fan_chassis.py

#!/usr/bin/python3

### IMPORTANT ###
# you must enable pwm chanels in /boot/config.txt
# see https://github.com/Pioreactor/rpi_hardware_pwm

# python modules
from rpi_hardware_pwm import HardwarePWM
import time
import signal
import sys
import os
import sys, getopt
import json

# Configuration
PWM_CHANNEL = 0      # PWM channel used to drive PWM fan (gpio18 = channel 0)
WAIT_TIME = 5        # [s] Time to wait between each refresh
PWM_FREQ = 65        # [Hz] 10kHz for Noctua PWM control

# Configurable temperature and fan speed
MIN_TEMP = 55
MAX_TEMP = 75
FAN_LOW = 20
FAN_HIGH = 100
FAN_OFF = 0
FAN_MAX = 100

# logging and metrics (enable = 1)
VERBOSE = 0
NODE_EXPORTER = 0
JSON_EXPORTER = 0

# parse input arguments
try:
   opts, args = getopt.getopt(sys.argv[1:],"hv",["min-temp=","max-temp=","fan-low=","fan-high=","wait-time=","help","pwm-channel=","pwm-freq=","verbose","node-exporter","json-exporter"])
except getopt.GetoptError:
   print('fan.py [--min-temp=40] [--max-temp=70] [--fan-low=20] [--fan-high=100] [--wait-time=1] [--pwm-channel=0] [--pwm-freq=10000] [--node-exporter] [--json-exporter] [-v|--verbose] [-h|--help]')
   sys.exit(2)
for opt, arg in opts:
   if opt in ("-h", "--help"):
      print('fan.py [--min-temp=40] [--max-temp=70] [--fan-low=20] [--fan-high=100] [--wait-time=1] [--pwm-channel=0] [--pwm-freq=10000] [--node-exporter] [--json-exporter] [-v|--verbose] [-h|--help]')
      sys.exit()
   elif opt in ("-v", "--verbose"):
      VERBOSE = 1
   elif opt in ("--min-temp"):
      MIN_TEMP = int(arg)
   elif opt in ("--max-temp"):
      MAX_TEMP = int(arg)
   elif opt in ("--fan-low"):
      FAN_LOW = int(arg)
   elif opt in ("--fan-high"):
      FAN_HIGH = int(arg)
   elif opt in ("--wait-time"):
      WAIT_TIME = int(arg)
   elif opt in ("--pwm-channel"):
      PWM_CHANNEL = int(arg)
   elif opt in ("--pwm-freq"):
      PWM_FREQ = int(arg)
   elif opt in ("--node-exporter"):
      NODE_EXPORTER = 1
   elif opt in ("--json-exporter"):
      JSON_EXPORTER = 1
print("")
print("MIN_TEMP:",MIN_TEMP)
print("MAX_TEMP:",MAX_TEMP)
print("FAN_LOW:",FAN_LOW)
print("FAN_HIGH:",FAN_HIGH)
print("WAIT_TIME:",WAIT_TIME)
print("PWM_CHANNEL:",PWM_CHANNEL)
print("PWM_FREQ:",PWM_FREQ)
print("VERBOSE:",VERBOSE)
print("NODE_EXPORTER:",NODE_EXPORTER)
print("JSON_EXPORTER:",JSON_EXPORTER)
print("")

# Get CPU's temperature
def getCpuTemperature():
    res = os.popen('cat /sys/devices/virtual/thermal/thermal_zone0/temp').readline()
    temp = (float(res)/1000)
    return temp

# Set fan speed
def setFanSpeed(speed,temp):
    pwm.change_duty_cycle(speed)

    # print fan speed and temperature
    if VERBOSE == 1:
        print("fan speed: ",int(speed),"    temp: ",temp)

    # write fan metrics to file for node-exporter/prometheus
    if NODE_EXPORTER == 1:
        # Save a reference to the original standard output
        original_stdout = sys.stdout 
        with open('/var/lib/node_exporter/fan-metrics.prom', 'w') as f:
            # Change the standard output to the file we created.
            sys.stdout = f 
            print('raspberry_fan_speed ',speed)
            print('raspberry_fan_temp ',temp)
            print('raspberry_fan_min_temp ',MIN_TEMP)
            print('raspberry_fan_max_temp ',MAX_TEMP)
            print('raspberry_fan_fan_low ',FAN_LOW)
            print('raspberry_fan_fan_high ',FAN_HIGH)
            print('raspberry_fan_wait_time ',WAIT_TIME)
            print('raspberry_fan_pwm_channel ',PWM_CHANNEL)
            print('raspberry_fan_freq ',PWM_FREQ)
            # Reset the standard output to its original value
            sys.stdout = original_stdout
            f.close()
    # write fan metrics to json file for Home Assistant
    if JSON_EXPORTER == 1:
        dFan = {
            'fan_speed': speed,
            'cpu_temp': temp,
            'cpu_min_temp': MIN_TEMP,
            'cpu_max_temp': MAX_TEMP,
            'fan_speed_low': FAN_LOW,
            'fan_speed_high': FAN_HIGH,
            'scan_time': WAIT_TIME,
            'pwm_channel': PWM_CHANNEL,
            'fan_frequency': PWM_FREQ
        }

        jsonString = json.dumps(dFan)
        jsonFile = open('/usr/share/hassio/homeassistant/files/chassis_fan.json','w')
        jsonFile.write(jsonString)
        jsonFile.close()
    return()

# Handle fan speed
def handleFanSpeed():
    temp = getCpuTemperature()

    # Turn off the fan if temperature is below MIN_TEMP
    if temp < MIN_TEMP:
        setFanSpeed(FAN_OFF,temp)

    # Set fan speed to MAXIMUM if the temperature is above MAX_TEMP
    elif temp > MAX_TEMP:
        setFanSpeed(FAN_MAX,temp)

    # Caculate dynamic fan speed
    else:
        step = (FAN_HIGH - FAN_LOW)/(MAX_TEMP - MIN_TEMP)
        delta = temp - MIN_TEMP
        speed = FAN_LOW + ( round(delta) * step )
        setFanSpeed(speed,temp)

    return ()

try:
    # Setup hardware PWM 
    pwm = HardwarePWM(pwm_channel=PWM_CHANNEL, hz=60)
    pwm.change_frequency(PWM_FREQ)
    pwm.start(FAN_LOW) # full duty cycle

    # Handle fan speed every WAIT_TIME sec
    while True:
        handleFanSpeed()
        time.sleep(WAIT_TIME)

except KeyboardInterrupt: # trap a CTRL+C keyboard interrupt
    setFanSpeed(FAN_OFF,MIN_TEMP)