{"id":69,"date":"2019-12-03T17:34:26","date_gmt":"2019-12-03T17:34:26","guid":{"rendered":"https:\/\/www.galagaking.org\/?p=69"},"modified":"2020-01-12T22:25:36","modified_gmt":"2020-01-12T21:25:36","slug":"esphome-co2-sensor","status":"publish","type":"post","link":"https:\/\/www.galagaking.org\/nl\/2019\/12\/03\/esphome-co2-sensor\/","title":{"rendered":"ESPHome \u2013 CO2 sensor"},"content":{"rendered":"

Following the ESPHome introduction<\/a>, we use the Winsen CO2 sensor to measure indoor CO2 level. For reference look at the datasheet<\/a>. <\/p>\n\n\n\n

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The sensor outputs the measured CO2 level in a PWM signal and a UART (serial) stream. We will use the UART interface in our example.<\/p>\n\n\n\n

Connection<\/h2>\n\n\n\n

We need four connections: power (5V – 150mA, GND, Rx and Tx). If you use the sensor with the JST6 cable you can solder plugs on these wires, or use Dupont crimp connectors. In the case you solder them you can connect Red \/ Black (Power) to one 2 pin female header, and Blue\/Green (Rx\/Tx) to another 2 pin header as shown.<\/p>\n\n\n\n

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Both on Wemos D1 and NodeMCU v2 the 5V power line (or Vin) is besides Ground (or ‘G’). Connect the power connector according to the colours (5V is Red, Ground is Black).<\/p>\n\n\n\n

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The Rx \/ Tx lines are connected to D1 (GPIO5), Green, Tx from module and D2 (GPIO4), Blue, Rx to module.<\/p>\n\n\n\n

YAML file<\/h2>\n\n\n\n

We will use ESPHome for the software. If you are not familair with ESPHome, have a look at our previous workshop<\/a>. Now we can add the sensor and the UART to the YAML file. First we will activate the uart. Feel free to use other pins if you use another ESP module.<\/p>\n\n\n\n

#D1: Green Wire \/ mhz19\n#D2: Blue Wire \/ mhz19\nuart:\n  rx_pin: D1\n  tx_pin: D2\n  baud_rate: 9600<\/pre>\n\n\n\n
We will add the MHZ sensor just before the BME280 sensor. There can only be one ‘sensor’ section! The sensor has also a temperature sensor, we will not use it here. More details on the ESPHome site<\/a>.<\/p>\n\n\n\n
sensor:\n  - platform: mhz19\n    co2:\n      name: \"MHZ19 CO2 Value\"\n      id: co2value\n    temperature:\n      name: \"MH-Z19 Temperature\"\n    automatic_baseline_calibration: false  \n    update_interval: 60s <\/pre>\n\n\n\n
If we upload our code, the ESP will initialize the sensor and read the values. They are also available at the webinterface and will be published on the MQTT chanel if you activated this.<\/p>\n\n\n\n
Add a display<\/h2>\n\n\n\n
To show the values on a small I2C display, we first have to connect the display to the I2C bus. That is a challenge, because the BME280 sensor also shares this bus. On a breadboard it is easy to connect both the Display and the BME280, if you want to solder you have to create a ‘splitter’. This can be done by soldering, or with crimp connectors.<\/p>\n\n\n\n
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