# LilyPad Temperature Sensor Hookup Guide

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The sensor produces an analog voltage representing the temperature near it. In order to get readings in degrees, we'll have to do some math. The voltage output from the sensor is linearly proportional to the Celsius temperature. Once you know the output voltage of the sensor, you can calculate the temperature with this equation:

To convert that reading to Fahrenheit, use this formula:

Next, we'll be use Serial Monitor to read the values coming from the sensor and insert the formulas in our code to display the temperature in both Celcius and Farenheit.

Don't forget to select the Serial Port that your LilyPad is connected to.

If prototyping with a LilyPad Development Board, change `sensorPin` to A1.
``````language:c

/*
SparkFun Electronics
https://www.sparkfun.com/products/8777

This code reads the input of the temperature sensor, converts it to Farenheit and Celsius
and prints to the Serial Monitor.

Temperature sensor connections:
* S tab to A3
* + tab to A5 (or +)
* - tab to -

******************************************************************************/

// Connect the S tab of the Temperature Sensor to A3
// If using the LilyPad ProtoSnap Plus, change to A9
int sensorPin = A3;

void setup()
{
// Set the temperature sensor pin as an INPUT:
pinMode(sensorPin, INPUT);

// Set pin A5 to use as a power pin for the light sensor
// If using the LilyPad Development Board or the + tab for power, comment out these lines of code
pinMode(A5, OUTPUT);
digitalWrite(A5, HIGH);

// Initialize Serial, set the baud rate to 9600 bps.
Serial.begin(9600);
}

void loop()
{
// Variable to store raw temperature
long rawTemp;

// Variable to store voltage calculation
float voltage;

// Variable to store Fahrenheit value
float fahrenheit;

// Variable to store Celsius value
float celsius;

// Read the raw 0-1023 value of temperature into a variable.

// Calculate the voltage, based on that value.
// Multiply by maximum voltage (3.3V) and divide by maximum ADC value (1023).
// If you plan on using this with a LilyPad Simple Arduino on USB power, change to 4.2
voltage = rawTemp * (3.3 / 1023.0);
Serial.print("Voltage: "); // Print voltage reading to serial monitor
Serial.println(voltage);

// Calculate the celsius temperature, based on that voltage..
celsius = (voltage - 0.5) * 100;
Serial.print("Celsius: "); // Print celcius temp to serial monitor
Serial.println(celsius);

// Use a common equation to convert celsius to Fahrenheit. F = C*9/5 + 32.
fahrenheit = (celsius * 9.0 / 5.0) + 32.0;
Serial.print("Fahrenheit: "); // Print Fahrenheit temp to serial monitor
Serial.println(fahrenheit);
// Print a blank line
Serial.println();

// Wait 1 second between readings
delay(1000);
}
``````

After uploading the code to your LilyPad Arduino, click the magnifying glass icon at the top right of your Arduino window to open the Serial Monitor window. You should begin seeing some values from the sensor. Try placing your finger over the sensor to see the readings change.