Meat-Smoker-Controller/temperature_sensor.cpp

#include "temperature_sensor.h"

TemperatureSensor::TemperatureSensor(byte pin, int refResistance, double a, double b, double c) {
  this->pin = pin;
  this->refResistance = refResistance;
  this->a = a;
  this->b = b;
  this->c = c;
  init();
}

#define DEBUG_OUTPUT Serial

void TemperatureSensor::init() {
  pinMode(pin, INPUT);
}

void TemperatureSensor::preload() {
  for(int i=0; i< 10; i++){
    update();
  }
}

void TemperatureSensor::update() {
  if(measurementCounter < 10){ //Measure 10 times before calculating temperature from average
    measurementAccumulative += analogRead(pin);
    measurementCounter++;
  } else {
    int sensorValue = measurementAccumulative/measurementCounter;
    // voltage = sensorValue*5.0/1024.0
    // r1 = (vdd-vout)*r2/vout
    double resistance = ((1.0-sensorValue/1024.0)*refResistance/(sensorValue/1024.0)); // this is our probe resistance.
    double lt = log(resistance);
    temperature = (1 / (a+b*lt+c*lt*lt*lt)) - 273.15; //Calculate temperature in Kelvin according to Steinhart-Hart equation, then convert to Celcius
    if(temperature < -35) temperature = sqrt (-1); // If value is unpossibly low, return NaN
    measurementAccumulative = 0;
    measurementCounter = 0;
  }
}

float TemperatureSensor::getTemperature() {
    return temperature;
}