Digital Thermometer using Arduino and LM35 Temperature Sensor

Arduino

BySaddam 21

Digital Thermometer Project using Arduino and LM35 Temperature Sensor

Thermometers are useful apparatus being used since long time for temperature measurement. In this project we have made an Arduino based digital thermometer to display the current ambient temperature and temperature changes on a LCD unit in real time . It can be deployed in houses, offices, industries etc. to measure the temperature. This project is based on Arduino which communicates here with LM35 temperature sensor and a 16x2 display unit. We can divide this arduino based thermometer into three sections - The first senses the temperature by using temperature sensor LM 35, second section converts the temperature value into a suitable numbers in Celsius scale which is done by Arduino, and last part of system displays temperature on LCD. The same is demonstrated in below block diagram.

Arduino Thermometer Block Diagram

In this Arduino LM35 temperature sensor interfacing, Arduino Uno is used to control the whole process. An LM35 temperature sensor is used for sensing environment temperature which gives 1 degree temperature on every 10mV change at its output pin. You can easily check it with voltmeter by connecting Vcc at pin 1 and Ground at pin 3 and output voltage at pin 2 of LM35 sensor. For an example if the output voltage of LM35 sensor is 250m volt, that means the temperature is around 25 degree Celsius.

 

Arduino reads output voltage of temperature sensor by using Analog pin A0 and performs the calculation to convert this Analog value to a digital value of current temperature. After calculations arduino sends these calculations or temperature to 16x2 LCD unit by using appropriate commands of LCD.

 

Circuit Components

Arduino

In this project we have used a microcontroller to control whole the process of system that is ARDUINO board. Actually arduino is not a mere controller as it has an operating system or boot-loader which runs on AVR controllers. Arduino is an open source hardware platform and very useful for project development purpose. There are many types of arduino boards like Arduino UNO, arduino mega, arduino pro mini, Lilypad etc. are available in the market or you can also build one by yourself.

Arduino Uno

 

LM35 Temperature Sensor

LM35 is a 3 pin temperature sensor which gives 1 degree Celsius on every 10mVolt change. This sensor can sense up to 150 degree Celsius temperature. 1 number pin of lm35 sensor is Vcc, second is output and third one is Ground.

LM35 Temperature Sensor Pins

 

Pin No

Function

Name

1

Supply voltage; 5V (+35V to -2V)

Vcc

2

Output voltage (+6V to -1V)

Output

3

Ground (0V)

Ground

 

LCD

16x2 LCD unit is widely using in embedded system projects because it is cheap, easily availablet, small in size and easy to interface. 16x2 have two rows and 16 columns, which means it consist 16 blocks of 5x8 dots. 16 pin for connections in which 8 data bits D0-D7 and 3 control bits namely RS, RW and EN. Rest of pins are used for supply, brightness control and for backlight.

16x2 LCD Display

 

Power Supply

Arduino Board already have an inbuilt power supply section. Here we only need to connect a 9 volt or 12 volt adaptors with the board.

 

Circuit Diagram and Explanation

Arduino Based Digital Thermometer Circuit Diagram

Circuit digram for digital thermometer using Arduino LM35 temperature sensor, is shown in the above figure. Make the connections carefully as shown in the schematic. Here 16x2 LCD unit is directly connected to arduino in 4-bit mode. Data pins of LCD namely RS, EN, D4, D5, D6, D7 are connected to arduino digital pin number 7, 6, 5, 4, 3, 2. A temperature sensor LM35 is also connected to Analog pin A0 of arduino, which generates 1 degree Celsius temperature on every 10mV output change at its output pin.

 

Arduino LM35 Code & Explanation

To write the code for digital thermometer, we need to write the code for Arduino, LM35 Temperature Sensor, and 16x2 LCD module interfacing. First we include library for LCD unit and then we defines data and control pins for LCD and temperature sensor.

Ex:

code

After getting analog value at analog pin we reads that value using Analog read function and stores that value in a variable. And then by applying given formula converts it in temperature.

float analog_value=analogRead(analog_pin);           

float Temperature=analog_value*factor*100

where

factor=5/1023

analog_value= output of temperature sensor

code for arduino digital temperature sensor

Here degree symbol is creates using custom character method

Arduino Temperature sensor code

Code

/*-----------Arduino LM35 Code-------------*/

/*-----------Digital Thermometer Using Arduino-------------*/

#include<LiquidCrystal.h>
LiquidCrystal lcd(7,6,5,4,3,2);

#define sensor A0

byte degree[8] = 
              {
                0b00011,
                0b00011,
                0b00000,
                0b00000,
                0b00000,
                0b00000,
                0b00000,
                0b00000
              };

void setup()
{
  lcd.begin(16,2);
  lcd.createChar(1, degree);
  lcd.setCursor(0,0);
  lcd.print("    Digital    ");
  lcd.setCursor(0,1);
  lcd.print("  Thermometer   ");
  delay(4000);
  lcd.clear();
  lcd.print(" Circuit Digest  ");
  delay(4000);
  lcd.clear();
}

void loop()
{
  /*---------Temperature-------*/
     float reading=analogRead(sensor);
     float temperature=reading*(5.0/1023.0)*100;
     delay(10);
  
  /*------Display Result------*/
    lcd.clear();
    lcd.setCursor(2,0);
    lcd.print("Temperature");
    lcd.setCursor(4,1);
    lcd.print(temperature);
    lcd.write(1);
    lcd.print("C");
    delay(1000);
}

Video

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Comments

  • QAMAR SHAIKH's picture
    QAMAR SHAIKH
    Dec 18, 2015

    TRIED WORKING VERY GOOD

  • harish's picture
    harish
    May 17, 2016

    how to create your own programme code sir
    i want to make new project
    and how to understand that code line
    pls tell that

  • harish's picture
    harish
    May 18, 2016

    it is a correct temperature or not

  • Muhammad's picture
    Muhammad
    Jul 17, 2016

    It is very good and must project.Thank you sir.

  • Hariprasath's picture
    Hariprasath
    Sep 25, 2016

    Hello there ,
    I am using an lm35 dz and arduino r3. My readings are varied from 0 to 500 degree celcius. What should i do for this.

  • Maddy's picture
    Maddy
    Oct 07, 2016

    Have you followed the code properly? Apply the given formula to convert the Analog temp reading into Degree C.

  • shafqat Riaz's picture
    shafqat Riaz
    Jul 15, 2018

    i have same problem with it

  • thummar's picture
    thummar
    Jan 20, 2019

    Dear sir,

        please tell me the soluion if you get a correct ans.

    my problem is that if i not connect the sensor to the arduno uno however arduno generat temoreture in -18 to 500 c range.

    warm regard

    thummar bhadresh

    (=918758236036)

  • Aswinth Raj's picture
    Aswinth Raj
    Jan 21, 2019

    Hi,

    You are not supposed to read anything from a pin if it is not connected to anything. If the pin is left free, it is said to be in floating condition and the value read from it can be anything from 0 toso yes there is no suprise that you are getting random calues as output.

    If you want to read zero, use a pull down resistor. That is connect a 10 resistor from the analog pin to the ground pin and you will be able to read zero 

  • Gainji GM's picture
    Gainji GM
    Mar 20, 2017

    Sir here is a code for Arduino based digital thermometer how can i add buzzer to alert if temperature increase
    (if temperature >50) then buzzer beeps

    #include<LiquidCrystal.h>
    LiquidCrystal lcd(2,4,7,8,9,10);

    const int Sensor = A0;
    byte degree_symbol[8] =
    {
    0b00111,
    0b00101,
    0b00111,
    0b00000,
    0b00000,
    0b00000,
    0b00000,
    0b00000
    };
    void setup()
    {
    pinMode(Sensor, INPUT);
    lcd.begin(16,2);
    lcd.createChar(1, degree_symbol);
    lcd.setCursor(0,0);
    lcd.print(" Digital ");
    lcd.setCursor(0,1);
    lcd.print(" Thermometer ");
    delay(4000);
    lcd.clear();
    }
    void loop()
    {

    float temp_reading=analogRead(Sensor);
    float temperature=temp_reading*(5.0/1023.0)*100;
    delay(10);

    lcd.clear();
    lcd.setCursor(0,0);
    lcd.print("Temperature in C");
    lcd.setCursor(4,1);
    lcd.print(temperature);
    lcd.write(1);
    lcd.print("C");
    delay(1000);
    }

  • Anna 's picture
    Anna
    Mar 26, 2017

    gd eve sir ! I am beginner in using arduino.Could I ask what codes i should add if I put a beep sound /alarm buzzer to alert if temperature increase.. thank you so much sir.

  • Eranna 's picture
    Eranna
    Mar 31, 2017

    I tried this project n got output ...plz ping code for buzzer also

  • karamjeet's picture
    karamjeet
    Apr 03, 2017

    I am not getting the output on lcd

  • Speedfox's picture
    Speedfox
    Aug 11, 2017

    I want to make one thermometer like that but some different things, like using an arduino mini, extend the range and seal the temp sensor (to put it on boiling water) and add a computer speaker to know when you reach a determinate temp. do you think that can be possible?

  • Mandaza's picture
    Mandaza
    Oct 09, 2017

    if the code is incorrect ,errors been detected what should l do

  • sukhbir 's picture
    sukhbir
    Apr 11, 2018

    What is A E S shown below the LCD

  • Aswinth Raj's picture
    Aswinth Raj
    Apr 15, 2018

    It is a potentiometer, it can be used to adjust the contract of the LCD. The pins AES are the three pins on a potentiometer respectively 

  • la4yt's picture
    la4yt
    Jun 15, 2018

    How to get view with just one digit after,

  • EMILY's picture
    EMILY
    Aug 27, 2018

    someone got the buzzer code?

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