Introduction: Arduino Based Digital Thermometer

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In this project, an Arduino based digital thermometer is designed that can be used to analyze the temperature of the room.

The thermometer is generally used as a temperature measuring instrument. There are various principles that can be used to measure the temperature like the thermal expansion of solids or liquids, the pressure of the gas, measurement of infrared energy, etc.

Arduino based digital thermometer is outlined that can be used to analyze the temperature of the room. LM35 LM35 is a temperature sensor. The output voltage of this sensor is directly proportional to the temperature in centigrade. LM35 can be utilized in the range of -550C to +1500C with +/- 0.750C accuracy.


Arduino Uno

LM35 Temperature sensor

16x2 LCD Display

Step 1: Circuit Design of Digital Thermometer

The temperature sensor used in this project is LM35. The output of a temperature sensor is directly proportional to the temperature but in analog form. Hence, the output of LM35 means pin 2 is connected to analog input A0 of Arduino.

As it is a digital thermometer, we need to convert the analog values of temperature to digital and display the result on a display like LCD, etc. 16X2 LCD is used. Pin no 1 and 2 of LCD are connected to ground and supply respectively. In order to manage the contrast of the display, Pin 3 of LCD is attached to the wiper of a 10 KΩ POT.

The remaining terminals of POT are attached to supply and ground. Pins 15 and 16 of LCD are used to revolve the backlight of the LCD which is connected to supply and ground respectively. In order to display the information on LCD, we require 4 data pins of the LCD. Pins 11 – 14 (D4 – D7) are attached to Pins 5 – 2 of Arduino. Pins 4, 5 and 6 (RS, RW and E) of LCD are control pins. Pins 4 (RS) of LCD is connected to pin 7 of Arduino. Pin 5 (RW) is connected to the ground. Pin 6 (E) is connected to pin 6 of Arduino.

Step 2: Working of Digital Thermometer

A high precision digital thermometer is outlined in this project. The working of the circuit is as explained below.

The temperature sensor i.e. LM35 constantly analyzes the room temperature and gives an analog identical voltage which is directly proportional to the temperature.

This data is given to Arduino through A0. As per the code is written, the Arduino transforms this analog voltage value to digital temperature readings.

This value is shown on the LCD. The output displayed on the LCD is an exact reading of room temperature in centigrade.

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Step 3: Run a Program


LiquidCrystal lcd(7,6,5,4,3,2);

const int Sensor = A0;

byte degree_symbol[8] =











void setup()


pinMode(Sensor, INPUT);


lcd.createChar(1, degree_symbol);


lcd.print(" Digital ");


lcd.print(" Thermometer ");




void loop()


float temp_reading=analogRead(Sensor);

float temperature=temp_reading*(5.0/1023.0)*100;




lcd.print("Temperature in C");