ADC CALIBRATION - need help in making use of power (eg x^3)

Projects Programming
1

Dear all from several tests i managed to have a range of adc values, having different equations in order to achieve accurate results....

My code is this:

#include <LiquidCrystal.h>
//#include <math.h>
#define powf

LiquidCrystal lcd(12, 11, 10, 5, 4, 3, 2);
const int analogInPin = A0;
int count = 300;


double 	pow (double __x, double __y);

void setup()
{
  lcd.begin(16,2);                              //initialise LCD
  Serial.begin(9600);
  setupA();
}

void loop()
{
}


void setupA()
{
  lcd.print("TESTING");                //display on lcd
   delay(2000); 
   digitalWrite(13,LOW);                  //RELAY CLOSED 
   read_average_analog(250);
}


/* Sample analog in pin a given number of times and
 * return the floating point mean of the samples.
 * The summing of samples is done using a long, which
 * is subject to overflow for very large counts.
 */
double read_average_analog(int count)
{
  int i;
  long sum = 0;
  float average;
  float voltage;
  float conversiontogas;
  int gas;
  float calibration;


  
    sum = 0;
    for (i = 0; i < count; i++)
    {
        sum += analogRead(analogInPin);
        Serial.print(sum, 3);
        Serial.print("\n");
    }
      
   average = ((sum)/(count));
   int conv_average = average;
   //voltage = average*(0.00469592); 
   Serial.print("A");
   Serial.println(average, 3);
   //Serial.println(voltage, 3);
   
   //calibration = ((average)*(21.8115942) - (611.1594203));
   
   if((conv_average >= 380) && (conv_average <= 685) )
   {
          calibration = ((conv_average)*(21.438) - (583.2));
     
   }
   else if((conv_average <= 684) && (conv_average <= 900))
   {
     double test = pow(conv_average, 1.0308);

               //calibration = ((5783)*(double exp(double (conv_average)*(0.0013)))); 
     
   }
   
       //calibration = ((average)*(21.277) - (501.47));  IDEAL
   //conversiontogas = ((4621.2)*(voltage) - 607.96); 
  gas = conversiontogas;    
  Serial.println(calibration);
  //Serial.println(gas);
  
   
        
  
  return gas;
}

Since i dont have the library math.h i tried to define it and a function but of no use...

All i need is this

from range ADC12BIT - 381 - 684 ; y = 21.438x - 583.2 (SOLVED)
684 - 899; y = 16.841x^1.0308
899 - 1023; y = 5.484x^1.10161

I JUST NEED TO KNOW HOW TO USE POWER OF in code....
tnx

2

I JUST NEED TO KNOW HOW TO USE POWER OF in code....

http://arduino.cc/en/Reference/Pow

Can you keep it down? We aren't deaf.

3

Something like this ...

float f(x)
{
  if (x < 381) return -1;
  if (x < 684) return 21.438 * x - 583.2;
  if (x < 899) return 16.841 * pow(x, 1.0308);
  if (x < 1024) return 5.484 * pow(x, 1.10161);
  return -1;
}

Note that the function returns -1 for out of range values.

4

Yeps tnx....
i was using double and it didnt corectly work them out doh...sry
tnx

5

i was using double

On the Arduino, "double" and "float" are identical - both are 32 bit.

6

Then y did it not work them correctly?