Traffic Lights Arduino

You are now going to create a set of traffic lights that will change from green to red, via amber, and back again, after a set length of time using the four-state UK, you can modify the code and colors to meke them work like the traddic lights in your own country. First, though, make the project as it is and change it once you know how it works.

Parts Required

• Breadboard
• Red Diffused LED
• Yellow Diffused LED
• Green Diffused LED
• 3 x 150 ohm Resistors*
• Jumper Wires

*or whatever value you require for your type of LED

Connect It Up

Connect your circuits as show Figure below. This time you connect three LEDs with the anode of each one going to Digital Pins 8, 9 and 10 via a 150 ohm resistor each.

Take a jumper wire from ground of the Arduino to ground rail at the top of the breadboard; a connected to the cathode. (For this simple circuit, it doesn't matter if the resistor is connected to the anode or cathode).

Image Source: Book Beggining Arduino. Page: 36

Enter the Code

int ledDelay = 5000;// delay in between changes
int redPin = 10;
int yellowPin = 9;
int greenPin = 8;

void setup (){
  pinMode(redPin, OUTPUT);
  pinMode(yellowPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
}

void loop(){
  digitalWrite(redPin,HIGH);
  delay(ledDelay); // wait 5 seconds
 
  digitalWrite(yellowPin, HIGH);
  delay(2000);// wait 2 seconds
 
  digitalWrite(greenPin, HIGH); // turn green on
  digitalWrite(redPin, LOW); // turn red off
  digitalWrite(yellowPin, LOW); // turn yellow off
  delay(ledDelay); // wait ledDelay milliseconds
 
  digitalWrite(yellowPin,HIGH); // turn yellow on
  digitalWrite(greenPin, LOW); // turn green off
  delay(2000); // wait 2 seconds
 
  digitalWrite(yellowPin, LOW); // turn yellow off
  // now our loop repeats
}

Figure: The four states of the UK traffic lightsystem (Image Source: Book Beggining Arduino. Page: 37)

The code can be downloaded HERE.

Source: Excerpted and adapted from the Book Beginning Arduino, page 34-37.

Image Saurce: http://www.amazon.co.uk/Beginning-Arduino-Michael-McRoberts/dp/1430232404

Hope it's useful....