Design And Construction Of A Digital Thermometer Using Arduino And LM35 Temperature Sensor

Electrical Electronics Engineering | Industrial Physics | Physics

The design and construction of a digital thermometer using an Arduino and LM35 temperature sensor involve combining electronic components to measure and display temperature accurately. Arduino, a versatile microcontroller, serves as the brain of the system, executing programmed instructions. The LM35 temperature sensor, a crucial component, ensures precise temperature measurements. The integration of these elements enables the thermometer to convert analog signals from the LM35 into digital data, facilitating easy interpretation and display. By employing Arduino’s programming capabilities, users can customize the thermometer’s functionality and enhance its adaptability to various environments. This project exemplifies the convergence of hardware and software expertise, showcasing the synergy between the Arduino microcontroller and the LM35 temperature sensor to create a sophisticated yet user-friendly digital thermometer.

Thermometers are useful apparatus being used since long time for temperature measurement. In this project an Arduino based digital thermometer to display the current ambient temperature and temperature changes on a LCD unit in real time was made. 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 16×2 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.

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRCT

TABLE OF CONTENT

CHAPTER ONE

INTRODUCTION
OBJECTIVE OF THE STUDY
SIGNIFICANCE OF THE STUDY
APPLICATION OF THE PROJECT
TYPES OF DIGITAL THERMOMETER
PROJECT ORGANISATION

CHAPTER TWO

LITERATURE REVIEW

2.0     LITERATURE REVIEW
2.1     HISTORICAL BACKGROUND ANDDEVELOPMENT OF THE STUDY
2.2     PHYSICAL PRINCIPLES OF THERMOMETRY
2.3     THERMOMETRIC MATERIALS
2.4     PRIMARY AND SECONDARY THERMOMETERS
2.5     CALIBRATION OF THERMOMETERS
2.6     REVIEW OF TWO KINDS OF CONVENTIONAL THERMOMETERS

CHAPTER THREE

3.0 METHODOLOGY

3.1 SYSTEM BLOCK DIAGRAM
3.2 COMPONENTS OF THE SYSTEM

3.3 SYSTEM CIRCUIT DIAGRAM

3.4 SYSTEM WORKING PRINCIPLE

3.5 POWER SUPPLY UNIT

CHAPTER FOUR

4.0 CONSTRUCTION PROCEDURE AND TESTING

4.1 CASING AND PACKAGING

4.2 ASSEMBLING OF SECTIONS

4.3 TESTING OF SYSTEM OPERATION

CHAPTER FIVE

5.1 CONCLUSIONS

5.2 RECOMMENDATION

5.3 REFERENCES

SYSTEM BLOCK DIAGRAM

Before carrying out any project, the block diagram must be drawn and fully understood. Block diagram gives a pictorial understanding of any work. The block diagram of the system is as below:

Components Needed:

Arduino board (e.g., Arduino Uno)
LM35 temperature sensor
Breadboard
Jumper wires
16×2 LCD display (optional, for visual output)
Potentiometer (for adjusting LCD contrast, if using)

Circuit Design:

The LM35 temperature sensor outputs an analog voltage proportional to the temperature it senses. We’ll connect it to one of the analog input pins of the Arduino to read this voltage. Here’s the circuit diagram:

Connect the components as follows:

LM35 Temperature Sensor:
- Pin 1 (Vs): Connect to +5V on Arduino
- Pin 2 (Vout): Connect to Analog Pin A0 on Arduino
- Pin 3 (Gnd): Connect to GND on Arduino
LCD Display (Optional):
- VSS: Connect to GND
- VDD: Connect to +5V
- VO: Connect to the middle pin of the potentiometer
- RS: Connect to digital pin 12 on Arduino
- RW: Connect to GND (for write mode)
- EN: Connect to digital pin 11 on Arduino
- D4-D7: Connect to digital pins 5, 4, 3, 2 on Arduino respectively
- A and K: Connect to +5V and GND for backlight

Arduino Code:

Now, let’s write the code to read the analog voltage from the LM35 sensor and convert it to temperature in Celsius. We’ll then display this temperature on the serial monitor and optionally on the LCD display if you have one connected.

cpp

#include <LiquidCrystal.h>
const int sensorPin = A0; // LM35 sensor connected to A0 pin

const float referenceVoltage = 5.0; // Reference voltage of Arduino

const float temperatureFactor = 100.0; // LM35 temperature scale factor
LiquidCrystal lcd(12, 11, 5, 4, 3, 2); // LCD pins
void setup() {

Serial.begin(9600); // Start serial communication

lcd.begin(16, 2); // Initialize LCD with 16x2 dimensions

}
void loop() {

int sensorValue = analogRead(sensorPin); // Read analog value from sensor

float voltage = (sensorValue / 1023.0) * referenceVoltage; // Convert analog value to voltage

float temperatureC = voltage * temperatureFactor; // Convert voltage to temperature in Celsius
 Serial.print("Temperature: ");

Serial.print(temperatureC);

Serial.println(" °C");
 lcd.setCursor(0, 0);

lcd.print("Temperature:");

lcd.setCursor(0, 1);

lcd.print(temperatureC);

lcd.print(" C");

delay(1000); // Delay for readability }

Explanation of the Code:

We first include the LiquidCrystal library for using the LCD display.
In the setup function, we initialize serial communication and the LCD display.
In the loop function, we read the analog value from the LM35 sensor and convert it to voltage.
We then convert the voltage to temperature in Celsius using the formula provided in the LM35 datasheet.
We print the temperature readings to the serial monitor and display them on the LCD.

Testing:

Upload the code to your Arduino board and open the serial monitor to see the temperature readings. If you have an LCD display connected, you should see the temperature displayed there as well.

Conclusion:

Congratulations! You’ve successfully designed and constructed a digital thermometer using an Arduino and an LM35 temperature sensor. You can further enhance this project by adding features like temperature calibration, Fahrenheit conversion, and alarm thresholds.