Arduino Starter Series - The Love-O-Meter

Arduino Aug 18, 2015

This is a project from my Arduino starter series.

In this project I'm going to make a Love-O-Meter, another project from the Arduino Projects Book. Perhaps this should have been made on Valentines day. Anyways, its simple

My code differs slightly from the Arduino Projects Book version, however the result is the same.

This project is ideal for beginners who want to grasp the basics of Arduino programming and prototyping. Enjoy!

Project Requirements

Arduino Uno/Duemilanove/Diecimila
USB cable to program Arduino
Three LEDS (Two red and one green)
Three 220 Ohm Resistors
One Temperature sensor (I'm using the TMP36)
Wires to power the components on the breadboard

The Breadboard Setup

The Love-O-Meter Arduino Sketch

Arduino Sketch

As usual, I've commented the code as mush as possible to explain every line.

// Temperature settings
int temperaturePin = A0; // We connect the temperature sensor to Analog 0
float ambientTemperature = 25.68; // This is the temperature value for the environment. This needs to be defined by the user
int lowTemp = 1;
int midTemp = 2;
int highTemp = 3;

// LED pins are defined here in accordance with the breadboard setup
int LED1 = 11;
int LED2 = 12;
int LED3 = 13;

void setup() {
  Serial.begin(9600); // We need to listen to the Arduino using the Serial monitor to see measurements from the temperature sensor

  // LED setup
  pinMode(LED1, OUTPUT);
  digitalWrite(LED1, LOW);
  pinMode(LED2, OUTPUT);
  digitalWrite(LED2, LOW);
  pinMode(LED3, OUTPUT);
  digitalWrite(LED3, LOW);

* I've left the loop functionality here the same as whats provided in the Arduino Starter Kit, 
* the only thing to note here that might differ for other users is that the temperature sensor 
* I'm using as a 500 mV offset and that needs to be accounted for in the equation
void loop() {
   // read the value on the temperature AnalogIn pin
  // and store it in a variable
  int sensorVal = analogRead(temperaturePin);

  // send the 10-bit sensor value out the serial port
  Serial.print("sensor Value: ");

  // convert the ADC reading to voltage
  float voltage = (sensorVal / 1024.0) * 5.0;

  // Send the voltage level out the Serial port
  Serial.print(", Volts: ");

  // convert the voltage to temperature in degrees C
  // the sensor changes 10 mV per degree
  // the datasheet says there's a 500 mV offset
  // ((voltage - 500mV) times 100)
  Serial.print(", degrees C: ");
  float temperature = (voltage - .5) * 100;

  // if the current temperature is lower than the ambient temperature
  // turn off all LEDs
  if (temperature < ambientTemperature + lowTemp) {
    digitalWrite(LED1, LOW);
    digitalWrite(LED2, LOW);
    digitalWrite(LED3, LOW);
  } // if the temperature rises between low and mid temp, turn an LED on
  else if (temperature >= ambientTemperature + lowTemp && temperature < ambientTemperature + midTemp) {
    digitalWrite(LED1, HIGH);
    digitalWrite(LED2, LOW);
    digitalWrite(LED3, LOW);
  } // if the temperature rises mid and high temp, turn a second LED on
  else if (temperature >= ambientTemperature + midTemp && temperature < ambientTemperature + highTemp) {
    digitalWrite(LED1, HIGH);
    digitalWrite(LED2, HIGH);
    digitalWrite(LED3, LOW);
  } // if the temperature rises more than high temp, turn all LEDs on
  else if (temperature >= ambientTemperature + highTemp) {
    digitalWrite(LED1, HIGH);
    digitalWrite(LED2, HIGH);
    digitalWrite(LED3, HIGH);

View this project on my Github page

Nicholas Bester

I have 15 years of experience in design, development and implementation of digital marketing solutions ranging from virtual reality, 3D projection mapping, mobile apps and massive web platforms.