Good they to all devs or people with raspberry pi 3 b+ have you noticce the 4 POE pins in the board near the 4 usb ports? what is the purpose of that 4 pins?

can I use that pin to power up my 5v DC fan? if yes how the ground and 5v connecction? or what is the real use of that pins I believe that they put it there for reason thanks for the comments highly appreciated.

  • 1
    those 4 pins connect to the ethernet port, 1 pin for each "pair" in the ethernet cable. The voltage across those pins (don't know which ones to be honest, you'd have to look up the PoE spec and which pin connects to which ehternet pair) is 37 to 57 volts ... so, no, you can't use those pins to power up a 5 volt fan - but, you're not likely going to have any voltage there, unless your pi is connected to a PoE switch anyway Jun 8, 2018 at 0:30
  • I'll answer to either sir or mam, but sir is correct :p Jun 8, 2018 at 6:26

2 Answers 2


The Raspberry Pi foundation plans to release a PoE HAT, which will be an add-on board to be stacked on top of the Raspberry Pi. That HAT will transform the rather high PoE voltage into the 5V the Raspberry Pi needs and eliminate the need for any other cables and a power supply.


If you take a look at the schematics, those 4 pins are used to feed the Ethernet power signal from the Ethernet port to the PoE Hat to the.

EDIT: As @JaromandaX points out I was looking at the schematics the wrong way. Those four pins are used to (of course) transfer the power and not the data to the hat.

  • You never get 1Gbps on Gigabit Ethernet over USB 2.0. Its maximum throughput is 300 Mbps.
    – Ingo
    Jun 7, 2018 at 23:49
  • @Ingo of course you never will get 1Gbps. But it is gigabit Ethernet protocol wise.
    – kwasmich
    Jun 8, 2018 at 6:27

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