Differential Temperature Controller Prototype Program http://www.youtube.com/watch?v=nsEZZS9QIao&feature=share&list=PLhtrCwA-6NNFC9vuZjVfwX6TNmPAWK0-e&index=1 http://www.youtube.com/watch?v=tPTX5_Q2qyE&feature=share&list=PLhtrCwA-6NNFC9vuZjVfwX6TNmPAWK0-e http://www.oomlout.com/oom.php/products/ardx/circ-10

DiffTemp1

 
This is code I modified for an lm34 that uses Fahrenheit instead of Celsius. Get the original code from oomlout with the link below.

/*     ---------------------------------------------------------
 *     |  Arduino Experimentation Kit Example Code             |
 *     |  CIRC-10 .: Temperature :. (TMP36 Temperature Sensor) |
 *     ---------------------------------------------------------
 *   
 *  A simple program to output the current temperature to the IDE's debug window 
 * 
 *  For more details on this circuit: http://www.oomlout.com/oom.php/products/ardx/circ-10  */

//TMP36 Pin Variables
int tempPin0 = 0; //the analog pin the TMP36's Vout (sense) pin is connected to
                        //the resolution is 10 mV / degree centigrade 
                        //(500 mV offset) to make negative temperatures an option
int tempPin1 = 1;

int led = 13;
/*
 * setup() - this function runs once when you turn your Arduino on
 * We initialize the serial connection with the computer
 */
void setup()
{
  Serial.begin(9600);  //Start the serial connection with the computer
                       //to view the result open the serial monitor 
                       //last button beneath the file bar (looks like a box with an antenae)
// initialize the digital pin as an output.
  pinMode(led, OUTPUT);
}
 
void loop()                     // run over and over again
{
 float temp0 = getVoltage(tempPin0);  //getting the voltage reading from the temperature sensor
 temp0 = temp0 * 100;                  //the lm34 is already scaled to Fahrenheit
                                              
  float temp1 = getVoltage(tempPin1);  //getting the voltage reading from the temperature sensor
 temp1 = temp1 * 100;                  //the lm34 is already scaled to Fahrenheit
                                                       
   Serial.print(temp0);                     //printing the result temp0
   // delay(1000);                               //waiting 1 second
   Serial.print(" - ");
   Serial.println(temp1);                     //printing the result temp1
   delay(1000);                               //waiting 1 second

  if (temp1-temp0>10)
  {
    digitalWrite(led, HIGH);   // turn the LED on (HIGH is the voltage level)
  }
  else
  {
    digitalWrite(led, LOW);    // turn the LED off by making the voltage LOW
  }

}

/*
 * getVoltage() - returns the voltage on the analog input defined by
 * pin
 */
float getVoltage(int pin){
 return (analogRead(pin) * .004882814); //converting from a 0 to 1023 digital range
                                        // to 0 to 5 volts (each 1 reading equals ~ 5 millivolts
}