How to make Traffic lights with Arduino uno

 This project implements a traffic light system with a countdown timer, designed using an Arduino microcontroller. It controls a sequence of traffic lights (red, yellow, and green) and a 7-segment display counter. Here’s a detailed description:

Features:

1. Traffic Light Phases:

   • Red Light Phase: The red light is active for 9 seconds, during which a countdown is displayed on a 7-segment display.
   • Yellow Light Phase: The yellow light blinks for 2 seconds before switching to green.
   • Green Light Phase: The green light is active for 9 seconds, with the countdown displayed.

2. Countdown Display:

   • A 7-segment display shows the countdown from 9 to 0 during the red and green light phases. This is achieved using a 4511 IC, with the display driven by 4 output pins.

Components:

1. Traffic Light LEDs:
   • Red, yellow, and green LEDs are connected to digital pins 11, 12, and 13 respectively.
   • Controlled using digitalWrite to turn them on or off.
2. 7-Segment Display:
   • Driven by a 4511 IC, connected to pins 4, 5, 6, and 7.
   • Displays the countdown timer during the active phases of red and green lights.

Workflow:

1. Setup Phase:

   • Configures the pins for the LEDs and the 7-segment display.
   • Initializes the system with the red light on and the counter set to 9.

2. Loop Phase:

• Executes the traffic light phases in sequence:
  • Red Light Phase: Lights the red LED and counts down from 9 to 0.
  • Yellow Light Phase: Blinks the yellow LED for 2 seconds.
  • Green Light Phase: Lights the green LED and counts down from 9 to 0.
• Repeats the cycle continuously.

Schematic:

Code:

// Pin Definitions

#define GREEN_LIGHT 13

#define YELLOW_LIGHT 12

#define RED_LIGHT 11

const int counterPins[] = {7, 6, 5, 4}; // Pins connected to 4511 (7-segment IC)

// Variables

int counter = 9; // Start countdown from 9

void setup() {

  // Setup Traffic Light Pins

  pinMode(GREEN_LIGHT, OUTPUT);

  pinMode(YELLOW_LIGHT, OUTPUT);

  pinMode(RED_LIGHT, OUTPUT);

  // Setup Counter Pins

  for (int i = 0; i < 4; i++) {

    pinMode(counterPins[i], OUTPUT);

  }

  // Initialize with Red Light and Counter at 9

  digitalWrite(GREEN_LIGHT, LOW);

  digitalWrite(YELLOW_LIGHT, LOW);

  digitalWrite(RED_LIGHT, HIGH);

  updateCounter(counter);

}

void loop() {

  // Red Light Phase

  digitalWrite(RED_LIGHT, HIGH);

  digitalWrite(YELLOW_LIGHT, LOW);

  digitalWrite(GREEN_LIGHT, LOW);

  countdown(9); // Countdown from 9 to 0 (9 seconds)

  // Yellow Light Phase (Blinking for 2 seconds)

  for (int i = 0; i < 4; i++) { // Blinks 4 times (2 seconds)

    digitalWrite(YELLOW_LIGHT, HIGH);

    delay(250);

    digitalWrite(YELLOW_LIGHT, LOW);

    delay(250);

  }

  // Green Light Phase

  digitalWrite(RED_LIGHT, LOW);

  digitalWrite(YELLOW_LIGHT, LOW);

  digitalWrite(GREEN_LIGHT, HIGH);

  countdown(9); // Countdown from 9 to 0 (9 seconds)

  // Loop starts again

}

// Update the counter value on the 4511 IC

void updateCounter(int value) {

  for (int i = 0; i < 4; i++) {

    digitalWrite(counterPins[i], (value >> i) & 0x01);

  }

}

// Countdown logic

void countdown(int startValue) {

  counter = startValue;

  while (counter >= 0) {

    updateCounter(counter);

    delay(1000); // 1 second delay for each count

    counter--;

  }

}

Code Highlights:

• Pin Definitions: Predefined constants improve code readability by labeling the pin numbers.
• Modular Functions:
  • updateCounter(int value): Updates the display based on the counter value.
  • countdown(int startValue): Handles the countdown logic with a 1-second delay for each decrement.
• Timing Control: Uses delay() for time intervals, providing precise timing for LED and countdown changes.

Applications:

This project can be used as:

• A simulation of a basic traffic light system for educational purposes.
• A starting point for more complex traffic management systems.