/*!

 * @file        Arduino_NTC_Interface.ino

 * @brief       Interfacing NTC Thermistor With Arduino

 * @author      Jobit Joseph

 * @copyright   Copyright (c) 2022 Semicon Media Pvt Ltd (https://circuitdigest.com)

 */

#define ntc_pin A0         // Pin,to which the voltage divider is connected

#define vd_power_pin 2        // 5V for the voltage divider

#define nominal_resistance 10000       //Nominal resistance at 25⁰C

#define nominal_temeprature 25   // temperature for nominal resistance (almost always 25⁰ C)

#define samplingrate 5    // Number of samples

#define beta 3950  // The beta coefficient or the B value of the thermistor (usually 3000-4000) check the datasheet for the accurate value.

#define Rref 10000   //Value of  resistor used for the voltage divider

int samples = 0;   //array to store the samples

void setup(void) {

  pinMode(vd_power_pin, OUTPUT);

  Serial.begin(9600);   //initialize serial communication at a baud rate of 9600

}

void loop(void) {

  uint8_t i;

  float average;

  samples = 0;

  // take voltage readings from the voltage divider

  digitalWrite(vd_power_pin, HIGH);

  for (i = 0; i < samplingrate; i++) {

    samples += analogRead(ntc_pin);

    delay(10);

  }

  digitalWrite(vd_power_pin, LOW);

  average = 0;

  average = samples / samplingrate;

  Serial.println("\n \n");

  Serial.print("ADC readings ");

  Serial.println(average);

  // Calculate NTC resistance

  average = 1023 / average - 1;

  average = Rref / average;

  Serial.print("Thermistor resistance ");

  Serial.println(average);

  float temperature;

  temperature = average / nominal_resistance;     // (R/Ro)

  temperature = log(temperature);                  // ln(R/Ro)

   Serial.print("Log Temp: ");

  Serial.println(temperature);

  temperature /= beta;                   // 1/B * ln(R/Ro)


  temperature += 1.0 / (nominal_temeprature + 273.15); // + (1/To)

  temperature = 1.0 / temperature;                 // Invert
  Serial.print("Beta Temp: ");

  Serial.println(temperature);
  temperature -= 273.15;                         // convert absolute temp to C

  Serial.print("Temperature ");

  Serial.print(temperature);

  Serial.println(" *C");

  delay(2000);

}