CELSIUS SCALE DIGITAL THERMOMETER USING AT89C51 AND LM35

Mini Project report submitted toV.R.Siddhartha Engineering Collegefor the award of the degreeof

Bachelor of TechnologyInElectrical and Electronics Engineering

by

Sk.Shani (128w1a0247)S.Komali (128w1a0249)(?).Rajeeswari (128w1a0242)N.Navarshi (128w1a0258)Under the guidance ofsmt.Lakshmi Kumari(?)

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERINGVELAGAPUDI RAMAKRISHNA SIDDHARTHA ENGINEERING COLLEGE(AUTONOMOUS)(Affiliated to JNTUK,Approved by UGC)December 2015

Abstract:

INTRODUCTION OF THE TOPIC:

Celsius scale digital thermometer displays the ambient temperature through a LCD display.

.The circuit consists of two sections. One is that which senses the temperature.This is a

temperaure sensor LM35.The other section converts the temperature value into a suitable

number in Celsius scale which is done by the ADC0804.A digital thermometer can be easily

made by interfacing a temperature sensor LM35 and a analog to digital converter ADC0804 to

the micro controller AT89C51.The analog temperature sensor LM35 has the advantage of

providing an output directly proportional to the Celsius temperature, without having the need to

be calibrated and the 8 bit analog to digital converter ADC0804, uses the successive

approximation conversion technique. This ADC0804 is controlled by the microcontroller which

processes its output to display the resultant temperature reading.The LM35 IC generates a

10mV variation to its output voltage for every degree Celsius change in temperature. The

Output of the temperature sensor is analog in nature so we use an analog to digital convertor for

converting the analog input to its equivalent binary output.ADC0804 is a single channel

convertor which converts the analog input upto a range of 5V to an equivalent 8-bit binary

output. The binary output of ADC is fed parallel to a port of the microcontroller .The

microcontroller reads the input through ADC and displays the corresponding decimal value on

LCD.