Arduino - Button Toggle Relay

In a previous tutorial , We have learned how to turn on the relay if the button is pressed, and turn off relay if the button is released. In this tutorial, We are going to learn how to toggle relay each time button is pressed.

By connecting relay to light bulb, led strip, motor or actuator... We can use the button to toggle light bulb, led strip, motor or actuator...

The tutorial includes two main parts:

Hardware Required

1×Arduino UNO or Genuino UNO
1×USB 2.0 cable type A/B
1×Button
1×Relay
1×Warning Light Bright Waterproof
1×12V Power Adapter
1×Breadboard
n×Jumper Wires
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About Relay and Button

If you do not know about relay and button (pinout, how it works, how to program ...), learn about them in the following tutorials:

Wiring Diagram

Arduino Button Relay Wiring Diagram

Image is developed using Fritzing. Click to enlarge image

Arduino Code - Button Toggles Relay Without Debouncing

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-button-toggle-relay */ // constants won't change const int BUTTON_PIN = 7; // Arduino pin connected to button's pin const int RELAY_PIN = 3; // Arduino pin connected to relay's pin // variables will change: int relayState = LOW; // the current state of relay int lastButtonState; // the previous state of button int currentButtonState; // the current state of button void setup() { Serial.begin(9600); // initialize serial pinMode(BUTTON_PIN, INPUT_PULLUP); // set arduino pin to input pull-up mode pinMode(RELAY_PIN, OUTPUT); // set arduino pin to output mode currentButtonState = digitalRead(BUTTON_PIN); } void loop() { lastButtonState = currentButtonState; // save the last state currentButtonState = digitalRead(BUTTON_PIN); // read new state if(lastButtonState == HIGH && currentButtonState == LOW) { Serial.println("The button is pressed"); // toggle state of relay relayState = !relayState; // control relay arccoding to the toggled state digitalWrite(RELAY_PIN, relayState); } }

Quick Steps

  • Connect Arduino to PC via USB cable
  • Open Arduino IDE, select the right board and port
  • Copy the above code and open with Arduino IDE
  • Click Upload button on Arduino IDE to upload code to Arduino
  • Keep pressing the button several seconds and then release it.
  • See the change of relay's state

Code Explanation

Read the line-by-line explanation in comment lines of code!

In the code, relayState = !relayState is equivalent to the following code:

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

※ NOTE THAT:

In practice, the above code does not work correctly sometimes. To make it always work correctly, we need to debounce for the button . Debouncing for the button is not easy for beginners. Fortunately, thanks to the ezButton library , We can do it easily.

Arduino Code - Button Toggles Relay With Debouncing

Why do we need debouncing? ⇒ see Arduino - Button Debounce tutorial

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-button-toggle-relay */ #include <ezButton.h> // constants won't change const int BUTTON_PIN = 7; // Arduino pin connected to button's pin const int RELAY_PIN = 3; // Arduino pin connected to relay's pin ezButton button(BUTTON_PIN); // create ezButton object that attach to pin 7; // variables will change: int relayState = LOW; // the current state of relay void setup() { Serial.begin(9600); // initialize serial 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 relayState = !relayState; // control relay arccoding to the toggled state digitalWrite(RELAY_PIN, relayState); } }

Quick Steps

  • Install ezButton library. See How To
  • Copy the above code and open with Arduino IDE
  • Click Upload button on Arduino IDE to upload code to Arduino
  • Press button several times
  • See the change of relay's state

Button and Relay on Commercial Products

Most electronic products have a reset button. Additionally, the button also keeps other functionalities in many products.

  • Ring Video Doorbell with HD Video
  • Amazon Smart Speaker - Echo Dot
  • TP-Link AC1750 Smart WiFi Router - Dual Band Gigabit Wireless Internet Routers
  • Gaming Keyboard and Mouse
  • Wemo Smart Plug, WiFi Enabled, Works with Alexa, Google Assistant & Apple HomeKit

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