anatemp.ino

// which analog pin to connect
#define THERMISTORPIN A0         
// resistance at 25 degrees C
#define THERMISTORNOMINAL 10000      
// temp. for nominal resistance (almost always 25 C)
#define TEMPERATURENOMINAL 25   
// how many samples to take and average, more takes longer
// but is more 'smooth'
#define NUMSAMPLES 5
// The beta coefficient of the thermistor (usually 3000-4000)
#define BCOEFFICIENT 3950
// the value of the 'other' resistor
#define SERIESRESISTOR 10000    
 
int samples[NUMSAMPLES];
float min, max;
 
void setup(void) {
  Serial.begin(9600);
  analogReference(EXTERNAL);
  min = 999;
  max = -999;
}
 
void loop(void) {
  uint8_t i;
  float average;
  float temp;
 
  // take N samples in a row, with a slight delay
  for (i=0; i< NUMSAMPLES; i++) {
   samples[i] = analogRead(THERMISTORPIN);
   delay(10);
  }
 
  // average all the samples out
  average = 0;
  for (i=0; i< NUMSAMPLES; i++) {
     average += samples[i];
  }
  average /= NUMSAMPLES;
 
//  Serial.print("Average analog reading "); 
//  Serial.println(average);
 
  // convert the value to resistance
  average = 1023 / average - 1;
  average = SERIESRESISTOR / average;
//  Serial.print("Thermistor resistance "); 
//  Serial.println(average);
 
  float steinhart;
  steinhart = average / THERMISTORNOMINAL;     // (R/Ro)
  steinhart = log(steinhart);                  // ln(R/Ro)
  steinhart /= BCOEFFICIENT;                   // 1/B * ln(R/Ro)
  steinhart += 1.0 / (TEMPERATURENOMINAL + 273.15); // + (1/To)
  steinhart = 1.0 / steinhart;                 // Invert
  steinhart -= 273.15;                         // convert to C

  temp = steinhart;

  if (temp < min) {
    min = temp;
  }
  if (temp > max) {
    max = temp;  
  }
 
  Serial.print("current: "); 
  Serial.print(temp);
  Serial.print(" max: ");
  Serial.print(max);
  Serial.print(" min: ");
  Serial.print(min);
  Serial.println("");
 
  delay(1000);
}