To notify myself when CO2 level rises in my home office I built custom sensors. Next, it was time to build a notification light. These will show us when to open the windows and get some fresh air in our home. I chose the ESPhome platform to connect to our home automation since it’s very easy to set up. I still had a few addressable RGB LEDs (WS2811) which fit perfectly. As a microcontroller, I used Nodemcu v2. You can find the .stl files on Github.

The blog post is divided into two steps:

  1. Hardware setup
  2. Automation

Hardware setup

First, I designed the notification light to be 3D printed. The Nodemcu is installed on the bottom. One WS2811 is installed in the middle.

Full view
Half view
Printed light

Here is the ESPhome configuration I use.

esphome:
  name: led-status-1

esp8266:
  board: nodemcuv2

# Enable logging
logger:

# Enable Home Assistant API
api:

ota:
  password: "*****************"

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password

  # Enable fallback hotspot (captive portal) in case wifi connection fails
  ap:
    ssid: "Led-Status-1 Fallback Hotspot"
    password: "*******"

light:
  - platform: neopixelbus
    type: RGB
    variant: WS2811
    pin: GPIO3
    num_leds: 1
    name: "NeoPixel Light"
    id: led_status_1
    effects:
      - pulse:
          name: "Slow Pulse"

          update_interval: 1s
    on_turn_on:
      then:
        - light.turn_on:
            id: led_status_1

Automation configuration

After building the light it’s time to set up the automation. I have one sensor installed in each room. The automation is triggered on every change in measurement. Depending on the value the light is set to a specific color:

  • below 1000 ppm – light is turned off
  • above 1000 and below 1500 ppm – light is set to yellow
  • above 1500 and below 2500 ppm – light is set to orange
  • above 2500 – light is set to red
alias: update status light 1 with CO2 measurements
description: ""
trigger:
  - platform: state
    entity_id:
      - sensor.air_sensor_1_co2
condition: []
action:
  - if:
      - condition: numeric_state
        entity_id: sensor.air_sensor_3_co2
        above: 1000
        below: 1500
    then:
      - service: light.turn_on
        data:
          transition: 1
          brightness_pct: 50
          rgb_color:
            - 245
            - 224
            - 66
        target:
          device_id: **************
  - if:
      - condition: numeric_state
        entity_id: sensor.air_sensor_1_co2
        above: 1500
        below: 2500
    then:
      - service: light.turn_on
        data:
          transition: 1
          brightness_pct: 75
          rgb_color:
            - 245
            - 120
            - 66
        target:
          device_id: **************
  - if:
      - condition: numeric_state
        entity_id: sensor.air_sensor_1_co2
        above: 2500
    then:
      - service: light.turn_on
        data:
          transition: 1
          brightness_pct: 75
          rgb_color:
            - 255
            - 0
            - 0
        target:
          device_id: **************
  - if:
      - condition: numeric_state
        entity_id: sensor.air_sensor_1_co2
        below: 800
    then:
      - service: light.turn_off
        data:
          transition: 1
          brightness_pct: 100
        target:
          device_id: **************
mode: single

Conclusion

Now we have one status light on every desk which indicates when to get some fresh air. I hope this will improve the experience of working from home.