Introduction

Alcohol-impaired driving is a significant cause of accidents and fatalities on the road. To ensure road safety, breathalyzer devices have become indispensable tools for law enforcement agencies and responsible individuals alike. In this article, we will explore how to create a breathalyzer alcohol tester with an LCD display using Arduino. This DIY project combines technology and safety, allowing you to measure blood alcohol content (BAC) with a simple, affordable device.

Working Principle

Breathalyzer devices determine BAC by analyzing the alcohol content in a person’s breath. When alcohol is consumed, it is absorbed into the bloodstream, and a fraction of it is exhaled through the breath. The alcohol concentration in the breath is directly proportional to the BAC.

The working principle of a breathalyzer involves a chemical reaction between the ethanol in the breath and a chemical reagent, producing a measurable electrical signal. The more alcohol present in the breath, the stronger the electrical signal. This signal is then converted into a BAC reading and displayed on an LCD.

Things We Need

1. Arduino Uno
2. MQ-3 alcohol sensor module
3. 16×2 LCD display with I2C Module
4. Breadboard and jumper wires
5. Power source (battery or USB cable)
6. Resistor (10k ohms) (if you are not using a sensor module)

Circuit Diagram

Add a 10k-ohm resistor between VCC and A0 on the MQ-3 sensor to create a voltage divider if you are not using a sensor module. If you are using a sensor module than you will have a trim pot to adjust the sensitivity of the MQ-3 Sensor.

Working of the System with Arduino

The Arduino reads analog data from the MQ-3 sensor connected to A0. This analog value represents the alcohol concentration in the breath. The Arduino then processes this data and displays the BAC on the LCD.

The concentration sensing range of 0.04 mg/L to 4 mg/L is suitable for breathalyzers (the legal limit of breath alcohol concentration, or BrAC, in most US states is 0.08 grams per 210 liters, or 0.38 mg/L). The sensor can operate at temperatures from -10 to 50°C and consumes less than 150 mA at 5 V.

Code

#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

int alcoholPin = A0;

void setup() {
  lcd.init();
  lcd.backlight();
  Serial.begin(9600);
}

void loop() {
  int alcoholValue = analogRead(alcoholPin);
  float voltage = (alcoholValue / 1023.0) * 5.0;
  float bac = map(voltage, 0.0, 5.0, 0.0, 0.4); // Adjust the mapping based on sensor calibration 0.4 stands for the 4mg

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("BAC:");
  lcd.setCursor(5, 0);
  lcd.print(bac, 3); // Display BAC with 3 decimal places
  lcd.setCursor(9, 0);
  lcd.print(" %");

  delay(1000);
}

Conclusion

Building a breathalyzer alcohol tester with an LCD display using Arduino is an educational and potentially life-saving project. While this DIY breathalyzer can provide indicative BAC readings, it’s essential to understand its limitations and not rely on it for legal or medical purposes. Commercially available breathalyzer devices undergo rigorous calibration and testing to ensure accuracy.

Always remember to drink responsibly and never drink and drive. This project serves as an excellent example of how technology can be used to promote safety and awareness.