Description
The MQ-7 CO Carbon Monoxide Coal Gas Sensor Module is a low-cost, highly sensitive semiconductor gas detection board designed for monitoring carbon monoxide (CO) and coal gas in domestic, industrial, and portable gas detection applications. Built around the MQ-7 sensor with a tin dioxide (SnO₂) sensing layer, this module offers high sensitivity to CO while using a unique high-low temperature cycle to maintain reliable long-term performance . It is an ideal solution for household CO alarms, industrial gas leak detectors, and portable safety instruments.
At the heart of the module is the MQ-7 sensor element, whose conductivity increases as the concentration of CO rises. Unlike simple gas sensors, the MQ-7 employs a cycling heater method: it heats to 5.0V for 60 seconds to clean the sensing element, then drops to 1.5V for 90 seconds to detect CO . This high-low temperature cycle is critical for accurate and stable CO measurement. The module provides two independent outputs: an analog output (AO) that varies continuously with gas concentration, and a digital output (DO) that switches when the concentration exceeds a user-adjustable threshold set by the onboard potentiometer .
The module operates from 5V DC with a typical current consumption of approximately 150mA . It is compatible with Arduino, ESP32, and other 5V microcontrollers; Raspberry Pi users require an external ADC. The board features a compact 32 × 20mm form factor and an onboard LED indicator for power and digital output status .
Important Note: The MQ-7 requires a significant preheat time for stable operation. The sensor should be powered on for not less than 48 hours in clean air before initial calibration . After each power-up, allow adequate time for the heater to stabilize. Critical: Most standard MQ-7 breakout boards do not include the heater cycling circuit required for proper operation . You must either implement the 5V/1.5V heater cycle manually (using a PWM pin or external circuit) or modify the board. Without proper heater cycling, readings will be inaccurate. The sensor is not a calibrated industrial-grade detector and should not be used as a sole life-safety device. The sensor surface becomes hot during operation — avoid touching it. The module is not waterproof and should be kept dry.
Whether you are building a home CO alarm, an industrial safety monitor, or an educational sensor project, the MQ-7 module provides a reliable, affordable solution for carbon monoxide detection.
Features
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MQ-7 SnO₂ semiconductor sensor — High sensitivity to carbon monoxide (CO) and coal gas
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High-low temperature cycling — 5.0V heating (60s) for cleaning, 1.5V (90s) for CO detection
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Dual output — Analog (AO) for concentration trends, Digital (DO) for threshold alarms
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Adjustable threshold — Onboard potentiometer sets the digital output trigger point
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Wide detection range — 10–1000 ppm (standard); some variants up to 10,000 ppm
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5V operation — Compatible with Arduino, ESP32, and other 5V microcontrollers
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LED indicators — Power and digital output status feedback
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Compact form factor — 32 × 20mm PCB for easy integration
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Fast response — Quick detection of CO concentration changes
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Wide application range — Household CO alarms, industrial detectors, portable instruments
Technical Specifications
| # | Parameter | Specification |
|---|---|---|
| 1 | Sensor Model | MQ-7 (SnO₂ semiconductor) |
| 2 | Target Gas | Carbon Monoxide (CO) |
| 3 | Detection Range | 10 – 1000 ppm (standard) |
| 4 | Operating Voltage | 5V DC |
| 5 | Heater Voltage | 5.0V ± 0.2V (high) / 1.5V ± 0.1V (low) |
| 6 | Heater Power Consumption | ≤350mW |
| 7 | Output Type | Analog (AO) + Digital (DO/TTL) |
| 8 | Preheat Time | Not less than 48 hours |
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