Last night I wrote a blog post about the “traffic lights” for my office. The trouble with the original setup was that the light was set to a particular state until I edited the code and uploaded a new version to the Arduino.

I was so excited about having something working that I hadn’t actually finished reading the Arduino Programming For Beginners: The Traffic Light Controller post that I referenced. Scroll down a bit further and James Bruce extends his traffic light sequence to simulate someone pressing a button to change the lights (e.g. to cross the road).

I worked on this to come up with something similar – using a variation on James’ wiring diagram (except with 2 LEDs rather than 3, and using pins 11 and 12 for my LEDs and 2 for the pushbutton switch), I now have a setup which waits for the button to be pressed, then sets the red LED, until the button is pressed again (when it goes green), etc.

My code is available on github but here’s the current version (just in case I lose that version as I get to grips with source control…):

/*
Red/green LED indicator with pushbutton control
Based on http://www.makeuseof.com/tag/arduino-traffic-light-controller/
*/

// 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;
}

Now I’m wondering how long it will be before the kids work out that they too can change the status (like pushing the button at a pedestrian crossing!)…