1.      INTRODUCTION

Buttons are components with two states open/close. There are two types of buttons:

·         NORMALLY OPEN

 

-Close circuit when you press it.

·         NORMALLY CLOSE

-Open circuit when you press it.

2.      HOW TO CONNECT?

Materials:

·         Arduino UNO board

·         Protoboard

·         Some wire Jumpers

·         220 and 10K ohms resistors

·         Button

·         LED

Normally, buttons in Arduino have similar internal connections.

To connect buttons, you must know that 1-2 and 3-4 pins are always connected.

On the other hand, 1 and 2 are disconnected from 3 and 4 until button is pressed.

To read the button state from Arduino, you must create a breakdown voltage in button connecting it between 5V and GND (see in the diagram) connect it to digital pin in Arduino A0… A5.

WARNING:

You need to connect a resistor between Arduino board and button to avoid short circuit.

EXERCISE_A (Turn on a LED) EXERCISE_B (Change between blink and fade)

3.      PROGRAMMING

EXERCISE_A (Turn on a LED)

-This program is a modification from CONNECTING_A_LED_A. In this case, the LED only turns on if the button is pressed. The button should be associated to a digital pin (pin 2) and set as INPUT.

int led=9;

int button=2;

void setup(){

  pinMode(led,OUTPUT);//Set led pin as output

  pinMode(button,INPUT);//Set button pin as input

}

-In loop part of the program button state is read by the function digitalRead(). It saves the result in ButtonStatevariable. Then, if() function write a HIGH level on LED if ButtonState equals HIGH and LOW level If not.

void loop(){

  int ButtonState=digitalRead(button);//Read button state

  //If Button state is in high level, led will turn on

  if(ButtonState==HIGH){

    digitalWrite(led,HIGH);

  }

  else{

    digitalWrite(led,LOW);

  }

}

 

EXERCISE_B (Change between blink and fade)

-This program combines CONNECTING_A_LED_A with CONNECTING_A_LED_B using button to change between both of them.

-Setup part is the same that in the previous exercise.

int led=9;//Assign the name led to pin 9

int i=0;

int button=2;

void setup(){

  pinMode(led,OUTPUT);//Set led pin output

  pinMode(button,INPUT);//Set button pin input

}

-Loop part is also similar but there, when ButtonState equals HIGH blink is executed. On the other hand, if ButtonStatenot equals HIGH fade is executed.

 

void loop(){

  int ButtonState=digitalRead(button);//Read button state

  //If Button state is in HIGH level led blinking, 

  //Unless led will be in fade mode.

  if(ButtonState==HIGH){

    digitalWrite(led,HIGH);//Write HIGH voltage level in led pin

    delay(500);//Stop program 500 miliseconds

    digitalWrite(led,LOW);//Write LOW voltage level in led pin

    delay(500);

  }

  else{

    //for increments i , one on one

    for(i=0;i<=255;i++){

      analogWrite(led,i);

      delay(5);

    }

    //for decrements i , one on one

    for(i=255;i>=0;i--){

      analogWrite(led,i);

      delay(5);

    }

  }

}