How to power a Raspberry Pi 3/4 over an Ethernet cable (up to 100 m) using passive PoE — with off-the-shelf parts costing under ~$2.
Complete setup — Raspberry Pi powered over Ethernet via passive PoE.
Warning: This uses passive PoE with T568B wiring:
- Blue / Blue-White → + (positive) terminal of DC supply
- Brown-White / Brown → − (negative) terminal of DC supply
If you don't know what passive PoE is, do not proceed — buy a proper PoE HAT instead.
Parts needed
1. PoE injector cable (~$0.80)
PoE injector cable — splits power and data onto the Ethernet cable.
Connector detail of the PoE injector cable.
Wiring detail of the PoE injector cable.
2. DC-DC buck converter (~$0.50) — look for Hesai brand on AliExpress, 12–24 V input, 5 V / 3 A output.
DC-DC buck converter — 12–24 V input to 5 V / 3 A output.
Assembly
3. Solder jumper wires — Cut female-to-female jumper wire into 4 pieces and solder to the buck converter as shown:
Jumper wires soldered to the DC-DC buck converter.
Wiring diagram — connecting the buck converter to the PoE splitter.
4. Heatshrink and connect — Cover the DC-DC converter in a heatshrink sleeve and connect to the Raspberry Pi:
DC-DC converter in heatshrink sleeve, connected to the Raspberry Pi.
5. Final setup — Feed 12 V DC and network into the PoE injector, then run a CAT-5 cable (up to 100 m) between the injector and the Raspberry Pi:
Complete setup — 12 V DC + network through PoE injector to Raspberry Pi over CAT-5.
7 comments:
Using a 1N4148 diode for reverse polarity protection might be a bit under-specced: the Pi-3 + peripherals can draw something near 800mA under heavy load and the 1N4148 is rated at 300mA max continuous current, 500mA max repetitive peak. Something like a 1N5817/1N5819 schottky diode would be better - and maybe a 3A 1N5822 if there's any power-hungry USB peripherals. That buck converter claims to be good up to 3A.
Ref: https://raspberrypi.stackexchange.com/questions/43285/raspbe...
Reference was truncated - try:
https://raspberrypi.stackexchange.com/questions/43285/raspberry-pi-3-vs-pi-2-power-consumption-and-heat-dissipation
Instead of soldering 9v then adjusting the pot, use the pcb/module as it was meant to be used. Cut the ADJ trace and solder the 5v.
See the picture here https://www.electronics.com.bd/image/cache/catalog/module/new/Mini-DC-DC-12-24V-To-5V-3A-Step-Down-Power-Supply-Module-Voltage-Buck1-1000x1000.jpg
Alternative instructions here https://i.pinimg.com/originals/e5/30/a7/e530a729067f0bd997f077ff53729f5f.jpg
Thanks NickG for the hint, i will update this blog.
Nice scheme, I'll try to create something similar
Hi thank you for the guide. I followed it religiously only to get to the last step where I opened up the case for my RPI3 model B v 1.2 and found out I did not have the PoE pins required.
Turns out this capability was only added in the RPI3 model B+ (https://www.rs-online.com/designspark/raspberry-pi-3-model-b-vs-3-model-b).
Still I got to learn a few things on the way and get frustrated at my soldering skills :)
This waas great to read
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