The MQ-135 Gas Sensor Module is a versatile device used for monitoring air quality by detecting a wide range of gases such as ammonia (NH₃), sulfur dioxide (SO₂), carbon monoxide (CO), nitrogen oxides (NOx), benzene, alcohol, smoke, and carbon dioxide (CO₂). It is commonly used in both domestic and industrial environments for pollution detection and safety monitoring.
This module is based on a metal oxide semiconductor (MOS) sensing principle. It uses a sensing element made of SnO₂ (tin dioxide), which exhibits low conductivity in clean air. When target gases are present, the conductivity of the sensor increases proportionally with gas concentration. This change is converted into an electrical signal that represents the level of gas in the environment.
The MQ-series sensors include a built-in heating element that ensures proper operation at room temperature, improving sensitivity and responsiveness to various gases.
Working Principle
The MQ-135 sensor operates by heating its sensing element to enhance interaction with gas molecules. When these gases come into contact with the sensor surface, they alter its electrical resistance. As gas concentration increases, the resistance changes accordingly. This variation is then translated into analog and digital output signals, enabling easy measurement and monitoring.
Key Features
- Detects multiple gases: NH₃, SO₂, CO, NOx, CO₂, benzene, alcohol, and smoke
- Based on SnO₂ (tin dioxide) sensing technology
- Detection range: 10 to 1000 ppm
- Operating voltage: 2.5V to 5V DC
- Provides both analog and digital outputs (0V–5V TTL)
- Adjustable sensitivity via onboard potentiometer
- Built-in heater for improved sensing accuracy
- Signal output indicator LED
- Low-cost and suitable for hobby and industrial applications
- Durable design for long-term usage in indoor and outdoor environments
Applications
- Air quality monitoring systems
- Detection of harmful and toxic gases
- Domestic air pollution monitoring
- Industrial pollution detection
- Portable air quality measurement devices
Technical Specifications
- Operating voltage: 2.5V – 5V DC
- Current consumption: ~150 mA
- Output type: Analog and Digital (TTL logic)
- Gas detection range: 10–1000 ppm
Why Choose MQ-135?
The MQ-135 sensor offers a reliable and cost-effective solution for detecting harmful gases at relatively low concentrations. Its high sensitivity, ease of use, and compatibility with microcontrollers make it an excellent choice for IoT projects, environmental monitoring, and safety systems.
