Step 1: About Power over Ethernet
- supplying 5V directly at one end of the cable means the Pi would get less than 5V, due to the resistance in the cable. This would make the Pi less reliable as the cable got longer.
- the current in the cable is less, meaning that less electrical power is wasted.
- the step-down regulator provides (some) protection for the Pi if the cable is mis-connected.
Step 2: You will need...
- A DC power supply - any voltage between 12V and 24V, regulated or unregulated, will do. In my tests, powering a Raspberry Pi used under 200mA at 15V, so make sure the supply is rated at least 250mA (at 15V) or 300mA (at 12V) for each Pi you will be powering.
- A passive PoE injector box. The one in the pictures was £7 on Amazon for a 4-port one - many other types are available.
- A short length of CAT5 cable with a RJ45 plug attached. (I cut the end off a short Ethernet patch lead where the plug on the other end had broken).
- A DC-DC step down converter module. (Search for 'LM2596' on Amazon or eBay - the one shown in the pictures was about £2).
- A PCB-mounting RJ45 socket.
- A two-pin 0.1" pitch socket (for a Raspberry Pi), or DC jack plug (for Beaglebone)
- A small piece of prototyping pad board. (Note this has to be pad board not strip board).
- Wire, cable ties
- Fine-tipped soldering iron + solder
- Wire cutters, strippers, pliers, etc.
- A multimeter
- A drill with small (1mm) bits - a Dremel is ideal
- Optional: a network cable tester(see photo)
Step 3: Solder in the RJ45 socket
Step 4: Wire up the DC-DC converter
- connect the board to the PoE injector unit using a short RJ45 cable (make sure it's not a 'crossover' cable)
- check that the -V on the converter module is connected to the -V or ground on the injector's input socket
- check that the +V on the converter is connected to +V on the injector
- check for short circuits between the +V and -V on the converter
Step 5: Wire up the Ethernet connection
- Pin 1 - white + orange stripe
- Pin 2 - orange
- Pin 3 - white + green stripe
- Pin 6 - green