LilyPad Temperature Sensor Hookup Guide

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Contributors: Gella
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Interpreting Sensor Readings

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.

Note: Upload the following code to your LilyPad Arduino, making sure to select the correct LilyPad board from the drop down menu below. Choose LilyPad Arduino USB if using a LilyPad Arduino USB. The LilyPad Arduino Simple, LilyPad Arduino, and LilyPad Development Board, and Development Board Simple all use a LilyPad ATmega 328. Select LilyPad USB Plus if following along with the LilyPad ProtoSnap Plus.

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

/*
LilyPad Temperature Sensor Example
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 -

Follow the tutorial at:
https://learn.sparkfun.com/tutorials/lilypad-temperature-sensor-hookup-guide

This code is released under the MIT License (http://opensource.org/licenses/MIT)
******************************************************************************/

// 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.
  rawTemp = analogRead(sensorPin);

  // 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.