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TIME OPERATED ELECTRICAL APPLIANCE

CONTROLLING SYSTEM FOR INDUSTRIAL APPLICATION

Dissertation submitted in partial fulfillment of the

Academic requirements for the award of

Bachelor of Technology

In

Electronics and Communication Engineering

By

G.Sujitha sree (Roll no.08X81A0443)

T.Santhosh (Roll no.08X81A0432)

Y.Dinesh (Roll no.08X81A0407)

Under the Guidance of

Mr.CH.Rajendra Prasad

Asst. Prof. Dept. of ECE

Department of Electronics & Communication Engineering

Sri Sarada Institute of Science & Technology(Affiliated to Jawaharlal Nehru Technological University)

Anantharam

2010-2011

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Department of Electronics & Communication Engineering

Sri Sarada Institute of Science & Technology(Approved by AICTE, Recognized by Govt. of A.P. and Affiliated to J.N.T.U.H,

Hyderabad.) Anantharam (V), Near Bibinagar, Bhongir (M), Nalgonda (Dist).

Certificate

This is to certify that the project work titled Time Opareted Electrical Applicance

Controlling System For Industrial Application submitted by M.sujitha Sree,

T.Santhosh, Y.Dinesh the students of Department of ECE, Sri Sarada institute of

science and technology, JNTUH in partial fulfillment of the requirements for award of

the degree ofBachelor of Technology is a record of the bonafide work carried out by

them during the academic year 2010-2011.

Head of the Department Internal Guide

Mr.CH.Rambabu Mr.CH.Rajendra Prasad

Assistant Professor Assistant Professor

Dept. of ECE Dept. of ECE

SSIST SSIST

External Examiner

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Declaration

This is to certify that the work reported in the present thesis titled Time

Opareted Electrical Applicance Controlling System For Industrial Application is a

record of work done by us in the Department of Electronics and communication

Engineering (ECE),Sarada Institute of Science And Technology, JNTUH

No part of the thesis is copied from books/Journals/Internet and wherever the

portion is taken, the same has been duly referred in the text. The reported are based on

the project work done entirely by us and not copied from any other source.

M.Sujitha sree (Roll no.08X81A0443)

T.Santhosh (Roll no.08X81A0432)

Y.Dinesh (Roll no.08X81A0407)

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Acknowledgements

We are extremely thankful to our internal guide Mr. CH.Rajendra Prasad Asst. Prof. in

ECE Department, Sri Sarada institute of science and technology, for his excellent guidance

and constant encouragement throughout the project work. It was a pleasant and challenging

experience to work under his supervision. Her constant monitoring and the valuable advices

ensured the completion of this thesis. We thank to his for setting high standards and

motivating us to do our best.

We wish to express our sincere thanks to Mr. CH. Rajendra Prasad, Asst. Prof. for his

valuable advices make confident that the completion of this Project work.

We wish to express our gratitude to Mr. CH. Ram Babu, HOD of ECE, for permitting to

do our project work at Department.

We take this opportunity to acknowledge our college principal Prof. Ravindranath, with

deep sense of gratitude for their support and encouragement.

We express my heartfelt gratitude to my family members, who patiently cooperated and

constantly supported for the successful completion. Last but not the least; we would like to

thank friends and well wishers for their direct and indirect help.

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TABLE OF CONTENTS

1. ABSTRACT 7

2. INTRODUCTION

2.1. EMBEDDED SYSTEMS 9

2.2 MICROCONTROLLERS 15

2.3. LCD 17

2.4. LED 24

2.5. KEIL-C COMPILER 26

3. COMPONENT DESCRIPTION

3.1. AT89S52 29

3.2. DS1307 41

3.3. 74LS21 54

3.4. TRANSISTOR AS A SWITCH 57

3.5. SPDT RELAY 60

3.6. ISP PROGRAMMER 67

4. SCHEMATIC DIAGRAM 70

5. CODING 71

6. Result and Discussion 92

7. Future Scope 94

8. References 95

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List of figures

1. Fig 3.1-PIN CONFIGURATION 40-lead PDIP(AT89S52) 33

2. Fig 3.2-ARCHITECTUREof AT89S52 34

3. Fig 3.3-INTERNAL BLOCK DIAGRAM OF AT89S52 39

4. Fig 3.4-OSCILLATOR\ 40

5. Fig 3.5-PIN DESCRIPTION OF DS1307 41

6. Fig 3.6-CIRCUIT DESCRIPTION OF DS1307 43

7. Fig 3.7- BLOCK DIAGRAM OF DS1307 44

8. Fig 3.8-TIME KEEP DESCRIPTION OF DS1307 48

9. Fig 3.9-TWO WIRE CONFIGURATION OF DS1307 50

10. Fig 3.10-DATA TRANSFER ON 2-WIRE SERIAL BUS52

11. Fig 3.11- PIN DESCRIPTION OF 74LS2155

12. Fig 3.12-CONNECTION OF 74LS2155

13. Fig 3.13-TRANSISTOR CURVES57

14. Fig 3.14-TRANSISTOR SWITCHING CIRCUIT58

15. Fig 3.15-SPDT RELAY63

16. Fig 3.16-ISP PROGRAMMER66

17.Fig 3.17 ISP BLOCK DIAGRAM 66

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18.Fig 3.18 ISP PIN CONNECTION 67

ABSTRACT

It is well known that the electrical appliances are more useful in every day life.

Industries are not small. It is very difficult to monitor overall industry with in short time,

so if we are implementing one embedded product which will solve our problem. One

more option is power wastage. In some cases industries devices are in ON state even

though it is not required. That leads power wastage. To save the power if we are

implementing one circuit that is more useful. There are different ways available to

implement such type of applications. In that, one option is time based control.

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To implement this application time is more important. For that we have to

interface RTC to the microcontroller. In this application we are interfacing DS1307

(RTC) to get the real-time clock. To read the time from the DS1307 user has to develop

I2C protocol logic in the microcontroller. After reading data from the RTC that data is

applied on the LCD. But that is not our application now. To implement our exact

requirement we have to select ON time and OFF time. For selecting the ON time and

OFF time one more switch is placed. Once ON time and OFF time is selected whenever

that time reaches electrical appliance is ON with the help of relay. And electrical

appliance is OFF whenever it reaches to OFF time, so that we can save the power.

BLOCK DIAGRAM:

8

AT89S52

LCD

DS1307

7

4

L

S2

1

SEL

INC

DEC

EXIT

SPDT

RELAY

AC

DEVICE

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HARDWARE:

AT89S52 microcontroller

16X2 LCD

74LS21

DS1307

SPDT RELAY

AC DEVICE

SOFTWARE:

KEIL C-Compiler

PROGRAMMING IN EMBEDDED C

2.INTRODUCTION

2.1 EMBEDDED SYSTEMS

Embedded systems are electronic devices that incorporate microprocessors with

in their implementations. The main purposes of the microprocessors are to simplify the

system design and provide flexibility. Having a microprocessor in the device helps in

removing the bugs, making modifications, or adding new features are only matter of

rewriting the software that controls the device. Or in other words embedded computer

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TIME

SELECT

SWITCH

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systems are electronic systems that include a microcomputer to perform a specific

dedicated application. The computer is hidden inside these products. Embedded systems

are ubiquitous. Every week millions of tiny computer chips come pouring out of factories

finding their way into our everyday products.

Embedded systems are self-contained programs that are embedded within a piece

of hardware. Whereas a regular computer has many different applications and software

that can be applied to various tasks, embedded systems are usually set to a specific task

that cannot be altered without physically manipulating the circuitry. Another way to think

of an embedded system is as a computer system that is created with optimal efficiency,

thereby allowing it to complete specific functions as quickly as possible.

Embedded systems designers usually have a significant grasp of hardware

technologies. They use specific programming languages and software to develop

embedded systems and manipulate the equipment. When searching online, companies

offer embedded systems development kits and other embedded systems tools for use by

engineers and businesses.

Embedded systems technologies are usually fairly expensive due to the necessary

development time and built in efficiencies, but they are also highly valued in specific

industries. Smaller businesses may wish to hire a consultant to determine what sort of

embedded systems will add value to their organization.

2.1.1 CHARACTERISTICS:

Two major areas of differences are cost and power consumption. Since many

embedded systems are produced in tens of thousands to millions of units range, reducing

cost is a major concern. Embedded systems often use a (relatively) slow processor and

small memory size to minimize costs.

The slowness is not just clock speed. The whole architecture of the computer is

often intentionally simplified to lower costs. For example, embedded systems often use

peripherals controlled by synchronous serial interfaces, which are ten to hundreds of

times slower than comparable peripherals used in PCs. Programs on an embedded system

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often run with real-time constraints with limited hardware resources: often there is no

disk drive, operating system, keyboard or screen. A flash drive may replace rotating

media, and a small keypad and LCD screen may be used instead of a PC's keyboard and

screen.

Firmware is the name for software that is embedded in hardware devices, e.g. in

one or more ROM/Flash memory IC chips. Embedded systems are routinely expected to

maintain 100% reliability while running continuously for long periods, sometimes

measured in years. Firmware is usually developed and tested too much harsher

requirements than is general-purpose software, which can usually be easily restarted if a

problem occurs.

2.1.2 PLATFORM:

There are many different CPU architectures used in embedded designs. This in

contrast to the desktop computer market which is limited to just a few competing

architectures mainly the Intel/AMD x86 and the Apple/Motorola/IBM Power PCs which

are used in the Apple Macintosh. One common configuration for embedded systems is

the system on a chip, an application-specific integrated circuit, for which the CPU was

purchased as intellectual property to add to the IC's design.

2.1.3 TOOLS:

Like a typical computer programmer, embedded system designers use compilers,

assemblers and debuggers to develop an embedded system. Those software tools can

come from several sources:

Software companies that specialize in the embedded market Ported from

the GNU software development tools. Sometimes, development tools for a personal

computer can be used if the embedded processor is a close relative to a common PC

processor. Embedded system designers also use a few software tools rarely used by

typical computer programmers. Some designers keep a utility program to turn data files

into code, so that they can include any kind of data in a program. Most designers also

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have utility programs to add a checksum or CRC to a program, so it can check its

program data before executing it.

2.1.4 OPERATING SYSTEM:

They often have no operating system, or a specialized embedded operating system

(often a real-time operating system), or the programmer is assigned to port one of these to

the new system.

2.1.5 DEBUGGING:

Debugging is usually performed with an in-circuit emulator, or some type of

debugger that can interrupt the micro controllers internal microcode. The microcode

interrupt lets the debugger operate in hardware in which only the CPU works. The CPU-based debugger can be used to test and debug the electronics of the computer from the

viewpoint of the CPU.

Developers should insist on debugging which shows the high-level language, with

breakpoints and single stepping, because these features are widely available. Also,

developers should write and use simple logging facilities to debug sequences of real-time

events. PC or mainframe programmers first encountering this sort of programming often

become confused about design priorities and acceptable methods. Mentoring, code-reviews and ego less programming are recommended.

2.1.6DESIGN OF EMBEDDED SYSTEMS:

The electronics usually uses either a microprocessor or a microcontroller. Some

large or old systems use general-purpose mainframes computers or minicomputers.

2.1.7START-UP:

All embedded systems have start-up code. Usually it disables interrupts, sets up

the electronics, tests the computer (RAM, CPU and software), and then starts the

application code. Many embedded systems recover from short-term power failures by

restarting (without recent self-tests). Restart times under a tenth of a second are common.

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Many designers have found one of more hardware plus software-

controlled LEDs useful to indicate errors during development (and in some instances,

after product release, to produce troubleshooting diagnostics). A common scheme is to

have the electronics turn off the LED(s) at reset, whereupon the software turns it on at the

first opportunity, to prove that the hardware and start-up software have performed their

job so far. After that, the software blinks the LED(s) or sets up light patterns during

normal operation, to indicate program execution progress and/or errors. This serves to

reassure most technicians/engineers and some users.

2.1.8THE CONTROL LOOP:

In this design, the software has a loop. The loop calls subroutines. Each

subroutine manages a part of the hardware or software. Interrupts generally set flags, or

update counters that are read by the rest of the software. A simple API disables and

enables interrupts. Done right, it handles nested calls in nested subroutines, and restores

the preceding interrupt state in the outermost enable. This is one of the simplest methods

of creating an exocrine.

Typically, there's some sort of subroutine in the loop to manage a list of software

timers, using a periodic real time interrupt. When a timer expires, an associated

subroutine is run, or flag is set. Any expected hardware event should be backed-up with asoftware timer. Hardware events fail about once in a trillion times.

State machines may be implemented with a function-pointer per state-

machine (in C++, C or assembly, anyway). A change of state stores a different function

into the pointer. The function pointer is executed every time the loop runs.

Many designers recommend reading each IO device once per loop, and storing the

result so the logic acts on consistent values. Many designers prefer to design their state

machines to check only one or two things per state. Usually this is a hardware event, and

a software timer. Designers recommend that hierarchical state machines should run the

lower-level state machines before the higher, so the higher run with accurate information.

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Complex functions like internal combustion controls are often handled with multi-

dimensional tables. Instead of complex calculations, the code looks up the values. The

software can interpolate between entries, to keep the tables small and cheap.

One major disadvantage of this system is that it does not guarantee a time torespond to any particular hardware event. Careful coding can easily assure that nothing

disables interrupts for long. Thus interrupt code can run at very precise timings. Another

major weakness of this system is that it can become complex to add new features.

Algorithms that take a long time to run must be carefully broken down so only a little

piece gets done each time through the main loop.

This system's strength is its simplicity, and on small pieces of software the loop is

usually so fast that nobody cares that it is not predictable. Another advantage is that this

system guarantees that the software will run. There is no mysterious operating system to

blame for bad behavior.

2.1.9USER INTERFACES:

Interface designers at PARC, Apple Computer, Boeing and HP minimize the

number of types of user actions. For example, use two buttons (the absolute minimum) to

control a menu system (just to be clear, one button should be "next menu entry" the other

button should be "select this menu entry"). A touch-screen or screen-edge buttons alsominimize the types of user actions.

Another basic trick is to minimize and simplify the type of output. Designs should

consider using a status light for each interface plug, or failure condition, to tell what

failed. A cheap variation is to have two light bars with a printed matrix of errors that they

select- the user can glue on the labels for the language that she speaks.

For example, Boeing's standard test interface is a button and some lights. When

you press the button, all the lights turn on. When you release the button, the lights with

failures stay on. The labels are in Basic English.

Designers use colors. Red defines the users can get hurt- think of blood. Yellow

defines something might be wrong. Green defines everything's OK.

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Another essential trick is to make any modes absolutely clear on the user's

display. If an interface has modes, they must be reversible in an obvious way. Most

designers prefer the display to respond to the user. The display should change

immediately after a user action. If the machine is going to do anything, it should start

within 7 seconds, or give progress reports.

One of the most successful general-purpose screen-based interfaces is the two

menu buttons and a line of text in the user's native language. It's used in pagers, medium-

priced printers, network switches, and other medium-priced situations that require

complex behavior from users. When there's text, there are languages. The default

language should be the one most widely understood.

2.2 MICROCONTROLLERS

Microcontrollers as the name suggests are small controllers. They are like

single chip computers that are often embedded into other systems to function as

processing/controlling unit. For example the remote control you are using probably has

microcontrollers inside that do decoding and other controlling functions. They are also

used in automobiles, washing machines, microwave ovens, toys ... etc, where automation

is needed.

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Micro-controllers are useful to the extent that they communicate with

other devices, such as sensors, motors, switches, keypads, displays, memory and even

other micro-controllers. Many interface methods have been developed over the years to

solve the complex problem of balancing circuit design criteria such as features, cost, size,

weight, power consumption, reliability, availability, manufacturability. Many

microcontroller designs typically mix multiple interfacing methods. In a very simplistic

form, a micro-controller system can be viewed as a system that reads from (monitors)

inputs, performs processing and writes to (controls) outputs.

Embedded system means the processor is embedded into the required

application. An embedded product uses a microprocessor or microcontroller to do one

task only. In an embedded system, there is only one application software that is typically

burned into ROM. Example: printer, keyboard, video game player

Microprocessor - A single chip that contains the CPU or most of the computer

Microcontroller - A single chip used to control other devices

Microcontroller differs from a microprocessor in many ways. First and the

most important is its functionality. In order for a microprocessor to be used, other

components such as memory, or components for receiving and sending data must be

added to it. In short that means that microprocessor is the very heart of the computer. On

the other hand, microcontroller is designed to be all of that in one. No other external

components are needed for its application because all necessary peripherals are already

built into it. Thus, we save the time and space needed to construct devices.

2.2.1MICROPROCESSOR VS MICROCONTROLLER:

Microprocessor:

CPU is stand-alone, RAM, ROM, I/O, timer are separate

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Designer can decide on the amount of ROM, RAM and I/O ports.

expensive

versatility general-purpose

Microcontroller:

CPU, RAM, ROM, I/O and timer are all on a single chip

fix amount of on-chip ROM, RAM, I/O ports

for applications in which cost, power and space are critical

single-purpose

2.3 LIQUID CRYSTAL DISPLAY

A liquid crystal display (LCD) is a thin, flat panel used for electronically

displaying information such as text, images, and moving pictures. Its uses include

monitors for computers, televisions, instrument panels, and other devices ranging from

aircraft cockpit displays, to every-day consumer devices such as video players, gaming

devices, clocks, watches, calculators, and telephones. Among its major features are its

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lightweight construction, its portability, and its ability to be produced in much larger

screen sizes than are practical for the construction of cathode ray tube (CRT) display

technology. Its low electrical power consumption enables it to be used in battery-powered

electronic equipment. It is an electronically-modulated optical device made up of any

number of pixels filled with liquid crystals and arrayed in front of a light source

(backlight) or reflector to produce images in color or monochrome. The earliest discovery

leading to the development of LCD technology, the discovery of liquid crystals, dates

from 1888. By 2008, worldwide sales of televisions with LCD screens had surpassed the

sale of CRT units.

2.3.1 PIN DESCRIPTION:

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PIN DESCRIPTION:

PIN SYMBOL I/O DESCRIPTION

1 VSS -- Ground

2 VCC -- +5V power supply

3 VEE -- Power supply to control contrast

4 RS I RS=0 to select command register

RS=1 to select data register

5 R/W I R/W=0 for write

R/W=1 for read

6 EN I/O Enable

7 DB0 I/O The 8-bit data bus








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VCC, VSS and VEE:

While VCC and VSS provide +5V and ground respectively, VEE is used for

controlling LCD contrast.

RS (REGISTER SELECT):

There are two important registers inside the LCD. When RS is low (0), the

data is to be treated as a command or special instruction (such as clear screen, position

cursor, etc.). When RS is high (1), the data that is sent is a text data which should be

displayed on the screen. For example, to display the letter "T" on the screen you would

set RS high.

RW (READ/WRITE):

The RW line is the "Read/Write" control line. When RW is low (0), the

information on the data bus is being written to the LCD. When RW is high (1), the

program is effectively querying (or reading) the LCD. Only one instruction ("Get LCD

status") is a read command. All others are write commands, so RW will almost be low.

EN (ENABLE):

The EN line is called "Enable". This control line is used to tell the LCD

that you are sending it data. To send data to the LCD, your program should first set this

line high (1) and then set the other two control lines and/or put data on the data bus.

When the other lines are completely ready, bring EN low (0) again. The 1-0 transition

tells the 44780 to take the data currently found on the other control lines and on the data

bus and to treat it as a command.

D0-D7 (DATA LINES):

The 8-bit data pins, D0-D7 are used to send information to the LCD or

read the content of the LCDs internal registers.

To display letters and numbers, we send ASCII codes for the letters A-Z,

a-z and numbers 0-9 to these pins while making RS=1.

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There are also instruction command codes that can be sent to the LCD to

clear the display or force the cursor to the home position or blink the cursor.

We also use RS=0 to check the busy flag bit to see if the LCD is ready to

receive the information. The busy flag is D7 and can be read when R/W = 1 and RS=0, as

follows: if R/W = 1, RS = 0. When D7=1 (busy flag = 1), the LCD is busy taking care of

internal operations and will not accept any new information. When D7 = 0, the LCD is

ready to receive new information.

Note: it is recommended to check the flag before writing any data to LCD.

2.3.2LCD COMMAND CODES:

CODE (HEX) COMMAND TO LCD INSTRUCTION REGISTER

0X01 CLEAR DISPLAY SCREEN

0X02 RETURN HOME

0X04 DECREMENT CURSOR(SHIFT CURSOR TO LEFT)

0X06 INCREMENT CURSOR(SHIFT CURSOR TO RIGHT)

0X05 SHIFT DISPLAY RIGHT

0X07 SHIFT DISPLAY LEFT

0X08 DISPLAY OFF,CURSOR OFF

0X0A DISPLAY OFF,CURSOR ON

0X0C DISPLAY ON,CURSOR OFF0X0E DISPLAY ON CURSOR BLINKING

0X0F DISPLAY ON CURSOR BLINKING

0X10 SHIFT CURSOR POSITION TO LEFT

0X14 SHIFT CURSOR POSITION TO RIGHT

0X18 SHIFT THE ENTIRE DISPLAY TO THE LEFT

0X1C SHIFT THE ENTIRE DISPLAY TO THE RIGHT

0X80 FORCE CURSOR TO BEGINNING OF 1ST LINE

0XC0 FORCE CURSOR TO BEGINNING OF 2ND LINE

0X38

0X30

0X280X20

8-BIT INTERFACE, 2 LINES, 5*7 PIXELS

8-BIT INTERFACE, 1 LINE, 5*7 PIXELS

4-BIT INTERFACE, 2 LINES, 5*7 PIXELS4-BIT INTERFACE, 1 LINE, 5*7 PIXELS

2.3.3CURSOR ADDRESSES FOR LCDS:

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16x2 LCD 80 81 82 83 84 85 86 through 8FC0 C1 C2 C3 C4 C5 C6 through CF

20x1 LCD 80 81 82 83 through 93

20x2 LCD 80 81 82 83 through 93

C0 C1 C2 C3 through D320x4 LCD 80 81 82 83 through 93

C0 C1 C2 C3 through D3

94 95 96 97 through A7D4 D5 D6 D7 through E7

40x2 LCD 80 81 82 83 through A7C0 C1 C2 C3 through E7

NOTE: All data is in HEX.

2.3.4ADVANTAGES:

LCD interfacing with 8051 is a real-world application. In recent years the LCD is

finding widespread use replacing LEDs (seven segment LEDs or other multi segment

LEDs).

This is due to following reasons:

The declining prices of LCDs.

The ability to display numbers, characters and graphics. This is in contrast to

LEDs, which are limited to numbers and a few characters. An intelligent LCD

displays two lines, 20 characters per line, which is interfaced to the 8051.

Incorporation of a refreshing controller into the LCD, thereby relieving the CPU

to keep displaying the data.

Ease of programming for characters and graphics.

2.4 LIGHT EMITTING DIODE

A light-emitting diode (LED) is a semiconductor diode that emits

incoherent narrow spectrum light when electrically biased in the forward direction of the

pn-junction, as in the common LED circuit. This effect is a form of electroluminescence.

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Like a normal diode, the LED consists of a chip of semi-conducting material

impregnated, or doped, with impurities to create a p-n junction. As in other diodes,

current flows easily from the p-side, or anode, to the n-side, or cathode, but not in the

reverse direction. Charge-carrierselectrons and holesflow into the junction from

electrodes with different voltages. When an electron meets a hole, it falls into a lower

energy level, and releases energy in the form of a photon.

23
http://en.wikipedia.org/wiki/Diodehttp://en.wikipedia.org/wiki/Doping_(semiconductor)http://en.wikipedia.org/wiki/P-n_junctionhttp://en.wikipedia.org/wiki/Anodehttp://en.wikipedia.org/wiki/Cathodehttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Energy_levelhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Diodehttp://en.wikipedia.org/wiki/Doping_(semiconductor)http://en.wikipedia.org/wiki/P-n_junctionhttp://en.wikipedia.org/wiki/Anodehttp://en.wikipedia.org/wiki/Cathodehttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Energy_levelhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Photon

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The wavelength of the light emitted, and therefore its color, depends on

theband gap energy of the materials forming the p-n junction. In silicon orgermanium

diodes, the electrons and holes recombine by a non-radiative transition which produces

no optical emission, because these are indirect band gap materials. The materials used for

the LED have a direct band gap with energies corresponding to near-infrared, visible or

near-ultraviolet light.

LED development began with infrared and red devices made with gallium

arsenide. Advances in materials science have made possible the production of devices

with ever-shorter wavelengths, producing light in a variety of colors.

LEDs are usually built on an n-type substrate, with an electrode attached

to the p-type layer deposited on its surface. P-type substrates, while less common, occur

as well. Many commercial LEDs, especially GaN/InGaN, also use sapphire substrate.

Most materials used for LED production have very high refractive indices.

This means that much light will be reflected back in to the material at the material/air

surface interface. Therefore Light extraction in LEDs is an important aspect of LED

production, subject to much research and development.

Solid state devices such as LEDs are subject to very limited wear and tear

if operated at low currents and at low temperatures. Many of the LEDs produced in the

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1970s and 1980s are still in service today. Typical lifetimes quoted are 25,000 to 100,000

hours but heat and current settings can extend or shorten this time significantly.

Conventional LEDs are made from a variety of inorganic semiconductor

materials; the following table shows the available colors with wavelength range and

voltage drop.

Color Wavelength (nm) Voltage (V)

Infrared > 760 V < 1.9

Red 610 < < 760 1.63 < V < 2.03

Orange 590 < < 610 2.03 < V < 2.10

Yellow 570 < < 590 2.10 < V < 2.18

Green 500 < < 570 1.9 < V < 4.0

Blue 450 < < 500 2.48 < V < 3.7

Violet 400 < < 450 2.76 < V < 4.0

Purple multiple types 2.48 < V < 3.7

Ultraviolet < 400 3.1 < V < 4.4

White Broad spectrum V = 3.5

2.4.1 ADVANTAGES OF LEDS:

LEDs have many advantages over other technologies like lasers. As compared to

laser diodes or IR sources

LEDs are conventional incandescent lamps. For one thing, they don't have a

filament that will burn out, so they last much longer. Additionally, their small

plastic bulb makes them a lot more durable. They also fit more easily into modern

electronic circuits.

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The main advantage is efficiency. In conventional incandescent bulbs, the light-

production process involves generating a lot of heat (the filament must be

warmed). Unless you're using the lamp as a heater, because a huge portion of the

available electricity isn't going toward producing visible light.

LEDs generate very little heat. A much higher percentage of the electrical power

is going directly for generating light, which cuts down the electricity demands

considerably.

LEDs offer advantages such as low cost and long service life. Moreover LEDs

have very low power consumption and are easy to maintain.

2.4.2 DISADVANTAGES OF LEDS:

LEDs performance largely depends on the ambient temperature of the operating

environment.

LEDs must be supplied with the correct current.

LEDs do not approximate a "point source" of light, so cannot be used in

applications needing a highly collimated beam.

But the disadvantages are quite negligible as the negative properties of LEDs do not

apply and the advantages far exceed the limitations.

\

2.5 KIEL SOFTWARE

Many companies provide the 8051 assembler, some of them provide

shareware version of their product on the Web, Kiel is one of them. We can download

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them from their Websites. However, the size of code for these shareware versions is

limited and we have to consider which assembler is suitable for our application.

2.5.1 KIEL U VISION2:

This is an IDE (Integrated Development Environment) that helps you

write, compile, and debug embedded programs. It encapsulates the following

components:

A project manager

A make facility

Tool configuration

Editor

A powerful debugger

To get start here are some several example programs

2.5.2 BUILDING AN APPLICATION IN UVISION2:

To build (compile, assemble, and link) an application in uVision2, you must:

Select ProjectOpen Project

(For example, \C166\EXAMPLES\HELLO\HELLO.UV2)

Select Project - Rebuild all target files or Build target. UVision2 compiles,

assembles, and links the files in your project.

2.5.3 CREATING YOUR OWN APPLICATION IN UVISION2:

To create a new project in uVision2, you must:

Select Project - New Project.

Select a directory and enter the name of the project file.

Select Project - Select Device and select an 8051, 251, or C16x/ST10

device from the Device

Database

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Create source files to add to the project.

Select Project - Targets, Groups, and Files. Add/Files, select Source

Group1, and add the source files to the project.

Select Project - Options and set the tool options. Note when you select the

target device from the Device Database all-special options are set automatically. You

only need to configure the memory map of your target hardware. Default memory model

settings are optimal for most.

2.5.4APPLICATIONS:

Select Project - Rebuild all target files or Build target.

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2.5.5 DEBUGGING AN APPLICATION IN UVISION2:

To debug an application created using uVision2, you must:

Select Debug - Start/Stop Debug Session.

Use the Step toolbar buttons to single-step through your program. You

may enter G, main in the Output Window to execute to the main C function.

Open the Serial Window using the Serial #1 button on the toolbar.

Debug your program using standard options like Step

3.COMPONENT DESCRIPTION

3.1AT89S52

SELECTION OF MICROCONTROLLER:

As we know that there so many types of micro controller families that are

available in the market.

Those are

1) 8051 Family

2) AVR microcontroller Family

3) PIC microcontroller Family

04) ARM Family

Basic 8051 family is enough for our application; hence we are not concentrating

on higher end controller families.

In order to fulfill our application basic that is AT89C51 controller is enough. But

still we selected AT89S52 controller because of inbuilt ISP (in system programmer)

option.There are minimum six requirements for proper operation of microcontroller.

Those are:

1) power supply section

2) pull-ups for ports (it is must for PORT0)

3) Reset circuit

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4) Crystal circuit

5) ISP circuit (for program dumping)

6) EA/VPP pin is connected to Vcc.

3.1.1 FEATURES:

Compatible with MCS-51 Products

8K Bytes of In-System Programmable (ISP) Flash Memory

-Endurance: 1000 Write/Erase Cycles

4.0V to 5.5V Operating Range

Fully Static Operation: 0 Hz to 33 MHz

Three-level Program Memory Lock

256 x 8-bit Internal RAM

32 Programmable I/O Lines

Three 16-bit Timer/Counters

Eight Interrupt Sources

Full Duplex UART Serial Channel

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3.1.3PIN CONFIGURATION 40-lead PDIP:

fig. 3.1

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3.1.4 ARCHITECTURE:

Fig.3.2

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3.1.5PIN DESCRIPTION:

VCC: Supply voltage.

GND: Ground.

Port 0:

Port 0 is an 8-bit open drain bidirectional I/O port. As an output port, each

pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as

high-impedance inputs.

Port 0 can also be configured to be the multiplexed low-order address/data

bus during accesses to external program and data memory. In this mode, P0 has internal

pull-ups.

Port 0 also receives the code bytes during Flash programming and outputs

the code bytes during program verification. External pull-ups are required during

program verification.

Port 1:

Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1

output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they

are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins

that are externally being pulled low will source current (IIL) because of the internal pull-

ups.

In addition, P1.0 and P1.1 can be configured to be the timer/counter 2

external count input (P1.0/T2) and the timer/counter 2 trigger input (P1.1/T2EX),

respectively, as shown in the following table.

Port 1 also receives the low-order address bytes during Flash

programming and verification.

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Port Pin Alternate Functions

P1.0 T2(external count to Timer/Counter 2), clock-out

P1.1 T2EX(Timer/Counter 2 capture/reload trigger and direction control)

P1.5 MOSI (used for In-System Programming)

P1.6 MISO(used for In-System Programming)

P1.7 SCK(used for In-System Programming)

Port 2:Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2



that are externally being pulled low will source current (IIL) because of the internal pull-ups.

Port 2 emits the high-order address byte during fetches from external

program memory and during accesses to external data memory that uses 16-bit addresses

(MOVX @ DPTR). In this application, Port 2 uses strong internal pull-ups when emitting

1s. During accesses to external data memory that uses 8-bit addresses (MOVX @ RI),

Port 2 emits the contents of the P2 Special Function Register.

Port 2 also receives the high-order address bits and some control signals

during Flash programming and verification.

Port 3:

Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3



that are externally being pulled low will source current (IIL) because of the pull-ups.

Port 3 receives some control signals for Flash programming and

verification.

Port 3 also serves the functions of various special features of the

AT89S52, as shown in the following table.

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RST:

Reset input. A high on this pin for two machine cycles while the oscillator

is running resets the device. This pin drives high for 98 oscillator periods after the

Watchdog times out. The DISRTO bit in SFR AUXR (address 8EH) can be used to

disable this feature. In the default state of bit DISRTO, the RESET HIGH out feature is

enabled.

:

Address Latch Enable (ALE) is an output pulse for latching the low byte

of the address during accesses to external memory. This pin is also the program pulse

input (PROG bar) during Flash programming. In normal operation, ALE is emitted at a

constant rate of 1/6 the oscillator frequency and may be used for external timing or

clocking purposes. Note, however, that one ALE pulse is skipped during each access to

external data memory. If desired, ALE operation can be disabled by setting bit 0 of SFR

location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction.

37

Port Pin Alternate FunctionsP3.0 RXD (serial Input port)

P3.1 TXD (serial output port)

P3.2 INT0 bar (external Interrupt 0)

P3.3 INT1 bar (external Interrupt 1)P3.4 T0 (timer 0 external Input)

P3.5 T1 (timer 1 external input)

P3.6 WR bar (external data memory write strobe)

P3.7 RD bar (external data memory read strobe)

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Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the

microcontroller is in external execution mode.

:

Program Store Enable (PSEN BAR) is the read strobe to external program

memory.

When the AT89S52 is executing code from external program memory,

PSEN BAR is activated twice each machine cycle, except that two PSEN BAR

activations are skipped during each access to external data memory.

:

External Access Enable. EA BAR must be strapped to GND in order to

enable the device to fetch code from external program memory locations starting at

0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA BAR will be

internally latched on reset.

EA BAR should be strapped to VCC for internal program executions.

This pin also receives the 12-volt programming enable voltage (VPP) during Flash

programming.

XTAL1:

Input to the inverting oscillator amplifier and input to the internal clock

operating circuit.

XTAL2:

Output from the inverting oscillator amplifier

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3.1.6 BLOCK DIAGRAM:

Fig.3.3

3.1.7 Oscillator Characteristics:

XTAL1 and XTAL2 are the input and output, respectively, of an inverting

amplifier that can be configured for use as an on-chip oscillator, as shown in Figure.

Either a quartz crystal or ceramic resonator may be used. To drive the device from an

external clock source, XTAL2 should be left unconnected while XTAL1 is driven, as

39

INTERRUPTCONTROL

ON-CHIP

ROM FORPROGRAM

CODE

ON-CHIPRAM

TIMER/COUNTER

TIMER 1

TIMER 0

OSC

BUSCONTROL

4 I/OPORTS

SERIALPORT

CPU

EXTERNALINTERRUPTS

COUNTERINPUTS

P0 P1 P2 P3 Tx Rx

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shown in below Figure There are no requirements on the duty cycle of the external clock

signal, since the input to the internal clocking circuitry is through a divide-by-two flip-

flop, but minimum and maximum voltage high and low time specifications must be

observed.[2]

Idle Mode:

In idle mode, the CPU puts itself to sleep while all the on-chip peripherals

remain active. The mode is invoked by software. The content of the on-chip RAM and all

the special functions registers remain unchanged during this mode. The idle mode can be

terminated by any enabled interrupt or by a hardware reset.

Power-down Mode:

In the Power-down mode, the oscillator is stopped, and the instruction that

invokes Power-down is the last instruction executed. The on-chip RAM and Special

Function Registers retain their values until the Power-down mode is terminated. Exit

from Power-down mode can be initiated either by a hardware reset or by an enabled

external interrupt. Reset redefines the SFRs but does not change the on-chip RAM. The

reset should not be activated before VCC is restored to its normal operating level and

must be held active long enough to allow the oscillator to restart and stabilize.[3]

Oscillator Connections:

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Fig.3.4

C1, C2 = 30 pF 10 pF for Crystals

= 40 pF 10 pF for Ceramic Resonators

3.2 DS1307

3.2.1 FEATURES OF DS1307:

Real-time clock (RTC) counts seconds, minutes, hours, date of the month, month,

day of the week, and year with leap-year compensation valid up to 2100.

56-byte, battery-backed, nonvolatile (NV) RAM for data storage.

Two-wire serial interface.

Programmable square wave output signal.

Automatic power-fail detect and switch circuitry.

Consumes less than 500nA in battery backup mode with oscillator running.

Optional industrial temperature range: 40C to +85C

Available in 8-pin DIP or SOIC.

Underwriters Laboratory (UL) recognized.

3.2.2 PIN ASSIGNMENT:

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Fig.3.5


VCC : Primary Power SupplyX1, X 2 : 32.768 kHz Crystal Connection

VBAT : +3V Battery Input

GND : Ground

SDA : Serial Data

SCL : Serial Clock

SQW/OUT : Square Wave/Output Driver

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3.2.4 DESCRIPTION:

The DS1307 Serial Real-Time Clock is a low-power; full binary-coded

decimal (BCD) clock/calendar plus 56 bytes of NV SRAM. Address and data are

transferred serially via a 2-wire, bi-directional bus. The clock/calendar provides seconds,

minutes, hours, day, date, month, and year information. The end of the month date is

automatically adjusted for months with fewer than 31 days, including corrections for leap

year. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator.The DS1307 has a built-in power sense circuit that detects power failures and

automatically switches to the battery supply.[1]

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3.2.5 TYPICAL OPERATING CIRCUIT:

Fig.3.6

3.2.6 OPERATION:

The DS1307 operates as a slave device on the serial bus. Access is

obtained by implementing a START condition and providing a device identification code

followed by a register address. Subsequent registers can be accessed sequentially until a

STOP condition is executed. When VCC falls below 1.25 x VBAT the device terminates

an access in progress and resets the device address counter. Inputs to the device will not

be recognized at this time to prevent erroneous data from being written to the device from

an out of tolerance system. When VCC falls below VBAT the device switches into a low-

current battery backup mode. Upon power-up, the device switches from battery to VCC

when VCC is greater than VBAT + 0.2V and recognizes inputs when VCC is greater than

1.25 x VBAT. The above diagram shows the main elements of the serial RTC.

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3.2.7 DS1307 BLOCK DIAGRAM:

Fig.3.7

SIGNAL DESCRIPTIONS:

VCC, GND:

DC power is provided to the device on these pins. VCC is the +5V input.

When 5V is applied within normal limits, the device is fully accessible and data can be

written and read. When a 3V battery is connected to the device and VCC is below 1.25 x

VBAT, reads and writes are inhibited. However, the timekeeping function continues

unaffected by the lower input voltage. As VCC falls below VBAT the RAM and

timekeeper are switched over to the external power supply (nominal 3.0V DC) at VBAT.

VBAT:

Battery input for any standard 3V lithium cell or other energy source. Battery

voltage must be held between 2.0V and 3.5V for proper operation. The nominal write

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protect trip point voltage at which access to the RTC and user RAM is denied is set by

the internal circuitry as 1.25 x VBAT nominal. A lithium battery with 48mAhr or greater

will back up the DS1307 for more than 10 years in the absence of power at 25C. UL

recognized to ensure against reverse charging current when used in conjunction with a

lithium battery.

SCL (Serial Clock Input):

SCL is used to synchronize data movement on the serial interface.

SDA (Serial Data Input/Output):

SDA is the input/output pin for the 2-wire serial interface. The SDA pin is

open drain which requires an external pull up resistor.

SQW/OUT (Square Wave/Output Driver):

When enabled, the SQWE bit set to 1, the SQW/OUT pin outputs one of

four square wave frequencies (1Hz, 4 kHz, 8 kHz, 32 kHz). The SQW/OUT pin is open

drain and requires an external pull-up resistor. SQW/OUT will operate with either Vcc or

Vbat applied.

X1, X2:

Connections for a standard 32.768 kHz quartz crystal. The internal oscillator

circuitry is designed for operation with a crystal having a specified load capacitance (CL)

of 12.5pF.

CLOCK ACCURACY:

The accuracy of the clock is dependent upon the accuracy of the crystal

and the accuracy of the match between the capacitive load of the oscillator circuit and the

capacitive load for which the crystal was trimmed. Additional error will be added by

crystal frequency drift caused by temperature shifts. External circuit noise coupled into

the oscillator circuit may result in the clock running fast.

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RTC AND RAM ADDRESS MAP:

The address map for the RTC and RAM registers of the DS1307 isshown below. The RTC registers are located in address locations 00h to 07h. The RAM

registers are located in address locations 08h to 3Fh. During a multi-byte access, when

the address pointer reaches 3Fh, the end of RAM space, it wraps around to location 0 the

beginning of the clock.

CLOCK AND CALENDAR:

The time and calendar information is obtained by reading the appropriate

register bytes.

The RTC registers are illustrated in the below figure. The time and calendar

are set or initialized by writing the appropriate register bytes. The contents of the time

and calendar registers are in the BCD format. Bit 7 of register 0 is the clock halt (CH) bit.

When this bit is set to a 1, the oscillator is disabled. When cleared to a 0, the oscillator is

enabled.

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The DS1307 can be run in either 12-hour or 24-hour mode. Bit 6 of the hours

register is defined as the 12- or 24-hour mode select bit. When high, the 12-hour mode is

selected. In the 12-hour mode, bit 5 is the AM/PM bit with logic high being PM. In the

24-hour mode, bit 5 is the second 10 hour bit (20- 23 hours).

On a 2-wire START, the current time is transferred to a second set of

registers. The time information is read from these secondary registers, while the clock

may continue to run. This eliminates the need to reread the registers in case of an update

of the main registers during a read.

DS1307 TIMEKEEPER REGISTERS:

.Fig.3.8

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CONTROL REGISTER:

The DS1307 control register is used to control the operation of the SQW/OUT

pin.

OUT (Output control):

This bit controls the output level of the SQW/OUT pin when the square wave

output is disabled. If SQWE = 0, the logic level on the SQW/OUT pin is 1 if OUT = 1

and is 0 if OUT = 0.

SQWE (Square Wave Enable):

This bit, when set to logic 1, will enable the oscillator output. The frequency of

the square wave output depends upon the value of the RS0 and RS1 bits. With the square

wave output set to 1Hz, the clock registers update on the falling edge of the square wave.

RS (Rate Select):

These bits control the frequency of the square wave output when the square wave

output has been enabled. Table below lists the square wave frequencies that can be

selected with the RS bits.

SQUAREWAVE OUTPUT FREQUENCY:

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2-WIRE SERIAL DATA BUS:

The DS1307 supports a bi-directional, 2-wire bus and data transmission

protocol. A device that sends data onto the bus is defined as a transmitter and a device

receiving data as a receiver. The device that controls the message is called a master. The

devices that are controlled by the master are referred to as slaves. The bus must be

controlled by a master device that generates the serial clock (SCL), controls the bus

access, and generates the START and STOP conditions. The DS1307 operates as a slave

on the 2-wire bus. A typical bus configuration using this 2-wire protocol is show in

Figure below.

TYPICAL 2-WIRE BUS CONFIGURATION:

Fig.3.9

Data transfer may be initiated only when the bus is not busy.

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During data transfer, the data line must remain stable whenever the clock line is

HIGH. Changes in the data line while the clock line is high will be interpreted as control

signals.

Accordingly, the following bus conditions have been defined:

BUS NOT BUSY:

Both data and clock lines remain HIGH.

START DATA TRANSFER:

A change in the state of the data line, from HIGH to LOW, while the clock is

HIGH, defines a START condition.

STOP DATA TRANSFER: A change in the state of the data line, from LOW to HIGH, while the clock line

is HIGH, defines the STOP condition.

DATA VALID:

The state of the data line represents valid data when, after a START condition,

the data line is stable for the duration of the HIGH period of the clock signal. The data on

the line must be changed during the LOW period of the clock signal. There is one clock

pulse per bit of data.

Each data transfer is initiated with a START condition and terminated with a

STOP condition. The number of data bytes transferred between START and STOP

conditions is not limited, and is determined by the master device. The information is

transferred byte-wise and each receiver acknowledges with a ninth bit. Within the 2-wire

bus specifications a regular mode (100 kHz clock rate) and a fast mode (400 kHz clock

rate) are defined. The DS1307 operates in the regular mode (100 kHz) only.

ACKNOWLEDGE:

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Each receiving device, when addressed, is obliged to generate acknowledge

after the reception of each byte. The master device must generate an extra clock pulse

which is associated with this acknowledge bit.

A device that acknowledges must pull down the SDA line during the

acknowledge clock pulse in such a way that the SDA line is stable LOW during the

HIGH period of the acknowledge related clock pulse. Of course, setup and hold times

must be taken into account. A master must signal an end of data to the slave by not

generating an acknowledge bit on the last byte that has been clocked out of the slave. In

this case, the slave must leave the data line HIGH to enable the master to generate the

STOP condition.

DATA TRANSFER ON 2-WIRE SERIAL BUS:

Fig.3.10Depending upon the state of the R/Wbit, two types of data transfer are possible:

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Data transfer from a master transmitter to a slave receiver:

The first byte transmitted by the master is the slave address. Next follows a

number of data bytes. The slave returns an acknowledge bit after each received byte. Data

is transferred with the most significant bit (MSB) first.

Data transfer from a slave transmitter to a master receiver:

The first byte (the slave address) is transmitted by the master. The slave then

returns an acknowledge bit. This is followed by the slave transmitting a number of data

bytes. The master returns an acknowledge bit after all received bytes other than the last

byte. At the end of the last received byte, a not acknowledge is returned. The master

device generates all of the serial clock pulses and the START and STOP conditions. A

transfer is ended with a STOP condition or with a repeated START condition. Since a

repeated START condition is also the beginning of the next serial transfer, the bus will

not be released. Data is transferred with the most significant bit (MSB) first.

The DS1307 may operate in the following two modes:

Slave receiver mode (DS1307 write mode):

Serial data and clock are received through SDA and SCL. After each byte is

received an acknowledge bit is transmitted. START and STOP conditions are recognized

as the beginning and end of a serial transfer. Address recognition is performed by

hardware after reception of the slave address and *direction bit. The address byte is the

first byte received after the start condition is generated by the master. The address byte

contains the 7 bit DS1307 address, which is 1101000, followed by the *direction bit

(R/W) which, for a write, is a 0. After receiving and decoding the address byte the device

outputs an acknowledge on the SDA line. After the DS1307 acknowledges the slave

address + write bit, the master transmits a register address to the DS1307. This will set

the register pointer on the DS1307. The master will then begin transmitting each byte of

data with the DS1307 acknowledging each byte received. The master will generate a stop

condition to terminate the data write.

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DATA WRITE SLAVE RECEIVER MODE:

Slave transmitter mode (DS1307 read mode):

The first byte is received and handled as in the slave receiver mode. However,

in this mode, the *direction bit will indicate that the transfer direction is reversed. Serial

data is transmitted on SDA by the DS1307 while the serial clock is input on SCL.

START and STOP conditions are recognized as the beginning and end of a serial transfer

.The address byte is the first byte received after the start condition is generated by the

master. The address byte contains the 7-bit DS1307 address, which is 1101000, followed

by the *direction bit (R/W) which, for a read, is a 1. After receiving and decoding the

address byte the device inputs an acknowledge on the SDA line. The DS1307 then begins

to transmit data starting with the register address pointed to by the register pointer. If the

register pointer is not written to before the initiation of a read mode the first address that

is read is the last one stored in the register pointer. The DS1307 must receive a not

acknowledge to end a read.[4]

DATA READ SLAVE TRANSMITTER MODE:

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SELECTION OF AND GATE:In this application we are using interrupt mechanism to find which switch is

pressed. In this project I am using four switches to select the particular cell phone to

charging. The four switches are connected to the AND gate. The output of AND gate isconnected to the interrupt pin of controller. In this application I am using 74LS21 IC it

has two AND gates, each gate has four inputs and one output

3.3 74LS21(DUAL 4-INPUT AND GATE

3.3.1GENERAL DESCRIPTION:

This device contains two independent gates each of which performs the logic

AND function.


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Fig 3.11

3.3.3 CONNECTION DIAGRAM:

Fig 3.12

3.3.4 FUNCTION TABLE:

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[5]

H - High Logic Level

L - Low Logic Level

X - Either Low or High Logic Level

3.3.5 OPERATING CODITIONS:

3.4 TRANSISTOR AS A SWITCH

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The transistor is the fundamental building block of modern electronic devices,

and its presence is ubiquitous in modern electronic systems.

Because a transistor's collector current is proportionally limited by its base

current, it can be used as a sort of current-controlled switch. A relatively small flow of

electrons sent through the base of the transistor has the ability to exert control over a

much larger flow of electrons through the collector.

When used as an AC signal amplifier, the transistors Base biasing voltage is

applied so that it operates within its "Active" region and the linear part of the output

characteristics curves are used. However, both the NPN & PNP type bipolar transistors

can be made to operate as an "ON/OFF" type solid state switch for controlling high

power devices such as motors, solenoids or lamps. If the circuit uses the Transistor as a

Switch, then the biasing is arranged to operate in the output characteristics curves seen

previously in the areas known as the "Saturation" and "Cut-off" regions as shown

below.[6]

TRANSISTORCURVES:

Fig 3.13

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The shaded area at the bottom represents the "Cut-off" region. Here the operating

conditions of the transistor are zero input base current (Ib), zero output collector current

(Ic) and maximum collector voltage (Vce) which results in a large depletion layer and no

current flows through the device. The transistor is switched "Fully-OFF". The lighter blue

area to the left represents the "Saturation" region. Here the transistor will be biased so

that the maximum amount of base current is applied, resulting in maximum collector

current flow and minimum collector emitter voltage which results in the depletion layer

being as small as possible and maximum current flows through the device. The transistor

is switched "Fully-ON". Then we can summarize this as:

Cut-off Region: Both junctions are Reverse-biased, Base current is zero or very

small resulting in zero Collector current flowing, the device is switched fully "OFF". Saturation Region: Both junctions are Forward-biased, Base current is high

enough to give a Collector-Emitter voltage of 0v resulting in maximum Collector

current flowing, the device is switched fully "ON".

3.4.1 TRANSISTOR SWITCHING CIRCUIT:

Fig 3.14

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An NPN Transistor as a switch being used to operate a relay is given above. With

inductive loads such as relays or solenoids a flywheel diode is placed across the load to

dissipate the back EMF generated by the inductive load when the transistor switches

"OFF" and so protect the transistor from damage. If the load is of a very high current or

voltage nature, such as motors, heaters etc, then the load current can be controlled via a

suitable relay as shown.

The circuit resembles that of the Common Emitter circuit we looked at in the

previous tutorials. The difference this time is that to operate the transistor as a switch the

transistor needs to be turned either fully "OFF" (Cut-off) or fully "ON" (Saturated). An

ideal transistor switch would have an infinite resistance when turned "OFF" resulting in

zero current flow and zero resistance when turned "ON", resulting in maximum current

flow. In practice when turned "OFF", small leakage currents flow through the transistor

and when fully "ON" the device has a low resistance value causing a small saturation

voltage (Vce) across it. In both the Cut-off and Saturation regions the power dissipated

by the transistor is at its minimum.[7]

To make the Base current flow, the Base input terminal must be made more

positive than the Emitter by increasing it above the 0.7 volts needed for a silicon device.

By varying the Base-Emitter voltage Vbe, the Base current is altered and which in turn

controls the amount of Collector current flowing through the transistor as previously

discussed. When maximum Collector current flows the transistor is said to be saturated.

The value of the Base resistor determines how much input voltage is required and

corresponding Base current to switch the transistor fully "ON".

Transistor switches are used for a wide variety of applications such as interfacing

large current or high voltage devices like motors, relays or lamps to low voltage digital

logic IC's or gates like AND Gates or OR Gates.[8]

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3.5 SPDT RELAY

POWER SUPPLY SECTION:

In-order to work with any components basic requirement is power supply. In this

section there is a requirement one voltage level i.e. 5V DC power supply.

Now the aim is to design the power supply section which converts 230V AC in to

5V DC. Since 230V AC is too high to reduce it to directly 5V DC, therefore we need a

step-down transformer that reduces the line voltage to certain voltage that will help us to

convert it in to a 5V DC. Considering the efficiency factor of the bridge rectifier, we

came to a conclusion to choose a transformer, whose secondary voltage is 3 to 4 V higher

than the required voltage i.e. 5V. For this application 0-9V transformers is used, since it

is easily available in the market.

The output of the transformer is 9V AC; it feed to rectifier that converts AC to

pulsating DC. As we all know that there are 3 kind of rectifiers that is

1) half wave

2) Full wave and

3) Bridge rectifier

Here we short listed to use Bridge rectifier, because half wave rectifier has we

less in efficiency. Even though the efficiency of full wave and bridge rectifier are the

same, since there is no requirement for any negative voltage for our application, we gone

with bridge rectifier.

Since the output voltage of the rectifier is pulsating DC, in order to convert it into

pure DC we use a high value (1000UF/1500UF) of capacitor in parallel that acts as a

filter. The most easy way to regulate this voltage is by using a 7805 voltage regulator,

whose output voltage is constant 5V DC irrespective of any fluctuation in line voltage.

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PORT0 is open collector thats why we are using pull-up resistor which makes

PORT0 as an I/O port. Reset circuit is used to reset the microcontroller. Crystal circuit is

used for the microcontroller for timing pluses. In this project we are not using external

memory thats why EA/VPP pin in the microcontroller is connected to Vcc that indicates

internal memory is used for this application.

A relay is an electrically operated switch. Many relays use an electromagnet to

operate a switching mechanism, but other operating principles are also used. Relays find

applications where it is necessary to control a circuit by a low-power signal, or where

several circuits must be controlled by one signal. The first relays were used in long

distance telegraph circuits, repeating the signal coming in from one circuit and re-

transmitting it to another. Relays found extensive use in telephone exchanges and early

computers to perform logical operations. A type of relay that can handle the high power

required to directly drive an electric motor is called a contactor. Solid-state relays control

power circuits with no moving parts, instead using a semiconductor device triggered by

light to perform switching. Relays with calibrated operating characteristics and

sometimes multiple operating coils are used to protect electrical circuits from overload or

faults; in modern electric power systems these functions are performed by digital

instruments still called "protection relays".[9]

SPDT RELAY:

(Single Pole Double Throw Relay) an electromagnetic switch, consist of a

coil (terminals 85 & 86), 1 common terminal (30), 1 normally closed terminal (87a), and

one normally open terminal (87).

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When the coil of the relay is at rest (not energized), the common terminal

(30) and the normally closed terminal (87a) have continuity. When the coil is energized,

the common terminal (30) and the normally open terminal (87) have continuity.

The diagram below first shows the relay at rest, with the coil not

energized. The diagram below second shows the relay with the coil energized. As you

can see the coil is an electromagnet that causes the arm that is always connected to the

common (30) to pivot when energized whereby contact is broken from the normally

closed terminal (87a) and made with the normally open terminal (87).

When energizing the coil of a relay, polarity of the coil does not matter

unless there is a diode across the coil. If a diode is not present, you may attach positive

voltage to either terminal of the coil and negative voltage to the other, otherwise you

must connect positive to the side of the coil that the cathode side (side with stripe) of the

diode is connected and negative to side of the coil that the anode side of the diode is

connected.[10]

Diodes are most often used across the coil to provide a path for current

when the current path to the relay is interrupted (i.e. switched off, coil no longer

energized). This allows the coil field to collapse without the voltage spike that would

otherwise be generated. The diode protects switch or relay contacts and other circuits that

may be sensitive to voltage spikes.

Here's are some circuit diagrams for driving relays from a microcontroller.

Make sure you're using a 5-volt relay (this refers to the coil, not the load circuit), and

make sure that the relay has a high enough rating for the load that you're driving.

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This circuit is necessary if you are using a relay with a coil that needs more power than

the microcontroller can supply (this includes most miniature electromechanical relays)

[11]

Fig 3.15

3.6 ISP PROGRAMMER

In-System Programming (abbreviated ISP) is the ability of someprogrammable

logic devices, microcontrollers, and other programmable electronic chips to be

programmed while installed in a complete system, rather than requiring the chip to be

programmed prior to installing it into the system. Otherwise, In-system programming

means that the program and/or data memory can be modified without disassembling the

embedded system to physically replace memory.

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The primary advantage of this feature is that it allows manufacturers of electronic

devices to integrate programming and testing into a single production phase, rather than

requiring a separate programming stage prior to assembling the system. This may allow

manufacturers to program the chips in their own system's production line instead of

buying preprogrammed chips from a manufacturer or distributor, making it feasible to

apply code or design changes in the middle of a production run.[12]

ISP (In System Programming) will provide a simple and affordable home made

solution to program and debug your microcontroller based project.

Normally, the flash memory of an ATMEL microcontroller is programmed using

a parallel interface, which consists of sending the data byte by byte (using 8 independent

lines for the data, and another bunch of lines for the address, the control word and clock

input).

Many members of the Maxim 8051-based microcontroller family support in-

system programming via a commonly available RS-232 serial interface. The serial

interface consists of pins SCK, MOSI (input) and MISO (output) and the RST pin, which

is normally used to reset the device.

ISP is performed using only 4 lines, and literally, data is transferred through 2

lines only, as in a I2C interface, where data is shifted in bit by bit though M OSI line,

with a clock cycle between each bit and the next (on the SCKline). MISO line is used

for reading and for code verification; it is only used to output the code from the FLASH

memory of the microcontroller.

The RST pin is also used to enable the 3 pins (MOSI, MISO and SCK) to be

used for ISP simply by setting RST to HIGH (5V), otherwise if RST is low (0V),

program start running and those three pins, are used normally as P1.5, P1.6 and P1.7.

After RST is set high, the Programming Enable instruction needs to be executed first

before other operations can be executed. Before a reprogramming sequence can occur, a

Chip Erase operation is required. The Chip Erase operation turns the content of every

memory location in the Code array into FFH

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Either an external system clock can be supplied at pin XTAL1 or a crystal

needs to be connected across pins XTAL1 and XTAL2. The maximum serial clock

(SCK) frequency should be less than 1/16 of the crystal frequency. With a 33 MHz

oscillator clock, the maximum SCK frequency is 2 MHz.[13]

G N D

I 4 A

G N

O 4 B

G N D

1 2

3 4

5 6

7 8

9 1 0

C O N N E C T O R D B 2 5

1 3

2 5

1 2

2 4

1 1

2 3

1 0

2 2

9

2 1

8

2 0

7

1 9

6

1 8

5

1 7

4

1 6

3

1 5

2

1 4

1

G N D

I 4 B

G A

1 0 0 K

G B

G

N

D

I 2 B

0 . 1 U F / 3 5 V

O 1 A

I 1 A

7 4 H C 2 4 4

2 0

1 9

1 8

1 7

1 6

1 5

1 4

1 3

1 2

1 1

1

2

3

4

5

6

7

8

9

1 0

O 2 A

V C

I 1 B

O 1 B

O 4 A

I 2 A

V C C

O 2 B

0 3 A

I 3 A

I 3 B

O 3 B

Fig 3.16

DB-25 Male pin description:

Pin no Name Direction Pin Description

1

2

GND

TXD

Shield Ground

Transmit Data

3 RXD Receive Data

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EXAMPLE: CONNECTING THE PROGRAMMER TO AN AT89S52

Fig 3.18

AT89S8252 microcontroller features an SPI port, through which on-chip Flash memory

and EEPROM may be programmed. To program the microcontroller, RST is held high

while commands, addresses and data are applied to the SPI port.

ATMEL ISP FLASH PROGRAMMER:

This is the software that will take the HEX file generated by whatever

compiler you are using, and send it - with respect to the very specific ISP transfer

protocol - to the microcontroller.

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This programmer was designed in view of to be flexible, economical and

easy to built, the programmer hardware uses the standard TTL series parts and no special

components are used. The programmer is interfaced with the PC parallel port and there is

no special requirement for the PC parallel port, so the older computers can also be used

with this programmer.

SUPPORTED DEVICES:

The programmer software presently supports the following devices

AT89C51 AT89S51 AT89C1051 UD87C51 AT89C52 AT89S52

AT89C2051 D87C52 AT89C55 AT89S53 AT89C4051 AT89C55WD

AT89S8252 AT89C51RC

Note: For 20 pin devices a simple interface adapter is required.

The ISP-3v0.zip file contains the main program and the I/O port driver for

Windows 2000 & XP. Place all files in the same folder, for win-95/98 use the "ISP-

Pgm3v0.exe"File, for win-2000 & XP use the "ISP-XP.bat" file. The main screen view of

the program is shown in fig below.

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Fig 3.9

Following are the main features of this software:

Read and write the Intel Hex file

Read signature, lock and fuse bits

Clear and Fill memory buffer

Verify with memory buffer

Reload current Hex file

Display buffer checksum

Program selected lock bits & fuses

Auto detection of hardware

The memory buffer contains both the code data and the EEPROM data for

the devices which have EEPROM memory. The EEPROM memory address in buffer is

started after the code memory, so it is necessary the hex file should contains the

EEPROM start address after the end of code memory last address.

i.e., for 90S2313 the start address for EEPROM memory is 0 x 800.

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4. SCHEMATIC DIAGRAM

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- +

B R I D G E R E C T I F I E R

1

4

3

2

P 1 . 1

S C L ( D S 1 3 0 7 )

s 1

D 6 ( L C D )

D 4 ( L C D )

X T A L 1

7 8 0 5 R E G U L A T O R1 3

V I N V O U T

s 2

1 K

G N D

N

V C C

1 1 . 0 5 9 2 M H z

A T 8 9 S 5 2

2 0

1 8

1 7

2 93 0

1 9

3 29

1 01 11 21 31 41 51 6

4 03 93 83 73 63 53 43 3

2 82 72 62 52 42 32 22 1

12345678

3 1

G N D

X T A L 2

( R D ) P 3 . 7

P S E N

A L E / P R O G

X T A L 1

P 0 . 7 / A D 7R S T

( R X D ) P 3 . 0( T X D ) P 3 . 1

( I N T 0 ) P 3 . 2( I N T 1 ) P 3 . 3( T 0 ) P 3 . 4( T 1 ) P 3 . 5( W R ) P 3 . 6

V C CP 0 . 0 / A D 0P 0 . 1 / A D 1P 0 . 2 / A D 2P 0 . 3 / A D 3P 0 . 4 / A D 4P 0 . 5 / A D 5P 0 . 6 / A D 6

P 2 . 7 / A 1 5P 2 . 6 / A 1 4P 2 . 5 / A 1 3P 2 . 4 / A 1 2P 2 . 3 / A 1 1P 2 . 2 / A 1 0

P 2 . 1 / A 9P 2 . 0 / A 8

( T 2 ) P 1 . 0( T 2 E X ) P 1 . 1P 1 . 2P 1 . 3P 1 . 4( M O S I ) P 1 . 5( M I S O ) P 1 . 6( S C K ) P 1 . 7

E A / V P P

P 2 . 7

P O W E R S U P P L Y ( 5 V D C )

V C C

3 3 0 o h m

D 7 ( L C D )

P 0 . 6

S D A ( D S 1 3 0 7 )

V C CR S ( L C D )

Y 1 ( 7 4 L S 2 1 N )

G N D

V C C

2

P 0 . 3

A 1

B 1

N C

C 1

D 1

Y 1

G N D Y 2

A 2

B 2

N C

C 2

D 2

V C C

7 4 L S 2 1 N

1

2

4

3

5

6

7 8

9

1 0

1 1

1 2

1 3

1 4

2

3

0

V

A

C

P 2 . 5

L E D

A 1 ( 7 4 L S 2 1 N )

V C C

12

8 . 2 K

( 9 V , 1 A M P )

V C C = 5 V

P 1 . 7

P

2 3 0 V , A . C

12

F R O M I S P ( 2 )

A T 8 9 S 5 2 I S P

P 2 . 4

P 0 . 4

F R O M I S P ( 1 0 )

G N D

B U L B

B 1 ( 7 4 L S 2 1 N )

R

8

R

7

R

6

R

5

R

4

R

3

R

2

R

1C

1 0 K P U L L U P

9 8 7 6 5 4 3 2 1

3 3 0 o h m

P 0 . 5

G N D

V C C

D 1 ( 7 4 L S 2 1 N )

V C C

R E L A Y C I R C U I T

3 3 p f

P 1 . 5

P 2 . 6

P 2 . 0

G N D

1 0 4 p f

G N D

D S 1 3 0 7

7

5

1

2

63

8

4

S Q W / O U T

S D A

X 1

X 2

S C LV B A T

V C C

G N D

V C C

R E S E T

1 0 K2 2 0 o h m

I

1 0 0 0 u f / 3 5 V

P 0 . 1

I N T 0 ( P 3 . 2 )

P

D 5 ( L C D )

F R O M I S P ( 6 ) & R S T

L C D

V C C = 5 V

3 3 p f

s 3

A T 8 9 S 5 2 C R Y S T A L

R E L A Y S P D T

35

412

G N D

1 23 45 67 89 1 0

1 0 u f / 6 3 VC

G N D

C 1 ( 7 4 L S 2 1 N )

G N DX T A L 1

R E L A Y

3

2

.

7

6

8

K

H

Z

3

V

B

A

T

T

E

R

Y

T R I M P O T

5 K

E N ( L C D )

F R O M I S P ( 4 )

G N DV C CV E ER SR WE ND 0

D 3

D 2

D 4D 5D 6D 7

D 1

L E D +

L E D -

123456789

1 01 11 21 31 41 51 6

R

8

R

7

R

6

R

5

R

4

R

1

R

2

R

3C

1 0 K P U L L U P

123456789

X T A L 2

B C 1 0 9

P 1 . 6

G N D

V C C = 5 V

3 3 p f

s 4

R S TS

G N D

4 . 7 K

R S T

V C C

I N 4 0 0 7

P 2 . 1

G N D

G N D

S

W

IT

C

H

R

8

R

7

R

6

R

5

R

4

R

1

R

2

R

3C

1 0 K P U L L U P

1 2 3 4 5 6 7 8 9

P 0 . 7

T R A N S F O R M E R

X T A L 2

1 0 K

V C C

G N D

5. CODING

/**HEADER FILES**/

#include

#include

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/**LCD CONNECTIONS**/

#define LCD P0

/**VARIABLES DEFINITION**/

#define DELAY _nop_();

#define CLKHIGH clk=1;

#define CLKLOW clk=0;

#define DATAHIGH dat=1;

#define DATALOW dat=0;

/**RTC & EEPROM PIN CONNECTIONS**/

sbit clk=P2^1;

sbit dat=P2^0;

/** SWITCHES CONNECTIONS **/

sbit SEL = P2^7;

sbit INC = P2^6;

sbit DEC = P2^5;

sbit EXIT = P2^4;

/**DEVICE CONNECTION**/

sbit relay = P1^1;

/**VARIABLES DECLARATION**/

bit busy,noack,busfault;

unsigned char mask,newmin,oldmin;

/** I2C FUNCTION DECLARATION **/

void stop(void);

void address(unsigned char);

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void send_byte(unsigned char);

unsigned char receive_byte(unsigned char);

void write_i2c(unsigned char,unsigned char,unsigned char);

unsigned char read_i2c(unsigned char,unsigned char);

/** TIME FUNCTIONS D

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