Arduino Lesson #2

/*
  This code is a modification of the code found here: 
  https://create.arduino.cc/projecthub/Ayeon0122/reading-a-photoresistor-1e705e
 
  Read a photoresistor (light sensor) to detect "darkness" and turn on an LED when it
  is "dark" and turn back off again when it is "bright. Print analog read to serial monitor. 
 
  Code was modified to allow viewer to see the value read at the voltage divider. 
  The code was also modified to include an output format that is more easily exported as a .csv.
  AnalogRead values are sent to the serial monitor so values can be analyzed.
*/
 
 
// As usual, we'll create constants to name the pins we're using.
// This will make it easier to follow the code below.
 
const int sensorPin = 0;
const int ledPin = 3;
 
// We'll also set up some global variables for the light level a calibration value and
//and a raw light value
int lightCal;
int lightVal;
 
int readingNumber = 0; //sets the first reading value to zero, so all future values are time in seconds from start
 
void setup()
{
  // We'll set up the LED pin to be an output.
  pinMode(ledPin, OUTPUT);
  lightCal = analogRead(sensorPin);
  //we will take a single reading from the light sensor and store it in the lightCal
  //variable. This will give us a prelinary value to compare against in the loop
 
  Serial.begin(9600); //initializes serial port with baud rate of 9600, pretends the USB is an old school serial port
  //baud rate is a way of confirming that the send rate equals the receive rate
  Serial.println("Serial is initialized"); // verify that it does something, starts text on a new line after function
  Serial.print("Initial light reading: "); //verify the initial reading, appends to previous line, quotes are not values but actual words to be included
  Serial.println(lightCal); //adds the lightCal reading after the previous colon
  Serial.println("ReadingNumber , LightValue"); //Headers for the data that will be collected, CSV
  
}
 
 
void loop()
{
  //Take a reading using analogRead() on sensor pin and store it in lightVal
  lightVal = analogRead(sensorPin);
  Serial.print(readingNumber); //prints the reading number to the serial monitor
  Serial.print(" , "); //prints a comma in the serial monitor to aid in CSV data collection
  Serial.println(lightVal); //prints the current photoresistor values
  readingNumber++; //shorthand of saying new variable = previous variable +1
  delay(1000); //sets data collection sampling rate to 1 second, remember time is in thousandths of a second
 
  //if lightVal is less than our initial reading (lightCal) minus 50 it is dark and
  //turn pin 9 HIGH. The (-50) part of the statement sets the sensitivity. The smaller
  //the number the more sensitive the circuit will be to variances in light.You may need to adjust this value
  //depending on environmental conditions, the amount of light in your room initially. 
  if (lightVal < lightCal - 50)
  {
    digitalWrite(3, HIGH);
  }
 
  //else, it is bright, turn pin 3 LOW
  else
  {
    digitalWrite(3, LOW);
  }
 
}