MQ3 SENSOR

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. The sensor could be used to detect alcohol with different concentration, it is with low cost and suitable for different application.

Working Principle

The MQ3 has an electrochemical sensor, which changes its resistance for different concentrations of varied gasses. The sensor is connected in series with a variable resistor to form a voltage divider circuit (Fig 1), and the variable resistor is used to change sensitivity. When one of the above gaseous elements comes in contact with the sensor after heating, the sensor’s resistance change. The change in the resistance changes the voltage across the sensor, and this voltage can be read by a microcontroller.

The voltage value can be used to find the resistance of the sensor by knowing the reference voltage and the other resistor’s resistance. The sensor has different sensitivity for different types of gasses.

Features :

High sensitivity to alcohol and small sensitivity to Benzine
Fast response and High sensitivity
Stable and long life
Simple drive circuit

Specifications :

Gas Detection Alcohol, Ethanol, Smoke

Circuit voltage 5V±0.1

Heating voltage 5V±0.1

Load resistance 200kΩ

Heater resistance 33Ω ± 5%

Using Temperature -10℃-50℃

Storage Temperature -20℃-70℃

Sensing Resistance 1MΩ- 8 MΩ (0.4mg/L alcohol )

Power requirements: 5 VDC @ ~165 mA (heater on) / ~60 mA (heater off) Interface: 1 TTL compatible input (HSW), 1 TTL compatible output (ALR) Operating temperature: 14 to 122 °F (-10 to 50°C)

Dimensions: 1.50 x 1.0 x 1.0 in (38.1 x 25.4 x 25.4 mm)

Link to datasheet :

Do’s and dont’s:

Do avoid the contact with water as Sensitivity of the sensors will be reduced when spattered or dipped in water.

Do avoid icing on sensor’s surface, otherwise sensing material will be broken and lost sensitivity.

Do avoid Continual vibration will result in sensors down-lead response then repture. In transportation or assembling line, pneumatic screwdriver/ultrasonic welding machine can lead this vibration.

Do not exposed to adverse environment for Long time.

Do Not use sensor for long time in high gas concentration, it will affect sensors characteristic.

Do not Exposed to High Corrosive gas, it will not only result in corrosion of sensors structure, also it cause sincere sensitivity attenuation.􀀃􀀃

Storing Instructions:

Storing temperature should not exceed 50 C.
Use a rigid box to store.
Use a covering to protect from environmental gases while not using the sensor.

Advantages:

➨It is mechanically very robust sensor.
➨It works well at constant high humidity condition.

Disadvantages:

➨It is susceptible to contaminants and changes due to environment conditions.
➨non-linear response affects sensor complexity.

Schematics:

Interfacing with Arduino

Arduino Code:

const int sensorPin = A0; //GAS sensor output pin to Arduino analog A0 pin

void setup()

{ Serial.begin(9600); //Initialize serial port – 9600 bps

}

void loop()

{ Serial.println(analogRead(sensorPin));

delay(1000); // Print value every 1 sec.

}

Applications:

Breathalyser.
Vehicel alcohol detector
Portable alcohol detector

FAQ’s:

Q1. Is it normal that the gas sensor becomes hot in the course of operating?

Ans. Don’t worry, it is normal. Because the sensitivity material in the sensor should be heated for operating.

Q2. What is the need of pre-heat?

Ans. The heater provides necessary work conditions for work of sensitive components.

Q3. What is the pre-heat time required for its functionality?

Ans. The pre-heat time for this sensor is of few minutes. In datasheet, it is given 48hr but that is for a stable precise reading. It can also used after few minutes of pre-heat.

Referral Links:

Documentation links :

3. http://rogerbit.com/wprb/wp-content/uploads/2017/01/mq3-1.pdf