Power Over Ethernet (POE) is a way to power the Pi4 using its ethernet port, making it easier to supply power and network connectivity through a single cable. This is useful when the Pi4 needs to be installed in positions away from power sockets and wifi such as for CCTV installations where a camera module needing power and fast networking is used.
This project uses the official POE Hat which is a low-profile add-on board that attaches to the GPIO header connector on the Pi4. It includes an integrated cooling fan and the whole unit fits neatly inside the OKdo metal case for a compact installation.
POE uses standard Cat5 ethernet cables, but you do need a POE network or you can use a POE injector module. This adds power to an existing standard network connection which is the approach taken by this project. In this way, POE can be used on any Office or Home network.
- Start by attaching the Pi4 to the OKdo case using the 4 screws provided. Then screw the metal standoffs to the bottom of the POE Hat.
Do not fit the heatsinks supplied in the OKdo kit to the Pi4 as these will bind with the components on the POE Hat. The fan supplied with the OKdo kit should not be fitted either. The POE Hat has its own temperature-controlled fan which only runs when the CPU temperature exceeds 50° C.
- Slide the POE Hat under the case fan support and rotate it into position over the GPIO header and separate 4-pin connector. Make sure all the connector pins are aligned before applying light pressure to snap the board into place.
- Fit the case lid by sliding the tab with the blind nut carefully between the POE hat and the base of the case. You may need to lift the edge of the POE slightly. Clip it into position and screw in the retaining screw.
- Power is injected into the network node using a dedicated POE injector module. This needs to be powered from the mains using a power cable which is not supplied with the injector. The unit has two ethernet connections, one for connecting it to a router or switch (labelled IN) and the other to connect the injector to the Pi4 (labelled OUT).
- There are different POE standards, the POE Hat requires power sourcing equipment that conforms with POE 802.3af. This standard can detect that the Pi4 is attached and supply the correct amount of power.
- Make the connections but Do Not power on yet.
- Because it’s common to use POE devices without a monitor and keyboard attached, this project uses Raspbian Lite for its operating system. This requires an 8 or 16MB SD card and the card reader supplied with the OKdo kit.
- On the PC download the Official Raspbian Buster Lite image from here.
The POE Hat no longer requires a firmware upgrade for the Pi4. It works with the standard Raspbian images out of the box.
- Use Balena Etcher which is a free app on Windows 10 or Mac OS to flash the downloaded image to the SD card. You can get it here.
- Follow the onscreen instructions and when the process has finished, eject the SD card from the PC.
- Re-insert the SD card in the PC card reader again and navigate to the boot drive. Create a new file named “ssh” in lower case and without any extension.
This is a special file that the Pi4 will find when it boots that will allow a remote login from an SSH client running on another PC.
- Eject the SD card from the PC card reader and insert it in the card slot of the Pi4.
- Switch on the POE injector, the Pi4 should power on and boot.
Windows 10 and Mac OS both have SSH clients built-in. These can be used to access the Pi4 securely via SSH from another computer on the same network.
- Open a Command / Terminal window on the PC and type the following command using the default username “pi” and password “raspberry”:
After allowing the SSH fingerprint to be added, you should now be logged into your Pi4 via SSH.
You can configure the Pi4 to change the password, network hostname and update to the latest version of software by using “raspi-config”.
- Type the following command to run it:
Raspbian Lite comes with hundreds of useful packages already installed. If you need any extra ones, add them with the “apt” command:
sudo apt install
Before removing power it’s important to safely shutdown the operating system. Do this by running the “poweroff” command. This will protect your SD card from corruption:
- Once the yellow activity LED next to the red power LED on the Pi4 has stopped flashing it’s safe to remove the power.
- Switch off the POE injector or disconnect the ethernet cable from the Pi4.
The green and yellow LED’s on the ethernet connect will remain on even when the OS has been shut down safely.