Car Speed Detector Using Arduino

This project demonstrates a car speed detection system using Arduino UNO, IR sensors, 16x2 LCD with I2C, buzzer, and basic components. It calculates vehicle speed by measuring the time taken to pass between two sensors and alerts if the speed exceeds the limit.

How the System Works

Two IR sensors are placed 20 cm apart on a simulated road setup
When a vehicle passes the first sensor, a timer starts
The timer stops when the vehicle passes the second sensor
Speed is calculated using the formula: Speed = Distance / Time
The system scales the measurement to simulate a 5-meter distance for practical application
Speed is converted to km/h and displayed on the LCD
If speed exceeds 50 km/h, the buzzer sounds and displays "Over Speeding"
For normal speeds, the display shows "Normal Speed"

Materials Required

Arduino UNO - Buy Here
IR Sensors - Buy Here
LCD Display with I2C Module - Buy Here
Mini Breadboard - Buy Here
Jumper Wires - Buy Here
Buzzer - Buy Here
MDF Board - Buy Here

3D Files

Download the 3D printable files for the project enclosure and mounting brackets:

Google Drive

Print these files using JLCPCB's 3D printing service:

Order Now

Step-by-Step Assembly

1. Setup the Road Simulation:

Cover an MDF board with black paper to simulate road surface
Add white paper strips as road markings for realistic appearance
Mount the two IR sensors exactly 20 cm apart

2. Wiring the Circuit:

Connect the first IR sensor to pin 2 of Arduino
Connect the second IR sensor to pin 3 of Arduino
Connect LCD I2C module to SDA (A4) and SCL (A5) pins
Connect buzzer to pin 11
Use breadboard for power distribution (5V and GND connections)

3. Arduino Code:

Upload the provided Arduino code
Adjust speed threshold (50 km/h default) if needed
Modify scaling factors for different simulation distances

4. Testing the System:

Move an object (or toy car) past both sensors
Verify speed calculation and display on LCD
Test buzzer activation when exceeding speed limit
Check "Normal Speed" display for compliant speeds

Circuit Diagram

The detailed circuit diagram is provided in the video.

🎥 Watch the video above for full wiring instructions.

Arduino Code

Once the circuit is set up, upload the following code to the Arduino UNO using the Arduino IDE.

#include <LiquidCrystal_I2C.h>
#include <Wire.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

float timer1;
float timer2;
float Time;

int flag1 = 0;
int flag2 = 0;

const float ACTUAL_DISTANCE = 0.2;  // Real distance: 20 cm (0.2 m)
const float SIMULATED_DISTANCE = 5.0; // Fake distance for scaling (5 m)
float speed;

int ir_s1 = 2;
int ir_s2 = 3;
int buzzer = 11;

void setup() {
  Serial.begin(9600);
  lcd.init();
  lcd.backlight();
  pinMode(ir_s1, INPUT);
  pinMode(ir_s2, INPUT);
  pinMode(buzzer, OUTPUT);

  lcd.clear();
  lcd.begin(16, 2);
  lcd.setCursor(0, 0);
  lcd.print("   WELCOME TO ");
  lcd.setCursor(0, 1);
  lcd.print("Simple Circuits ");
  delay(2000);
  lcd.clear();
}

void loop() {
  if (digitalRead(ir_s1) == LOW && flag1 == 0) { timer1 = millis(); flag1 = 1; }
  if (digitalRead(ir_s2) == LOW && flag2 == 0) { timer2 = millis(); flag2 = 1; }

  if (flag1 == 1 && flag2 == 1) {
    if (timer1 > timer2) { Time = timer1 - timer2; }
    else if (timer2 > timer1) { Time = timer2 - timer1; }
    Time = Time / 1000; // Convert ms to seconds
    
    speed = (ACTUAL_DISTANCE / Time); // Speed in m/s
    speed = speed * (SIMULATED_DISTANCE / ACTUAL_DISTANCE); // Scale up
    speed = speed * 3.6; // Convert to km/h
  }

  if (speed == 0) {
    lcd.setCursor(0, 1);
    if (flag1 == 0 && flag2 == 0) { lcd.print("No Car Detected"); }
    else { lcd.print("Searching...    "); }
  }
  else {
    lcd.setCursor(0, 0);
    lcd.clear();
    lcd.print("Speed:");
    lcd.print(speed, 1);
    lcd.print("Km/Hr  ");
    lcd.setCursor(0, 1);
    if (speed > 50) { lcd.print("  Over Speeding  "); digitalWrite(buzzer, HIGH); }
    else { lcd.print("  Normal Speed   "); }
    delay(3000);
    digitalWrite(buzzer, LOW);
    speed = 0;
    flag1 = 0;
    flag2 = 0;
  }
}

Code Explanation:

Setup:

Initializes the LCD display, IR sensors, and buzzer. Sets up the welcome message that displays for 2 seconds on startup.

Loop:

Continuously monitors both IR sensors. When a vehicle is detected at the first sensor, it starts a timer. When detected at the second sensor, it stops the timer and calculates the speed using the time difference. The speed is then scaled to simulate a longer distance (5 meters) and converted to km/h. If the speed exceeds 50 km/h, it triggers the buzzer and displays an over-speed warning.

Why Choose This Design?

✅ Accurate Measurement: Precise speed calculation using time difference between two points
🚗 Realistic Simulation: Scaled to simulate actual road conditions despite small physical setup
📊 Clear Display: LCD shows speed in km/h with clear status messages
⚠️ Safety Alert: Audible buzzer warning for speeding vehicles
🛠️ DIY Friendly: Simple components and wiring, no soldering required
📱 Educational: Great for learning about sensors, timing, and physics calculations

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