Arduino LM335 temperature sensor interface

Forum 2005-2010 (read only) Hardware Interfacing
1

Here I describe a class for reading out the LM335 temperature sensor. This class is based on Chiptemp. See here for a detailed description of the software: Chip temperature measurement

LM335.pde

#include "LM335.h"
LM335::LM335(int _ADCpin)
{ ADCpin = _ADCpin;
}

inline void LM335::initialize() 
{ delay(10); // wait for the analog reference to stabilize
  readAdc(); // discard first sample (never hurts to be safe)  
}

inline int LM335::readAdc()
{ return analogRead(ADCpin);
}

int LM335::deciCelsius() 
{ long averageTemp=0; 
  initialize(); // must be done everytime
  for (int i=0; i<lm335_samples; i++) averageTemp += readAdc();
  averageTemp -= lm335_offsetFactor;
  return averageTemp / lm335_divideFactor; // return deci degree Celsius
}

int LM335::celsius() 
{ return deciCelsius()/10;
}

int LM335::deciFahrenheit() 
{ return (9 * deciCelsius()+1600) / 5;
}

int LM335::fahrenheit() 
{ return (9 * deciCelsius()+1600) / 50; // do not use deciFahrenheit()/10;
}

LM335.h

#ifndef LM335_H
#define LM335_H

// LM335 temperature sensor interface 
// Rev 1.0 Albert van Dalen www.avdweb.nl
// Resolution 0.1 degree

// Calibration values, set in decimals
static const float lm335_offset = 559; // change this!
static const float lm335_gain = 2.048;

static const int lm335_samples = 1000; // must be >= 1000, else the gain setting has no effect

// Compile time calculations
static const long lm335_offsetFactor = lm335_offset * lm335_samples;
static const int lm335_divideFactor = lm335_gain * lm335_samples/10; // deci = 1/10

class LM335 
{
public:
  LM335(int _ADCpin);
  int deciCelsius(); 
  int celsius(); 
  int deciFahrenheit();
  int fahrenheit(); 
  
private:   
  inline void initialize(); 
  inline int readAdc();
  int ADCpin;
};
2

Good work, thanks !