Arduino Alcohol Detector

This DIY electronics project showcases how to create a simple alcohol sniffing device using an Arduino and an MQ‑3 gas sensor. The system detects alcohol vapors in the environment—commonly used for breathalyzer-style applications—and provides immediate readings and visual feedback

Story

Project Overview

This DIY electronics project showcases how to create a simple alcohol sniffing device using an Arduino and an MQ‑3 gas sensor. The system detects alcohol vapors in the environment—commonly used for breathalyzer-style applications—and provides immediate readings and visual feedback.

Objectives & Purpose

Design and build a breath alcohol detection system
Read alcohol levels via the MQ‑3 sensor
Display results to users through LEDs and serial output
Demonstrate sensor interfacing and basic data thresholding

Key Components

Component	Description
Arduino Uno/Nano	Acts as the microcontroller base
MQ‑3 Gas Sensor	Detection of alcohol vapor
LEDs	Example: green for safe, red for alcohol alert
Buzzer (optional)	Audible alarm when threshold crossed
Resistors	For LED current limiting
Jumper Wires	For connections
Breadboard	Optional, for prototyping

How the System Works

MQ‑3 sensor measures alcohol concentration in breath via changes in analog output voltage.
Arduino's analog input pin (e.g., A0) reads the sensor voltage.
The code processes analog values:
- If it exceeds a threshold → LED turns red + optional buzzer triggers.
- Else → LED stays green.
Serial Monitor output shows real-time sensor voltage values (for debugging and calibration).

Wiring & Connections

MQ‑3 Sensor:
- VCC → 5V
- GND → GND
- AOUT → Arduino A0
Green LED:
- Anode → Arduino digital pin (e.g. D8) via resistor
- Cathode → GND
Red LED (Alert):
- Anode → Arduino digital pin (e.g. D9) via resistor
- Cathode → GND
Buzzer (Optional):
- One terminal → Arduino digital pin
- Other terminal → GND

Sample Arduino Sketch

cpp

const int sensorPin = A0;
const int greenLED = 8;
const int redLED = 9;
const int buzzer = 10;       // Optional
const int threshold = 300;   // Calibrate for your environment

void setup() {
  Serial.begin(9600);
  pinMode(greenLED, OUTPUT);
  pinMode(redLED, OUTPUT);
  pinMode(buzzer, OUTPUT);
  digitalWrite(greenLED, HIGH); // default safe indication
  digitalWrite(redLED, LOW);
}

void loop() {
  int sensorValue = analogRead(sensorPin);
  Serial.println(sensorValue);
  if (sensorValue > threshold) {
    digitalWrite(redLED, HIGH);
    digitalWrite(greenLED, LOW);
    digitalWrite(buzzer, HIGH); // if included
  } else {
    digitalWrite(redLED, LOW);
    digitalWrite(greenLED, HIGH);
    digitalWrite(buzzer, LOW);
  }
  delay(500);
}

???? Adjust threshold based on your calibration experiments (monitor serial output while testing with known ethanol sources).

Applications & Extensions

Breathalyzer prototypes for educational purposes
Alcohol vapor detection in enclosed spaces
Calibration improvements using LCD/OLED displays
Bluetooth or Wi-Fi output for remote monitoring
Data logging to SD card or cloud services

Key Learning Outcomes

Working with analog sensors and voltage-based thresholds
Interfacing the MQ‑3 gas sensor with Arduino
Using LEDs and buzzers for alerts
Calibrating sensors and interpreting analog data

Safety & Calibration Notes

MQ‑3 sensors respond to both ethanol (alcohol) and certain volatile organic compounds—may give false positives if not calibrated
Always test in well-ventilated areas
Use small alcohol sources (e.g., diluted beverages) for testing—not direct ingestion
Be cautious with heating cycles and sensor warm-ups (usually requires several minutes to stabilize)

Arduino Alcohol Detector

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