Do It Yourself Breathalyzer with MQ-3 & LEGO Bricks

In this video you will learn how to create an entirely open source breathalyzer with MQ-3 analog sensor module, mini I2C OLED display (SSD1306), an Arduino sketch for the open source hardware ANAVI Gas Detector and a lot of LEGO bricks.

MQ-3 is a low-cost analog sensor module for detecting alcohol. It is suitable for alcohol checkers and breathalyzers. According to the datasheet it has high sensitivity to alcohol and small sensitivity to benzine. The disadvantage is that is that it is not very accurate and requires calibration. The pre-heat time is over 24 hours. This means you need to place it in a room with clean air and keep the sensor running for more than 24 hours when you turn it on for very first time. This is a one-time procedure, after that the sensor just needs a few minutes to start working.

ANAVI Gas Detector is an ESP8266-powered Wi-Fi development board for monitoring air quality and detecting dangerous gases. It has been created with KiCad and has been certified as open source hardware by Open Source Hardware Association (OSHWA). Although ANAVI Gas Detector has been designed for MQ-135 analog sensor module for measuring indoor air quality and detecting dangerous gases, it is also compatible with other 5V analog gas sensors such as MQ-3.

LEGO® Medium Creative Brick Box 10696 is used to provide all components for the case. The LEGO® contains 484 parts which are more than enough for this fun project.The do it yourself breathalyzer created in this project is just for fun. It is not very accurate. It is provided "as is" without any warranty. Drink responsibly. Never drink and drive!

Step 1: Arduino sketch for ANAVI Gas Detector with MQ-3

An Arduino sketch for MQ-3 and ANAVI Gas Detector is available at GitHub. Download it and flash it to ANAVI Gas Detector through Arduino IDE.

Function detectAlcohol reads data from the pin connected to the analog output of MQ-3. Depending on the retrieved data and hardcoded threshold values, text is displayed on the mini OLED display.

Step 2: Building a case with LEGO bricks

ANAVI Gas Detector is placed on a big green LEGO® plate. LEGO® bricks are placed around it in a way to keep it in the same position. There is a whole for micro USB cable and placeholders for the mini OLED display and the MQ-3 sensor module.

Step 3: Calibration and testing

MQ-3 is not very accurate and requires calibration depending on the air quality, the temperature and the humidity in the environment in which it will work. After doing the one-time pre-heat procedure, you can test the sensitivity of MQ-3 to various alcohol drinks.

I took the do it yourself breathalyzer, which I called "The Breathanalyzer" to the Kapana creative district in my hometown Plovdiv, Bulgaria. This is a small neighborhood with a lot of bars and restaurants, especially popular among tourists.