Item specifics
Description
MQ Series Gas Sensor Kit Product Overview
The MQ Series Gas Sensor Kit includes 9 of the most commonly used gas sensor modules: MQ-2 (smoke), MQ-3 (alcohol), MQ-4 (methane), MQ-5 (LPG/natural gas), MQ-6 (isobutane/propane), MQ-7 (carbon monoxide), MQ-8 (hydrogen), MQ-9 (CO/combustible gas), and MQ-135 (air quality). Each module uses a high-quality metal oxide semiconductor gas sensing element with high sensitivity, fast response, long life, and simple circuitry. Outputs include analog voltage (AO) and digital TTL level (DO) with adjustable threshold. Operating at 5V, they connect directly to Arduino, ESP32, STM32, etc. Ideal for home gas alarms, industrial leak detection, air quality monitoring, alcohol detection, and more.
MQ Series Gas Sensor Kit Core Features
Complete Coverage of 9 Common Gases： MQ-2 (smoke/LPG/propane/hydrogen), MQ-3 (alcohol/ethanol), MQ-4 (methane/CNG), MQ-5 (LPG/natural gas/town gas), MQ-6 (isobutane/propane), MQ-7 (CO), MQ-8 (hydrogen), MQ-9 (CO/combustible gas), MQ-135 (ammonia/benzene/smoke/CO2 for air quality)
Dual Output Signals： Each module provides AO (analog 0-5V) and DO (digital TTL, threshold adjustable via potentiometer) for both precise concentration measurement and simple on/off alarm
Adjustable Sensitivity： Onboard blue potentiometer per module sets DO trigger threshold for different environments
Heater Driver Circuit： Integrated heating circuit ensures fast stabilization, response time typically <10 seconds
Wide Voltage Compatibility： 5V DC operation, directly compatible with 5V microcontrollers
Clear Indicators： Power LED (on when powered) and DO LED (lights when DO is low)
Standard Interface： 4-pin header (VCC, GND, DO, AO) with 2.54mm pitch for easy wiring
Easy Mounting： 3mm mounting holes for secure installation on boards or enclosures
Multiple Applications： Covers home gas alarms, industrial safety, alcohol testing, air quality monitoring, fire detection
Cost-Effective Kit： Get 9 sensors in one package, cheaper than buying individually, ideal for learning, R&D, and stocking
MQ Series Gas Sensor Kit Applications
Home Safety： Natural gas/LPG leak alarm, smoke/fire alarm, CO poisoning prevention
Alcohol Detection： Breathalyzer, drunk driving simulation devices
Industrial Safety： Methane detection in mines, chemical plant leak monitoring, gas station safety
Environmental Monitoring： Indoor air quality (VOCs/harmful gases), HVAC integration
Maker & Education： Arduino/ESP32 gas sensing experiments, smart home projects, graduation designs
Fire Warning： Smoke detection for early fire alert
MQ Series Gas Sensor Kit Key Advantages
One Kit Covers Most Common Gases： From flammable to toxic to air quality – 9 sensors meet most home and industrial needs, avoiding piecemeal purchases
Dual Output for Flexible System Integration： Analog output for precise concentration (ADC), digital output for direct relay/buzzer triggering
Independent Sensitivity Adjustment： Potentiometer on each module sets DO threshold to prevent false alarms from background gases
Plug-and-Play Integration： Modules come with pre-soldered headers, 4-wire connection to MCU – abundant Arduino libraries and examples
Fast Response & Recovery： High-quality sensing elements, response typically <10 sec after warm-up, suitable for real-time monitoring
Excellent Value： Kit price much lower than individual purchases – perfect for beginners, labs, maker spaces, competition teams
Modular Design for Easy Maintenance： Replace only the failed sensor, not the whole set
Widely Compatible： Standard MQ series pinout, interchangeable with common modules
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FAQ:
What is the MQ series 9‑in‑1 gas sensor kit and which sensors are included?
The kit contains nine MQ gas sensor modules, each designed to detect specific gases using a metal‑oxide semiconductor (MOS) sensing element. The included modules are: MQ‑2 (smoke, LPG, propane, hydrogen, methane), MQ‑3 (alcohol, ethanol), MQ‑4 (methane, natural gas), MQ‑5 (LPG, natural gas, town gas), MQ‑6 (LPG, propane), MQ‑7 (carbon monoxide), MQ‑8 (hydrogen), MQ‑9 (carbon monoxide, combustible gases), and MQ‑135 (air quality — ammonia, benzene, sulfide, smoke). All modules operate at 5 V, provide analog output (0–5 V), and most also have a digital (TTL) output with a threshold adjustment potentiometer.
How do I connect an MQ sensor module to Arduino or ESP32?
Wiring is straightforward. Connect VCC → 5 V, GND → GND, A0 (analog output) → any analog input pin (e.g., A0 on Arduino). If you want to use the digital output, connect D0 → any digital input pin. For ESP32 (3.3 V logic), the analog output can still be read directly because the ADC is usually 0–3.3 V, but a level shifter is recommended for the digital pin, or you can set the DO threshold within the 3.3 V range using the onboard potentiometer. A standard Arduino sketch simply reads analogRead(A0) to get the gas concentration value.
What is the preheat (warm‑up) time for MQ sensors, and why is it necessary?
MQ sensors require a preheat time to allow the internal heater to reach the proper operating temperature and for the sensing resistance to stabilize. For most MQ sensors (MQ‑2, 3, 4, 5, 6, 8, 135), the initial warm‑up is 24–48 hours for first use and 2–5 minutes for subsequent uses. MQ‑7 and MQ‑9 use a heating cycle (high/low temperature) and need about 2–3 minutes to stabilize during each power‑on. Never skip the warm‑up; readings taken before stabilization will be inaccurate.
What gases does each MQ sensor specifically detect?
MQ‑2: Smoke, LPG, propane, hydrogen, methane, alcohol — a general combustible gas sensor.
MQ‑3: Mainly alcohol and ethanol, commonly used in breathalyzers.
MQ‑4: Methane (CH₄) and natural gas.
MQ‑5: LPG, natural gas, town gas; good for domestic gas leak detection.
MQ‑6: LPG, iso‑butane, propane; highly sensitive to LPG.
MQ‑7: Carbon monoxide (CO) only; uses a high‑low heating cycle for selective CO sensing.
MQ‑8: Hydrogen (H₂); also responds to alcohol and LPG but optimized for H₂.
MQ‑9: Carbon monoxide and combustible gases (methane, LPG); also uses cyclic heating.
MQ‑135: Air quality — detects ammonia (NH₃), benzene, sulfide, smoke, and other harmful gases.
How do I interpret the analog output voltage and convert it to gas concentration (ppm)?
The analog output ranges from 0 V to 5 V, where higher voltage = higher gas concentration. To convert to ppm, you must use the sensitivity curve provided in each sensor’s datasheet. The relationship is non‑linear: Rs/R₀ = a × (ppm)^b, where R₀ is the sensor resistance in clean air and Rs is the resistance in the target gas. The value R₀ must be measured during calibration in clean air. Most hobby projects use the raw ADC value or a simple linear scaling for threshold detection, rather than calculating exact ppm. For precise ppm, a known calibration gas is required.
What is the digital (TTL) output on the MQ modules and how do I set the threshold?
Most modules include a comparator (LM393) that generates a digital output (D0). When the gas concentration exceeds a set threshold, D0 goes LOW (0 V) and the onboard LED lights up. You adjust the threshold using the onboard potentiometer: turn clockwise to raise the trigger level (needs higher concentration), counter‑clockwise to lower it. To set it, expose the sensor to the desired gas level and slowly turn the pot until the LED just turns on. The digital output is ideal for simple alarm circuits where you only need a yes/no detection.
Why do MQ‑7 and MQ‑9 require a special heating cycle? How do I implement it in code?
MQ‑7 and MQ‑9 use a cyclic heating method for improved selectivity: high temperature (5 V) for 60 s to burn off contaminants, then low temperature (1.4 V) for 90 s to measure the target gas. This is typically done by toggling the heater voltage using a transistor (e.g., 2N2222) or a dedicated driver circuit controlled by an Arduino PWM pin. In code, you use a state machine that switches between the high and low heating phases. Some modules simplify this by providing a dedicated driver, but the raw MQ‑7/MQ‑9 sensors require you to manage the cycle yourself for correct readings.
How do I calibrate the MQ‑135 for CO₂ or air quality monitoring?
MQ‑135 is commonly calibrated for CO₂ or general air quality. The process: first, run the sensor in clean, fresh air for at least 24 hours. Measure the analog value and calculate R₀ = Rs / ratio_from_datasheet. The datasheet provides a curve of Rs/R₀ vs. ppm for various gases. For hobby use, a common method is to assume ~400 ppm CO₂ in clean outdoor air and use the corresponding Rs/R₀ value to determine R₀. Then, in operation, measure Rs, compute Rs/R₀, and look up the ppm from the curve. Many Arduino libraries simplify this to an estimated CO₂ concentration.
Which MQ sensor should I choose for my specific project?
• Smoke/fire detection: MQ‑2.
• Alcohol breathalyzer: MQ‑3.
• Domestic gas leak (methane/LPG): MQ‑4 or MQ‑5.
• LPG/propane leak detection: MQ‑6.
• Carbon monoxide alarm: MQ‑7.
• Hydrogen gas detection: MQ‑8.
• Combustible gases and CO: MQ‑9.
• General indoor air quality (VOCs, ammonia, benzene): MQ‑135.
If you need to cover multiple gases, you can combine several sensors. The kit lets you experiment with all types before designing a final product.
What are the most typical applications of the MQ series sensor kit?
The kit is widely used in IoT air quality monitors, gas leak alarms, smoke detectors, breath alcohol testers, mine safety devices, smart kitchen hoods, and environmental monitoring stations. Because each sensor module provides both analog and digital outputs, they are extremely popular in Arduino and Raspberry Pi projects, university labs, and rapid prototyping of safety devices.