#include <toneAC.h>

const int piezo=9;
const int ledPin= 13;
const int photoPin= A0;
int readVal;
int minSense= 1000;
int maxSense= 0;
unsigned long myTime;

void setup() {
  // put your setup code here, to run once:
pinMode (piezo, OUTPUT);
pinMode (photoPin, INPUT);
Serial.begin (9600);
calibrate ();
}
void calibrate()
{
  digitalWrite (ledPin, HIGH);
  delay (30);
  digitalWrite (ledPin, LOW);
  myTime= millis();
  while( millis () - myTime < 5000)
  {
  readVal= analogRead (photoPin);
  if (readVal > maxSense)
 {
  maxSense= readVal;
 }
    if (readVal< minSense)

  {
    minSense= readVal;
  }
  }
 Serial. print(" Max Value  ");
 Serial. print (maxSense);
 Serial. print ("  Min Value = ");
Serial. println (minSense);
}


void loop() {
  // put your main code here, to run repeatedly:

int readVal= analogRead (photoPin);
readVal= map (readVal, minSense, maxSense, 40, 4000);
readVal= constrain (readVal, 40, 4000);
tone (piezo, readVal, 20);
delay (10);
noTone (piezo);

}