Arduino LM35 temperature sensor with LCD Display

I added my LM35 Temperature Sensor to my Arduino again and added a display to show how hot it is... ;)

I have used the LM35 already some month ago; It is a very easy to setup device.

Here is my Code (UPADTE 2015.08.21; This is my final code.):

// Written 2015 by Johannes Findeisen 

#include <LiquidCrystal.h>

// Initialize the LCD code. Take care of the pins I use. The first two pins 
// are 12 and 11 in most examples around the web. I use pin 7 and 6 because of 
// nicer wiring on my breadboard.
// Read this for more information:
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);

// Define how many samples should be collected every $collectDelay miliseconds.
// After sample collection the temperature is beeing calculated and then
// send to the LCD. 
int samples = 16;

// Collect delay between each sample. 
int collectDelay = 2000;

// The pin where the status LED is connected to.
int ledPin = 13;

// The analog input pin where the LM35 is connected to.
int tempPin = 0;

// Just some variable initializations.
float tempC = 0;
float tempClast = 0;
float tempF = 0;

void setup() {
  pinMode(ledPin, OUTPUT);
  lcd.begin(16, 2);
  // Get data for the first time.
  // Read this to understand the temperature calculation:
  tempC = (5.0 * analogRead(tempPin) * 100.0) / 1024.0;
  tempClast = tempC;
  // Celsius to Fahrenheit conversion
  tempF = (tempC * 9) / 5 + 32;
  // Refresh the LCD output

void loop() {
  int i;
  tempC = 0;
  for(i = 0; i <= (samples - 1); i++) {
    tempC = tempC + ((5.0 * analogRead(tempPin) * 100.0) / 1024.0);
    digitalWrite(ledPin, HIGH);
    delay((collectDelay / 2));
    digitalWrite(ledPin, LOW);
    delay((collectDelay / 2));
  // Calculate temperature
  tempC = tempC / (float)samples;
  // Celsius to Fahrenheit conversion.
  tempF = (tempC * 9) / 5 + 32;
  // Print results to the display.
  // Remember current temperature for next run.
  tempClast = tempC;

// Prints results to the display
void lcd_refresh() {
  lcd.setCursor(0, 0);
  lcd.print((char)40); // ASCII code 40 = "("
  if(tempClast > tempC) {
    lcd.print((char)60); // ASCII code 60 = "<"
  } else if(tempClast < tempC) {
    lcd.print((char)62); // ASCII code 62 = ">"
  } else {
    lcd.print((char)61); // ASCII code 61 = "="
  lcd.print((char)41); // ASCII code 41 = ")"
  lcd.print((char)58); // ASCII code 58 = ":"
  lcd.setCursor(0, 1);
  lcd.print((char)223); // ASCII code 223 = "°"
  lcd.print((char)223); // ASCII code 223 = "°"

Some other sources:

Have fun with it... ;)

My AVR Development Board

I build a new dev board for my AVR and Arduino development. My old one really was too small... Since I am daily are working on the evaluation of all the nice and tiny IC's in my electronics box I needed this. Maybe it will become too small in some time but currently it helps me a lot.

It consists of two large breadboards and a wooden panel underneath with four rubber foots. I will work on optimizing this in the future and maybe I will write a document, describing how to build it like mine... ;)

Attiny13 Blink example

Image of Attiny13 MCUJust to keep and share the code... Here is the code for making a LED blink using an Attiny13 MCU from Atmel.

I got a package with about 30 AVR MCU's from different kind yesterday and now I will give them all a try. The next step with the Attiny13 is to build a thermometer with a RGB LED as indicator of the temperature. As temperature sensor I will use the LT1025 chip which I tried some days ago. I got many logic IC's too so it will be a hackish time this december. I will post the code and circuit here in some days when everything is working properly... ;)

#include <avr/io.h>
#include <util/delay.h>

#define LED_PIN PB4

int main(void) {

  // Configure LED_PIN (PB4) as output
  DDRB |= (1 << LED_PIN);

  while (1) {
    PORTB |= (1 << LED_PIN);
    PORTB &= ~(1 << LED_PIN);
  return 0;

Have fun... ;)

Evaluating LT1025

Today I found a chip named LT1025. It is a Thermocouple Cold Junction Compensator from Linear Technology which is very easy to use for building temperature sensors for measurement and control and can also be used to convert a heat gradient into electricity.

It took about 5 minutes to get it working in the Arduino environment.

Just order some samples from Linear, they will send you one or two without charge... ;)

Evaluating 74HC238

Image of 74hc238 icI am currently working me thru my box of microchips and other electronic stuff. I found some 74HC238 IC's today and gave them a try. It was no very spectacular event but it's nice to know what I have laying around when starting the next AVR project.

The 74HC238 is a high speed CMOS 3 to 8 line decoder which makes it possible to control 8 outputs with only 3 input lines. You will find more information and the datasheet at Sparkfun.

I used it to control 8 LED's with my Arduino using just 3 output pins. Nothing worth to show you a photo... ;)