27-09-2013, 04:56 PM
PIR SENSOR BASED POWER SAVER FOR AUDITORIUM AND CONFRENCE HALL
PIR SENSOR .pdf (Size: 922.02 KB / Downloads: 69)
ABSTRACT:
Nowadays, human has become too busy and he is unable to find time even to operate the
lights and fans wherever not necessary. This can be seen more effectively in the case of lights
in the rooms. This project gives the best solution for electrical power wastage. Also the manual
operation is completely eliminated.
The Project Automatic auditorium control system using Microcontroller is an interesting
project which uses AT89S52 microcontroller as its brain. This system switches on the lights only
in darkness.PIR sensor is used for the movement reorganization. This is a simple, fit and forget
system. If some movement is identified in the auditorium the light will automatically switched
on else it will be off.
To operate the fans automatically, temperature has to be read continuously. For this,
Thermistor is used. Thermistor reads the temperature value continuously and gives this value to
the ADC. ADC0804 is used to convert analog data delivered by Light dependant Resistor (LDR)
into digital data. This ADC interfacing makes this project highly sensitive and user friendly.
LCD is used to display the related messages.
INTRODUCTION TO EMBEDDED SYSEMS
Embedded systems have grown tremendously in recent years, not only in their popularity
but also in their complexity. Gadgets are increasingly becoming intelligent and autonomous.
Refrigerators, air-conditioners, automobiles, mobile phones etc are some of the common
examples of devices with built in intelligence. These devices function based on operating and
environmental parameters.
The intelligence of smart devices resides in embedded systems. An embedded system, in
general, in co-operates hardware, operating systems, low-level software binding the operating
system and peripheral devices, and communication software to enable the device to perform
the pre-defined functions. An embedded system performs a single, well-defined task, is tightly
constrained, is reactive and computes results in real time.
EMBEDDED SOFTWARE
The software for the embedded systems is called firmware. The firmware will be written
in assembly languages for time or resource critical operations or using higher-level languages
like C or embedded C. The software will be simulated using micro code simulators for the target
processor. Since they are supposed to perform only specific tasks these programs are stored in
Read Only Memories (ROM’s).
APPLICATIONS
Embedded software is present in almost every electronic device you use today. There is
embedded software inside your watch, cellular phone, automobile, thermostats, industrial control
equipment and scientific and medical equipment. Defence services use embedded software to
guide missiles and detect aircraft’s communication satellites, medical instruments and deep space
probes would have been nearly impossible without these systems. Embedded systems cover such
as broad range of products that generalization is difficult.
THE STACK AND THE STACK POINTER
The stack refers to an area of internal RAM that is used in conjunction with certain
opcodes to store and retrieve data quickly. The 8-bit Stack Pointer (SP) register is used by the
8051 to hold an internal RAM address that is called the top of the stack. The address held in
the SP register is the location in internal RAM where the last byte of data was stored by a stack
operation.
When data is to be placed on the stack, the SP increments before storing data on the stack
so that the stack grows up, as data is stored. As data is retrieved from the stack, the byte is read
from the stack, and then the SP decrements to point to the next available byte of stored data.
The stack is limited in height to the size of the internal RAM. The stack has the potential
to overwrite valuable data in the register banks, bit-addressable RAM, and scratch-pad RAM
areas.
EXTERNAL MEMORY
The system designer is not limited by the amount of internal RAM and ROM available on chip.
Two separate external memory spaces are accessed using the 16-bit PC and DPTR. Different
control pins are used for enabling external ROM and RAM chips. Internal circuitry accesses the
correct physical memory, depending on the machine cycle state and the opcode being executed.
The 8051 accesses external RAM whenever the EA (external access) pin is connected to
ground or when the PC contains an address higher than the last address in the internal 4K ROM
(0FFh). During any memory cycle access, port 0 is time multiplexed. It provides the lower byte
of the 16-bit memory address, and port 2 provides the high byte of the memory address during
the entire read/write memory cycle. If the memory access is for a byte of program code in the
ROM, the PSEN (program store enable) pin will go low to enable the ROM to place a byte of
program code on the data bus. If the access is for a RAM byte, the WR (write) or RD (read)
pins will go low, enabling data to flow between the RAM and the data bus. The ROM may be
expanded to 64K by using a 27512 type EPROM and connecting the remaining port 2 upper
address lines A14-A15 to the chip.
COUNTERS AND TIMERS
Many micro controller applications require the counting of external events, such as the frequency of a
pulse train, or the generation of precise internal time delays between computer actions. Both of these
tasks can be accomplished using software techniques, but software loops for counting or timing keep
the processor occupied so that other, perhaps more important, functions are not done. To relieve the
processor of this burden, two 16-bit up counters, named T0 and T1, are provided for the general use of
the programmer. Each counter may be programmed to count internal clock pulses, acting as a timer,
or programmed to count external pulses as a counter. The counters are divided into two 8-bit registers
called the timer low (TL0, TL1) and high (TH0, TH1). All counter action is controlled by bit states in the
timer mode control register (TMOD), the timer/counter control register (TCON), and certain program
instructions.
SERIAL DATA INPUT/OUTPUT
Computers must be able to communicate with each other in modern multiprocessor distributed
systems. One cost-effective way to communicate is to send and receive data bits serially. The 8051 has
a serial data communication circuit that uses register SBUF to hold data. Register SCON controls data
communication, register PCON controls data rates, and pins RXD (P3.0) and TXD (P3.1) connect to the
serial data network.
SBUF is physically two registers. One is ‘write’ only and is used to hold data to be transmitted
out of the 8051 via TXD. The other is ‘read’ only and holds received data from external sources via RXD.
Both mutually exclusive registers use address 99h. There are four programmable modes for serial data
communication that are chosen by setting the SMX bits in SCON. Baud rates are determined by the mode
chosen.