Arduino Nano - Button - LED

This tutorial instructs you how to use the Arduino Nano and button to control the LED. We will learn two different applications:

Application 1 - The LED state is synchronized with the button state. In detail:

Application 2 - The LED state is toggled each time the button is pressed. More specifically:

In the Application 2, We need to debounce the button to make sure it works properly. We'll figure out why it's important by comparing how the LED behaves when we use the Arduino code with and without debouncing the button.

Hardware Preparation

1×Arduino Nano
1×USB A to Mini-B USB cable
1×Push Button
1×(Optional) Panel-mount Push Button
1×LED
1×220 ohm resistor
1×Breadboard
1×Jumper Wires
1×(Optional) 9V Power Adapter for Arduino Nano
1×(Recommended) Screw Terminal Adapter for Arduino Nano

Or you can buy the following sensor kit:

1×DIYables Sensor Kit 30 types, 69 units
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Overview of LED and Button

If you are unfamiliar with LED and button (including pinout, operation, and programming), the following tutorials can help:

Wiring Diagram

The wiring diagram between Arduino Nano and Button LED

This image is created using Fritzing. Click to enlarge image

Application 1 - The LED state is in sync with the button state

Arduino Nano Code

/* * This Arduino Nano code was developed by newbiely.com * * This Arduino Nano code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-nano/arduino-nano-button-led */ const int BUTTON_PIN = 2; // The number of the pushbutton pin const int LED_PIN = 5; // The number of the LED pin int button_state = 0; // variable for reading the pushbutton status void setup() { // Configure the LED pin as a digital output pinMode(LED_PIN, OUTPUT); // initialize the pushbutton pin as an pull-up input: // The pull-up input pin is HIGH when the button is open and LOW when pressed. pinMode(BUTTON_PIN, INPUT_PULLUP); } void loop() { // read the state of the pushbutton value: button_state = digitalRead(BUTTON_PIN); // control LED according to the state of button if(button_state == LOW) // If button is pressing digitalWrite(LED_PIN, HIGH); // turn on LED else // otherwise, button is not pressing digitalWrite(LED_PIN, LOW); // turn off LED }

Detailed Instructions

  • Connect an Arduino Nano to your computer with a USB cable.
  • Launch the Arduino IDE, and select the correct board and port.
  • Copy the code and open it in the Arduino IDE.
  • Click the Upload button on the Arduino IDE to compile and upload the code to the Arduino Nano.
Arduino IDE Upload Code
  • Press the button and hold it for a few seconds.
  • Check out the alteration in the LED's condition.

You will see that the LED state is in sync with the button state.

Code Explanation

Check out the line-by-line explanation contained in the comments of the source code!

Application 2 - Button toggles LED

Arduino Nano Code - Button Toggles LED Without Debouncing

/* * This Arduino Nano code was developed by newbiely.com * * This Arduino Nano code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-nano/arduino-nano-button-led */ const int BUTTON_PIN = 2; // The Arduino Nano pin connected to button's pin const int LED_PIN = 5; // The Arduino Nano pin connected to LED's pin int led_state = LOW; // The current state of LED int prev_button_state; // The previous state of button int button_state; // The current state of button void setup() { Serial.begin(9600); // Initialize the Serial to communicate with the Serial Monitor. pinMode(BUTTON_PIN, INPUT_PULLUP); // set arduino pin to input pull-up mode pinMode(LED_PIN, OUTPUT); // set arduino pin to output mode button_state = digitalRead(BUTTON_PIN); } void loop() { prev_button_state = button_state; // save the last state button_state = digitalRead(BUTTON_PIN); // read new state if(prev_button_state == HIGH && button_state == LOW) { Serial.println("The button is pressed"); // toggle state of LED led_state = !led_state; // control LED according to the toggled state digitalWrite(LED_PIN, led_state); } }

Code Explanation

You can locate the explanation in the comment lines of the Arduino Nano code above.

In the code, the expression led_state = !led_state is equal to the following code:

if(led_state == LOW) led_state = HIGH; else led_state = LOW;

Detailed Instructions

  • Copy the code and open it in the Arduino IDE.
  • Upload the code to the Arduino Nano.
  • Press release and button several times.
  • Check out the change in the LED's state.

You may observe that the LED state is toggled every time the button is pressed. However, this behavior may not always be consistent. At times, the LED state may be rapidly toggled multiple times within a single button press, or it may not toggle at all(toggling twice in quick succession which can be difficult to see with the naked eye).

⇒ To solve this problem, we need to debounce for the button.

Arduino Nano Code - Button Toggles LED With Debouncing

Debouncing a button can be challenging for beginners. Fortunately, the ezButton library makes it easy.

Why is debouncing necessary? See the Arduino Nano - Button Debounce tutorial for more information.

/* * This Arduino Nano code was developed by newbiely.com * * This Arduino Nano code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-nano/arduino-nano-button-led */ #include <ezButton.h> const int BUTTON_PIN = 2; // The number of the pushbutton pin const int LED_PIN = 5; // The number of the LED pin ezButton button(BUTTON_PIN); // create ezButton object for pin 7; int led_state = LOW; // The current state of LED void setup() { Serial.begin(9600); // Initialize the Serial to communicate with the Serial Monitor. pinMode(LED_PIN, OUTPUT); // set arduino pin to output mode button.setDebounceTime(50); // set debounce time to 50 milliseconds } void loop() { button.loop(); // MUST call the loop() function first if(button.isPressed()) { Serial.println("The button is pressed"); // toggle state of LED led_state = !led_state; // control LED according to the toggleed sate digitalWrite(LED_PIN, led_state); } }

Detailed Instructions

  • Install the ezButton library. Refer to How To for instructions.
  • Copy the code and open it with Arduino IDE.
  • Click the Upload button on Arduino IDE to upload the code to the Arduino Nano.
  • Press and release the button multiple times.
  • Check out the LED's state change.

You will see that the LED state is toggled exactly once each time the button is pressed.

Video Tutorial