Using a push button control on an Arduino board to control an LED's brightness. Press the button to turn LED on. Hold it down to increase the LED's brightness until it reaches 100%. After reaching full brightness, the LED will return to 0% brightness and repeat.

arduino_pushbutton_led_brightness

// turn on LED when button is pressed, keep it on after release (simple de-bouncing)
// if button held, brightness changes

const int LED = 9;      // pin for LED
const int BUTTON = 7;   // pin of the pushbutton

int val = 0;            // stores state of input (pin 7)
int old_val = 0;        // stores previous value of val
int state = 0;          // state of LED (0 is off, 1 is on)

int brightness = 128;   // stores brightness of LED (start at 50%)
unsigned long startTime = 0;  // keep track of when the 'push' started

void setup() {
  pinMode(LED,OUTPUT);    // LED is an output
  pinMode(BUTTON,INPUT);  // BUTTON is an input
}

void loop() {
  val = digitalRead(BUTTON);  // read input value of button and store in val
  
  // check for transition
  if((val==HIGH) && (old_val==LOW)) {
    state = 1 - state;  // change on/off
    startTime = millis();  // the arduino clock - returns how many milliseconds have passed since board has been reset
    // used to remember when button was last pressed
    
    delay(10);
  }
  
  // check if button is held down
  if((val==HIGH) && (old_val==HIGH)) {
    // if button held for more than 500ms
    if(state==1 && (millis() - startTime) > 500) {
      brightness++;    // increase brightness by 1
      delay(10);       // use delay to stop brightness from going up too fast
      
      if(brightness > 255) {  // check for max brightness
        brightness = 0;       // reset to 0 if brightness is above 255
      }
    }
  }
  
  old_val = val;    // val is old, store it
  
  if(state==1) {
    analogWrite(LED,brightness);  // turn LED on at current brightness
  } else {
    analogWrite(LED,0);           // turn LED off
  }
}