DESIGN OF HOME AUTOMATION USING

VOICE CONTROL

A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE

REQUIREMENTS FOR THE DEGREE OF

BY-

ABHISHEK NEB

ABSTRACT

Voice is used in this project for the controlling switches. Reason for choosing voice is

because it is easily being reproduced by human. Besides that, usage of voice gives a control

system that can be effective and convenient to be used. The application of this system involve

modifying the switching system from the traditional way which is physical contact with the

switch to a safer way where the usage of voice to replace all the physical contact. This project

involve a simple switching system that used the transistor along with relay to do all the

connecting of the power to the devices, a voice recognition system that consists of voice

recognition chip AT89C51, and the AT89C51 microcontroller to build up the system. The

ULN2003 serves as the ear that will listen and interpret the command by the given while the

AT89C51 serve as the brain of the system that will coordinate the correct output with the

input command given. This project able to recognition the command trained by the user and

successfully to execute the correct output. This project is a small scale design which consists

of 8 commands that will used to control three different switches. The command is able to

individually switch on and switch off each of the switch. Besides that, the command also able

to switch on all and off all the switch at the same time.

LIST OF ABBREVIATIONS

LED - Light Emitting Diode

LCD - Liquid Crystal Display

PCB - Printed Circuit Board

SRAM - Static Random Access Memory

RAM - Random Access Memory

ADC - Analog Digital Converter

BCD - Binary Code to Decimal

CMOS - Complementary metaloxidesemiconductor

CHAPTER 1

INTRODUCTION

1.1Background

Home automated system is characterized by the ability of the system to perform tasks to

initiate or control appliance or devices in home. Nowadays, the appliance that available in the

market is getting increase as days passed. Thus, the controlling of such devices is getting

more and more attention. From long time ago mostly the controlling is done manually such as

walking to the switch and switching it on. But as time passed the arrival or remote control that

give the user alternative way to control such appliance without the need for the user to walk to

the appliance.

From the above, there are some more advancement in the controlling method that been on

research. The advancement mention is using of the voice to act as the controlling medium to

initiate or to control the appliance. Taking example such as a security door is only can be

activated with the voice of the authorized personal only if then the door will be unlocked. In

this project, the voice is also used as the medium to perform the controlling of the electrical

appliance in home. The same concept applies in this project compare to the security door

where the different is the electrical appliance controlled.

1.2 Objective of Project

The main objective of this project is to design a voice recognition home automation system.

This project will enable the user to control the electrical appliance in home using their voice

as the medium that will control the power system. This project also aim to allow not only the

user that have train the system with their voice to control the system but it extend to the other

user who also can use the system without do the training process again.

Besides that, this system provides user a better safety against any current leakage, because by

using voice direct contact with the power source is reduced compare to the usage of

conventional switch.

1.3 Scope of Project

In order to achieve the objective of this project, there are several scope had been identified.

The scope of this project includes the designing of a voice recognition circuit for the voice

recognition purpose. Follow by the designing of the microcontroller board using AT89S52 as

the hardware that control the whole project by serving as interface for the voice recognition

board with the electrical appliance. Next, a C programming is to be design and coded to

enable the microcontroller to be able to function properly as desired.

1.4 Outlined of Thesis

This thesis consists of five chapters. In the first chapter, it discuss about the objective, scope

of project and summary of the work. In second chapter, the discussion is more focused on the

literature review. In third chapter, the discussion will be mainly on the methodology of the

hardware and the software implementation in this project

While for chapter four, the discussion is mainly on the theory and working description. Last

but not least the chapter five, the result, conclusion of this project is discussed along with the

future work

1.5 Summary of work

This project is summarized to the flow chart below for all the necessary implementation and

optimization of the project. Figure 1.1 shows the flow chart..

Figure 1.1: The Flow chart of the implementation of the project.

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

This chapter included the background study regarding the voice recognition concept and

several similar projects that applies the theory of voice and sound. It also discussed briefly

about the AT89S52 microcontroller.

2.2 Voice Recognition concept

This concept is more alike a comparison of between the source and the data stored in memory

(the voice that stored during the training process). The way of this concept function is when a

user speaks out some command, with then the voice is captured through microphone as the

input devices. Once the voice is captured, the usage of a decoding system that will convert the

analog (voice) to digital (binary signal). Later, the input voice is compared with the data

stored in the memory early before the testing. The output of the comparison is the voice

matched with any of the command trained and certain signal is produce as the input for the

controlling system.

2.3 Past Project

There are a few projects done locally by other student and researcher in Malaysia regarding

on the voice related research.

First of it will be the automated home lighting system, by a degree student of UTM. In this

projects, the usage of clap(s) as the source of input or command to control the lighting system

in home. This project offers the ability to control the lighting in term of the intensity or

brightness with corresponding to the light intensity in a room due to environment. From this

project, it can be concluded that the usage of sound is proof to be a way of controlling the

electrical appliance [1]. But the application will be limited to one electrical appliance.

Follow by another research by a master student of UTM. While for this project the voice is

apply as a way to control the wheel chair movement. In this project, a wheel chair is modified

by equipping it with the motor system that will read the command given by the user to control

it speed and movement direction [2]. This project is successful due to the usage of the

HM2007 voice recognition chip. From this project, it can be concluded that the usage of the

voice is capable to be one of the method to control electrical devices provided a suitable

system is used.

There are also some projects made by our seniors based on the controlling of electrical

appliances with the help of PC interface and remote control .

2.4 Outcome of this project

From all above of the discussion on the previous project that have been done by other student.

In this project, the application of the concept and theory used in the above project is applied.

Thus this lead to a project that have the capability to produce a system that have the

application of voice as the controlling method for controlling the electrical appliance or

devices in home.

In this system, voice is used as the primary input to the system. This is because voice is

available for each and every user by doing so the system offers a wide range of the controlling

to the user. By using all the above way the system is able to function as it was designed for

which is to enable the usage of the voice to control the electrical appliance and devices in

home.

CHAPTER 3

METHODOLOGY

3.1 Introduction

Home automation (also called domotics) is the residential extension of "building automation".

It is automation of the home, housework or household activity. Home automation may include

centralized control of lighting, HVAC (heating, ventilation and air conditioning), appliances,

and other systems, to provide improved convenience, comfort, energy efficiency and security.

Home automation for the elderly and disabled can provide increased quality of life for persons

who might otherwise require caregivers or institutional care.

A home automation system integrates electrical devices in a house with each other. The

techniques employed in home automation include those in building automation as well as the

control of domestic activities, such as home entertainment systems, houseplant and yard

watering, pet feeding, changing the ambiance "scenes" for different events (such as dinners or

parties), and the use of domestic robots. Devices may be connected through a computer

network to allow control by a personal computer, and may allow remote access from the

internet.

Typically, a new home is outfitted for home automation during construction, due to the

accessibility of the walls, outlets, and storage rooms, and the ability to make design changes

specifically to accommodate certain technologies. Wireless systems are commonly installed

when outfitting a pre-existing house, as they reduce wiring changes. These communicate

through the existing power wiring, radio, or infrared signals with a central controller. Network

sockets may be installed in every room like AC power receptacles.

Although automated homes of the future have been staple exhibits for World's Fairs and

popular backgrounds in science fiction, complexity, competition between vendors, multiple

incompatible standard and the resulting expense have limited the penetration of home

automation to homes of the wealthy or ambitious hobbyists. Possibly the first "home

computer" was an experimental system in 1966

3.1.1 History and early developments

Earliest home control systems were proposed by Hitachi & Matsushita in 1978.

First home automation blue prints and demonstrations held by Japanese Electrical

Appliance manufacturers like Sanyo, Sony, Toshiba etc.

Honeywell’s first demonstration house started in 1978.

American X 10 system appeared in 1979.

Two rival programs CE Bus and Smart House started in the early 1980’s in the US.

GE reported their multimedia home bus signaling protocol Homenet in 1983.

Total Home system launched in 1992.

GIS, Home Automation Ltd. MK Electric took the initiative in Europe.

3.1.2 General Working

Fig 2 General Working of our project

3.2 Hardware implementation

In this section will discuss on the hardware used in the implementation of this system

that include the AT89S52, ULN 2003, voltage regulator and the relay for interfaces.

Fig. Circuit of our project

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. The Power-down mode saves 3.2.1 Microcontroller AT89S52

3.2.1.1 Features

Compatible with MCS®-51 Products

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

Endurance: 10,000 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.

Low-power Idle and Power-down Modes.

Interrupt Recovery from Power-down Mode.

Watchdog Timer.

Dual Data Pointer.

Power-off Flag.

Fast Programming Time.

Flexible ISP Programming (Byte and Page Mode).

Green (Pb/Halide-free) Packaging Option.

3.2.1.2 Description

The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K bytes

of in-system programmable Flash memory. The device is manufactured using Atmel’s high-

density nonvolatile memory technology and is compatible with the industry-standard 80C51

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 in-system programmable Flash on a monolithic chip,

the Atmel AT89S52 is a powerful microcontroller which provides a highly-flexible and cost-

effective solution to many embedded control applications.

The AT89S52 provides the following standard features: 8K bytes of Flash, 256 bytes of

RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit timer/counters, a six-

vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator, and clock

circuitry. In addition, the AT89S52 is designed with static logic for operation down to the

RAM con-tents but freezes the oscillator, disabling all other chip functions until the next

interrupt or hardware reset.

3.2.1.3 Pin Configurations

40-lead PDIP 44-lead PLCC

44-leadTQFP

3.2.1.4 BLOCK DIAGRAM

3.2.1.5 Pin Description

1. VCC- Supply voltage.

2. 0.GND- Ground.

3. 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.

4. 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 inter-nal 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.

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

output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins,

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

2 pins 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 use 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 use 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.

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

output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins,

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

3 pins 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.

7. 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.

8. ALE/PROG - 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) 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 dur-ing 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. Otherwise, the pin is weakly pulled high. Setting the ALE-disable

bit has no effect if the microcontroller is in external execution mode.

9. PSEN- Program Store Enable (PSEN) is the read strobe to external program memory.

When the AT89S52 is executing code from external program memory, PSEN is

activated twice each machine cycle, except that two PSEN activations are skipped

during each access to external data memory.

10. EA/VPP- External Access Enable. EA 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 will be internally

latched on reset. EA should be strapped to VCC for internal program executions. This

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

programming.

11. XTAL1- Input to the inverting oscillator amplifier and input to the internal clock

operating circuit.

12. XTAL2 -Output from the inverting oscillator amplifier.

3.2.1.6 . Special Function Registers

A map of the on-chip memory area called the Special Function Register (SFR). Note that not

all of the addresses are occupied, and unoccupied addresses may not be implemented on the

chip. Read accesses to these addresses will in general return random data, and write accesses

will have an indeterminate effect. User software should not write 1s to these unlisted

locations, since they may be used in future products to invoke new features. In that case, the

reset or inactive values of the new bits will always be 0.

Timer 2 Registers: Control and status bits are contained in registers T2CON and T2MOD

for Timer 2. The register pair (RCAP2H, RCAP2L) are the Capture/Reload registers for

Timer 2 in 16-bit capture mode or 16-bit auto-reload mode.

Interrupt Registers: The individual interrupt enable bits are in the IE register. Two priorities

can be set for each of the six interrupt sources in the IP register.

3.2.1.7 Memory Organization

MCS-51 devices have a separate address space for Program and Data Memory. Up to 64K

bytes each of external Program and Data Memory can be addressed.

Program Memory If the EA pin is connected to GND, all program fetches are directed to

external memory. On the AT89S52, if EA is connected to VCC, program fetches to addresses

0000H through 1FFFH are directed to internal memory and fetches to addresses 2000H

through FFFFH are to external memory.

Data Memory The AT89S52 implements 256 bytes of on-chip RAM. The upper 128 bytes

occupy a parallel address space to the Special Function Registers. This means that the upper

128 bytes have the same addresses as the SFR space but are physically separate from SFR

space. When an instruction accesses an internal location above address 7FH, the address mode

used in the instruction specifies whether the CPU accesses the upper 128 bytes of RAM or the

SFR space. Instructions which use direct addressing access the SFR space.

For example, the following direct addressing instruction accesses the SFR at location 0A0H

(which is P2).

MOV 0A0H, #data

Instructions that use indirect addressing access the upper 128 bytes of RAM. For example,

the following indirect addressing instruction, where R0 contains 0A0H, accesses the data byte

at address 0A0H, rather than P2 (whose address is 0A0H).

MOV @R0, #data

Note that stack operations are examples of indirect addressing, so the upper 128 bytes of data

RAM are available as stack space.

3.2.2 78-Series Voltage Regulator

3-Terminal 1A Positive Voltage Regulator

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

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.

3.2.2 IC – ULN 2003

DESCRIPTION

The ULN2003 is high voltage, high current Darlington arrays each containing seven open

collectors 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 layout.

PACKAGE

2003A is supplied in 16 pin plastic DIP packages with a copper lead frame to reduce thermal

resistance.

ULN2003A: 06 – 15V

CMOS

PMOS

APPLICATIONS

These versatile devices are useful for driving a wide range of loads including solenoids, relays

DC motors; LED displays filament lamps, thermal print heads and high power buffers.

SCHEMATIC DIAGRAM

3.2.3POWER SUPPLY

In the power supply section we use one step down transformer to step down the voltage from

220 volt ac to 9 volt dc. Output of the transformer is further connected to the two diode

circuit. Here two diode work as a full wave rectifier circuit. Output of the full wave rectifier is

now filtered by the capacitor. Capacitor converts the pulsating dc into smooth dc with the

help of charging and discharging effect. Output of the capacitor is now regulated by the IC

7805 regulator. IC 7805 provides a 5 volt regulation to the circuit and provides a regulated 5

volt power supply. Output of the regulator is now again filter by the capacitor. In the output of

the capacitor we use one resistor and one l.e.d in series to provide a visual indication to the

circuit.

3.2.4 RECTIFIER DIODE

Philips Semiconductors Product specification

Rectifiers 1N4001G to 1N4007G

FEATURES

Glass passivated

Maximum operating temperature

Low leakage current

Excellent stability

Available in ammo-pack

DESCRIPTION

Rugged glass package, using a high temperature alloyed construction. This package is

hermetically sealed and fatigue free as coefficients of expansion of all used parts are matched.

Fig.1 Simplified outline (SOD57) and symbol.

3.2.5 TRANSISTOR

The name is transistor derived from ‘transfer resistors’ indicating a solid state Semiconductor

device. In addition to conductor and insulators, there is a third class of material that exhibits

proportion of both. Under some conditions, it acts as an insulator, and under other conditions

it’s a conductor. This phenomenon is called Semi-conducting and allows a variable control

over electron flow. So, the transistor is semi conductor device used in electronics for

amplitude. Transistor has three terminals, one is the collector, one is the base and other is the

emitter, (each lead must be connected in the circuit correctly and only then the transistor will

function). Electrons are emitted via one terminal and collected on another terminal, while the

third terminal acts as a control element. Each transistor has a number marked on its body.

Every number has its own specifications.

There are mainly two types of transistor (i) NPN & (ii) PNP

NPN Transistors:

When a positive voltage is applied to the base, the transistor begins to conduct by allowing

current to flow through the collector to emitter circuit. The relatively small current flowing

through the base circuit causes a much greater current to pass through the emitter / collector

circuit. The phenomenon is called current gain and it is measure in beta.

PNP Transistor:

It also does exactly same thing as above except that it has a negative voltage on its collector

and a positive voltage on its emitter.

Transistor is a combination of semi-conductor elements allowing a controlled current

flow. Germanium and Silicon is the two semi-conductor elements used for making it. There

are two types of transistors such as POINT CONTACT and JUNCTION TRANSISTORS.

Point contact construction is defective so is now out of use. Junction triode transistors are in

many respects analogous to triode electron tube.

A junction transistor can function as an amplifier or oscillator as can a triode tube, but has the

additional advantage of long life, small size, ruggedness and absence of cathode heating

power.

Junction transistors are of two types which can be obtained while manufacturing.

The two types are: -

1) PNP TYPE: This is formed by joining a layer of P type of germanium to an N-P

Junction.

1) NPN TYPE:

This is formed by joining a layer of N type

germanium to a P-N Junction.

Both types are shown in figure, with their

symbols for representation. The centre section is called

the base, one of the outside sections-the emitter and the other outside section-the collector.

The direction of the arrowhead gives the direction of the conventional current with the

forward bias on the emitter. The conventional flow is opposite in direction to the electron

flow.

P N P

N P N

OPERATION OF PNP TRANSISTOR

A PNP transistor is made by sand witching two PN germanium or silicon diodes, placed back

to back. The centre of N-type portion is extremely thin in comparison to P region. The P

region of the left is connected to the positive terminal and N-region to the negative terminal

i.e. PN is biased in the forward direction while P region of right is biased negatively i.e. in the

reverse direction as shown in Fig. The P region in the forward biased circuit is called the

emitter and P region on the right, biased negatively is called collector. The centre is called

base.

The majority carriers (holes) of P region (known as emitter) move to N region as they are

repelled by the positive terminal of battery while the electrons of N region are attracted by the

positive terminal. The holes overcome the barrier and cross the emitter junction into N region.

As the width of base region is extremely thin, two to five percent of holes recombine with the

free electrons of N-region which result in a small base current while the remaining holes (95%

to 98%) reach the collector junction. The collector is biased negatively and the negative

collector voltage aids in sweeping the hole into collector region.

As the P region at the right is biased negatively, a very small current should flow but

the following facts are observed:-

1) A substantial current flows through it when the emitter junction is biased in a forward

direction.

2) The current flowing across the collector is slightly less than that of the emitter.

3) The collector current is a function of emitter current i.e. with the decrease or increase

in the emitter current a corresponding change in the collector current is observed.

The facts can be explained as follows:-

1. As already discussed that 2 to 5% of the holes are lost in recombination with the

electron n base region, which result in a small base current and hence the collector

current is slightly less than the emitter current.

2. The collector current increases as the holes reaching the collector junction are

attracted by negative potential applied to the collector.

3. When the emitter current increases, most holes are injected into the base region, which

is attracted by the negative potential of the collector and hence results in increasing the

collector current. In this way emitter is analogous to the control of plate current by

small grid voltage in a vacuum triode.

Hence we can say that when the emitter is forward biased and collector is negatively

biased, a substantial current flows in both the circuits. Since a small emitter voltage of about

0.1 to 0.5 volts permits the flow of an appreciable emitter current the input power is very

small. The collector voltage can be as high as 45 volts.

3.2.6 RESISTANCE

Resistance is the opposition of a material to the current. It is measured in Ohms (). All

conductors represent a certain amount of resistance, since no conductor is 100% efficient. To

control the electron flow (current) in a predictable manner, we use resistors. Electronic

circuits use calibrated lumped resistance to control the flow of current. Broadly speaking,

resistor can be divided into two groups viz. fixed & adjustable (variable) resistors. In fixed

resistors, the value is fixed & cannot be varied. In variable resistors, the resistance value can

be varied by an adjuster knob. It can be divided into (a) Carbon composition (b) Wire wound

(c) Special type. The most common type of resistors used in our projects is carbon type. The

resistance value is normally indicated by color bands. Each resistance has four colors, one of

the band on either side will be gold or silver, this is called fourth band and indicates the

tolerance, others three band will give the value of resistance (see table). For example if a

resistor has the following marking on it say red, violet, gold. Comparing these colored rings

with the color code, its value is 27000 ohms or 27 kilo ohms and its tolerance is ±5%.

Resistor comes in various sizes (Power rating). The bigger, the size, the more power rating of

1/4 watts. The four color rings on its body tells us the value of resistor value as given below.

COLOURS CODE

Black-----------------------------------------------------0

Brown----------------------------------------------------1

Red-------------------------------------------------------2

Orange---------------------------------------------------3

Yellow---------------------------------------------------4

Green-----------------------------------------------------5

Blue-------------------------------------------------------6

Violet-----------------------------------------------------7

Grey------------------------------------------------------8

White-----------------------------------------------------9

The first rings give the first digit. The second ring gives the second digit. The third

ring indicates the number of zeroes to be placed after the digits. The fourth ring gives

tolerance (gold ±5%, silver ± 10%, No color ± 20%).

In variable resistors, we have the dial type of resistance boxes. There is a knob with a metal

pointer. This presses over brass pieces placed along a circle with some space b/w each of

them. Resistance coils of different values are connected b/w the gaps. When the knob is

rotated, the pointer also moves over the brass pieces. If a gap is skipped over, its resistance is

included in the circuit. If two gaps are skipped over, the resistances of both together are

included in the circuit and so on.

A dial type of resistance box contains many dials depending upon the range, which it has to

cover. If a resistance box has to read up to 10,000, it will have three dials each having ten

gaps i.e. ten resistance coils each of resistance 10. The third dial will have ten resistances

each of 100.

The dial type of resistance boxes is better because the contact resistance in this case is small

& constant.

3.2.7 Capacitors

It is an electronic component whose function is to accumulate charges and then release it.

To understand the concept of capacitance, consider a pair of metal plates which all are placed

near to each other without touching. If a battery is connected to these plates the positive pole

to one and the negative pole to the other, electrons from the battery will be attracted from the

plate connected to the positive terminal of the battery. If the battery is then disconnected, one

plate will be left with an excess of electrons, the other with a shortage, and a potential or

voltage difference will exists between them. These plates will be acting as capacitors.

Capacitors are of two types:-

(1) Fixed type like ceramic, polyester, electrolytic capacitors-these names refer to the

material they are made of aluminum foil.

(2) Variable type like gang condenser in radio or trimmer. In fixed type capacitors, it has two

leads and its value is written over its body and variable type has three leads. Unit of

measurement of a capacitor is farad denoted by the symbol F. It is a very big unit of

capacitance. Small unit capacitor are Pico-farad denoted by PF (1PF=1/1000, 000,000,000 f)

Above all, in case of electrolytic capacitors, its two terminal are marked as (-) and (+) so

check it while using capacitors in the circuit in right direction. Mistake can destroy the

capacitor or entire circuit in operational.

3.2.8 DIODE

The simplest semiconductor device is made up of a sandwich of P-type semiconducting

material, with contacts provided to connect the p-and n-type layers to an external circuit. This

is a junction Diode. If the positive terminal of the battery is connected to the p-type material

(cathode) and the negative terminal to the N-type material (Anode), a large current will flow.

This is called forward current or forward biased.

If the connections are reversed, a very little current will flow. This is because under this

condition, the p-type material will accept the electrons from the negative terminal of the

battery and the N-type material will give up its free electrons to the battery, resulting in the

state of electrical equilibrium since the N-type material has no more electrons. Thus there will

be a small current to flow and the diode is called Reverse biased.

Thus the Diode allows direct current to pass only in one direction while blocking it in the

other direction. Power diodes are used in concerting AC into DC. In this, current will flow

freely during the first half cycle (forward biased) and practically not at all during the other

half cycle (reverse biased). This makes the diode an effective rectifier, which convert ac into

pulsating dc. Signal diodes are used in radio circuits for detection. Zener diodes are used in

the circuit to control the voltage.

Some common diodes are:-

1. ZENER DIODE:-

A zener diode is specially designed junction diode, which can operate continuously without

being damaged in the region of reverse break down voltage. One of the most important

applications of zener diode is the design of constant voltage power supply. The zener diode is

joined in reverse bias to d.c. through a resistance R of suitable value.

2. PHOTO DIODE:-

A photo diode is a junction diode made from photo- sensitive semiconductor or material. In

such a diode, there is a provision to allow the light of suitable frequency to fall on the p-n

junction. It is reverse biased, but the voltage applied is less than the break down voltage. As

the intensity of incident light is increased, current goes on increasing till it becomes

maximum. The maximum current is called saturation current.

3. LIGHT EMITTING DIODE (LED):-

When a junction diode is forward biased, energy is released at the junction diode is forward

biased, energy is released at the junction due to recombination of electrons and holes. In case

of silicon and germanium diodes, the energy released is in infrared region. In the junction

diode made of gallium arsenate or indium phosphide, the energy is released in visible region.

Such a junction diode is called a light emitting diode or LED.

3.2.9 Relay

In this project, the primary interface between the systems with the electrical appliance is the

relay. The relay is actually a switch alike component just the different is the way of triggering

is through the magnetic field that will change the contact and thus activating a switch. This

model of relay is selected for a few reasons. First of it is the required triggering voltage which

is 5 volts and this power sources is easy to be acquire by using a simple 7805 regulator IC

Chip. Second is the contacts voltage that permitted by this model which is 240volts, and it fit

just nice to the system as this system serves as the switching system that will replace a switch

which traditionally used to connect the 240 volts power supply from 16 power supply.

3.2.10 LIGHT EMITTING DIODE

Light emitting diode (LED) is basically a P-N junction semiconductor diode particularly

designed to emit visible light. There are infrared emitting LEDs which emit invisible light.

The LEDs are now available in many colors red, green and yellow. A normal LED emits at

2.4V and consumes MA of current. The LEDs are made in the form of flat tiny P-N junction

enclosed in a semi-spherical dome made up of clear colored epoxy resin. The dome of a LED

acts as a lens and diffuser of light. The diameter of the base is less than a quarter of an inch.

The actual diameter varies somewhat with different makes. The common circuit symbols for

the LED are shown in Fig. It is similar to the conventional rectifier diode symbol with two

arrows pointing out. There are two leads- one for anode and the other for cathode.

LEDs often have leads of dissimilar length and the shorter one is the cathode. All

manufacturers do not strictly adhere this to. Sometimes the cathode side has a flat base. If

there is doubt, the polarity of the diode should be identified. A simple bench method is to use

the ohmmeter incorporating 3-volt cells for ohmmeter function. When connected with the

ohmmeter: one way there will be no deflection and when connected the other way round there

will be a large deflection of a pointer. When this occurs the anode lead is connected to the

negative of test lead and cathode to the positive test lead of the ohmmeter.

If low range (Rxl) of the ohmmeter is used the LED would light up in most cases because the

low range of ohmmeter can pass sufficient current to light up the LED.

Another safe method is to connect the test circuit shown in Fig. 2. Use any two dry cells in

series with a current limiting resistor of 68 to 100 ohms. The resistor limits the forward diode

current of the LED under test to a safe value. When the LED under test is connected to the

test terminals in any way: if it does not light up, reverse the test leads. The LED will now light

up. The anode of the LED is that which is connected to the “A” terminal (positive pole of the

battery). This method is safe, as reverse voltage can never exceed 3 volts in this test.

3.2.11 Transformers

PRINCIPLE OF THE TRANSFORMER:- Two coils are wound over a Core such

that they are magnetically coupled. The two coils are known as the primary and secondary

windings.

In a Transformer, an iron core is used. The coupling between the coils is source of making a

path for the magnetic flux to link both the coils. A core as in fig.2 is used and the coils are

wound on the limbs of the core. Because of high permeability of iron, the flux path for the

flux is only in the iron and hence the flux links both windings. Hence there is very little

‘leakage flux’. This term leakage flux denotes the part of the flux, which does not link both

the coils, i.e., when coupling is not perfect. In the high frequency transformers, ferrite core is

used. The transformers may be step-up, step-down, frequency matching, sound output,

amplifier driver etc. The basic principles of all the transformers are same.

Miniature Transformer Conventional power transformer

3.2.12 Fundamentals of RS232 Serial Communications

Due to its relative simplicity and low hardware overhead (when compared to parallel interfacing),

serial communications is used extensively within the electronics industry. Today, the most

popular serial communications standard is certainly the EIA/TIA-232-E specification. This

standard, which was developed by the Electronic Industry Association and the

Telecommunications Industry Association (EIA/TIA), is more popularly called simply RS-232,

where RS stands for "recommended standard." Although this RS prefix has been replaced in

recent years with EIA/TIA to help identify the source of the standard, this paper uses the common

RS232 notation.

3.2.12.1Introduction

The official name of the EIA/TIA-232-E standard is "Interface Between Data Terminal

Equipment and Data Circuit-Termination Equipment Employing Serial Binary Data Interchange."

Although the name may sound intimidating, the standard is simply concerned with serial data

communication between a host system (Data Terminal Equipment, or DTE) and peripheral

system. The EIA/TIA-232-E standard was introduced in 1962 and has since been updated four

times to meet the evolving needs of serial communication applications. The letter "E" in the

standard's name indicates that this is the fifth revision of the standard.

3.2.12.2RS-232 Specifications

RS-232 is a complete standard. This means that the standard sets out to ensure compatibility

between the host and peripheral systems by specifying:

1. Common voltage and signal levels

2. Common pin-wiring configurations

3. A minimal amount of control information between the host and peripheral systems.

Unlike many standards which simply specify the electrical characteristics of a given interface,

RS-232 specifies electrical, functional, and mechanical characteristics to meet the above three

criteria. Each of these aspects of the RS-232 standard is discussed below.

3.2.12.3 Electrical Characteristics

The electrical characteristics section of the RS-232 standard specifies voltage levels, rate of

change for signal levels, and line impedance. As the original RS-232 standard was defined in

1962 and before the days of TTL logic, it is no surprise that the standard does not use 5V and

ground logic levels. Instead, a high level for the driver output is defined as between +5V to

+15V, and a low level for the driver output is defined as between -5V and -15V. The receiver

logic levels were defined to provide a 2V noise margin. As such, a high level for the receiver is

defined as between +3V to +15V, and a low level is between -3V to -15V. Figure 1 illustrates the

logic levels defined by the RS-232 standard. It is necessary to note that, for RS-232

communication, a low level (-3V to -15V) is defined as a logic 1 and is historically referred to as

"marking." Similarly, a high level (+3V to +15V) is defined as logic 0 and is referred to as

"spacing."

Figure 1. RS-232 logic-level specifications.

The RS-232 standard also limits the maximum slew rate at the driver output. This limitation was

included to help reduce the likelihood of crosstalk between adjacent signals. The slower the rise

and fall time, the less chance of crosstalk. With this in mind, the maximum slew rate allowed is

30V/ms. Additionally, standard defines a maximum data rate of 20kbps, again to reduce the

chance of crosstalk. The impedance of the interface between the driver and receiver has also been

defined. The load seen by the driver is specified at 3kΩ to 7kΩ. In the original RS-232 standard

the cable length between the driver and receiver was specified to be 15 meters maximum.

Revision "D" (EIA/TIA-232-D) changed this part of the standard. Instead of specifying the

maximum length of cable, the standard specified a maximum capacitive load of 2500pF, clearly a

more adequate specification. The maximum cable length is determined by the capacitance per

unit length of the cable, which is provided in the cable specifications.

Table 1 summarizes the electrical specifications in the current standard.

Table 1. RS-232 Specifications

RS-232

Cabling Single-ended

Number of Devices 1 transmit, 1 receive

Communication

ModeFull duplex

Distance (max) 50 feet at 19.2kbps

Data Rate (max) 1Mbps

Signaling Unbalanced

Mark (data 1) -5V (min) -15V (max)

Space (data 0) 5V (min) 15V (max)

Input Level (min) ±3V

Output Current500mA (Note that the driver ICs normally used in PCs are limited to

10mA)

Impedance 5kΩ (Internal)

Bus Architecture Point-to-Point

3.2.12.4Functional Characteristics

Because RS-232 is a complete standard, it includes more than just specifications on electrical

characteristics. The standard also addresses the functional characteristics of the interface, #2 on

our list above. This essentially means that RS-232 defines the function of the different signals

used in the interface. These signals are divided into four different categories: common, data,

control, and timing. See Table 2. The standard provides abundant control signals and supports a

primary and secondary communications channel. Fortunately few applications, if any, require all

these defined signals. For example, only eight signals are used for a typical modem. Examples of

how the RS-232 standard is used in real-world applications are discussed later. The complete list

of defined signals is included here as a reference. Reviewing the functionality of all these signals

is, however, beyond the scope of this paper.

Table 2. RS-232 Defined Signals

Circuit

MnemonicCircuit Name*

Circuit

Direction

Circuit

Type

AB Signal Common — Common

BA

BB

Transmitted Data (TD)

Received Data (RD)

To DCE

From DCEData

CA

CB

CC

CD

CE

CF

CG

CH

CI

CJ

RL

LL

TM

Request to Send (RTS)

Clear to Send (CTS)

DCE Ready (DSR)

DTE Ready (DTR)

Ring Indicator (RI)

Received Line Signal Detector** (DCD)

Signal Quality Detector

Data Signal Rate Detector from DTE

Data Signal Rate Detector from DCE

Ready for Receiving

Remote Loopback

Local Loopback

Test Mode

To DCE

From DCE

From DCE

To DCE

From DCE

From DCE

From DCE

To DCE

From DCE

To DCE

To DCE

To DCE

From DCE

Control

DAransmitter Signal Element Timing from

DTETo DCE  

DB

DD

Transmitter Signal Element Timing from

DCE

Receiver Signal Element Timing from DCE

From DCE

From DCETiming

SBA

SBB

Secondary Transmitted Data

Secondary Received Data

To DCE

From DCEData

SCA

SCB

SCF

Secondary Request to Send

Secondary Clear to Send

Secondary Received Line Signal Detector

To DCE

From DCE

From DCE

Control

*Signals with abbreviations in parentheses are the eight most commonly used signals.

**This signal is more commonly referred to as Data Carrier Detect (DCD).

3.2.12.5 Mechanical Interface Characteristics

The third area covered by RS-232 is the mechanical interface. Specifically, RS-232 specifies a

25-pin connector as the minimum connector size that can accommodate all the signals defined in

the functional portion of the standard. The pin assignment for this connector is shown in Figure 2.

The connector for DCE equipment is male for the connector housing and female for the

connection pins. Likewise, the DTE connector is a female housing with male connection pins.

Although RS-232 specifies a 25-position connector, this connector is often not used. Most

applications do not require all the defined signals, so a 25-pin connector is larger than necessary.

Consequently, other connector types are commonly used. Perhaps the most popular connector is

the 9-position DB9S connector, also illustrated in Figure 2. This 9-position connector provides,

for example, the means to transmit and receive the necessary signals for modem applications.

This type pf application will be discussed in greater detail later.

Figure 2. RS-232 connector pin assignments.

3.2.12.6 Evolution of RS-232 IC Design

Regulated Charge Pumps

The original MAX232 Driver/Receiver and its related parts simply doubled and inverted the input

voltage to supply the RS-232 driver circuitry. This design enabled much more voltage than

actually required; it wasted power. The EIA-232 levels are defined as ±5V into 5kΩ. With a new

low-dropout output stage, Maxim introduced RS-232 transceivers with internal charge pumps

that provided regulated ±5.5V outputs. This design allows the transmitter outputs to maintain RS-

232-compatible levels with a minimum amount of supply current.

Low-Voltage Operation

The reduced output voltages of the new regulated charge pumps and low-dropout transmitters

allow use of reduced supply voltages. Most of Maxim's recent RS-232 transceivers operate with

supply voltages down to +3.0V.

Auto Shutdown

In the never-ending battle to extend battery life, Maxim pioneered a technique called auto-

shutdown. When the device is not detecting valid RS-232 activity, it enters a low-power

shutdown mode. An RS-232-valid output indicates to the system processor whether an active RS-

232 port is connected at the other end of the cable. The MAX3212 goes one step further: it

includes a transition-detect circuit whose latched output, applied as an interrupt, can awaken the

system when a change of state occurs on any incoming line.

Auto Shutdown Plus

Building on the success of Auto Shutdown, devices with Maxim's Auto Shutdown Plus capability

achieve a 1µA supply current. These devices automatically enter a low-power shutdown mode

either when the RS-232 cable is disconnected or the transmitters of the connected peripherals are

inactive, or when the UART driving the transmitter inputs is inactive for more than 30 seconds.

The devices turn on again when they sense a valid transition at any transmitter or receiver input.

Auto Shutdown Plus saves power without changes to the existing BIOS or operating system.

Mega Baud

Moving beyond the EIA-232 specification is mega baud mode, which allows the driver slew rate

to increase, thereby providing data rates up to 1Mbps. Mega Baud mode is useful for

communication between high-speed peripherals such DSL or ISDN modems over short distances.

High ESD

Some ICs are designed to provide high ESD protection. These ICs specify and achieve ±15kV

ESD protection using both the human body model and the IEC 801-2 air-gap discharge method.

Maxim's high-ESD protection eliminates the need for costly external protection devices such as

Transzorbs, while preventing expensive field failures.

Capacitor Selection

The charge pumps of Maxim RS-232 transceivers rely on capacitors to convert and store energy,

so choosing these capacitors affects the circuit's overall performance. Although some data sheets

indicate polarized capacitors in their typical application circuits, this information is shown only

for a customer who wants to use polarized capacitors. In practice, ceramic capacitors work best

for most Maxim RS-232 ICs. Choosing the ceramic capacitor is also important. Capacitor

dielectric types of Z5U and Y5V are unacceptable because of their incredible voltage and

temperature coefficients. Types X5R and X7R provide the necessary performance.

Unused Inputs

RS-232 receiver inputs contain an internal 5kΩ pull-down resistor. If this receiver input is

unused, it can be left floating without causing any problems. The CMOS transmitter inputs are

high-impedance and must be driven to valid logic levels for proper IC operation. If a transmitter

input is unused, connect it to VCC or GND.

Layout Guidelines

Maxim RS-232 ICs should be treated like DC-DC converters for layout purposes. The AC current

flow must be analyzed for both the charge and discharge stages of the charge-pump cycle. To

facilitate an easy and effective layout, Maxim conveniently places all the critical pins in close

proximity to their external components.

RS-232 Transceivers in Tiny Packages

Low-power RS-232 transceivers are available in space-saving chip-scale (UCSP), TQFN, and

TSSOP packages. The MAX3243E in a 32-pin (7mm x 7mm) thin QFN package saves 20%

board space over TSSOP solutions. The MAX3222E, also available in a 20-pin (5mm x 5mm)

TQFN, improves and thus saves board space by 40%. Other transceiver part families packaged in

a TQFN, the MAX3222E and MAX3232E with two drivers and two receivers and the

MAX3221E with a single driver and single receiver, feature Auto Shutdown capability to reduce

the supply current to 1µA (See Table 3). These RS-232 transceivers are ideal for battery-

powered equipment.

The MAX3228E/MAX3229E family in a 30-bump (3mm x 2.5mm) UCSP package saves about

70% board space, making these ICs ideal for space-constrained applications such as notebook,

cell phone, and handheld equipment. Low-power RS-232 transceivers in space-saving UCSP with

a low 1µA shutdown supply current are ideal for ultra-low-power system applications.

Table 3. RS232 Transceivers in Space-Saving Packages

Part PackageShutdown Supply

Current (µA)

Data Rate

(kbps)

No. of

Drivers/Receivers

ESD

Protection

(±kV)

MAX3221E20-Pin

TQFN1 250 1/1 15

MAX3222E 16-Pin 1 250 2/2 15

TQFN

MAX3223E20-Pin

TQFN1 250 2/2 15

MAX3230E20-Bump

UCSP1 250 2/2 15

MAX3231E20-Bump

UCSP1 250 1/1 15

MAX3232E16-Pin

TQFN1 250 2/2 15

MAX3237E28-Pin

SSOP10nA 1Mbps 5/3 15

MAX3243E32-Pin

TQFN1 250 3/5 15

MAX3246E36-Bump

UCSP1 250 3/5  

Practical RS-232 Implementation

Most systems designed today do not operate using RS-232 voltage levels. Consequently, level

conversion is necessary to implement RS-232 communication. Level conversion is performed by

special RS-232 ICs with both line drivers that generate the voltage levels required by RS-232,

and line receivers that can receive RS-232 voltage levels without being damaged. These line

drivers and receivers typically invert the signal as well, since logic 1 is represented by a low

voltage level for RS-232 communication, and logic 0 is represented by a high logic level.

Figure 3 illustrates the function of an RS-232 line driver/receiver in a typical modem application.

In this example, the signals necessary for serial communication are generated and received by the

Universal Asynchronous Receiver/Transmitter (UART). The RS-232 line driver/receiver IC

performs the level translation necessary between the CMOS/TTL and RS-232 interface.

Figure 3. Typical RS-232 modem application.

The UART performs the "overhead" tasks necessary for asynchronous serial communication.

Asynchronous communication usually requires, for example, that the host system initiate start

and stop bits to indicate to the peripheral system when communication will start and stop. Parity

bits are also often employed to ensure that the data sent has not been corrupted. The UART

usually generates the start, stop, and parity bits when transmitting data, and can detect

communication errors upon receiving data. The UART also functions as the intermediary

between byte-wide (parallel) and bit-wide (serial) communication; it converts a byte of data into

a serial bit stream for transmitting and converts a serial bit stream into a byte of data when

receiving.

Now that an elementary explanation of the TTL/CMOS to RS-232 interface has been provided,

we can consider some real-world RS-232 applications. It has already been noted in the Functional

Characteristics section above that RS-232 applications rarely follow the RS-232 standard

precisely. The unnecessary RS-232 signals are usually omitted. Many applications, such as a

modem, require only nine signals (two data signals, six control signals, and ground). Other

applications require only five signals (two for data, two for handshaking, and ground), while

others require only data signals with no handshake control. We begin our investigation of real-

world implementations by considering the typical modem application.

3.2.12.7 RS-232 in Modem Applications

Modem applications are one of the most popular uses for the RS-232 standard. Figure 4

illustrates a typical modem application. As can be seen in the diagram, the PC is the DTE and the

modem is the DCE. Communication between each PC and its associated modem is accomplished

using the RS-232 standard. Communication between the two modems is accomplished through

telecommunication. It should be noted that, although a microcontroller is usually the DTE in RS-

232 applications, this is not mandated by a strict interpretation of the standard.

Figure 4. Modem communication between two PCs.

Although some designers choose to use a 25-pin connector for this application, it is not necessary

as there are only nine interface signals (including ground) between the DTE and DCE. With this

in mind, many designers use 9- or 15-pin connectors. (Figure 2 above shows a 9-pin connector

design.) The "basic nine" signals used in modem communication are illustrated in Figure 3

above; three RS-232 drivers and five receivers are necessary for the DTE. The functionality of

these signals is described below. Note that for the following signal descriptions, ON refers to a

high RS-232 voltage level (+5V to +15V), and OFF refers to a low RS-232 voltage level (-5V to

-15V). Keep in mind that a high RS-232 voltage level actually represents a logic 0, and that a low

RS-232 voltage level refers to a logic 1.

Transmitted Data (TD):

One of two separate data signals, this signal is generated by the DTE and received by the DCE.

Received Data (RD):

The second of two separate data signals, this signals is generated by the DCE and received by the

DTE.

Request to Send (RTS):

When the host system (DTE) is ready to transmit data to the peripheral system (DCE), RTS is

turned ON. In simplex and duplex systems, this condition maintains the DCE in receive mode. In

half-duplex systems, this condition maintains the DCE in receive mode and disables transmit

mode. The OFF condition maintains the DCE in transmit mode. After RTS is asserted, the DCE

must assert CTS before communication can commence.

Clear to Send (CTS):

CTS is used along with RTS to provide handshaking between the DTE and the DCE. After the

DCE sees an asserted RTS, it turns CTS ON when it is ready to begin communication.

Data Set Ready (DSR):

This signal is turned on by the DCE to indicate that it is connected to the telecommunications

line.

Data Carrier Detect (DCD):

This signal is turned ON when the DCE is receiving a signal from a remote DCE, which meets its

suitable signal criteria. This signal remains ON as long as a suitable carrier signal can be

detected.

Data Terminal Ready (DTR):

DTR indicates the readiness of the DTE. This signal is turned ON by the DTE when it is ready to

transmit or receive data from the DCE. DTR must be ON before the DCE can assert DSR.

Ring Indicator (RI):

RI, when asserted, indicates that a ringing signal is being received on the communications

channel.

The signals described above form the basis for modem communication. Perhaps the best way to

understand how these signals interact is to examine a step-by-step example of a modem

interfacing with a PC. The following steps describe a transaction in which a remote modem calls

a local modem.

1. The local Pc uses software to monitor the RI (Ring Indicate) signal.

2. When the remote modem wants to communicate with the local modem, it generates an RI

signal. This signal is transferred by the local modem to the local PC.

3. The local PC responds to the RI signal by asserting the DTR (Data Terminal Ready)

signal when it is ready to communicate.

4. After recognizing the asserted DTR signal, the modem responds by asserting DSR (Data

Set Ready) after it is connected to the communications line. DSR indicates to the PC that

the modem is ready to exchange further control signals with the DTE to commence

communication. When DSR is asserted, the PC begins monitoring DCD for an indication

that data is being sent over the communication line.

5. The modem asserts DCD (Data Carrier Detect) after it has received a carrier signal from

the remote modem that meets the suitable signal criteria.

6. At this point data transfer can begin. If the local modem has full-duplex capability, the

CTS (Clear to Send) and RTS (Request to Send) signals are held in the asserted state. If

the modem has only half-duplex capability, CTS and RTS provide the handshaking

necessary for controlling the direction of the data flow. Data is transferred over the RD

and TD signals.

7. When the transfer of data has been completed, the PC disables the DTR signal. The

modem follows by inhibiting the DSR and DCD signals. At this point the PC and modem

are in the original state described in step number 1.

3.2.12.8 RS-232 in Minimal Handshake Applications

Although the modem application discussed above is simplified from the RS-232 standard because

of the number of signals needed, it is still more complex than many system requirements. For

many applications, only two data lines and two handshake control lines are necessary to establish

and control communication between a host system and a peripheral system. For e.g., an

environmental control system may need to interface with a thermostat using a half-duplex

communication scheme. At times the control systems read the temperature from the thermostat

and at other times they load temperature trip points to the thermostat. In this type of simple

application, only five signals could be needed (two for data, two for handshake control, and

ground.

Figure 5 illustrates a simple half-duplex communication interface. As can be seen, data is

transferred over the TD (Transmit Data) and RD (Receive Data) pins, and the RTS (Ready to

Send) and CTS (Clear to Send) pins provide handshake control. RTS is driven by the DTE to

control the direction of data. When it is asserted, the DTE is placed in transmit mode. When RTS

is inhibited, the DTE is placed in receive mode. CTS, which is generated by the DCE, controls

the flow of data. When asserted, data can flow. However, when CTS is inhibited, the transfer of

data is interrupted. The transmission of data is halted until CTS is reasserted.

Figure 5. Half-duplex communication scheme.

3.2.12.9 RS-232 Application Limitations

In the more than four decades since the RS-232 standard was introduced, the electronics industry

has changed immensely. There are, therefore, some limitations in the RS-232 standard. One

limitation—the fact that over twenty signals have been defined by the standard—has already been

addressed. Designers simply do not use all the signals or the 25-pin connector.

Other limitations in the standard are not necessarily as easy to correct.

Generation of RS-232 Voltage Levels

As explained in the Electrical Characteristics section, RS-232 does not use the conventional 0

and 5V levels implemented in TTL and CMOS designs. Drivers have to supply +5V to +15V for

logic 0 and -5V to -15V for logic 1. This means that extra power supplies are needed to drive the

RS-232 voltage levels. Typically, a +12V and a -12V power supply are used to drive the RS-232

outputs. This is a great inconvenience for systems that have no other requirements for these

power supplies. With this in mind, RS-232 products manufactured by Dallas Semiconductor have

on-chip charge-pump circuits that generate the necessary voltage levels for RS-232

communication. The first charge pump essentially doubles the standard +5V power supply to

provide the voltage level necessary for driving logic 0. A second charge pump inverts this voltage

and provides the voltage level necessary for driving logic 1. These two charge pumps allow the

RS-232 interface products to operate from a single +5V supply.

Maximum Data Rate

Another limitation in the RS-232 standard is the maximum data rate. The standard defines a

maximum data rate of 20kbps, which is unnecessarily slow for many of today's applications. RS-

232 products manufactured by Dallas Semiconductor guarantee up to 250kbps and typically can

communicate up to 350kbps. While providing a communication rate at this frequency, the devices

still maintain a maximum 30V/ms maximum slew rate to reduce the likelihood of crosstalk

between adjacent signals.

Maximum Cable Length

As we have seen, the cable-length specification once included in the RS-232 standard has been

replaced by a maximum load-capacitance specification of 2500pF. To determine the total length

of cable allowed, one must determine the total line capacitance.

Figure 6 shows a simple approximation for the total line capacitance of a conductor. As can be

seen, the total capacitance is approximated by the sum of the mutual capacitance between the

signal conductors and the conductor to shield capacitance (or stray capacitance in the case of

unshielded cable).

As an example, assume that the user decided to use no shielded cable when interconnecting the

equipment. The mutual capacitance (Cm) of the cable is found in the cable's specifications to be

20pF per foot. Assuming that the receiver's input capacitance is 20pF, this leaves the user with

2480pF for the interconnecting cable. From the equation in Figure 6, the total capacitance per

foot is 30pF. Dividing 2480pF by 30pF reveals that the maximum cable length is approximately

80 feet. If a longer cable length is required, the user must find a cable with a smaller mutual

capacitance.

Figure 6. Interface cable-capacitive model, per unit length.

Auto Shutdown is a trademark of Maxim Integrated Products, Inc.

3.3 Software implementation

3.3.1 INTRODUCTION TO KEIL SOFTWARE

Keil Micro Vision is an integrated development environment used to create software to be run

on embedded systems (like a microcontroller). It allows for such software to be written either

in assembly or C programming languages and for that software to be simulated on a computer

before being loaded onto the microcontroller.

3.3.1.1 WHAT IS μVision3?

μVision3 is an IDE (Integrated Development Environment) that helps write, compile, and

debug embedded programs. It encapsulates the following components:

A project manager.

A make facility.

A Tool configuration.

An Editor.

A powerful debugger.

3.3.1.2STEPS FOLLOWED IN CREATING AN APPLICATION IN uVision3:

To create a new project in uVision3:

1. Select Project - New Project

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

3. Select Project –Select Device and select a device from Device Database.

4. Create source files to add to the project

5. Select Project - Targets, Groups, and Files. Add/Files, select Source Group1, add the

source files to the project.

6. Select Project - Options and set the tool options. Note that when the target device is

selected from the Device Database all-special options are set automatically. Default

memory model settings are optimal for most applications.

7. Select Project - Rebuild all target files or Build target

To create a new project, simply start Micro Vision and select

“Project”=>”New Project” from the pull–down menus. In the file dialog that appears, choose

a name and base directory for the project. It is recommended that a new directory be created

for each project, as several files will be generated. Once the project has been named, the

dialog shown in the figure below will appear, prompting the user to select a target device. In

this lab, the chip being used is the “AT89S52,” which is listed under the heading “Atmel”

.

Fig-Window for choosing the target device

Next, Micro Vision must be instructed to generate a HEX file upon program compilation. A

HEX file is a standard file format for storing executable code that is to be loaded onto the

microcontroller.

In the “Project Workspace” pane at the left, right–click on “Target 1” and select “Options for

‘Target 1’ ”.Under the “Output” tab of the resulting options dialog, ensure that both the

“Create Executable” and “Create HEX File” options are checked. Then click “OK”

As shown in the two figures below.

Fig- Project workspace pane Fig-Project Options Dialog

Next, a file must be added to the project that will contain the project code. To do this, expand

the “Target 1” heading, right–click on the “Source Group 1” folder, and select “Add files…”

Create a new blank file (the file name should end in “.asm”), select it, and click “Add.” The

new file should now appear in the “Project Workspace” pane under the “Source Group 1”

folder. Double-click on the newly created file to open it in the editor. All code for this lab will

go in this file. To compile the program, first save all source files by clicking on the “Save All”

button, and then click on the “Rebuild All Target Files” to compile the program as shown in

the figure below. If any errors or warnings occur during compilation, they will be displayed in

the output window at the bottom of the screen. All errors and warnings will reference the line

and column number in which they occur along with a description of the problem so that they

can be easily located. Note that only errors indicate that the compilation failed, warnings do

not (though it is generally a good idea to look into them anyway).

Fig. “Save All” and “Build All Target Files” Buttons

When the program has been successfully compiled, it can be simulated using the integrated

debugger in Keil Micro Vision. To start the debugger, select “Debug”=>”Start/Stop Debug

Session” from the pull–down menus.

At the left side of the debugger window, a table is displayed containing several key

parameters about the simulated microcontroller, most notably the elapsed time (circled in the

figure below). Just above that, there are several buttons that control code execution. The

“Run” button will cause the program to run continuously until a breakpoint is reached,

whereas the “Step Into” button will execute the next line of code and then pause (the current

position in the program is indicated by a yellow arrow to the left of the code).

Fig. μVision3 Debugger window

Breakpoints can be set by double–clicking on the grey bar on the left edge of the window

containing the program code. A breakpoint is indicated by a red box next to the line of code.

Fig ‘Reset’, ‘Run’ and ‘Step into’ options

The current state of the pins on each I/O port on the simulated microcontroller can also be

displayed. To view the state of a port, select “Peripherals”=>”I/O Ports”=>”Port n” from the

pull–down menus, where n is the port number. A checked box in the port window indicates a

high (1) pin, and an empty box indicates a low (0) pin. Both the I/O port data and the data at

the left side of the screen are updated whenever the program is paused.

The debugger will help eliminate many programming errors, however the simulation is not

perfect and code that executes properly in simulation may not always work on the actual

microcontroller.

3.3.1.3DEVICE DATABASE

A unique feature of the Keil μVision3 IDE is the Device Database, which contains

information about more than 400 supported microcontrollers. When you create a new

μVision3 project and select the target chip from the database, μVision3 sets all assembler,

compiler, linker, and debugger options for you. The only option you must configure is the

memory map.

3.3.1.4PERIPHERAL SIMULATION

The μVision3 Debugger provides complete simulation for the CPU and on-chip peripherals of

most embedded devices. To discover which peripherals of a device are supported, in μVision3

select the Simulated Peripherals item from the Help menu. You may also use the web-based

Device Database. We are constantly adding new devices and simulation support for on-chip

peripherals so be sure to check Device Database often.

3.3.2PROGRAMMER

The programmer used is a powerful programmer for the Atmel 89 series of microcontrollers

that includes 89C51/52/55, 89S51/52/55 and many more.

It is simple to use & low cost, yet powerful flash microcontroller programmer for the Atmel

89 series. It will Program, Read and Verify Code Data, Write Lock Bits, Erase and Blank

Check. All fuse and lock bits are programmable. This programmer has intelligent onboard

firmware and connects to the serial port. It can be used with any type of computer and

requires no special hardware. All that is needed is a serial communication port which all

computers have.

All devices also have a number of lock bits to provide various levels of software and

programming protection. These lock bits are fully programmable using this programmer.

Locks bits are useful to protect the program to be read back from microcontroller only

allowing erase to reprogram the microcontroller.

Major parts of this programmer are Serial Port, Power Supply and Firmware microcontroller.

Serial data is sent and received from 9 pin connector and converted to/from TTL logic/RS232

signal levels by MAX232 chip. A Male to Female serial port cable, connects to the 9 pin

connector of hardware and another side connects to back of computer.

All the programming ‘intelligence’ is built into the programmer so you do not need any

special hardware to run it. Programmer comes with window based software for easy

programming of the devices.

3.3.3 VOICE RECOGNITION SOFTWARE

The way of this concept function is when a user speaks out some command, then the voice is

captured through microphone as the input devices.

Once the voice is captured, the usage of a decoding system that will convert the analog

(voice) to digital (binary signal).

Later, the input voice is compared with the data stored in the memory early before the testing.

The output of the comparison is the voice matched with any of the command trained and

certain signal is produce as the input for the controlling system.

In this project whenever we want to control the machine from our voice then first of we

enable the button of voice control. As we speaks through the mike on/off then the control

panel works as per condition.

Whenever we want to control the machine computer then first of we enable the button of pc

control. As we enable the button then with the help mouse we on /off the control panel as per

our requirement. Once we enable the button then Red indicator is lit on the screen then

computer send a code to the microcontroller via RS 232 com port. Data is transfer via serial

port on the baud rate of 9600 bps. Data transfer in the 8 bit package. Data receive by the

controller receive pin via Max 232 IC. IC max232 is RS232 to TTL converter IC. As the code

is receive by the controller inside and then switch on/off the electrical appliances in. When the

output is on then connected L.E.D. is on and when the output is off then connected L.E.D is

off.

For this project we transfer the data from computer in the form of serial communication.

When we want to control the appliances through Wireless remote then first of all we enable

the remote option. In the project we use RC5 TV remote. There is lot of remote are available,

but in this project we use RC5 base remote fro switching. For Any remote control device we

must know the protocol of infra red transmission. In the infra red transmission we send the

different codes on modulated frequency. Each time when we press any switch from the

remote then one modulated signal is transfer to the receiver circuit. On the receiver end we

receive this code with the help of infra red receiver eye. Receiver eye receive the code then

demodulated the frequency. Code from the eye is further connected to then microcontroller

for further process. Microcontroller receives the code and after processing Toggle the

electrical switch regular rally.

In our project we use MICROSOFT VISUAL BASIC to run appliance controller.

Chapter 4

Working Description

4.1 MAKING PRINTED CIRCUIT BOARD (P.C.B.)

4.1.1 INTRODUCTION—

Making a Printed Circuit Board is the first step towards building electronic equipment by any

electronic industry. A number of methods are available for making P.C.B., the simplest

method is of drawing pattern on a copper clad board with acid resistant (etchants) ink or paint

or simple nail polish on a copper clad board and do the etching process for dissolving the rest

of copper pattern in acid liquid.

4.1.2 MATERIAL REQUIRED

The apparatus needs for making a P.C.B. is:-

Copper Clad Sheet

Nail Polish or Paint

Ferric Chloride Powder. (Fecl)

Plastic Tray

Tap Water etc.

4.1.3 PROCEDURE

The first and foremost in the process is to clean all dirt from copper sheet with say spirit or

trichloro ethylene to remove traces grease or oil etc. and then wash the board under running

tap water. Dry the surface with forced warm air or just leave the board to dry naturally for

some time.

Making of the P.C.B. drawing involves some preliminary consideration such as thickness of

lines/ holes according to the components. Now draw the sketch of P.C.B. design (tracks, rows,

square) as per circuit diagram with the help of nail polish or enamel paint or any other acid

resistant liquid. Dry the point surface in open air, when it is completely dried, the marked

holes in P.C.B. may be drilled using 1Mm drill bits. In case there is any shorting of lines due

to spilling of paint, these may be removed by scraping with a blade or a knife, after the paint

has dried.

After drying, 22-30 grams of ferric chloride in 75 ml of water may be heated to about 60

degree and poured over the P.C.B. , placed with its copper side upwards in a plastic tray of

about 15*20 cm. Stirring the solution helps speedy etching. The dissolution of unwanted

copper would take about 45 minutes. If etching takes longer, the solution may be heated again

and the process repeated. The paint on the pattern can be removed P.C.B. may then be washed

and dried. Put a coat of varnish to retain the shine. Your P.C.B. is ready.

4.1.4 REACTION

Fecl3 + Cu ----- CuCl3 + Fe

Fecl3 + 3H2O --------- Fe (OH)3 + 3HCL

4.1.5 PRECAUTION

1. Add Ferric Chloride (Fecl3) carefully, without any splashing. Fecl3 is irritating to the

skin and will stain the clothes.

2. Place the board in solution with copper side up.

3. Try not to breathe the vapors. Stir the solution by giving see-saw motion to the dish

and solution in it.

4. Occasionally warm if the solution over a heater-not to boiling. After some time the

unshaded parts change their color continue to etch. Gradually the base material will

become visible. Etch for two minutes more to get a neat pattern.

5. Don't throw away the remaining Fecl3 solution. It can be used again for next Printed

Circuit Board P.C.B.

4.1.6 USES

Printed Circuit Board are used for housing components to make a circuit for compactness,

simplicity of servicing and case of interconnection. Thus we can define the P.C.B. as :

Prinked Circuit Boards is actually a sheet of bakelite (an insulating material) on the one side

of which copper patterns are made with holes and from another side, leads of electronic

components are inserted in the proper holes and soldered to the copper points on the back.

Thus leads of electronic components terminals are joined to make electronic circuit. In the

boards copper cladding is done by pasting thin copper foil on the boards during curing. The

copper on the board is about 2 mm thick and weights an ounce per square foot.

The process of making a Printed Circuit for any application has the following steps (opted

professionally):

Preparing the layout of the track.

Transferring this layout photographically M the copper.

Removing the copper in places which are not needed, by the process of etching

(chemical process)

Drilling holes for components mounting.

4.1.7 PRINTED CIRCUIT BOARD

Printed circuit boards are used for housing components to make a circuit, for compactness,

simplicity of servicing and ease of interconnection. Single sided, double sided and double

sided with plated-through-hold (PYH) types of p.c boards are common today.

Boards are of two types of material (1) phenolic paper based material (2) Glass epoxy

material. Both materials are available as laminate sheets with copper cladding.

Printed circuit boards have a copper cladding on one or both sides. In both boards, pasting

thin copper foil on the board during curing does this. Boards are prepared in sizes of 1 to 5

metre wide and up to 2 meters long. The thickness of the boards is 1.42 to 1.8mm. The copper

on the boards is about 0.2 thick and weighs and ounce per square foot.

4.2 Soldering Process

Building project in the proper manner is really an art, something which must be précised and

learned through trial and error, it is not all that difficult. The main thing is to remember to

take each step slowly and carefully according to the instructions giving making since that

everything at it should be before proceeding further.

4.2.1 TOOLS: The electronics workbench is an actual place of work with comfortably &

conveniently & should be supplied with compliment of those tools must often use in project

building. Probably the most important device is a soldering tool. Other tool which should be

at the electronic work bench includes a pair of needle nose pliers, diagonal wire cutter, a small

knife, an assortment of screw driver, nut driver, few nuts & bolts, electrical tape, pucker etc.

Diagonal wire cutter will be used to cut away any excess lead length from copper side of

P.C.B. 7 to cut section of the board after the circuit is complete. The needle nose pliers are

most often using to bend wire leads & wrap them in order to form a strong mechanical

connection.

4.2.2 MOUNTING & SOLDERING: Soldering is

process of joining together two metallic parts. It is

actually a process of function in which an alloy, the

solder, with a comparatively low melting point

penetrates the surface of the metal being joined & makes a firm joint between them on

cooling & solidifying.

4.2.3 THE SOLDERING KIT

1. SOLDERING IRON: As soldering is a process of joining together two

metallic parts, the instrument, which is used, for doing this job is known as soldering

Iron. Thus it is meant for melting the solder and to setup the metal parts being joined.

Soldering Iron is rated according to their wattage, which varies from 10- 200 watts.

2. SOLDER: The raw material used for soldering is solder. It is composition of lead &

tin. The good quality solder (a type of flexible naked wire) is 60% Tin +40% Lead

which will melt between 180 degree to 200 degree C temperature.

3. LUXES OR SOLDERING PASTE: When the points to solder are heated, an oxide

film forms. This must be removed at once so that solder may get to the surface of the

metal parts. This is done by applying chemical substance called Flux, which boils

under the heat of the iron remove the oxide formation and enable the metal to receive

the solder.

4. BLADES OR KNIFE: To clean the surface & leads of components to be soldered is

done by this common instrument.

5. SAND PAPER: The oxide formation may attack at the tip of your soldering iron &

create the problem. To prevent this, clean the tip with the help of sand paper time to

time or you may use blade for doing this job. Apart from all these tools, the working

bench for soldering also includes desoldering pump, wink wire (used for desoldering

purpose), file etc.

4.2.4 HOW TO SOLDER?

Mount components at their appropriate place; bend the leads slightly outwards to prevent

them from falling out when the board is turned over for soldering. No cut the leads so that

you may solder them easily. Apply a small amount of flux at these components leads with

the help of a screwdriver. Now fix the bit or iron with a small amount of solder and flow

freely at the point and the P.C.B copper track at the same time. A good solder joint will

appear smooth & shiny. If all appear well, you may continue to the next solder

connections.

4.2.5 TIPS FOR GOOD SOLDERING

1. Use right type of soldering iron. A small efficient soldering iron (about 10-25 watts with

1/8 or 1/4 inch tip) is ideal for this work.

2. Keep the hot tip of the soldering iron on a piece of metal so that excess heat is dissipated.

3. Make sure that connection to the soldered is clean. Wax frayed insulation and other

substances cause poor soldering connection. Clean the leads, wires, tags etc. before

soldering.

4. Use just enough solder to cover the lead to be soldered. Excess solder can cause a short

circuit.

5. Use sufficient heat. This is the essence of good soldering. Apply enough heat to the

component lead. You are not using enough heat, if the solder barely melts and forms a

round ball of rough flaky solder. A good solder joint will look smooth, shining and spread

type. The difference between good & bad soldering is just a few seconds extra with a hot

iron applied firmly.

4.2.6 PRECAUTIONS

1. Mount the components at the appropriate places before soldering. Follow the circuit

description and components details, leads identification etc. Do not start soldering before

making it confirm that all the components are mounted at the right place.

2. Do not use a spread solder on the board, it may cause short circuit.

3. Do not sit under the fan while soldering.

4. Position the board so that gravity tends to keep the solder where you want it.

5. Do not over heat the components at the board. Excess heat may damage the components

or board.

6. The board should not vibrate while soldering otherwise you have a dry or a cold joint.

7. Do not put the kit under or over voltage source. Be sure about the voltage either dc or ac

while operating the gadget.

8. Do spare the bare ends of the components leads otherwise it may short circuit with the

other components. To prevent this use sleeves at the component leads or use sleeved

wire for connections.

9. Do not use old dark color solder. It may give dry joint. Be sure that all the joints are

clean and well shiny.

10. Do make loose wire connections especially with cell holder, speaker, probes etc. Put

knots while connections to the circuit board, otherwise it may get loose.

CHAPTER 5

RESULT AND DISCUSSION

5.1 RESULT AND DISCUSSION

Since this system is related to the voice or the speech by the user that will use to control this

system, thus there is some issue that arises when using this system. The problems are the

pronunciation of the user when doing the training process, pronunciation when using the

system, the repetition of the same word used to train the system with different number and

lastly the length of the word used. For the pronunciation matter, the system takes it at a quite

high level of sensitivity. The main reason is when a word is trained into the system, the

HM2007 IC chip will perform ADC. Which later convert the word into a series of data with

correspondent to the time. So when the user wishes to use the system, thus he or she must

produce the word with the correct pronunciation as in the training process. While for the

problem of the repetition of word used to train 2 different numbers, it will create an issue of

common output value for both of the number trained.

This issue will cause the system to enable to perform it duties perfectly as when the user use

the word that trained it will either display one of the number which mean there is a probability

of executing wrong command.

5.2 CONCLUSION

This project discussed the development of the voice recognition home automation system

which can be used to replace the old and conventional way to switch on the power of an

electrical device. This system consists of a voice recognition circuit, a microcontroller circuit

and a set of relay.

The voice recognition home automation system has been successfully developed and through

this project we have gained much experience especially in the field of applying the technique

of troubleshooting an electrical circuit and also in programming the microcontroller. This

project is a very simple project compare to any of those who are already in the industry and

commercialized but yet we hope that this project can be research on further to create a better

design that can be applied to a larger scale of controlling.

Besides that, we also hope that this project can be jumping stone for the application as one of

the smart home necessity. Besides the achieving of the main objective, by using this system, it

can help reduce any occurrence of getting shock due to the failure of the switch and it offer a

more safety way to turn on the switch. Moreover if this system is fully equipped in a house it

can reduce the addition of the wall switch and what left is only the plug point for user to plug

in their devices only.

5.3 APPENDICS

// This is declaration of variable used

char *someText1;

char *someText2;

char *someText3;

int state;

int plug1;

int plug2;

int plug3;

// module connections

char D_DataPort at PORTH;

sbit D_CS1 at LATJ0_bit;

sbit D_CS2 at LATJ1_bit;

sbit D_RS at LATJ2_bit;

sbit D_RW at LATJ3_bit;

sbit D_EN at LATJ4_bit;

sbit D_RST at LATJ5_bit; sbit GLCD_CS1_Direction at TRISJ0_bit;

sbit D_CS2_Direction at TRISJ1_bit;

sbit D_RS_Direction at TRISJ2_bit;

sbit D_RW_Direction at TRISJ3_bit;

sbit D_EN_Direction at TRISJ4_bit;

sbit D_RST_Direction at TRISJ5_bit;

// End module connections

void delay1S(){

// 0.5 seconds delay function

Delay_ms(500);

}

void delay2S(){

// 2.0 seconds delay function

Delay_ms(2000);

}

void main() {

ADCON1|=0x0F;

CMCON |= 7;

TRISD = 0xff; // port D as input

TRISA = 0x1f; // port A as analog input

TRISE = 0x00; // port E as output

PORTE = d_Init(); // Initialize

d_Fill(0xFF);

// Setting the Font

d_Set_Font(Character8x7, 8, 7, 32);

d_Write_Text("Welcome ", 67, 1, 2);

d_Write_Text("to", 90, 2, 2);

d_Write_Text("VRHAS", 75, 3, 2);

delay2S();

d_Fill(0xFF); // Clear GLCD

someText1="off"; // Initialize the display

someText2="off"; // Initialize the display

someText3="off"; // Initialize the display

while(1){

d_Write_Text("VRHAS", 75, 1, 2);

delay1S();

d_Write_Text("S1", 70, 2, 2);

d_Write_Text(someText1, 95, 2, 2);

d_Write_Text("S2", 70, 3, 2);

d_Write_Text(someText2, 95, 3, 2);

d_Write_Text("S3", 70, 4, 2);

d_Write_Text(someText3, 95, 4, 2);

delay1S();

// Distance sensor input

while (PORTA.F1==0) {}

// user input command

if (PORTD==0X01) state=1;

else if (PORTD==0X02) state=2;

else if (PORTD==0X03) state=3;

else if (PORTD==0x04) state=4;

else if (PORTD==0x05) state=5;

else if (PORTD==0x06) state=6;

else if (PORTD==0x07) state=7;

else if (PORTD==0x08) state=8;

switch (state) {

case 0:

break;

case 1:plug1= 1; // setting output

someText1= "on"; //update display

break;

case 2:plug1= 0; // setting output

someText1= "Off"; //update display

break;

case 3:plug2=1; // setting output

someText2= "On"; //update display

break;

case 4:plug2=0; // setting output

someText2= "Off"; //update display

35

break;

case 5:plug3=1; // setting output

someText3= "On";

break;

case 6:plug3=0; // setting output

someText3= "Off"; //update display

break;

case 7:plug1=0; // setting output

plug2=0; // setting output

plug3=0; // setting output

someText1= "Off"; //update display

someText2= "Off"; //update display

someText3= "Off"; //update display

break;

case 8:plug1=1; // setting output

plug2=1; // setting output

plug3=1; // setting output

someText1= "on"; //update display

someText2= "On"; //update display

someText3= "On"; //update display

break;

default:

break;

}

LATE.F1=plug1; // Actual output

LATE.F3=plug2; // Actual output

LATE.F5=plug3; // Actual output

}

}33

5.4 REFERENCES

1. Han Siong, J. Automated Home Lighting System. Degree.thesis. Faculty of

Electrical Engineering, Universiti Teknologi Malaysia. 2009.

2. en.wikipedia.org/wiki/Home_automation –

3. home-automation.org/

4. smart-home-automation-guide.com

5. Automation Testing By Saurabh Chandra “TATA MCGRAW HILLS”

6. www.atmel.com/atmel/acrobat/doc0265.pdf

7. http://wiki.answers.com/Q/What_is_Uln_2803_relay_driver