Arduino Project for Traffic Light: Simple Code and Setup

An Arduino traffic light project uses digitalWrite() to control LEDs representing red, yellow, and green lights in sequence. You connect LEDs to Arduino pins and write a loop to turn them on and off with delay() for timing.

Syntax

The basic syntax for controlling LEDs in an Arduino traffic light project involves setting pin modes and using digitalWrite(pin, HIGH) to turn an LED on and digitalWrite(pin, LOW) to turn it off. The delay(milliseconds) function pauses the program to keep the light on for a set time.

• pinMode(pin, OUTPUT): Sets the pin as an output to control an LED.
• digitalWrite(pin, HIGH): Turns the LED on.
• digitalWrite(pin, LOW): Turns the LED off.
• delay(ms): Waits for the specified milliseconds.

arduino

void setup() {
  pinMode(2, OUTPUT); // Red LED
  pinMode(3, OUTPUT); // Yellow LED
  pinMode(4, OUTPUT); // Green LED
}

void loop() {
  digitalWrite(2, HIGH); // Red ON
  delay(5000);          // Wait 5 seconds
  digitalWrite(2, LOW);  // Red OFF

  digitalWrite(3, HIGH); // Yellow ON
  delay(2000);          // Wait 2 seconds
  digitalWrite(3, LOW);  // Yellow OFF

  digitalWrite(4, HIGH); // Green ON
  delay(5000);          // Wait 5 seconds
  digitalWrite(4, LOW);  // Green OFF
}

Example

This example shows a simple traffic light sequence using three LEDs connected to pins 2, 3, and 4. The red light stays on for 5 seconds, yellow for 2 seconds, and green for 5 seconds, repeating endlessly.

arduino

void setup() {
  pinMode(2, OUTPUT); // Red LED
  pinMode(3, OUTPUT); // Yellow LED
  pinMode(4, OUTPUT); // Green LED
}

void loop() {
  // Red light
  digitalWrite(2, HIGH);
  digitalWrite(3, LOW);
  digitalWrite(4, LOW);
  delay(5000);

  // Yellow light
  digitalWrite(2, LOW);
  digitalWrite(3, HIGH);
  digitalWrite(4, LOW);
  delay(2000);

  // Green light
  digitalWrite(2, LOW);
  digitalWrite(3, LOW);
  digitalWrite(4, HIGH);
  delay(5000);
}

Output

Red LED ON for 5 seconds, then Yellow LED ON for 2 seconds, then Green LED ON for 5 seconds, repeating.

Common Pitfalls

Common mistakes include not setting the pin modes to OUTPUT, which prevents LEDs from lighting up. Another error is forgetting to turn off other LEDs before turning one on, causing multiple lights to be on simultaneously. Also, wiring LEDs without resistors can damage them or the Arduino.

arduino

/* Wrong: Missing pinMode setup */
void setup() {
  // pinMode calls missing
}

void loop() {
  digitalWrite(2, HIGH); // Won't work properly
  delay(1000);
}

/* Correct: Proper pinMode setup */
void setup() {
  pinMode(2, OUTPUT);
}

void loop() {
  digitalWrite(2, HIGH);
  delay(1000);
  digitalWrite(2, LOW);
  delay(1000);
}

Quick Reference

• pinMode(pin, OUTPUT): Prepare pin to control LED.
• digitalWrite(pin, HIGH): Turn LED on.
• digitalWrite(pin, LOW): Turn LED off.
• delay(ms): Pause program for timing.
• Use resistors: Protect LEDs and Arduino pins.

Key Takeaways

Set pin modes to OUTPUT before controlling LEDs.

Use digitalWrite to turn LEDs on and off in sequence.

Use delay to control how long each light stays on.

Always include resistors to protect LEDs and Arduino pins.

Turn off other LEDs before turning one on to avoid overlap.