I am using the attached NTC and connected it in series with a 10k resistor, supplying the series with 5V from Arduino.
I can't figure out what is going wrong.
The voltage at the ends of the NTC is sent to pin A5 of Arduino and I wrote the code to calculate the temperature.
(If I leave 33k measure 15°C)
NTC-2.pdf (165,8 KB)
sketch.ino (3,9 KB)
Please post your entire sketch, not a snippet.
Edit - please post your code in line, in a following message. Please do not edit your original post. Do not add code as an attachment again.
There is the sketch.ino file atatched
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As I was pasting the code here I realized that I had not initialized the NTC pin ... what a stupid mistake I made!
pinMode(readPin, ntc_pin);
Sorry for wasting your time, the important thing is to have solved and understood the error.
1 Like
Koepel
May 13, 2023, 12:17pm
8
It starts with the NTC.
Since you have a unknown NTC, you can not calculate the temperature, you can only make guesses.
I came across this document that shows how the formula is not ideal: https://catalogs.kyocera-avx.com/NTC-Thermistors.pdf
Please explain what that line of code is. Can you show your whole sketch ?
Don't assume you will get exactly 5v from there...........
DaveX
May 14, 2023, 12:26am
10
This does not look right. Your sketch has ntc_pin defined as A5 undefined, which is not INPUT, INPUT_PULLUP or OUTPUT .
By default, the pins are initialized to all be pinMode(xxx,INPUT)
Your sketch.ino:
//Librearie per il display LCD:
#include <Wire.h> //libreria per I2C
#include <LiquidCrystal_I2C.h> //libreria per LCD
LiquidCrystal_I2C lcd = LiquidCrystal_I2C(0x27, 20, 4);
//Pins su Arduino da usare:
#define ntc2_pin A5 // Pin che rileva la V del partitore di tensione del NTC2
#define Vg 8 // Pin che da in output la V
#define vdd 2 // 5V per il partitore di tensione
//Parametri dell'NTC2:
#define R0_NTC2 37000 //Resistenza nominale a 25⁰C .. cioè 33k
#define temperatura_nominale 25 //Temperatura nominale = 25⁰C
#define beta2 4220 //coefficiente beta del termistore
#define Rref 10000 //Valore del resistore utilizzato per i partitori di tensione
float campioni2 = 0; //array per memorizzare i campioni di tensione letti (generati da NTC2)
int readPin = A3;
float temperatura2 = 0; //a 25°C la resistenza è 10k per ntc1 e 33k per nct2
int ritardo = 500;
int i = 0; //per il ciclo for
float tensione2 = 0; //per il ciclo for
float Rntc2 = 0;
void setup() {
/*
SDA --> A4
SCL --> A5
GND --> GND
5V --> 5V
*/
//pinMode(4, OUTPUT); //SDA
//pinMode(5, OUTPUT); //SCL
lcd.init();
lcd.backlight();
lcd.clear();
pinMode(readPin, INPUT); //readPin = A3 = input A CHE MI SERVE A3 ????
pinMode(Vg, OUTPUT);
//pinMode(vdd,OUTPUT); //D2 = output (fornisce i 5V)
Serial.begin(9600);
}
void loop() {
//Prelevo 10 campioni e ne calcolo la media (per una miglior precisione):
//inizio lettura (e campionamento):
int numero_campioni = 20; //scegli tu quanto mettere
//digitalWrite(vdd,HIGH);
for (i = 0; i < numero_campioni ; i++) {
campioni2 = campioni2 + (float)analogRead(ntc2_pin);
delay(20); //ogni campione viene letto ogni 20ms
}
//digitalWrite(vdd,LOW);
//fine lettura
tensione2 = campioni2 / numero_campioni;
tensione2 = tensione2/1024.0*5;
campioni2=0;
//tensione = (float)analogRead(ntc1_pin);
//tensione = tensione/1024.0*5;
//V partitore:
/*Serial.print("V partitore = ");
Serial.println (tensione, 3);
Serial.println(" [V]");
lcd.setCursor(0, 0); //a sx le colonne .. a dx le righe
lcd.print("V partitore = ");
lcd.setCursor(14, 0);
lcd.print(tensione);
lcd.print(" V");*/
delay(50);
//resistenza dell'NTC2 (termistore)
Rntc2 = tensione2*Rref/(5*(1-tensione2/5));
Serial.print("Rntc2 = ");
Serial.println (Rntc2, 2);
Serial.println(" [ohm]");
lcd.setCursor(0, 2); //a sx le colonne .. a dx le righe
lcd.print("Rntc2 = ");
lcd.setCursor(8, 2);
lcd.print(Rntc2);
lcd.print(" ohm");
//temperatura media dell'NTC (termistore)
/*temperatura = media / resistenza_nominale;
temperatura = log(temperatura) / beta;
temperatura = 1.0 / (temperatura_nominale + 273.15);
temperatura = (1.0 / temperatura) - 273.15;
*/
temperatura2 = (1./296.15+log(Rntc2/R0_NTC2)/beta2);
temperatura2 = 1/temperatura2;
Serial.print("T2 = ");
Serial.print(temperatura2-273.15);
Serial.println(" °C");
lcd.setCursor(0, 3);
lcd.print("T2 = ");
lcd.setCursor(5, 3);
lcd.print(temperatura2-273.15);
lcd.print(" C");
////////////////////////////////////////////////////////// CONTROLLO //////////////////////////////////////////////////////////
/*
if (temperatura1-273.15 >= 40)
{
digitalWrite(Vg, LOW);
}
else if (temperatura1-273.15 < 40)
{
digitalWrite(Vg, HIGH);
}
else if(temperatura1-273.15 < 40 && temperatura1-273.15 > 37){
digitalWrite(Vg, HIGH);
}
*/
////////////////////////////////////////////////////////// CONTROLLO //////////////////////////////////////////////////////////
/*
tensione = ((5.)/1023.)*analogRead(readPin);
Serial.println(tensione); //stampo il valore di V letto
Serial.print("[V]"); //stampo la stringa "[V]" dopo il numero per chiarezza di lettura
delay(ritardo); //eventualmente un ritardo tra una lettura e un'altra
*/
}
system
November 10, 2023, 12:27am
11
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