LilyPad Temperature Sensor Hookup Guide
Contributors:
Gella
Using Values to Trigger Behaviors
Next, we'll use some of the readings we gathered to trigger an action or behavior when the temperature is above or below a set threshold.
This example uses the built-in LED attached to pin 13 on the LilyPad Arduino.
/* LilyPad Temperature Trigger Example SparkFun Electronics https://www.sparkfun.com/products/8777 This code reads the input of the temperature sensor and compares it to a set variable named 'threshold'. If temperature is above the thermalAlert threshold, the built-in LED on the LilyPad Arduino will turn on. If the temperature falls below the threshold, the LED will turn off. 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 example is based on Thermal Alert! example in the Digital Sandbox: https://learn.sparkfun.com/tutorials/digital-sandbox-arduino-companion/12-thermal-alert 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; int alertLED = 13; // Set temperature threshold variable to check against. If the temperature reading is above // this number in degrees Fahrenheit, the LED will turn on int threshold = 80; // 80 degrees Fahrenheit 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); // Make the built-in LED an OUTPUT pinMode(alertLED, OUTPUT); // 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(); // Check the temperature, and turn on the LEDs associated with the hot or cold thresholds if (fahrenheit >= threshold) // If the temperature rises above the threshold: { digitalWrite(alertLED, HIGH); // Turn the LED on Serial.println("Thermal alert!"); } else { digitalWrite(alertLED, LOW); //Turn the LED off } // Wait 1 second between readings delay(1000); }
In this code, we use an if()
statement to compare the value of threshold
to the converted analog readings from the temperature sensor stored in the fahrenheit
variable. If the temperature is too hot (higher than the threshold's set value), then the LED will turn on. If the value is lower than the threshold, the LED will turn off.
If are having trouble getting temperatures that trigger the LED, check the output of the Serial Monitor to see if there's a better value for threshold
than what is set in the example code.