Trying to understand POE.
I have 3x Pi 4B+ and 2x Pi 5’s, I would like to do away with the plug packs, they take up too many power outlets. Wondered if POE might solve the power problem and remove the need to run the USB-C cables.
Is there a guide or something or does anyone have experience in using multiple Pi’s powered by POE ??
Not sure which hats I need and how to get power onto the ethernet cable. The injectors seem to be single port, multiple injectors would not be a solution.
@Liam120347 Thanks for your reply.
I have looked at all the POE Pi Hats and the 2 switches sold by Core Electronics. Also what JBHiFi and Jaycar sell. I have a better understanding now after reading a few guides and documentation.
The first part is to get a POE enabled switch. The DC input for most of these is 52V DC.
The ones JB Hi Fi sells dont seem to come with a power supply according to the web page.
The Alloy AS2008-P from Core is physically too big for the space I have. The Mercusys MS108GP looks promising with 7 ports POE and one uplink.
The Digitech 5 port and 10 port from Jaycar look the better options.
The second part is to get POE Hat’s for all the Pi’s. Most of what Core Electronics has will not fit with what is currently on the Pi’s. Heatsink/fan/NVMe board/AI board. The POE boards that may fit are the ones connected by jumper wires, so they can be mounted anywhere, although their power output is on the low side. These are the boards for Pi 3B & Pi 4B. Waveshare have a board which may work with the Pi 5, has POE power/fan/NVMe adaptor. Would just need a heatsink to sit under it.
So what switch do I buy, how many ports may I eventually need (4 at this time). The cheapest option is the Mercusys from Core Electronics.
Anyway, been an interesting exercise and expanded my knowledge.
Cheers
Jim
Edit: There is an alternative to the Hats, POE splitter. Adds clutter around the Pi but might be the best option if none of the POE boards will fit.
Just to add, when choosing POE hats or splitters, check the voltage and current ratings carefully to ensure stable Pi operation, especially with the Pi 5 which can have higher power spikes. Also, if using splitters, look for ones that provide clean 5V output with low ripple to avoid issues.
For your setup, a small POE switch like the Mercusys combined with quality splitters might actually be the most flexible approach if the hats don’t physically fit your current cooling and NVMe boards.
Finally, remember that running POE over longer cables can cause voltage drop, so keep cables as short as possible or consider switches with higher output voltage standards (802.3at or bt) if you plan longer runs.
Without test results from the manufacturer or an independant tester it is hard to determine if the POE splitter is any good. Manufacturer stating 5V 2.5A is all good but is it 5.0V or 5.2V or what. We know the Pi likes to have about 5.2V.
*** Buyer Beware: ***
It is worth noting not all splitters are created equal. Adafruit lists one that only does 100mbps, another is switchable 5/9/12V and 10/100mbps only. They can have Micro USB or USB-C or 2.1 DC barrel jack (12V). The UCTRONICS USB-C / Micro USB seems to be the best. But the claim of 3A seems a little high to me for such a small case.
Really only one way to see if these will work, buy and test. But waste of money it they don’t.
I think the Pi 5 set up for me is Waveshare POE Hat, Pimoroni NVMe Base
(goes under Pi), NVMe Base Case, Header to lift POE hat above Official Pi 5 cooler board, and of course a NVMe memory board. The Pimoroni NVMe Base allows all sizes of NVMe memory boards.
Raising the height means the case cover would no longer fit. But no probs, will use 3D printer to make a larger cover.
As to Pi 4B+ and Pi 3B+ unsure what to do at this stage, will keep checking. The Mercusys POE switch would do the job nicely. 7 POE ports, 1 normal port. Although the Jaycar Digitech version has 8 POE ports, and 2 normal ports, but almost twice the price.
Excellent points made, looks like you have a solid setup! It seems like your chosen case and components should handle the extra heat well.
I also agree that info on splitters can be hard to find or verify, but thankfully, forums like this can be a great resource to share real-world experience and help others avoid costly guesswork.
Purchased the following 3 items from Core Electronics, also a 5 port switch from Jaycar (4 ports POE), to test on Pi 5, Pi 4B+, and Pi 3B+.
Pi 5 Testing:
Purchased a Pimoroni NVMe Base for the Pi 5. The POE board mounts on header extensions allowing the Official cooler board to be used. (see pic)
BUT, telling the Pi to shutdown does not leave the Pi in shutdown mode; after a second or two it powers up again. This could be very annoying; the Pi will be on all the time so not really an issue for now with want I want to do.
Pi 4B+ Testing:
The UCTRONICS board with the fan can be installed very close to the processor, low profile leaves it lower than the ethernet and USB connections. BUT if you want other hats installed you will need to use header extensions and a heatsink on the processor. Interestingly this one will remain in shutdown mode, quite impressed with this UCTRONIC board.
I came across a Jeff Geerling video where he reviews some POE boards. He mentions the need for an isolation transformer on the POE board and suggests not to use boards that dont use an isolation transformer. One board he tested the manufacturer stated to remove 3 heatsink fins from the official cooler board to allow the POE board to fit. (really !!!). Another board left components touching each other when fitted to a Pi. The boards I purchased do not have isolation transformers.
I am in two minds about the need to use isolation transformers. The POE voltage is about 48V and would kill a Pi if it was somehow connected to the 5V rail; but then the POE boards are basically switch mode power supplies which should have normal protection. Hard to tell without a schematic though. We will see after the Pi 5 & Pi4B+ have been running for a while.
For now it has been pretty easy and removes the need for two plug packs in my situation.
Really impressive research and great attention to detail! You’ve clearly done your homework on the different PoE options and practical setup challenges. Thanks for sharing all this, it’s super helpful for anyone else tackling a similar project.
Posted these schematics as examples of using an isolation transformer and not using one.
DO NOT build these circuits.
Raspberry Pi POE schematic from link posted above. Very simple circuit. This would not be the current schematic. Note the isolation transformer for the 5V output.
From a document discussing POE for ESP32 micros. Very simple power supply circuit. The Sy8401 would have to fail in a big way to connect the ethernet DC voltage to the 5V rail, probably this is similar to how the POE devices I purchased work.
Link to a TI document that discusses POE in detail, as usual for TI documents.
It made me realise there also needs to be isolation of the DC from the signal on the ethernet connection to the Pi. I have not investigated how the Pi does this, just trust the Raspberry Pi corporation to have done it correctly.
Sorry to chime in so late in the discussion, but I wonder if James’ real goal is to understand POE, or to tidy up his power packs
I imagine that James has all 5 RasPis located close together, and those RasPi power supplies are notoriously too wide to all fit on one 6-way power board. I would certainly get frustrated at the space required for all those power supplies !
If James’ actual goal is simply wanting to replace 5 power packs (one for each RasPi) with one power supply with enough current to drive all 5 RasPis at the same time … something like Mean Well 70W 5V 14A Power Supply (sorry Core, but I didn’t find a comparable unit in your catalogue), or maybe an old PC’s ATX power supply should provide enough 5V current.
Of course James did start by stating he is Trying to understand POE, which is an admirable goal in itself.
James, are the Rapberry Pis at distributed locations, or all in one place ?
POE is most commonly used for cameras, which tend to be located where there is no handy power point. If you want a security camera under the eaves of your house, it could use wi-fi to send the image … but you need an electrician to install a power cable through the ceiling to the camera location. Or you can run an ethernet cable through the ceiling to the camera location and provide the power as well as ethernet communications through the same cable. The additional cost of the POE switch (or injector) and POE camera is offset by much better wired communications, and by running the ethernet cable yourself without needing to call out an electrician.
Currently using 4 port POE switch, Pi 4B+ and Pi5 connected. All in 19” rack with 3 NAS devices. Ran out of 240VAC sockets on power board with 10 sockets. Had to add another power board.
Saw a video by Jeff Geerling on Pi equipment and using POE. Wondered if the 4 Pi devices I had connected could use POE so began investigating. At first I had no idea how POE worked.
Yet to modify the Pi 3B+ weather station to use POE, and there is another Pi 5 intended to connect to POE. Yet to buy a POE board for that one.
At the moment all the sockets on the power board are used without the need for a second power board. In the final design there will be a Pi 3B+, Pi 4B+, and 2 x Pi 5’s on POE using all the POE ports of the switch.
So the original objective was to reduce the number of power sockets needed; and to get a good understanding of POE. I think I have achieved that.
I don’t think so, though you can certainly run out of wide power sockets, and space in your cabinet
I assume your Pis are each dedicated to a separate task, and so each is protected from any problem affecting any of the other machines.
There is also an argument that one server can run 5 Virtual Machines more efficiently than 5 separate computers. Back around 2000 IT departments were rushing to switch to VMs, and I even had a play with VMWare at the time, and was impressed.
I think the most significant disadvantages of RasPi are (1) its limited upgradability, (2) there aren’t so many apps available for the ARM CPU platform, and (3) cost of the higher-end RasPis - at least down here in Australia. A couple of years back I upgraded my HAOS from a RasPi to a VM running on a cheap ex-business PC running proxmox.
After running 3 Pi’s POE, all performing well with just an ethernet cable to each device.
The Waveshare board linked below initially caused the Pi to auto reboot after shutdown. I had another Waveshare board which worked correctly on the same Pi.
But, further investigation showed that when POWER_OFF_ON_HALT=0 in the “rpi-eeprom-config” it will remain shutdown and wont auto reboot. If POWER_OFF_ON_HALT=1 the amount of power drawn by the Pi in shutdown mode is reduced significantly but with the POE board it reboots, guess you cannot have everything.
I was going to get another board but this one now works ok. Not being able to shutdown the Pi is very annoying.
Regards
Jim
EDIT: I have two Waveshare POE boards, the one listed above needs POWER_OFF_ON_HALT=0, the other does not care. Weird.
