.

    Check them out!

  • PoEPi Servo Control Board

    julien02/19/2016 at 13:20 0 comments

    Who doesn't love moving motors from far away? Well that was the point of this design. The power that is available in PoE is easily enough to control some small motors as long as you are careful what you are doing. I decided to put only 4 servos on the board but this can be changed easily if someone is making a different version of the board. The Servos are controlled from the GPIO, you can use whatever library you want to control them, I have some docs here.

    This is the schematic section that describes the servos. There is current limiting in case the motors are to big or they experience a stall condition. This part is untested and it would be great to have some feedback. I simulated it but I have a bad history with Spice. The low side MOSFET will disable the ground of the servos.

    The board itself has the servo headers sticking out so they don't interfere with the Pi. I hate to continually violate the Pis form factor but those 3 pin right angle headers are hard to get a hold of.

  • Audio PoEPi Finished

    julien02/16/2016 at 11:54 0 comments

    Early in the project I mentioned that I would be making a couple variations of PoEPi so that other people can get an idea of how to make there own. While I sit and wait for my boards to come in 7 - 32 days (its always 32 days for some reason) I have created another version of the PoePi.

    This version is a speaker amplifier. It uses the PiZeros Audio capabilities routed through a GPIO to make a speaker amplifier. This way you can make your own PA system or an excessive audio system where each speaker can also be an audio server.

    Check out the details on the project page. I have also started a project log for this project on my blog OpenFET.

    I am buy no means a good Audio engineer so it would be great if someone could give me some feedback on my design. I will wait until the other boards come back before ordering these ones.

    One of the things I am known for is very very bad art and bad spelling. I wanted a cool logo for this project and had to use every ounce of creativity I had to come up with one. In the bottom right hand corner of the board you will notice the fun PoEPi logo. It was supposed to be a smiling RJ45 connector but it just looks evil.

  • BOM finished

    julien02/11/2016 at 14:18 0 comments

    The component selection and BOM are finished! Its always the hardest part and can require a lot of attention to detail. While creating the BOM i realized that I had sized one of the Caps wrong on the PoE circuit. With this cap to small the power would have been spotty at high loads.

    The BOM is formated for mouser. If you are using Digikey or some other supplier you can use Mousers BOM tool to export the manufacturer part numbers then load them to your distributor. The cost to make one board is .... $55! Seems expensive, well its mostly in the transformers. The cost drops to about $32 at 100. Several of these parts can be switch for low cost versions. I used high quality caps to avoid blowing things up early in the building.

    Im still looking for feedback if you can give it. I want the PoE circuit to be solid before I start adapting other designs. I will be ordering the board next week hopefully.

  • First board design *almost* done

    julien02/09/2016 at 12:04 0 comments

    The first board design is almost done. After having a discussion with someone about PoE I want to go back and double check the PoE design on the board. But if anything changes it will be minor.

    The Layout and routing is finished and the good news is that there is lots of room left for custom applications. We will be building a couple custom applications for this board as examples of what can be done with PoE.

    I am looking for suggestions!

  • Routing Continues, and whats with HAT anyway?

    julien02/07/2016 at 06:19 0 comments

    The routing and placement of this board is going pretty well. There is still some discussion about where the Ethernet connector will go and how it will be configured. Most likely it looks I will use a generic foot print so multiple connectors can be used as well as having a small connector for external mounting (maybe).

    I have managed to pack everything in pretty tight and have kept most of the routing on the top layer. I have been carfull with the power planes as well, there are a lot of magnetics in a tight space :S. There should be lots of space on the bottom layer for people to add there own designs as well. So far I would like to do the following and I am looking for more ideas if you want to throw in (or contribute to the project :D). These are all different boards:

    - A ws2812 driver and connector (we can run almost 100 ws2812s from the basic PoE). This is the one I am working on right now.

    - an 8w mono speaker driver (maybe for an intercom system)

    - high power LED driver for a single LED, or maybe tri color LED

    - servo driver for who knows what reasons (probably pan and tilt). Going to have to add current limiting for servo stall condition.

    A quick note about Hats. The more I design with the idea of the HAT specification in mind the more I realize it is pretty pointless, it fate may be the same as the OSHW logo. People are selling things that are not HATs at all and calling them HATs, there is no enforcing of these parts going on. And because the hardware of most "HATs" is not open its hard to actually check if they meet the standard. The Raspberry Pi foundation may be able to afford buying these boards and checking them for there "HATness". Then there can be an offical list and blacklist of boards. I like the standard and I think its handy in some applications but probably not this one. Long story short Im losing the eeprom unless anyone has any objections?

  • Where oh where should the RJ45 go?

    julien02/05/2016 at 06:05 9 comments

    Sometimes you get deep into a schematic design and forget to ask the question where is it all going to fit? I assumed that an RJ45 would fit nicely at the end of the PiZero. Well it doesn't, it violates the footprint of the Pi connector and the mounting holes. It could be placed in the center of the board but that will seriously disrupt the flow of the routing (which will be tight).

    An alternative is to overhang the connector. This violates the Hat specs but I dont yet see the benefit to constraining the board to those specs. Any ideas on where the RJ45 conn can go?

View all 10 project logs

  • 1
    Step 1

    Enable the Ethernet on the Raspberry Pi Zero

    First we need to enable SPI on the Raspberry Pi. If you are doing a lot of hardware hacking on the Pi there is a chance that you have already done this.

    sudo nano /etc/modprobe.d/raspi-blacklist.conf
    In this file you want to put a "#" symbol in front of the line that says;
    blacklist spi-bcm2708

    Then hit "CTRL-O" then CTRL-X" to exit the nano application.

    You may also enable SPI through the Raspberry Pi Desktop by going to preferences and enabling SPI in the Raspberry Pi Configuration page.

    After you have done this we need to enable the use of the chip that is on the PoEPi board. This is done by adding a device overlay to the boot configuration file. Just enter the following line in a terminal.

    sudo echo "dtoverlay=enc28j60" >> boot/config.txt
    Now you can reboot the Raspberry Pi and you will have an Ethernet connection! You can now ssh into the Rasberry Pi once it is placed into a PoE network.
  • 2
    Step 2

    !!This step is in progress!!

    Making your own PoEPi board

    If you want to make your own custom PoEPi application you can build on this board and make your own PCBs. All you need is some KiCad knowledge and an idea. There is lots of room on the board to add your own devices.

    Before you get started there are some things that you should keep in mind before starting your design.

    • Your application does not use more than 10W of power (about 2A from the 5v supply)
    • Your application uses either 5v or 3.3v (or a combination)
    • Your application will not draw big current spikes, it may make the Pi reboot
    • The devices on your board wont collide with the Raspberry Pi when assembled.

View all instructions

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Discussions

Chaemelion wrote 07/17/2017 at 04:18 point

I could use a few of these boards as well. Wish there were some more recent updates.

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btpp78 wrote 05/13/2017 at 21:37 point

Likewise. I wish this were available today; I am ordering boards right now. But I will definitely be interested when this project launches.

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ccdanieldb wrote 04/25/2017 at 05:42 point

Wow,  This is great.  Can you add my name to the list.  Have you considered a something like Kickstarter.  

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mica.sbg wrote 04/21/2017 at 17:21 point

I'm sure you'll sell lots of this little boards. I'd like to put my name on the list as well.

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eduindam wrote 04/19/2017 at 07:41 point

This is great. Hoping there will be some for sale soon. I really need at least twenty of these things like... yesterday.

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Hash wrote 04/06/2017 at 19:11 point

Very interested in this too. Any plans of having some for sale soon?

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Chris Scott wrote 04/04/2017 at 15:12 point

Any update on your testing were you able to get it to work?  Would like to use this design if it's proven.  Thank you!

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jesper bang wrote 03/14/2017 at 18:38 point

Anyone ever finished this project .. this is exactly what I need for my project ?? 

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mvn wrote 02/25/2017 at 13:07 point

Hey - amazing work! Any chance of you producing a few of these and selling them?

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seawinds wrote 12/18/2016 at 19:52 point

Hi 

I have just started to look closer at this project wanting to use it for my owne project.
Looking a bit closer at the schematics and the board layout, I find it a bit confusing.
Lookig at the RJ45 pins and connections to the Bridge D2.

1. I see that you are using RJ45 Pins
   1&2 3&4 TX/TR Were the standard is 1&2 3&6.
  You are using 5&6 7&8  rathr than 4&5 7&8 As Spare. Am I missing somethng here?

2. Looking at the stamping of D2 SS & +- seem to be reversed.
   so RJ45 Spare pair 5&6 7&8 look like they are going to
   SS on D2 but if I look at the actual board you made the
   chip looks reveresd. I assume this is just a stamping error.

Sorry for asking such basic questions but just wanted to get this right in my head.

Regards
Dave

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robbie.francis wrote 07/09/2016 at 12:38 point

This is great!  I love my Pi2's with the Pi POE Hat - And am defo interested in a remote POE Airplay speakers!  Any plans to sell the POE boards?

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julien wrote 07/09/2016 at 19:34 point

Thanks! Yeah i might through them up on Tindie when I get the design really nailed down. Im doing the testing for the current one today (update soon!) and mabye i will have one on tindie in a couple weeks. I think there might be a cheaper way to go if i remove the isolation from the PoE. Im still not sure if people care about isolation with the PiZero. The device is cheap but hard to get a hold of. 

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cwo wrote 06/30/2016 at 20:59 point

Very excited to see this project moving along - thanks for your hard work! How many WS2812s do you expect it will be able to drive, allowing for full power on all LEDs, when powered from a class 3 PoE supply (12.95W)? 

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julien wrote 07/01/2016 at 12:41 point

Well depending on what power the Pi is using, lets say 3W max. We are left with about 2 amps to work with. If we take the WS2812s for there face value and say they will each always be using 60mA then we can run 34 of them. Now I have a string of 72 of them and I think it will be able to power them all without a problem.

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Dan Julio wrote 02/23/2016 at 20:23 point

I like your idea of different personalities for this.  POE provides a lot of opportunity.

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julien wrote 02/24/2016 at 00:40 point

Thanks! Yeah it really does. The challenge is getting the cost down. 

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Dan Julio wrote 02/24/2016 at 05:25 point

yup!

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seawinds wrote 11/28/2016 at 14:44 point

Hi Julien Great project, Is this card available yet to purchase? I would like to test it in a project I am working on.

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Jos van Bakel wrote 02/06/2016 at 15:30 point

I like what you are making! I was thinking about powering a zero with PoE too, but was stuck at finding a good, small and cheap PoE splitter. What is your estimation for a price for this? Or is it too soon too tell?

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julien wrote 02/06/2016 at 23:42 point

PoE injectors are usually about $10 which is a bit more than a wall USB supply but you get a good amount of power out of it. Its to soon to tell the price of this board. The PHY is super cheap but some of the magnetics are expensive. Mabye around $25 but thats a big guess. The hope is that this design can be easily adapted, I was going to make one with a speaker amplifier on it. 

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julien wrote 02/27/2016 at 05:17 point

I added the price in one of the project logs. Turns out its about $50 if you just make one. I could make a cheaper design that uses a none isolated design but people might get mad. But you are only killing an unobtainable $5 board if the power supply goes bonkers. 

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hipolito.lopes wrote 02/05/2016 at 13:10 point

Back when laptops had no WiFi and some doesnt even had an ethernet port there were some PCMCIA ethernet cards which used a small footprint connector on the interface and a cable adapter...I wonder if this couldnt fit better than the huge ethernet connector directly soldered to the board.

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julien wrote 02/05/2016 at 14:42 point

hmmm thanks for the suggestion, i had no idea those existed. Ill start poking around for a part number thats in production.  

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K.C. Lee wrote 02/02/2016 at 16:02 point

Your feedback path from secondary side has GND as feedback instead of +5V in the schematic.

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julien wrote 02/03/2016 at 02:26 point

Good catch, I was trying to make it look pretty and I guess I got
carried away. Thats a pretty silly mistake. I still have a lot of
component selection to do.

  Are you sure? yes | no

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