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.
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.
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.
|
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.
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
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:
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
Here degree symbol is creates using custom character method
/*-----------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);
}
Comments
Dec 18, 2015
TRIED WORKING VERY GOOD
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
May 18, 2016
it is a correct temperature or not
May 28, 2016
Go through our initial Arduino projects to learn coding and Arduino like :LED Blinking with Arduino Uno. And yes Temperature is correct.
Jul 17, 2016
It is very good and must project.Thank you sir.
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.
Oct 07, 2016
Have you followed the code properly? Apply the given formula to convert the Analog temp reading into Degree C.
Jul 15, 2018
i have same problem with it
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)
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
Jan 29, 2017
good project
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);
}
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.
Mar 31, 2017
I tried this project n got output ...plz ping code for buzzer also
Apr 03, 2017
I am not getting the output on lcd
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?
Oct 09, 2017
if the code is incorrect ,errors been detected what should l do
Apr 11, 2018
What is A E S shown below the LCD
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
Jun 15, 2018
How to get view with just one digit after,
Aug 27, 2018
someone got the buzzer code?