Flickering LEDs - proof of concept

My first project is to light a string of papier-mâché hot air balloons. I was just going to light them with some LEDs, but then I heard about the Arduino and wanted to make something more exciting. I got a starter kit from adafruit.com and got to work.

This is the first proof of concept of making the LEDs flicker. Later I’ll add a light sensor to start a sleep timer that will turn the balloons off after a half hour.



Here’s the sketch that runs what you see above:

/*
* randomly flickering LEDs
*/

int ledPin[] = {
5, 6, 9, 10, 11};              // pwm pins only
int ledState[5];                 // last state of each led
long randNumber;

void setup() {
for (int i=0; i<5; i++){       // set each led pin as an output
  pinMode(ledPin[i], OUTPUT);   
}
randomSeed(analogRead(0));     // seed the rnd generator with noise from unused pin

for (int i=0; i<5; i++){       // init each led with a random value
  ledState[i] = random(20, 201);
}
}

void loop(){
for (int i=0; i<5; i++){                   // for each led:
  analogWrite(ledPin[i], ledState[i]);     // set the pwm value of that pin determined previously
  randNumber = random(-35, 41);            // generate new random number and add that to the current value
  ledState[i] += randNumber;               // that range can be tweaked to change the intensity of the flickering
  if (ledState[i] > 200) {                 // now clamp the limits of the pwm values so it remains within
    ledState[i] = 200;                     // a pleasing range as well as the pwm range
  }
  if (ledState[i] < 10) {
    ledState[i] = 10;
  }
}
delay(100);    // the delay between changes
}