CHAPTER ONE

1.0 INTRODUCTION

The interesting thing about technology of nowadays is the ease in

communication. This is as a result of improvement in mobile communication

equipment through wireless technology. In communication network,

different means of channels are used such as co-axial cable, pair of wires

and fiber optic which constitute wired communication network. However,

the fastest growing network communication technologies are the use of

infra-red, blue tooth, radio waves and satellite.

A Transceiver is a transmitter-receiver circuit, a device that transmits

and receive analogue or digital signal simultaneously. In this case, it is used

as a remote control to switch ON/OFF a device. This circuit includes a

radio-frequency amplifier, which amplifies the power and output of the radio

frequency. Remote control is a system whereby control command and its

execution are separated by a relative significant distance.

1.1 PREVIOUS METHODOLOGY

Basically and empirically speaking, the hitherto usage of remote

control systems for home appliances made use of infra-red but depend on

line of sight which at times brings about inconveniences to some people at

home as result of short distance covered. In this case, the frequency employs

does not appreciate a long distance.

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1.2 PROPOSED METHODOLOGY

Radio wave comes into play due to its efficient utilization in

communication systems. It has high frequency and covers long distance.

Radio Frequency (RF) wave is used in this project to control a device by a

means of wireless communication between a transmitter and receiver (RF

transceiver).

1.3 MOTIVATION

The use of remote control has gained ground in recent time. System,

equipment and appliances at remote areas are being controlled through

wireless remote link, missiles and bombs are triggered through automated

remote control system in war fronts.

To move in trend of latest technology, and also considering the advantage of

radio wave wireless technology over a wired technology prompted me to

carry out a project on remote control system that makes use of FM wave.

1.4 OBJECTIVE

The aim is to design a portable remote control system that makes use

of FM radio wave to control a device (switching of an electrical bulb).

1.5 THESIS OUTLINE

This project is divided into five chapters. Chapter one deals with

introduction to wireless remote control system, objective, previous method

used, proposed method and motivation. Chapter two presents the literature

review and basic principle of the various components used. Design and

analysis is outlined in chapter three while chapter four contains the

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construction procedures, performance test and problem encountered. Lastly,

conclusion and recommendation on this project are presented in chapter five.

CHAPTER TWO

2.0 LITERATURE REVIEW

2.1 COMMUNICATION SYSTEM

Communication is defined as a process of transforming information

from one point in space to another point, that is, the destination or end user.

In other words, communication involves the sending of message signal and

receiving of the signal by users which should be able to understand and read

meaning to the information received. A complete communication system

would include a transmitter, a communication channel or medium over

which the signal is to be transmitted and a receiver to pick up the

information. The conversion of the signal from electrical to electrical pulse

for onward transmission is achieved by the use of a transducer. The

transducer converts the message to an electrical signal which could be a time

varying voltage or current. The block diagram of a communication system

can be shown below in figure 1.

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Block diagram

Fig. 2 Block diagram of communication system

2.2 TRANSMITTER

A transmitter is a piece of broadcasting equipment where a Radio

Frequency (RF) is generated, modulated, so that it can carry a meaningful

signal from one point to another, and send the same signal out through

radio wave by an antenna. Transmitter can be classified according to the

following categories.

-Types of modulation: modulation is a process designed to match the

transmitted signal to the properties of the channel through the use of carrier

wave. It can be Amplitude Modulation (AM), Frequency Modulation (FM)

or Phase Modulation (PM) transmitter.

-Service involved: a transmitter can be classified according to its service e.g.

Radio broadcasting TX e.g. Radio Kwara, Brilla FM, Ray Power.

Radio Telephony TX for relaying, telephone signals.

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Input message

Input electrical signal

Transmitted electrical signal

Received electrical signal

Output electrical signal

Output message

Input transducer

Transmitter

Transmi-ssion channel

Receiver Output transducer

Radio Telegraphy.

Radar Transmitter.

Satellite Transmitter.

-Range of frequency:

Long wave TX; below 300kz.

Medium wave TX; between 550 – 1550 KHz.

Short wave TX; between 3 – 30 MHz.

Microwave TX; beyond 10GHz.

UHF and VHF TX; used for television signal.

It is required to distinguish and define analog and digital transmission

1- Analog Transmission: Analog transmission implies continuity as

contrasted with digital transmission that is concerned with discrete states.

Many signals can be used in either the analog or digital sense, the means of

carrying the information being the distinguishing feature. The information

content of an analog signal is conveyed by the value or magnitude of some

characteristic(s) of the signal such as amplitude, frequency, or phase of a

voltage, the amplitude or duration of a pulse, the angular position of a shaft,

or the pressure of a fluid. Typical analog transmission are the signals we

hear on AM and FM radio and what we see (and hear) on television. In fact,

television is rather unique. The video itself uses amplitude modulation; the

sound subcarrier uses frequency modulation, and the color subcarrier

employs phase modulation. All are in analog formats.

2- Digital Transmission: The information content of a digital signal is

concerned with discrete states of the signal, such as the presence or absence

of a voltage. The output is usually open or closed position, or a hole or no

hole in certain positions on a card or paper tape. The signal is given meaning

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by assigning numerical values or other information to the various

combinations of the discrete states of the signal.

2.3 TRANSMISSION CHANNEL

The transmission channel is the medium of connection between

transmitter and receiver, bridging the distance from source to destination.

For instance, a pair of twisted wires, a coaxial cable, a radio wave and

optical fiber, each of the transmission media is subjected to degrading

influences such as noise, interference and distortion which tend to impair the

quality of the signal transmitted. (Bruce, 2005)

2.4 RECEIVER

The receiver must be designed to receive the best possible signal

transmitted by using signal processing technique, that is, amplification,

filtering and modulation in the case of a receiver. The receiver is to extract

the desired signal from the channel and deliver it to the output transducer.

The primary requirement for any communicating receiver is that it has

the ability to select the desired signal from among thousands of other present

signals and to provide sufficient amplification to recover the modulating

signal. These two requirements are referred to as selectivity and sensitivity.

2.5 WIRELESS RADIO COMMUNICATION SYSTEM

This involves the use of radio waves as the communication channel.

Messages are transmitted in form of electromagnetic wave to the destination.

The route of transmission depends on frequency use. Each transmission link

has its own frequency to prevent interference. The advantages of Wireless

radio communication over any other form are provision of mobility in

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communication, more flexible and easy to construct, higher accessibility,

and more so, it covers a long distance and it is used in trans-oceanic

communication and other places where wire line network is impossible.

2.6 MODULATION CONCEPT

In order to transmit information, a form of modulation is necessary.

The process of modulation is to vary some parameter of a basic

electromagnetic wave usually called the carrier wave. A Radio Frequency

(RF) signal is normally used as the original information in a form which is

unsuitable for distant transmission directly and it is necessary to convert it to

a high frequency by the process of modulation.

Over the years, various modulating methods have been devised and

are aimed at transmitting the required information as effectively as possible

with minimum amount of distortion. The primary factors to be considered

are signal power, bandwidth, distortion and noise power. Ultimately, it is the

ratio of signal power to noise power or output signal – to – noise ratio (S/N)

specified for the system which determines performance. The mathematical

expression for a sinusoidal carrier wave is expressed in eqn(1) below

v=VcSin(wct + Ф)

v=VcSin(2Пfct+Ф)……………………………………………(1)

Where Vc is the amplitude of the carrier, fc is the frequency of the carrier and

Ф is the phase of the carrier.

From the equation (1) above, the three characteristics that can be varied are

phase, amplitude, and frequency of the carrier wave. Hence, we have three

different type of modulation, namely Amplitude Modulation, Frequency

Modulation and Phase Modulation.

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2.7 AMPLITUDE MODULATION (AM)

In amplitude modulation, the information signal changes the

amplitude of the carrier wave whereby the frequency and the phase are kept

constant.

2.8 PHASE MODULATION (PM)

In this case, the phase of the carrier wave is varied in proportion to the

instantaneous phase of the information signal whereby the amplitude and the

frequency remain constant.

2.9 FREQUENCY MODULATION (FM)

The process of varying the frequency of a carrier wave in

proportion to a modulating signal is known as frequency modulation (FM).

The carrier amplitude of an FM wave is kept constant during modulation and

so the power associated with an FM wave is constant.

Frequency modulation has the following advantages over its

amplitude counterpart and these are as follow.

(1) All transmitted power in FM is useful whereas in AM most of power

transmitted is in carrier which serves no useful purpose.

(2) FM has high signal to noise ratio (S ⁄ N).

(3) Adjacent channel interference is unusual due to its guard band.

2.10 BASIC COMPONENT OF RADIO FREQUENCY (RF)

REMOTE CONTROL SYSTEM

A radio frequency remote control system consists of a transmitter

and a receiver circuit otherwise called (RF TRANSCEIVER). The block

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diagram of the transmitter and the receiver circuits are shown in fig (2) &

fig (3) below respectively.

The transmitter block diagram consists of a tone generator, ON ⁄

OFF switches (two in number), mixer circuits, carrier frequency

generator, RF amplifier, Transmitter and the power supply unit. While

the receiver circuit consists of RF receiver, demodulator circuit,

electromechanical switch, controlled device and the PSU.

Fig 2 Block diagram of a transmitter circuit

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TONE AON

TONE BOFF

ON/OFFCONTROL MIXER

RF AMP&TRANSMI-TTER

PSUCARRIER

FREQEUNCY GENERATOR

Fig. 3 Block diagram of the receiver circuit

2.11 TONE GENERATOR/ TONE DECODER

A device or component which produces tone with frequency which is

set by some external discrete components that is connected to, is known as a

tone generator. While a decoder is the device that responds to a tone with a

particular frequency range which must be within the bandwidth set by some

external discrete component that is connected to it.

A tone generator is an astable multivibrator, using 555 timer in this

project for the generation of tones. Tone A is determined by the choice of

R1, R2 and C while the Tone B is determined by the choice of R1, R’2 and C.

i.e. the tones A & B are function of resistors and the capacitor connected to

the 555 timer. The combinations of the three passive devices in each case

determine the oscillating frequency of the 555 timer. The following are the

general features of 555 timer.

(1.) Supply voltage between 4.5 and 18volts; supply current 3 to 6mA and a

rise/fall time of 100nsec.

PSU

RFReceiver

DemodulatorCircuit

Elecromechanicalswitch

ControlledDevice

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(2.) It can also withstand quite a bit of abuse

(3.) Highly stable centered frequency.

(4.) Both the rise and fall time of the output waveform is quite fast, typically

switching time being 100nsec.

(5.) Higher immunity to false signal.

11

Fig. 4 Basic schematic of 555 integrated circuit

2.12 555 TIMER AS A TONE GENERATOR (LM567)

The frequency of the tone is determined by the passive devices, that is, the

resistors and the capacitor. The generated frequency is given by

1

fₒ = 1.1RC ……………………………….. (2)

The resistor raises the current level of the output at pin8 of the IC. The

capacitor is used to select the bandwidth and reduce the noise so as to

improve the output.

12

R2

R1

8 57

Fig. 5 LM567 Connected As A Tone generator.

2.13 PHASE LOCKED LOOP (PLL)

A tone decoder is also called a frequency decoder. It is used to identify the

frequency of the intelligent signal. Phase Locked Loop (PLL) is a control

system. The output of the tone decoder is used to trigger the flip flop (F/F).

PLL generates a signal that has a fixed relation to the phase of a reference

signal. Phase-locked loop mechanisms may be implemented as either analog

or digital circuits. Both implementations use the same basic structure.

Fig. 6 PLL Characteristics

Both analog and digital PLL circuits include three basic elements:

a phase detector;

a variable electronic oscillator; and

a feedback path (which often includes a frequency divider).

2.14 PRE-EMPHASIS AND DE-EMPHASIS CIRCUIT

13

RI2

3

412

6

OutputInput

Pre-emphasis circuit is used at the transmitter to boost the modulating

base band frequency above 1KHz. De-emphasis is employed in the receiver

to restore the modulating base band signal back to it original power

distribution. Both have the effect of improving the signal to noise ratio(S/N).

Pre-emphasis is a high pass filter circuit while the De-emphasis is a low pass

filter circuit and they can be shown below in Fig (7)

Fig.7 Pre-emphasis circuit De-emphasis circuit

2.15 OSCILLATOR/ MODULATOR

Oscillator / modulator are circuits used for modulation. Frequency

modulation can be done using either the varactor diode method or transistor

reactance method. The illustration of this can be shown in the circuit below

in Fig8. The carrier wave signal is produced by a LC1 tuned circuit which is

connected to the collector terminal of a modulating transistor. The input

modulating signal (base band signal) is applied through its base terminal.

The variation in the conductivity of the transistor and as a result the tuned

circuit frequency is varied.

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C

R

R

C

A feedback capacitor C2 is connected between the collector and the

emitter terminal of modulating transmitter to restore any frequency shift or

drift that may occur during modulation.

Fig.8 Circuit diagram of Transistor Reactance Modulation.

2.16 DETECTOR

The RF modulated signal from the transmitter need to be detected by

removal of base band signal from the carrier wave. Super heterodyne

principle is used in this project. The idea of super heterodyne is to mix, to

frequencies together so as to produce a beat of frequency, which paves way

for the difference between the two. Generally, the term super heterodyne

refers to creating a beat frequency that is lower than the original signal.

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Base band signal

Modulator

Oscillator

Here, RF modulated signal that is captured by the receiver antenna is

amplified by the RF amplifier. RF mixer multiplies the signal from the

amplifier and a local oscillator produce more signals with different

frequencies. These signals are filtered allowing smallest frequencies to pass;

the intermediate frequency signal is amplified before it is sent to the

demodulator that extracts the base band signal.

Fig. 9 Block diagram of a Super- heterodyne Principle.

2.17 TA2003

A TA2003 is an AM/FM radio IC that is designed for AM/FM demodulation which is the IC works, using super heterodyne principle. The receiver stage was built around this IC. TA2003 IC possesses the following.

(1.) FM IFT, AM IFT and FM Detector Coil aren’t needed (2.) Operating supply voltage range; Vcc (opr) = 1.8~ 7v (Ta=25°C)(3.) Maximum rating (Ta=25°C)

(4.) Power dissipated of 70mW(5.) Storage Temp - 55 ~ 150°C.

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Antenna

RF AMP Mixer

IF Amplifier and filter

Demodulation

Base bandsignal

Local oscillator

Fig.10 Block Diagram of TA2003.

2.18 FLIP FLOP

A Flip flop (F/F) is a kind of bistable multivibrator with memory

ability. Data present on the input line just before a clock transition

determines the output state after the clock has changed. These flip flops are

available as inexpensive package IC’s and are always used that form. Today,

the term flip flop has come to generally denote non-transparent (clocked or

edge triggered) devices, while the simpler transparent ones are often referred

to as latches. The flip flop is used to switch the control device ON/OFF

depending on the nature of the received frequency (tone). A flip-flop is

controlled by one or two control signals and/or a gate or clock signal. The

output often includes the component as well as the normal output. The flip-

flops are implemented electronically; they required power and ground

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connections. A flip-flop can either be simple (transparent) or clocked. Flip-

flop can be built by two cross-coupled inverting elements transistor, or

NAND or NOR gates perhaps augmented by some enable / disable (gating)

mechanism.

Clocked devices are specially designed for synchronous (time- discrete)

system and therefore one such device ignores its inputs except at the

transition of a dedicated clock signal (known as clocking or pulsing,) this

causes the flip-flop to either change or retain its output signal based upon the

values of the input signal at the transition. Some flip-flop change output on

the rising edge of the clock, while the others on the falling edge. Clocked

(non transparent) flip flops are typically implemented as master slave

devices where two basic flip flops with some additional logics collaborate to

make it insensitive to spikes and noise between the short clock transitions;

nevertheless, they often include asynchronous clear or set inputs which may

be used to change the current output independent of the clock. Flip-flop is

further divided into types that have found common applicability in both

asynchronous and clock sequential systems: the SR (Set- Reset); D (Delay)

T (Toggle); JK types are the common ones; all of which may be synthesized

from other types by a few logic gate.

2.19 SET_ RESET FLIP FLOPS (SR FLIP- FLOPS)

Fig. 11 SR Flip flop symbol

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S Q

R Q

The most fundamental latch is the simple SR latch (or a simple SR

flip flop), where S and R stand for set and reset. It can be constructed from a

pair of cross – coupled (NOR) (negative OR) logic gates. The stored bit is

present on the output marked Q, normally, in storage mode, the S and R

inputs are both low, and feedback maintains the Q and Q output in a constant

state, with Q the complement of Q, if S (set) is pulsed high while R is held

low, then the Q output is forced high , and the stays high even after S returns

low; similarly, if R (reset) is pulsed high while S is held low, the Q output is

forced low and stay low even after R returns low.

SR Latch Operation

SR Action

00- Keep state

01- Q =0

10- Q =1

11- Unstable combinations

2.20 RELAY

A relay is a specialized electrical switch, whereby a high power device

can be controlled by a device of much lower power. It consists of an

electromagnetic coil and mechanical switch contacts that are pushed and

pulled by the electromagnet. The electromagnet requires a current of only a

few hundred milliamps produced by only a current of only a few volts,

where the contact may be subject to hundred of volts and tens of amps may

be pass through them .The switch therefore enables a small electric current

and voltage to control a much larger current and voltage.

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The type of relay employed in this project is the transistor driven

electromagnetic relay and it is shown in Fig.12 below. Freewheel diode is to

provide a path for reverse current generated by the coil.

Fig12. Transistor Driven Electromagnetic Relay

2.21 POWER SUPPLY UNIT

This is the source stable DC voltage supply to all components used in the

transmitting and receiving unit. The transmitting unit makes use of 12V DC

battery. In the case of receiving circuit, the input is 220V power supply from

the power holding company of Nigeria (PHCN) which is stepped down,

filtered, and regulated to 12V. It can be illustrated using the block diagram

shown below.

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Inputsignal

Freewheel diode

Fig.13 Block Diagram of the power supply unit.

2.22 TRANSFORMER

Control of signal from one voltage level to another is done using a

transformer and this is done with little lose of power. There are two closely

coupled coil identified as a primary secondary coil. The input coil is called

the primary and that of the output is called the secondary. There is no

electric connection between the coils but they are linked by alternating

magnetic field created in soft- iron core of the transformer .The ratio of the

voltages and the turns determine the current and the power at both side of

the transformer.

Vp Np

Therefore, ____ = _____-------------------------------------- (3)

Vs Ns

Where Vp = primary (input voltage) Np = Number of turns of primary coil

Ns = Number of turns of secondary coil

Vp = Secondary (output) voltage

And the power;

Vs Is =Vp Ip ------------------------------------------ (4)

Where Is = secondary output current

Ip = primary input current.

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Transformer

Rectifier Filter Voltage regulator

Input output

2.23 RECTIFIER

The process of converting an alternating current (ac) to pulsating direct

current is known as rectification. The most important rectifying component

is semiconductor diode. Full wave rectification is the most effective

rectification since it produces fewer ripples that can be easily filtered and

significantly, more efficient and cheaper. For the purpose of this project,

four diodes IN4001 are used. These diodes are silicon semiconductor

therefore 1.2V is used up in bridge rectification because each diode uses

0.6V when conducting.

Fig. 14 Circuit Diagram of a full wave Bridge Rectifier

22

Step down A.C

D

D D

D

Rectifiedvoltage

CHAPTER THREE

3.0 DESIGN ANALYSIS AND CALCULATION

3.1 Tone generating stage (555 timer is used)

It is connected for astable multivibrator operation to generate pulses.

T = 1/F. where T = pulse, F = frequency.

Generally, T = 0.693C (R1 + 2R2)

Therefore, F = 1

Chosen C1 = 0.1µF

For tone A put FA = 1 KHz

R1+2R2 = 1

R1+2R2 = 14,430Ω

But R1 is large compare to R2.

Assume R1 = 4R2

Hence, R1+2R2 = 14,430.01Ω = 6R2

R2 = 2.4KΩ

Therefore, R1 = 4 x 1.2 KΩ = 9620.00Ω

Nearest value R1 = 10kΩ.

For tone B put FB = 2 KHz

R1 + 2RI2 = 1

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0.693C1 (R1 + 2R2)

0.693x0.1x10-6x1x103

0.693 x 0.1 x 10-6 x 2 x 103

R1 + 2RI2 = 7215.00Ω

But R1 is large compare to R12

Assume R1 = 4R12

Therefore 4R12 + 2R1

2 = 7215Ω

6R12 = 7215Ω

R12 = 1.2KΩ

So R1 = 4 x 1.2 KΩ = 4810.00Ω

Taken the nearest value

R1 = 5KΩ

3.2 DESIGN FOR THE OSCILLATOR / MODULATING SECTION

Generally, Fc = 1

For a carrier frequency of 90MHz whereby C3 is a trimmer varies from

2p – 10pF

L1 = 1

Put C = 5pF

= 1

L1 = 0.693µH

C2 =?

(C2 + C6) = 1

C2 + C6 = 1

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2√LC

f2c x 4п2 x C3

(90 x 106) 2 x 4(3.1415) 2 x 5 x 10-12

4п2f2c L1

4(3.1415)2 x (90 x 106) 2 x 0.63 x 10-6

C2 + C6 = 5 x 10-12 = 5pF

But C6 is a trimmer chosen to be 20pF

C2 = 5pF – 2pF = 3pF

Therefore C2 = 3pF

C4 is a feedback capacitor of 10pF dr4 C4 = 10pF.

In order to eliminate waveform distortion i.e. to have a distortion-free

output, the emitter voltage is chosen to be half of the Vcc. i.e.

VE = ½ Vcc = 9/2 = 4.5V

For the transistor BC547, the maximum collector current

Ic = 100mA. Put Ic= 9.57mA.

Therefore RE = VE/IE but Ic ≈ IE

Therefore RE = 4.5 = 470 Ω

Therefore R3 = 470Ω

VB = VE + VBE = 4.5 + 0.7 = 5.2V

C5 is a coupling capacitor chosen to be 10pF.

Considering collector – emitter portion

Vcc = Vc + VCE

Therefore Vc = Vcc – VCE

From the data sheet, maximum VCE for BC547 = 45V

Chosen VCE = 4V

Therefore VC = 9 – 4 = 5V

VC = ICRC , IC is taken to be 1mA.

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9.57 x 10-3

RC = VC/IC = 5

= 5KΩ

Therefore R4 = 5KΩ

3.3 DESIGN FOR DETECTING STAGE

C16= C6= 10pF But, L2, C7 from the RF filter

FC = 1

4п2Fc2 = 1

L2 = 1

C7 is chosen to be 5pF

L2 = 1

= 0.63µH

L3, C8 form the local oscillator

But FLO = FC + IF

Where FLO = Local oscillator frequency

F C = Carrier frequency

IF = Intermediate frequency.

IF = 10.7MHz (for super heterodyne principle)

FC = 90MHz

FLO = 90MHz + 10.7MHz

= 100.7MHz

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1 x 10-3

2п√L2C7

L2C7

4п2Fc2C7

4(3.1415)2 x (90 x 106) 2 x 5 x 10-12

Therefore L3 = 1

C8 is chosen to be 5pF

L3 = 1 = 4.995 x 10-7 H

Therefore L3 = 0.5µH

Ca is a coupling capacitor for preventing the biasing of one stage from the

other. It is given as 20pF.

The tuned circuit of the local oscillator forms a quadrature oscillator with the

crystal frequency CF2.

3.4 DESIGN FOR THE DECODING STAGE.

Using F = 1

R = 1

C10 = 0.1uF, F1 1KHz, for tone A

R5 = 1/1.1 x 103 x 0.1 x 10-6 = 90,90.90Ω

R5 = 10KΩ

For tone B F2 2KHz, C11 = 0.1µF

R6 = 1 = 4545.45Ω

Therefore R6 = 5KΩ

3.5 DESIGN FOR THE RELAY CIRCUIT

27

4п2F2LO C8

4(3.1415)2 (100.7 x 106) 2 x 5 x 10-12

1.1RC

1.1RC

1.1 x 2 x 103 x 0.1 x 10-6

R7 =? But from the transistor T3 considering the base-emitter portion,

VB = IBRB + VBE

RB = VB – VBE/IB = R7

The relay employed is rated 10ADC6V, JZC-20F (4088) type. Shows

IC = 1A (manufacturer specification)

Using IB = IC/β, put β = 200 (TIP31) (T3), IC = 1A

IB = 1A = 0.005A = 5mA

Therefore RB = R7 = 6 – 0.6 = 1080Ω

Therefore R7 = 1080Ω =1KΩ

3.6 DESIGN CALCULATION FOR THE POWER

SUPPLY UNIT (PSU)

This unit design to provide 12Volts and 6volts outputs voltages.

T1 is a 220/9V, 50Hz with rating of 500mA. The peak inverse voltage

from the secondary of the transformer.

Vm = √2Vs

Where,

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200

0.005

Vs = secondary voltage, Vrms = 9V

Vm = √2 x 9 = 12.73V

VD = diode forward voltage drop.

Typically VD = 0.7V for most diodes.

Therefore for full wave bridge rectification

VDR = 2 x VD = 2 x 0.7 = 1.4V

For full wave rectification

Vdc = 2Vo /П

Vdc = 2 x 12.73 = 8.10V

For full wave bridge rectification, the peak inverse voltage PIV = Vo

Therefore PIV = 12.73V

Based on the analysis, the IN4001 diode was considered appropriate

for the bridge rectifying circuit due to its following ratings.

(i) Peak inverse voltage of 50V

(ii) Average rectified current of 1.0A

(iii) Maximum reverse current of 50µA.

Applying KVL to the first loop of the low voltage side of transformer

Vo = VD + VDR + dV

Where dV = ripple voltage

dV = Vo – Vdc – VDR = 12.73 – 8.10 – 1.4

dV = 3.23V

but I = CdV

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3.1415

dt

dV = I dt

For full wave rectification

dt = I/2f

Therefore dV = I

For Iload = 500mA, f = 50Hz, dV = 3.23V

C12 = I = 500 x 10-3

C12 = 1.5479 x 10-3F

Therefore the nearest value C12 = 2000µF

LED1 has an operating voltage and current of 2V and 10mA respectively

(manufacturer specification)

R8 = Vin – 2 = 9 – 2 = 700Ω

Since the maximum forward voltage for LED is between 1.2V and 3.2V

30

C

2fC12

2fdV 2 x 50 x 3.32

10 x 10-3 10 x 10-3

CHAPTER FOUR

4.0 CONSTRUCTION, PERFORMANCE TEST AND PROBLEM ENCOUNTERED

4.1 CONSTRUCTION: The requirements as designed in the previous chapter were purchased

and tested with a digital multimeter to determine their continuities and to

ascertain how good they are. Then, each of the components was arranged on

a project board to confirm that the components and circuit designs were

intact and possessed an ideal electric circuit.

The circuit layout was drawn for the project which is then used to

arrange the components on a clean portion of matrix Vero board before they

were all soldered to the board. But, before this, sockets were fixed for each

component of IC used in this project. Then, on the socket, each IC is

soldered. The importance of the socket is to prevent the heat of the soldering

iron from damaging the IC’s. The IC’s were placed on their sockets and the

project was tested.

A well sharpened, low heat dissipating soldering iron was used for the

transistors since heat damage transistors easily.

4.2 PERFORMANCE TEST

31

At the end of the construction, a bulb was connected to the receiving

unit to serve as a controlled device through a switch. The transmitting

unit was placed at a distance from the receiving unit. This was used to

control the switch of the bulb. Both switches were used to switch

ON/OFF the bulbs. For effective control a maximum distance of 6

meters apart was achieved.

4.3 PROBLEM ENCOUTERED

The following are the problems encountered during the design and

implementation of this project work.

(1) Selection of frequency amongst the FM range was not achieved on

time, owing to oscillator circuit used, especially in selecting values

for the passive component.

(2) During the process of soldering, some components got spoilt.

(3) Unavailability of some components used in the construction brought

about a delays during the design and construction

(4) The frequency of transmission changes easily during reconstruction

therefore, it is quite difficult to set the required transmitting

frequency.

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(5) The relay section gave a lot of problems owing to the switching

transistor that was not well biased.

CHAPTER FIVE

5.0 CONCLUSION AND RECOMMEDATION

5.1 CONCLUSION

The objective of this project which is the use of FM wave to control

a particular device of ones choice was achieved given a coverage distance up

to 6 meters, depending on the capacity of the transceiver. Tone A and Tone

B are the two factors that would determine if the device is to ON/OFF.

Radio Frequency (RF) remote control was used to control a particular device

of ones choice. Indeed is a means of controlling or modifying radio

frequency to control a particular device being electrical, mechanical or

electromechanical devices.

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5.2 RECOMMENDATION.

Having painstakingly perused this project, I hereby recommend that,

Radio Frequency (RF) remote control system should be modified to a

robotic remote control system for more effective performances.

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REFERENCES

1. Bruce Carlson, An Introduction to signal and Noise in electrical

communication (2nd edition) published by Elsevier India pvt ltd, Ring

Road, New- Delhi

2. M.G Scroggle (1996), Fundamentals of wireless and Electronics (10 th

edition) publication of Borland Ltd USA.

3. Theraja B.L and Theraja A.K (2001); A textbook of electrical

technology, publication Division of Schand and compand Ltd, Ram

Nigar, New Delhi.

4. onyVan Roon VA3AVR www.uoguelph.ca/~ antoon/gatgets/pll/pllhtml.

5. Semiconductor components industries, TIP41/TIP31 BC547 Data Sheet.

6. Semiconductor components industries – TA2003 Datasheet LLC, 1999,

www.national.com

7. www.radioelectronicschool.com

8. Power Supply Unit, www.electronicproject.com

9. Anthony R.H (2005), Relay Encyclopedia Encarta

10. Roger L Freeman, Fundamental of telecommunication (2nd edition) john

wiley and sons, inc , publication

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