These gas sensor can be easily interfaced with Microcontrollers, Arduino Boards, Raspberry Pi. You may also use a comparator to convert analog output to digital and a preset can be used along with it to adjust sensitivity.

✍ Gas Sensor MQ-2
Sensitive Smoke & Flammable Gases
Detect range concentrations from 300 to 10,000 ppm.
The sensitive material used for this sensor is SnO2, whose conductivity is lower in clean air. This sensor has high sensitivity to Hydrogen, Propane, LPG, Methane and other combustible steams. This can be used to detect gas leakage in industries and houses.

✍ Gas Sensor MQ-3
Sensitive Alcohol Gas for Breathalyzer
Detect range 0.05 mg/L to 10 mg/L. The sensitive material used for this sensor is SnO2, whose conductivity is lower in clean air. It has high sensitivity to alcohol and has a good resistance to disturbances due to smoke, vapor and gasoline.

✍ Gas Sensor MQ-4
Sensitive Methane, CNC Gases
Detect range 200 to 10,000 ppm. It has also sensitivity to propane and butane gases.

✍ Gas Sensor MQ-5
Sensitive Natural Gas, LPG Coal, H2, CH4, CO, Alcohol
Detect range 200 to 10,000 ppm. It has also some sensitivity to smoke and alcohol.

✍ Gas Sensor MQ-6
Sensitive LPG, Butane, Propane Gases
Detect range 200 to 10,000 ppm. It has also some sensitivity to smoke and alcohol.

✍ Gas Sensor MQ-7
Sensitive Carbon Monoxide Gas
Detect range 20 to 2,000 ppm, high sensitivity to carbon monoxide, and stable and long-life span.

✍ Gas Sensor MQ-8
Sensitive Hydrogen Gas
Detect range 100 to 10,000 ppm

✍ Gas Sensor MQ-9
Sensitive Carbon Monoxide (CO) & Flammable Gas
Detect range 100 to 10,000 ppm. It has also some sensitivity to Carbon Monoxide, Methane and LPG

✍ Air Quality Sensor MQ-135
Can detect the presence of Ammonia (NH3), Mono-nitrogen oxides (NOx), Alcohol, Benzene, Smoke, Carbon-dioxide (CO2) etc. This module is commonly used as an Air Quality Sensor as it has good sensitivity to harmful gases in wide range. The sensitive material used for this sensor is SnO2, whose conductivity is lower in clean air. It’s conductivity increases as the concentration of sensing gases increases.

#Smoke, Flammable, Alcohol, Methane, CNC, Natural, LPG, Butane, Carbon Monoxide, Hydrogen for Arduino Raspberry

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▼ Applications
Domestic gas leakage detector
Industrial combustible gas detector
Portable gas detector

▼ Specifications
Operating Voltage: DC 5V
Analog Output (AO): 0~5V analog output voltage
Digital Outout (DO): 0V or 5V output
Configuration: Through Potentiometer (adjusts the output level transition)
Preheat Duration: 20s
Weight: 5g
Dimensions: 23 x 19 x 19 mm