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:
If Arduino Nano detects that the button has been pressed (changing from a HIGH state to a LOW state), it will turn ON the relay if it's currently OFF, or turn OFF the relay if it's currently ON.
Releasing the button does not affect to the relay state.
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.
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If you are unfamiliar with relay and button (including pinout, operation, and programming), the following tutorials can help:
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const int BUTTON_PIN = 8;
const int RELAY_PIN = 2;
void setup() {
Serial.begin(9600);
pinMode(BUTTON_PIN, INPUT_PULLUP);
pinMode(RELAY_PIN, OUTPUT);
}
void loop() {
int button_state = digitalRead(BUTTON_PIN);
if (button_state == LOW) {
Serial.println("The button is being pressed");
digitalWrite(RELAY_PIN, HIGH);
}
else
if (button_state == HIGH) {
Serial.println("The button is unpressed");
digitalWrite(RELAY_PIN, LOW);
}
}
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.
You will see that the relay state is in sync with the button state.
Check out the line-by-line explanation contained in the comments of the source code!
const int BUTTON_PIN = 8;
const int RELAY_PIN = 2;
int relay_state = LOW;
int prev_button_state;
int button_state;
void setup() {
Serial.begin(9600);
pinMode(BUTTON_PIN, INPUT_PULLUP);
pinMode(RELAY_PIN, OUTPUT);
button_state = digitalRead(BUTTON_PIN);
}
void loop() {
prev_button_state = button_state;
button_state = digitalRead(BUTTON_PIN);
if(prev_button_state == HIGH && button_state == LOW) {
Serial.println("The button is pressed");
relay_state = !relay_state;
digitalWrite(RELAY_PIN, relay_state);
}
}
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;
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.
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.
#include <ezButton.h>
const int BUTTON_PIN = 8;
const int RELAY_PIN = 2;
ezButton button(BUTTON_PIN);
int relay_state = LOW;
void setup() {
Serial.begin(9600);
pinMode(RELAY_PIN, OUTPUT);
button.setDebounceTime(50);
}
void loop() {
button.loop();
if(button.isPressed()) {
Serial.println("The button is pressed");
relay_state = !relay_state;
digitalWrite(RELAY_PIN, relay_state);
}
}
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.
