Arduino Blink LED With Pushbutton Control to Turn ON and Off

Abhishek Ghosh

By Abhishek Ghosh July 18, 2018 2:43 pm Updated on July 18, 2018

Arduino Blink LED With Pushbutton Control to Turn ON and Off

We already know that we can blink one LED with Arduino and also we can blink one LED with 555 IC. We can also blink 2 LEDs alternatively with Arduino and also blink 2 LEDs alternatively with 555 IC. From our older examples, we can start LED to be on with one pushbutton press and turn-off with another pushbutton keypress. Arduino Blink LED With Pushbutton Control to Turn ON and Off is Few Steps Higher Than Basic Example. There is Matter of Repeat Checking by Microcontroller. It is not exactly easy to a beginner but mandatory next step to learn.

Arduino Blink LED With Pushbutton Control to Turn ON and Off

Wiring/circuit diagram of this project is very easy. One digital pin of Arduino will be connected to LED, LED’s another leg will be connected to GND of Arduino. Alternatively, the onboard LED on Arduino board can be used. Connection for pushbutton is easy too – one digital pin of Arduino will be connected to pushbutton, pushbutton’s another leg will be connected to GND of Arduino with a resistor with value like 1K Ohm to ensure not much current going back to Arduino board.

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Very basic code will be :

const int kPinBtn = 2;
const int kPinLed = 13;

boolean kPress = false;

void setup()
{
  pinMode(kPinBtn, INPUT_PULLUP);
  pinMode(kPinLed, OUTPUT);
}

void loop()
{
  if(digitalRead(kPinBtn) == LOW && kPress == false)
  {
    digitalWrite(kPinLed, HIGH);
    kPress = true;
  }
  if(digitalRead(kPinBtn) == LOW && kPress == true)
  {
    digitalWrite(kPinLed, LOW);
    kPress = false;
  }  
}

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const int kPinBtn = 2;

const int kPinLed = 13;

boolean kPress = false;

void setup()

{

pinMode(kPinBtn, INPUT_PULLUP);

pinMode(kPinLed, OUTPUT);

}

void loop()

{

if(digitalRead(kPinBtn) == LOW && kPress == false)

{

digitalWrite(kPinLed, HIGH);

kPress = true;

}

if(digitalRead(kPinBtn) == LOW && kPress == true)

{

digitalWrite(kPinLed, LOW);

kPress = false;

}

You will notice the odd with a delay. If we want to achieve is to have a button alternate between blink and off smoothly, that can be done in this way:

enum { LED=13, ButtonPin=2, BounceMS=50, BlinkMS=256 };
unsigned long buttonAt;
bool blinky, bouncy, buttonState;

void setup() {
  pinMode(LED, OUTPUT);
  pinMode(ButtonPin, INPUT_PULLUP);
  blinky = bouncy = buttonState = false;
  buttonAt = millis();
}

void loop() {
  // Detect button changes
  if (bouncy) {
    if (millis() - buttonAt > BounceMS)
      bouncy = false;       // End of debounce period
  } else {
    if (digitalRead(ButtonPin) != buttonState) {
      buttonState = digitalRead(ButtonPin);
      buttonAt = millis();
      bouncy = true;        // Start debounce period
      if (buttonState) {    // Was button just pressed?
        blinky = !blinky;   // Toggle blink-state
      }
    }
  }
  // Control light-blinking
  if (blinky) {
    // Turn LED on for BlinkMS ms, then off for same 
    digitalWrite(LED, (millis() - buttonAt)%(2*BlinkMS) < BlinkMS);
  } else {
    digitalWrite(LED, LOW);
  }
}

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enum { LED=13, ButtonPin=2, BounceMS=50, BlinkMS=256 };

unsigned long buttonAt;

bool blinky, bouncy, buttonState;

void setup() {

pinMode(LED, OUTPUT);

pinMode(ButtonPin, INPUT_PULLUP);

blinky = bouncy = buttonState = false;

buttonAt = millis();

}

void loop() {

// Detect button changes

if (bouncy) {

if (millis() - buttonAt > BounceMS)

bouncy = false; // End of debounce period

} else {

if (digitalRead(ButtonPin) != buttonState) {

buttonState = digitalRead(ButtonPin);

buttonAt = millis();

bouncy = true; // Start debounce period

if (buttonState) { // Was button just pressed?

blinky = !blinky; // Toggle blink-state

}

// Control light-blinking

if (blinky) {

// Turn LED on for BlinkMS ms, then off for same

digitalWrite(LED, (millis() - buttonAt)%(2*BlinkMS) < BlinkMS);

} else {

digitalWrite(LED, LOW);

}

We can not directly use easy logic to start and stop. That will leads to a very long time between successive checks of the button as there is a delay between cycles! That invites some other functions to use, like using the millis function. Notice some changes in connection in this diagram :

Arduino Blink LED With Pushbutton Control

Another code with millis :

/* Pushbutton-controlled blinking LED
* David A. Mellis
* http://arduino.berlios.de
*/
int ledPin = 13;                // LED connected to digital pin 13
int ledValue = LOW;             // previous value of the LED
long ledStartTime = 0;          // will store last time LED was updated
long ledBlinkInterval = 1000;   // interval at which to blink (milliseconds)

int buttonPin = 2;              // an active-high momentary pushbutton on pin 2
int buttonValue = HIGH;         // the current state of the button
long buttonPressTime = 0;       // will store the time that the button was pressed


void setup()
{
 pinMode(ledPin, OUTPUT);      // sets the digital pin as output
}

void loop()
{
 // Check to see if the button is pressed.  If so, mark the time.  When the
 // button is released, calculate how long it was pressed, and make the led
 // blink at the same rate.
 buttonValue = digitalRead(buttonPin);

 // button press
 if (buttonValue==LOW && buttonPressTime==0) {
   buttonPressTime = millis();  // capture the time of the press
 }

 // button release
 if (buttonValue==HIGH && buttonPressTime!=0) {
   ledBlinkInterval = millis() - buttonPressTime;  // set the new flash interval
   buttonPressTime = 0;                            // clear the button press time
 }

 // check to see if it's time to blink the LED; that is, is the difference
 // between the current time and last time we blinked the LED bigger than
 // the interval at which we want to blink the LED.
 if (millis() - ledStartTime > ledBlinkInterval) {
   ledStartTime = millis();   // remember the last time we blinked the LED

   // if the LED is off turn it on and vice-versa.
   if (ledValue == LOW)
     ledValue = HIGH;
   else
     ledValue = LOW;

   digitalWrite(ledPin, ledValue);
 }
}

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/* Pushbutton-controlled blinking LED

* David A. Mellis

* http://arduino.berlios.de

*/

int ledPin = 13; // LED connected to digital pin 13

int ledValue = LOW; // previous value of the LED

long ledStartTime = 0; // will store last time LED was updated

long ledBlinkInterval = 1000; // interval at which to blink (milliseconds)

int buttonPin = 2; // an active-high momentary pushbutton on pin 2

int buttonValue = HIGH; // the current state of the button

long buttonPressTime = 0; // will store the time that the button was pressed

void setup()

{

pinMode(ledPin, OUTPUT); // sets the digital pin as output

}

void loop()

{

// Check to see if the button is pressed. If so, mark the time. When the

// button is released, calculate how long it was pressed, and make the led

// blink at the same rate.

buttonValue = digitalRead(buttonPin);

// button press

if (buttonValue==LOW && buttonPressTime==0) {

buttonPressTime = millis(); // capture the time of the press

}

// button release

if (buttonValue==HIGH && buttonPressTime!=0) {

ledBlinkInterval = millis() - buttonPressTime; // set the new flash interval

buttonPressTime = 0; // clear the button press time

}

// check to see if it's time to blink the LED; that is, is the difference

// between the current time and last time we blinked the LED bigger than

// the interval at which we want to blink the LED.

if (millis() - ledStartTime > ledBlinkInterval) {

ledStartTime = millis(); // remember the last time we blinked the LED

// if the LED is off turn it on and vice-versa.

if (ledValue == LOW)

ledValue = HIGH;

else

ledValue = LOW;

digitalWrite(ledPin, ledValue);

}

We can use timer library :

#include "Timer.h"

// Pin 13 has a LED connected on most Arduino boards.
// give it a name:
const int led = 13;
const int buttonPin = 2;

// declare state variables as global
bool buttonState = LOW;
bool buttonState_prev = LOW;
bool toggleBlinking;
bool blinkState;

// declare a Timer object so blinking can be done without loosing button presses
Timer timer_b;
int blink_id;

// the setup routine runs once when you press reset:
void setup() {
  // initialize the digital pin as an output.
  pinMode(led, OUTPUT);
  pinMode(buttonPin, INPUT_PULLUP);

  // initial state: toggle led each 1000 ms
  blink_id = timer_b.oscillate(led, 1000, HIGH);
  blinkState = true;
  toggleBlinking = false;
}

// the loop routine runs over and over again forever:
void loop() {
  // Update the timer (required)
  timer_b.update();

  // check if button has been pressed (HIGH to LOW),
  // then debounce it and raise toggle flag
  buttonState = digitalRead(buttonPin);
  if ((buttonState != buttonState_prev) && (buttonState_prev == HIGH)) {
    // simple button debounce (confirm press after some ms)
    delay (50);
    buttonState = digitalRead(buttonPin);
    if (buttonState != buttonState_prev) toggleBlinking = true;
  }

  // keep current LED state unless the button has been pushed
  switch (blinkState) {
    case true:
      // if button has been pushed, stop blinking and change LED state
      if (toggleBlinking == true) {
        timer_b.stop (blink_id);
        blinkState = false;
      }
      break;
    case false:
      digitalWrite(led, LOW);
      // if button has been pushed, start blinking and change LED state
      if (toggleBlinking == true) {
        blink_id = timer_b.oscillate(led, 1000, HIGH);
        blinkState = true;
      }
      break;
  }

  buttonState_prev = buttonState;
  toggleBlinking = false;
}

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#include "Timer.h"

// Pin 13 has a LED connected on most Arduino boards.

// give it a name:

const int led = 13;

const int buttonPin = 2;

// declare state variables as global

bool buttonState = LOW;

bool buttonState_prev = LOW;

bool toggleBlinking;

bool blinkState;

// declare a Timer object so blinking can be done without loosing button presses

Timer timer_b;

int blink_id;

// the setup routine runs once when you press reset:

void setup() {

// initialize the digital pin as an output.

pinMode(led, OUTPUT);

pinMode(buttonPin, INPUT_PULLUP);

// initial state: toggle led each 1000 ms

blink_id = timer_b.oscillate(led, 1000, HIGH);

blinkState = true;

toggleBlinking = false;

}

// the loop routine runs over and over again forever:

void loop() {

// Update the timer (required)

timer_b.update();

// check if button has been pressed (HIGH to LOW),

// then debounce it and raise toggle flag

buttonState = digitalRead(buttonPin);

if ((buttonState != buttonState_prev) && (buttonState_prev == HIGH)) {

// simple button debounce (confirm press after some ms)

delay (50);

buttonState = digitalRead(buttonPin);

if (buttonState != buttonState_prev) toggleBlinking = true;

}

// keep current LED state unless the button has been pushed

switch (blinkState) {

case true:

// if button has been pushed, stop blinking and change LED state

if (toggleBlinking == true) {

timer_b.stop (blink_id);

blinkState = false;

}

break;

case false:

digitalWrite(led, LOW);

// if button has been pushed, start blinking and change LED state

if (toggleBlinking == true) {

blink_id = timer_b.oscillate(led, 1000, HIGH);

blinkState = true;

}

break;

}

buttonState_prev = buttonState;

toggleBlinking = false;

}

This ends this tutorial.

Arduino Blink LED With Pushbutton Control to Turn ON and Off

Arduino Blink LED With Pushbutton Control to Turn ON and Off

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