Raspberry PI 4: PoE with LM2596

During last Black Friday I bought Raspberry PI 4 on Aliexpress for just $36. After initial tests I’ve found out that a good cooling case is definitely a must have. The SoC quickly reaches 80°C under a full load and then throttles from 1.5 to 1.0 GHz per ARM core to maintain the temperature limit, so I ordered a very nice Chinese aluminum case. I love PoE devices – my new toy must also support Power over Ethernet – and it does!

I took a cheap LM2596 DC converter and installed it together with the board in the aluminium case.

There are some important things to consider:

• This LM2596 module will not fit normally inside this case. I had to cut the PCB edge near the OUT GND pad.
• I removed the potentiometer, which is the tallest element on the PCB. I used fixed resistors to set the 5.2 V output.
• The LM2596 PCB is double sided and the (+) pads are also on both sides. Therefore the module should be isolated from the aluminium surface of the case.

The aluminium case comes with all thermopads included. Under continuous full CPU load (without overclocking) the SoC is below 70°C without any throttling in a room temperature.

When overclocked to 2.0 GHz it definitely needs additional active cooling (i.e. a fan), as the temperature quickly rises to 80°C, the ARM frequency frequently drops to 1.33 GHz and it takes almost 11 W (!) with 24 V PoE voltage. I don’t care about GPU though.

It will upgrade my previous Raspberry PI 3 B+ and I will use it for:

• FM DX: XDR-F1HD tuner remote control & Opus audio encoding
• Wi-Fi DX: Two instances of MTscan in a VNC session
• Continuous FT8 decoding on the 144 MHz band with Airspy HF+ (planned)