mqtt-pi-pwn-fan

1st_readme.md

MQTT client to control a PWM fan from a raspberry pi

A simple python script to control a fan from Home Assistant.

• Installing dependencies on a stock Raspbian install:

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install python3-pip python3-dev python3-gpiozero 
sudo pip3 install paho-mqtt

• Create the python script as /home/pi/mqtt_fan.py
• Create a systemd service definition file as /lib/systemd/system/mqtt_fan.service
• Set permissions:

sudo chmod 644 /lib/systemd/system/mqtt_fan.service

• Enable and test the service:

sudo systemctl daemon-reload
sudo systemctl enable mqtt_fan.service
sudo systemctl start mqtt_fan.service

configuration.yml

# Snippet to add to a Home Assistant configuration yaml file
mqtt:

fan:
  - platform: mqtt
    name: "My Fan"
    command_topic: "homeassistant/test_fan/on/set"
    state_topic: "homeassistant/test_fan/on/state"
    speed_command_topic: "homeassistant/test_fan/speed/set"
    speed_state_topic: "homeassistant/test_fan/speed/state"
    payload_low_speed: "low"
    payload_medium_speed: "medium"
    payload_high_speed: "high"
    speeds:
      - low
      - medium
      - high

mqtt_fan.py

#!/usr/bin/python3

import paho.mqtt.client as mqtt
from gpiozero import PWMOutputDevice

# MQTT configuration
broker = '127.0.0.1'
device_id = 'test_fan'
on_topic = 'homeassistant/' + device_id + '/on/set'
on_state_topic = 'homeassistant/' + device_id + '/on/state'
speed_topic = 'homeassistant/' + device_id + '/speed/set'
speed_state_topic = 'homeassistant/' + device_id + '/speed/state'

# gpio settings
gpio_pin = 18
pwm_freq = 5000
speeds = {'low':  0.05, 'medium': 0.4, 'high': 1}

class PwmFan:
  on_state = 'OFF'
  pwm = PWMOutputDevice(gpio_pin,frequency=pwm_freq)
  speed_state = 'high'

  def switch(self, onoff):
    if onoff == 'ON':
      if self.on_state == 'OFF':
        self.on_state = 'ON'
        self.set_speed(self.speed_state)
    elif onoff == 'OFF':
      if self.on_state == 'ON':
        self.on_state = 'OFF'
        self.pwm.off()

  def set_speed(self,speed):
    if speed in speeds:
      if self.on_state == 'ON':
        self.pwm.value=speeds[speed]
      self.speed_state = speed


fan = PwmFan()

def on_message(client, userdata, message):
  payload = str(message.payload.decode("utf-8"))
  topic = message.topic
  if topic == on_topic:
    print("ON/OF command received")
    if (payload == 'ON') or (payload == 'OFF'):
      print("turning " + payload)
      fan.switch(payload)
      client.publish(on_state_topic, payload)
      if payload == 'ON':
        client.publish(speed_state_topic, fan.speed_state)
  elif message.topic == speed_topic:
    if payload in speeds:
      print('Setting speed to ' + payload)
      fan.set_speed(payload)
      if fan.on_state == 'ON':
        client.publish(speed_state_topic, fan.speed_state)

# Send messages in a loop
client = mqtt.Client("myfan")
client.on_message = on_message
# If your homeassistant is protected by as password, uncomment this next line:
# client.username_pw_set('homeassistant','yourpasswordhere')
client.connect(broker)
client.subscribe(on_topic)
client.subscribe(speed_topic)
client.loop_forever()

mqtt_fan.service

[Unit]
Description=MQTT Fan
After=multi-user.target

[Service]
Type=idle
ExecStart=/usr/bin/python3 /home/pi/mqtt_fan.py

[Install]
WantedBy=multi-user.target