Arduino : Intermediate - Control LED using LM 35 or TMP 36

Description

Reads repeatedly from an analog input (LM 35), and convert the ADC reading to voltage and temperature in Celcius, print the result to the serial monitor.

List Item

1. Arduino Uno 
2. 3 LED
3. 3 Resistor (150 to 330 ohm)
4. LM 35 or TMP 36
5. Wire jumper

Wiring Diagram

Video

Coding
/*
  Arduino Starter Kit example
 Project 3  - Love-O-Meter

 This sketch is written to accompany Project 3 in the
 Arduino Starter Kit

 Parts required:
 1 TMP36 temperature sensor
 3 red LEDs
 3 220 ohm resistors

 Created 13 September 2012
 by Scott Fitzgerald

 http://www.arduino.cc/starterKit

 This example code is part of the public domain
 */

// named constant for the pin the sensor is connected to
const int sensorPin = A0;
// room temperature in Celcius
const float baselineTemp = 20.0;

void setup() {
  // open a serial connection to display values
  Serial.begin(9600);
  // set the LED pins as outputs
  // the for() loop saves some extra coding
  for (int pinNumber = 2; pinNumber < 5; pinNumber++) {
    pinMode(pinNumber, OUTPUT);
    digitalWrite(pinNumber, LOW);
  }
}

void loop() {
  // read the value on AnalogIn pin 0
  // and store it in a variable
  int sensorVal = analogRead(sensorPin);

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

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

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

  // convert the voltage to temperature in degrees C
  // the sensor changes 10 mV per degree
  // the datasheet says there's a 500 mV offset
  // ((volatge - 500mV) times 100)
  Serial.print(", degrees C: ");
  //float temperature = (voltage - .5) * 100; // for TMP 36
  float temperature = (voltage) * 100; // for LM 35
  Serial.println(temperature);

  // if the current temperature is lower than the baseline
  // turn off all LEDs
  if (temperature < baselineTemp + 2) {
    digitalWrite(2, LOW);
    digitalWrite(3, LOW);
    digitalWrite(4, LOW);
  } // if the temperature rises 2-4 degrees, turn an LED on
  else if (temperature >= baselineTemp + 2 && temperature < baselineTemp + 4) {
    digitalWrite(2, HIGH);
    digitalWrite(3, LOW);
    digitalWrite(4, LOW);
  } // if the temperature rises 4-6 degrees, turn a second LED on
  else if (temperature >= baselineTemp + 4 && temperature < baselineTemp + 6) {
    digitalWrite(2, HIGH);
    digitalWrite(3, HIGH);
    digitalWrite(4, LOW);
  } // if the temperature rises more than 6 degrees, turn all LEDs on
  else if (temperature >= baselineTemp + 6) {
    digitalWrite(2, HIGH);
    digitalWrite(3, HIGH);
    digitalWrite(4, HIGH);
  }
  delay(1);
}