Under the Guidance of Submitted by Project Title PRACTICAL TEMPERATURE CONTROLLER Under the Guidance of Submitted by

ABSTRACT This practical temperature controller controls the temperature of any device according to its requirement for any industrial application. It also displays the temperature on an LCD displays in the range of –55°C to +125°C. At the heart of the circuit is the microcontroller from 8051 family which controls all its functions. An IC DS1621 is used as temperature sensor. The DS1621 Digital Thermometer and Thermostat provides 9-bit temperature readings, which indicate the temperature of the device. User-defined temperature settings are stored in a nonvolatile memory EEPROM through 8051 series microcontroller .Maximum and minimum temperature settings are entered to the MC through a set of switches which are stored in the EEPROM -24C02.Maximum and minimum setting are meant for allowing any hysteresis necessary. Set button is used first and then the temperature setting by INC and then the enter button. Similarly for the DEC button. A relay is driven from the MC through a transistor driver. The contact of the relay is used for the load, shown as a lamp in the circuit. For high power heater load a contactor may be used, the coil of which is operated by the relay contacts in place of the lamp as shown. Standard power supply of 12 volt DC and 5 volt through a regulator are made from a step down transformer along with a bridge rectifier and filter capacitor.

BLOCK DIAGRAM

HARDWARE REQUIREMENTS Transformer. Voltage regulator Diodes Capacitor. Resistors. Microcontroller (AT89S52). Temperature sensor (DS1621). BC547. Relay. Lamp. LCD(16x2). 24C02

POWER SUPPLY Bridge rectifier 5v Regulator 230 V AC 50 Hz 5V DC Filter(470µf) 12V step down transformer

It is a smaller computer Has on-chip RAM, ROM, I/O ports... MICROCONTROLLER It is a smaller computer Has on-chip RAM, ROM, I/O ports... RAM ROM I/O Port Timer Serial COM Port Microcontroller CPU A single chip

INTERNAL STRUCTURE OF A MICRO CONTROLLER-AT89S52/51 CPU On-chip RAM On-chip ROM for program code 4 I/O Ports Timer 0 Serial Port OSC Interrupt Control External interrupts Timer 1 Timer/Counter Bus Control TxD RxD P0 P1 P2 P3 Address/Data Counter Inputs

Features of AT89S51/52 Compatible with MCS®-51 Products 8K Bytes of In-System Programmable (ISP) Flash Memory Endurance: 10,000 Write/Erase Cycles 4.0V to 5.5V Operating Range Fully Static Operation: 0 Hz to 33 MHz 256 x 8-bit Internal RAM 32 Programmable I/O Lines Three 16-bit Timer/Counters Eight Interrupt Sources Full Duplex UART Serial Channel Interrupt Recovery from Power-down Mode Watchdog Timer Dual Data Pointer

Pin Description

TEMPERATURE SENSOR(DS1621) Measures temperatures from -55°C to +125°C in 0.5°C increments. Fahrenheit equivalent is -67°F to 257°F in 0.9°F increments. Temperature is read as a 9-bit value (2-bytetransfer) Wide power supply range (2.7V to 5.5V) Converts temperature to digital word in less Than 1 second Thermostatic settings are user definable and Non volatile. Data is read from/written via a 2-wire serial interface (open drain I/O lines). Applications include thermostatic controls, industrial systems, consumer products, thermometers, or any thermal sensitive system It is as 8-pin DIP or SO package Features

SDA - 2-Wire Serial Data Input/ Output SCL - 2-Wire Serial Clock GND - Ground TOUT - Thermostat Output Signal A0 - Chip Address Input A1 - Chip Address Input A2 - Chip Address Input VDD - Power Supply Voltage

RELAY IT IS A ELECTRO MAGNETIC SWITCH USED TO CONTROL THE ELECTRICAL DEVICES COPPER CORE MAGNETIC FLUX PLAYS MAIN ROLE HERE

The relay's switch connections are usually labeled COM, NC and NO: COM = Common, always connect to this; it is the moving part of the itch. NC = Normally Closed, COM is connected to this when the relay coil is off. NO = Normally Open, COM is connected to this when the relay coil is on

BC547 The BC547 transistor is an NPN Epitaxial Silicon Transistor. The BC547 transistor is a general-purpose transistor in small plastic packages. It is used in general-purpose switching and amplification BC847/BC547 series 45 V, 100 mA NPN general-purpose transistors. Whenever base is high, then current starts flowing through base and emitter and after that only current will pass from collector to emitter  

Working of project The project uses a digital temperature sensor DS1621 the surface which is capable of sensing the temperature & delivering digital data at its output which are connected to the controller. The LCD displays the present temperature, maximum temperature and minimum temperature. The maximum and minimum values are entered through switches attached to the microcontroller. The maximum and minimum settings are stored in the EEPROM. If the temperature goes below the minimum value the heater is on as indicated by a lamp connected through a relay driven by a transistor connected to the microcontroller. If the temperature crosses the maximum value the heater is switched off.

Soft ware Requirements Keil an ARM Company makes C compilers, macro assemblers, real-time kernels, debuggers, simulators, integrated environments, evaluation boards, and emulators for ARM7/ARM9/Cortex-M3, XC16x/C16x/ST10, 251, and 8051 MCU families. Compilers are programs used to convert a High Level Language to object code. Desktop compilers produce an output object code for the underlying microprocessor, but not for other microprocessors.

i.e the programs written in one of the HLL like ‘C’ will compile the code to run on the system for a particular processor like x86 (underlying microprocessor in the computer). For example compilers for Dos platform is different from the Compilers for Unix platform  So if one wants to define a compiler then compiler is a program that translates source code into object code.

BIBILOGRAPHY “The 8051 Microcontroller and Embedded systems” by Muhammad Ali Mazidi and Janice Gillispie Mazidi , Pearson Education. ATMEL 89S52 Data Sheets. www.atmel.com www.beyondlogic.org www.wikipedia.org www.howstuffworks.com www.alldatasheets.com

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