/**********************************************
This code defines values for a thermistor's resistance,
reference resistance, B-coefficient, and a known temperature
in Celsius. It then reads an analog value from a sensor
(presumably connected to a thermistor) and calculates the temperature
 in Celsius using the Steinhart-Hart equation. 
 The temperature is displayed on an LCD2004 I2C display 
 and printed to the serial monitor with a delay, 
 allowing you to monitor temperature readings. This code is 
 suitable for interfacing with a thermistor to measure and
  display temperature in Celsius.
custonchip created by arvind patil 14/10/23
******************************************/

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 20, 4); // Address 0x27 for a 20x4 LCD display

// Define the thermistor resistance and reference resistance values
const float thermistorResistance = 10000.0;  // Resistance of the thermistor (in ohms)
const float referenceResistance = 10000.0;   // Reference resistance (in ohms) at a known temperature

// Define the B-coefficient for the thermistor
const float betaCoefficient = 3950.0;  // Beta coefficient of the thermistor

// Define the temperature at a known resistance (usually room temperature)
const float knownTemperatureCelsius = 25.0;  // Known temperature in Celsius

void setup() {
  Serial.begin(115200);
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Temperature:");
  lcd.setCursor(0, 1);
  lcd.print("Celsius:");
  lcd.setCursor(0,2 );
  lcd.print("customchip ky-13");
  lcd.setCursor(0,3);
  lcd.print("by arvind 14/10/23");
 
  pinMode(A2, INPUT);
}

void loop() {
  // Read the analog value from the sensor
  int analogValue = analogRead(A2);

  // Calculate the resistance of the thermistor
  float resistance = referenceResistance / (1023.0 / analogValue - 1.0);

  // Calculate the temperature in Celsius using the Steinhart-Hart equation
  float steinhart = resistance / thermistorResistance;  // (R/Ro)
  steinhart = log(steinhart);  // ln(R/Ro)
  steinhart /= betaCoefficient;  // 1/B * ln(R/Ro)
  steinhart += 1.0 / (knownTemperatureCelsius + 273.15);  // + (1/To)
  steinhart = 1.0 / steinhart;  // Invert
  float temperatureCelsius = steinhart - 273.15;

  // Print the temperature in Celsius to the LCD display
  lcd.setCursor(11, 1);
  lcd.print("     "); // Clear previous temperature
  lcd.setCursor(11, 1);
  lcd.print(temperatureCelsius);

  // Print the temperature in Celsius to the serial monitor
  Serial.print("Temperature (Celsius): ");
  Serial.println(temperatureCelsius);

  delay(5000);  // You can adjust the delay as needed
}