Arduino - Traffic Light

In this tutorial, we are going to learn how to use Arduino control the traffic light module. In detail, we will learn:

Hardware Required

1×Arduino UNO or Genuino UNO
1×USB 2.0 cable type A/B
1×Traffic Light Module
1×Jumper Wires
1×(Optional) 9V Power Adapter for Arduino
1×(Recommended) Screw Terminal Block Shield for Arduino Uno
1×(Optional) Transparent Acrylic Enclosure For Arduino Uno

Or you can buy the following sensor kit:

1×DIYables Sensor Kit 30 types, 69 units
Please note: These are Amazon affiliate links. If you buy the components through these links, We will get a commission at no extra cost to you. We appreciate it.

About Traffic Light Module

Pinout

A traffic light module includes 4 pins:

  • GND pin: The ground pin, connect this pin to GND of Arduino.
  • R pin: The pin to control the red light, connect this pin to a digital output of Arduino.
  • Y pin: The pin to control the yellow light, connect this pin to a digital output of Arduino.
  • G pin: The pin to control the green light, connect this pin to a digital output of Arduino.
Traffic Light Pinout

How It Works

Wiring Diagram

Arduino traffic light Wiring Diagram

This image is created using Fritzing. Click to enlarge image

How To Program For Traffic Light module

  • Configure an Arduino's pins to the digital output mode by using pinMode() function
pinMode(PIN_RED, OUTPUT); pinMode(PIN_YELLOW, OUTPUT); pinMode(PIN_GREEN, OUTPUT);
digitalWrite(PIN_RED, HIGH); // turn on RED digitalWrite(PIN_YELLOW, LOW); // digitalWrite(PIN_GREEN, LOW); delay(RED_TIME); // keep red led on during a period of time

Arduino Code

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-traffic-light */ #define PIN_RED 2 // The Arduino pin connected to R pin of traffic light module #define PIN_YELLOW 3 // The Arduino pin connected to Y pin of traffic light module #define PIN_GREEN 4 // The Arduino pin connected to G pin of traffic light module #define RED_TIME 4000 // RED time in millisecond #define YELLOW_TIME 4000 // YELLOW time in millisecond #define GREEN_TIME 4000 // GREEN time in millisecond void setup() { pinMode(PIN_RED, OUTPUT); pinMode(PIN_YELLOW, OUTPUT); pinMode(PIN_GREEN, OUTPUT); } // the loop function runs over and over again forever void loop() { // red light on digitalWrite(PIN_RED, HIGH); // turn on digitalWrite(PIN_YELLOW, LOW); // turn off digitalWrite(PIN_GREEN, LOW); // turn off delay(RED_TIME); // keep red light on during a period of time // yellow light on digitalWrite(PIN_RED, LOW); // turn off digitalWrite(PIN_YELLOW, HIGH); // turn on digitalWrite(PIN_GREEN, LOW); // turn off delay(YELLOW_TIME); // keep yellow light on during a period of time // green light on digitalWrite(PIN_RED, LOW); // turn off digitalWrite(PIN_YELLOW, LOW); // turn off digitalWrite(PIN_GREEN, HIGH); // turn on delay(GREEN_TIME); // keep green light on during a period of time }

Quick Steps

  • Copy the above code and open with Arduino IDE
  • Click Upload button on Arduino IDE to upload code to Arduino
  • Check out the traffic light module
Arduino traffic light module
image source: diyables.io

It's important to note that the exact workings of a traffic light can vary depending on the specific design and technology used in different regions and intersections. The principles described above provide a general understanding of how traffic lights operate to manage traffic and enhance safety on the roads.

The code above demonstrates individual light control. Now, let's enhance the code for better optimization.

Arduino Code Optimization

  • Let's improve the code by implementing a function for light control.
/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-traffic-light */ #define PIN_RED 2 // The Arduino pin connected to R pin of traffic light module #define PIN_YELLOW 3 // The Arduino pin connected to Y pin of traffic light module #define PIN_GREEN 4 // The Arduino pin connected to G pin of traffic light module #define RED_TIME 2000 // RED time in millisecond #define YELLOW_TIME 1000 // YELLOW time in millisecond #define GREEN_TIME 2000 // GREEN time in millisecond #define RED 0 // Index in array #define YELLOW 1 // Index in array #define GREEN 2 // Index in array const int pins[] = { PIN_RED, PIN_YELLOW, PIN_GREEN }; const int times[] = { RED_TIME, YELLOW_TIME, GREEN_TIME }; void setup() { pinMode(PIN_RED, OUTPUT); pinMode(PIN_YELLOW, OUTPUT); pinMode(PIN_GREEN, OUTPUT); } // the loop function runs over and over again forever void loop() { // red light on trafic_light_on(RED); delay(times[RED]); // keep red light on during a period of time // yellow light on trafic_light_on(YELLOW); delay(times[YELLOW]); // keep yellow light on during a period of time // green light on trafic_light_on(GREEN); delay(times[GREEN]); // keep green light on during a period of time } void trafic_light_on(int light) { for (int i = RED; i <= GREEN; i++) { if (i == light) digitalWrite(pins[i], HIGH); // turn on else digitalWrite(pins[i], LOW); // turn off } }
  • Let's improve the code by using a for loop.
/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-traffic-light */ #define PIN_RED 2 // The Arduino pin connected to R pin of traffic light module #define PIN_YELLOW 3 // The Arduino pin connected to Y pin of traffic light module #define PIN_GREEN 4 // The Arduino pin connected to G pin of traffic light module #define RED_TIME 2000 // RED time in millisecond #define YELLOW_TIME 1000 // YELLOW time in millisecond #define GREEN_TIME 2000 // GREEN time in millisecond #define RED 0 // Index in array #define YELLOW 1 // Index in array #define GREEN 2 // Index in array const int pins[] = {PIN_RED, PIN_YELLOW, PIN_GREEN}; const int times[] = {RED_TIME, YELLOW_TIME, GREEN_TIME}; void setup() { pinMode(PIN_RED, OUTPUT); pinMode(PIN_YELLOW, OUTPUT); pinMode(PIN_GREEN, OUTPUT); } // the loop function runs over and over again forever void loop() { for (int light = RED; light <= GREEN; light ++) { trafic_light_on(light); delay(times[light]); // keep light on during a period of time } } void trafic_light_on(int light) { for (int i = RED; i <= GREEN; i ++) { if (i == light) digitalWrite(pins[i], HIGH); // turn on else digitalWrite(pins[i], LOW); // turn off } }
  • Let's improve the code by using millis() function intead of delay().
/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-traffic-light */ #define PIN_RED 2 // The Arduino pin connected to R pin of traffic light module #define PIN_YELLOW 3 // The Arduino pin connected to Y pin of traffic light module #define PIN_GREEN 4 // The Arduino pin connected to G pin of traffic light module #define RED_TIME 2000 // RED time in millisecond #define YELLOW_TIME 1000 // YELLOW time in millisecond #define GREEN_TIME 2000 // GREEN time in millisecond #define RED 0 // Index in array #define YELLOW 1 // Index in array #define GREEN 2 // Index in array const int pins[] = { PIN_RED, PIN_YELLOW, PIN_GREEN }; const int times[] = { RED_TIME, YELLOW_TIME, GREEN_TIME }; unsigned long last_time = 0; int light = RED; // start with RED light void setup() { pinMode(PIN_RED, OUTPUT); pinMode(PIN_YELLOW, OUTPUT); pinMode(PIN_GREEN, OUTPUT); trafic_light_on(light); last_time = millis(); } // the loop function runs over and over again forever void loop() { if ((millis() - last_time) > times[light]) { light++; if (light >= 3) light = RED; // new circle trafic_light_on(light); last_time = millis(); } // TO DO: your other code } void trafic_light_on(int light) { for (int i = RED; i <= GREEN; i++) { if (i == light) digitalWrite(pins[i], HIGH); // turn on else digitalWrite(pins[i], LOW); // turn off } }

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