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AUTOMATIC ROOM LIGHT CONTROLLER WITH VISITOR COUNTER
TABLE OF CONTENTS
PAGE NO:
CHAPTER-1
1: INTRODUCTION OF PROJECT (7)
2: PROJECT OVERVIWE (8)
CHAPTER-2
BLOCK DIAGRAM AND ITS DESCRIPTION
1: BASIC BLOCK DIAGRAM (10)
2: BLOCK DIAGRAM DISCRIPTION (11)
CHAPTER-3
SCHEMATIC DIAGRAM
TRANSMISION CIRCUIT (14)
RECEIVER CIRCUIT (15)
CIRCUIT DISCRIPTION (16)
CHAPTER-4
HARDWARE DESIGN & DESCRIPTION (20)
LIST OF COMPONENT (23)
COMPONENT DESCRIPTION
1: MICROCONTROLLER (24)
2: ULN 2003 7805 (39)
3: VOLTAGE REGULTAR (42)
4: POWER SUPPLY (44)
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5: BRIDGE RECTIFIER (45)
6: TRANSFORMER (45)
7: DIODES (46)
8: RESISTER (47)
9: CAPECITOR (50)
10: LED (52)
11: BUZZER (54)
555 TIMER (56)
POWER SUPPLY (66)
A: TRANSFORMER
B: BASIC PART OF TRASFORMER
C: COMPONENT OF TRASFORMER
BRIDGE RECTIFIER (69)
IR SENSOR (75)
7- SEGMENT DISPLAY (78)
VOLTAGE REGULATOR (80)
RELAY CIRCUIT (81)
CHAPTER-5
SOFTWARE DESIGN (91)
CHAPTER-6
TESTING AND RESULT (94)
CHAPTER-7
FUTURE EXPANSION (97)
CHAPTER-8
APPLICATION, ADVANTAGE & DISADVANTAGE (99)
CHAPTER-9
BIBLOGRAPHY (102)
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CHAPTER :- 1
Project Overview
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1. Introduction Of Project
1.1 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
Enter Exit
S
Fig. 2.1 Basic Block Diagram
Signal
Conditioning
Enter Sensor
Exit Sensor
Power Supply
Signal
Conditioning
A
T
8
9
S
Light
Relay Driver
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2.2 Block Diagram Description
The 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 fact
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that only one of its output states is stable. It is also known as a 'one-
shot'.
In this circuit, a negative pulse applied at pin 2 triggers an internal flip-flop 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. And
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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:-
Fig. 4.1 Snap of the entire circuit
Infrared SensorMicrocontroller
Relay7-Segment
Timer IC
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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 wasdone. 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 DESCRIPTION
The 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 high-
density 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 cost-
effective 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 clockcircuitry. 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 8051
12345678910
11121314151617181920
40393837363534333231
30292827262524232221
P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7RST
(RXD)P3.0
(TXD)P3.1
(T0)P3.4(T1)P3.5
XTAL2XTAL1
GND
(INT0)P3.2(INT1)P3.3
(RD)P3.7(WR)P3.6
VccP0.0(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/PROGPSENP2.7(A15)P2.6(A14)P2.5(A13)P2.4(A12)P2.3(A11)P2.2(A10)P2.1(A9)P2.0(A8)
8051
(8031)
Figure No. 1.1: Pin Diagram of 8051
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PROCESSOR
A processor is an electronic device capable of manipulating data in a way
specified by a sequence of instructions.
INSTRUCTIONS
Instructions 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.
PROGRAM
The sequence of instructions is what constitutes a program. The
sequence of instructions may be altered to suit the application.
ASSEMBLY LANGUAGE
Writing 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 mnemonicsForm is called an assembly language program. But it must be converted
into machine language for execution by processor.
ASSEMBLER
An 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 LANGUAGE
A 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 DESCRIPTION
VCC (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 31
Connected to VCC for on chip ROM
Connected to Ground for external ROM containing the code Input Pin
Program Store Enable: PSEN 29
Output 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 0
Pins 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 1
Pins 1 through 8
Both input or output
No dual function
Internal pull up registers
On RESET configured as output
PORT 2
Pins 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-A16
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PORT 3
Pins 10 through 17
No external pull up resistors required
PROCESSOR ARCHITECTURE
Block Diagram
CPU
On-chipRAM
On-chipROM forprogramcode
4 I/O Ports
Timer 0
SerialPortOSC
InterruptControl
External interrupts
Timer 1
Timer/Counter
BusControl
TxD RxDP0 P1 P2 P3
Address/Data
CounterInputs
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Figure No. 1.3: Block Diagram of Microcontroller
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ALU
The Arithmetic Logic Unit (ALU) performs the internal arithmeticmanipulation 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 fromtwo 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.
REGISTERS
Registers 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 REGISTERS
Stores the current status of various flags denoting conditions resulting
from various operations.
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CONTROL REGISTERS
Contains configuration bits that affect processor operation and the
operating modes of various internal subsystems.
Memory Organization
Program Memory
Data Memory
The right half of the internal and external data memory spacesavailable 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 addressesare 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 different
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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 Set
All 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 requireBoolean processing. The following overview of the instruction set gives a
brief description of how certain instructions can be used.
Program Status Word
The 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 oddnumber 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 Modes
The addressing modes in the Flash microcontroller instruction set are as
follows.
Direct Addressing
In 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 Addressing
In 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 Instructions
The 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 the
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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 Addressing
Program 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.
SRAM
Volatile, fast, low capacity, expensive, requires lesser external support circuitry.
DRAM
Volatile, relatively slow, highest capacity needs continuous refreshing. Hence
require external circuitry.
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OTP ROM
One time programmable, used for shipping in final products.
EPROM
Erasable programmable, UV Erasing, Used for system development and
debugging.
EEPROM
Electrically erasable and programmable, can be erased programmed in- circuit,
Used for storing system parameters.
FLASH
Electrically programmable & erasable, large capacity, organized as sectors.
BUSES
A 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 bus
Address bus
Control bus
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CONTROLLER LOGIC
Processor brain decodes instructions and generate control signal for various sub
units. It has full control over the clock distribution unit of processor.
I/O Peripherals
The 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
DESCRIPTION
The 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 Parameter Value Unit
V Output voltage 50 V
Vi Input voltage 30 V
Ic Countinuous
collector current
500 Ma
Ib Countinuous
base current
25 Ma
Ta Operating
ambient
tempreture
range
-20 - 85
Tstg Storage
tempreture
range
-55 - 155
Tj Junction
tempreture
150
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Table :-2 Thermal Data
Symbol Parameter Dip -16 So -16 Unit
R th.ra Thermal
resistance
junction
ambient - max
70 120 C/w
WHY WE USE ULN 2003?
Digital system and microcontroller pins lack sufficient current to drive the relay.
(3)VOLTAGE REGULATOR
Voltage 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
DESCRIPTION
These voltage regulators are monolithic circuit integrated circuit designed as fixed
voltage regulators for a wide variety of applications including local, on cardregulation. 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.
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FEATURES
Output current in Excess of 1.0 A
No 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 RECTIFIER
Bridge rectifier circuit consists of four diodes arranged in the form of a bridge as
shown in figure.
OPERATION
During the positive half cycle of the input supply, the upper end A of thetransformer 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)TRANSFORMER
Transformer 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
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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)DIODE
The diode is a p-n junction device. Diode is the component used to control theflow of the current in any one direction. The diode widely works in forward bias.
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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).
APPLICATION
Diodes: Rectification, free-wheeling, etc
Zener diode: Voltage control, regulator etc.
Tunnel diode: Control the current flow, snobbier circuit, etc
(8)RESISTORS
The 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
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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.
FUNCTION
Resistor 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 RESISTORS
It includes two types of resistors as carbon film and metal film .These two types
are explained under
1. CARBON FILM RESISTORS
During 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 Resistors
Another 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 RESISTORS
Metal film and metal oxides resistors are made in a similar way, but can be mademore 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 RESISTOR
A 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.
TESTING
Resistors are checked with an ohm meter/millimeter. For a defective resistor the
ohm-meter shows infinite high reading.
(9)CAPACITORS
In 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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BASIC
Like 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 theplates 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.
TESTING
To 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)LED
LED 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 biasedP-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.
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LED is a component used for indication. All the functions being carried out aredisplayed 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)BUZZER
Buzzer 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.
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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 supply
potential 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 set
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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 longerthan 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
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input for this period of time afterthe 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 triggercurrent, 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-pole
stage 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) is
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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 a
low state. The reset voltage threshold level is 0.7 volt, and a sink current of 0.1mA
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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 varyfrom 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+ voltage-
divider 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 the
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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.
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Pin 6 (Threshold): Pin 6 is one input to the upper comparator (the other being
pin 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 thresholdcurrent, 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 npn
transistor (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 monostable
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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 voltage
terminal 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.
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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 (2/3 Vs) makes output low, 0V
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When the input voltage is between1/3 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 least1/3 Vs to make the output switch back.
Fig: IR Sensor Circuit.
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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 magnetically-coupled 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 primarywinding 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.
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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 RECTIFIER-
A 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.
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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 theright 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 DC-
powered 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 the
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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 lethalcharge after theAC 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 = RCwhere 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. Thesmoothing 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 the
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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 currentfrom 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 onextremely 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 4-
15 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 full-
wave 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.
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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 to
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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 HALF-
CYCLE
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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 thesame 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.
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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
Application
o 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 sensor
hence 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
http://www.datasheets4u.com/http://www.datasheets4u.com/http://www.8051.com/http://www.8051.com/http://www.8051.com/http://www.datasheets4u.com/