Wednesday, September 25, 2019

Poor man's PoE for Raspberry pi-3/4 under ~$2


Warning: This blog is about powering your raspberry pi-3/4 over ethernet cable(length upto 100Meters), It uses Passive PoE mechanism where T568b wire color 
Blue/Blue-White ==> +(positive) terminal of DC supply
Brown-White/Brown ==> -(negetive) terminal of DC supply

If you dont know what is a passive PoE, then dont proceed!!!, instead buy a proper PoE Hat for Raspberry pi-3.

If you are a tinkerer/hw-enthusiest/diy-hobbyist(and you know what you are doing), here is what you need,

1)PoE Injector cable(costs less than 80cents)



2)DC-DC buck converter from aliexpress that costs less than 50cents(Look for Hesai brand, 12v-24v input and 5V/3A Output).


3)female-to-female jumper wire(cut into 4 pieces) and solder as shown in the picture



4)Cover DC-DC converter in a heatshrink sleev, and connect to raspi-3 as shown.

5)Feed 12v-DC and  Network-connection to the PoE Injector and connect CAT-5 cable(upto 100m) between Injector cable and Raspberry-Pi-3 as shown below



4 comments:

Linker3000 said...

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...

Anonymous said...

Reference was truncated - try:

https://raspberrypi.stackexchange.com/questions/43285/raspberry-pi-3-vs-pi-2-power-consumption-and-heat-dissipation

NickG said...

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

ADAV said...

Thanks NickG for the hint, i will update this blog.