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MQ-3 Alcohol Gas Sensor

Pin Description

For MQ-3 Sensor Module

Pin Name



This pin powers the module, typically the operating voltage is +5V


Used to connect the module to system ground

Digital Out (DO)

You can also use this sensor to get digital output from this pin, by setting a threshold value using the potentiometer

Analog Out (AO)

This pin outputs 0-5V analog voltage based on the intensity of the gas

For MQ-3 Sensor


H -Pins

Out of the two H pins, one pin is connected to supply and the other to ground



The A pins and B pins are interchangeable. These pins will be tied to Supply voltage.



A pins and B pins are interchangeable. One pin will act as output while the other will be pulled to ground.


Features of MQ-3 Alcohol Sensor

  • Sensor Type - Semiconductor
  • Easy SIP header interface
  • Compatible with most of the microcontrollers
  • Low-power standby mode
  • Requires heater voltage
  • Good sensitivity to alcohol gas
  • Fast response and High sensitivity  
  • Long life and low cost
  • Requires simple Drive circuit

Specifications of MQ-3 Gas Sensor

  • Power requirements: 5 VDC @ ~165 mA (heater on) / ~60 mA (heater off)
  • Current Consumption: 150mA
  • DO output: TTL digital 0 and 1 ( 0.1 and 5V)
  • AO output: 0.1- 0.3 V (relative to pollution), the maximum concentration of a voltage of about 4V
  • Detecting Concentration: 0.05-10mg/L Alcohol
  • Interface: 1 TTL compatible input (HSW), 1 TTL compatible output (ALR)
  • Heater consumption: less than 750mW
  • Operating temperature: 14 to 122 °F (-10 to 50°C)
  • Load resistance: 200kΩ
  • Sensitivity S: Rs(in air)/Rs(0.4mg/L Alcohol)≥5
  • Sensing Resistance Rs: 2KΩ-20KΩ(in 0.4mg/l alcohol)
  • Dimensions: 32 x 22 x 16 mm

Alternative MQ-3 Gas Sensors

Sensor Name

Gas to measure


Methane, Butane, LPG, Smoke


Alcohol, Ethanol, Smoke


Methane, CNG Gas


Natural gas, LPG


LPG, butane


Carbon Monoxide


Hydrogen Gas


Carbon Monoxide, flammable gasses




Air Quality


Hydrogen Sulphide gas




Benzene, Toluene, Alcohol, Propane, Formaldehyde gas, Hydrogen


Methane, Natural Gas


Natural gas, Coal Gas


Alcohol, Ethanol, smoke


LPG, butane


Carbon Monoxide


Carbon Monoxide, flammable gas


MQ-3 Equivalent Sensors

MQ-2, MQ214 (detection of Methane), MQ303A


Brief Detail about MQ-3 Gas Sensor

MQ-3 module is suitable for detecting Alcohol, Benzine, CH4, Hexane, LPG, CO. Sensitive material of MQ-3 gas sensor is SnO2, which with lower conductivity in clean air. When the target alcohol gas exist, the sensor’s conductivity is more higher along with the gas concentration rising. MQ-3 gas sensor has high sensitity to Alcohol, and has good resistance to disturb of gasoline, smoke and vapor.

This sensor provides an analog resistive output based on alcohol concentration. When the alcohol gas exist, the sensor’s conductivity gets higher along with the gas concentration rising.

There is a resistance across an A and  B inside the sensor which varies on detection of alcohol. More the alcohol, the lower the resistance. The alcohol is measured by measuring this resistance. The sensor and load resistor form a voltage divider, and the lower the sensor resistance, the higher the voltage reading will be.

Internal Structure of MQ-3 Sensor

Structure and configuration of MQ-3 gas sensor is shown in the figure above for Configuration A or B, sensor composed by micro AL2O3 ceramic tube, Tin Dioxide (SnO2) sensitive layer, measuring electrode and heater are fixed into a crust made by plastic and stainless steel net. The heater provides necessary work conditions for work of sensitive components. The enveloped MQ-3 have 6 pin, 4 of them are used to fetch signals, and other 2 are used for providing heating current.


Applications of MQ-3 Gas Sensor

  • Gas level over-limit alarm
  • Breathalyser
  • Portable alcohol detector
  • Stand-alone/background sensing device
  • Environmental monitoring equipment


2D Model of MQ-3 Sensor (Configuration A and B)

2D Representation of MQ3 Sensor

Component Datasheet

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