Arduino breathing light - with variable brightness and breathing rate.

breathing_night_light.ino

/*
  Arduino breathing light - with variable brightness and breathing rate. 
*/

#include <math.h>

const int PIN_POT = 0;
const int PIN_LED = 13;

const int BRIGHTNESS_MIN = 0;
const int BRIGHTNESS_MAX = 255;
const float DURATION_FACTOR_MIN = 0.5;
const float DURATION_FACTOR_MAX = 2.0;

void setup() {
  Serial.begin(9600);

  pinMode(PIN_POT, INPUT);
  pinMode(PIN_LED, OUTPUT);
}

int pot_value;
void loop() {
  pot_value = analogRead(PIN_POT);
  float brightness = map(pot_value, 0, 1023, BRIGHTNESS_MIN, BRIGHTNESS_MAX);
  float biased_duration_factor = map(pot_value, 0, 1023, DURATION_FACTOR_MIN, DURATION_FACTOR_MAX);
  float brightnessFunction = (exp(sin(millis() / 4000.0 * PI * biased_duration_factor)) - 0.36787944) * 108.0;
  brightness = map(brightnessFunction, BRIGHTNESS_MIN, BRIGHTNESS_MAX, 0, brightness);
  analogWrite(11, brightness);
}