Arduino LED Temperature Indicator

Above is a simuation.  Click the "Start Simulation" button to begin.  Click on the sensor labled "TMP" to change its value: the LEDs will light themselves according to the sensor's reading.

This design is made to keep track of the temperature in a room.

You give it the parameters you want and it will light a blue LED if it is too cold, a red LED if it's too hot, and a green one if it's just right.

You will need:

• Arduino board: https://amzn.to/2DLjxR2
• Breadboard: https://amzn.to/2RYqiSK
• Jumper wires: https://amzn.to/2Q7kiKc
• 3 220Ω resistors (red-red-brown): https://amzn.to/2S2sV5R
• 3 LEDs (colors of your choice): https://amzn.to/2S5PFlM
• A temperature sensor (mine is an LM35, but most should work): https://amzn.to/2ORLHuQ

Step 1: Make the Circuit

• Red LED goes to digital pin 4 through one of the resistors, and ground
• Green LED goes to digital pin 3 though a resistor, and ground
• Blue LED goes to digital pin 2 through a resistor, and ground
• Pin one (the pin on the left) of the temperature sensor goes to 5v
• Pin two (the pin in the middle) of the temperature sensor goes to analog pin A2
• pin three (the pin on the right) of the temperature sensor goes to ground

Step 2: Code

Connect your Arduino to your computer and upload this code:

const int hot = 87; //set hot parameter
const int cold = 75; //set cold parameter
void setup() {
  pinMode(A2, INPUT); //sensor
  pinMode(2, OUTPUT); //blue
  pinMode(3, OUTPUT); //green
  pinMode(4, OUTPUT); //red
  Serial.begin(9600);
}
void loop() {
  int sensor = analogRead(A2);
  float voltage = (sensor / 1024.0) * 5.0;
  float tempC = (voltage - .5) * 100;
  float tempF = (tempC * 1.8) + 32;
  Serial.print("temp: ");
  Serial.print(tempF);
  if (tempF < cold) { //cold
    digitalWrite(2, HIGH);
    digitalWrite(3, LOW);
    digitalWrite(4, LOW);
    Serial.println(" It's Cold.");
  }
  else if (tempF >= hot) { //hot
    digitalWrite(2, LOW);
    digitalWrite(3, LOW);
    digitalWrite(4, HIGH);
    Serial.println(" It's Hot.");
  }
  else { //fine
    digitalWrite(2, LOW);
    digitalWrite(3, HIGH);
    digitalWrite(4, LOW);
    Serial.println(" It's Fine.");
  }
  delay(10);
}