room light

7/30/2019 Room Light

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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
http://en.wikipedia.org/wiki/Image:Diode_bridge_alt_2.svghttp://en.wikipedia.org/wiki/Image:Diode_bridge_alt_1.svghttp://en.wikipedia.org/wiki/Image:Diode_bridge_alt_2.svghttp://en.wikipedia.org/wiki/Image:Diode_bridge_alt_1.svg


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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
http://en.wikipedia.org/wiki/File:Diode_bridge_smoothing.svg


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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/

room light

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