Air Quality Sensor Module MQ-135
Air Quality Sensor Module MQ-135
Air Quality Sensor Module MQ-135
Air Quality Sensor Module MQ-135

Air Quality Sensor Module MQ-135

Sensors
DET665
Part.No: MQ-135
€4.95
In Stock
Immediate Dispatch
MQ-135 Air Quality Sensor Module detects benzene, alcohol, smoke and other harmful gases. Dual analog + TTL output, 5V operation, adjustable sensitivity — ideal for Arduino and microcontroller air quality projects.

 

The MQ-135 Air Quality Sensor Module (MPN: MQ-135) is a versatile gas detection module sensitive to benzene, alcohol, smoke, and sulfides. Operating at 5V DC, it provides both analog and digital (TTL) outputs, making it straightforward to integrate with any 5V microcontroller. As the concentration of detected gases increases, the analog output voltage rises proportionally — giving you a continuous, real-time air quality reading without complex calibration routines.

Key Features

  • Multi-gas Detection: Sensitive to benzene, alcohol, smoke, and sulfides → covers a wide range of indoor air quality threats
  • Dual Signal Output: Simultaneous analog (AO) and digital TTL (DO) outputs → connect to both analog ADC pins and digital IO pins
  • Analog Proportional Response: Output voltage increases with gas concentration → enables precise concentration monitoring
  • TTL Active-Low Output: DO goes LOW when threshold is exceeded → triggers interrupts or LEDs directly on any microcontroller IO port
  • Adjustable Sensitivity: On-board potentiometer for threshold tuning → customise the alarm point for your application
  • Fast Response & Recovery: Rapid reaction to gas changes → suitable for real-time monitoring systems
  • Signal Output Indicator: On-board LED indicates active digital output → instant visual feedback during testing

Pinout & Wiring

PINSymbolDescription
1VCCPower supply — connect to 5V DC
2GNDGround
3DODigital TTL output (active LOW when gas exceeds threshold)
4AOAnalog output — voltage rises with gas concentration

Wiring note: Connect VCC to 5V, GND to ground. Read AO on any ADC-capable pin (e.g., Arduino A0) for continuous concentration data. Connect DO to a digital IO pin to trigger alerts when the preset threshold is exceeded.

Compatibility

  • Arduino UNO / Nano / Mega: Fully compatible — 5V supply matches module operating voltage; read AO via analog pins and DO via digital pins directly.
  • ESP32 / Raspberry Pi (3.3V logic): Power the module from the 5V rail; use a voltage divider or logic-level shifter on the AO/DO lines to protect 3.3V GPIO pins.

Typical Applications

  • Indoor Air Quality Monitors: Detect elevated benzene or smoke levels in homes, offices, or classrooms and trigger ventilation or alarms.
  • DIY Smoke & Gas Alarm: Use the TTL output to drive a buzzer or LED warning system when gas concentration crosses a set threshold.
  • Arduino / ESP32 Environmental Logger: Log analog AO readings over time to track air quality trends and visualise data on a dashboard.
  • Industrial Safety Monitoring: Early warning for harmful gas accumulation in workshops or laboratories.
  • STEM / University Projects: Hands-on experiments in sensor calibration, ADC reading, and threshold-based control systems.

Technical Specifications

ParameterValue
InterfaceAnalog (AO) + Digital TTL (DO)
Operating VoltageDC 5V
Operating Current150 mA
Digital Output (DO)0.1V (LOW) / 5V (HIGH)
Analog Output (AO)0.1 – 0.3V (idle, increases with concentration)
TTL Output LogicActive LOW (signal valid when LOW)
Detected GasesBenzene, alcohol, smoke, sulfides
Sensitivity AdjustmentOn-board potentiometer
MPNMQ-135

FAQ

Q: Can I use the MQ-135 directly with an ESP32?
A: The module requires a 5V supply to heat the sensing element correctly. You can power it from a 5V rail, but the AO/DO outputs will be at 5V logic — use a voltage divider on those lines before connecting to ESP32's 3.3V GPIO to avoid damage.

Q: What does the analog output voltage represent?
A: The AO pin outputs a low voltage (~0.1–0.3V) in clean air. As gas concentration increases, the voltage rises. By reading this value with an ADC (e.g., Arduino analogRead()), you can monitor relative air quality changes in real time.

Package Contents: 1 × MQ-135 Air Quality Sensor Module

⚠ Note: The MQ-135 sensor element requires a warm-up period (typically several minutes) before readings stabilise. Allow adequate pre-heating time before relying on sensor data in your application.
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