Introduction: Alcohol Tester With LED Lights


In this project I will explain to you how to create a breathalyzer to estimate blood alcohol content from a breath sample using a MQ-3 Alcohol Gas sensor and using VIPER or Sublime Text to program the board.

I used Arduino Due but it is also possible to use other boards with the same code, because VIPER is multiboard.

The breathalyzer consists of 9 LED's: 3 green and 6 red. They light up according to the alcohol concentration read by the MQ-3 sensor. The system must be calibrated by setting the values of the calibration in the code and through the resistors. The aim is to only have the 3 green LED's light up when the concentration of alcohol is under a certain level.


1. Connect the power to the Vin pin and ground rails to the GND pin on the Arduino.

2. Connect the anod of the led to the pin 4 and the cathod to the ground rail of the breadboard using a 220Ω resistor. Repeat this to connect the other LED's from pin 5 until 12.

3. Connect the sensor as shown in the specified scheme:
- Connect the B pins and one of the H pins of the sensor to the 5V output of the board
- Connect the other H pin to the ground
- Connect the A pins to the breadboard before the two serial resistor (4.7K and 10K ohm) as in the scheme
- Connect the A0 analog in to the breadboard among the two serial resistors (4.7K and 10K ohm)
- Connect the end of the serial resistors to the ground (as in the scheme)


Download the programming code (will be attached) and paste it in the IDE, viperize your board and upload the code to the board.


This project was based on a project that I found on and it was made by Francesco Manetti ( All of the credits go out to him!