Khamis, Mei 09, 2019

How to Make an IoT Smoke Alarm With NodeMCU ESP8266

About Gas Sensor

The MQ2 is used in gas leakage detecting equipment in consumer and industry markets, this sensor is suitable for detecting CH4, Natural gas, LNG, avoid exposure to alcohol, cooking fumes, and cigarette smoke. The sensitivity can be adjusted by the potentiometer. Come with cables


Power supply: 5V
Interface type: Analog
Pin Definition: 1-Output 2-GND 3-VCC
High sensitivity to CH4, Natural gas
Small sensitivity to alcohol, smoke
Fast response
Stable and long life
Simple drive circuit
Size: 40x20mm

The MQ-2 sensor has 4 pins.

Pin-------------------------------------Wiring to Arduino Uno

A0-------------------------------------Analog pins

D0-------------------------------------Digital pins



How does it Work?

The voltage that the sensor outputs changes accordingly to the smoke/gas level that exists in the atmosphere. The sensor outputs a voltage that is proportional to the concentration of smoke/gas. You can use with Gas Lighter.

In other words, the relationship between voltage and gas concentration is the following:

The greater the gas concentration, the greater the output voltage
The lower the gas concentration, the lower the output voltage

The output can be an analog signal (A0) that can be read with an analog input of the Arduino or a digital output (D0) that can be read with a digital input of the NodeMCU ESP8266.

Tools and materials :
  • NodeMCU ESP8266
  • Sensor MQ-2  
  • Jumper female to male 

Drawing Circuits:


#define BLYNK_PRINT Serial
#include <ESP8266WiFi.h>
#include <BlynkSimpleEsp8266.h>
BlynkTimer timer;
char auth[] = " ***";
char ssid[] = "***";
char pass[] = "***";

int gas;    // Declare gas

void setup()
  Blynk.begin(auth, ssid, pass);
  // You can also specify server:
  //Blynk.begin(auth, ssid, pass, "", 80);
  //Blynk.begin(auth, ssid, pass, IPAddress(192,168,1,100), 8080);

void loop()

  if(gas>190)   // If gas more than 190
     digitalWrite(16,HIGH); // LED1 RED LAMP
     Blynk.notify("Gas Detected");

  if(gas<190)   // If gas less than 190
      digitalWrite(5,HIGH); // LED2 GREEN LAMP
    Blynk.virtualWrite(V1, gas); // Set V1 in Blynk Apps;;

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