ESP8266 - Traffic Light

This tutorial instructs you how to use an ESP8266 to control a traffic light module. Specifically, we will cover the following aspects:

Establishing the connection between the traffic light module and ESP8266
Programming ESP8266 to oversee the RGB traffic light module
Implementing ESP8266 programming to manage the RGB traffic light module without relying on the delay() function

Hardware Preparation

1	×	ESP8266 NodeMCU
1	×	Micro USB Cable
1	×	Traffic Light Module
1	×	Jumper Wires
1	×	Breadboard
1	×	(Optional) Screw Terminal Expansion Board for ESP8266

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

Disclosure: Some of the links provided in this section are Amazon affiliate links. We may receive a commission for any purchases made through these links at no additional cost to you.
Additionally, some of these links are for products from our own brand, DIYables.

Overview of Traffic Light Module

Pinout

A traffic light module is equipped with four pins:

GND pin: Connect this pin to the GND of the ESP8266.
R pin: Manages the red light; connect this pin to a digital output of the ESP8266.
Y pin: Controls the yellow light; connect this pin to a digital output of the ESP8266.
G pin: Governs the green light; connect this pin to a digital output of the ESP8266.

How It Works

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

See more in ESP8266's pinout and how to supply power to the ESP8266 and other components.

How To Program For Traffic Light module

Configure an ESP8266'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

ESP8266 Code

/* * This ESP8266 NodeMCU code was developed by newbiely.com * * This ESP8266 NodeMCU code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp8266/esp8266-traffic-light */ #define PIN_RED D7 // The ESP8266 pin connected to R pin of traffic light module #define PIN_YELLOW D6 // The ESP8266 pin connected to Y pin of traffic light module #define PIN_GREEN D5 // The ESP8266 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 repeats indefinitely 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 }

Detailed Instructions

To get started with ESP8266 on Arduino IDE, follow these steps:

Check out the how to setup environment for ESP8266 on Arduino IDE tutorial if this is your first time using ESP8266.
Wire the components as shown in the diagram.
Connect the ESP8266 board to your computer using a USB cable.
Open Arduino IDE on your computer.
Choose the correct ESP8266 board, such as (e.g. NodeMCU 1.0 (ESP-12E Module)), and its respective COM port.
Copy the above code and open with Arduino IDE
Click Upload button on Arduino IDE to upload code to ESP8266
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.

ESP8266 Code Optimization

Let's improve the code by implementing a function for light control.

/* * This ESP8266 NodeMCU code was developed by newbiely.com * * This ESP8266 NodeMCU code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp8266/esp8266-traffic-light */ #define PIN_RED D7 // The ESP8266 pin connected to R pin of traffic light module #define PIN_YELLOW D6 // The ESP8266 pin connected to Y pin of traffic light module #define PIN_GREEN D5 // The ESP8266 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 repeats indefinitely 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.

/* * This ESP8266 NodeMCU code was developed by newbiely.com * * This ESP8266 NodeMCU code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp8266/esp8266-traffic-light */ #define PIN_RED D7 // The ESP8266 pin connected to R pin of traffic light module #define PIN_YELLOW D6 // The ESP8266 pin connected to Y pin of traffic light module #define PIN_GREEN D5 // The ESP8266 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 repeats indefinitely 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().

/* * This ESP8266 NodeMCU code was developed by newbiely.com * * This ESP8266 NodeMCU code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp8266/esp8266-traffic-light */ #define PIN_RED D7 // The ESP8266 pin connected to R pin of traffic light module #define PIN_YELLOW D6 // The ESP8266 pin connected to Y pin of traffic light module #define PIN_GREEN D5 // The ESP8266 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 repeats indefinitely 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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