Arduino UNO R4 - Traffic Light

In this guide, we will learn how to control a traffic light module using Arduino UNO R4. We will cover:

Arduino UNO R4 traffic light

Hardware Preparation

1×Arduino UNO R4 WiFi
1×Arduino UNO R4 Minima (Alternatively)
1×USB Cable Type-C
1×Traffic Light Module
1×Jumper Wires
1×(Optional) 9V Power Adapter for Arduino UNO R4
1×(Recommended) Screw Terminal Block Shield for Arduino Uno
1×(Optional) Transparent Acrylic Enclosure For Arduino Uno

Or you can buy the following sensor kits:

1×DIYables Sensor Kit (30 sensors/displays)
1×DIYables Sensor Kit (18 sensors/displays)
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Overview of Traffic Light Module

Pinout

A traffic light module has 4 pins:

  • GND pin: This is the ground pin. Connect it to the GND on the Arduino UNO R4.
  • R pin: This pin controls the red light. Connect it to a digital output on the Arduino UNO R4.
  • Y pin: This pin controls the yellow light. Connect it to a digital output on the Arduino UNO R4.
  • G pin: This pin controls the green light. Connect it to a digital output on the Arduino UNO R4.
Traffic Light Pinout

How It Works

Wiring Diagram

The wiring diagram between Arduino UNO R4 traffic light

This image is created using Fritzing. Click to enlarge image

How To Program For Traffic Light module

  • Set the pins of an Arduino UNO R4 as digital outputs by using the pinMode() function.
pinMode(PIN_RED, OUTPUT); pinMode(PIN_YELLOW, OUTPUT); pinMode(PIN_GREEN, OUTPUT);
  • Program to activate the red light using the digitalWrite() function:
digital-Write(PIN_RED, HIGH); // Set the RED LED to on digitalWrite(PIN_YELLOW, LOW); // Set the YELLOW LED to off digitalWrite(PIN_GREEN, LOW); // Set the GREEN LED to off delay(RED_TIME); // Maintain RED LED on state for the duration defined by RED_TIME

Arduino UNO R4 Code

/* * This Arduino UNO R4 code was developed by newbiely.com * * This Arduino UNO R4 code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-uno-r4/arduino-uno-r4-traffic-light */ #define PIN_RED 2 // The Arduino UNO R4 pin connected to R pin of traffic light module #define PIN_YELLOW 3 // The Arduino UNO R4 pin connected to Y pin of traffic light module #define PIN_GREEN 4 // The Arduino UNO R4 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 }

Detailed Instructions

Follow these instructions step by step:

  • If this is your first time using the Arduino Uno R4 WiFi/Minima, refer to the tutorial on setting up the environment for Arduino Uno R4 WiFi/Minima in the Arduino IDE.
  • Connect the traffic light module the Arduino Uno R4 according to the provided diagram.
  • Connect the Arduino Uno R4 board to your computer using a USB cable.
  • Launch the Arduino IDE on your computer.
  • Select the appropriate Arduino Uno R4 board (e.g., Arduino Uno R4 WiFi) and COM port.
  • Copy the code and open it in Arduino IDE.
  • Click the Upload button in Arduino IDE to upload the code to Arduino UNO R4.
  • Check out the traffic light module.

Traffic lights work differently depending on their design used in each area. The information given here offers a basic idea of how traffic lights help control traffic.

The code shown above lets you control each light separately. Now, we will improve the code to make it work better.

Arduino UNO R4 Code Optimization

  • Let's make the code better by adding a function to control the light.
/* * This Arduino UNO R4 code was developed by newbiely.com * * This Arduino UNO R4 code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-uno-r4/arduino-uno-r4-traffic-light */ #define PIN_RED 2 // The Arduino UNO R4 pin connected to R pin of traffic light module #define PIN_YELLOW 3 // The Arduino UNO R4 pin connected to Y pin of traffic light module #define PIN_GREEN 4 // The Arduino UNO R4 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 } }
  • We can make the code better by using a for loop.
/* * This Arduino UNO R4 code was developed by newbiely.com * * This Arduino UNO R4 code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-uno-r4/arduino-uno-r4-traffic-light */ #define PIN_RED 2 // The Arduino UNO R4 pin connected to R pin of traffic light module #define PIN_YELLOW 3 // The Arduino UNO R4 pin connected to Y pin of traffic light module #define PIN_GREEN 4 // The Arduino UNO R4 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 make the code better by using the millis() function instead of delay().
/* * This Arduino UNO R4 code was developed by newbiely.com * * This Arduino UNO R4 code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-uno-r4/arduino-uno-r4-traffic-light */ #define PIN_RED 2 // The Arduino UNO R4 pin connected to R pin of traffic light module #define PIN_YELLOW 3 // The Arduino UNO R4 pin connected to Y pin of traffic light module #define PIN_GREEN 4 // The Arduino UNO R4 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 } }

Video Tutorial

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