Interfacing Carbon Dioxide (CO2) Sensor with Arduino

Introduction

Carbon dioxide (CO2) is a colorless, odorless gas that is present in the atmosphere and is a byproduct of many human activities. With the increasing concern about climate change and global warming, it has become crucial to monitor the level of CO2 in the environment. One way to achieve this is by interfacing a CO2 sensor with an Arduino microcontroller, which can provide accurate readings of CO2 concentration in real-time.

In this article, we will discuss the process of interfacing a “CO2 sensor with an Arduino” and how it can be used to monitor CO2 levels.

What is Carbon Dioxide (CO2) Sensor?

A Carbon Dioxide (CO2) sensor is an electronic device that measures the level of carbon dioxide gas in the surrounding environment. The sensor typically consists of a sensing element, which is designed to detect the presence of CO2, and a signal processing circuit, which converts the sensor’s output into a usable electrical signal.

Hardware Components

To interface Carbon Dioxide (CO2) Sensor with Arduino, you’ll need the following hardware components to get started:

Components	Value	Qty
Arduino UNO	–	1
USB Cable Type A to B	–	1
DC Power for Arduino	–	1
CO2 Sensor	–	1
Jumper Wires	–	1

CO2 Sensor Pinout

Pin Name	Pin Description	Remarks
A	Analog Output	Analog Output proportional to the CO2 sensor.
+	Power supply – 5 V	You can use onboard 5 V to power the sensor
–	Ground	Common ground connections

CO2 Sensor Arduino Circuit

Make connections according to the circuit diagram given below.

Wiring / Connections

Arduino	CO2 Sensor
5V	VCC
GND	GND
A0	ANALOG OUT

Installing Arduino IDE

First, you need to install Arduino IDE Software from its official website Arduino. Here is a simple step-by-step guide on “How to install Arduino IDE“.

Code

Now copy the following code and upload it to Arduino IDE Software.

#define MG_PIN (A0)     //define which analog input channel you are going to use
#define BOOL_PIN (2)
#define DC_GAIN (8.5)   //define the DC gain of amplifier
#define READ_SAMPLE_INTERVAL (50)    //define how many samples you are going to take in normal operation
#define READ_SAMPLE_TIMES (5)     //define the time interval(in milisecond) between each samples in
                                                     //normal operation
#define ZERO_POINT_VOLTAGE (0.220) //define the output of the sensor in volts when the concentration of CO2 is 400PPM
#define REACTION_VOLTGAE (0.030) //define the voltage drop of the sensor when move the sensor from air into 1000ppm CO2
float CO2Curve[3]  =  {2.602,ZERO_POINT_VOLTAGE,(REACTION_VOLTGAE/(2.602-3))};
                                                     //two points are taken from the curve.
                                                     //with these two points, a line is formed which is
                                                     //"approximately equivalent" to the original curve.
                                                     //data format:{ x, y, slope}; point1: (lg400, 0.324), point2: (lg4000, 0.280)
                                                     //slope = ( reaction voltage ) / (log400 –log1000)
 
void setup()
{
    Serial.begin(9600);                              //UART setup, baudrate = 9600bps
    pinMode(BOOL_PIN, INPUT);                        //set pin to input
    digitalWrite(BOOL_PIN, HIGH);                    //turn on pullup resistors
 
   Serial.print("MG-811 Demostration\n");
}
 
void loop()
{
    int percentage;
    float volts;
 
    volts = MGRead(MG_PIN);
    Serial.print( "SEN0159:" );
    Serial.print(volts);
    Serial.print( "V           " );
 
    percentage = MGGetPercentage(volts,CO2Curve);
    Serial.print("CO2:");
    if (percentage == -1) {
        Serial.print( "<400" );
    } else {
        Serial.print(percentage);
    }
 
    Serial.print( "ppm" );
    Serial.print("\n");
 
    if (digitalRead(BOOL_PIN) ){
        Serial.print( "=====BOOL is HIGH======" );
    } else {
        Serial.print( "=====BOOL is LOW======" );
    }
 
    Serial.print("\n");
 
    delay(500);
}
 
float MGRead(int mg_pin)
{
    int i;
    float v=0;
 
    for (i=0;i<READ_SAMPLE_TIMES;i++) {
        v += analogRead(mg_pin);
        delay(READ_SAMPLE_INTERVAL);
    }
    v = (v/READ_SAMPLE_TIMES) *5/1024 ;
    return v;
}
 
int  MGGetPercentage(float volts, float *pcurve)
{
   if ((volts/DC_GAIN )>=ZERO_POINT_VOLTAGE) {
      return -1;
   } else {
      return pow(10, ((volts/DC_GAIN)-pcurve[1])/pcurve[2]+pcurve[0]);
   }
}

Code Explanation

This Arduino code defines several constants and sets up a CO2 sensor using an MG-811 sensor module. The code first sets the pin configuration for the analog input and the digital pin to be used for the sensor. The code also defines constants for the DC gain of the amplifier, the sample interval for reading the sensor, the zero point voltage, and the reaction voltage.

The setup function initializes the UART communication and sets up the digital pin for input with pullup resistors. The loop function reads the voltage from the sensor using the MGRead function and calculates the percentage of CO2 using the MGGetPercentage function. The loop function also checks the state of the digital pin and prints the readings to the serial monitor.

The MGRead function takes multiple samples of the analog input and calculates the average voltage. The MGGetPercentage function uses the voltage readings and the CO2Curve array to calculate the percentage of CO2 concentration in the air.

Overall, this code demonstrates how to interface a CO2 sensor with an Arduino and how to read and interpret the sensor data.

Applications CO2 Sensor

Here are some applications of Carbon Dioxide (CO2) sensors:

• Indoor air quality monitoring in homes, offices, and public buildings
• HVAC (heating, ventilation, and air conditioning) systems for climate control
• Industrial processes where the level of CO2 needs to be monitored for safety and efficiency reasons
• Greenhouses and indoor farming to optimize plant growth and health
• Environmental monitoring for research purposes
• Air quality monitoring in urban areas
• Automotive and transportation systems to monitor exhaust emissions
• Medical applications for monitoring respiratory function and anesthesia gases in operating rooms

Conclusion

Interfacing a CO2 sensor with an Arduino can provide a cost-effective and efficient way to monitor CO2 levels in the environment. By using this we can take steps to reduce the impact of human activities on the environment and help mitigate the effects of climate change. As we have seen, the process of interfacing a CO2 sensor with an Arduino is relatively simple and can be accomplished by following a few basic steps. We hope that this article has provided you with a clear understanding of how to interface a CO2 sensor with an Arduino.