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**MQ-135 Air Quality Gas Sensor Module**Monitor air quality with the MQ-135 sensor, perfect for detecting ammonia, NOx, alcohol, benzene, smoke, and COâ. Featuring dual outputs--analog (0-5V) and digital TTL--this versatile module is ideal for Arduino projects, smart ventilation, and indoor monitoring. **Key Features:**- Detects multiple gases for broad-spectrum monitoring.- Quick response and easy 4-pin installation.- Adjustable threshold for customizable detection.- Compatible with Arduino, ESP, Raspberry Pi, and more.**Specifications:**- Operating Voltage: 5V DC- Dimensions: 32 x 20 x 27 mm- Includes: 1x MQ-135 Module (No Arduino or cables)Maximize your air quality control today! Enjoy fast, free shipping and responsive support from Envistia Mall!
Electronics for IoT, Prototyping & DIY
**MQ-135 Air Quality Gas Sensor Module**Monitor air quality with the MQ-135 sensor, perfect for detecting ammonia, NOx, alcohol, benzene, smoke, and CO₂. Featuring dual outputs--analog (0-5V) and digital TTL--this versatile module is ideal for Arduino projects, smart ventilation, and indoor monitoring. **Key Features:**- Detects multiple gases for broad-spectrum monitoring.- Quick response and easy 4-pin installation.- Adjustable threshold for customizable detection.- Compatible with Arduino, ESP, Raspberry Pi, and more.**Specifications:**- Operating Voltage: 5V DC- Dimensions: 32 x 20 x 27 mm- Includes: 1x MQ-135 Module (No Arduino or cables)Maximize your air quality control today! Enjoy fast, free shipping and responsive support from Envistia Mall! MQ-135 NH₃ / NOx / Alcohol / Benzene / Smoke / CO₂ Air Quality Gas Sensor Detector Module
The MQ-135 gas sensor detector module is designed for air quality monitoring, detecting ammonia (NH₃), nitrogen oxides (NOx), alcohol, benzene, smoke, and carbon dioxide (CO₂). The module features dual signal outputs -- an analog output (0–5V) proportional to gas concentration and a digital TTL output with an adjustable threshold via the onboard potentiometer. With fast response, long service life, and a simple 4-pin interface, it\'s ideal for Arduino-based air quality projects, smart ventilation systems, and indoor environment monitoring.
⚠️ Important: The sensor element gets hot during operation -- do not touch the metal mesh cylinder while powered. Allow a 24–48 hour initial burn-in for best accuracy on first use; subsequent warm-ups take only 2–5 minutes. 🔧 How It Works
- The sensor\'s internal heater raises the tin dioxide (SnO₂) element to its operating temperature
- When target gas molecules (NH₃, NOx, alcohol, benzene, smoke, or CO₂) contact the heated surface, the sensor\'s electrical resistance decreases
- The onboard voltage divider converts the resistance change into an analog voltage (0–5V) on the AO pin -- higher concentration produces higher voltage
- The LM393 comparator compares the analog signal against the potentiometer threshold -- when exceeded, the DO pin goes HIGH and the DO LED illuminates
⚡ Key Features
- Air Quality Monitoring -- Detects NH₃, NOx, alcohol, benzene, smoke, and CO₂
- Broad-Spectrum Detection -- Responds to toxic gases, volatile organic compounds (VOCs), and smoke
- Dual Signal Output -- Analog (AO) and digital TTL (DO) outputs for flexible integration
- Adjustable Threshold -- Onboard potentiometer to set the digital output trigger level
- Indicator LEDs -- Power LED and DO status LED for visual response
- Fast Response & Recovery -- Quick detection and return to baseline
- Simple 4-Pin Interface -- VCC, GND, AO, DO -- no library required
- 5V Compatible -- Works directly with Arduino, ESP8266, and other 5V development boards
📐 SpecificationsOperating Voltage5V DCMax Power Consumption800 mW (160 mA at 5V)Detectable GasesNH₃, NOx, alcohol, benzene, smoke, CO₂Analog Output (AO)0V to ~5V (proportional to gas concentration)Digital Output (DO)TTL level -- LOW normally, HIGH when gas detectedThreshold AdjustmentOnboard potentiometerIndicator LEDsPower LED, DO (Digital Output) LEDDimensionsApprox. 32 × 20 × 27 mm (1.25 x 0.8 x 1.1 inches) L × W × HWeight~7 grams 📦 What\'s in the Box
- 1x MQ-135 Air Quality Gas Sensor Detector Module
Arduino, jumper wires, and USB cable are not included.
🔌 Compatible With
- Arduino (Uno, Mega, Nano, Pro Mini, and compatibles)
- ESP8266 and ESP32 development boards
- Raspberry Pi (with ADC module for analog reading)
- STM32, Teensy, and other 5V-compatible microcontrollers
🎯 Typical Applications
- Indoor air quality monitoring (homes, offices, classrooms)
- Smart ventilation and HVAC control
- Ammonia detection in agricultural and livestock facilities
- Solvent and VOC monitoring in workshops and labs
- Smoke detection as a secondary indicator
- CO₂ trend monitoring (general indication)
- Air quality dashboards and IoT data logging
- Smart home automation -- trigger alerts, fans, or air purifiers
- Educational and STEM projects
💡 Tip: The MQ-135 is a broad-spectrum air quality sensor -- it cannot distinguish between individual gas types on its own. For precise CO₂ measurement, pair it with a dedicated NDIR CO₂ sensor. For gas-specific detection, consider using it alongside other MQ-series sensors (MQ-2 for smoke, MQ-7 for CO, MQ-5 for natural gas) and comparing readings. ⚠️ Important Notes
- The sensor element gets hot during operation -- do not touch the metal mesh cylinder while powered
- Allow a 24–48 hour initial burn-in for best accuracy on first use
- Raw analog readings are not direct PPM values -- calibration against known concentrations is required for PPM conversion
- The sensor draws up to 160 mA -- use an external 5V supply if powering multiple sensors or experiencing unstable readings
- Temperature and humidity can affect sensor readings -- recalibrate periodically for best results
- Benzene is a known carcinogen -- do not intentionally expose yourself to benzene vapors for testing
- Keep the sensor away from direct airflow (fans, HVAC vents) that could dilute gas concentrations
🏪 About Envistia Mall
Envistia Mall is a US-based electronics retailer specializing in development boards, sensors, modules, and components for makers, engineers, and educators. We are committed to providing quality products with excellent customer service.
📦 Fast Free US Shipping | 🔄 Hassle-Free Returns | 📧 Responsive Customer Support
Visit our store for more gas sensor modules, Arduino-compatible sensors & development boards, and electronic components for your next project.
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