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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:
- How to connect the traffic light module to Arduino
- How to program Arduino to control RGB traffic light module
- How to program Arduino to control RGB traffic light module without using delay() function
Hardware Required
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| 1 | × | DIYables Sensor Kit (30 sensors/displays) | |
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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.
How It Works
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);
- Program to turn ON red light by using digitalWrite() function:
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
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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