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In this tutorial, we will explore how to utilize the ESP32 to control a traffic light module. In detail, we will learn:
How to connect the traffic light module to ESP32
How to program ESP32 to control RGB traffic light module
How to program ESP32 to control RGB traffic light module without using delay() function
Hardware Used In This Tutorial
| 1 | × | ESP-WROOM-32 Dev Module | |
| 1 | × | USB Cable Type-C | |
| 1 | × | Traffic Light Module | |
| 1 | × | Jumper Wires | |
| 1 | × | (Recommended) ESP32 Screw Terminal Adapter |
Or you can buy the following sensor kit:
| 1 | × | DIYables Sensor Kit 30 types, 69 units |
Disclosure: some of these links are affiliate links. We may earn a commission on your purchase at no extra cost to you. We appreciate it.
Introduction to Traffic Light Module
Pinout
A traffic light module includes 4 pins:
GND pin: The ground pin, connect this pin to GND of ESP32.
R pin: The pin to control the red light, connect this pin to a digital output of ESP32.
Y pin: The pin to control the yellow light, connect this pin to a digital output of ESP32.
G pin: The pin to control the green light, connect this pin to a digital output of ESP32.
How It Works
Wiring Diagram
This image is created using Fritzing. Click to enlarge image
If you're unfamiliar with how to supply power to the ESP32 and other components, you can find guidance in the following tutorial: How to Power ESP32.
With breadboard
This image is created using Fritzing. Click to enlarge image
How To Program For Traffic Light module
Configure an ESP32'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 REDdigitalWrite(PIN_YELLOW, LOW); //digitalWrite(PIN_GREEN, LOW);delay(RED_TIME); // keep red led on during a period of time
ESP32 Code
/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-traffic-light */#define PIN_RED 25 // The ESP32 pin GPIO25 connected to R pin of traffic light module#define PIN_YELLOW 26 // The ESP32 pin GPIO26 connected to Y pin of traffic light module#define PIN_GREEN 27 // The ESP32 pin GPIO27 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 millisecondvoid setup() { pinMode(PIN_RED, OUTPUT); pinMode(PIN_YELLOW, OUTPUT); pinMode(PIN_GREEN, OUTPUT);}// the loop function runs over and over again forevervoid 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 Instructions
If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
Do the wiring as above image.
Connect the ESP32 board to your PC via a micro USB cable
Open Arduino IDE on your PC.
Select the right ESP32 board (e.g. ESP32 Dev Module) and COM port.
Copy the above code and open with Arduino IDE
Click Upload button on Arduino IDE to upload code to ESP32
Check out the traffic light module
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.
ESP32 Code Optimization
Let's improve the code by implementing a function for light control.
/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-traffic-light */#define PIN_RED 25 // The ESP32 pin GPIO25 connected to R pin of traffic light module#define PIN_YELLOW 26 // The ESP32 pin GPIO26 connected to Y pin of traffic light module#define PIN_GREEN 27 // The ESP32 pin GPIO27 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 arrayconst 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 forevervoid 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.
/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-traffic-light */#define PIN_RED 25 // The ESP32 pin GPIO25 connected to R pin of traffic light module#define PIN_YELLOW 26 // The ESP32 pin GPIO26 connected to Y pin of traffic light module#define PIN_GREEN 27 // The ESP32 pin GPIO27 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 arrayconst 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 forevervoid 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().
/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-traffic-light */#define PIN_RED 25 // The ESP32 pin GPIO25 connected to R pin of traffic light module#define PIN_YELLOW 26 // The ESP32 pin GPIO26 connected to Y pin of traffic light module#define PIN_GREEN 27 // The ESP32 pin GPIO27 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 arrayconst 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 lightvoid 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 forevervoid 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 }}
Video Tutorial
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