It is an easy way to measure the exact temperature with a thermistor.

It is an easy way to measure the exact temperature with a thermistor.

About Project

Thermistor

The important segment in this circuit is Thermistor, which has been utilized to recognize the rise in temperature. The thermistor is temperature sensitive resistor, whose resistance modifies as per the temperature.

There are two different types of thermistor NTC and PTC, we have used as an NTC type thermistor. NTC thermistor is a resistor whose resistance diminishes as arise in temperature while in PTC it will improve the resistance as arise in temperature.

Thermistor.jpg

Vout= (Vin * Rt) / (R + Rt)

Rt value will be:

Rt = R (Vin/Vout) – 1

Here, Rt will be the resistance of the thermistor and the value of R is 10k ohm.

Calculation of Temperature from the Thermistor resistance

T = 1 / (A + Bln(Rt) + Cln (Rt)3 )

Where, A, B and C are the constants,

So, for estimating the temperature we require the value of thermistor resistance only.

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Thermistor with arduino temp output.jpg
        #include <math.h>
#include "LiquidCrystal.h"
LiquidCrystal lcd(44,46,40,52,50,48);
float A = 1.009249522e-03, B = 2.378405444e-04, C = 2.019202697e-07;
float T,logRt,Tf,Tc;
float Thermistor(int Vo) {
 logRt = log(10000.0*((1024.0/Vo-1))); 
 T = (1.0 / (A + B*logRt + C*logRt*logRt*logRt));  // We get the temperature value in Kelvin from this Stein-Hart equation
 Tc = T - 273.15;                     // Convert Kelvin to Celcius
 Tf = (Tc * 1.8) + 32.0;              // Convert Kelvin to Fahrenheit
 return T;
}

void setup(){
 lcd.begin(16,2);
 lcd.clear();
}

void loop() 
{
 lcd.setCursor(0,0);
  lcd.print("Temp:");
  lcd.print((Thermistor(analogRead(0))));
  lcd.print("k ");
 
 lcd.setCursor(0,1);
  lcd.print((Tc));
  lcd.print(" C ;");

 lcd.setCursor(9,1);
  lcd.print((Tf));
  lcd.print(" F");
 delay(800);
}
    
rasika Joshi
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