01-04-2014, 12:19 PM
DESIGN AND CONSTRUCTION OF MICROCONTROLLER BASED TEMPERATURE CONTROLLER
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ABSTRACT
A Microcontroller based Temperature controller (or simply digital Thermometer) is an
electronic instrument that can measure body or ambient temperature over a long period of time.
It consists of sensors, multiplexer, Analogue-to-Digital Converters (ADC), microcontroller and a
display unit. Microcontrollers have an on-board memory that is large enough to hold data that is
recorded for a period of time. The memory in Embedded systems may be flash memory,
Registers, accumulator, banks, EEPROM or Static Random Access Memory that is battery
backed. Microcontroller based Temperature controller are provided with real time clocking to
measure and display instantaneous temperature of a system.
In this project, a digital thermometer for temperature measurement has been designed. The
system works around the famous 8051 family. The system is designed and developed to measure
the temperature over a wide range with the help of three temperature sensors viz Thermocouple
(type K), silicon fabricated IC (LM35) and a general purpose transistor (BC 108). The analogue
output of these sensors are multiplexed and fed into the microcontroller via an ADC. The result
shown with the aid of LCD module. The focus of design is on portability and low power
consumption for battery operated applications. The designed system is tested under different
conditions: at room temperatures, at low temperatures, at different temperatures, readings were
taken over a long time. For all these conditions, the system performed accurately.
INTRODUTION
Temperature is a fundamental quantity that expresses the level of hotness or coldness of
matter. Everybody is interested in knowing his/her body temperature and if possible the ambient
temperature as well. This is because temperature reveals a microscopic information about matter
at any given time. To measure temperature we need a measuring device called thermometer.
Although the most commonly used and readily available type of Thermometer is the Analogue
Liquid-in-glass thermometer. This project work explores the microcontroller technology to
design and construct a microcontroller based temperature controller. The Microcontrollers and
Embedded systems are the latest Technology rapidly replacing the both the common analogue
and digital electronic circuits. This is simply because the system has a central heart
(microcontroller) which is capable of controlling all the activities within the circuit. The
Microcontroller is very versatile in operation being that it can be programmed and re-
programmed at any time to suite your desired purpose. Microcontrollers are being designed into
more and more products e.g motor cars, watching machine, mobile phones, robots, measuring
and monitoring instruments in various fields such as digital thermometer, rainguage, voltmeters,
ammeters, magnetometer e.t.c. A major requirement or challenge of embedded system is that it
requires engineers with both software and hardware design capabilities.
WHY MICROCONTROLLER BECOMES MOST DESIRABLE
With the advancement of technology, requirements for electronic devices are becoming
more and more complex. Due to this increase in complexity, there is need to device simple and
flexible electronic circuits alternate to the bulky digital and analogue circuit that incorporate
several ICs, Op-Amps, Oscillators, relays e.t.c. For instance, a few line of instruction codes can
generate the square wave pulse needed in the power inerter systems, instead of building a another
sub- circuit (Oscillator stage) to achieve oscillation. Embedded system is an advance means of
implementing the much required complex functions for electronic circuit. It can be used to
collect and analyse real time data from analogue and digital measurement sources such as
sensors and devices under test. The microcontroller is more or less like a micro-computer,
though it is design to achieve purposes different from that of micro-computer. Both have central
and major IC (microcontroller for Embedded systems and microprocessor for micro-
computer).Unlike the micro-computer, The Embedded systems major IC can be reprogrammed
or adjusted after circuit implementation .