Quiet Raspberry Pi 4B case with active cooling

cults3d

I wanted a super-quiet Raspberry Pi 4B case for tinkering with it as a desktop, but knew it needed some serious cooling action.\nI ordered some 28mm x 28mm x 20mm heatsinks and designed this around them.\n\nDesign considerations:\n* Use a massive heatsink so minimal airflow is required. I provide an easy-to-print alignment tool to ensure the heatsink is perfectly positioned for the cover to fit.\n* Direct airflow through the heatsink, don't leave proper airflow to chance.\n* Duct air in one side and out the opposite to maximize the likelihood of pulling fresh air.\n* Squirrel-cage blowers can be much quieter than fans and handle pressure differentials far better, so I used a 4010 blower.\n* The primary source of noise for a blower is the intake, so I wanted the intake fully inside the case, that meant it's going to be used as an extractor.\n* The second loudest source of noise from one of these blowers is the backside, where the motor is mounted. Fully enclosing the blower inside the case helps block some of that noise.\n* Underdriving a fan or blower is a common way to reduce noise. I'm using a heatsink with a huge surface area, so it doesn't need a tremendous amount of airflow. However, I wanted to run a 12V blower faster than 5V would drive it, so I chose an MT3608 boost converter (Amazon product ID: B07RNBJK5F) to raise the voltage to the blower. This boost converter has no mounting holes, so I made it snap in place.\n* External control of the blower speed would be handy so you don't have to take the case apart for an adjustment. I provided a very small hole in the top for you to access the potentiometer with a small screwdriver, adjusting the output voltage.\n* Single power source drives both the Pi and the blower. The boost converter is connected to the Pi's power lines for supply voltage.\n* Many cases recess the connectors too much for some cables. I made all connectors flush with the outside of this case, with very close clearances and a bevel to accommodate the flared edges of the connectors. Keeping these areas clear is crucial.\n\nI used these 28mm x 28mm x 20mm heatsinks:https://www.aliexpress.com/item/32618788162.html\nYou can use other heatsinks of the same width, height isn't as important. The key part is that it fills out the duct. If the heatsink is too narrow, too much air can flow around the outside of it, reducing its effectiveness.\n\nI used 3M thermal adhesive padding (sort of like double-sided tape, without the tape) to attach the heatsink:https://www.aliexpress.com/item/32794560201.html\n\nI also used a copper shim as a heat-spreader between the heatsink and microcontroller:https://www.aliexpress.com/item/32826278552.html\nI'm not sure if the shim is providing a benefit or not. The adhesive is extremely sticky, you have one chance to apply it correctly, so I didn't test multiple configurations.\n\nIf you don't want to use a boost converter and don't mind the increased volume of a fully driven fan, they do make 5V 4010 blowers:https://www.aliexpress.com/item/32998581988.html\n\nIn my testing (comparing with a coworker's Pi 4), this case keeps the Pi 4 cooler than the Flirc case can, while still running almost dead silent. I'm glad I finished this before the Flirc was introduced, else I would not have designed it. The advantage of the Flirc over this one is it has no moving parts. This one has the fan. However, this doesn't block wifi signals, and my coworker has found the Flirc definitely attenuates the wifi signal.\n\nUpdate (2020/01/11): 5V 4010 blowers can be found if you don't want to use the buck-converter and don't mind running the blower at full speed (it will be louder than when underdriven). I'd recommend my approach if you want it to be as quiet as possible.