Arduino Traffic Light Project: Circuit and Code

Build the signal at your school gate. Green to go, yellow to slow down, red to stop.

Parts you need

• Arduino Uno
• Red, yellow, green LEDs
• 3 × 220Ω resistors

Wiring

1. Pin 12 → red LED
2. Pin 11 → yellow LED
3. Pin 10 → green LED
4. All short legs → GND rail

Arduino code

int red = 12;
int yellow = 11;
int green = 10;

void setup() {
  pinMode(red, OUTPUT);
  pinMode(yellow, OUTPUT);
  pinMode(green, OUTPUT);
}

void loop() {
  digitalWrite(green, HIGH);
  delay(3000);
  digitalWrite(green, LOW);

  digitalWrite(yellow, HIGH);
  delay(1000);
  digitalWrite(yellow, LOW);

  digitalWrite(red, HIGH);
  delay(3000);
  digitalWrite(red, LOW);
}

Goal and tip

Goal: Light up all three colors in order.

Tip: Try this: make the green light stay on for 5 seconds.

Run this experiment in the free simulator