Then how can i calibrate it i have no clue and I searched it up but didnt see anything about calibrating the thermistor
You need to make resistance measurements at two or more know temperatures. One of the temperatures need to be greater than 200.
So do you have a known temperature source greater than 200 degrees?
If not then do you have something that can make accurate temperature measurements above 200 degrees?
If you don't have either, then there is no way you can calibrate your thermister
Or you can buy a thermistor with a datasheet that provides the coefficients for the stienhart-hart equation or has a table that give the resistance, temperature data.
This is a very good tutorial on using thermisters
https://www.jameco.com/Jameco/workshop/TechTip/temperature-measurement-ntc-thermistors.html
Is heat gun on my soldering station will be enough?
150-250 will be enough?
Is that the maximum and minimum temperatures you want to measure?
Yes
Use this code to compute temperature.
Use this calculator to compute Beta
NTC Thermistors - Calculate Beta Values | Ametherm
You just need the measure the thermistor resistance at two temperatures and enter them into the calculator. Use the Beta from the calculator in the program
// How to compute beta:
// https://www.ametherm.com/thermistor/ntc-thermistor-beta
// How to:
// https://www.jameco.com/Jameco/workshop/TechTip/temperature-measurement-ntc-thermistors.html
// For stienhart-hart https://www.thinksrs.com/downloads/programs/Therm%20Calc/NTCCalibrator/NTCcalculator.htm
/*
Connect thermistor between Vref and the reference resistor.
Vref--Rt--Rref--GND, where Vref = 5V
Rt = R0 * ((Vref/Vout)-1)
OR
Connect thermistor between GND and the reference resistor.
Vref--Rref--Rt--GND, where Vref = 5V
Rt = R0 / ((Vref/Vout)-1) or Rt = Vout * (R0/(Vref-Vout))
*/
const int Vout_pin = A0; // ADC Pin to which the voltage divider is connected
const int R0 = 10000; // Nominal resistance at 25deg C
const int T0 = 25; // Temperature for nominal resistance (almost always 25deg C)
const int num_samples = 5;// Number of samples for average
const int beta = 3950; // The beta coefficient or the B value of the thermistor
// (usually 3000-4000) check the datasheet or use the computed value
const int Rref = 10000; // Value of reference resistor used for the voltage divider
const int Max_ADC = 1023; // Maximum ADC value (for 10 bit = 1023)
void setup()
{
Serial.begin(9600);
}
void loop()
{
int i;
float ADC_average;
int samples = 0;
float Rt;
// Read the thermistor voltage num_samples times
for (i = 0; i < num_samples; i++)
{
samples += analogRead(Vout_pin);
// for testing
//samples += 511;
delay(10);
}
ADC_average = samples / num_samples; // Average voltage
Serial.print("ADC readings ");
Serial.println(ADC_average, 0);
// Calculate thermistor resistance
// Rt = R0 * ((Vref/Vout)-1)
// If Vref is same volatge for the ADC then
// Vref/Vout = Max_ADC/ADC_average
Rt = Rref * ((Max_ADC / ADC_average) - 1.0);
Serial.print("Thermistor resistance ");
Serial.println(Rt, 1);
// Calculate temperature
float temperature;
temperature = log(Rt / R0); // ln(R/Ro)
temperature /= beta; // 1/B * ln(R/Ro)
temperature += 1.0 / (T0 + 273.15); // + (1/To)
temperature = 1.0 / temperature; // Invert
temperature -= 273.15; // Convert absolute temp to C
Serial.print("Temperature ");
Serial.print(temperature, 1);
Serial.println(" *C");
Serial.println("\n");
delay(1000);
}So i need just to put that code and add a relay part?
Yes and you should also change your ten 10K resistors to just one 10K resistor.
I donât understand why isnt it have to be the same resistance as thermistor?
You want the reference resistor value to be close to the thermister value when it is within the desired temperature range (150-200). That way the voltage going to the ADC is about halfway and you won't have problems measuring temperatures above and below the desired range.
If you use 100K then the ADC voltage will be around 2.5V at 25ÂșC but will be very small at 200ÂșC
Change that to 3705.7
Have you measured the resistance at room temperature?
No.
it shows -273 degree at 200
i cant find the name that stands for temp for relay
it shows nonsence now