Raspberry Pi 4


The Recalbox Team.

Script to turn off cooler

  • Themer

    Is there any script to turn off the cooler when you request to turn off the recalbox?

  • @azvarel Coolers are usually plugged on the very first pins of a pi. These are always powered. What you'd want requires a GPIO script

  • Themer

    @Substring I thought I could still do a script to turn it off and if I turned it on pins 17 and 20, the 17 still got direct power?

  • @azvarel pins noted as 5V or 3.3V most probably always deliver a voltage as long as the pi is plugged to a working power supply. So you need playing with programmable GPIO.

  • Themer

    @Substring so I could play on any other GPIO pin and program on it?
    I would like to give a voltage of 5v on any progrmado pin? Or is it not possible?

  • Translation Master

    @azvarel you could do something like I did some time ago..and then if you shut down your recalbox, just set the GPIO of the transistor to LOW.

    But..a big BUT..I think the gpio has an undefined logic level if the software is shut down. Just try it out. I also need to check how mine is behaving 😄 its a long time ago 🙂


  • @azvarel Setting a GPIO to a logical 1 level means outputting 3.3V i think. Beware of the current level, a GPIO can't deliver much

  • Themer

    @lackyluuk said in Push button (ON/OFF) script problems?:

    @PenPen: I am sorry for this way too late answer. Not sure if you need an answer anymore

    Here is an example with GPIO pin 14 for controlling the fan. The indents might not be correct 😉 I had a little trouble with copy/paste the code 😄
    Hope I can help you with this

    #!/usr/bin/env python

    import os
    import time
    import RPi.GPIO as GPIO

    #Set max. temperature of CPU
    TEMP_MAX = 67
    ON_TIME = 200
    #Set pin 14 as transistor gate
    GATE = 14
    #Set pin 14 as an output and shut down
    GPIO.setup(GATE, GPIO.OUT)
    GPIO.output(GATE, False)

    def getCPUtemperature():

    while True:

      	temp_float = float(getCPUtemperature())
      	if (temp_float > TEMP_MAX):
      		# ein
      		GPIO.output(GATE, True)
      		# aus
      		GPIO.output(GATE, False)
      		GPIO.output(GATE, False)

    except KeyboardInterrupt:
    print float(getCPUtemperature())
    print "power off fan..."
    GPIO.output(GATE, False)
    print "cancelling..."

    Forgot to attach a short drawing. I used the official RaspberryPI 5V DC fan.


    I will ask the questions here instead of being there.

    So I understood your script when it reaches a temperature it turns on the cooler, when it cools it turns off. it is?

    @Substring I'm not a programmer, I'm afraid to do something and go wrong.

  • Developer
    Global moderator

    A more simple solution is to plug the fan cooler on the USB Connector. These one are stopped when the system stops.

  • Translation Master

    @azvarel yes exactly, this script controls the fan depending on the temperature. If you don't need this you can just turn the fan ON at startup and OFF at shutdown.

    Or as @ian57 alrrady mentioned, to use a USB slot if you have one free. They deliver also 5V DC.

  • Themer

    @ian57 This idea is great, but I use the other ports for usb controllers, xbox360 receiver and are on the front of SNES 😞

    If I soldered the wires at the voltage points of the USB, would it have problem when plugging a controller or a usb key? If it does not give you trouble, I do it even easier for me.

    If I do not have to follow the script of @lackyluuk, I just did not understand there in the diagram the why of having a transistor, for safety?

  • Developer
    Global moderator

    @azvarel; the transitor is for switch and safety. I don't think that standard GPIO can supply enough power to run your fan correctly. So we use the +5V directly from the power supply to power the fan, and the GPIO + transitor are making the script controllable switch.

    Soldering to get only the power supply is a bit risky for the plugged element I think. A fan, is a motor, and it can have bad effects on it's power circuit. And the usb deliver at max 500mA. If you try to do that .. not on an usb key slot... try it on the usb snes controller slots... it uses less current ...

    If someone elsehas an idea about that?

  • Themer

    @ian57 so we went back to the script.

  • @azvarel the script looks like it takes 100% CPU, but it looks logically correct.
    The electronic schematic is very simple and could help someone like @ian57 who wants to drive a 12V power supply 😄

  • Translation Master

    @azvarel @Substring just add a time.sleep(1) or (2) into the while() loop

  • Well, maybe i say a stupidity but with a thermal switch? It avoids the question of the script and you can choose one with a temperature of closing and opening of your choice.

  • Themer

    @tikiandskull nothing is stupid, any idea is valid, where would you find this thermal switch?

  • @azvarel maybe something like this link text It can be found on amazon, conrad, etc some works in 5v others in 12v.

    Afterwards, I do not know how it could be positioned, but probably with the probe as close as possible to cpu

    (sorry for my poor English 🙂 )

  • #!/usr/bin/env python3

    import os
    from time import sleep
    import signal
    import sys
    import RPi.GPIO as GPIO

    pin = 27 # The pin ID, edit here to change it
    maxTMP = 50 # The maximum temperature in Celsius after which we trigger the fan
    sleepTime = 30 # The time to sleep between temp checks

    def setup():
    GPIO.setup(pin, GPIO.OUT)

    def getCPUtemperature():
    temp =(res.replace("temp=","").replace("'C\n",""))
    print("temp is {0}".format(temp)) #Uncomment here for testing
    return temp

    def fanON():
    print("Fan on ...")

    def fanOFF():
    print("Fan off ...")

    def getTEMP():
    CPU_temp = float(getCPUtemperature())
    if CPU_temp > maxTMP:
    sleep(sleepTime) # Sleep additional time in order to ensure that we stay below max temp ...

    def setPin(mode): # A little redundant function but useful if you want to add logging
    GPIO.output(pin, mode)

    while True:
    sleep(sleepTime) # Read the temperature every x amount of seconds ...
    except KeyboardInterrupt: # trap a CTRL+C keyboard interrupt
    GPIO.cleanup() # resets all GPIO ports used by this script

  • With this transistor 2N4401 600 mA, 40V and 5v fan Works perfectly.

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