Arduino Traffic Light System

  This circuit was tested and worked properly!

Here is a traffic light system based on Arduino that can be use in a 3-way ond 4-way intersections. It has an additional blinking orange led that is used to signal when the pedestrians can cross the street. The code is a little bit complicated but I think you can understand how it works, right?

Check out this video below to see how the traffic lights system is working.
The code is written based on 4 situations:

1. the first traffic light (TF1) has the red signal and the pedestrians ON; the second one (TF2) has green ON.
2. TF1 has red and yellow ON; TF2 has yellow ON
3. TF1 is green now and TF2 is red and pedestrians ON
4. TF1 is yellow and TF2 is red and yellow

The schematic is too easy, all you have to do is connect the leds in series with a 470Ω resistor between the ground and the Arduino pins mentioned in the code.

Code of the Arduino Traffic Lights Sketch

// Source: http://www.electroschematics.com/10178/arduino-traffic-light-system/
int trafficLights1[] = {2,3,4,5}; // red, yellow, green, pedestrians led pins
int trafficLights2[] = {6,7,8,9}; // red, yellow, green, pedestrians led pins
int situations = 4;
int duration[] = {8000,3000,10000,3000}; // duration of each situation
long previousCars = 0;
long previousPeds = 0;
long interval = 300; //blink interval for pedestrians
int ledState = LOW;
int state;
int i = 0;

void setup()
{
  for(int i = 0; i < 4; i++) {
   pinMode(trafficLights1[i], OUTPUT);
   pinMode(trafficLights2[i], OUTPUT);
  }
 Serial.begin(9600);
}

void loop()
{ 
 unsigned long currentMillis = millis();  
 if(currentMillis - previousCars < duration[i]) {   
  situation(i);  
 } else { 
  previousCars = currentMillis; 
  if(i >= situations) {
   i = 0;
   } else {
   i++;
  }  
 }
}

void activateTrafficLight1(String lights, int pedestrians) 
{ 
 for(int x = 0; x < 3; x++) 
 {
  if(lights[x] == '0') state = LOW;
  if(lights[x] == '1') state = HIGH;
  digitalWrite(trafficLights1[x], state); 
 }
 if(pedestrians == 1) {
  blinkPed(trafficLights1[3]);
 } else {
  digitalWrite(trafficLights1[3], LOW);
 }
}

void activateTrafficLight2(String lights, int pedestrians)
{ 
 for(int x = 0; x < 3; x++)
 {
  if(lights[x] == '0') state = LOW;
  if(lights[x] == '1') state = HIGH;
  digitalWrite(trafficLights2[x], state);
 }
 if(pedestrians == 1) {
  blinkPed(trafficLights2[3]);
 } else {
  digitalWrite(trafficLights2[3], LOW);
 }
}

void situation(int i)
{
 switch(i){
  case 0: 
   activateTrafficLight1("100",1); // 100 means red ON, yellow OFF, green OFF
   activateTrafficLight2("001",0); // the second parameter is for pedestrians
   break;       // 1 is ON and 0 is OFF
  case 1: 
   activateTrafficLight1("110",0); // 110: red ON, yellow ON, green OFF
   activateTrafficLight2("010",0);
   break; 
  case 2: 
   activateTrafficLight1("001",0);
   activateTrafficLight2("100",1);
   break;
  case 3: 
   activateTrafficLight1("010",0);
   activateTrafficLight2("110",0);
   break; 
 }
}

void blinkPed(int ped) {
 unsigned long currentMillis = millis();
 if(currentMillis - previousPeds > interval) {  
  previousPeds = currentMillis;  
  if (ledState == LOW)
  ledState = HIGH;
  else
  ledState = LOW;
  digitalWrite(ped, ledState);
 } 
}