Arduino - Blink multiple LED

This tutorial teaches you how to program an Arduino to make multiple LEDs blink simultaneously without using the delay function. The tutorial provides code in two ways:

Arduino blink multiple LEDs
Arduino blink multiple LEDs using arrays.

We will use three LEDs as examples. You can easily modify it to adapt for two LEDs, four LEDs, or even more.

Hardware Required

1	×	Arduino UNO or Genuino UNO
1	×	USB 2.0 cable type A/B
1	×	LED
1	×	220 ohm resistor
1	×	Breadboard
1	×	Jumper Wires
1	×	(Optional) 9V Power Adapter for Arduino
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)

Please note: These are Amazon affiliate links. If you buy the components through these links, We will get a commission at no extra cost to you. We appreciate it.

About LED

We have a detailed LED tutorial including hardware pinout, working principle, Arduino wiring, and code instructions. Learn more here:

Arduino - LED tutorial

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

Arduino Code - Blink Multiple LEDs

To blink multiple LEDs simultaneously, we can't rely on the delay() function. This is because using delay() blocks other code execution, preventing us from blinking multiple LEDs at the same time. Instead, we utilize the millis() function to manage timestamps effectively.

For beginners, managing timestamps while blinking multiple LEDs can be challenging. Fortunately, the ezLED library simplifies this process by internally handling timestamp management. This removes the burden of managing timestamps from users when utilizing the library. Additionally, employing an array of LEDs can improve code clarity and conciseness.

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-blink-multiple-led */ #include <ezLED.h> // ezLED library by ArduinoGetStarted.com #define PIN_LED_1 7 // The Arduino pin connected to LED 1 #define PIN_LED_2 8 // The Arduino pin connected to LED 2 #define PIN_LED_3 9 // The Arduino 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(500, 500); // 500ms ON, 500ms OFF, blink immediately led2.blink(200, 800); // 200ms ON, 800ms OFF, blink immediately led3.blink(800, 200); // 800ms ON, 200ms OFF, blink immediately } 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 }

Quick Steps

Do the wiring as above image.
Connect the Arduino board to your PC via a USB cable
Open Arduino IDE on your PC.
Select the right Arduino board (e.g. Arduino Uno) and COM port.
Click to the Libraries icon on the left bar of the Arduino IDE.
Search “ezLED”, then find the led library by ArduinoGetStarted
Click Install button to install ezLED library.

Copy the above code and paste it to Arduino IDE.
Compile and upload code to Arduino board by clicking Upload button on Arduino IDE

How to upload Arduino code on Arduino IDE

Check out the status of LED

Arduino Code - Blink Multiple LEDs by using array

We can improve the code above by employing an array of LEDs. The following code utilizes this array to handle LED objects.

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-blink-multiple-led */ #include <ezLED.h> // ezLED library by ArduinoGetStarted.com #define NUM_LED 3 // three LEDs #define PIN_LED_1 7 // The Arduino pin connected to LED 1 #define PIN_LED_2 8 // The Arduino pin connected to LED 2 #define PIN_LED_3 9 // The Arduino 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(500, 500); // 500ms ON, 500ms OFF, blink immediately ledArray[1].blink(200, 800); // 200ms ON, 800ms OFF, blink immediately ledArray[2].blink(800, 200); // 800ms ON, 200ms OFF, blink immediately } void loop() { for (int i = 0; i < NUM_LED; i++) ledArray[i].loop(); // MUST call the led.loop() function in loop() // DO SOMETHING HERE }

By using the ezLED library, we can blink multiple LED flexiblly as follows:

Blink multiple LED with different freqency
Blink multiple LED with different start times
Blink each LED in a period of time
Blink each LED in number of times (cycle)

See the example code in the library.

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