Hallo, so I'm making a pulstruder using old parts from an CL-260 3D printer and i reached a stop. The same thermistor that gave me good readings till 300celsius on the printer, connected to the same boards gives me now some strange readings: when i heat up the thermistor the readings go down instead of up and the same happens when i cool it, i tried to fix the problem but i couldn't manage to do it. Ill be frank, i made most of my code using chatgpt, it is a good tool to understand basic ideas while also making things move and it worked great till now but i think the one i am using is not capable of writing the beta formula correctly and i have no idea how to do it.
If you know how to help me ill greatly appreciate it!
Here are some more INFO:
Thermistor type: NTC 10K-ohm Beta Value 3500
Here is the code i am using, it was mostly written poorly by chatgpt and then i had to try to fix it (it currently works fine except of the thermistor readings)
// Define pin connections & motor's steps per revolution
const int stepPin = 26;
const int dirPin = 28;
const int enablePin = 24;
const int heaterPin = 10;
const int coolerPin = 9;
const int blueLED = 4;
const int whiteLED = 5;
const int stepsPerRevolution = 200;
unsigned long stepDelay = 2000;
const int thermistorPin = 13; // Pin connected to the thermistor (analog pin)
// Constants for thermistor calculation
const float BETA = 3500.0; // Beta value for thermistor (adjust based on your thermistor)
const float R25 = 10000.0; // Resistance at 25°C in ohms (adjust based on your thermistor)
const int ADC_MAX = 1023; // Maximum ADC value for 10-bit ADC (0-1023)
const float VCC = 5.0; // Supply voltage for the Arduino (adjust if needed)
// Calibration value to adjust raw thermistor reading (experimentally determined)
const float CALIBRATION_OFFSET = 0;
float currentTemperature;
float desiredTemperature;
void setup() {
pinMode(stepPin, OUTPUT);
pinMode(dirPin, OUTPUT);
pinMode(enablePin, OUTPUT);
pinMode(heaterPin, OUTPUT);
pinMode(coolerPin, OUTPUT);
digitalWrite(enablePin, LOW); // Enable the stepper motor driver
Serial.begin(9600);
Serial.println("Enter desired temperature (in Celsius):");
}
void loop() {
if (Serial.available() > 0) {
String input = Serial.readStringUntil('\n');
input.trim();
desiredTemperature = input.toFloat();
Serial.print("Desired Temperature Set to: ");
Serial.println(desiredTemperature);
}
// Read the thermistor value from pin 13
int thermistorValue = analogRead(thermistorPin);
// Calculate the voltage across the thermistor (Vout)
float Vout = (thermistorValue / (float)ADC_MAX) * VCC;
// Calculate the thermistor resistance using the voltage divider formula
float resistance = (R25 * (VCC - Vout)) / Vout;
// Calculate temperature using the Beta equation
// Beta formula: 1/T = 1/T0 + (1/BETA) * ln(R/R0)
// where T is in Kelvin, T0 is 298.15K (25°C), R0 is resistance at 25°C (R25)
float temperatureK = 1.0 / (1.0 / 298.15 + (1.0 / BETA) * log(resistance / R25)); // In Kelvin
float temperature = temperatureK - 273.15; // Convert to Celsius
// Apply calibration offset (if necessary)
temperature += CALIBRATION_OFFSET;
// Print current temperature for debugging
Serial.print("Current Temperature: ");
Serial.print(temperature);
Serial.println(" °C");
// Heater control logic
if (temperature < desiredTemperature) {
digitalWrite(heaterPin, HIGH); // Keep heater on
digitalWrite(coolerPin, LOW); // Keep cooler off
Serial.println("Heater ON");
} else {
digitalWrite(heaterPin, LOW); // Turn off the heater
digitalWrite(coolerPin, HIGH); // Turn on the cooler
Serial.println("Heater OFF");
}
// Motor control
if (temperature == desiredTemperature) {
for (int i = 0; i < stepsPerRevolution; i++) {
digitalWrite(stepPin, HIGH);
delayMicroseconds(stepDelay);
digitalWrite(stepPin, LOW);
delayMicroseconds(stepDelay);
}
} else {
for (int i = 0; i < stepsPerRevolution; i++) {
digitalWrite(stepPin, LOW);
delayMicroseconds(stepDelay);
digitalWrite(stepPin, LOW);
delayMicroseconds(stepDelay);
}
}
// LED logic based on temperature comparison
if (temperature == desiredTemperature) {
digitalWrite(blueLED, HIGH);
} else {
digitalWrite(blueLED, LOW);
}
digitalWrite(whiteLED, HIGH);
}
