Ingo Lohs
Published © LGPL

Carbon Monoxide Gas Sensor MQ-7

The easy way - Pololu #1482

BeginnerProtip45 minutes28,963
Carbon Monoxide Gas Sensor MQ-7

Things used in this project

Hardware components

MQ-7
×1
Pololu Carrier for MQ Gas Sensors (Bare PCB Only)
×1
Resistor 10k ohm
Resistor 10k ohm
https://www.electronicsplanet.ch/Widerstand/10-k-Ohm-Widerstand-Farbcode.html
×1
Arduino Nano R3
Arduino Nano R3
×1
Breadboard (generic)
Breadboard (generic)
×1
Jumper wires (generic)
Jumper wires (generic)
3 pieces
×1

Software apps and online services

Arduino IDE
Arduino IDE

Story

Read more

Code

Analog Read Example code from Arduino IDE

C/C++
/*
  AnalogReadSerial

  Reads an analog input on pin 0, prints the result to the Serial Monitor.
  Graphical representation is available using Serial Plotter (Tools > Serial Plotter menu).
  Attach the center pin of a potentiometer to pin A0, and the outside pins to +5V and ground.

  This example code is in the public domain.

  http://www.arduino.cc/en/Tutorial/AnalogReadSerial
*/

// the setup routine runs once when you press reset:
void setup() {
  // initialize serial communication at 9600 bits per second:
  Serial.begin(9600);
}

// the loop routine runs over and over again forever:
void loop() {
  // read the input on analog pin 0:
  int sensorValue = analogRead(A0);
  // print out the value you read:
  Serial.println(sensorValue);
  delay(1);        // delay in between reads for stability
}

Practical Example

C/C++
/********************************************************************/
// First we include the libraries
#include <OneWire.h> 
#include <DallasTemperature.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27,16,2);  // set the LCD address to 0x27 for a 16 chars and 2 line display
/********************************************************************/
// Data wire is plugged into pin 2 on the Arduino 
#define ONE_WIRE_BUS 2 
/********************************************************************/
// Setup a oneWire instance to communicate with any OneWire devices  
// (not just Maxim/Dallas temperature ICs) 
OneWire oneWire(ONE_WIRE_BUS); 
/********************************************************************/
// Pass our oneWire reference to Dallas Temperature. 
DallasTemperature sensors(&oneWire);
/********************************************************************/ 


int thresholdMQ7 = 1000; // Threshold for Buzzer-Alarm - toxic Carbon Monixide Area
int Buzzer_PIN = 3;      // Buzzer connected to digital pin 13
int MQ7_PIN = A0;        // MQ7-Sensor to analog pin A0

void setup(void) 
{ 
 // start serial port 
 Serial.begin(9600); 
 Serial.println("Dallas Temperature IC Control Library Demo"); 
 // Start up the library 
 sensors.begin(); 

  lcd.init();                      // initialize the lcd 
  lcd.backlight();

  pinMode(Buzzer_PIN, OUTPUT);      // sets the digital pin as output
  pinMode(MQ7_PIN, INPUT);         // sets the analog pin as input
 
} 
void loop(void) 
{ 
 // call sensors.requestTemperatures() to issue a global temperature 
 // request to all devices on the bus 
/********************************************************************/
 Serial.print("Requesting temperatures..."); 
 sensors.requestTemperatures(); // Send the command to get temperature readings 
 Serial.println("DONE"); 
/********************************************************************/
 lcd.setCursor(0,0);
 lcd.print("Temp C | Monoxid");
 Serial.print("Temperature is: "); 
 Serial.println(sensors.getTempCByIndex(0)); // Why "byIndex"?  
 
 lcd.setCursor(2,1);
 lcd.print(sensors.getTempCByIndex(0));
   // You can have more than one DS18B20 on the same bus.  
   // 0 refers to the first IC on the wire 

 int sensorValueMQ7 = analogRead(MQ7_PIN);
 // print out the value you read:
 Serial.print("Carbon Monoxide: ");
 Serial.println(sensorValueMQ7);
 lcd.setCursor(11,1);
 lcd.print(sensorValueMQ7);

 if (sensorValueMQ7 >= thresholdMQ7) {
  digitalWrite(Buzzer_PIN, HIGH);   // sets the Buzzer ALARM on
 } else {
  digitalWrite(Buzzer_PIN, LOW);   // sets the Buzzer ALARM off
 }
 
 lcd.setCursor(0,1); // signals that temp update is in progress
 lcd.cursor_on();
 delay(1000); 
 lcd.cursor_off();
}

Credits

Ingo Lohs
182 projects • 198 followers
I am well over 50 years and come from the middle of Germany.
Contact

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