CO2 Sensor

The Sensirion SCD30 is a high precision specialized NDIS CO2 sensor that can be used to monitor air quality.

Using this sensor in an ESPHome device illustrates just how easy and straight-forward it is to build such sensor devices.

The SCD30 is a highly sensitive device. Handle with care according to manufacturer guidelines, and do not touch the measuring tube.

Hardware Schematics

The SCD30 is a 3.3V device and uses a I2C interface to communicate with the microcontroller.

It is best used with its service board attached. The service board contains voltage regulators and level shifters to ensure that the sensor is protected from inappropriate voltages.

Translate To Configuration

The sensor uses the I2C interface so we need to tell ESPHome the I2C pins that the sensor is using.

The sensor itself is supported natively by ESPHome, and all that’s left to do is specify the update interval.

i2c:
  sda: GPIO21
  scl: GPIO22
  scan: False
  id: bus_a

sensor:
  - platform: scd30
    co2:
      name: "Workshop CO2"
      accuracy_decimals: 1
    temperature:
      name: "Workshop Temperature"
      accuracy_decimals: 2
    humidity:
      name: "Workshop Humidity"
      accuracy_decimals: 1
    temperature_offset: 1.5 °C
    address: 0x61
    update_interval: 60s
    

Make sure you choose a wise update interval. You don’t need to report CO2 values every second. In fact it would probably be sufficient to update the readings every 5 minutes. Longer update intervals reduce energy consumption but more importantly, increase the sensor life span.

Validation And Upload

Like always, after you saved your configuration and validated it, you upload it to your microcontroller by clicking the three-dot menu. Then click Install and Wirelessly.

The log already includes first readings. As always, after you uploaded the firmware, click STOP to close the terminal window, then go to the ESPHome dashboard and verify that your device is marked ONLINE.

Diagnostics

To verify correct functionality, in the Home Assistant side bar, click Developer tools, click the tab States, then click into the text box below Entity, and enter part of your sensor name.

If your sensor does not show up, you might have to add it to Home Assistant first. Check Notifications in the sidebar to see whether Home Assistant has auto-detected your device, and add it to Home Assistant. You now see the current readings, and (depending on the update interval you set) you can now see these values change over time.

Monitoring And Logs

Once the new sensor works fine, you can now add its entities (i.e. CO2 value, temperature, and humidity readings) to your Home Assistant dashboards and display these values i.e. as a gauge or a graph.

You don’t just get a momentary display but also a continuous monitoring and logging: when you click the sensor gauge, Home Assistant pulls the sensor history data and shows a graph.

Without diving too much into detail, all of this is highly customizable: you control the type and style of dashboard item, can define the timespan to show, and your ESPHome device configuration sets the update interval in which Home Assistant polls new sensor values.

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^{_{(content created Jul 01, 2024 - last updated Jul 12, 2024)}}