Official Raspberry Pi PoE+ HAT shorts out on Pi 3B+

Hi Everyone,

Has anyone successfully managed to use an official Raspberry Pi PoE+ HAT on a Pi 3B+ ? Apparently they are compatible however at least one capacitor is going to short out on the HDMI connector if the 3 PoE+ HAT’s I’ve got are anything to go by. I could put a couple of layers of insulating tape over the HDMI connector but this seems like an accident waiting to happen - I am wondering if I have a few rogue HATs with the wrong profile capacitors on them:

What do we think about this ?

Maybe use taller standoffs?

and if you dont have a taller standoff ,remove hat and put nut on the standoff to give a bit more hight ;)

Surely the issue here is that the description for this hat states that it is compatible with the 3B+ and doesn’t mention anything about having to take precautions to make it safe. I wonder how many people would just stick the HAT on and power it up releasing the magic smoke.

I am trying to find out if there is a manufacturing issue with the HATs I’ve got or if the QA during product development was so poor that no-one spotted this. They missed the screw that fouls on the camera cable connector and how it back powers if powered by the USB port so I guess it’s possible they didn’t check the keep-out area of the larger HDMI connector used on an earlier board.

Incidentally, if I change the height of the HAT they won’t fit in the cases properly that I bought specifically for the purpose. I am not so worried about that because I can use something else, but guys - the problem here is that components on the underside of the board short out on the HDMI connector ! That’s not compatible in my book. Perhaps they’ve sold so few of these (or sold them all to real engineers who check their work) that no-one has genuinely ever put one on a 3B+. My point is that you can damage your kit if you fit one of these PoE+ HATs to a 3B+ which is claimed to be compatible if mine are anything to go by.

Has anyone here used one of these HATs on a 3B+ without having to make it safe to do so first ?

Wrong forum, IMHO. Pimoroni don’t make it they are just a reseller. The onus is on you to make sure its installed with the correct suitable mounting hardware.

Buy a PoE+ HAT – Raspberry Pi

  • Before installing the PoE+ HAT, you must attach the supplied spacers in the four corners of the board

Raspberry Pi Forums - Index page
HATs and other add-ons - Raspberry Pi Forums

This is a good point, one of the commentors on Discord has observed that I am using the standoffs supplied with the case and not the ones supplied with the HAT. It is quite possible that the original metal standoffs are longer than those supplied with the case. I had not considered this.

I am not in a position to check this now but I will do so - it would certainly be interesting if the problem was caused by the case designer shaving a couple of milimetres off of the height when they should not have done.

Once I have had the opportunity to check this I will report back should this help anyone else in future (and I’ll also mention it to the dealer who supplied the case).

Thanks everyone.

The length varies from vendor to vendor. Adafruit have 11mm and tall 16mm standoffs. The Pimoroni ones are a slightly shorter 10mm.

That’s interesting to know. I did check this yesterday and the standoffs supplied with the PoE+ HAT are 9mm but it requires 10mm to stop the capacitor on the underside of the HAT from shorting out on the 3B+'s HDMI connector. You could get away with the 9mm standoff if you put some insulating tape on the HDMI connector but that runs the risk of it unsticking (these things run pretty hot) so long as you don’t tighten up the fixings properly as this adds a little flex to the board.

The case I wanted to use doesn’t have a lot of tolerance in it when it comes to messing around with standoff / pillar sizes but I have an assortment of sizes and by losing a millimeter here and gaining on there I managed to get it to fit. If you don’t want to go through this yourself I can suggest that these cases accept the PoE+ hat with no serious modifications (although for the Pi 3 case below I did drill a few holes in the lid and shaved 2 degrees off the average temperature):

Pi 3 PoE compatible case:

Pi 4 case (I went with these in the end for my Pi 4 and works very well minus the supplied fan and heatsinks - note that the Pi 3 variant which looks the same requires cutting and filing to make it fit due to unnecessary plastic inside):

… and with the lid on:

A few extra alterations might possibly be to use Kapton tape over the HDMI socket - it’s thinner, heatproof and stronger than electrical insulation tape, replace the cheese/round head fan screws with countersunk screws for a bit more headroom in the case and to tweak the stand-off height use some of those fibre washers typically used for PC motherboard mounting.
Additionally, albeit possibly warranty-breaking, I snip off protruding component legs from PCBs and then sometimes resolder the joints to make a nice smooth solderball making it less likeky to draw blood when manhandling.
OK perhaps it shouldn’t need any alterations straight out of the factory but sometimes it just makes your life easier to bring it up to your own requirements or standards if simple tweaks can be applied (assuming you’ve tested it first before modding).

I’ve been buying these kits.
Black Nylon Machine Screw and Stand-off Set – M2.5 Thread : ID 3299 : $16.95 : Adafruit Industries, Unique & fun DIY electronics and kits
I have a lot of builds with stacked Hats and pHats. I tend to use a lot of the ones with the threaded stud on one end.