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What size fan will fit over official case's top HAT opening?

Thu Dec 08, 2016 1:57 pm


What are the precise dimensions of the HAT opening in the official RPi 3's case with it's top layer off? I ask since I wonder if I buy one will I be able to fit perhaps a 60mm fan without it falling in? Or would I need a 70mm fan?

Is this even a suitable case to add a fan too? I'm not seeing much in the way of vents in the photos, for air to be pulled or pushed through by a fan.

TIA :-)
Frog blast the vent core!

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Joined: Tue Mar 10, 2015 10:20 am

Re: What size fan will fit over official case's top HAT open

Fri Jan 20, 2017 12:07 pm

I have an old Pi1 model B in a ModMyPi case. This particular case has 7 holes in the bottom (one central hole and 6 surrounding it) for ventilation purposes.

I recently bought a Pi3 with the official case and power supply, for running Lakka for game console emulation. I used the bottom of the ModMyPi case as a template to draw 7 circles in the bottom of the official case, roughly under where the memory chip is on the Pi3, and I used a Black & Decker drill with 3mm drill bit to bore the 7 holes. As the official case has four rubber feet, this means air can circulate through these holes.

I also bought a set of aluminium heatsinks, which I attached to the SoC and the USB/Ethernet controller chip. The heatsink for the RAM chip won't fit on between the bottom of the board and the bottom part of the case, so I've left it for now.

I elected to keep the entire white plastic "lid" of the case, and mount a fan on the underside of that white lid, with the body of the fan poking through the part where the HATs go. I originally bought a 5v 30mm fan, but it turned out to be catastrophically noisy, so I've discarded it - but not before drilling holes for it to fit, and holes for airflow for that fan... So I went to a company who specialise in building quiet or silent PCs, and bought a 40mm 5v fan (the Noctua NF-A4 FLX 5V). This fan is MUCH quieter than the whiny 30mm I junked, but it's still noisier than I'd like it to be. I'm not convinced a 50mm fan would fit through the HAT gap properly.

The Noctua is a quality product, but has a couple of flaws for Pi use - one, is the fan connector is 3-pin. Second, the wired in cable is VERY long. They provide a 3-pin to 2-pin adapter, but this makes the cable even longer. Thankfully, they also provide four 3M Scotchlock connectors, which can be used to join cabling together without soldering - literally all you need is a pair of pliers. So I cut the 3-pin connector off the fan, and used the Scotchlocks to join on the 2-pin connector, and connected that to the 5v and GND pins (4 and 6, respectively) on the GPIO header. Hey presto, the fan works!

The Noctua also comes with four rubber fan mounts, to reduce vibration. I had to use a 4mm drill bit to open up the holes for those mounts to go through.

It makes a huge difference to Pi cooling; when fully loaded, the "vcgencmd measure_temp" command reveals around 45 - 48 Celsius (under full load and with no heatsinks/fans I have seen temperatures above 80 Celsius; this is around the point the Pi starts to throttle back its performance to reduce risk of hardware failure.

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