Document how to use the PoE HAT

[geerlingguy]

I just bought four Raspberry Pi PoE HATs, and I'm trying to incorporate them into the cluster... but there are two issues I'm running into currently:

1. They come with female-to-female 9mm M2.5 spacers that need to be precisely this height so the contact can be made with the GPIO port and the PoE header. So I can't physically screw the Pi into the bone-style clear case using it's screws and have the HAT on top of those screws.
   • To fix this issue, I'm going to order 24 of these aluminum 9mm M2.5 female/male spacers and see if they solve the issue.
2. I can no longer attach my little RGB LED board to the GPIO, especially considering the now-even-more-limited vertical clearance with the Pi and the HAT.
   • I could maybe buy GPIO headers like this 11mm female GPIO header and stack the RGB LED board on top of the PoE HAT... we'll see. I might have to forego the GPIO-controlled LEDs for the time being.
   • Look at this PoE header tutorial/overview post for more tips—if I do end up stacking headers, I will need more vertical clearance (so new standoffs for the entire cluster), and I will need 15mm M2.5 female/male spacers... instead of the 9mm ones I just ordered. Go figure :P

[geerlingguy]

Testing the first HAT on my top Pi, since I can't put them all on and still mount them in the rack... so far it works great. But no LED for now, and that makes me sad :(

Maybe I could make a super trim board and just extend some of the pins (and trim the rest?) custom-printed? I don't have an etcher and don't want to try to DIY it if I don't have to.

The lengths I'm going to just get 5 fewer cables and one fewer power supply...

[geerlingguy]

One thing to mention in setup: all my HATs came with a little anti-static sticker over the 4x4 PoE female header. I had to remove that little sticker before I could install the HAT on the Pi.

[geerlingguy]

I have the HATs all working now. Interestingly, the temperature-controlled fan seems to work even after shutdown... at least AFAICT.

[geerlingguy]

Nevermind, that Pi just hadn't actually shut down all the way yet.

I am noticing a bit of coil whine when the Pis are shut down. It's loud enough that it's a bit of an annoyance.

[poon64]

Just saw that there is another model of the PiPoE that has pass-through of the GPIO.

[geerlingguy]

@poon64 - ooh, that does look nice. I'm full-bore ahead with the Blinksticks for now, though, and may revisit the PoE HAT later... we'll see. For now I can live with the coil whine. One thing that is a bit annoying (even if it does help overall with CPU) is that the fans are almost constantly running (at least one of them is), and they are pretty darn loud. So not super fun to have sitting in my office right next to me. I'm considering unplugging them and letting the CPUs bake a little.

[geerlingguy]

Just a quick note—while I was disassembling the Pi 3 model B+ edition of the cluster, the first PoE HAT I removed had its PoE header separated on one side as it's kind of a tricky maneuver to separate it from the main Pi board.

So for the rest of the Pis I used a small screwdriver and slowly pried the GPIO pin areas up and down the board so the pins on the PoE header would not be wrenched in a funny way.

I had to go re-solder the joints and clamp down the tiny PoE header using a wrench!

[ndom91]

Im about to go ahead and build this myself. Quick question regarding the PoE hats.

Is using the 9mm aluminum spacers you linked above enough clearance to operate the fans of the PoE hats when the Pis are setup in the typical cluster stack?

Could you also possibly link which "case" / acrylic base you used for this specifically?

Thanks so much!

[shailensukul]

The PoE Hat here says it is only compatible with the Pi 3B+:

Compatible only with Raspberry Pi 3 B+ that has PoE pins

Has anyone been able to install with the Pi 4B ?
TIA

[JJJ]

There are several different PoE hats floating around, some masquerading as if they are official, but in my experience, 2 different ones have worked for me on 2 4Gb Pi 4’s.

[shailensukul]

Found a supported one here

[geerlingguy]

@shailensukul - I am using the official Pi PoE HAT without issue on all my Pi 4s. See the official product page: https://www.raspberrypi.org/products/poe-hat/