12-04-2011, 03:25 PM
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1. INTRODUCTION
1.1 Context
This project explains about a simple low cost circuit which can be mainly used in large scale industries to detect the high temperature and take immediate measures. This circuit is used to sense the temperature at a place. It indicates the temperature on the 7 Segment Display with the help of microcontroller. This circuit makes use of SL100 which is a 3 pin centigrade temperature sensor IC. It directly senses the temperature and sends the data to the controller.
The complete project is built around the 8051 micro controller. PCB Wizard Schematic generation software is employed to prepare the schematic for development of project. Hardware is built according to schematic prepared by soldering each component on the general purpose PCB. Source code is developed using Keil micro vision software. μVision is an IDE (Integrated
Development Environment) that helps we write, compile, and debug embedded programs. The written source code is dumped into the microcontroller IC using a Programmer. To dump the code into microcontroller micro C Flash software is used.
1.2 Resolve
The industries in which Temperature plays a major role, needs thousands of degree centigrade of temperature. In such industries, it is impossible for a normal human being to enter and check the temperature. So by using this Temperature Monitoring system we can solve the problem. Here we use transmitter and receiver. Transmitter will be kept where the temperature has to measure and the receiver is kept in a monitor room. If any changes occur in the temperature, the sensor placed in the transmitter section will sense it and pass it to the receiver section.
1.3 Scope of the project
• This project is developed in order to help the Industrialist to know the correct temperature of a particular room or a big furnace without any difficulties and not even entering into the room.
• Based on the responses and reports obtained as a result of the significant development in the working system in INDUSTRIES, this project can be further extended to meet the demands according to situation.
• This can be further implemented, so that the temperature can be controlled, if it exceeds the limit by providing large fans etc. Thus becomes the user friendliness.
• Additional modules can be added without affecting the remaining modules. This allows the flexibility and easy maintenance of the developed system.
This system consists of following features over manual system:
• There is no time lag to operate the device.
• Accuracy.
2. Block Diagram
2.1 Overview
Block Diagram of Temperature Monitoring System
Description
This project uses AT89C51 microcontroller for programming and operation The block diagram of temperature monitoring system consists of temperature sensor, ADC, microcontroller and 7 Segment Display. SL100 is used as temperature sensor it senses the temperature. The output of Temperature sensor is in the form of analog signal. ADC0809 is used to convert this analog signal to digital. The output of ADC is given to the Microcontroller. The output of controller will be displayed on the 7 Segment Display. It also consists of the power supply, which is of single-phase 230V ac. This should be given to step down transformer to reduce the 230V ac voltage to lower value. i.e., to 12V ac this value depends on the transformer inner winding. The output of the transformer is given to the rectifier circuit. This rectifier converts ac voltage to dc voltage. But the voltage may consist of ripples or harmonics.
To avoid these ripples, the output of the rectifier is connected to filter. The filter thus removes the harmonics. This is the exact dc voltage of the given specification. But the controller operates at 5V dc. So the regulator is required to reduce the voltage. Regulator 7805 produces 5V dc.
Here the microcontroller gets activated when power supply is given to it. Then the temperature will sense the temperature and sends the output in form of analog to ADC 0809. As the microcontroller does not accept analog inputs so we are using A to D converter. There it converts into digital from analog signals. The resultant output will be displayed on the 7 Segment display.
3. Survey of Literature
Here this project consists of Microcontroller, sensor, A to D converter, 7 Segment Display and Op amp LM 324, 555 timers and crystal oscillator.
3.1 Microcontroller
Introduction
A Micro controller consists of a powerful CPU tightly coupled with memory, various I/O interfaces such as serial port, parallel port timer or counter, interrupt controller, data acquisition interfaces-Analog to Digital converter, Digital to Analog converter, integrated on to a single silicon chip.
If a system is developed with a microprocessor, the designer has to go for external memory such as RAM, ROM, EPROM and peripherals. But controller is provided all these facilities on a single chip. Development of a Micro controller reduces PCB size and cost of design.
One of the major differences between a Microprocessor and a Micro controller is that a controller often deals with bits not bytes as in the real world application.
Intel has introduced a family of Micro controllers called the MCS-51.
The Major Features:
• Compatible with MCS-51 products
• 4k Bytes of in-system Reprogrammable flash memory
• Fully static operation: 0HZ to 24MHZ
• Three level programmable clock
• 128 * 8 –bit timer/counters
• Six interrupt sources
• Programmable serial channel
• Low power idle power-down modes
AT89C51 is 8-bit micro controller, which has 4 KB on chip flash memory, which is just sufficient for our application. The on-chip Flash ROM allows the program memory to be reprogrammed in system or by conventional non-volatile memory Programmer. Moreover ATMEL is the leader in flash technology in today’s market place and hence using AT 89C51 is the optimal solution.
3.2 AT89C51 MICROCONTROLLER ARCHITECTURE
The 89C51 architecture consists of these specific features:
• Eight –bit CPU with registers A (the accumulator) and B
• Sixteen-bit program counter (PC) and data pointer (DPTR)
• Eight- bit stack pointer (PSW)
• Eight-bit stack pointer (Sp)
• Internal ROM or EPROM (8751) of 0(8031) to 4K (89C51)
• Internal RAM of 128 bytes
• Thirty –two input/output pins arranged as four 8-bit ports:p0-p3
• Two 16-bit timer/counters: T0 and T1
• Full duplex serial data receiver/transmitter: SBUF
• Control registers: TCON, TMOD, SCON, PCON, IP, and IE
• Two external and three internal interrupts sources.
• Oscillator and clock circuits.
Why AT89C51?
The system requirements and control specifications clearly rule out the use of 16, 32 or 64 bit micro controllers or microprocessors. Systems using these may be earlier to implement due to large number of internal features. They are also faster and more reliable but, 8-bit micro controller satisfactorily serves the above application. Using an inexpensive 8-bit Microcontroller will doom the 32-bit product failure in any competitive market place.
Coming to the question of why to use AT89S52 of all the 8-bit microcontroller available in the market the main answer would be because it has 8 Kb on chip flash memory which is just sufficient for our application. The on-chip Flash ROM allows the program memory to be reprogrammed in system or by conventional non-volatile memory Programmer. Moreover ATMEL is the leader in flash technology in today’s market place and hence using AT 89S52 is the optimal solution.
3.3 Types of memory:
The 89C51 have three general types of memory. They are on-chip memory, external Code memory and external Ram. On-Chip memory refers to physically existing memory on the micro controller itself. External code memory is the code memory that resides off chip. This is often in the form of an external EPROM. External RAM is the Ram that resides off chip. This often is in the form of standard static RAM or flash RAM.
a) Code memory
Code memory is the memory that holds the actual 89C51 programs that is to be run. This memory is limited to 64K. Code memory may be found on-chip or off-chip. It is possible to have 4K of code memory on-chip and 60K off chip memory simultaneously. If only off-chip memory is available then there can be 64K of off chip ROM. This is controlled by pin provided as EA.
b) Internal RAM
The 89C51 have a bank of 128 of internal RAM. The internal RAM is found on-chip. So it is the fastest Ram available. And also it is most flexible in terms of reading and writing. Internal Ram is volatile, so when 89C51 is reset, this memory is cleared. 128 bytes of internal memory are subdivided. The first 32 bytes are divided into 4 register banks. Each bank contains 8 registers. Internal RAM also contains 128 bits, which are addressed from 20h to 2Fh. These bits are bit addressed i.e. each individual bit of a byte can be addressed by the user. They are numbered 00h to 7Fh. The user may make use of these variables with commands such as SETB and CLR.
Flash memory is a nonvolatile memory using NOR technology, which allows the user to electrically program and erase information. Flash memory is used in digital cellular phones, digital cameras, LAN switches, PC Cards for notebook computers, digital set-up boxes, embedded controllers, and other devices.
