Review: Raspberry Pi's new PoE+ HAT

the poe plus hat powers your raspberry pi 3b plus or 4 model b over a single ethernet cable meaning you can ditch the usbc power adapter if you have the right network setup unfortunately i can't recommend this new version of the hat for most users at least not this first version and i'll tell you why as we test everything later in this video but first why is poe so special if you have a poe network switch or injector you can do things like run a raspberry pi powered camera far away from an electrical outlet or use pies for industrial automation where you just have a network cable run to each pie in your factory or warehouse or if you're me you can run a rack of raspberry pi's just using one poe switch and plugged into a ups and get networking and battery backup through a single cable but why the new hat and what's with the plus well let's dig into the history of the poe hat and why there's a new plus version before we dig in i wanted to give a quick thanks to volker de boissignier for his sponsorship on github and he asked if i could also give a special call out to fronix a site that's now 17 years old and my most trusted source for testing and benchmarking so much in the linux and open source community people like me and michael from pharonix need your support to keep doing what we do so please consider sponsoring my work using the links in the description and also go check out and consider subscribing to pharonix there's a link for that too now back to the video in 2018 the pi foundation introduced the poe hat for the pi 3b plus that initial version had a fatal flaw on many pie boards it could only supply about 200 milliwatts of power to usb before the current limiter reset martin rowan first documented how plugging in almost anything besides a keyboard and mouse would trigger the pi's over current protection and switch off the usb ports so the pi foundation refunded or replaced all the first version poe hats with a new revision the new hat has a mezzanine board that patches over the problem and i've been running these boards for years without a problem the power issues were solved completely for the pi 3b plus but after the pi 4 came out people started plugging in more power hungry devices like usb3 ssds and the pi's internals could draw even more power this exposed a new problem the poe hat just can't put through all the power of fully loaded pi 4 needs and that's because the first poe hat used the 802.3 af standard it only guarantees up to about 13 watts of power for a powered device like the raspberry pi most simple poe devices like ip phones and security cameras are happy using less than 13 watts but the pi 4 is a decent general purpose computer and people do a lot of crazy things with them like overclock the cpu plug in a display and plug in multiple ssds devices like ssds consume around three watts each and two of them together would be six watts according to the pi documentation the pi 4 itself minus the usb usage should have 9 watts available to it for stable operation if you do the math 3 plus 3 plus 9 equals 15 which is more than poe can guarantee and doesn't even include the overhead of the poe hat's own power draw and looking back at that power supply documentation again the recommended psu current capacity is 3 amps for the pi4 model b basic poe can't supply more than 13 watts or 2.6 amps total at 5 volts so we're in a bit of a pickle now i currently have a number of pi4s using the original poe hat and they've been online for years without a problem but i don't overclock them and i don't have anything plugged in via usb so i'm well within the power requirements but taking all that into account the pi foundation just announced a new poe plus hat and that plus isn't just a marketing term it refers to the fact that the new version of the hat supports 802.380 which is known as poe plus it's still backwards compatible so it can work with older poe switches but if you have a newer poe plus switch you can get about 25 watts through the new hat that means you could pump five amps of power into the pi through poe plus now before you get all excited you have to make sure you have a poe plus switch or injector a lot of cheaper or older poe devices only support the older af standards so you'd still only get 13 watts lucky for me i do have a poe plus switch handy thanks to a fan of the channel who sent me this really nice hp enterprise switch and this switch even offers a web ui where i can check power consumption per port and if i glance at the two pies i'm currently powering with the original hats i can see they're using about three to four watts each which is well under the hats maximum but how about the new hat it provides more power but what are the hardware differences well for starters the new hat has this ideal diode rectifier which replaces a slightly less efficient part from the original hat the pi foundation's blog post has a thermal image showing heat dissipation under a 2.5 amp load and in my testing the board actually seemed to be slightly cooler than that but still pretty hot the second big difference is this flat transformer the old hat used a traditional wire around a magnet transformer but this new one is called a planar transformer this transformer kind of turns things inside out since it has a spiral of circuit traces for a winding and a flat magnet goes around the whole pcb and because the pcb traces are flat and more precise than copper wire windings they're slightly more efficient at dissipating heat plus the whole transformer package can be a tiny bit shorter the fan is also different the old hat used a two pin soon on 10 000 rpm fan while the new one has a 3 pin at a 12 000 rpm fan almost identical to the case fan introduced a few months ago the big question i have is whether the new fan sounds any better than the original hats fan let's mount it up and find out the m 2.5 mounting hardware is the same you get with the original hat i'm using some of my own 12 millimeter screws to mount the pie to my rack tray though now there's one thing that's a bit concerning right out of the box the screw that's pre-installed on the fan here is actually too long to fit correctly it's a 12 millimeter screw and when you put on the hat the screw pushes against the camera connector i could ignore it and live with a little board flex or not tighten the screws all the way or i could replace the screw with a 10 millimeter screw but i don't have one on hand and technically i could reverse the screw and have a little jagged end sticking out at the top but then it doesn't slide into my rack as nicely so i handed it off to redshirt jeff and he took care of the problem for me wait what i told him to take the screw off before he cut it i don't think he's ever going to learn anyways i'm not sure how that passed the board's qa hopefully newer batches switched to shorter screws so this isn't a problem and this doesn't matter to me so much but the new hat doesn't even fit in the official pi4 case i never use the hat in any enclosed case though so for me it's not really an issue but it is a little annoying that the old hat did fit while the new one doesn't another thing i disliked about the original hath design and it's the same on the new hat is the fragile surface mount socket used for the poe header connection here i've had to resolder it on two of my original hats because when you pry the hat off the pie it can get yanked off the tiny solder joints most of the time though people just stick the hat on and it never gets removed so it's really a minor annoyance alright so i have it all put together now let's turn it on and check how it performs first of all i noticed when the fan is going full blast it gets even louder than the old hat the new fan pushes through 2.4 cubic feet per minute compared to the older hats 2.2 cfm so the increased noise does also pair with slightly more cooling for comparison here's what the older hat sounds like at full blast the new fan gets up to 54 decibels at close range compared to the old fan at 45 that's a pretty significant difference and you'll definitely notice it if you're in the same room as the fan but i do like how quiet the new fan is at low speed though if you tweak the fan temperature settings like i mentioned in a blog post linked in the description you can get a much more pleasant fan experience here are both poe hat fans at the lowest speed first the new poe plus hat and then the poe hat if you have your pie stowed away in a rack or closet it's not a huge issue either way but if you're going to be near it both fans get to be a bit annoying at full blast i found out you can get the current the pi is consuming using this command it gives the current in microamps so converting that to amps it says the pi is using around half an amp at a nominal of 5 volts that means the pi is using a little under 3 watts at idle that's pretty typical but what's not typical is how much power the new poe plus hat uses by itself checking on my enterprise grade poe switch i saw the port with the new poe plus hat using almost 6 watts so it doubles the idle power consumption of the pi what about the original hat well i configured the exact same pi with the exact same microsd card and the exact same port on the switch and tried two other ports too to make sure it's not a fluke and the original peewee hat only used about 4.1 watts at idle for the pi plus the hat this means the poe plus hat consumes around 60 to 70 percent more power by itself than the old poe hat if your pi is running full blast with usb devices plugged in the difference isn't quite as dramatic but if you're like me and you have some pies running lightweight utilities like a web server or monitoring utilities doubling the idle power consumption isn't exactly ideal even with the pi shut down the old hat consumed 2.6 watts and the new one consumes 4.8 watts that's a pretty significant amount of power going to waste almost twice as much as the original poe hat i was also excited to really stress test the new hat so i overclocked the pi cpu to 2 gigahertz plugged in two ssds and set up a stress test i ran stress ng on all four cpu cores ran iperf 3 network traffic benchmarks and wrote data to both ssds simultaneously the first time i ran the test i was able to do it all and it worked for a few minutes before i stopped it the maximum current draw on the pi itself was 11.2 watts while the poe switch was telling me the whole system was pulling over 14 watts but i tried running the test a few more times and every time the pi would reset itself after a few seconds at full blast here's what that sounds like now the same thing happened when i powered the pi via usbc so the moral of this story is if you're going to be running high-powered usb devices use a powered usb hub and don't plug them into the pi 4 directly the pi4's usb ports can only supply a maximum of 1.2 amps no matter how much power the pi itself gets speaking of usb some people ask if it's possible to power the pi via usbc instead of over ethernet while the hat is attached so i plugged in usb-c power with the hat attached and everything seemed to work just as well at least without any hard drives plugged in i did notice there was still power flowing through the poe plus hat and i measured over 60 volts across these two leads there's an ethernet cable plugged in here but that cable is plugged into a regular switch and it didn't blow it up so i guess the power's not going through ethernet at the same time i was doing this research i found martin rowan's blog post about the new hat and saw this video clip i was wondering why his pie had that horrible sound but mine didn't well it turns out i just needed to plug in my hard drive the sound that came out of my pie was ear grating i have a link to martin's blog post below so check out his investigation too hopefully this coil wine or whatever it is doesn't indicate a deeper issue i haven't really had time to dig in too deep but it's really unpleasant to hear it in person so usbc power does work but if you're not going to power the pi through ethernet maybe take off the hat after all this testing i have to say i can't recommend the new poe plus hat yet some people like overclockers who have multiple usb devices plugged in might benefit from a little extra power i mean the older poe hat couldn't even run half my stress test but for most people the original poe hat seems like a better option you'll save energy and have a product that fits the pi 4 model b out of the box without any modifications both of them are 20 bucks so price doesn't make a difference and you can also find other poe hat options for the pie too but be careful with some of the cheaper options since they lack protections that could kill your pie or the switch it's plugged into in the end i find it slightly ironic that james adams said in the 2018 post announcing the original poe hats revision and i quote it's embarrassing to have released a product with a bug like this but it's a lesson well learned and will be improving our internal processes to prevent a recurrence there are definitely similar teething problems with this next gen poe plus hat and hopefully qa for the next board's launch is better i should note that i was never contacted about the poe plus board prior to its release nor was martin who first identified some of those original poe hat problems and i'm not sure how many people outside the pi foundation tested it before release a wider real world testing program would have probably identified these issues hey it's jeff so this is the morning that i'm posting this video and i actually just got a response back from the raspberry pi foundation to an email that i sent with some of the questions that i had after making this video and i wanted to mention them here just because i think that'll head off some questions about it first of all with usbc the back power issue shouldn't cause any problems but apparently it's not a supported use case according to the pi foundation that's not mentioned right now in the documentation so hopefully they they can add that in but if you're going to power it from usbc like i said earlier pop off the hat also they did mention that the new hat does use more power they they said that that is the case especially if the poe power supplier using is close to 50 volts and if you need to use less power their recommendation was sticking with the original poe hat so for me like i said earlier i think that's the better option and for a lot of people that are using the pi not to do overclocking or have lots of usb devices plugged in it might still be the best option also i mentioned the fan noise and they said that the new fan does have also a longer lifetime and it's rated for higher temperatures so the bearings that it has are a little bit louder at full blast but like i mentioned it is actually quieter at the low setting which is nice so in the end even with that new information i'm going to stick by my findings and my recommendation but this got me thinking that maybe the hat would be perfect for like a pi 4 b plus revision that that lifted the usb current or had a higher clock speed or maybe even a pi 5 someday and i don't have any idea if either of those things are actually going to happen so that's just my speculation but it seems like the poe plus hat is unnecessary overkill for a lot of the raspberry pi 4 use cases anyways back to the pre-recorded video i'll dive more into power over ethernet in general in a future video so make sure you're subscribed in the meantime check out some of the videos and resources linked below until next time i'm jeff gearling and more precise flat apparently i'm still going through puberty that was not the best way to do that so i'm going to try it again some people asked if it's power if it ah i sure plugged in that power there's an ethernet cable plugged in here but that's ah crud there's an ethernet cable plugged in in this little clip but moral of the story don't just start ad-libbing in the middle of a sentence that i wrote out already but for most people the original pewee somebody just texted me i finally got that paragraph and then dhl texts me

Channel: Jeff Geerling

Views: 157,074

Rating: 4.9480247 out of 5

Keywords: raspberry pi, poe, power over ethernet, poe+, 802.3af, 802.3at, power, usb-c, plug, ethernet, network, networking, problems, broken, fault, blog, hat, poe hat, poe+ hat, terrible, review, red shirt jeff, cisco, trendnet, hp, aruba, switch, router, screw, too long, coil whine, transformer, planar, coil, ideal diode, rectifier, circuit, computer, computers, pi, pi foundation

Id: XZ08QKAbBoU

Length: 16min 3sec (963 seconds)

Published: Thu Jun 17 2021