Hello again, fellow readers and fixers! Since the previous part, we looked again at implementing a cooling solution for our media centre build project. We intended to reuse one of the fans I salvaged from some old laptops as an exhaust fan. However, a problem enters…
Why not use a laptop fan for our media centre build?
Well, we realised that the fan we chose for the project constantly ran at full speed when we tried it. We can get away with that by connecting the 5v and ground wires directly to the Pine H64 SBC. That way, we can keep the whole media centre build simple. But it’s usually not necessary to run the fan at full speed when the computer is idle. Also, laptop fans can run loud when they operate at full speed.
Gareth set up a rig that lets us test fans, so that they’re viable for different projects. We tried the most suitable laptop fan on the rig. While it shifted quite a lot of air, we couldn’t find a way to change the fan speed. We needed a fan that can adjust its speed to match thermal conditions, yet is also compact.
Time to acquire a new fan…
We ultimately settled for buying a new compact fan to keep it cool. The fan we chose was a Noctua NF-A4x20. It’s a 40mm fan that is small and quiet, yet has good cooling performance! Of course, we experimented with it.
We tried using tape to secure the fan to the removable plastic and fabric cover. But it’s prone to falling off when we tested it. So Gareth used hot glue to hold the fan in place instead. I routed the fan cable out of the unit, so that we can connect the wires externally.
Once again, I ran Big Buck Bunny on YouTube in 720p to test the cooling. I used the HTop software to check the CPU temperatures. Unfortunately, we found that the overall cooling performance was…not great. I saw temperatures running as high as 86 °C during video playback!
Why is our media centre build so toasty?!
The most obvious issue here as it stands, is the lack of ventilation. With nothing to let the warm air out of the case, the enclosure traps the air inside. This makes the SoC throttle itself to prevent heat damage, in turn reducing performance. We’ll remedy this by first creating holes at the top of the case. This will let the warm out out of the case passively. Then, we can secure the fan from the inside, with the airflow pointing outside.
The second issue here is the position of the small heatsink. We positioned it in a way that goes against the direction of the airflow. We’ll try turning it 90 degrees, so that the cool air passes along all of the fins. Failing that, we can look again at reusing chipset heatsinks. They’re larger, and can help better dissipate heat.
All being well, those should help keep it running cool. Gareth is also experimenting with the PWM feature on the Noctua fan. He’s using an Arduino board and a tiny fan controller with the fan itself. Using a script, he aims to control the fan speed, based on the temperature of the SoC. One we’re happy with the cooling performance, we’ll flash Armbian to the eMMC module. Then, we’ll add the completed fan control scripts to the OS.
And that’s all for now! Once we’ve sorted out the cooling, we’ll be closer to completing our media centre PC project. So until then, remember; just keep calm and keep on fixing!