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.
Warning
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)
2. DC-DC buck converter (~$0.50) — look for Hesai brand on AliExpress, 12–24 V input, 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:
4. Heatshrink and connect — Cover the DC-DC converter in a heatshrink sleeve and connect 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:
