fan_ctrl.py

#!/usr/bin/python3
import RPi.GPIO as GPIO
import json
from time import sleep

# Load User settings
with open(__file__.replace('.py', '.json')) as file:
    config = json.load(file)

# Load Fan Profile
curve = config['profiles'][config['profile']]

# Use Broadcom GPIO Numbers
GPIO.setmode(GPIO.BCM)

# Initialize GPIO Pin
GPIO.setup(config['gpio_pin'], GPIO.OUT)

# Set PWM Frequency
fan = GPIO.PWM(config['gpio_pin'], config['pwm_freq'])

# PWM Start with fan turned off
fan.start(0)

# User Settings no longer needed
config.clear()

# The current CPU Fan status (on/off)
status = False

# Temp history, used for calculating trend
history = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

# The main loop
while True:
    # Get CPU Temp
    with open("/sys/class/thermal/thermal_zone0/temp", "r") as sensor:
        temp = int(float(sensor.read()) / 1000)

    # Reset the fan speed
    speed = 0

    # Should the fan be turned off?
    if temp <= 40:
        # Turn off the fan
        status = False

    # Is the fan on or should it be?
    elif status or temp >= 50:
        # Clamp the temperature to the fan curve
        if temp <= 50:
            index = 0
        elif temp > 80:
            index = 30
        else:
            index = temp - 50

        # Check if it's an upward trend
        if ((sum(history) / 10) < temp) or temp < 50:
            # Try to stabilize the temperature
            # TODO: Need to test this further
            if index < 30:
                index += 1

        # Remove the first entry
        history.pop(0)

        # Add temperature to the list
        history.append(temp)

        # Load fan speed from curve
        speed = curve[index]

        # Keep the fan on
        status = True

    # Update fan speed
    fan.ChangeDutyCycle(speed)

    # Go back to sleep... ZzZzZz
    sleep(2.00)