The file that is currently on an Arduino Uno with a serial number of 74132343530351609150

Pushbutton_Red_Green_LED.ino

/*

Based on http://www.makeuseof.com/tag/arduino-traffic-light-controller/

USE_GITHUB_USERNAME=mark-wilson

*/

// Pins for coloured LEDs
int red = 11;
int green = 12;
int light = 0;

int button = 2; // Pushbutton on pin 2
int buttonValue = 0; // Button defaults to 0 (LOW)

void setup(){
  // Set up pins with LEDs as output devices and switch for input
  pinMode(red,OUTPUT);
  pinMode(green,OUTPUT);
  pinMode(button,INPUT);
}

void loop(){
  // Read the value of the pushbutton switch
  buttonValue = digitalRead(button);
  if (buttonValue == HIGH){
    changeLights();
    delay(15000); // Wait 15 seconds before reading again
  }
}
  
void changeLights(){
  // Change the lights based on current value: 0 is not set; 1 is green; 2 is red
  switch (light) {
    case 1:
      turnLightRed();
      break;
    case 2:
      turnLightGreen();
      break;
    default:
      turnLightRed();
  }
}

void turnLightGreen(){
  // Turn off the red and turn on the green
  digitalWrite(red,LOW);
  digitalWrite(green,HIGH);
  light = 1;
}

void turnLightRed(){
  // Turn off the green and turn on the red
  digitalWrite(green,LOW);
  digitalWrite(red,HIGH);
  light = 2;
}