So I got the new raspberry pi 3 b+ and also bought the PoE switch to power it using Ethernet.


I don't know if I am doing something wrong, because it is not powering the pi. (you can ignore the white cable, it was there just because without it, the pi doesn't start) I hold the power button of the hat for a couple of seconds but nothing happens.

Do I need the PoE injector? https://uk.pi-supply.com/products/tp-link-poe-injector-tl-poe150s

Shouldn't the hat work directly just like it is using the normal Ethernet cable from my router?

I get Ethernet connection through the hat, but only if connected with power supply

enter image description here

  • how is the PoE hat powered? ... do you have a power supply? .... edit: i just read the rest of your question ... the PoE injector is the power supply
    – jsotola
    Commented Mar 16, 2018 at 17:18
  • but shouldn't the hat be powered with the Ethernet cable? So in the end I also need a power supply... portable or not?
    – blfuentes
    Commented Mar 16, 2018 at 17:22
  • I once accidentally fried a regulator on a HAT board designed to power the PI through the connector by plugging on the USB power instead of the HAT power. Did you initially try the board WITHOUT the usb power connected and only the POE connected? Do you have any other POE devices to verify that your injector is working?
    – crj11
    Commented Mar 16, 2018 at 17:33

3 Answers 3


you require the Poe injector

the PoE injector supplies around 50V into the cable, so you do not have run separate power to a device

it is useful for powering things like APs (access points) in a shopping mall where it would be a pain to run AC power into the ceiling where APs are usually mounted

enter image description here

  • So using just the Ethernet cable from my router is not enough...?
    – blfuentes
    Commented Mar 16, 2018 at 17:31
  • 2
    if the router has PoE capability, then you do not need a separate injector. but that would be a high end commercial router.
    – jsotola
    Commented Mar 16, 2018 at 17:33
  • There are some cheap(ish) PoE capable switches available, it doesn't have to be a high-end expensive enterprise switch. They are used for VoIP phones, security cameras etc...
    – njh
    Commented Dec 31, 2018 at 0:06

If you use an injector, you lose the ability to power-on a cold Pi. But if the Pi is connected either directly to a POE switch, or indirectly through a POE Splitter (described below), if you disable and re-enable the port on the switch, the Pi can be booted from a cold state. A few more elegant (and cheaper) POE options are:

Option 1 (in terms of lowest price): POE Splitter For £10 you can get this POE Splitter from Amazon.co.uk and it requires NO hat! Plug it on the far end of an Ethernet cable which is connected to a POE switch and your Pi boots. The monitor shown is a Pi touchscreen which makes the Splitter look large, but it has a small form factor.

Another benefit of the POE Splitter is that it leaves all your GPIO pins free as it moves the POE capabilities off of the Pi and puts it in front of the Pi.

POE Splitter

Option 2: POE Hat: Or, you can can spend £20 (inc VAT) and get a real POE hat- plug it into an Ethernet cable connected to your POE switch and the Pi powers on. I use this model and it works like a charm: I just plug it into my POE switch and the Pi lights up.


Both options work out of the box with no significant tinkering required. HTH- Terrence Houlahan


I read in the more info section here, :

Includes optional jumper that toggles the power functionality If you keep the jumper on, your Pi PoE will power on after holding the power > button for two seconds If you take the jumper off, your Pi PoE will power on as soon as you apply power from your injector

For it to work with the power button, as you're trying to do, the jumper must be on. Have you checked this?

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