AUTOMATIC ROOM LIGHT CONTROLLER WITH VISITOR COUNTER
ACKNOWLEDGEMENT
We are greatly thankful to Mr. Rishikesh Kumar for guiding us in
preparing our project titled Microcontroller Based Automatic Room
Light Controller with Visitor Counter .
The guidance was helpful to us in making the project and gaining
practical knowledge on various technical aspects.
We would also like to thank all the faculty members of
Electronics & Communication Engineering department for their
support.
Arvind Kumar Vandita Jaiswal Satish Kumar Avinash Kumar
Sohil
U.C.E.R., GR NOIDA
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AUTOMATIC ROOM LIGHT CONTROLLER WITH VISITOR COUNTER
CERTIFICATE
This is to certify that Mr. Avinash Kumar Sohil, Mr. Arvind
kumar , Mr.Satish kumar and Miss. Vandita Jaiswal; students of
Electronics&Communication Engineering department of United
College of Engineering & Research, Greater Noida (U.P.) which
is affiliated to G.B.Technical University, Lucknow (U.P.) have
worked under my supervision during the session 2010-2011 and the
report submitted by them on the project titled Microcontroller
based automatic room light controller with visitor counter has been
prepared by their own efforts.
With best of my knowledge, they have gained the required
knowledge for the theoretical aspect and have done all the
practical practice, which is required up to this level.
U.C.E.R., GR NOIDA
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PREFACE
Any engineering institute can be successful only when it shows
its willingness and implement new ideas and practice in the field
of technical education. It is necessary for an institute to upgrade
its course content with the changing condition of the market and
the field.
The project to be made is an essential step towards making
future engineers familiar with the practical aspects of their
field. During the project period the engineer is exposed of its
innovativeness and engineering knowledge.
While working on the project, the engineer gets an opportunity
to relate the theoretical knowledge with practical operation. He is
first given a brief overview of the entire setup and then detailed
description of individual unit follows.
We feel privileged to have this opportunity of making this
project at U.C.E.R. In this project report, we have tried to
summarize all our observations, experience and knowledge that we
have gained while working towards completing the project.
U.C.E.R., GR NOIDA
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TABLE OF CONTENTSPAGE NO: CHAPTER-1 1: INTRODUCTION OF PROJECT
2: PROJECT OVERVIWE CHAPTER-2 BLOCK DIAGRAM AND ITS DESCRIPTION 1:
BASIC BLOCK DIAGRAM 2: BLOCK DIAGRAM DISCRIPTION CHAPTER-3
SCHEMATIC DIAGRAM TRANSMISION CIRCUIT RECEIVER CIRCUIT CIRCUIT
DISCRIPTION CHAPTER-4 HARDWARE DESIGN & DESCRIPTION LIST OF
COMPONENT COMPONENT DESCRIPTION 1: MICROCONTROLLER 2: ULN 2003 7805
3: VOLTAGE REGULTAR 4: POWER SUPPLY (24) (39) (42) (44) (20) (23)
(14) (15) (16) (10) (11) (7) (8)
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AUTOMATIC ROOM LIGHT CONTROLLER WITH VISITOR COUNTER5: BRIDGE
RECTIFIER 6: TRANSFORMER (45) (45) (46) (47) (50) (52) (54) (56)
(66)
7: DIODES8: RESISTER 9: CAPECITOR 10: LED 11: BUZZER 555 TIMER
POWER SUPPLY A: TRANSFORMER B: BASIC PART OF TRASFORMER C:
COMPONENT OF TRASFORMER BRIDGE RECTIFIER IR SENSOR 7- SEGMENT
DISPLAY VOLTAGE REGULATOR RELAY CIRCUIT CHAPTER-5 SOFTWARE DESIGN
CHAPTER-6 TESTING AND RESULT CHAPTER-7 FUTURE EXPANSION CHAPTER-8
APPLICATION, ADVANTAGE & DISADVANTAGE CHAPTER-9 BIBLOGRAPHY
(69) (75) (78) (80) (81)
(91)
(94)
(97)
(99)
(102)
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CHAPTER :- 1 Project Overview
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1. Introduction Of Project1.1 Project Definition:
Project title is AUTOMATIC ROOM LIGHT CONTROLLER WITH
BIDIRECTIONAL VISITOR COUNTER .
The objective of this project is to make a controller based
model to count number of persons visiting particular room and
accordingly light up the room. Here we can use sensor and can know
present number of persons.
In todays world, there is a continuous need for automatic
appliances with the increase in standard of living, there is a
sense of urgency for developing circuits that would ease the
complexity of life.
Also if at all one wants to know the number of people present in
room so as not to have congestion. This circuit proves to be
helpful.
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1.2 Project Overview
This Project Automatic Room Light Controller with Visitor
Counter using Microcontroller is a reliable circuit that takes over
the task of controlling the room lights as well us counting number
of persons/ visitors in the room very accurately. When somebody
enters into the room then the counter is incremented by one and the
light in the room will be switched ON and when any one leaves the
room then the counter is decremented by one. The light will be only
switched OFF until all the persons in the room go out. The total
number of persons inside the room is also displayed on the seven
segment displays.
The microcontroller does the above job. It receives the signals
from the sensors, and this signal is operated under the control of
software which is stored in ROM. Microcontroller AT89S52
continuously monitor the Infrared Receivers, When any object pass
through the IR Receiver's then the IR Rays falling on the receiver
are obstructed , this obstruction is sensed by the
Microcontroller
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CHAPTER :- 2 BLOCK DIAGRAM AND ITS DESCRIPTION
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2.1 Basic Block Diagram
EnterEnter Sensor Signal Conditioning
Exit
A T
Relay Driver
Exit Sensor
8Signal Conditioning Power Supply
9 S 5 2
Light
S
Fig. 2.1 Basic Block Diagram
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2.2
Block Diagram DescriptionThe basic block diagram of the
bidirectional visitor counter with automatic light controller is
shown in the above figure. Mainly this block diagram consist of the
following essential blocks. 1. Power Supply 2. Entry and Exit
sensor circuit 3. AT 89S52 micro-controller 4. Relay driver
circuit
1. Power Supply:Here we used +12V and +5V dc power supply. The
main function of this block is to provide the required amount of
voltage to essential circuits. +12 voltage is given. +12V is given
to relay driver. To get the +5V dc power supply we have used here
IC 7805, which provides the +5V dc regulated power supply.
2. Enter and Exit Circuits:This is one of the main part of our
project. The main intention of this block is to sense the person.
For sensing the person and light we are using the light dependent
register (LDR). By using this sensor and its related circuit
diagram we can count the persons.
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3. 89S52 Microcontroller:It is a low-power, high performance
CMOS 8-bit microcontroller with 8KB of Flash Programmable and
Erasable Read Only Memory (PEROM). The device is manufactured using
Atmels high-density nonvolatile memory technology and is compatible
with the MCS-51TM instruction set and pin out. The on-chip Flash
allows the program memory to be reprogrammed in-system or by a
conventional nonvolatile memory programmer. By
combining a versatile 8-bit CPU with Flash on a monolithic hip,
the Atmel AT89S52 is a powerful Microcontroller, which provides a
highly flexible and cost effective solution so many embedded
control applications.
4. Relay Driver Circuit:-
This block has the potential to drive the various controlled
devices. In this block mainly we are using the transistor and the
relays. One relay driver circuit we are using to control the light.
Output signal from AT89S52 is given to the base of the transistor,
which we are further energizing the particular relay. Because of
this appropriate device is selected and it do its allotted
function.
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CHAPTER :- 3 SCHEMATIC DIAGRAM
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Transmission Circuit:-
Fig. 3.1 Transmitter circuit
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Receiver Circuit:-
Fig. 3.2 Receiver circuit
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CIRCUIT DESCRIPTION:There are two main parts of the circuits. 1.
Transmission Circuits (Infrared LEDs) 2. Receiver Circuit
(Sensors)
1. Transmission Circuit:
Fig. 3.3 Transmitter circuit
This circuit diagram shows how a 555 timer IC is configured to
function as a basic monostable multivibrator. A monostable
multivibrator is a timing circuit that changes state once
triggered, but returns to its original state after a certain time
delay. It got its name from the factU.C.E.R., GR NOIDAPage 16
AUTOMATIC ROOM LIGHT CONTROLLER WITH VISITOR COUNTER
that only one of its output states is stable. It is also known
as a 'oneshot'. In this circuit, a negative pulse applied at pin 2
triggers an internal flipflop that turns off pin 7's discharge
transistor, allowing C1 to charge up through R1. At the same time,
the flip-flop brings the output (pin 3) level to 'high'. When
capacitor C1 as charged up to about 2/3 Vcc, the flip-flop is
triggered once again, this time making the pin 3 output 'low' and
turning on pin 7's discharge transistor, which discharges C1 to
ground. This circuit, in effect, produces a pulse at pin 3 whose
width t is just the product of R1 and C1, i.e., t=R1C1. IR
Transmission circuit is used to generate the modulated 36 kHz IR
signal. The IC555 in the transmitter side is to generate 36 kHz
square wave. Adjust the preset in the transmitter to get a 38 kHz
signal at the o/p. around 1.4K we get a 38 kHz signal. Then you
point it over the sensor and its o/p will go low when it senses the
IR signal of 38 kHz.
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2. Receiver Circuit:
Fig. 3.4 Receiver circuit
The IR transmitter will emit modulated 38 kHz IR signal and at
the receiver we use TSOP1738 (Infrared Sensor). The output goes
high when the there is an interruption and it return back to low
after the time period determined by the capacitor and resistor in
the circuit. I.e. around 1 second. CL100 is to trigger the IC555
which is configured as monostable multivibrator. Input is given to
the Port 1 of the microcontroller. Port 0 is used for the 7-Segment
display purpose. Port 2 is used for the Relay Turn On and Turn off
Purpose.LTS 542 (Common Anode) is used for 7-Segment display. And
that time Relay will get Voltage and triggered so light will get
voltage and it will turn on. AndU.C.E.R., GR NOIDAPage 18
AUTOMATIC ROOM LIGHT CONTROLLER WITH VISITOR COUNTER
when counter will be 00 that time Relay will be turned off.
Reset button will reset the microcontroller.
\
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CHAPTER :- 4 HARDWARE DESIGN & DESCRIPTIONS
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Hardware Design:-
Infrared Sensor TSOP1738
Microcontroller AT89S52
7-Segment Timer IC Display 555 Fig. 4.1 Snap of the entire
circuit
Relay
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4.1 Procedure Followed While Designing:
In the beginning I designed the circuit in DIPTRACE software.
Dip trace is a circuit designing software. After completion of the
designing circuit I prepared the layout. Then I programmed the
microcontroller using KEIL software using hex file. Then soldering
process was done. After completion of the soldering process I
tested the circuit. Still the desired output was not obtained and
so troubleshooting was done. In the process of troubleshooting I
found the circuit aptly soldered and connected and hence came to
conclusion that there was error in programming section which was
later rectified and the desired results were obtained.
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4.2 List of Components:
Following is the list of components that are necessary to build
the assembly of the Digital Speedometer Cum Odometer:
Microcontroller AT89S52 IC 7805 Sensor TSOP 1738 (Infrared
Sensor) Transformer 12-0-12, 500 mA Preset 4.7K Disc capacitor
104,33pF Reset button switch Rectifier diode IN4148 Transistor BC
547, CL 100 7-Segment Display
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COMPONENT DESCRIPTION
1)MICRO-CONTROLLER 8051 DESCRIPTIONThe IC 8051 is a low-power;
high-performance CMOS 8-bit microcomputer with 4K bytes of Flash
programmable and erasable read only memory (PEROM). The device is
manufactured using Atmels highdensity nonvolatile memory technology
and is compatible with the industry-standard MCS-51 instruction set
and pin out. The on-chip Flash allows the program memory to be
reprogrammed in-system or by a conventional nonvolatile memory
programmer. By combining a versatile 8-bit CPU with Flash on a
monolithic chip, the Atmel IC 8051 is a powerful microcomputer
which provides a highly-flexible and costeffective solution to many
embedded control applications. The IC 8051 provides the following
standard features: 4K bytes of Flash, 128 bytes of RAM, 32 I/O
lines, two 16-bit timer/counters, a five vector two-level interrupt
architecture, full duplex serial port, on-chip oscillator and clock
circuitry. In addition, the IC 8051 is designed with static logic
for operation down to zero frequency and supports two software
selectable power saving modes. The Idle Mode stops the CPU while
allowing the RAM, timer/counters, serial port and interrupt system
to continue functioning.
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Pin Description of the 8051P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6
P1.7 RST (RXD)P3.0 (TXD)P3.1 (INT0)P3.2 (INT1)P3.3 (T0)P3.4
(T1)P3.5 (WR)P3.6 (RD)P3.7 XTAL2 XTAL1 GND 1 2 3 4 5 6 7 8 9 10 11
12 13 14 15 16 17 18 19 20 40 39 38 37 36 35 34 33 32 31 30 29 28
27 26 25 24 23 22 21
8051 (8031)
Vcc P0.0(AD0) P0.1(AD1) P0.2(AD2) P0.3(AD3) P0.4(AD4) P0.5(AD5)
P0.6(AD6) P0.7(AD7) EA/VPP ALE/PROG PSEN P2.7(A15) P2.6(A14)
P2.5(A13) P2.4(A12) P2.3(A11) P2.2(A10) P2.1(A9) P2.0(A8)
Figure No. 1.1: Pin Diagram of 8051
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PROCESSORA processor is an electronic device capable of
manipulating data in a way specified by a sequence of
instructions.
INSTRUCTIONSInstructions in a computer are binary numbers just
like data. Different numbers, when read and executed by a
processor, cause different things to happen. The instructions are
also called opcodes or machine codes. Different bit patterns
activate or deactivate different parts of the processing core.
Every processor has its own instruction set varying in number, bit
pattern and functionality.
PROGRAMThe sequence of instructions is what constitutes a
program. The sequence of instructions may be altered to suit the
application.
ASSEMBLY LANGUAGEWriting and understanding such programs in
binary or hexadecimal form is very difficult ,so each instructions
is given a symbolic notation in English language called as
mnemonics. A program written in mnemonics Form is called an
assembly language program. But it must be converted into machine
language for execution by processor.
ASSEMBLERAn assembly language program should be converted to
machine language for execution by processor. Special software
called ASSEMBLER
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converts a program written in mnemonics to its equivalent
machine opcodes.
HIGH LEVEL LANGUAGEA high level language like C may be used to
write programs for processors. Software called compiler converts
this high level language program down to machine code. Ease of
programming and portability.
PIN DESCRIPTIONVCC (Pin 40) Provides voltage to the chip . +5V
GND (Pin 20) Ground XTAL1 (Pin 19) and XTAL2 (Pin 18) Crystal
Oscillator connected to pins 18, 19.Two capacitors of 30pF value.
Time for one machine cycle:11.0592/12=1.085 secs
RST (Pin 9) RESET pin
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1.Active high. On applying a high pulse to this pin,
microcontroller will reset and terminate all activities. 2.INPUT
pin 3.Minimum 2 machine cycles required to make RESET 4.Value of
registers after RESET
External Access: EA 31Connected to VCC for on chip ROM Connected
to Ground for external ROM containing the code Input Pin
Program Store Enable: PSEN 29Output Pin In case of external ROM
with code it is connected to the OE pin of the ROM
Address Latch Enable: ALE 30 Output Pin. Active high In case of
external ROM ,ALE is used to de multiplex (PORT 0) the address and
data bus by connecting to the G pin of 74LS373 chip
I/O Port Pins and their Functions:Four ports P0,P1,P2,P3 with 8
pins each, making a total of 32 input/output pins
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On RESET all ports are configured as output. They need to be
programmed to make them function as inputs
PORT 0Pins 32-39 Can be used as both Input or Output External
pull up resistors of 10K need to be connected Dual role: 8051
multiplexes address and data through port 0 to save pins .AD0-AD7
ALE is used to de multiplex data and address bus
PORT 1Pins 1 through 8 Both input or output No dual function
Internal pull up registers On RESET configured as output
PORT 2Pins 21 through 28 No external pull up resistor required
Both input or output Dual Function: Along with Port 0 used to
provide the 16-Bit address for external memory. It provides higher
address A8-A16U.C.E.R., GR NOIDA
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PORT 3Pins 10 through 17 No external pull up resistors
required
PROCESSOR ARCHITECTURE
Block DiagramExternal interrupts Interrupt Control On-chip ROM
for program codeTimer/Counter
On-chip RAM
Timer 1 Timer 0
Counter Inputs
CPU Serial Port
OSC
Bus Control
4 I/O Ports
P0 P1 P2 P3
TxD RxD
Address/Data
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Figure No. 1.3: Block Diagram of Microcontroller
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ALUThe Arithmetic Logic Unit (ALU) performs the internal
arithmetic manipulation of data line processor. The instructions
read and executed by the processor decide the operations performed
by the ALU and also control the flow of data between registers and
ALU. Operations performed by the ALU are Addition , Subtraction ,
Not , AND , NAND , OR , NOR , XOR , Shift Left/Right , Rotate
Left/right , Compare etc. Some ALU supports Multiplication and
Division. Operands are generally transferred from two registers or
from one register and memory location to ALU data inputs. The
result of the operation is the placed back into a given destination
register or memory location from ALU output.
REGISTERSRegisters are the internal storage for the processor.
The number of registers varies significantly between processor
architectures. WORKING REGISTERS Temporary storage during ALU
Operations and data transfers. INDEX REGISTERS Points to memory
addresses.
STATUS REGISTERSStores the current status of various flags
denoting conditions resulting from various operations.
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CONTROL REGISTERSContains configuration bits that affect
processor operation and the operating modes of various internal
subsystems.
Memory OrganizationProgram Memory
Data MemoryThe right half of the internal and external data
memory spaces available on Atmels Flash microcontrollers. Hardware
configuration for accessing up to 2K bytes of external RAM. In this
case, the CPU executes from internal Flash. Port 0 serves as a
multiplexed address/data bus to the RAM, and 3 lines of Port 2 are
used to page the RAM. The CPU generates RD and WR signals as needed
during external RAM accesses. You can assign up to 64K bytes of
external data memory. External data memory addresses can be either
1 or 2 bytes wide. One-byte addresses are often used in conjunction
with one or more other I/O lines to page the RAM. Two-byte
addresses can also be used, in which case the high address byte is
emitted at Port 2. Internal data memory addresses are always 1 byte
wide, which implies an address space of only 256 bytes. However,
the addressing modes for internal RAM can in fact accommodate 384
bytes. Direct addresses higher than 7FH access one memory space,
and indirect addresses higher than 7FH access a differentU.C.E.R.,
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memory space. Thus, the Upper 128 and SFR space occupying the
same block of addresses, 80H through FFH, although they are
physically separate entities. The lowest 32 bytes are grouped into
4 banks of 8 registers. Program instructions call out these
registers as R0 through R7. Two bits in the Program Status Word
(PSW) select which register bank is in use. This architecture
allows more efficient use of code space, since register
instructions are shorter than instructions that use direct
addressing.
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Programming Status Word:
The Instruction SetAll members of the Atmel microcontroller
family execute the same instruction set. This instruction set is
optimized for 8- bit control applications and it provides a variety
of fast addressing modes for accessing the internal RAM to
facilitate byte operations on small data structures. The
instruction set provides extensive support for 1-bit variables as a
separate data type, allowing direct bit manipulation in control and
logic systems that require Boolean processing. The following
overview of the instruction set gives a brief description of how
certain instructions can be used.
Program Status WordThe Program Status Word (PSW) contains status
bits that reflect the current state of the CPU. The PSW, shown in
Figure 11, resides in SFR space. The PSW contains the Carry bit,
the Auxiliary Carry (for BCD operations), the tworegister bank
select bits, the Overflow flag, a Parity bit, and two
user-definable status flags. The Carry bit, in addition to serving
as a Carry bit in arithmetic operations, also serves as the
Accumulator for a number of Boolean operations.
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The bits RS0 and RS1 select one of the four register banks shown
in Figure 8. A number of instructions refer to these RAM locations
as R0 through R7. The status of the RS0 and RS1 bits at execution
time determines which of the four banks is selected. The Parity bit
reflects the number of 1s in the Accumulator: P=1 if the
Accumulator contains an odd number of 1s, and P=0 if the
Accumulator contains an even number of 1s. Thus, the number of 1s
in the Accumulator plus P is always even. Two bits in the PSW are
uncommitted and can be used as general purpose status flags.
Addressing ModesThe addressing modes in the Flash
microcontroller instruction set are as follows.
Direct AddressingIn direct addressing, the operand is specified
by an 8-bit address field in the instruction. Only internal data
RAM and SFRs can be directly addressed.
Indirect AddressingIn indirect addressing, the instruction
specifies a register that contains the address of the operand. Both
internal and external RAM can be indirectly addressed. The address
register for 8-bit addresses can be either the Stack Pointer or R0
or R1 of the selected register bank. The address register for
16-bit addresses can be only the 16-bit data pointer register,
DPTR.
Register InstructionsThe register banks, which contain registers
R0 through R7, can be accessed by instructions whose opcodes carry
a 3- bit register specification. Instructions that access the
registers this way make efficient use of code, since this mode
eliminates an address byte. When theU.C.E.R., GR NOIDAPage 36
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instruction is executed, one of the eight registers in the
selected bank is accessed. One of four banks is selected at
execution time by the two bank select bits in the PSW.
Register-Specific InstructionsSome instructions are specific to
a certain register. For example, some instructions always operate
on the Accumulator, so no address byte is needed to point to it. In
these cases, the opcode itself points to the correct register.
Instructions that refer to the Accumulator as A assemble as
Accumulator-specific opcodes.
Indexed AddressingProgram memory can only be accessed via
indexed addressing. This addressing mode is intended for reading
look-up tables in program memory. A 16-bit base register (either
DPTR or the Program Counter) points to the base of the table, and
the Accumulator is set up with the table entry number. The address
of the table entry in program memory is formed by adding the
Accumulator data to the base pointer. Another type of indexed
addressing is used in the case jump instruction. In this case the
dest ination address of a jump instruction is computed as the sum
of the base pointer and the Accumulator data.
SRAMVolatile, fast, low capacity, expensive, requires lesser
external support circuitry.
DRAMVolatile, relatively slow, highest capacity needs continuous
refreshing. Hence require external circuitry.
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OTP ROMOne time programmable, used for shipping in final
products.
EPROMErasable programmable, UV Erasing, Used for system
development and debugging.
EEPROMElectrically erasable and programmable, can be erased
programmed in- circuit, Used for storing system parameters.
FLASHElectrically programmable & erasable, large capacity,
organized as sectors.
BUSESA bus is a physical group of signal lines that have a
related function. Buses allow for the transfer of electrical
signals between different parts of the processor
Processor buses are of three types: Data busAddress bus Control
bus
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CONTROLLER LOGICProcessor brain decodes instructions and
generate control signal for various sub units. It has full control
over the clock distribution unit of processor.
I/O PeripheralsThe I/O devices are used by the processor to
communicate with the external world Parallel Ports. Serial Ports.
ADC/DAC.
2)ULN 2003 7805
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Figure No. 1.4: ULN 2003
FEATURES- Output current 500mA per driver (600mA peak) - Output
voltage 50V Integrated suppression diodes for inductive loads -
Outputs can be paralleled for higher current - TTL/CMOS/PMOS/DTL
Compatible inputs - Inputs pinned opposite outputs to simplify
Layout
DESCRIPTIONThe ULN2001, ULN2002, ULN2003 and ULN2004 are high
voltage, high current Darlington Arrays each contain seven open
collector Darlington pairs with common emitters. Each Channel rated
at 500mA and can withstand peak currents of 600mA. Suppression
diodes are Included for inductive load driving and the inputs are
pinned opposite the outputs to simplify board
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MAXIMUM RATING Table No. 1.2: Maximum Rating of ULN Table :-1
Absolute max ratings Symbol V Vi Ic Ib Ta Parameter Output voltage
Input voltage Countinuous collector current Countinuous base
current Operating ambient tempreture range Storage tempreture range
Junction tempreture Value 50 30 500 25 -20 - 85 Unit V V Ma Ma
Tstg
-55 - 155
Tj
150
U.C.E.R., GR NOIDA
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Table :-2 Thermal Data Symbol R th.ra Parameter Thermal
resistance junction ambient - max Dip -16 70 So -16 120 Unit
C/w
WHY WE USE ULN 2003?Digital system and microcontroller pins lack
sufficient current to drive the relay.
(3)VOLTAGE REGULATORVoltage regulator ICs are available with
fixed (typically 5, 12 and 15V) or variable output voltages. The
maximum current they can pass also rates them. Negative voltage
regulators are available, mainly for use in dual supplies. Most
regulators include some automatic protection from excessive current
(over load protection) and overheating (thermal protection). Many
of fixed voltage regulator ICs has 3 leads. They include a hole for
attaching a heat sink if necessary.
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Figure No. 1.5: 7805 Voltage Regulator
DESCRIPTIONThese voltage regulators are monolithic circuit
integrated circuit designed as fixed voltage regulators for a wide
variety of applications including local, on card regulation. These
regulators employ internal current limiting, thermal shutdown, and
safe-area compensation. With adequate heat sinking they can deliver
output current in excess of 1.0 A. Although designed primarily as a
fixed voltage regulator, these devices can be used with external
components to obtain adjustable voltage and current.U.C.E.R., GR
NOIDAPage 43
AUTOMATIC ROOM LIGHT CONTROLLER WITH VISITOR COUNTER
FEATURES Output current in Excess of 1.0 ANo external component
required Internal thermal overload protection Internal short
circuit current limiting Output transistor safe-area compensation
Output voltage offered in 2% and 4% tolerance Available I n surface
mount D2PAK and standard 3-lead transistor packages Previous
commercial temperature range has been extended to a junction
temperature range of -40 degree C to +125 degree C.
(4)POWER SUPPLY
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(5) BRIDGE RECTIFIERBridge rectifier circuit consists of four
diodes arranged in the form of a bridge as shown in figure.
OPERATIONDuring the positive half cycle of the input supply, the
upper end A of the transformer secondary becomes positive with
respect to its lower point B. This makes Point1 of bridge Positive
with respect to point 2. The diode D1 & D2 become forward
biased & D3 & D4 become reverse biased. As a result a
current starts flowing from point1, through D1 the load & D2 to
the negative end. During negative half cycle, the point2 becomes
positive with respect to point1. Diodes D1 & D2 now become
reverse biased. Thus a current flow from point 2 to point1.
(6)TRANSFORMERTransformer is a major class of coils having two
or more windings usually wrapped around a common core made from
laminated iron sheets. It has two cols
U.C.E.R., GR NOIDA
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named primary and secondary. If the current flowing through
primary is fluctuating, then a current will be inducted into the
secondary winding. A steady current will not be transferred from
one coil to other coil.
Transformers are of two types:1.Step up transformer 2.Step down
transformer In the power supply we use step down transformer. We
apply 220V AC on the primary of step down transformer. This
transformer step down this voltages to 6V AC. We Give 6V AC to
rectifier circuit, which convert it to 5V DC.
(7)DIODEThe diode is a p-n junction device. Diode is the
component used to control the flow of the current in any one
direction. The diode widely works in forward bias.
U.C.E.R., GR NOIDA
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Diode When the current flows from the P to N direction. Then it
is in forward bias. The Zener diode is used in reverse bias
function i.e. N to P direction. Visually the identification of the
diode`s terminal can be done by identifying he silver/black line.
The silver/black line is the negative terminal (cathode) and the
other terminal is the positive terminal (cathode).
APPLICATIONDiodes: Rectification, free-wheeling, etc Zener
diode: Voltage control, regulator etc. Tunnel diode: Control the
current flow, snobbier circuit, etc
(8)RESISTORSThe flow of charge through any material encounters
an opposing force similar in many respects to mechanical friction
.this opposing force is called resistance of the material .in some
electric circuit resistance is deliberately introduced in form of
resistor. Resistor used fall in three categories , only two of
which are color coded which are metal film and carbon film resistor
.the third category is the wire wound type ,where value are
generally printed on the vitreous paint finish of the component.
Resistors are in ohms and are represented in Greek letter omega,
looks as an upturned horseshoe. Most electronic circuit require
resistors to make them work properly and it is obliviously
important to find out something about the different types of
resistors available. Resistance is measured in ohms, the
U.C.E.R., GR NOIDA
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symbol for ohm is an omega ohm. 1 ohm is quite small for
electronics so resistances are often given in kohm and Mohm.
Resistors used in electronics can have resistances as low as 0.1
ohm or as high as 10 Mohm.
FUNCTIONResistor restrict the flow of electric current, for
example a resistor is placed in series with a light-emitting
diode(LED) to limit the current passing through the LED.
TYPES OF RESISTORS FIXED VALUE RESISTORSIt includes two types of
resistors as carbon film and metal film .These two types are
explained under
1. CARBON FILM RESISTORSDuring manufacture, at in film of carbon
is deposited onto a small ceramic rod. The resistive coating is
spiraled away in an automatic machine until the resistance between
there two ends of the rods is as close as possible to the correct
value. Metal leads and end caps are added, the resistors is covered
with an insulating coating and finally painted with colored bands
to indicate the resistor value
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Figure No. 1.15: Carbon Film ResistorsAnother example for a
Carbon 22000 Ohms or 22 Kilo-Ohms also known as 22K at 5%
tolerance: Band 1 = Red, 1st digit Band 2 = Red, 2nd digit Band 3 =
Orange, 3rd digit, multiply with zeros, in this case 3 zero's Band
4 = Gold, Tolerance, 5%
2.METAL FILM RESISTORSMetal film and metal oxides resistors are
made in a similar way, but can be made more accurately to within 2%
or 1% of their nominal vale there are some difference in
performance between these resistor types, but none which affects
their use in simple circuit.
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3.WIRE WOUND RESISTORA wire wound resistor is made of metal
resistance wire, and because of this, they can be manufactured to
precise values. Also, high wattage resistors can be made by using a
thick wire material. Wire wound resistors cannot be used for high
frequency circuits. Coils are used in high frequency circuit. Wire
wound resistors in a ceramic case, strengthened with special
cement. They have very high power rating, from 1 or 2 watts to
dozens of watts. These resistors can become extremely hot when used
for high power application, and this must be taken into account
when designing the circuit.
TESTINGResistors are checked with an ohm meter/millimeter. For a
defective resistor the ohm-meter shows infinite high reading.
(9)CAPACITORSIn a way, a capacitor is a little like a battery.
Although they work in completely different ways, capacitors and
batteries both store electrical energy. If you have read How
Batteries Work , then you know that a battery has two terminals.
Inside the battery, chemical reactions produce electrons on one
terminal and absorb electrons at the other terminal.
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BASICLike a battery, a capacitor has two terminals. Inside the
capacitor, the terminals connect to two metal plates separated by a
dielectric. The dielectric can be air, paper, plastic or anything
else that does not conduct electricity and keeps the plates from
touching each other. You can easily make a capacitor from two
pieces of aluminum foil and a piece of paper. It won't be a
particularly good capacitor in terms of its storage capacity, but
it will work. In an electronic circuit, a capacitor is shown like
this:
Figure No. 1.17: Symbol of Capacitor
When you connect a capacitor to a battery, heres what
happens:
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The plate on the capacitor that attaches to the negative
terminal of the battery accepts electrons that the battery is
producing. The plate on the capacitor that attaches to the positive
terminal of the battery loses electrons to the battery.
TESTINGTo test the capacitors, either analog meters or specia l
digital meters with the specified function are used. The
non-electrolyte capacitor can be tested by using the digital meter.
Multi meter mode : Continuity Positive probe : One end Negative
probe : Second end Display : `0`(beep sound occur) `OL` Result :
Faulty OK
(10)LEDLED falls within the family of P-N junction devices. The
light emitting diode (LED) is a diode that will give off visible
light when it is energized. In any forward biased P-N junction
there is, with in the structure and primarily close to the
junction, a recombination of hole and electrons. This recombination
requires that the energy possessed by the unbound free electron be
transferred to another state. The process of giving off light by
applying an electrical source is called
electroluminescence.U.C.E.R., GR NOIDAPage 52
AUTOMATIC ROOM LIGHT CONTROLLER WITH VISITOR COUNTER
LED is a component used for indication. All the functions being
carried out are displayed by led .The LED is diode which glows when
the current is being flown through it in forward bias condition.
The LEDs are available in the round shell and also in the flat
shells. The positive leg is longer than negative leg.
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(11)BUZZERBuzzer is a device used for beep signal. This will
help us to make understand information or message. A buzzer is
usually electronic device used in automobiles, household
applications etc.
It mostly consists of switches or sensors connected to a control
unit that determines if and which button was pushed or a preset
time has lapsed, and usually illuminates a light on appropriate
button or control panel, and sounds a warning in the form of a
continuous or intermittent buzzing or beeping sound. Initially this
device was based on an electromechanical system which was identical
to an electrical bell without the metal gong. Often these units
were anchored to a wall or ceiling and used the ceiling or wall as
a sounding board. Another implementation with some AC-connected
devices was to implement a circuit to make the AC current into a
noise loud enough to derive a loudspeaker and hook this circuit to
a cheap 8-ohm speaker. These buzzers do not make a sound or turn on
a light, they stop a nearby digital clock, briefly fire two smoke
cannons on each side of the stage exit and open the exit. However,
at the end of the Heartbreaker in Viking, the buzzer is replaced
with a sword that, when removed, causes two
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contacts to touch, closing the circuit and causing the latter
two actions above to occur.
U.C.E.R., GR NOIDA
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555 TIMER
Definition of Pin Functions
Refer to the internal 555 schematic of Fig. 1
Pin 1 (Ground): The ground (or common) pin is the most-negative
supplypotential of the device, which is normally connected to
circuit common (ground) when operated from positive supply
voltages.
Pin 2 (Trigger): This pin is the input to the lower comparator
and is used to setU.C.E.R., GR NOIDAPage 56
AUTOMATIC ROOM LIGHT CONTROLLER WITH VISITOR COUNTER
the latch, which in turn causes the output to go high. This is
the beginning of the timing sequence in monostable operation.
Triggering is accomplished by taking the pin from above to below a
voltage level of 1/3 V+ (or, in general, one-half the voltage
appearing at pin 5). The action of the trigger input is
level-sensitive, allowing slow rate-of-change waveforms, as well as
pulses, to be used as trigger sources. The trigger pulse must be of
shorter duration than the time interval determined by the external
R and C. If this pin is held low longer than that, the output will
remain high until the trigger input is driven high again. One
precaution that should be observed with the trigger input signal is
that it must not remain lower than 1/3 V+ for a period of time
longer than the timing cycle. If this is allowed to happen, the
timer will re-trigger itself upon termination of the first output
pulse. Thus, when the timer is driven in the monostable mode with
input pulses longer than the desired output pulse width, the input
trigger should effectively be shortened by differentiation. The
minimum-allowable pulse width for triggering is somewhat dependent
upon pulse level, but in general if it is greater than the 1uS
(micro-Second), triggering will be reliable. A second precaution
with respect to the trigger input concerns storage time in the
lower comparator. This portion of the circuit can exhibit normal
turn-off delays of several microseconds after triggering; that is,
the latch can still have a trigger
U.C.E.R., GR NOIDA
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input for this period of time after the trigger pulse. In
practice, this means the minimum monostable output pulse width
should be in the order of 10uS to prevent possible double
triggering due to this effect. The voltage range that can safely be
applied to the trigger pin is between V+ and ground. A dc current,
termed the trigger current, must also flow from this terminal into
the external circuit. This current is typically 500nA (nano-amp)
and will define the upper limit of resistance allowable from pin 2
to ground. For an astable configuration operating at V+ = 5 volts,
this resistance is 3 Mega-ohm; it can be greater for higher V+
levels.
Pin 3 (Output): The output of the 555 comes from a high-current
totem-polestage made up of transistors Q20 - Q24. Transistors Q21
and Q22 provide drive for source-type loads, and their Darlington
connection provides a high-state output voltage about 1.7 volts
less than the V+ supply level used. Transistor Q24 provides
current-sinking capability for low-state loads referred to V+ (such
as typical TTL inputs). Transistor Q24 has a low saturation
voltage, which allows it to interface directly, with good noise
margin, when driving current-sinking logic. Exact output saturation
levels vary markedly with supply voltage, however, for both high
and low states. At a V+ of 5 volts, for instance, the low state
Vce(sat) isU.C.E.R., GR NOIDAPage 58
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typically 0.25 volts at 5 mA. Operating at 15 volts, however, it
can sink 200mA if an output-low voltage level of 2 volts is
allowable (power dissipation should be considered in such a case,
of course). High-state level is typically 3.3 volts at V+ = 5
volts; 13.3 volts at V+ = 15 volts. Both the rise and fall times of
the output waveform are quite fast, typical switching times being
100nS. The state of the output pin will always reflect the inverse
of the logic state of the latch. Since the latch itself is not
directly accessible, this relationship may be best explained in
terms of latch-input trigger conditions. To trigger the output to a
high condition, the trigger input is momentarily taken from a
higher to a lower level. [see "Pin 2 Trigger"]. This causes the
latch to be set and the output to go high. Actuation of the lower
comparator is the only manner in which the output can be placed in
the high state. The output can be returned to a low state by
causing the threshold to go from a lower to a higher level [see
"Pin 6 - Threshold"], which resets the latch. The output can also
be made to go low by taking the reset to a low state near ground
[see "Pin 4 - Reset"]. The output voltage available at this pin is
approximately equal to the Vcc applied to pin 8 minus 1.7V.
Pin 4 (Reset): This pin is also used to reset the latch and
return the output to alow state. The reset voltage threshold level
is 0.7 volt, and a sink current of 0.1mAU.C.E.R., GR NOIDAPage
59
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from this pin is required to reset the device. These levels are
relatively independent of operating V+ level; thus the reset input
is TTL compatible for any supply voltage. The reset input is an
overriding function; that is, it will force the output to a low
state regardless of the state of either of the other inputs. It may
thus be used to terminate an output pulse prematurely, to gate
oscillations from "on" to "off", etc. Delay time from reset to
output is typically on the order of 0.5 S, and the minimum reset
pulse width is 0.5 S. Neither of these figures is guaranteed,
however, and may vary from one manufacturer to another. In short,
the reset pin is used to reset the flip-flop that controls the
state of output pin 3. The pin is activated when a voltage level
anywhere between 0 and 0.4 volt is applied to the pin. The reset
pin will force the output to go low no matter what state the other
inputs to the flip-flop are in. When not used, it is recommended
that the reset input be tied to V+ to avoid any possibility of
false resetting.
Pin 5 (Control Voltage): This pin allows direct access to the
2/3 V+ voltagedivider point, the reference level for the upper
comparator. It also allows indirect access to the lower comparator,
as there is a 2:1 divider (R8 - R9) from this point to the
lower-comparator reference input, Q13. Use of this terminal is the
option of the user, but it does allow extreme flexibility by
permitting modification of theU.C.E.R., GR NOIDAPage 60
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timing period, resetting of the comparator, etc. When the 555
timer is used in a voltage-controlled mode, its voltage-controlled
operation ranges from about 1 volt less than V+ down to within 2
volts of ground (although this is not guaranteed). Voltages can be
safely applied outside these limits, but they should be confined
within the limits of V+ and ground for reliability. By applying a
voltage to this pin, it is possible to vary the timing of the
device independently of the RC network. The control voltage may be
varied from 45 to 90% of the Vcc in the monostable mode, making it
possible to control the width of the output pulse independently of
RC. When it is used in the astable mode, the control voltage can be
varied from 1.7V to the full Vcc. Varying the voltage in the
astable mode will produce a frequency modulated (FM) output. In the
event the control-voltage pin is not used, it is recommended that
it be bypassed, to ground, with a capacitor of about 0.01uF (10nF)
for immunity to noise, since it is a comparator input. This fact is
not obvious in many 555 circuits since I have seen many circuits
with 'no-pin-5' connected to anything, but this is the proper
procedure. The small ceramic cap may eliminate false
triggering.
U.C.E.R., GR NOIDA
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Pin 6 (Threshold): Pin 6 is one input to the upper comparator
(the other beingpin 5) and is used to reset the latch, which causes
the output to go low. Resetting via this terminal is accomplished
by taking the terminal from below to above a voltage level of 2/3
V+ (the normal voltage on pin 5). The action of the threshold pin
is level sensitive, allowing slow rate-of-change waveforms. The
voltage range that can safely be applied to the threshold pin is
between V+ and ground. A dc current, termed the threshold current,
must also flow into this terminal from the external circuit. This
current is typically 0.1A, and will define the upper limit of total
resistance allowable from pin 6 to V+. For either timing
configuration operating at V+ = 5 volts, this resistance is 16
Mega-ohm. For 15 volt operation, the maximum value of resistance is
20 MegaOhms.
Pin 7 (Discharge): This pin is connected to the open collector
of a npntransistor (Q14), the emitter of which goes to ground, so
that when the transistor is turned "on", pin 7 is effectively
shorted to ground. Usually the timing capacitor is connected
between pin 7 and ground and is discharged when the transistor
turns "on". The conduction state of this transistor is identical in
timing to that of the output stage. It is "on" (low resistance to
ground) when the output is low and "off" (high resistance to
ground) when the output is high. In both the monostableU.C.E.R., GR
NOIDAPage 62
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and astable time modes, this transistor switch is used to clamp
the appropriate nodes of the timing network to ground. Saturation
voltage is typically below 100mV (milli-Volt) for currents of 5 mA
or less, and off-state leakage is about 20nA (these parameters are
not specified by all manufacturers, however). Maximum collector
current is internally limited by design, thereby removing
restrictions on capacitor size due to peak pulse-current discharge.
In certain applications, this open collector output can be used as
an auxiliary output terminal, with current-sinking capability
similar to the output (pin 3).
Pin 8 (V +): The V+ pin (also referred to as Vcc) is the
positive supply voltageterminal of the 555 timer IC. Supply-voltage
operating range for the 555 is +4.5 volts (minimum) to +16 volts
(maximum), and it is specified for operation between +5 volts and
+15 volts.
U.C.E.R., GR NOIDA
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The buffer circuit's input has a very high impedance (about 1M )
so it requires only a few A, but the output can sink or source up
to 200mA. This enables a high impedance signal source (such as an
LDR) to switch a low impedance output transducer (such as a lamp).
It is an inverting buffer or NOT gate because the output logic
state (low/high) is the inverse of the input state: Input low (<
1/3 Vs) makes output high, +Vs Input high (> 2/3 Vs) makes
output low, 0V
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When the input voltage is between 1/3 and 2/3 Vs the output
remains in its present state. This intermediate input region is a
deadspace where there is no response, a property called hysteresis,
it is like backlash in a mechanical linkage. This type of circuit
is called a Schmitt trigger. If high sensitivity is required the
hysteresis is a problem, but in many circuits it is a helpful
property. It gives the input a high immunity to noise because once
the circuit output has switched high or low the input must change
back by at least 1 /3 Vs to make the output switch back.
Fig: IR Sensor Circuit.U.C.E.R., GR NOIDAPage 65
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POWER SUPPLY:
A: TRANSFORMER:A transformer is a device that transfers
electrical energy from one circuit to another through inductively
coupled conductors the transformer's coils or "windings". Except
for air-core transformers, the conductors are commonly wound around
a single iron-rich core, or around separate but magneticallycoupled
cores. A varying current in the first or "primary" winding creates
a varying magnetic field in the core (or cores) of the transformer.
This varying magnetic field induces a varying electromotive force
(EMF) or "voltage" in the "secondary" winding. This effect is
called mutual induction.
If a load is connected to the secondary circuit, electric charge
will flow in the secondary winding of the transformer and transfer
energy from the primary circuit to the load connected in the
secondary circuit.
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The secondary induced voltage VS, of an ideal transformer, is
scaled from the primary VP by a factor equal to the ratio of the
number of turns of wire in their respective windings:
By appropriate selection of the numbers of turns, a transformer
thus allows an alternating voltage to be stepped up by making NS
more than NP or stepped down, by making it
B: BASIC PARTS OF A TRANSFORMER :In its most basic form a
transformer consists of: A primary coil or winding. A secondary
coil or winding. A core that supports the coils or windings. Refer
to the transformer circuit in figure as you read the following
explanation: The primary winding is connected to a 60-hertz ac
voltage source. The magnetic field (flux) builds up (expands) and
collapses (contracts) about the primary winding. The expanding and
contracting magnetic field around the primary winding cuts the
secondary winding and induces an alternating voltage into the
winding. This voltage causes alternating current to flow through
the load. The voltage may be stepped up or down depending on the
design of the primary and secondary windings.U.C.E.R., GR NOIDAPage
67
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C: THE COMPONENTS OF A TRANSFORMER :Two coils of wire (called
windings) are wound on some type of core material. In some cases
the coils of wire are wound on a cylindrical or rectangular
cardboard form. In effect, the core material is air and the
transformer is called an AIR-CORE TRANSFORMER. Transformers used at
low frequencies, such as 60 hertz and 400 hertz, require a core of
low-reluctance magnetic material, usually iron. This type of
transformer is called an IRON-CORE TRANSFORMER. Most power
transformers are of the iron-core type. The principle parts of a
transformer and their functions are:
The CORE, which provides a path for the magnetic lines of flux.
The PRIMARY WINDING, which receives energy from the ac source.
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The SECONDARY WINDING, which receives energy from the primary
winding and delivers it to the load.
The ENCLOSURE, which protects the above components from dirt,
moisture, and mechanical damage.
BRIDGE RECTIFIERA bridge rectifier makes use of four diodes in a
bridge arrangement to achieve full-wave rectification. This is a
widely used configuration, both with individual diodes wired as
shown and with single component bridges where the diode bridge is
wired internally.
A: Basic operation :According to the conventional model of
current flow originally established by Benjamin Franklin and still
followed by most engineers today, current is assumed to flow
through electrical conductors from the positive to the negative
pole. In actuality, free electrons in a conductor nearly always
flow from the negative to the positive pole. In the vast majority
of applications, however, the actual direction of current flow is
irrelevant. Therefore, in the discussion below the conventional
model is retained.In the diagrams below, when the input connected
to the left corner of the diamond is positive, and the input
connected to the right corner is negative, current flows from the
upper supply terminal to the right along the red (positive) path to
the output, and returns to the lower supply terminal via the blue
(negative) path.U.C.E.R., GR NOIDAPage 69
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When the input connected to the left corner is negative, and the
input connected to the right corner is positive, current flows from
the lower supply terminal to the right along the red path to the
output, and returns to the upper supply terminal via the blue
path.
In each case, the upper right output remains positive and lower
right output negative. Since this is true whether the input is AC
or DC, this circuit not only produces a DC output from an AC input,
it can also provide what is sometimes called "reverse polarity
protection". That is, it permits normal functioning of DCpowered
equipment when batteries have been installed backwards, or when
the
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leads (wires) from a DC power source have been reversed, and
protects the equipment from potential damage caused by reverse
polarity.Prior to availability of integrated electronics, such a
bridge rectifier was always constructed from discrete components.
Since about 1950, a single four-terminal component containing the
four diodes connected in the bridge configuration became a standard
commercial component and is now available with various voltage and
current ratings.
B: OUTPUT SMOOTHINGO :For many applications, especially with
single phase AC where the full-wave bridge serves to convert an AC
input into a DC output, the addition of a capacitor may be desired
because the bridge alone supplies an output of fixed polarity but
continuously varying or "pulsating" magnitude (see diagram
above).
The function of this capacitor, known as a reservoir capacitor
(or smoothing capacitor) is to lessen the variation in (or
'smooth') the rectified AC output voltage waveform from the bridge.
One explanation of 'smoothing' is that the capacitor provides a low
impedance path to the AC component of the output, reducing
theU.C.E.R., GR NOIDAPage 71
AUTOMATIC ROOM LIGHT CONTROLLER WITH VISITOR COUNTER
AC voltage across, and AC current through, the resistive load.
In less technical terms, any drop in the output voltage and current
of the bridge tends to be canceled by loss of charge in the
capacitor. This charge flows out as additional current through the
load. Thus the change of load current and voltage is reduced
relative to what would occur without the capacitor. Increases of
voltage correspondingly store excess charge in the capacitor, thus
moderating the change in output voltage / current. The simplified
circuit shown has a well-deserved reputation for being dangerous,
because, in some applications, the capacitor can retain a lethal
charge after the AC power source is removed. If supplying a
dangerous voltage, a practical circuit should include a reliable
way to safely discharge the capacitor. If the normal load cannot be
guaranteed to perform this function, perhaps because it can be
disconnected, the circuit should include a bleeder resistor
connected as close as practical across the capacitor. This resistor
should consume a current large enough to discharge the capacitor in
a reasonable time, but small enough to minimize unnecessary power
waste. Because a bleeder sets a minimum current drain, the
regulation of the circuit, defined as percentage voltage change
from minimum to maximum load, is improved. However in many cases
the improvement is of insignificant magnitude. The capacitor and
the load resistance have a typical time constant = RC where C and R
are the capacitance and load resistance respectively. As long as
the load resistor is large enough so that this time constant is
much longer than the time of
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one ripple cycle, the above configuration will produce a
smoothed DC voltage across the load. In some designs, a series
resistor at the load side of the capacitor is added. The smoothing
can then be improved by adding additional stages of
capacitorresistor pairs, often done only for sub-supplies to
critical high-gain circuits that tend to be sensitive to supply
voltage noise. The idealized waveforms shown above are seen for
both voltage and current when the load on the bridge is resistive.
When the load includes a smoothing capacitor, both the voltage and
the current waveforms will be greatly changed. While the voltage is
smoothed, as described above, current will flow through the bridge
only during the time when the input voltage is greater than the
capacitor voltage. For example, if the load draws an average
current of n Amps, and the diodes conduct for 10% of the time, the
average diode current during conduction must be 10n Amps. This
non-sinusoidal current leads to harmonic distortion and a poor
power factor in the AC supply. In a practical circuit, when a
capacitor is directly connected to the output of a bridge, the
bridge diodes must be sized to withstand the current surge that
occurs when the power is turned on at the peak of the AC voltage
and the capacitor is fully discharged. Sometimes a small series
resistor is included before the capacitor to limit this current,
though in most applications the power supply transformer's
resistance is already sufficient. Output can also be smoothed using
a choke and second capacitor. The choke tends to keep the current
(rather than the voltage) more constant. Due to theU.C.E.R., GR
NOIDAPage 73
AUTOMATIC ROOM LIGHT CONTROLLER WITH VISITOR COUNTER
relatively high cost of an effective choke compared to a
resistor and capacitor this is not employed in modern equipment.
Some early console radios created the speaker's constant field with
the current from the high voltage ("B +") power supply, which was
then routed to the consuming circuits, (permanent magnets were then
too weak for good performance) to create the speaker's constant
magnetic field. The speaker field coil thus performed 2 jobs in
one: it acted as a choke, filtering the power supply, and it
produced the magnetic field to operate the speaker.
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TSOP1738 (INFRARED SENSOR)
Fig. 4.2 Infrared Sensor
Description:
The TSOP17.. Series are miniaturized receivers for infrared
remote control systems. PIN diode and preamplifier are assembled on
lead frame, the epoxy package is designed as IR filter. The
demodulated output signal can directly be decoded by a
microprocessor. TSOP17.. is the standard IR remote control receiver
series, supporting all major transmission codes.
Features: Photo detector and preamplifier in one package
Internal filter for PCM frequency Improved shielding against
electrical field disturbance TTL and CMOS compatibility
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Output active low Low power consumption High immunity against
ambient light Continuous data transmission possible (up to 2400
bps) Suitable burst length .10 cycles/burst
Block Diagram:
Fig. 4.3 Block Diagram of TSOP 1738
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Application Circuit:
Fig. 4.4 Application circuit
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LTS 542 (7-Segment Display)Description:The LTS 542 is a 0.52
inch digit height single digit seven-segment display. This device
utilizes Hi-eff. Red LED chips, which are made from GaAsP on GaP
substrate, and has a red face and red segment.
Fig. 4.6 7 Segment
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Features:
Common Anode
0.52 Inch Digit Height Continuous Uniform Segments Low power
Requirement Excellent Characters Appearance High Brightness &
High Contrast Wide Viewing Angle
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LM7805 (Voltage Regulator)
Fig. 4.7 Voltage Regulator
Description:The KA78XX/KA78XXA series of three-terminal positive
regulator are available in the TO-220/D-PAK package and with
several fixed output voltages, making them useful in a wide range
of applications. Each type employs internal current limiting,
thermal shut down and safe operating area protection, making it
essentially indestructible. If adequate heat sinking is provided,
they can deliver over 1A output current. Although designed
primarily as fixed voltage regulators, these devices can be used
with external components to obtain adjustable voltages and
currents.
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Features: Output Current up to 1A Output Voltages of 5, 6, 8, 9,
10, 12, 15, 18, 24V Thermal Overload Protection Short Circuit
Protection Output Transistor Safe Operating Area Protection
RELAY CIRCUIT:
Fig. 4.8 Relay
A single pole dabble throw (SPDT) relay is connected to port RB1
of the microcontroller through a driver transistor. The relay
requires 12 volts at a current of around 100ma, which cannot
provide by the microcontroller. So the driver transistor is added.
The relay is used to operate the external solenoid forming part of
a locking device or for operating any other electrical devices.
Normally the relay remains off. As soon as pin of the
microcontroller goes high, the relay operates. When the relay
operates and releases. Diode D2 is the
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standard diode on a mechanical relay to prevent back EMF from
damaging Q3 when the relay releases. LED L2 indicates relay on.
THE CAPACITOR FILTER-
The simple capacitor filter is the most basic type of power
supply filter. The application of the simple capacitor filter is
very limited. It is sometimes used on extremely high-voltage,
low-current power supplies for cathode ray and similar electron
tubes, which require very little load current from the supply. The
capacitor filter is also used where the power-supply ripple
frequency is not critical; this frequency can be relatively high.
The capacitor (C1) shown in figure 415 is a simple filter connected
across the output of the rectifier in parallel with the load.
Full-wave rectifier with a capacitor filter.
When this filter is used, the RC charge time of the filter
capacitor (C1) must be short and the RC discharge time must be long
to eliminate ripple action. In other words, the capacitor must
charge up fast, preferably with no discharge at all.
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Better filtering also results when the input frequency is high;
therefore, the fullwave rectifier output is easier to filter than
that of the half-wave rectifier because of its higher frequency.
For you to have a better understanding of the effect that filtering
has on Eavg, a comparison of a rectifier circuit with a filter and
one without a filter is illustrated in views A and B of figure
4-16. The output waveforms in figure 4-16 represent the unfiltered
and filtered outputs of the half-wave rectifier circuit. Current
pulses flow through the load resistance (RL) each time a diode
conducts. The dashed line indicates the average value of output
voltage. For the half-wave rectifier, Eavg is less than half (or
approximately 0.318) of the peak output voltage. This value is
still much less than that of the applied voltage. With no capacitor
connected across the output of the rectifier circuit, the waveform
in view A has a large pulsating component (ripple) compared with
the average or dc component. When a capacitor is connected across
the output (view B), the average value of output voltage (Eavg) is
increased due to the filtering action of capacitor C1.
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A: UNFILTERED :
Half-wave rectifier with and without filtering.
B: FILTERED :
The value of the capacitor is fairly large (several
microfarads), thus it presents a relatively low reactance to the
pulsating current and it stores a substantial charge.U.C.E.R., GR
NOIDAPage 84
AUTOMATIC ROOM LIGHT CONTROLLER WITH VISITOR COUNTER
The rate of charge for the capacitor is limited only by the
resistance of the conducting diode, which is relatively low.
Therefore, the RC charge time of the circuit is relatively short.
As a result, when the pulsating voltage is first applied to the
circuit, the capacitor charges rapidly and almost reaches the peak
value of the rectified voltage within the first few cycles. The
capacitor attempts to charge to the peak value of the rectified
voltage anytime a diode is conducting, and tends to retain its
charge when the rectifier output falls to zero. (The capacitor
cannot discharge immediately.) The capacitor slowly discharges
through the load resistance (RL) during the time the rectifier is
non-conducting. The rate of discharge of the capacitor is
determined by the value of capacitance and the value of the load
resistance. If the capacitance and load-resistance values are
large, the RC discharge time for the circuit is relatively long. A
comparison of the waveforms shown in figure 4-16 (view A and view
B) illustrates that the addition of C1 to the circuit results in an
increase in the average of the output voltage (Eavg) and a
reduction in the amplitude of the ripple component (Er), which is
normally present across the load resistance. Now, let's consider a
complete cycle of operation using a half-wave rectifier, a
capacitive filter (C1), and a load resistor (RL). As shown in view
A of figure 4-17, the capacitive filter (C1) is assumed to be large
enough to ensure a small reactance to the pulsating rectified
current. The resistance of RL is assumed to be much greater than
the reactance of C1 at the input frequency. When the circuit is
energized, the diode conducts on the positive half cycle and
current flows through the circuit, allowing C1 to charge. C1 will
charge toU.C.E.R., GR NOIDAPage 85
AUTOMATIC ROOM LIGHT CONTROLLER WITH VISITOR COUNTER
approximately the peak value of the input voltage. (The charge
is less than the peak value because of the voltage drop across the
diode (D1)). In view A of the figure, the heavy solid line on the
waveform indicates the charge on C1. As illustrated in view B, the
diode cannot conduct on the negative half cycle because the anode
of D1 is negative with respect to the cathode. During this
interval, C1 discharges through the load resistor (RL). The
discharge of C1 produces the downward slope as indicated by the
solid line on the waveform in view B. In contrast to the abrupt
fall of the applied ac voltage from peak value to zero, the voltage
across C1 (and thus across RL) during the discharge period
gradually decreases until the time of the next half cycle of
rectifier operation. Keep in mind that for good filtering, the
filter capacitor should charge up as fast as possible and discharge
as little as possible. Figure. - Capacitor filter circuit (positive
and negative half cycles). POSITIVE HALFCYCLE
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Figure. - Capacitor filter circuit (positive and negative half
cycles). NEGATIVE HALF-CYCLE
Since practical values of C1 and RL ensure a more or less
gradual decrease of the discharge voltage, a substantial charge
remains on the capacitor at the time of the next half cycle of
operation. As a result, no current can flow through the diode until
the rising ac input voltage at the anode of the diode exceeds the
voltage on the charge remaining on C1. The charge on C1 is the
cathode potential of the diode. When the potential on the anode
exceeds the potential on the cathode (the charge on C1), the diode
again conducts, and C1 begins to charge to approximately the peak
value of the applied voltage. After the capacitor has charged to
its peak value, the diode will cut off and the capacitor will start
to discharge. Since the fall of the ac input voltage on the anode
is considerably more rapid than the decrease on the capacitor
voltage, the
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cathode quickly become more positive than the anode, and the
diode ceases to conduct. Operation of the simple capacitor filter
using a full-wave rectifier is basically the same as that discussed
for the half-wave rectifier. Referring to figure, you should notice
that because one of the diodes is always conducting on alternation,
the filter capacitor charges and discharges during each half cycle.
(Note that each diode conducts only for that portion of time when
the peak secondary voltage is greater than the charge across the
capacitor.)Figure - Full-wave rectifier (with capacitor
filter).
Another thing to keep in mind is that the ripple component (E r)
of the output voltage is an ac voltage and the average output
voltage (Eavg) is the dc component of the output. Since the filter
capacitor offers relatively low impedance to ac, the majority of
the ac component flows through the filter capacitor. The ac
component is therefore bypassed (shunted) around the load
resistance, and the
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entire dc component ( Eavg) flows through the load resistance.
This statement can be clarified by using the formula for XC in a
half-wave and full-wave rectifier. First, you must establish some
values for the circuit. As you can see from the calculations, by
doubling the frequency of the rectifier, you reduce the impedance
of the capacitor by one-half. This allows the ac component to pass
through the capacitor more easily. As a result, a full-wave
rectifier output is much easier to filter than that of a half-wave
rectifier. Remember, the smaller the XC of the filter capacitor
with respects to the load resistance, the better the filtering
action. Since
the largest possible capacitor will provide the best filtering.
Remember, also, that the load resistance is an important
consideration. If load resistance is made small, the load current
increases, and the average value of output voltage (Eavg)
decreases. The RC discharge time constant is a direct function of
the value of the load resistance; therefore, the rate of capacitor
voltage discharge is a direct function of the current through the
load. The greater the load current, the more rapid the discharge of
the capacitor, and the lower the average value of output voltage.
For this reason, the simple capacitive filter is seldom used with
rectifier circuits that must supply a relatively large load
current. Using the simple capacitive filter in conjunction with a
full-wave or bridge rectifier provides improved filtering
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because the increased ripple frequency decreases the capacitive
reactance of the filter capacitor.
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CHAPTER :- 5 SOFTWARE DESIGN
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FLOW CHART:
Fig. 4.7 Flow Chart
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If the sensor 1 is interrupted first then the microcontroller
will look for the sensor 2. And if it is interrupted then the
microcontroller will increment the count and switch on the relay,
if it is first time interrupted. If the sensor 2 is interrupted
first then the microcontroller will look for the sensor 1. And if
it is interrupted then the microcontroller will decrement the
count. When the last person leaves the room then counter goes to 0
and that time the relay will turn off. And light will be turn
off.
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CHAPTER :- 6 TESTING AND RESULTS
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Testing And Results
We started our project by making power supply. That is easy for
me but when we turn toward the main circuit, there are many
problems and issues related to it, which we faced, like component
selection, which components is better than other and its feature
and cost wise a We started our project by making power supply. That
is easy for me but when I turn toward the main circuit, there are
many problems and issues related to it, which are I faced, like
component selection, which components is better than other and its
feature and cost wise also, then refer the data books and other
materials related to its. I had issues with better or correct
result, which I desired. And also the software problem. I also had
some soldering issues which were resolved using continuity checks
performed on the hardware. We had issues with better or correct
result, which we desired. And also the software problem. We also
had some soldering issues which were resolved using continuity
checks performed on the hardware. We started testing the circuit
from the power supply. There we got over first trouble. After
getting 9V from the transformer it was not converted to 5V and the
circuit received 9V.U.C.E.R., GR NOIDAPage 95
AUTOMATIC ROOM LIGHT CONTROLLER WITH VISITOR COUNTER
As the solder was shorted IC 7805 got burnt. So we replaced the
IC7805.also the circuit part around the IC7805 were completely
damaged..with the help of the solder we made the necessary
paths.
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CHAPTER :- 7 FUTURE EXPANSION
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FUTURE EXPANSION
By using this circuit and proper power supply we can implement
various applications Such as fans, tube lights, etc.
By modifying this circuit and using two relays we can achieve a
task of opening and closing the door.
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CHAPTER :- 8 APPLICATION, ADVANTAGES & DISADVANTAGES
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APPLICATION, ADVANTAGES & DISADVANTAGES
Applicationo For counting purposes o For automatic room light
control
Advantages o Low cost o Easy to use o Implement in single
door
Disadvantages
o It is used only when one single person cuts the rays of the
sensorhence it cannot be used when two person cross
simultaneously.
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CHAPTER :- 9 BIBILOGRAPHY
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Bibliography Reference Books Programming in ANSI C: E
BALAGURUSAMY The 8051microcontroller and embedded systems: MUHAMMAD
ALIMAZIDI, JANICE GILLISPIE MAZIDI The 8051 microcontroller:
KENNETH J. AYALA
Website www.datasheets4u.com www.8051.com
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