Pi0/PiZ2 PoE hat (broken on day 1)

Hi Core crowd,

I bought a few of the PoE/USB hats for pi0, tested one quickly, and left it for a while. It was all working fine, powering a PiZ2 that I could see loading on a monitor.
When I came back maybe an hour later, I burnt myself grabbing it and checking with a thermal camera, I measured over 100C on the bottom of the PoE hat. So I unplugged it and waited over the weekend.
Later, it wouldn’t power up again.

So I tried, different PoE hats, different pi0 & piZ2, measuring voltages around.
All other PoE hats work perfectly.
All pis involved still work (no pi were harmed in the making of this debug)
The PoE injector still sends 50V to the broken PoE hat, but nothing comes out of the pogo pins for the pi

Any clue what went wrong?
This is an excellent product, and I wanted to use them for a massive project, but I can’t plan to use many of them if they can randomly break and turn off …

Did I involuntarily short-circuit it? Where could that happen?
I have thermal pictures if that helps. Now the working PoE hats run around 50C
Could it be a defective unit? What are the QCs on these products?
Any insight is welcome.

Thanks in advance

(ref: product wiki: PoE/ETH/USB HUB HAT - Waveshare Wiki)

1 Like

Hey Eric,

Sorry about the wait. Thanks for posting on the forum :slightly_smiling_face:

Unfortunately, I don’t have any of the Waveshare Pi Zero PoE HATs to be able to test locally to see whether there were any batch faults, but from what you’ve described it sounds like there may either be a solder bridge somewhere on the HAT from a manufacturing fault that didn’t get picked up by Waveshare’s QC, which is quite rare but can happen sometimes and cause a short which can lead to the result you’ve described.

The other potential issue that comes to mind is that the wiring being used is CAT2 or CAT1 and causing enough of a voltage drop that the power getting to the device wasn’t sufficient causing a further voltage drop and increase in current? Although this seems quite unlikely. Also being 802.3af compliant, you should be able to use any PoE+ or ++ switch with it with no problem, as the standards are intentionally designed to be reverse compatible.

It sounds like a hardware failure, I’ve sent you an email with more information. All the best with your project!


Thanks Bryce!
All other PoE hats seem OK, so I agree it can only be a hardware failure. I’m going to need 20 of those, so hopefully it’s a one in a million fault :laughing:

Pretty good product overall,