Arduino UNO R4 - Blink multiple LED

This guide shows you how to program an Arduino UNO R4 to make multiple LEDs blink at different frequency without using the delay() function. It offers the code in two ways:

Arduino UNO R4 blink multiple LEDs
Arduino UNO R4 blink multiple LEDs using array

We will demonstrate with three LEDs. You can easily adjust this for two LEDs, four LEDs, or more.

Hardware Preparation

1	×	Arduino UNO R4 WiFi
1	×	Arduino UNO R4 Minima (Alternatively)
1	×	USB Cable Type-C
1	×	LED
1	×	220 ohm resistor
1	×	Breadboard
1	×	Jumper Wires
1	×	(Recommended) Screw Terminal Block Shield for Arduino UNO R4
1	×	(Recommended) Breadboard Shield For Arduino UNO R4
1	×	(Recommended) Enclosure For Arduino UNO R4

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 LED

Explore our comprehensive guide on LEDs, covering how to connect the hardware, how they work, how to set it up with Arduino UNO R4, and programming steps. Find out more here:

Arduino UNO R4 - LED tutorial

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

Arduino UNO R4 Code - Blink Multiple LEDs

To blink several LEDs at the same time, we should not use the delay() function. This function stops other code from running, which means we cannot blink different LEDs together. We should use the millis() function to control the timing instead.

For beginners, managing timestamps when blinking several LEDs can be difficult. Luckily, the ezLED library makes this easier by dealing with timestamp management inside the library. This means users don't have to worry about managing timestamps themselves when using the library. Also, using a group of LEDs can make the code clearer and shorter.

/* * 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-blink-multiple-led */ #include <ezLED.h> // ezLED library by ArduinoGetStarted.com #define PIN_LED_1 7 // The Arduino UNO R4 pin connected to LED 1 #define PIN_LED_2 8 // The Arduino UNO R4 pin connected to LED 2 #define PIN_LED_3 9 // The Arduino UNO R4 pin connected to LED 3 ezLED led1(PIN_LED_1); // create ezLED object that attach to pin PIN_LED_1 ezLED led2(PIN_LED_2); // create ezLED object that attach to pin PIN_LED_2 ezLED led3(PIN_LED_3); // create ezLED object that attach to pin PIN_LED_3 void setup() { Serial.begin(9600); led1.blink(800, 200); // 800ms ON, 200ms OFF, blink immediately led2.blink(500, 500); // 500ms ON, 500ms OFF, blink immediately led3.blink(500, 500, 500); // 500ms ON, 500ms OFF, blink after 500ms } void loop() { led1.loop(); // MUST call the led1.loop() function in loop() led2.loop(); // MUST call the led2.loop() function in loop() led3.loop(); // MUST call the led3.loop() function in loop() // DO SOMETHING HERE }

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 Arduino Uno R4 to the LEDs 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.
Click on the Libraries icon on the left side of the Arduino IDE.
Type "ezLED" in the search box and find the LED library created by Arduino UNO R4GetStarted.
Click the Install button to add the ezLED library.

Copy the provided code and paste it into the Arduino IDE.
To load the code onto an Arduino UNO R4 board, click the Upload button in the Arduino IDE.

How to upload Arduino UNO R4 code on Arduino IDE

See if the LED is on or off.

Arduino UNO R4 Code - Blink Multiple LEDs by using array

We can make the above code better by using an array of LEDs. The code below uses the array to manage LED objects.

/* * 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-blink-multiple-led */ #include <ezLED.h> // ezLED library by ArduinoGetStarted.com #define NUM_LED 3 // three LEDs #define PIN_LED_1 7 // The Arduino UNO R4 pin connected to LED 1 #define PIN_LED_2 8 // The Arduino UNO R4 pin connected to LED 2 #define PIN_LED_3 9 // The Arduino UNO R4 pin connected to LED 3 ezLED ledArray[NUM_LED] = { ezLED(PIN_LED_1), // create ezLED object that attach to pin PIN_LED_1 ezLED(PIN_LED_2), // create ezLED object that attach to pin PIN_LED_2 ezLED(PIN_LED_3) // create ezLED object that attach to pin PIN_LED_3 }; void setup() { Serial.begin(9600); ledArray[0].blink(800, 200); // 800ms ON, 200ms OFF, blink immediately ledArray[1].blink(500, 500); // 500ms ON, 500ms OFF, blink immediately ledArray[2].blink(500, 500, 500); // 500ms ON, 500ms OFF, blink after 500ms } void loop() { for (int i = 0; i < NUM_LED; i++) ledArray[i].loop(); // MUST call the led.loop() function in loop() // DO SOMETHING HERE }

Using the ezLED library, we can flexibly blink multiple LEDs like this:

Make several LEDs flash at different speeds.
Make several LEDs start flashing at different times.
Make each LED flash over a specific duration.
Make each LED flash a certain number of times.

Look at the sample code in the library.

Video Tutorial

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