INSPIRE-MANAK - 2026 | Smart Alcohol Detection & Automatic Engine Locking System Using Arduino UNO, MQ-3 Alcohol Sensor

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:

• Arduino UNO as the main controller.

• MQ-3 alcohol sensor to detect alcohol vapours.

• Relay module to control a low-voltage demonstration motor.

• LCD display to show system status.

• Buzzer to provide an audio warning.

• 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:

• Reaction time.

• Concentration.

• Decision-making ability.

• Vision and coordination.

• 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

1. The driver approaches the alcohol sensor.

2. The MQ-3 sensor detects alcohol vapours.

3. Arduino UNO reads the sensor's analogue output.

4. The controller compares the reading against a calibrated threshold.

5. If the reading is below the threshold, the demonstration motor is permitted to start.

6. If the reading exceeds the threshold, the motor remains disabled.

7. The buzzer and warning LED indicate alcohol detection.

3. Main objectives

1. Detect alcohol vapours using an MQ-3 sensor.

2. Develop an automatic vehicle-start prevention prototype.

3. Control a demonstration motor using Arduino UNO.

4. Display system status through an LCD.

5. Generate an alert when alcohol is detected.

6. Develop an affordable and educational road-safety solution.

7. Demonstrate how sensor-based automation can improve driver safety.

4. Components required

Component	Quantity	Purpose
Arduino UNO	1	Main controller
MQ-3 alcohol sensor module	1	Alcohol vapour detection
16×2 LCD with I2C	1	Display messages
5V relay module	1	Demonstration motor control
Active buzzer	1	Warning sound
Red LED	1	Alcohol warning
Green LED	1	Safe/start permitted indication
220Ω resistors	2	LED current limiting
Push button	1	Start request
Breadboard	1	Circuit assembly
Jumper wires	As required	Connections
Low-voltage DC motor	1	Vehicle-start demonstration
Suitable motor power supply	1	Motor power

5. Working principle

The project operates using the sensing capability of the MQ-3 alcohol sensor.

techmaze.ae

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:

• VCC – power supply.

• GND – ground.

• AO – analogue output.

• 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:

• Reading the alcohol sensor.

• Comparing readings with a threshold.

• Processing the driver's start request.

• Controlling the LCD.

• Activating the buzzer.

• 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:

• SYSTEM INITIALIZING

• SENSOR WARMING

• READY TO TEST

• ALCOHOL DETECTED

• START PERMITTED

• MOTOR DISABLED

6. Complete system block diagram

xilirprojects.com

The logical block diagram is:

text

           DRIVER
              |
              v
       MQ-3 ALCOHOL SENSOR
              |
              v
          ARDUINO UNO
              |
       +------+------+
       |      |      |
       v      v      v
      LCD   BUZZER  LEDS
              |
              v
       START AUTHORIZATION
              |
       +------+------+
       |             |
       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

Component	Component pin	Arduino UNO
MQ-3 sensor	VCC	5V
MQ-3 sensor	GND	GND
MQ-3 sensor	AO	A0
LCD I2C	VCC	5V
LCD I2C	GND	GND
LCD I2C	SDA	A4
LCD I2C	SCL	A5
Relay module	VCC	5V
Relay module	GND	GND
Relay module	IN	D8
Buzzer	Positive	D9
Buzzer	Negative	GND
Red LED	Anode through 220Ω	D6
Green LED	Anode through 220Ω	D7
Push button	One terminal	D2
Push button	Other terminal	GND

Demonstration motor relay connections

Use a separate, appropriately rated low-voltage supply for the demonstration motor.

text

       ISOLATED LOW-VOLTAGE MOTOR CIRCUIT

       Motor supply (+)
              |
              |
        Relay COM
              |
        Relay NO
              |
          DC MOTOR
              |
       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

rees52.com

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:

• Check all power connections before switching on.

• Use a current-limited USB supply for the Arduino.

• Never power the DC motor directly from an Arduino GPIO pin.

• Use a motor supply suitable for the motor and relay ratings.

• 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

conrad.se

• Take an Arduino UNO board.

• Connect it to a computer using a USB cable.

• Install Arduino IDE.

• Verify that the Arduino board is detected.

• Select Arduino UNO under Tools → Board.

Step 2: Connect the MQ-3 alcohol sensor

diyprojectslab.com

• Connect VCC to Arduino 5V.

• Connect GND to Arduino GND.

• Connect AO to Arduino A0.

• Allow the sensor to warm up.

• 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

electronoobs.com

• Connect LCD VCC to 5V.

• Connect LCD GND to GND.

• Connect SDA to A4.

• Connect SCL to A5.

Install the LiquidCrystal_I2C library through Arduino IDE Library Manager.

Step 4: Connect the warning indicators

• Connect the red LED to D6 through a 220Ω resistor.

• Connect the green LED to D7 through a 220Ω resistor.

• Connect the buzzer positive terminal to D9.

• 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

• Connect one button terminal to D2.

• Connect the other terminal to GND.

• The program uses Arduino's internal pull-up resistor.

Step 6: Connect the demonstration relay

• Connect relay VCC to 5V.

• Connect relay GND to GND.

• Connect relay IN to D8.

• Use the relay's normally open contact in the isolated low-voltage motor circuit.

Step 7: Upload the program

• Open Arduino IDE.

• Create a new sketch.

• Copy the program below.

• Install the required LCD library.

• Select the correct COM port.

• Upload the program.

• 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

Program section	Function
Library inclusion	Enables LCD communication
Pin configuration	Defines Arduino connections
setup()	Initializes the components
analogRead()	Reads the MQ-3 sensor
Threshold comparison	Identifies elevated sensor readings
disableMotor()	Disables the demonstration motor
Red LED	Indicates an alcohol warning
Green LED	Indicates start authorization
Buzzer	Produces an alert
LCD	Displays the operating condition
Start button	Requests demonstration motor activation

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

1. Power the sensor and allow it to stabilize according to its datasheet.

2. Keep the sensor in a clean-air environment.

3. Observe the analogue readings in Serial Monitor.

4. Record the baseline readings.

5. Perform controlled calibration using an appropriate certified alcohol reference gas and suitable laboratory procedures.

6. Record the corresponding sensor readings.

7. Select an experimental threshold for the demonstration.

8. Test the prototype repeatedly to check whether the readings are stable.

Example of a results-recording table:

Test condition	Analogue reading	Expected response
Clean-air baseline	To be measured	Start may be permitted
Reference gas below experimental threshold	To be measured	Start may be permitted
Reference gas above experimental threshold	To be measured	Motor disabled
Sensor disconnected	To be measured	Requires separate fault detection

Do not interpret these analogue readings as a person's actual blood-alcohol concentration or fitness to drive.

14. Complete working explanation

srrobotics.in

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:

• Red LED turns ON.

• Buzzer turns ON.

• LCD displays ALCOHOL DETECTED.

• Demonstration motor remains disabled.

Stage 7: Normal condition

If the reading is below the threshold:

• Red LED turns OFF.

• Buzzer turns OFF.

• LCD displays CHECK START.

• Green LED indicates authorization when the start button is pressed.

• Demonstration motor is enabled.

Stage 8: Continuous monitoring

Arduino continuously reads the sensor and updates the demonstration system's status.

15. Project operation chart

Parameter	Alcohol warning condition	Normal sensor condition
MQ-3 reading	Above threshold	Below threshold
LCD	Alcohol detected	Check start
Red LED	ON	OFF
Green LED	OFF	ON when start requested
Buzzer	ON	OFF
Relay	Disabled	Enabled on start request
Demo motor	OFF	ON when authorized

16. Testing and validation

After assembly, perform the following tests.

Test	Procedure	Expected result
Test 1	Switch ON Arduino	LCD initializes
Test 2	Allow sensor warm-up	Sensor readings stabilize
Test 3	Check clean-air readings	Baseline is displayed
Test 4	Apply certified reference gas below threshold	Start authorization possible
Test 5	Apply certified reference gas above threshold	Motor disabled
Test 6	Press start button in permitted condition	Demo motor starts
Test 7	Increase sensor reading above threshold	Demo motor is disabled
Test 8	Remove sensor connection	Fault behaviour must be investigated and improved

These are proposed test cases, not claimed experimental results. Record your actual readings and observations during testing.

17. Advantages of the project

1. Helps demonstrate preventive drunk-driving technology.

2. Uses affordable electronic components.

3. Simple Arduino-based implementation.

4. Provides audio and visual warnings.

5. Demonstrates automatic start authorization.

6. Can be expanded with IoT technology.

7. Suitable for educational electronics and road-safety demonstrations.

8. Provides an opportunity to study sensors, embedded systems and automation.

18. Limitations

Every engineering project has limitations.

• MQ-3 is not a certified evidential breathalyser.

• It can respond to interfering vapours.

• Temperature and humidity may affect measurements.

• Sensor warm-up and calibration are important.

• A single sensor cannot guarantee that the driver is sober.

• Sensor readings cannot establish legal intoxication.

• Power failure, wiring faults and relay failures require additional safety measures.

• 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

• To create awareness about drunk driving.

• To demonstrate alcohol detection using electronic sensors.

• To explore automatic vehicle-start authorization.

• To develop an affordable student innovation prototype.

• To encourage the use of technology for public safety.

D. Innovation and uniqueness

The innovative aspect of this project is the combination of:

1. Alcohol vapour sensing.

2. Automatic electronic decision-making.

3. Audio warning.

4. Visual indication.

5. Start authorization.

6. 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:

• Promoting responsible driving.

• Creating awareness among young people.

• Encouraging engineering innovation.

• Demonstrating practical applications of electronics.

• 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:

1. Arduino UNO official documentation – Arduino UNO Rev3 .

2. MQ-3 alcohol sensor datasheet – obtain the datasheet corresponding to your sensor manufacturer and module.

3. Arduino programming reference – Arduino Language Reference .

4. LiquidCrystal_I2C library documentation – LiquidCrystal_I2C library .

5. 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:

Chapter	Topic
1	Introduction
2	Problem statement
3	Objectives
4	Proposed solution
5	Components and specifications
6	Working principle
7	Block diagram
8	Circuit and schematic diagram
9	Flowcharts
10	Hardware implementation
11	Software implementation
12	Arduino source code
13	Testing and observations
14	Advantages and limitations
15	Future scope
16	Social impact
17	Conclusion
18	References

22. INSPIRE-MANAK presentation plan

For your project exhibition, I recommend preparing these five items:

1. Working model: Arduino UNO, MQ-3 sensor, LCD, buzzer, LEDs and a small demonstration motor.

2. Project display board: Problem, objectives, innovation, working principle and social benefits.

3. Circuit diagram: Clearly labelled connections.

4. Flowchart: Sensor detection and start authorization.

5. Demonstration video: Show both normal and alcohol-warning conditions using controlled reference testing.

23. Questions judges may ask

Question	Suggested answer
Why did you select MQ-3?	It is designed to respond to alcohol vapours and is suitable for an educational detection prototype.
Why Arduino UNO?	It is affordable, programmable and has analogue inputs for sensor measurements.
What happens when alcohol is detected?	The warning is activated and the demonstration motor is disabled.
What is the function of the relay?	It electrically switches the low-voltage demonstration motor.
Why use an LCD?	To display sensor readings and operating conditions.
Can this project prevent all drunk-driving incidents?	No. It demonstrates one possible preventive technology and has sensor limitations.
Can it be installed in a real car?	Not in its present form. Professional automotive safety engineering and validation would be necessary.
What is the main innovation?	Combining alcohol sensing with automatic start authorization and warning indications.

24. Recommended final project title

SMART ALCOHOL DETECTION AND AUTOMATIC ENGINE START LOCKING SYSTEM

Using Arduino UNO and MQ-3 Alcohol Sensor

srrobotics.in

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.