MQ-3 Alcohol Gas Sensor

Pin Description

For MQ-3 Sensor Module

Pin Name	Description
VCC	This pin powers the module, typically the operating voltage is +5V
GND	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

1	H -Pins	Out of the two H pins, one pin is connected to supply and the other to ground
2	A-Pins	The A pins and B pins are interchangeable. These pins will be tied to Supply voltage.
3	B-Pins	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
MQ-2	Methane, Butane, LPG, Smoke
MQ-3	Alcohol, Ethanol, Smoke
MQ-4	Methane, CNG Gas
MQ-5	Natural gas, LPG
MQ-6	LPG, butane
MQ-7	Carbon Monoxide
MQ-8	Hydrogen Gas
MQ-9	Carbon Monoxide, flammable gasses
MQ131	Ozone
MQ135	Air Quality
MQ136	Hydrogen Sulphide gas
MQ137	Ammonia
MQ138	Benzene, Toluene, Alcohol, Propane, Formaldehyde gas, Hydrogen
MQ214	Methane, Natural Gas
MQ216	Natural gas, Coal Gas
MQ303A	Alcohol, Ethanol, smoke
MQ306A	LPG, butane
MQ307A	Carbon Monoxide
MQ309A	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.

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)