Spark core Maverick ET73 probe

gistfile1.txt

#include "math.h"

#define PROBE1 A7
#define DEBUG TRUE
#define SMOOTH TRUE

// Measure actual board voltage, from 3v3* to GND with voltage multimeter, it's rarely exactly 3.3
const float VREF = 3.3200;

// What resistor did you use from 3v3* to between the analog pin and positive pin of thermistor?
// Measure it with multimeter
const int RESISTOR = 19800;

// ADC chip cycles is 4096 - 1
const int ADC = 4095;

// Global vars in case we want to set them on the fly
double A, B, C;


void setup() {
    // Start serial at 9600 baud
    Serial.begin(9600);
    
    // Forgot who
    A = -2.20911E-06;
    B = 7.02421E-04;
    C = 1.99476E-05;
    
    // 732 constants
    A = 2.3067434E-4;
    B = 2.3696596E-4;
    C = 1.2636414E-7;

    // Maverick ET-72/73 from heatermeter
    A = 2.4723753e-4;
    B = 2.3402251e-4;
    C = 1.3879768e-7; 
    
    // From smartbbq
    A = 0.00023067431;
    B = 0.00023696594;
    C = 1.2636415e-7;
    
    // Coefficient calculator at http://www.rusefi.com/Steinhart-Hart.html
    A = 4.97E-02;
    B = -8.38E-03;
    C = 3.87E-05;

}

void loop() {
    double bbqTemp;
    
    //Input = thermistor_temp(analogRead(PROBE1));
    bbqTemp = thermistor_temp(PROBE1);
    
    Serial.print("Temperature (C): ");
    Serial.println(bbqTemp, 2);

    delay(5000);
}

double thermistor_temp(int pin) { //Function to do theristor calculations

        int aval;
        double R, T;
        
        if(DEBUG) {
            Serial.println("============");
            Serial.println();
            Serial.print("aval (Pin ");
            Serial.print(pin);
            Serial.print("): ");
        }

        // read in smoothly
        //TODO change to 90% median
        
        if(SMOOTH) {
            int total = 0;
            
            for(int i=0; i<100; i++) {
                total += analogRead(pin);
                delay(1);
            }
            
            aval = total/100;
            if(DEBUG) {
                Serial.print(aval);
                Serial.println(" (smooth)");
            }
        } else {
            aval = analogRead(pin);
            if(DEBUG) {
                Serial.println(aval);
            }
        }
        delay(500);

        // What was the voltage that the pin saw? 
        // Calculate based on known ADC value and multimeter measured voltage from 3v3* to GND
        // float casting is required as aval divided by ADC may result in a fraction
        float Vout = (float) aval / (float) ADC * VREF;
        
        if(DEBUG) {
            Serial.print("/ ADC: ");
            Serial.println(ADC);
            Serial.print("* VREF ");
            Serial.println(VREF, 3);
            Serial.print("= Vout ");
            Serial.println(Vout, 3);
        }
        delay(500);
        
        // Calculate the original resistance
        R = (RESISTOR * VREF / Vout) - RESISTOR;
        if(DEBUG) {
            Serial.println("--");
            Serial.println("R = (RESISTOR * VREF / Vout) - RESISTOR");
            Serial.print("RESISTOR: ");
            Serial.println(RESISTOR);
            Serial.print("R: (new) ");
            Serial.println(R, 2);
        }
        delay(500);
        
        
        // calculate log10(R)
        R = log(R);
        // Show it
        if (DEBUG) {
            Serial.print("log(R): ");
            Serial.println(R);
        }
        delay(500);

        if (DEBUG) {
            Serial.println("--");
            Serial.print("A: ");
            Serial.println(A,14);
            Serial.print("B: ");
            Serial.println(B,14);
            Serial.print("C: ");
            Serial.println(C,14);
        }
        
        // Calculate temperature in Celsius
        T = (1 / (A + B * R + C * R * R * R)) - 273.15;
        
        // return degrees Celcius
    	return (T);
        
    }