INSPIRE-MANAK 2026 Project
Smart Alcohol Detection and Automatic Engine Locking System Using Arduino UNO and MQ-3 Alcohol Sensor
Student Innovation Project INSPIRE-MANAK 2026
1. Project overview
Project title: Smart Alcohol Detection and Automatic Engine Locking System for Drunken Drivers Using Arduino UNO.
Project idea: Develop an intelligent alcohol detection system that checks whether the driver has consumed alcohol before allowing a vehicle-start simulation. If alcohol is detected above a preset threshold, the system prevents the demonstration motor from starting and activates an alert.
This project aims to reduce drunk-driving incidents by introducing an alcohol detection mechanism into a vehicle-start authorization system.
The proposed prototype uses:
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Arduino UNO as the main controller.
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MQ-3 alcohol sensor to detect alcohol vapours.
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Relay module to control a low-voltage demonstration motor.
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LCD display to show system status.
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Buzzer to provide an audio warning.
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LEDs to indicate safe and unsafe conditions.
Important safety consideration: The student prototype described below controls only a small, isolated, low-voltage demonstration motor. It must not be connected to a real vehicle's ignition, starter, fuel pump, ECU, or engine wiring. Cutting propulsion while a vehicle is moving can cause a serious accident. Any real vehicle application would require automotive engineering, independent safety systems, and professional validation.
2. Problem statement
Drunk driving is one of the major causes of road accidents. Alcohol affects a driver's:
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Ability to control a vehicle safely.
Traditional vehicle starting systems generally do not check whether the driver has consumed alcohol.
Our project proposes a preventive system that checks for alcohol vapours before authorizing a vehicle-start demonstration.
Proposed solution
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The driver approaches the alcohol sensor.
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The MQ-3 sensor detects alcohol vapours.
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Arduino UNO reads the sensor's analogue output.
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The controller compares the reading against a calibrated threshold.
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If the reading is below the threshold, the demonstration motor is permitted to start.
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If the reading exceeds the threshold, the motor remains disabled.
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The buzzer and warning LED indicate alcohol detection.
3. Main objectives
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Detect alcohol vapours using an MQ-3 sensor.
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Develop an automatic vehicle-start prevention prototype.
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Control a demonstration motor using Arduino UNO.
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Display system status through an LCD.
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Generate an alert when alcohol is detected.
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Develop an affordable and educational road-safety solution.
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Demonstrate how sensor-based automation can improve driver safety.
4. Components required
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Component
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Quantity
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Purpose
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Arduino UNO
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1
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Main controller
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MQ-3 alcohol sensor module
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1
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Alcohol vapour detection
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16×2 LCD with I2C
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1
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Display messages
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5V relay module
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1
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Demonstration motor control
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Active buzzer
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1
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Warning sound
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Red LED
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1
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Alcohol warning
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Green LED
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1
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Safe/start permitted indication
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220Ω resistors
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2
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LED current limiting
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Push button
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1
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Start request
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Breadboard
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1
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Circuit assembly
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Jumper wires
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As required
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Connections
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Low-voltage DC motor
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1
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Vehicle-start demonstration
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Suitable motor power supply
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1
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Motor power
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5. Working principle
The project operates using the sensing capability of the MQ-3 alcohol sensor.
MQ-3 alcohol sensor
The MQ-3 is a semiconductor gas sensor designed to respond to alcohol vapours.
It contains a sensing element whose electrical resistance changes when exposed to alcohol-containing vapours.
The module provides:
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DO – digital output, depending on the module.
For this project, we use the AO pin because Arduino can read different analogue levels.
Arduino UNO
Arduino UNO acts as the brain of the system.
Its responsibilities include:
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Reading the alcohol sensor.
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Comparing readings with a threshold.
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Processing the driver's start request.
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Controlling the demonstration motor relay.
Relay module
The relay provides electrical switching for the low-voltage demonstration motor.
In this project, the motor is enabled only when the controller authorizes a start request.
LCD display
The LCD displays messages such as:
6. Complete system block diagram
The logical block diagram is:
text
DRIVER
|
v
MQ-3 ALCOHOL SENSOR
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v
ARDUINO UNO
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+------+------+
| | |
v v v
LCD BUZZER LEDS
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v
START AUTHORIZATION
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+------+------+
| |
v v
ALCOHOL NO ALCOHOL
DETECTED ABOVE THRESHOLD
| |
v v
MOTOR OFF MOTOR ENABLED
RED LED ON GREEN LED ON
7. Circuit connections
Arduino UNO pin connection table
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Component
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Component pin
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Arduino UNO
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MQ-3 sensor
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VCC
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5V
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MQ-3 sensor
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GND
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GND
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MQ-3 sensor
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AO
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A0
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LCD I2C
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VCC
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5V
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LCD I2C
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GND
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GND
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LCD I2C
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SDA
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A4
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LCD I2C
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SCL
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A5
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Relay module
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VCC
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5V
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Relay module
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GND
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GND
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Relay module
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IN
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D8
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Buzzer
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Positive
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D9
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Buzzer
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Negative
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GND
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Red LED
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Anode through 220Ω
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D6
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Green LED
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Anode through 220Ω
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D7
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Push button
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One terminal
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D2
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Push button
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Other terminal
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GND
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Demonstration motor relay connections
Use a separate, appropriately rated low-voltage supply for the demonstration motor.
text
ISOLATED LOW-VOLTAGE MOTOR CIRCUIT
Motor supply (+)
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Relay COM
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Relay NO
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DC MOTOR
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Motor supply (-)
The relay module's control side connects to Arduino. Its switching contacts control only the isolated demonstration motor circuit.
Do not connect this relay to a real vehicle.
8. Schematic diagram
The following is the simplified electrical architecture to use when assembling the prototype:
text
+------------------+
| ARDUINO UNO |
| |
MQ3 AO ---------->| A0 |
LCD SDA --------->| A4 |
LCD SCL --------->| A5 |
Relay IN -------->| D8 |
Buzzer (+) ------>| D9 |
Red LED ----------| D6 |
Green LED --------| D7 |
Start Button ---->| D2 |
| |
+------------------+
| |
5V GND
| |
+-------+------+-------+
| | |
MQ-3 LCD Relay
Assembly precautions:
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Check all power connections before switching on.
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Use a current-limited USB supply for the Arduino.
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Never power the DC motor directly from an Arduino GPIO pin.
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Use a motor supply suitable for the motor and relay ratings.
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Keep motor wiring separate from sensor wiring to reduce electrical interference.
9. System flowchart
This flowchart explains the complete working sequence.
mermaid
flowchart TD
A([START]) --> B[Power ON]
B --> C[Initialize Arduino]
C --> D[Initialize MQ3, LCD and Relay]
D --> E[Sensor Warm-up]
E --> F[Read Alcohol Sensor]
F --> G{Sensor Reading Valid?}
G -->|No| H[Motor Disabled]
H --> I[Display Sensor Error]
I --> F
G -->|Yes| J{Alcohol Above Threshold?}
J -->|Yes| K[Display Alcohol Detected]
K --> L[Red LED and Buzzer ON]
L --> M[Motor Disabled]
M --> F
J -->|No| N[Display Ready]
N --> O{Start Button Pressed?}
O -->|No| F
O -->|Yes| P[Green LED ON]
P --> Q[Enable Demonstration Motor]
Q --> F
10. Decision-making flowchart
The main decision is based on the sensor's analogue reading.
mermaid
flowchart TD
A[Read MQ3 Sensor] --> B[Obtain Analogue Value]
B --> C[Compare With Calibrated Threshold]
C --> D{Reading Above Threshold?}
D -->|YES| E[Alcohol Warning]
E --> F[Disable Motor]
F --> G[Activate Buzzer]
D -->|NO| H[Show Safe Sensor Reading]
H --> I{Start Button Pressed?}
I -->|YES| J[Permit Demo Motor]
I -->|NO| K[Wait]
J --> A
G --> A
K --> A
11. Step-by-step construction procedure
Step 1: Prepare the Arduino UNO
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Take an Arduino UNO board.
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Connect it to a computer using a USB cable.
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Verify that the Arduino board is detected.
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Select Arduino UNO under Tools → Board.
Step 2: Connect the MQ-3 alcohol sensor
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Connect VCC to Arduino 5V.
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Connect GND to Arduino GND.
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Connect AO to Arduino A0.
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Allow the sensor to warm up.
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Observe the readings using the Serial Monitor.
The MQ-3 requires a warm-up period. Its readings may drift, especially when the sensor is new or environmental conditions change. Follow the manufacturer's conditioning instructions.
Step 3: Connect the LCD
Install the LiquidCrystal_I2C library through Arduino IDE Library Manager.
Step 4: Connect the warning indicators
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Connect the red LED to D6 through a 220Ω resistor.
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Connect the green LED to D7 through a 220Ω resistor.
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Connect the buzzer positive terminal to D9.
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Connect the buzzer negative terminal to GND.
If your buzzer draws more current than a GPIO pin can safely supply, use a suitable transistor driver.
Step 5: Connect the start button
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Connect one button terminal to D2.
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Connect the other terminal to GND.
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The program uses Arduino's internal pull-up resistor.
Step 6: Connect the demonstration relay
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Connect relay GND to GND.
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Use the relay's normally open contact in the isolated low-voltage motor circuit.
Step 7: Upload the program
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Install the required LCD library.
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Select the correct COM port.
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Open Serial Monitor at 9600 baud.
12. Arduino software program
Complete educational prototype code
The following program implements sensor reading, threshold comparison, LCD messages, audio and visual alerts, and low-voltage demonstration motor authorization.
It deliberately does not implement real vehicle ignition or engine-control wiring.
cpp
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
// LCD address may be 0x27 or 0x3F
LiquidCrystal_I2C lcd(0x27, 16, 2);
// Pin configuration
const int alcoholSensor = A0;
const int relayPin = 8;
const int buzzerPin = 9;
const int redLED = 6;
const int greenLED = 7;
const int startButton = 2;
// Calibrate this value using clean-air readings
// and controlled sensor testing.
const int alcoholThreshold = 400;
// Many relay modules are active LOW.
// Change these if your relay module differs.
const int RELAY_ON = LOW;
const int RELAY_OFF = HIGH;
bool motorEnabled = false;
void disableMotor() {
digitalWrite(relayPin, RELAY_OFF);
motorEnabled = false;
}
void setup() {
Serial.begin(9600);
pinMode(relayPin, OUTPUT);
pinMode(buzzerPin, OUTPUT);
pinMode(redLED, OUTPUT);
pinMode(greenLED, OUTPUT);
pinMode(startButton, INPUT_PULLUP);
disableMotor();
digitalWrite(redLED, LOW);
digitalWrite(greenLED, LOW);
digitalWrite(buzzerPin, LOW);
lcd.init();
lcd.backlight();
lcd.setCursor(0, 0);
lcd.print("SMART ALCOHOL");
lcd.setCursor(0, 1);
lcd.print("DETECTION SYSTEM");
delay(2000);
lcd.clear();
lcd.print("SENSOR WARMING");
lcd.setCursor(0, 1);
lcd.print("PLEASE WAIT");
// Initial demonstration warm-up delay.
// Follow the sensor manufacturer's full
// conditioning and warm-up requirements.
delay(30000);
lcd.clear();
lcd.print("SYSTEM READY");
delay(1500);
}
void loop() {
int alcoholValue = analogRead(alcoholSensor);
Serial.print("MQ3 Reading: ");
Serial.println(alcoholValue);
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("Alcohol:");
lcd.print(alcoholValue);
// Alcohol threshold exceeded
if (alcoholValue >= alcoholThreshold) {
disableMotor();
digitalWrite(redLED, HIGH);
digitalWrite(greenLED, LOW);
digitalWrite(buzzerPin, HIGH);
lcd.setCursor(0, 1);
lcd.print("ALCOHOL DETECTED");
Serial.println("WARNING: MOTOR DISABLED");
}
// Reading below threshold
else {
digitalWrite(redLED, LOW);
digitalWrite(buzzerPin, LOW);
lcd.setCursor(0, 1);
lcd.print("CHECK START");
// Permit only a button-requested
// low-voltage demonstration motor start.
if (digitalRead(startButton) == LOW) {
digitalWrite(greenLED, HIGH);
digitalWrite(relayPin, RELAY_ON);
motorEnabled = true;
lcd.clear();
lcd.print("START PERMITTED");
lcd.setCursor(0, 1);
lcd.print("DEMO MOTOR ON");
Serial.println("DEMO MOTOR ENABLED");
delay(1000);
}
else {
digitalWrite(greenLED, LOW);
if (!motorEnabled) {
disableMotor();
}
}
}
delay(500);
}
Explanation of the program
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Program section
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Function
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Library inclusion
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Enables LCD communication
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Pin configuration
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Defines Arduino connections
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setup()
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Initializes the components
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analogRead()
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Reads the MQ-3 sensor
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Threshold comparison
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Identifies elevated sensor readings
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disableMotor()
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Disables the demonstration motor
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Red LED
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Indicates an alcohol warning
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Green LED
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Indicates start authorization
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Buzzer
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Produces an alert
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LCD
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Displays the operating condition
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Start button
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Requests demonstration motor activation
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Note about the sample code: The value 400 is only an example threshold, not a scientifically validated alcohol concentration or legal blood-alcohol limit. The program also uses a simple demonstration threshold, not a certified breath-alcohol measurement. MQ-3 readings can be affected by other vapours, temperature, humidity, sensor age and calibration.
Before testing, inspect the relay's active-high/active-low behaviour and adjust the software constants to match the actual module.
13. Sensor calibration and threshold setting
This is one of the most important stages of the project.
The MQ-3 does not directly provide a blood-alcohol concentration. It provides an analogue voltage that changes with the surrounding vapour concentration.
Calibration procedure
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Power the sensor and allow it to stabilize according to its datasheet.
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Keep the sensor in a clean-air environment.
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Observe the analogue readings in Serial Monitor.
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Record the baseline readings.
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Perform controlled calibration using an appropriate certified alcohol reference gas and suitable laboratory procedures.
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Record the corresponding sensor readings.
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Select an experimental threshold for the demonstration.
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Test the prototype repeatedly to check whether the readings are stable.
Example of a results-recording table:
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Test condition
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Analogue reading
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Expected response
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Clean-air baseline
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To be measured
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Start may be permitted
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Reference gas below experimental threshold
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To be measured
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Start may be permitted
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Reference gas above experimental threshold
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To be measured
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Motor disabled
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Sensor disconnected
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To be measured
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Requires separate fault detection
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Do not interpret these analogue readings as a person's actual blood-alcohol concentration or fitness to drive.
14. Complete working explanation
The complete working process is as follows:
Stage 1: Power supply
When the system receives power, Arduino UNO starts executing the program.
Stage 2: Sensor initialization
The MQ-3 sensor begins warming up. The LCD displays the initialization message.
Stage 3: Alcohol sensing
The sensor responds to alcohol vapours in its surroundings and produces an analogue signal.
Stage 4: Signal processing
Arduino reads the signal using its analogue input A0.
Stage 5: Decision-making
Arduino compares the reading with the experimentally calibrated threshold.
Stage 6: Alcohol warning condition
If the reading is above the threshold:
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LCD displays ALCOHOL DETECTED.
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Demonstration motor remains disabled.
Stage 7: Normal condition
If the reading is below the threshold:
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LCD displays CHECK START.
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Green LED indicates authorization when the start button is pressed.
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Demonstration motor is enabled.
Stage 8: Continuous monitoring
Arduino continuously reads the sensor and updates the demonstration system's status.
15. Project operation chart
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Parameter
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Alcohol warning condition
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Normal sensor condition
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MQ-3 reading
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Above threshold
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Below threshold
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LCD
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Alcohol detected
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Check start
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Red LED
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ON
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OFF
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Green LED
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OFF
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ON when start requested
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Buzzer
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ON
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OFF
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Relay
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Disabled
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Enabled on start request
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Demo motor
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OFF
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ON when authorized
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16. Testing and validation
After assembly, perform the following tests.
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Test
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Procedure
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Expected result
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Test 1
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Switch ON Arduino
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LCD initializes
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Test 2
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Allow sensor warm-up
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Sensor readings stabilize
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Test 3
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Check clean-air readings
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Baseline is displayed
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Test 4
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Apply certified reference gas below threshold
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Start authorization possible
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Test 5
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Apply certified reference gas above threshold
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Motor disabled
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Test 6
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Press start button in permitted condition
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Demo motor starts
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Test 7
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Increase sensor reading above threshold
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Demo motor is disabled
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Test 8
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Remove sensor connection
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Fault behaviour must be investigated and improved
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These are proposed test cases, not claimed experimental results. Record your actual readings and observations during testing.
17. Advantages of the project
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Helps demonstrate preventive drunk-driving technology.
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Uses affordable electronic components.
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Simple Arduino-based implementation.
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Provides audio and visual warnings.
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Demonstrates automatic start authorization.
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Can be expanded with IoT technology.
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Suitable for educational electronics and road-safety demonstrations.
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Provides an opportunity to study sensors, embedded systems and automation.
18. Limitations
Every engineering project has limitations.
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MQ-3 is not a certified evidential breathalyser.
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It can respond to interfering vapours.
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Temperature and humidity may affect measurements.
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Sensor warm-up and calibration are important.
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A single sensor cannot guarantee that the driver is sober.
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Sensor readings cannot establish legal intoxication.
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Power failure, wiring faults and relay failures require additional safety measures.
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The educational prototype is not suitable for installation in a real vehicle.
19. Future scope
The project can be developed further with additional technologies.
1. IoT-based monitoring
Use ESP32 to send system status to a monitoring dashboard.
2. GPS integration
Add location reporting for a stationary demonstration or safety-monitoring prototype.
3. Advanced display
Show sensor status, calibration state, system errors and test results.
4. Cloud monitoring
Record demonstration test events and sensor performance.
5. Advanced driver monitoring
Research additional independent driver-safety technologies, with appropriate privacy and safety protections.
20. Complete project documentation
The following sections can be included directly in your INSPIRE-MANAK project report.
A. Abstract
Smart Alcohol Detection and Automatic Engine Locking System Using Arduino UNO is an innovative road-safety project designed to demonstrate how alcohol detection technology can be used to prevent unauthorized vehicle starting.
The proposed system uses an MQ-3 alcohol sensor to detect alcohol vapours. Arduino UNO processes the sensor output and compares it with a predefined experimental threshold. When the sensor reading exceeds the threshold, the controller activates a warning buzzer, switches ON a red LED, displays an alcohol detection message on the LCD and disables the low-voltage demonstration motor.
When the sensor reading is below the threshold, the system permits a start request through a push button and activates the demonstration motor.
The project demonstrates the application of embedded systems, gas sensors and automatic control technology to road safety. It is a low-cost educational prototype that can be further developed through improved sensing, calibration and independent safety validation.
B. Introduction
Road accidents caused by drunk driving are a major public safety concern. Alcohol consumption can affect the human nervous system and reduce the ability to control vehicles safely.
This project introduces a smart alcohol detection system that demonstrates how a vehicle-start authorization mechanism could work.
The system uses an MQ-3 sensor connected to an Arduino UNO. The sensor detects alcohol vapours, and the microcontroller processes the output to determine whether a start request should be permitted in the demonstration model.
The primary goal is to demonstrate preventive road-safety technology using affordable electronic components.
C. Need for the project
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To create awareness about drunk driving.
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To demonstrate alcohol detection using electronic sensors.
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To explore automatic vehicle-start authorization.
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To develop an affordable student innovation prototype.
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To encourage the use of technology for public safety.
D. Innovation and uniqueness
The innovative aspect of this project is the combination of:
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Automatic electronic decision-making.
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Demonstration motor control.
The system combines these functions into one compact prototype using Arduino UNO.
E. Social impact
The project has the potential to contribute to road-safety awareness by demonstrating how preventive technology can discourage drunk driving.
Its educational value includes:
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Promoting responsible driving.
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Creating awareness among young people.
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Encouraging engineering innovation.
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Demonstrating practical applications of electronics.
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Inspiring students to develop safety-focused technologies.
F. Conclusion
The Smart Alcohol Detection and Automatic Engine Locking System using Arduino UNO is a student-oriented innovation project that demonstrates alcohol vapour sensing and automatic start authorization.
The MQ-3 sensor detects alcohol vapours, while Arduino UNO processes the sensor output. Based on the experimental threshold, the system either permits or denies a demonstration motor start request.
The LCD, buzzer and LEDs provide clear indications of the system's operating condition.
This project demonstrates how embedded systems and sensor technology can be applied to road-safety education. With further research, improved sensing, calibration and professional safety engineering, the concept could contribute to the development of more advanced driver-safety technologies.
G. References and learning resources
For the final report, consult:
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MQ-3 alcohol sensor datasheet – obtain the datasheet corresponding to your sensor manufacturer and module.
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Basic embedded systems and electronic circuit design textbooks.
21. Suggested project report structure
For a professional school-level project submission, arrange the report in this order:
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Chapter
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Topic
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1
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Introduction
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2
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Problem statement
|
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3
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Objectives
|
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4
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Proposed solution
|
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5
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Components and specifications
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6
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Working principle
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7
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Block diagram
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8
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Circuit and schematic diagram
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9
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Flowcharts
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10
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Hardware implementation
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11
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Software implementation
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12
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Arduino source code
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13
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Testing and observations
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14
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Advantages and limitations
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15
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Future scope
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16
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Social impact
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17
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Conclusion
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18
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References
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22. INSPIRE-MANAK presentation plan
For your project exhibition, I recommend preparing these five items:
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Working model: Arduino UNO, MQ-3 sensor, LCD, buzzer, LEDs and a small demonstration motor.
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Project display board: Problem, objectives, innovation, working principle and social benefits.
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Circuit diagram: Clearly labelled connections.
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Flowchart: Sensor detection and start authorization.
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Demonstration video: Show both normal and alcohol-warning conditions using controlled reference testing.
23. Questions judges may ask
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Question
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Suggested answer
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Why did you select MQ-3?
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It is designed to respond to alcohol vapours and is suitable for an educational detection prototype.
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Why Arduino UNO?
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It is affordable, programmable and has analogue inputs for sensor measurements.
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What happens when alcohol is detected?
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The warning is activated and the demonstration motor is disabled.
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What is the function of the relay?
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It electrically switches the low-voltage demonstration motor.
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Why use an LCD?
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To display sensor readings and operating conditions.
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Can this project prevent all drunk-driving incidents?
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No. It demonstrates one possible preventive technology and has sensor limitations.
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Can it be installed in a real car?
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Not in its present form. Professional automotive safety engineering and validation would be necessary.
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What is the main innovation?
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Combining alcohol sensing with automatic start authorization and warning indications.
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24. Recommended final project title
SMART ALCOHOL DETECTION AND AUTOMATIC ENGINE START LOCKING SYSTEM
Using Arduino UNO and MQ-3 Alcohol Sensor
INSPIRE-MANAK 2026
A student innovation project for road safety using embedded systems and sensor technology.
My recommendation: For INSPIRE-MANAK, emphasize not just the Arduino circuit but the actual social problem, your innovative solution, how it works, its limitations and how you would make it safer and more reliable. A well-explained working model and your own experimental observations will make the project report much stronger.
