In commercial buildings and industries, fire alarm systems are quite popular, they usually include a cluster of sensors that continually monitor any building flame, gas, smoke, or fire and cause an alarm if they detect them. One of the easiest ways to detect fire, gas, and smoke is by utilizing a Flame sensor and MQ 2 Gas Sensor.
This article interfaces Flame Sensor and MQ 2 Gas Sensor with Arduino and learns about all the procedures needed to develop Arduino Fire Alarm System. The flame sensor module has a photodiode for light detection and an op-amp for sensitivity monitoring. It is used for fire detection and makes a HIGH signal. Arduino detects the signal and alerts the buzzer and LED by turning it on. The flame sensor utilized is a flame sensor based on IR.
The MQ 2 sensor has an electrochemical sensor that varies its resistance to different flammable gas concentrations. The sensor is connected to a voltage divider circuit in series with a variable resistor, and the variable resistor is used to change sensitivity. When flammable gaseous elements come into contact with the sensor, it is heated. As a result, the sensor’s resistance changes. The voltage across the sensor changes as the resistance changes and this value can be read by a microcontroller. Here Arduino read the value and turning on the buzzer and LED.
Components required the Arduino Fire Alarm
| Arduino Uno | × 1 | Amazon |
| Flame Sensor | × 1 | Amazon |
| MQ-2 Gas & Smoke Sensor | × 1 | Amazon |
| Breadboard | × 1 | Amazon |
| Jumper wires kit | × 1 | Amazon |
| LED and Resistor Kit | × 1 | Amazon |
| Buzzer | ×2 | Amazon |
| USB cable type A/B | × 1 | Amazon |
Software
Flame Sensor
The flame sensor module is a small electronic module capable of detecting a fire source or other light sources. This sensor basically detects light wave IR (Infrared) from a light source or from a fire flame between 760 nm – 1100 nm. The flame sensor has a high-speed and sensitive YG1006 photo-transistor sensor. The detecting range is 100 cm. The Flame sensor can output either a digital or analog signal. There are two types of IR Infrared Flame Sensor Modules on the market: one with three pins (D0, Gnd, Vcc) and one with four pins (A0, D0, Gnd, Vcc), both of them can be used with Arduino and other microcontroller boards.
This sensor has a potentiometer, a 10k preset. Adjust the sensitivity of the flame sensor by rotating the preset knob. The Flame Sensor sensitivity will increase if the preset knob rotates clockwise. The sensitivity of the Flame sensor will decrease if it rotates counter-clockwise.
Application
- Fire detection
- Use in Fire fighting robot
- Fire alarm
Flame Sensor Specifications
| Operating voltage | 3.3V – 5V |
| Operating current consumption | 15mA |
| Spectrum range | 760nm ~ 1100nm |
| Detecting range | 100 cm |
| Sensor type | YG1006 Photo Transistor |
| Sensitivity | Adjustable via potentiometer |
| Detection angle | 0 – 60 degree |
| Operating temperature | -25℃ ~ 85℃ |
| PCB Size | 3cm X 1.6cm |
| Cost | Check price |
For more information, you can check out the flame sensor datasheet below:
MQ 2 Gas Sensor
MQ-2 sensitive gas sensor material is SnO2, which has a lower clean air conductivity. The conductivity of the sensor increases with the increase of the gas concentration when the target inflammable gas is present. Users can convert the change of conductivity by a single circuit to the corresponding gas concentration output signal.
The MQ-2 gas sensor is highly propane-smoke-sensitive and can well detect gas and other flammable steam. It’s cheap and suitable for various The MQ-2 gas sensor is highly propane-smoke-sensitive and can well detect gas and other flammable steam. It’s cheap and suitable for various applications of flammable gas detection.
- Wide range good sensitivity to Combustible gases
- High sensitivity to LPG, Propane and Hydrogen
- Long life and low cost
- Simple drive circuit
Application
- Domestic gas leakage detector
- Industrial Combustible gas detector
- Portable gas detector
- Safety of home
- Control of air quality
- Measurement of gas level
MQ 2 Gas Sensor Specifications
| Operating voltage | 4.5V – 5.V |
| Sensor Type | Semiconductor |
| Sensitivity | Adjustable via potentiometer |
| Gas to measure | LPG, i-butane, propane, methane, alcohol, Hydrogen, smoke |
| Detection range | 300～10000ppm (flammable gas) |
| Cost | Check price |
For more information, you can check out the MQ 2 Gas Sensor datasheet below:
Arduino Fire Alarm Schematics
Flame Sensor Connections
| Flame Sensor | Arduino |
| VCC | 5 V |
| GND | GND |
| D0 | Digital pin 2 |
MQ 2 Gas Sensor Connections
| MQ 2 Gas Sensor | Arduino |
| VCC | 5 V |
| GND | GND |
| A0 | A0 |
LED and Buzzer Connections
| LED and Buzzer | Arduino |
| Green LED | Digital Pin 8 |
| MQ 2 Gas Sensor Red LED | Digital Pin 3 |
| Flame Sensor Red LED | Digital Pin 4 |
| MQ 2 Gas Sensor Buzzer | Digital Pin 5 |
| Flame Sensor Buzzer | Digital Pin 6 |
Arduino Fire Alarm Code
By clicking the button in the top right corner of the code field, you can copy the code. Copy and paste it into Arduino IDE.
/*
www.arduinopoint.com
Fire Alarm System
*/
int redLed1 = 3;
int redLed2 = 4;
int greenLed = 8;
int buzzer1 = 5; //PWM (~) pin
int buzzer2 = 6; //PWM (~) pin
int gasPin = A0;
int flamePin = 2;
// Your threshold value
int gasSensorThres = 400;
void setup() {
pinMode(redLed1, OUTPUT);
pinMode(redLed2, OUTPUT);
pinMode(greenLed, OUTPUT);
pinMode(buzzer1, OUTPUT);
pinMode(buzzer2, OUTPUT);
pinMode(gasPin, INPUT);
pinMode(flamePin, INPUT);
Serial.begin(9600);
}
void loop() {
int gasSensor = analogRead(gasPin);
int flameSensor = digitalRead(flamePin);
Serial.print("gasPin Value: ");
Serial.println(gasSensor);
Serial.print("flamePin Value: ");
Serial.println(flameSensor);
delay(1000);
if (gasSensor > gasSensorThres && flameSensor==LOW){
digitalWrite(redLed1, HIGH);
tone(buzzer1, 5000); //the buzzer sound frequency at 5000 Hz
digitalWrite(redLed2, HIGH);
tone(buzzer2, 5000); //the buzzer sound frequency at 5000 Hz
digitalWrite(greenLed, LOW);
}
else if (gasSensor > gasSensorThres)
{
digitalWrite(redLed1, HIGH);
tone(buzzer1, 5000); //the buzzer sound frequency at 5000 Hz
digitalWrite(redLed2, LOW);
noTone(buzzer2);
digitalWrite(greenLed, LOW);
}
else if (flameSensor==LOW){ // HIGH MEANS NO FLAME
digitalWrite(redLed1, LOW);
noTone(buzzer1);
digitalWrite(redLed2, HIGH);
tone(buzzer2, 5000); //the buzzer sound frequency at 5000 Hz
digitalWrite(greenLed, LOW);
}
else
{
digitalWrite(redLed1, LOW);
digitalWrite(redLed2, LOW);
noTone(buzzer1);
noTone(buzzer2);
digitalWrite(greenLed, HIGH);
}
}Result
You should see your LED and Buzzer turn on when the sensor detects a fire, flammable gas, or smoke. If you cannot see the desired output, ensure the circuit has been properly assembled, and verified, and uploaded the code to your board.
