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Detailed Description:

Ensure the safety of your environment with the versatile and reliable MQ-9 Gas Sensor Module, a powerful solution for detecting both toxic and flammable gases. Unlike single-purpose sensors, the MQ-9 is uniquely designed to sense Carbon Monoxide (CO) as well as combustible gases like methane (CH4​) and LPG. This is achieved by using a high and low-temperature cycling method, allowing a single module to perform dual-gas detection.

The sensor's core is a tin dioxide (SnO2​) semiconductor material whose electrical conductivity changes in the presence of these gases. This change is then converted into a usable signal by the module's on-board circuitry. The versatility of the MQ-9 module is further enhanced by its dual output functionality. For simple, threshold-based alerts, it provides a digital output (DO), which can be easily configured using the on-board potentiometer to trigger a buzzer or LED when a preset gas concentration is detected. For more advanced projects, the analog output (AO) provides a continuous voltage signal that is directly proportional to the gas concentration, allowing for real-time monitoring and data logging.

Operating on a standard 5V DC supply, the MQ-9 module is fully compatible with popular microcontrollers like Arduino, ESP32, and Raspberry Pi. It is widely used in critical applications such as domestic and industrial gas leakage alarms, portable gas detectors, and smart home safety systems. With its robust performance, dual detection capability, and ease of use, the MQ-9 Gas Sensor Module is an indispensable component for any safety-conscious electronics project, offering peace of mind for both home and industrial environments.

The MQ-9 Gas Sensor Module is based on the MQ-9 semiconductor sensor, designed for the detection of CO (Carbon Monoxide), CH₄ (Methane), and LPG. It features dual output modes: an analog voltage output (A0) proportional to the gas concentration, and a digital output (D0) that activates when the concentration exceeds a user-defined threshold (set using the onboard potentiometer).

The sensor is suitable for home gas leak detectors, industrial safety systems, fire alarms, and IoT-based gas monitoring applications. It uses a heating element with a high/low heater voltage cycle for better selectivity between different gases.

Key Features:

• Detects Carbon Monoxide, Methane, and LPG gases

• High sensitivity to both CO (low temp) and CH₄/LPG (high temp)

• Dual output: Analog (A0) and Digital (D0)

• Onboard adjustable sensitivity potentiometer

• Compatible with Arduino, Raspberry Pi, ESP32, STM32

• Long life, low cost, and fast response time

• Ideal for IoT safety, smart homes, and gas warning systems

Technical Specifications:

How to Use:

1. Connect VCC to 5V, GND to GND, A0 to analog pin, and D0 to digital pin of your microcontroller.

2. Allow the sensor to preheat for 1–2 minutes for stable readings.

3. Use analogRead() to monitor gas levels continuously.

4. Use the potentiometer to set a threshold that triggers the digital output (digitalRead()).

For accurate gas type separation (CO vs LPG/CH₄), cycle heater voltage using a transistor or PWM control.

Arduino Sample Code (Basic Analog Output Monitoring):

#define MQ9_A0 A0

void setup() {
  Serial.begin(9600);
  pinMode(MQ9_A0, INPUT);
}

void loop() {
  int gasValue = analogRead(MQ9_A0);
  float voltage = gasValue * (5.0 / 1023.0);
  Serial.print("Gas Value: ");
  Serial.print(gasValue);
  Serial.print(" | Voltage: ");
  Serial.println(voltage, 2);
  delay(1000);
}

For best accuracy, use heater voltage switching (5V ↔ 1.5V) and calibrate against known ppm values.

Applications:

• Carbon monoxide and LPG leak detection systems

• Smart kitchens and gas safety appliances

• Industrial CH₄/CO monitoring

• IoT-based environmental and safety monitoring

• Fire alarms and HVAC gas sensors

• Breath detection or smoke sensing projects

• Educational and prototyping kits

Package Includes:

• 1 x MQ-9 Gas Sensor Module (CO/CH₄/LPG Detection)