Is it possible to power the device without using the micro USB? For example, is it possible to use PoE (Power over Ethernet)?
Yes it is possible.
But not with PoE. The board can be powered using the GPIO. Here is a pin diagram showing the pins for power at the top.
Maximum permitted current draw from the 3v3 pin is 50mA.
Maximum permitted current draw from the 5v pin is the USB input current (usually 1A) minus any current draw from the rest of the board.
Model A: 1000mA - 500mA -> max power draw: 500mA
Model B: 1000mA - 700mA -> max power draw: 300mA
You can read more on elinux.
The Ethernet port does not support PoE. Therefore, you cannot use PoE without external hardware; it would be necessary to convert the 48V down to 5V. It should limit the current to 1A.
Untested (Possibly) Useful Hardware
It doesn't support IEEE 802.3af standard PoE. But PoE is the CONCEPT of running the voltage over the unused (or overvolting the USED) DC wires on the Cat5 cable. (Blue and brown/blue+white and brown+white). And the Raspberry Pi CAN be modified to do this...
I imagine it can be wired over Cat5/Cat6. But need to make sure after the DC is taken to power the Pi that you're not overvolting the RJ45.
(3.3v actually I think for Raspberry) - and for PoE, you can use blue wires or brown depending on your design. (IEEE 802.3af is DC+ on pins 4,5 and DC- on 7,8). If you didn't know you can connect a Cat5 cable, strip it. Cut the blue and brown wires, and it will still work. You can use this princple to wire the DC over those wires, and take it off before it enters the 8p8c modular plug, or before it hits the pcb after the plug.
I'd build my own injector too btw.
As others have said you can power the Pi by feeding 5V into P1-2 and ground to P1-6. I've done so for several years using a UBEC. You do bypass the polyfuse and any protection that might give (not much in my opinion). You should not feed in 3V3 as the Pi's 3V3 (and lower voltages) are derived from the 5V line.
If you want a Raspberry Pi PoE solution that conforms to IEEE 802.3af Standard (PoE), then try the Xtronix Raspberry Pi interface. It is not cheap, but it allows the Pi to be powered via the ethernet cable from a standard PoE hub/switch. The IEEE 802.3af PoE standard defines how devices can be powered over the CAT 5 Ethernet cable.One of the issues the standard addresses is that of safety. A hub/switch that meets the standard allows Poe and non-Poe devices to be mixed safely in the network. Hope this is of help - Regards Jim
It is in fact possible to power the Pi via PoE using a PoE Splitter: £9.90 inc VAT from Amazon for the GB speed model. The data is piped through the Ethernet cable on the device and power from the switch is diverted to the MicroUSB cable attached to it which powers the Pi. So yes, can power the Pi via PoE, but via the standard Power socket on the Pi. You can also of course use a PoE Hat but if you need to use another hat, things start getting ugly ;-)
The POE switch I use with my the POE Splitter is a ZyXEL_GS1900-8HP-GB0102F, currently £88.35 ex-VAT from Amazon. By enabling and disabling the port the POE-powered Pi is connected to I can remotely start a Pi which is in a down-state (either not booted or shutdown using
sudo systemctl poweroff ). This is a really great switch with a lot of bells & whistles for a very reasonable price. Even has SNMP and IPv6 support.
Practically speaking maybe not, I did the following and RPI Model B did not work.
I connected 5V from a USB to Pin 2 and GND to pin 6 for Model B RPi. The power LED lit RED, Act lit slow blinking green.
Other LEDs were off.
I could not connect to the RPi over the Ethernet. Removed the connects and powered through Micro USB and RPi worked as expected.
I did NOT connect 3v3 since I do not have access to 3.3V.