remote controlled home appliances

Govt. Polytechnic College Dewas Page 1

R E M O T E C O N T R O L L I N G O F H O M E A P P L I A N C E S U S I N G R F M O D U L E

A MAJOR PROJECT REPORT

A Dissertation submitted for the partial fulfillment of the diploma of Engineering in Electronics &

Telecommunication

(Session-2014)

Guided By: - Submitted By:-

Mr. Ashish More Mayur Thakur

Mr. Jitendra Abhay (11125E03035)

Miss. Kavita Bhagat


ABSTRACT

Project title is REMOTE CONTROLLING OF HOME

APPLIANCES USING RF MODULE.

The main objective of this project is to develop a home automation

system with a RF controlled remote. As technology is advancing so houses

are also getting smarter. Modern houses are gradually shifting from

conventional switches to centralized control system, involving RF controlled

switches. Presently, conventional wall switches located in different parts of

the house makes it difficult for the user to go near them to operate. Even

more it becomes more difficult for the elderly or physically handicapped

people to do so. Remote controlled home automation system provides a

simpler solution with RF technology.

In order to achieve this, a RF remote is interfaced to the microcontroller on

transmitter side which sends ON/OFF commands to the receiver where

loads are connected. By operating the specified remote switch on the

transmitter, the loads can be turned ON/OFF remotely through wireless

technology


CHAPTER: - 1

INTRODUCTION

In this project REMOTE CONTROLLING OF HOME APPLIANCES

USING RF MODULE We show that how we control electrical appliances

with the help of WIRELESS REMOTE (Radio Frequency Module).

As we press the switch from transmitter end then immediate data

is to be transmitting in the air. Data receive in air by the Radio frequency

module and proceed to the electrical appliances circuit. In this project we

use two circuits one is transmitter and second is receiver.

In the transmitter part we send the RF code by the transmitter by

4 switches and in the receiver we use four relay coils for electrical output.

As we want to switch on any electrical appliances we press the switch of the

transmitter. As the switch is pressed, data is to be transmitting by the radio

frequency module.

In this project we use 433 Mhz modules for data transmission. We

use one encoder ic for data transmission. All the switches are connected to

the encoder. Encoder ic get the data from the switch and transmit the data

in serial by the RF transmitter. In the receiver circuit we use RF module to

get the data and decoded by the decoder. Decoder delivers the data into 4

bit and we use further control circuit to switch on/off.


CHAPTER: - 2

BLOCK DIAGRAM AND ITS DESCRIPTION

2.1 Basic Block Diagram

Fig 2.1 Basic Block Diagram

Switches

Parallel data

Encoder

HT12E

Serial data

RF Transmitter Serial data RF Receiver

Serial data

Parallel data

Decoder

HT12D

Relays Home

Appliances


2.2 Block Diagram Description

The basic block diagram of the REMOTE CONTROLLING OF

HOME APPLIANCES USING RF MODULE is shown in the above figure.

Mainly this block diagram consists of the following essential blocks.

1. Encoder HT12E

2. RF Transmitter

3. RF Receiver

4. Decoder HT12D

5. Relays

1. Encoder HT12E :-

The encoders are a series of CMOS LSIs for remote control

system applications. They are capable of encoding information which

consists of N address bits and 12_N data bits. Each address/data input can

be set to one of the two logic states. The programmed addresses/data are

transmitted together with the header bits via an RF or an infrared

transmission medium upon receipt of a trigger signal. The capability to

select a TE trigger on the HT12E or a DATA trigger on the HT12A further

enhances the application flexibility of the 212 series of encoders. The

HT12E additionally provides a 38 kHz carrier for infrared systems.

2. RF Transmitter :-

This radio frequency (RF) transmission system employs

Amplitude Shift Keying (ASK) with transmitter/receiver (Tx/Rx) pair

operating at 434 MHz. The transmitter module takes serial input and

transmits these signals through RF


3. RF Receiver :-

The RF receiver also operates at 433.92MHz, and has a

sensitivity of 3uV. The ASK receiver operates from 4.5 to 5.5 volts-DC, and

has both linear and digital outputs. It receives the data from the transmitter

and sends to the decoder IC

4. Decoder HT12D :-

The 212 decoders are a series of CMOS LSIs for remote

control system applications. For proper operation, a pair of encoder/decoder

with the same number of addresses and data format should be chosen. The

decoders receive serial addresses and data from programmed 212 series of

encoders that are transmitted by a carrier using an RF or an IR transmission

medium. They compare the serial input data three times continuously with

their local addresses. If no error or unmatched codes are found, the input

data codes are decoded and then transferred to the output pins. The 212

series of decoders are capable of decoding information that consists of N

bits of address and 12_Nbits of data. Of this series, the HT12D is arranged

to provide8 address bits and 4 data bits, and HT12F is used to decode 12

bits of address information.

5. Relays :-

A relay is an electrically operated switch. It allows one circuit

to switch a second circuit which is completely separated from the first. The

output from the driver IC is send to the corresponding relays which thus

results in its excitation and gets activated. As a result it controls the

corresponding home appliance.


CHAPTER: - 3

CIRCUIT DESCRIPTION: There are two main parts of the circuits.

Transmitter Circuit

Receiver Circuit

3.1 Transmitter Circuit:-

Fig 3.1 Transmitter Circuit Diagram


3.2 Receiver Circuit:-

Fig 3.2 Receiver Circuit Diagram


Fig.3.3 RELAY CONNECTION FOR EACH APPLIANCE


CHAPTER: - 4

WORKING

Our project as mentioned earlier is aimed at controlling 4

home appliances using a RF Module. It controls the on/off process of

the appliances interfaced to this circuit. The devices are operated

using the keypads 1-4. It performs the function of an RF transmitter

which sends Radio frequency after encoding information which

consists of N address bits and 12_N data bits by an encoder IC

HT12E. Each address/data input can be set to one of the two logic

states. The programmed addresses/data are transmitted together

with the header bits via an RF with a carrier of 315 MHz to

433.92 MHz frequency.

These series signals are received by RF Receiver these

are designed to receive signals of 315 MHz to 433.92 MHz. It senses

the received output and demodulates them. Therefore original

signals are retrieved after demodulation. The output from the

receiver is then sent to the decoder IC HT12D. HT12D is

programmed so as to decode the encoded signal from transmitter. It

decodes the signals from RF receiver and thereby it recognizes the

device to be functioned.


The inputs and outputs are thus controlled. The decoded output from

the decoder IC is obtained by the Hex Inverter CD4049.

The CD4049 is a CMOS logic chip that is six

independent inverters. It is used for interfacing and to make simple

clock pulse generators and oscillators. Connect two in series to make

a non-inverting buffer. The input-signal high level (VIH) can exceed

the VCC supply voltage when these devices are used for logic-level

conversions. The output of the hex inverter is applied to the 4013 d

flip flop. The outputs Q and Q dash switch their logic states

alternately in response to the set/reset or the clock pin out inputs.

When a clock frequency is applied at the CLK input, the output Q and

Q dash change states alternately as long as the clocks keep repeating.

Similarly the Q and Q dash status can be changed

by manually pulsing the set or the reset pins with a positive voltage

source. Normally the set and the reset pin should be connected to the

ground when not utilized.

Here the signals from 4013 d flip flop are given to the

base of the corresponding transistor. Thus, the external circuit gets

grounded at one end while it is provided +Vcc at its other end. So, the

circuit gets completed and starts operating. A total of four relays are

connected to the output pins of d flip flop IC 4013. When the relay

gets excited from the outputs appearing at the 4013 IC, it gets

activated.


Thus the coil gets energized and the COM gets connected to the N/O

contact and the AC mains circuit gets completed and the appliance

starts working.

Components used:-

7805 Voltage Regulator

HT12E ENCODER IC.

HT12D DECODER IC.

RF TRANSMITTER MODULE.

RF RECEIVER MODULE

4 DIFFERENT SWITCH

4013 ( D flip flop)

4049 ( hex inverter)

548 Transistors

Resistors

Capacitors

Relays

IN 4007 Diodes

LEDs

Aerial Antenna


4.1 HT12E Encoder IC :-

HT12E is a 212 series encoder IC (Integrated Circuit) for

remote control applications. It is commonly used for radio frequency (RF)

applications. HT12E simply converts 12 bit parallel data in to serial output

which can be transmitted through a RF transmitter. These 12 bit parallel

data is divided in to 8 address bits and 4 data bits. By using these address

pins we can provide 8 bit security code for data transmission and multiple

receivers may be addressed using the same transmitter.

Fig.4.1 (a) Block Diagram of HT12E


HT12E is able to operate in a wide voltage range from 2.4V

to 12V and has a built in oscillator which requires only a small external

resistor. Its power consumption is very low, standby current is 0.1A at 5V

VDD and has high immunity against noise. It is available in 18 pin DIP (Dual

Inline Package) and 20 pin SOP (Small Outline Package) as given below.

4.1.1 PIN Diagram and Description:-

Fig.4.1 (b) PIN Diagram of HT12E


VDD and VSS are power supply pins which are used to connect

positive and negative of the power supply respectively.

OSC1 and OSC2 are used to connect external resistance for the

internal oscillator. OSC1 is the oscillator input pin and OSC2 is the

oscillator output pin.

Fig.4.1 (c) Oscillator of HT12E

TE is used for enabling the transmission and is an active low input.

A0 A7 are the input address pins. By using these pins we can

provide a security code for the data. These pins can be connected to

VSS or left open.

D8 D11 are the input data pins. These pins can be connected to

VSS or may left open for sending LOW and HIGH respectively.

DOUT It is the serial data output of the encoder and can be

connected to a RF transmitter.


4.1.2 Working of HT12E:-

The HT12E 212 series encoder starts a 4 word transmission

cycle upon receiving transmission enable signal on TE input. This output

cycle will repeat as long as the transmission is enabled. When the

transmission enable (TE) signal switches to HIGH, the encoder output

completes the current cycle and stops as shown above. The encoder will be

in the Standby mode when the transmission is disabled.

4.1.3 FEATURES:-

Operating voltage

_2.4V~5V for the HT12A

_2.4V~12V for the HT12E

Low power and high noise immunity CMOS technology

Low standby current: 0.1_A (typ.) at VDD=5V

HT12A with a 38kHz carrier for infrared transmission medium


4.2 HT12E Decoder IC :-

HT12D is a 212 series decoder IC (Integrated Circuit) for

remote control applications manufactured by Holtek. It is commonly used for

radio frequency (RF) wireless applications. By using the paired

HT12E encoder and HT12D decoder we can transmit 12 bits of

parallel data serially. HT12D simply converts serial data to its input (may be

received through RF receiver) to 12 bit parallel data. These 12 bit parallel

data is divided in to 8 address bits and 4 data bits. Using 8 address bits we

can provide 8 bit security code for 4 bit data and can be used to address

multiple receivers by using the same transmitter.

Fig.4.2 (a) Block Diagram of HT12D


HT12D is a CMOS LSI IC and is capable of operating in a

wide voltage range from 2.4V to 12V. Its power consumption is low and

has high immunity against noise. The received data is checked 3 times for

more accuracy. It has built in oscillator; we need to connect only a small

external resistor. As HT12E, it is available in 18 pin DIP (Dual Inline

Package) and 20 pin SOP (Small Outline Package) as given below.

4.2.1 PIN Diagram and Description:-

Fig.4.2 (b) PIN Diagram of HT12D


VDD and VSS are used to provide power to the IC, Positive and

Negative of the power supply respectively. As I said earlier its

operating voltage can be in the range 2.4V to 12V.

OSC1 and OSC2 are used to connect external resistor for internal

oscillator of HT12D. OSC1 is the oscillator input pin and OSC2 is the

oscillator output pin as shown in the figure below.

Fig.4.2 (c) Oscillator of HT12E

A0 A7 are the address input pins. Status of these pins should match

with status of address pin in HT12E (used in transmitter) to receive

the data. These pins can be connected to VSS or left open.

DIN is the serial data input pin and can be connected to a RF receiver

output.

D8 D11 are the data output pins. Status of these pins can be VSS or

VDD depending upon the received serial data through pin DIN.

VT stands for Valid Transmission. This output pin will be HIGH when

valid data is available at D8 D11 data output pins.


4.2.2 Working of HT12D:-

HT12D decoder will be in standby mode initially i.e.,

oscillator is disabled and a HIGH on DIN pin activates the oscillator. Thus

the oscillator will be active when the decoder receives data transmitted by

an encoder. The device starts decoding the input address and data. The

decoder matches the received address three times continuously with the

local address given to pin A0 A7. If all matches, data bits are decoded and

output pins D8 D11 are activated. This valid data is indicated by making

the pin VT (Valid Transmission) HIGH. This will continue till the address

code becomes incorrect or no signal is received.


4.2.3 FEATURES:-

Operating voltage: 2.4V~12V

Low power and high noise immunity CMOS technology

Low standby current

Capable of decoding 12 bits of information

Binary address setting

Received codes are checked 3 times

Address/Data number combination

_ HT12D: 8 address bits and 4 data bits

_ HT12F: 12 address bits only

4.3 RF Module:-

An RF module (radio frequency module) is a (usually) small

electronic circuit used to transmit and/or receive radio signals on one of a

number of carrier frequencies. RF modules are widely used in electronic

design owing to the difficulty of designing radio circuitry. Good electronic

radio design is notoriously complex because of the sensitivity of radio

circuits and the accuracy of components and layouts required achieving

operation on a specific frequency.

Design engineers will design a circuit for an application which

requires radio communication and then "drop in" a radio module rather than

attempt a discrete design, saving time and money on development.


Fig.4.3 (a) RF Modules

RF modules are most often used in medium and low volume

products for consumer applications such as garage door openers, wireless

alarm systems, industrial remote controls, smart sensor applications,

and wireless home automation systems.

They are sometimes used to replace older infra

red communication designs as they have the advantage of not requiring

line-of-sight operation. Several carrier frequencies are commonly used in

commercially-available RF modules, including 433.92 MHz, 315 MHz,

868 MHz and 915 MHz. These frequencies are used because of national

and international regulations governing the used of radio for communication.


4.3.1 Type of RF Modules:-

The term RF module can be applied to many different types, shapes and

sizes of small electronic sub assembly circuit board. It can also be applied

to modules across a huge variation of functionality and capability. Most

standard, well known types are covered here:

Transmitter module

Receiver module

Transceiver module

A). Transmitter modules:-

An RF transmitter module is a small PCB sub-

assembly capable of transmitting a radio wave and modulating that wave to

carry data. Transmitter modules are usually implemented alongside a micro

controller which will provide data to the module which can be transmitted. it

is also a part of transreceiver.

B). Intelligent transmitter modules:-

An intelligent transmitter module is the same as a

transmitter module, but it is often made with an on-board micro controller to

handle radio data packetisation negating the need for an external micro

controller to convert data or Manchester encode it. This type of module is

usually used for designs requiring a quick route to market or if the designer

has little experience designing with radio.


C). Super heterodyne and super regenerative receiver:-

There are two types of RF receiver modules: super

heterodyne receivers and super-regenerative receivers. Super-regenerative

modules are usually low cost and low power designs using a series of

amplifiers to extract modulated data from a carrier wave.

Super-regenerative modules are generally imprecise as

their frequency of operation varies considerably with temperature and power

supply voltage. Super heterodyne receivers have a performance advantage

over super-regenerative; they offer increased accuracy and stability over a

large voltage and temperature range. This stability comes from a fixed

crystal design which in turn leads to a comparatively more expensive

product.

4.3.2 Transmitter Working:-


4.3.3 RF transmitter Pin description:-

Pin

No Function Name

1 Ground (0V) Ground

2 Serial data input pin Data

3 Supply voltage; 5V Vcc

4 Antenna output pin ANT

4.3.4 Receiver working:-


4.3.5 RF Receiver Pin description:-

Pin

No Function Name


2 Serial data output pin Data

3 Linear output pin; not connected NC





8 Antenna input pin ANT

4.3.6 Main factors affecting RF Module performance:-

As with any other radio-frequency device, the performance

of an RF module will depend on a number of factors. For example, by

increasing the transmitter power, a larger communication distance will be

achieved. However, this will also result in a higher electrical power drain on

the transmitter device, which will cause shorter operating life for battery

powered devices. Also, using a higher transmit power will make the system

more prone to interference with other RF devices, and may in fact possibly

cause the device to become illegal depending on the jurisdiction.


Correspondingly, increasing the receiver sensitivity will also

increase the effective communication range, but will also potentially cause

malfunction due to interference with other RF devices.

The performance of the overall system may be improved by

using matched antennas at each end of the communication link, such as

those described earlier.

Finally, the labeled remote distance of any particular

system is normally measured in an open-air line of sight configuration

without any interference, but often there will be obstacles such as walls,

floors, iron construction to absorb the radio wave signals, so the effective

operational distance will in most practical instances be less than specified.

4.3.7 FEATURES:-

RF Transmitter Features

Frequency Range: 433.92 MHZ.

Supply Voltage: 3~12V

Output Power : 4~16dBm

Circuit Shape: Saw

Supply Current: 3.5mA


RF Receiver Features

Receiver Frequency: 433.92 MHZ

Typical sensitivity: -105dBm

Supply Current: 3.5mA

Frequency: 1MHz

Low power consumption

Operation voltage: 5 Volts

4.4 7805 Voltage Regulator:-

7805 is a voltage regulator integrated circuit. It is a

member of 78xx series of fixed linear voltage regulator ICs. The voltage

source in a circuit may have fluctuations and would not give the fixed

voltage output. The voltage regulator IC maintains the output voltage at a

constant value. The xx in 78xx indicates the fixed output voltage it is

designed to provide. 7805 provides +5V regulated power supply.

Capacitors of suitable values can be connected at input and output pins

depending upon the respective voltage levels.

4.4.1 Pin Description of 7805 voltage regulator:-

Pin No Function Name

1 Input voltage (5V-18V) Input


3 Regulated output; 5V (4.8V-5.2V) Output


Fig.4.4 7805 Voltage Regulator

4.4.2 Advantages:-

7805 IC do not require additional components to provide a constant,

regulated source of power, making them easy to use, as well as

economical and efficient uses of space. Other voltage regulators may

require additional components to set the output voltage level, or to assist

in the regulation process. Some other designs (such as a switched) may

need substantial engineering expertise to implement.


7805 IC have built-in protection against a circuit drawing too much

power. They have protection against overheating and short-circuits,

making them quite robust in most applications. In some cases, the

current-limiting features of the 7805 device can provide protection not

only for the 7805 itself, but also for other parts of the circuit.

4.4.3 Disadvantages:-

The input voltage must always be higher than the output voltage by

some minimum amount (typically 2.5 volts). This can make these devices

unsuitable for powering some devices from certain types of power

sources (for example, powering a circuit that requires 5 volts using 6-volt

batteries will not work using a 7805).

As they are based on a linear regulator design, the input current

required is always the same as the output current. As the input voltage

must always be higher than the output voltage, this means that the total

power (voltage multiplied by current) going into the 78xx will be more

than the output power provided. The extra input power is dissipated as

heat. This means both that for some applications an adequate heat

sink must be provided, and also that a (often substantial) portion of the

input power is wasted during the process, rendering them less efficient

than some other types of power supplies. When the input voltage is

significantly higher than the regulated output voltage (for example,

powering a 7805 using a 24 volt power source), this inefficiency can be a

significant issue.


4.5 4013 ( D flip flop):-

4.5.1 General Description:-

The CD4013B dual D-type flip-flop is a monolithic

complementary MOS (CMOS) integrated circuit constructed with N- and P-

channel enhancement mode transistors. Each flip-flop has independent

data, set, reset, and clock input sand Q and Q outputs. These devices

can be used for shift register applications, and by connecting Q output to

the data input, for counter and toggle applications.

Fig.4.5 Pin Diagram of 4013 (D flip flop)

The logic level present at the D input is transferred to the Q

output during the positive-going transition of the clock pulse. Setting or

resetting is independent of the clock and is accomplished by a high level on

the set or reset line respectively.


The D-type has four inputs. These are:

DATA input: This is connected either to a LOW voltage, logic 0, or to

a HIGH voltage, logic 1.

CLOCK input: The triangle, next to the CLOCK input shows that it

is edge-triggered, that is, it responds to sudden changes in voltage,

but not to slow changes or to steady logic levels. The CLOCK input of

the 4013 D-type bistable is rising-edge triggered, meaning that it

responds only to a sudden change from LOW to HIGH.

Usually, the CLOCK input is connected to a subsystem which delivers

pulses. To test the 4013, you will need to build an astable.

SET input: The SET input is normally held LOW. When it is pulsed

HIGH, the outputs of the bistable are forced immediately to the SET

state, , .

RESET input: The RESET input is normally held LOW. When it is

pulsed HIGH, the outputs of the bistable are forced immediately to the

RESET state, ,


4.5.2 Connection Diagram:-

4.5.3 Logic Diagram:-


4.5.4 Features:-

Wide supply voltage range: 3.0V to 15V

High noise immunity: 0.45 VDD (typ.)

Low power TTL: fan out of 2 driving 74L compatibility: or 1 driving

74LS

4.6 4049 ( hex inverter):-

The CD4049 is a CMOS logic chip, which are six

independent inverters. It is used for interfacing and to make simple clock

pulse generators and oscillators. Connect two in series to make a non-

inverting buffer. The input-signal high level (VIH) can exceed the VCC

supply voltage when these devices are used for logic-level conversions.

These devices are intended for use as CMOS to DTL/TTL converters and

can drive directly two DTL/TTL loads. The Maximum power supply must not

exceed 18 volts.

Fig.4.6 Pin Diagram of 4049 (hex inverter)


4.6.1 The pin assignments of DIP 16 as CD4049:-

4.6.2 Features:-

Wide supply voltage range: 3V to 15V

Direct drive to 2 TTL loads at 5.0V over full temperature range.

High source and sink current capability

Special input protection permits input voltage greater than Vdd.


4.7 548 NPN Transistors:-

BC548 is general purpose silicon, NPN, bipolar junction

transistor. It is used for amplification and switching purposes. The current

gain may vary between 110 and 800. The maximum DC current gain is 800.

Its equivalent transistors are 2N3904 and 2SC1815. These

equivalent transistors however have different lead assignments. The

variants of BC548 are 548A, 548B and 548C which vary in range of current

gain and other characteristics.

Fig.4.7 (a) 548 NPN Transistor


The transistor terminals require a fixed DC voltage to

operate in the desired region of its characteristic curves. This is known as

the biasing. For amplification applications, the transistor is biased such that

it is partly on for all input conditions. The input signal at base is amplified

and taken at the emitter. BC548 is used in common emitter configuration for

amplifiers. The voltage divider is the commonly used biasing mode. For

switching applications, transistor is biased so that it remains fully on if there

is a signal at its base. In the absence of base signal, it gets completely off.

Fig.4.7 (b) DC Current Gain


4.8 Relay:-

A relay is an electrically operated switch. It allows one circuit to

switch a second circuit which is completely separated from the first. For

example a low voltage battery circuit can use a relay to switch a 230V AC

mains circuit. There is no electrical connection inside the relay between the

two circuits; the link is magnetic and mechanical.

Fig.4.8 (a) Electromagnetic relay operation

In the above figure, when controlling switch is closed, current flows through

the coil and thus, magnetic field is produced. The resulting magnetic field

attracts an armature that is mechanically linked to a set of contacts.


The movement makes a connection with a fixed contact and circuit gets

completed. When the current to the coil is switched off, the armature is

returned by a force approximately half as strong as the magnetic force to its

relaxed position and the connection is broken.

The relay's switch connections are usually labeled COM, N/C and N/O as

shown in figure 11 above:

COM = Common, always connect to this; it is the moving part of the

switch.

N/C = Normally Closed, COM is connected to this when the relay coil

is off.

N/O = Normally Open, COM is connected to this when the relay coil is

on.

Connect to COM and N/O if you want the switched circuit to be on

when the relay coil is on.

Connect to COM and N/C if you want the switched circuit to be on

when the relay coil is off.

4.8.1 Application:-

Relays are used as:

Amplifying a digital signal, switching a large amount of power with a

small operating power. Some special cases are:

o A telegraph relay, repeating a weak signal received at the end of

a long wire


o Controlling a high-voltage circuit with a low-voltage signal, as in

some types of modems or audio amplifiers,

o Controlling a high-current circuit with a low-current signal, as in

the starter solenoid of an automobile,

Detecting and isolating faults on transmission and distribution lines by

opening and closing circuit breakers (protection relays)

4.9 IN4007 Diode:-

The most common function of a diode is to allow an electric

current to pass in one direction (called the diode's forward direction), while

blocking current in the opposite direction (the reverse direction). Thus, the

diode can be viewed as an electronic version of a check valve.

This unidirectional behavior is called rectification, and is

used to convert alternating current to direct current, including extraction of

modulation from radio signals in radio receiversthese diodes are forms

of rectifiers.

Fig.4.9 Device package and Symbol of diode


However, diodes can have more complicated behavior than this

simple onoff action, due to their nonlinear current-voltage characteristics.

Semiconductor diodes begin conducting electricity only if a certain threshold

voltage or cut-in voltage is present in the forward direction (a state in which

the diode is said to be forward-biased). The voltage drop across a forward-

biased diode varies only a little with the current, and is a function of

temperature; this effect can be used as a temperature sensor or voltage

reference.

Semiconductor diodes' currentvoltage characteristic can be

tailored by varying the semiconductor materials and doping, introducing

impurities into the materials. These are exploited in special-purpose diodes

that perform many different functions. For example, diodes are used to

regulate voltage (Zener diodes), to protect circuits from high voltage surges

(avalanche diodes), to electronically tune radio and TV receivers (varactor

diodes), to generate radio frequency oscillations (tunnel diodes, Gunn

diodes, IMPATT diodes), and to produce light (light emitting diodes).

V-I Characteristics of Diode:-


4.10 Aerial Antenna:-

An aerial antenna is an electrical device which

converts electric power into radio waves, and vice versa. It is usually used

with a radio transmitter or radio receiver. In transmission, a radio transmitter

supplies an electric current oscillating at radio frequency (i.e. a high

frequency alternating current (AC) to the antenna's terminals, and the

antenna radiates the energy from the current as electromagnetic (radio

waves). In reception, an antenna intercepts some of the power of an

electromagnetic wave in order to produce a tiny voltage at its terminals that

is applied to a receiver to be amplified.

Antennas are essential components of all equipment that

uses radio. They are used in systems such as broadcasting, broadcast, two-

way radio, communications receivers, radar, cell phones, and satellite

communications, as well as other devices such as garage door

openers, wireless microphones, Bluetooth enabled devices, wireless

computer networks, baby monitors, and RFID tags on merchandise.


Typically an antenna consists of an arrangement of

metallic conductors (elements), electrically connected (often through a

transmission) to the receiver or transmitter. An oscillating current

of electrons forced through the antenna by a transmitter will create an

oscillating magnetic field around the antenna elements, while the charge of

the electrons also creates an oscillating electric along the elements.

These time-varying fields radiate away from the antenna into

space as a moving transverse electromagnetic field wave. Conversely,

during reception, the oscillating electric and magnetic fields of an incoming

radio wave exert force on the electrons in the antenna elements, causing

them to move back and forth, creating oscillating currents in the antenna.

Fig.4.10 Radiation Pattern of Aerial Antenna


4.11 Resistor:-

Resistors determine the flow of current in an electrical circuit.

Where there is high resistance in a circuit the flow of current is small, where

the resistance is low the flow of current is large. Resistance, voltage and

current are connected in an electrical circuit by Ohms Law. When a

resistor is introduced to a circuit the flow of current is reduced. The higher

the value of the resistor the smaller/lower the flow of current.

Fig.4.11 Four Band Resistor

Resistors are used for regulating current and they resist the

current flow and the extent to which they do this is measured in ohms ().

Resistors are found in almost every electronic circuit. The most common

type of resistor consists of a small ceramic (clay) tube covered partially by a

conducting carbon film. The composition of the carbon determines how

much current can pass through.


Resistors are too small to have numbers printed on them

and so they are marked with a number of colored bands. Each color stands

for a number. Three color bands show the resistors value in ohms and the

fourth shows tolerance. Resistors can never be made to a precise value and

the tolerance band (the fourth band) tells us, using a percentage, how close

the resistor is to its coded value.


4.12 Capacitor:-

A capacitor (originally known as a condenser) is

a passive two-terminal electrical component used to store energy electro

statically in an electric field. The forms of practical capacitors vary widely,

but all contain at least two electrical conductors (plates) separated by

a dielectric (i.e., insulator). The conductors can be thin films of metal,

aluminum foil or disks, etc. The 'non conducting' dielectric acts to increase

the capacitor's charge capacity. A dielectric can be glass, ceramic, plastic

film, air, paper, mica, etc. Capacitors are widely used as parts of electrical

circuits in many common electrical devices. Unlike a resistor, a capacitor

does not dissipate energy. Instead, a capacitor stores energy in the form of

an electrostatic field between its plates.

Fig.4.12 Ceramic and electrolytic capacitors

When there is a potential difference across the conductors

(e.g., when a capacitor is attached across a battery), an electric

field develops across the dielectric, causing positive charge (+Q) to collect

on one plate and negative charge (-Q) to collect on the other plate.


If a battery has been attached to a capacitor for a sufficient

amount of time, no current can flow through the capacitor. However, if an

accelerating or alternating voltage is applied across the leads of the

capacitor, a displacement current can flow.

An ideal capacitor is characterized by a single constant

value for its capacitance. Capacitance is expressed as the ratio of the

electric charge (Q) on each conductor to the potential difference (V)

between them. The SI unit of capacitance is the farad (F), which is equal to

one coulomb per volt (1 C/V). Typical capacitance values range from about

1 pF (1012 F) to about 1 mF (103 F).

Selection of the correct type of capacitor is important in all

applications. Just satisfying capacitances and voltage requirements is

usually insufficient. In previous chapters, capacitors have been used to

perform the following functions:

Turn-off snubbering

dv/dt snubbering

Transient voltage sharing of series connected devices

Switched-mode power supply output filtering and dc blocking

Dc rail splitting for multilevel converters

Power L-C filters

as well as

Ac power factor correction and compensation

Dc rail decoupling

Voltage multipliers

motors for single phase supplies


CHAPTER: - 5

PCB Fabrication and Layout Designing

PCB FABRICATION TECHNIQUE:-

The first step of assembling is to produce a printed circuit board.

The fabrication of the program counter plays a crucial role in the electronic

field. The success of the circuit is also dependent on the PCB. As far as the

cost is concerned, more than 25% of the total cost is for the PCB design

and fabrication.

The board is designed using a personal computer. The layout is

drawn using the software Eagle 5.6. The layout is printed in a buffer

sheet using a laser procedure. First, a negative screen of the layout is

prepared with the help of a professional screen printer. Then the copper

clad sheet is kept under this screen. The screen printing ink is poured on

the screen and brushed through the top of the screen. The printed board is

kept under shade for few hours till the ink becomes dry.

The etching medium is prepared with the un-hydrous ferric

chloride water. The printed board is kept in this solution till the exposed

copper dissolves in the solution fully. After that the board is taken out and

rinsed in flowing water under a tap. The ink is removed with solder in order

to prevent oxidation.


Another screen, which contains component side layout, is

prepared and the same is printed on the component side of the board. A

paper epoxy laminate is used as the board. Both the component and the

track layout of the peripheral PCB is given at the end of this report.

PCB LAYOUT:-

(a) (b)

Fig.5 (a) Layout of receiver circuit and

(b) Layout of transmitter circuit

remote controlled home appliances

Documents

rf remote

rf module

data transmission

immediate data

rf technology

rf controlled switches

rf code

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