I was approached the other day for cooling advice for an SBC (single board computer) project.
Without going into unnecessary detail, the issue is that the board has to work in an unusually hot environment, and even with a heatsink and fan installed, the processor runs almost on the thermal edge.
If a heatsink and fan are not enough to cool the board, what can be done without using many modifications? (The board in question is a Radxa Rock 5 Model B, but the solution below also works on a Raspberry Pi.)
Also: How to cool your Raspberry Pi (and should you?)
I remember overclocking processors on desktop computers a lot, and the more you push them beyond their comfort zone, the more they work, and the more heat they generate that needs to dissipate.
One solution I used was a Peltier thermoelectric cooler module. It works by exploiting the Peltier effect. In simple terms, when an electric current is passed through two different conductive materials (usually a pair of semiconductors) that are joined together, heat is transferred from one side to the other. This results in one side becoming cooler while the other side becomes warmer.
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Peltier Thermoelectric Cooler Module – 5 Volt/1 Amp
- Create a temperature difference
- 5V module
- Rated for 5W max (5V/1A)
- Maximum temperature difference: 65°C/149°F
The Peltier cooler is named after Jean Charles Athanase Peltier, a French physicist who, in 1834, discovered the thermoelectric effect that now bears his name.
It’s a weird effect — I’ll never get over how weird it is to hold something that’s hot and cold at the same time –but it’s a great way to keep something cold. The hot side of the cooler itself requires a heatsink and fan to conduct the heat, but the Peltier thermoelectric module is a more effective cooler than using a heatsink and fan alone.
Also: How to overclock and stress-test your Raspberry Pi
You can see this effect in the thermal image below, although thermal cameras are not accurate due to the emissivity (ie, reflectivity) of the ceramic surface of the Peltier module.
I use it to great effect with overclocked processors, and wonder if I can gerry-rig something to work here.
Also: Finding the Raspberry Pi: Where to buy the latest model and its alternatives
Peltier modules come in all kinds of sizes and ratings. The one I use is a modest 30 x 30 mm that runs at 5V / 1A (although the module will happily run at 3V in my tests), which means I can do it (and the fan) in one small power supply. There are larger Peltier modules out there, but they may be overkill for this type of cooling project.
Here’s what you need;
Thermal paste should be applied between the cold side of the Peltier module and the chip you are cooling, and between the hot side of the module and the heatsink. The paste helps to improve the transfer of heat between the air gaps that should be on each side of the module.
The cooler fan I have for the Rock 5 Model 5 has fittings that can attach to the board. (I had to use longer fasteners.) For a Raspberry Pi, I put the Peltier in the middle of a dedicated Raspberry Pi cooler.
Also: The best cooler for Raspberry Pi power users
The main thing to remember when assembling a project like this is that the cold part of the Peltier goes where you are cooling. Don’t get it wrong! Sometimes they are marked, but if not, you need to power up your module to feel the difference.