Temperature Sensor Tutorial!

Step 5 Auto-calibrating supply-independent thermometer

This example is similar to the one above except that now we use a special trick where we read the analog value of a fixed reference voltage inside the chip and then use that to make a precise calculation. This also means it will work right no matter what voltage the Arduino is running at!

//TMP36 Pin Variables
int sensorPin = 0; //the analog pin the TMP36's Vout (sense) pin is connected to
//the resolution is 10 mV / degree centigrade with a
//500 mV offset to allow for negative temperatures

#define BANDGAPREF 14 // special indicator that we want to measure the bandgap

/* 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
delay(500);
}

void loop() // run over and over again
{
// get voltage reading from the secret internal 1.05V reference
int refReading = analogRead(BANDGAPREF);
Serial.println(refReading);

// now calculate our power supply voltage from the known 1.05 volt reading
float supplyvoltage = (1.05 * 1024) / refReading;
Serial.print(supplyvoltage); Serial.println("V power supply");

//getting the voltage reading from the temperature sensor
int reading = analogRead(sensorPin);

// converting that reading to voltage
float voltage = reading * supplyvoltage / 1024;

// print out the voltage
Serial.print(voltage); Serial.println(" volts");

// now print out the temperature
float temperatureC = (voltage - 0.5) * 100 ; //converting from 10 mv per degree wit 500 mV offset
//to degrees ((volatge - 500mV) times 100)
Serial.print(temperatureC); Serial.println(" degress C");

// now convert to Fahrenheight
float temperatureF = (temperatureC * 9 / 5) + 32;
Serial.print(temperatureF); Serial.println(" degress F");

delay(1000); //waiting a second
}

Comments

[mattadamsnet]

174
6.18V power supply
0.84 volts
33.88 degress C
92.98 degress F

173
6.22V power supply
0.84 volts
33.76 degress C
92.76 degress F

Heres the problem, .. its more like 70-72 degrees in here and im using USB power which my volt meter measures at 5.10v, the sensor @ the sensor is measuring .583v help me out here.