Breathalyzer Made from Interfacing Arduino and MQ-3

The project illustrates how an Arduino board was interfaced with MQ-3 Alcohol Gas Sensor to create the Breathalyzer.

One ADC input of Arduino is required to obtain the simple connection of the sensor. The output voltage changes depend on the amount of Alcohol Gas in the breath. A bar consisting of 10 LEDs is used to interpret these voltage changes. The LEDs come in green, yellow and red with a dimension of 10 × 5mm. To calibrate the MQ-3 sensor, a 100KOhm potentiometer is used. The LEDs were connected in sequence in order to function properly as it uses the digital Pins 2 to 11. For each LED, a resistor between 220Ohms and 470Ohms is used.

One of the H pin is connected to +5V supply and the other one to Ground in order to connect the sensor. An external power supply is used so that the current will not be too much for the Arduino.

The MQ-3 Gas sensor has high sensitivity to alcohol and small sensitivity to Benzine. It also has fast response, long life, stable, and simple drive circuit. The proper alarm point considers temperature and humidity influence.

Rest of the project