intervalometer.pde

/*
  intervalometer.pde
  Flashes an LED for random-length intervals at random intervals
  The first 'on' interval is set by MINON and MAXON, the 'off' interval
  by MINOFF and MAXOFF (in seconds.)
 */

#define LED 0
#define FLICKER 100     // 1/10 second.
#define FLASHES 5       // flashes per second.
#define MINON 10        // minimum flash duration
#define MAXON 60        // maximum flash duration
#define MINOFF 30       // minimum off duration
#define MAXOFF 240      // maximum off duration

long time;              // used for counting milliseconds and flashes.
int j;                  // loop counter

void flash() {
    digitalWrite(LED, HIGH);
    delay(FLICKER);
    digitalWrite(LED, LOW);
    delay(FLICKER);
}

void setup() {                
    // initialize the digital pin as an output.
    pinMode(LED, OUTPUT);     
	// use unconnected input as a random seed
    randomSeed(analogRead(1));		
    // Indicate operation by flashing 5x.
    delay(1000);
    for (byte j=0;j<FLASHES;j++) flash();
}

void loop() {
    time = random(MINOFF, MAXOFF);  // random OFF delay, seconds
    for (j=0;j<time;j++) 
        delay(1000);
    // now flash for a random time
    time = random(MINON*FLASHES, MAXON*FLASHES);// random on delay, flashes
    for (j=0;j<time;j++) 
        flash();
}