How to Build a Traffic Light with Arduino

Overview

This project deals with a 2-road crossing traffic light. These lights work the same as our traffic system does here. Resistors are used so that no extra current is given to the LEDs, as the extra current can damage them.

In this traffic light signal, when signal 1 is red, signal 2 will be green and vice versa.

Hardware required 

1. Arduino Uno R3
2. LED
3. Resistor
4. Jumper Wires

Schematic Diagram

Fig 1.  Circuit Diagram

Arduino Code : 

// light one
int red1 = 10;
int yellow1 = 9;
int green1 = 8;

// light two
int red2 = 13;
int yellow2 = 12;
int green2 = 11;

void setup(){
    // light one
    pinMode(red1, OUTPUT);
    pinMode(yellow1, OUTPUT);
    pinMode(green1, OUTPUT);

    // light two
    pinMode(red2, OUTPUT);
    pinMode(yellow2, OUTPUT);
    pinMode(green2, OUTPUT);
}

void loop(){
    changeLights();
    delay(15000);
}

void changeLights(){
    // turn both yellows on
    digitalWrite(green1, LOW);
    digitalWrite(yellow1, HIGH);
    digitalWrite(yellow2, HIGH);
    delay(5000);

    // turn both yellows off, and opposite green and red
    digitalWrite(yellow1, LOW);
    digitalWrite(red1, HIGH);
    digitalWrite(yellow2, LOW);
    digitalWrite(red2, LOW);
    digitalWrite(green2, HIGH);
    delay(5000);

    // both yellows on again
    digitalWrite(yellow1, HIGH);
    digitalWrite(yellow2, HIGH);
    digitalWrite(green2, LOW);
    delay(3000);

    // turn both yellows off, and opposite green and red
    digitalWrite(green1, HIGH);
    digitalWrite(yellow1, LOW);
    digitalWrite(red1, LOW);
    digitalWrite(yellow2, LOW);
    digitalWrite(red2, HIGH);
    delay(5000);
}

Precautions

1. Connections should be done properly.
2. Arduino is case Sensitive, so code accordingly.
3. Give different and appropriate colours to the wires.

Conclusion

This project demonstrates how a simple Arduino Uno can effectively control a 2-road traffic light system using LEDs, resistors, and basic coding. By simulating real-world traffic signals, beginners can strengthen their understanding of microcontrollers, electronics, and logic building.

Projects like these are a stepping stone toward more advanced embedded systems and IoT applications. To further enhance your learning journey and explore structured programs, check out coding schools.