MQ-4 Methane Gas Sensor
Overview
The Boardoza MQ-4 is a specialized electrochemical sensing module engineered for the reliable detection of Methane (CH₄) and Compressed Natural Gas (CNG) in ambient environments. Built around a robust metal-oxide semiconductor (MOS) chemiresistor, this sensor exhibits high sensitivity to methane concentrations ranging from 200 to 10000 ppm, making it a critical component for gas leak detection, industrial safety monitoring, and domestic air quality systems.
The module simplifies the integration of the raw MQ-4 sensor by providing onboard signal conditioning circuitry, offering both analog and digital output interfaces for seamless connectivity with modern microcontrollers.
Core Technical Specifications
The module is defined by the following operational parameters:
Target Gas: Optimized for Methane (CH₄) and Natural Gas (CNG) detection.
Detection Range: Capable of sensing concentrations between 300 ppm and 10000 ppm.
Sensing Architecture: Metal-Oxide Semiconductor (SnO₂) chemiresistor, where conductivity increases in the presence of target combustible gases.
Operating Voltage: designed for standard 5V DC supply rails to power the internal heating element.
Heater Consumption: approximately 150mA, required to maintain the sensing element at optimal catalytic temperature.
Response Time: Fast response (< 10s) suitable for real-time safety alerts.
Sensitivity Adjustment: Features an onboard precision potentiometer for calibrating the digital trigger threshold.
Key Engineering Features
Dual-Signal Output Architecture
To maximize versatility, the breakout board provides two distinct output modes:
Analog Output (A0): Delivers a continuous voltage signal proportional to the gas concentration. This allows for precise ppm estimation when coupled with an MCU's Analog-to-Digital Converter (ADC).
Digital Output (D0): Provides a simple TTL logic signal (High/Low) based on a pre-set threshold. This is ideal for standalone alarm systems where a microcontroller might be overkill or for triggering interrupt-based safety shutdowns.
Integrated Comparator Circuitry
The digital output stage is driven by an onboard LM393 comparator. This integrated circuit compares the analog sensor voltage against a reference set by the onboard potentiometer, providing a clean, hysteresis-free digital signal for robust alarm triggering without software debouncing.
Industrial-Grade Stability
The MQ-4 sensor element is known for its long-term stability and resistance to alcohol and smoke interference, ensuring a low false-positive rate in specific methane detection applications compared to general-purpose combustible gas sensors.
Hardware Interface and Signal Mapping
The module interfaces via a standard 4-pin header, clearly labeled for rapid prototyping:
Power Terminals
VCC: Positive supply input. Must be connected to a stable 5V source to ensure consistent heater performance.
GND: Common system ground.
Signal Outputs
A0 (Analog Out): The primary measurement pin. Output voltage increases as gas concentration rises.
D0 (Digital Out): The threshold trigger pin. Logic Low (0V) typically indicates gas presence exceeding the calibrated limit (adjustable via potentiometer).
Applications
Domestic Safety: Leak detectors for residential natural gas pipelines and stoves.
Industrial Monitoring: Methane concentration logging in coal mines or waste management facilities.
Portable Gas Analyzers: Handheld sniffers for locating pipe fractures.
Smart HVAC: Ventilation control based on indoor air quality metrics.
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