// GND to GND, V to 5v, Out to A0

const int leds[] = {2,3,4,5,6};
unsigned int thresh[] = {0,0,0,0,0};
const int numLeds = sizeof(leds) / sizeof(int);

const int ledMin = 150;
int ledMax = 300;

void setup() {
  Serial.begin(57600);
  // turn LEDs on
  for (int i=0; i<numLeds; ++i)
  {
    pinMode(leds[i], OUTPUT);
    digitalWrite(leds[i], HIGH);
    delay(200);
  }
  // wait for a pull to calibrate (determine the max pull value)
  while (ledMax == 300)
  {
    unsigned int cur = analogRead(A0);
    if (cur > ledMax)
    {
      int calibrateStart = millis();
      while (millis() - calibrateStart < 2000)
      {
        cur = analogRead(A0);
        if (cur > ledMax)
          ledMax = cur;
      }
    }
  }
  unsigned int ledRange = ledMax - ledMin;
  // turn LEDs off to indicate that calibration is finished
  for (int i=0; i<numLeds; ++i)
  {
    thresh[i] = (ledRange / numLeds) * i + ledMin;
    digitalWrite(leds[i], LOW);
    Serial.print("Thresh ");
    Serial.print(i);
    Serial.print(": ");
    Serial.println(thresh[i]);
  }
  delay(1000);
}

void loop() {
  unsigned int cur = analogRead(A0);
  for (int i=0; i<numLeds; ++i)
  {
    if (cur > thresh[i])
      digitalWrite(leds[i], HIGH);
    else
      digitalWrite(leds[i], LOW);
  }
}