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I have a Pi3 in a fairly enclosed environment, and I found that, even when my Pi was relatively idle (5% CPU usage) the CPU temp was averaging around 80C, which is close to the 85C where the Pi starts to underclock and the 90C where the Pi starts to get damaged. Since I'm planning some more processor-hungry tasks, I want beef up the cooling, if only for performance reasons.

I already have a heatsink on the Pi's main chip, so I'm considering adding a very small fan. I found that even slightly blowing on the chip immediately takes the temp down to 60, so it's entirely an air-flow problem, so even a very weak tiny fan should work.

Unfortunately, I don't have any more room to add a power regulator to supply the fan, so I need to power it directly from the Pi's 5V power rail and controlled via a GPIO pin. What are the fan specs I should be looking for so it doesn't exceed the Pi's max current? Is anyone aware of any very tiny and silent 3.3V or 5V fans suitable for this?

Cerin
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    If you want to turn on/off the fan you could use a simple transistor switch according to this wiring - just replace the relay with your fan http://raspberrypi.stackexchange.com/q/27928/19949 The restrictions as listed in joan's answer apply. – Ghanima Oct 12 '16 at 17:08
  • If you're feeling crafty ya could try building a small Stirling Engine and replace the fly wheel with waited fan. Hotter the CPU faster the fan spins. Been thinking about doing this for awhile so let us know if you beat me to it :-) – S0AndS0 Oct 12 '16 at 23:53
  • @S0AndS0, Instructions unclear. Raspberry Pi on fire. :) – Cerin Oct 13 '16 at 03:13
  • Sorry @Cerin, Stirling Engines are heat pumps and they don't require a large temp difference, so no fire needed. By placing the tip of the piston against any heat source, in this case you're CPU, & allowing the other end to be chilled by the ambient room temperature there should be enough thermal difference to cause the engine to keep running. By replacing the traditional flywheel with a fan of similar wait the whole unit could be setup to pull fresh air across the underside of your RPi. Additional benefit would be that it would keep running till your RPi is room temp & friction stops fan. – S0AndS0 Oct 13 '16 at 06:00

4 Answers4

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You can power a small 5v fan off the 5V and the GND pins on Raspberry's GPIO pins. Check the GPIO layout HERE.

I use this Kit and use pin 2 and 6.

Hope this helps

DCL
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  • I've confirmed this. I'm powering this tiny fan directly from the Pi's 5V pin. My multimeter says it's barely drawing 5mA. – Cerin Dec 11 '16 at 20:14
  • i've read on several forums that you should not connect the fan directly to the gpio pins because this could destroy the pi over time. now we have 2019 and i would like to ask u guys if you have ever encountered problems due to using the fan directly connected to your gpio pins. – AlexOnLinux Mar 17 '19 at 09:15
  • If its only 5mA you are safe, but anything over that should not be done. – PLASMA chicken Jun 06 '19 at 15:45
  • I've been running the same 5v Fan off the 5v and GND pins since my last post (Dec 11, 2016). No problems or issues. – DCL Jun 07 '19 at 22:52
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I can confirm that I also haven't had any problem powering a low profile 5V Noctua 40mm x 10mm fan from the 5V and GND pins. These pins are always on. This is on a Raspberry Pi 3B+ used as an Octoprint server.

The power drain is minimal.

Rob Willett
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You can not power a fan from the Pi's GPIO. The GPIO are all 3V3 and only supply a few tens of milliamps at best (you are recommended to draw no more than 16mA from an individual GPIO).

You can power a fan from a 5V power rail pin on the expansion header. You might be able to power a fan from a 3V3 power rail pin on the expansion header but that will depend on your Pi model. Early Pis had very limited 3V3 power available.

joan
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  • What's the maximum current I could safely draw from the 5V rail without effecting the Pi's operation? – Cerin Oct 12 '16 at 21:00
  • Assuming you power via the microUSB it will depend on the Pi model you are using (which determines the amp rating of any polyfuse fitted as well as the likely consumption by the Pi itself). – joan Oct 12 '16 at 21:03
  • As my question states, I'm using a Pi3, and I'm using the 5V pin, not USB. – Cerin Oct 13 '16 at 13:24
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If you want a really silent fan, I suggest powering a regular fan with a lower voltage. The safest bet is to get a 5V fan and try it with 3.3V: it will almost certainly rotate at roughly half the RPM, which reduces the noise a lot. If it doesn't work, or the airflow is not sufficient, you can still power it with 5V.

Another option (that I personally use) is to get a 12V fan and power it with 5V.

There are some cooling assemblies for grahpic cards available on e-bay which include a small heatsink and a 5 or 12V fan. Some of those are really cheap and also quite small, so they fit the Pi perfectly. The screws/clips will not fit of course, but you can attach them with a very thin layer of super glue.

Dmitry Grigoryev
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