Arduino Nano - Button - Relay

This tutorial instructs you how to use the Arduino Nano and button to control the relay. By connecting the relay to a soleniod lock, light bulb, LED strip, motor, or actuator..., we can use a button to control the them. We will learn two different applications:

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

Application 2 - The relay 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 see why it's important by comparing how the relay 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×Relay
1×Breadboard
1×Jumper Wires
1×(Optional) Solenoid Lock
1×(Optional) 12V Power Adapter
1×(Optional) DC Power Jack
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 Relay and Button

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

Wiring Diagram

The wiring diagram between Arduino Nano and Button relay

This image is created using Fritzing. Click to enlarge image

Application 1 - The relay 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-relay */ const int BUTTON_PIN = 8; // The Arduino Nano pin connected to button's pin const int RELAY_PIN = 2; // The Arduino Nano pin connected to relay's pin 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(RELAY_PIN, OUTPUT); // set arduino pin to output mode } void loop() { int button_state = digitalRead(BUTTON_PIN); // read new state if (button_state == LOW) { Serial.println("The button is being pressed"); digitalWrite(RELAY_PIN, HIGH); // turn on } else if (button_state == HIGH) { Serial.println("The button is unpressed"); digitalWrite(RELAY_PIN, LOW); // turn off } }

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 change in the relay's condition.

You will see that the relay 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 Relay

Arduino Nano Code - Button Toggles relay 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-relay */ const int BUTTON_PIN = 8; // The Arduino Nano pin connected to button's pin const int RELAY_PIN = 2; // The Arduino Nano pin connected to relay's pin int relay_state = LOW; // The current state of relay 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(RELAY_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 relay relay_state = !relay_state; // control relay according to the toggled state digitalWrite(RELAY_PIN, relay_state); } }

Code Explanation

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

In the code, the expression relay_state = !relay_state is equivalent to the following code:

if(relay_state == LOW) relay_state = HIGH; else relay_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 relay's state.

You might notice that the relay switches on or off every time you press the button, but it may not always be the same. Sometimes it may rapidly switch multiple times with just one button press, or it might not switch at all (switch twice very quickly, which can't see with the naked eye).

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

Arduino Nano Code - Button Toggles relay 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-relay */ #include <ezButton.h> const int BUTTON_PIN = 8; // The Arduino Nano pin connected to button's pin const int RELAY_PIN = 2; // The Arduino Nano pin connected to relay's pin ezButton button(BUTTON_PIN); // create ezButton object for pin 7; int relay_state = LOW; // The current state of relay void setup() { Serial.begin(9600); // Initialize the Serial to communicate with the Serial Monitor. pinMode(RELAY_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 relay relay_state = !relay_state; // control relay according to the toggled state digitalWrite(RELAY_PIN, relay_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 relay's state change.

You'll notice that the relay will switch on or off only one time whenever you press the button.

Video Tutorial