Add support for the HC8 CO2 sensor

[ClarkAlmazan]

Describe the problem you have/What new integration you would like

I would like to see the HC8 CO2 sensor integrated. This sensor is almost the same as the MHZ19, but uses a different protocol. It's been reported previously on https://github.com/esphome/issues/issues/4534.

Please describe your use case for this integration and alternatives you've tried:

This is one of the NDIR-based CO2 sensors that are available for a very cheap price. Currently, it's already supported in Tasmota. I've tested their code for reading the CO2 values on an Arduino UNO R3 and I can confirm that it works.

I'm unaware of other functions besides reading the values.

Additional context

Blogpost from someone who found this sensor. Cached datasheet

[fanfaron2004]

hello ... i use the PWM output ...

I measure the pulsation time (x), and we can calculate the CO2 value: ppm = (1000x-2)*5

here is an ESPhome example

sensor:

• platform: pulse_width pin: GPIO19 name: "Co2" device_class: carbon_dioxide state_class: measurement filters:
  • lambda: !lambda |- if (x < 0.02) return {}; return round(((1000x)-2)5); unit_of_measurement: "ppm" update_interval: 60s

[ClarkAlmazan]

Hi @fanfaron2004, this looks kinda neat, definitely much simpler than what I had in mind. Never thought about using PWM, as I've never used it before. For this method, I'm assuming you only need 5V, GND, and the PWM pins connected, right?

For my own use, I made an esphome component, but honestly it's not very good so I don't think I want to make a pull request. I started off copying the mhz19 code, then just changed it to run like how the tasmota implementation did. It works but not without issues... You can see it here: https://github.com/ClarkAlmazan/esphome/commit/f751d198f07954478eb8664255f5dd9d7d0158a0

[Racer0412]

Hey @fanfaron2004.

Could you please share the code in a different format so it's easier to copy? That'd be nice. My ESPHome is throwing errors and due to my limited experience I'm not able to fix it on my own :/

Thanks a lot!

[IZZE2000]

FYI i asked Bing (GPT4) to fix the indentation and it worked out nicely!

sensor:
  platform: pulse_width
  pin: GPIO19
  name: "Co2"
  device_class: carbon_dioxide
  state_class: measurement
  filters:
    lambda: !lambda |-
      if (x < 0.02) return {};
      return round(((1000*x)-2)*5);
  unit_of_measurement: "ppm"
  update_interval: 60s

[alexschultze]

+1 For implementing this "C08" type of sensor protocol.