CO2_Sensor_Forced_Recalibration_Code.ino

// DIY CO2 Sensor SCD-30 Forced Recalibration Code
// CC By-NC 2022 Eric & Brian Woo-Shem
/*
Info:
Code to quickly recalibrate a SCD-30 sensor using Arduino. If sensor is not returning values around 400-450ppm when outside, use this code to reset it.
Also disables automatic self-calibration because it has caused problems.
Afterward it will take measurements and display them to screen indefinitely so you can check your work. 
Does NOT log data. Does NOT use RTC.

LCD = Liquid Crystal Display (Screen)


Resources Used:
https://learn.adafruit.com/adafruit-scd30
*/
#include <Adafruit_SCD30.h> 
#include <LiquidCrystal.h>
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~// ^Import Packages^
LiquidCrystal lcd(9, 8, 5, 4, 3, 2); // Set LCD Screen pins
Adafruit_SCD30  scd30; // Define Sensor

/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
void setup() { // Start setup

  lcd.begin(16, 2); // Set size of LCD screen
  pinMode(6, OUTPUT); // Set what pin 6 does (output)
  pinMode(7, OUTPUT); // Set what pin 7 does (output)
  
  digitalWrite(7, HIGH); // Set LCD brightness, you can change it if you want to
  analogWrite(6, 120); // Setting LCD contrast, you can change it if you want to
  
  scd30.begin(); // Start CO2 Sensor
  
// Force sensor to grab a few measurements to deal with first value = zero and sensor startup time bug.
  int i = 1;
  while(i<4){
    if (scd30.dataReady()){ // If CO2 data
        if (!scd30.read()) //If probelm reading data
          {
            return; // Don't do the the following ↓↓↓
           }
        lcd.clear();
        lcd.setCursor(0,0); // Set LCD Screen cursor position
        lcd.print("Calibrating..."); // Write the time to LCD Screen 
        lcd.setCursor(0,1); // Set LCD Screen cursor position
        lcd.print("Co2: "+String(scd30.CO2)); // Write the CO2 level to the LCD Screen
    }
    i += 1;
  }
  delay(1000);

// Disable automatic self-calibration because it tends to make sensors get off over time
// Note: if set to true, self-calibration is enabled.
  scd30.selfCalibrationEnabled(false);

// Force recalibration to approximate current outdoor value
// ONLY DO THIS WHEN OUTSIDE AND SENSOR IS AWAY FROM PEOPLE, WIND, AND OTHER SOURCES OF ERROR
// Typical outdoor value is 410-440ppm. 
// Comment out to only disable self-calibration
  scd30.forceRecalibrationWithReference(425); //IMPORTANT CHANGE THIS VALUE TO YOUR EXPECTED VALUE

} // End setup
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/

void loop() {
  // Repeatedly read in values once the calibration is complete. So you can check the sensor if you have LCD connected.
  if (scd30.dataReady()){ // If CO2 data
    if (!scd30.read()) //If probelm reading data
      {
        return; // Don't do the the following ↓↓↓
       }
    lcd.clear();
    lcd.setCursor(0,0); // Set LCD Screen cursor position
    lcd.print("Calibration Done"); // Different first line message to indicate it is running calibration code.
    lcd.setCursor(0,1); // Set LCD Screen cursor position
    lcd.print("Co2: "+String(scd30.CO2)); // Write the CO2 level to the LCD Screen
  }
}