The MQ-135 is a gas sensor module used for monitoring indoor air quality, detecting harmful gases like ammonia (NH₃), nitrogen oxides (NOx), benzene, alcohol, and smoke, offering both analog (voltage) and digital (threshold) outputs for microcontrollers like Arduino or Raspberry Pi. It works by changing its electrical conductivity as pollutant gas concentration rises, requiring a pre-heat time (around 48 hrs initially, but minutes for use) and a 5V supply, making it great for DIY environmental monitoring, alarms, and IoT projects.�
Operating Voltage is 5V
Detect/Measure NH3, NOx, alcohol, Benzene, smoke, CO2, etc.
Analog output voltage: 0V to 5V
Digital output voltage: 0V or 5V (TTL Logic)
Preheat duration 20 seconds
Can be used as a Digital or analog sensor
The Sensitivity of Digital pin can be varied using the potentiometer
The MQ-135 gas sensor senses the gases like ammonia nitrogen, oxygen, alcohols, aromatic compounds, sulfide and smoke.
The MQ-135 Gas sensors are used in air quality control equipments and are suitable for detecting or measuring of NH3, NOx, Alcohol, Benzene, Smoke, CO2. The MQ-135 sensor module comes with a Digital Pin which makes this sensor to operate even without a microcontroller and that comes in handy when you are only trying to detect one particular gas. If you need to measure the gases in PPM the analog pin need to be used. The analog pin is TTL driven and works on 5V and so can be used with most common microcontrollers.
Applications
Air quality monitor
Detection of harmful gases
detect domestic/Industrial air pollution
Portable air pollution detection
Used to detect leakage/excess of gases like Ammonia, nitrogen oxide, alcohols, aromatic compounds, sulfide and smoke.
