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Arduino UNO Traffic Light System with Countdown Display and Melody

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Circuit Documentation

Summary

This circuit is designed to control a traffic light system with a countdown display and a piezo speaker for sound alerts. The system is managed by an Arduino UNO microcontroller, which interfaces with a seven-segment display, a traffic light module, a piezo speaker, and a servo motor. The Arduino UNO runs a program that controls the traffic light sequence, displays countdown numbers on the seven-segment display, and plays a melody through the piezo speaker.

Component List

  1. Arduino UNO

    • Description: A microcontroller board based on the ATmega328P.
    • Pins: UNUSED, IOREF, Reset, 3.3V, 5V, GND, Vin, A0, A1, A2, A3, A4, A5, SCL, SDA, AREF, D13, D12, D11, D10, D9, D8, D7, D6, D5, D4, D3, D2, D1, D0

  2. Traffic Light

    • Description: A module with three LEDs (Green, Yellow, Red) to simulate a traffic light.
    • Pins: Green, Yellow, Red, GND

  3. Piezo Speaker

    • Description: A small speaker used to generate sound.
    • Pins: pin1, pin2

  4. MG996R Servo Motor

    • Description: A high-torque servo motor.
    • Pins: GND, VCC, SIG

  5. Seven Segment Display (Wokwi Compatible)

    • Description: A display module used to show numbers.
    • Pins: G, F, COM.2, B, A, E, D, COM.1, C, DP

  6. Resistors

    • Description: Resistors used to limit current.
    • Pins: pin1, pin2
    • Properties:
      • Resistance: 200 Ohms (6 instances)
      • Resistance: 220 Ohms (1 instance)

Wiring Details

Arduino UNO

Traffic Light

Piezo Speaker

MG996R Servo Motor

Seven Segment Display (Wokwi Compatible)

Resistors

Code Documentation

#include <Servo.h>      // Include the Servo library

Servo myServo;               // Create a Servo object

// Define 7-segment display pins
int segmentPins[] = {2, 3, 4, 5, 6, 7, 8}; // A, B, C, D, E, F, G

// Define the numbers to be displayed (0-9)
const byte numToSeg[10] = 
{
  // A B C D E F G (segment ON = 1, OFF = 0)
  B00111111,  // 0
  B00000110,  // 1
  B01011011,  // 2
  B01001111,  // 3
  B01100110,  // 4
  B01101101,  // 5
  B01111101,  // 6
  B00000111,  // 7
  B01111111,  // 8
  B01000000,  // -
};

#define NOTE_A3  220
#define NOTE_B3  247
#define NOTE_G3  196

// notes in the melody:
int melody[] = {
  NOTE_B3, NOTE_A3, NOTE_G3, NOTE_A3, NOTE_B3
};

// note durations: 4 = quarter note, 8 = eighth note, etc.:
int noteDurations[] = {
  4, 8, 4, 8, 4
};

void playMelody() 
{
  // Iterate over the notes of the melody:
  for (int thisNote = 0; thisNote < 5; thisNote++) {
    int noteDuration = 2000 / noteDurations[thisNote];
    tone(10, melody[thisNote], noteDuration); // Play melody on the buzzer (pin 10)
    int pauseBetweenNotes = noteDuration * 1.30;
    delay(pauseBetweenNotes);
    noTone(10); // Stop the tone
  }
}

void setup() {
  Serial.begin(9600);        // Initialize Serial communication
  
  // Set pins for 7-segment display as OUTPUT
  for (int i = 0; i < 7; i++) {
    pinMode(segmentPins[i], OUTPUT);
    digitalWrite(segmentPins[i], LOW);
  }
  
  pinMode(11, OUTPUT);       // RED light
  digitalWrite(11, LOW);      // Turn off red light
  
  pinMode(12, OUTPUT);       // Yellow light
  digitalWrite(12, LOW);      // Turn off yellow light
  
  pinMode(13, OUTPUT);       // GREEN light
  digitalWrite(13, LOW);      // Turn off yellow light
  
  pinMode(10, OUTPUT);       // Buzzer
  
  myServo.attach(9);         // Attach the servo to pin 9
  myServo.write(0);         // Set servo to remove the obstacle initially
}

void displayDigit(int digit) 
{
  // Turn off all segments first to clear the display
  for (int i = 0; i < 7; i++) {
    digitalWrite(segmentPins[i], LOW);
  }

  // Get the segment pattern for the current digit
  byte segments = numToSeg[digit];

  // Turn on the correct segments based on the pattern
  for (int i = 0; i < 7; i++) {
    if (segments & (1 << i)) {
      digitalWrite(segmentPins[i], HIGH);  // Turn ON the segment
    }
  }
}

void loop() {
  
  // RED Light and Melody
  digitalWrite(11, HIGH);
  playMelody();               // Play melody before green light
  myServo.write(0); // Engage the obstacle (block