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I got my RPI3 cooled by a 5v dc fan and it only activates when it reaches 55°C so everything is fine i control it with PWM.

Now i want to cool it with a bigger 12V DC fan the problem is i need 12V, either from external source or from the PI itself and in this case i need a dc-dc converter which i found here

the thing is i can't find on the internet a similar project and how to cable it that's why i'm asking for help.

tried to do it myself on fritzing but i really dont think its good.

update : assuming the fan is a 4 wires (12v/grd/pwm/rpm) i did this on fritzing:

enter image description here

yellow wire is connected to PWM gpio.

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  • Are you not concerned about overloading the Pi?
    – Mohammad Ali
    Jul 9 '17 at 17:21
  • @MohammadAli how come ? The fan runs at 12v 0.20A
    – Corn
    Jul 9 '17 at 17:25
  • that's like 2.4 watts you sure your power supply is capable of that plus the spike in power required normally around 4-6 watts to start the fan?
    – Mohammad Ali
    Jul 9 '17 at 18:00
  • @MohammadAli What should i do to know how much my Pi consumes ? Is the limit the same for all PIs ? Or does it depend of my power supply ?
    – Corn
    Jul 9 '17 at 18:11
  • It's more about the power supply as the pis 5v line is just a pass through of the USB power
    – Mohammad Ali
    Jul 9 '17 at 18:12
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I would personally recommend that you use either a dedicated power supply or a usb to 12v dc-dc boost converter like this. Furthermore do check whether or not your fan is capable of detecting a 3.3v pwm signal as that is the max and only voltage the pi's gpio operates on. which means that you will likely also need a dc-dc boost converter on your pwm signal as well.

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"the thing is i can't find on the internet a similar project" This is for the simple reason that it will NOT work.

You are likely to blow up the Pi.

On top of that you don't actually need a fan.

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  • I'm getting mixed answers here, could you explain me why it would not work please ? Would it work through a relay with 12v battery powering the fan ?
    – Corn
    Jul 11 '17 at 6:17
  • @Corn Poorly asked questions with no supporting information tend to attract speculation. Realistically no one can answer. Connecting an (unspecified) 12V powered device (presumably intended for a desktop PC) to a 3.3V GPIO is unlikely to work, and risks damage. My "answer" was more intended to warn of the risk. This in addition to the fact that the (unspecified) Pi is unlikely to be able to supply sufficient current from your (unspecified) power supply.
    – Milliways
    Jul 12 '17 at 1:23

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