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The MQ135 module is a gas sensor built for air quality monitoring, with high sensitivity to ammonia, sulfide and benzene vapor, and additional sensitivity to smoke and other harmful gases. It provides both a digital output (TTL, through the DOUT pin) for a simple threshold-based trigger, and an analog output (through the AOUT pin) for reading a more graduated sense of gas concentration, giving flexibility depending on whether a project needs a simple alarm trigger or genuinely measured readings.
Its tested detection range spans 10 to 1000ppm, and the sensor is described as suited to family and surrounding environment noxious gas detection, applying to ammonia, aromatics, sulfur and benzene vapor specifically, which points to household air quality monitoring and general environmental sensing as its main use case.
It runs on a 5V DC working voltage with a working current of 150mA, and needs a preheat time of over 20 seconds before readings stabilize, which is typical of this class of gas sensor and comes from the heating element inside that needs to reach a stable operating temperature before the sensing element responds accurately. Physical size is compact, at 32mm x 22mm x 27mm high.
Because gas sensors like the MQ135 respond to a mix of gases rather than a single specific one, it's best used as a general air-quality indicator rather than a precise measurement of any one gas concentration, and calibration against a known reference is advisable if more accurate readings are needed for a specific application.
Hobbyists building a home air quality monitor, a basic smoke or gas alarm, or an environmental sensing project that needs a general sense of air quality rather than one specific gas's concentration will find the MQ135 a practical, low-cost starting point.
Ammonia, sulfide, benzene vapor, smoke and other harmful gases.
Both a digital (TTL) output and an analog output.
Over 20 seconds of preheat time before stable readings.
5V DC.
10 to 1000ppm.
| Brand | Generic |
|---|---|
| Measurement Target | NH3, Sulfides, Benzene, Smoke |
| Output Signal | Digital + Analog |
| Selling unit | PCS |
