final doc 2

ABSTRACT

In Today’s Electronic communication take important role. Today’s Communication

technology the chatting system from one Place to another is easy and fast. The main aim

of this project is to display the notice using PC with RF Communication. The purpose of

the project is to send data from pc and display on LCD by using RF.

In our project we have two sections, one is transmitter section and another one is Receiver

section. The two sections are designed around a microcontroller as a control unit with all

the devices interfaced to it. The main aim of the project is to transmit the data using

wireless communication. At the receiver side, it will display on LCD which works like a

notice board using RF.

BLOCK DIAGRAM:

TRANSMITTER :

MICRO CONTROLLER

Power supply

EncoderRF

TransmitterDRIVER

RECEIVER:

POWER SUPPLY :

DESCRIPTION:

The hardware used in the transmitter section are microcontroller, RF transmitter, encoder,

serial driver, power supply .In the receiver section microcontroller, RF receiver, decoder,

LCD, power supply .The software used for this project are keil, embedded ‘C’, express

PCB, express schematic.

According to this project we can implement notice board using RF.

Step DownTransformer

BridgeRectifier

FilterCircuit

Regulator section

MICRO CONTROLLER

DecoderRFReceiver

Regulated Power Supply

1.INTRODUCTION

1.1 OVERVIEW

Notice Board is primary thing in any institution / organization or public utility places like

bus stations, railway stations and parks. But sticking various notices day-to-day is a

difficult process. A separate person is required to take care of this notices display. This

project deals about an advanced hi-tech wireless notice board

Electronic notice board is a common device that is used to display information. The

information or messages are displayed using dot matrix. The wireless system for dot

matrix display is a method using Radio Frequency as transmission medium. The system

consists of two modules: transmitter and receiver. The transmitter module is used by a

user to place a message through an input module PC. The information then transmitted

using RF technology to the receiver. It then will be decoded and displayed on electronic

notice board

1.2 STATEMENT OF THE PROBLEM

Currently we rely on putting up notices on the notice boards using papers. This is time

consuming since we need time for preparing notices. Also there is wastage of paper. If we

need to renew the notice then we have to take a new hardcopy

Presently almost all electronic notice boards are designed using wired system.

One of the drawbacks of the design is the system is inflexible in term of placement.

The common notice board cannot be placed anywhere because of the messy wire.

1.3 OBJECTIVE OF THE STUDY

The aim of this project is to develop a wireless notice board that will be used at the

faculty in order to display latest information. Wireless electronics notice board is

developed as user friendly notice board with wireless concept that offers the flexibility to

control the notice board within range of few meters. The input of the system is PC. The

PC is connected to the electronic notice board by using RF technology.

1.4 LITERATURE SURVEY

1.4.1 WIRELESS HISTORY:-

The wireless era was started by two European scientists,James Clerk Maxwell and

Heinrich Rudolf Hertz. In 1984, Maxwell presented the Maxwell’s equations by

combining the works of Lorentz, Faraday, Ampere and Gauss. He predicted the

propagation of electromagnet waves in free space at the speed of light. His theory was

accepted 20 years later, after Hertz validated electromagnetic wave (wireless)

propagation. Hertz demonstrated RF generation, propagation and reception in the

laboratory. His work then continues by Guglielmo Marconi after 2 decades. He then

acquires a method for transmitting and receiving information. Marconi started to

commercialize the use of electromagnet wave propagation for wireless telegraphs and

allowed the transfer of information from one continent to another without physical

connection. Since the cellular mobile phone system was introduced in the early 1980’s,

the wireless industry has gone several generations of revolutionary changes. Other

examples for this application are in remote sensing, broadcast, smart automobile and

highways and so on.

1.4.2 NOTICE BOARD HISTORY:-

We are instrumental in providing a wide variety of display notice boards that can be used

to display anything, be it some painting, any article, a notice or any other information.

Offered at competitive prices, these are available in various sizes and shapes and are

extremely durable.

1.4.3 ORGANISATION OF THESIS

3.BLOCK DIAGRAM

TRANSMITTER

RECEIVER

MICRO CONTROLLER

Power supply

PCEncoder

RFTransmitter

MICRO CONTROLLER

DecoderRFReceiver

Regulated Power Supply

DRIVER

Block Diagram Explanation:

Micro controller:

In this project work the micro-controller is plays major role. Micro-controllers

were originally used as components in complicated process-control systems. However,

because of their small size and low price, Micro-controllers are now also being used in

regulators for individual control loops.In several areas Micro-controllers are now

outperforming their analog counterparts and are cheaper as well.

RF Transmitter

In this project ST-TX01-ASK is used as the RF transmitter module. The encoded signal is

given to the RF transmitters data pin. Then the signal is modulated (ASK) by the RF

Transmitter module and transmitted through the antenna. This section is fully described in

the RF communication section.

Encoder

We are using IC HT 640 Encoder which is a 24 pin IC. This encoder circuit will encode

the data send by the microcontroller and then transmits the data serially to the RF

transmitter module. Here we are using ST-TX01 transmitter module for transmitting the

RF module (RECIEVER)

In this section we are using ST-RX04 RF Receiver module. The transmitted signal is

received by this receiver module. The received data is transmitted to the decoder to

decode the data as we encoded the data while transmitting.

DECODER

We are using IC HT648 Decoder which is a 24 pin IC. This Decoder circuit will decode

the data from the receiver and then send the decoded data to the microcontroller.

POWER SUPPLY

A variable regulated power supply is one where you can continuously adjust the output

voltage to our requirements. Varying the output of the power supply is the recommended

way to test a project after having double checked parts placement against circuit drawings

and the parts placement guide. This type of regulation is ideal for having a simple

variable bench power supply. While a dedicated supply is quite handy e.g. 5V or 12V, it's

much handier to have a variable supply on hand, especially for testing. Most digital logic

circuits and processors need a 5 volt power supply. To use these parts we need to build a

regulated 5 volt source. Usually you start with an unregulated power supply ranging from

9 volts to 24 volts DC (A 12 volt power supply is included with the Beginner Kit and the

Microcontroller Beginner Kit.). To make a 5 volt power supply, we use a LM7805

voltage regulator IC.

The LM7805 is simple to use. You simply connect the positive lead of your

unregulated DC power supply (anything from 9VDC to 24VDC) to the Input pin, connect

the negative lead to the Common pin and then when you turn on the power, you get a 5

volt supply from the Output pin.

MAX-232:

Max stands for MAXIM the manufacturer name of the product. It is designed for a special

purpose where to convert the controller voltages to the PC voltages and vise versa for the

data transmission to take place. Therefore it is also called as voltage converter. Here this

interfaced between the PC and the controller.

2.1. Schematic Diagram

TRANSMITTER

RECIEVER:

Schematic explanation:

voltage. Firstly, the required operating voltage for Microcontroller 89C51 is 5V. Hence

the 5V D.C.. This regulated 5V is generated by first stepping down the 230V to 9V power

supply is needed by the same by the step down transformer.

The step downed a.c. voltage is being rectified by the Bridge Rectifier. The diodes used

are 1N4007. The rectified a.c voltage is now filtered using a ‘C’ filter. Now the rectified,

filtered D.C. voltage is fed to the Voltage Regulator. This voltage regulator allows us to

have a Regulated Voltage which is +5V.The rectified; filtered and regulated voltage is

again filtered for ripples using an electrolytic capacitor 100μF. Now the output from this

section is fed to 40th pin of 89c51 microcontroller to supply operating

The microcontroller 89c51 with Pull up resistors at Port0 and crystal oscillator of 11.0592

MHz crystal in conjunction with couple of capacitors of is placed at 18th & 19th pins of

89c51 to make it work (execute) properly.

Transmitter:

RF transmitter is connected to the port P2.0 to P2.3 and TE pin is connected to the port

Receiver :

RF receiver is connected to the port P2.0 to P2.3 and VT pin is connected to the port p3.2

LCD data pins are connected to the port 0 and control pins are connected to the port 2.5 to

3. Hardware Components

Microcontroller

MAX- 232

RF TRANSMITTER

RF RECEIVER

Power supply

3.1.1 MICROCONTROLLER AT89C51

A Micro controller consists of a powerful CPU tightly coupled with memory, various I/O

interfaces such as serial port, parallel port timer or counter, interrupt controller, data

acquisition interfaces-Analog to Digital converter, Digital to Analog converter, integrated

on to a single silicon chip.

If a system is developed with a microprocessor, the designer has to go for external

memory such as RAM, ROM, EPROM and peripherals. But controller is provided all

these facilities on a single chip. Development of a Micro controller reduces PCB size and

cost of design.

One of the major differences between a Microprocessor and a Micro controller is that a

controller often deals with bits not bytes as in the real world application.

Intel has introduced a family of Micro controllers called the MCS-51.

3.1.2 The Major Features :

Compatible with MCS-51 products

4k Bytes of in-system Reprogrammable flash memory

Fully static operation: 0HZ to 24MHZ

Three level programmable clock

128 * 8 –bit timer/counters

Six interrupt sources

Programmable serial channel

Low power idle power-down modes

3.1.3 AT89C51 MICROCONTROLLER ARCHITECTURE

3.1.4 The AT89C51 architecture consists of these specific features:

Eight –bit CPU with registers A (the accumulator) and B

Sixteen-bit program counter (PC) and data pointer (DPTR)

Eight- bit stack pointer (PSW)

Eight-bit stack pointer (Sp)

Internal ROM or EPROM (8751) of 0(8031) to 4K (89C51)

Internal RAM of 128 bytes:

1. Four register banks, each containing eight registers

2. Sixteen bytes, which maybe addressed at the bit level

3. Eighty bytes of general- purpose data memory

Thirty –two input/output pins arranged as four 8-bit ports:p0-p3

Two 16-bit timer/counters: T0 and T1

Full duplex serial data receiver/transmitter: SBUF

Control registers: TCON, TMOD, SCON, PCON, IP, and IE

Two external and three internal interrupts sources.

Oscillator and clock circuits.

Functional block diagram of micro controller

3.1.5 Types of memory:

The 89C51 have three general types of memory. They are on-chip memory,

external Code memory and external Ram. On-Chip memory refers to physically existing

memory on the micro controller itself. External code memory is the code memory that

resides off chip. This is often in the form of an external EPROM. External RAM is the

Ram that resides off chip. This often is in the form of standard static RAM or flash

3.1.6 PIN DIAGRAM OF AT 89C51

Pin Description :

VCC: Supply voltage.

GND: Ground.

Port 0:

Port 0 is an 8-bit open-drain bi-directional I/O port. As an output port, each pin can sink

eight TTL inputs. When one’s are written to port 0 pins, the pins can be used as high

impedance inputs. Port 0 may also be configured to be the multiplexed low order

address/data bus during accesses to external program and data memory. In this mode P0

has internal pull-ups. Port 0 also receives the code bytes during Flash programming, and

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

program verification.

Port 1:

Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 1 output buffers

can sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled high

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

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

1 also receives the low-order address bytes during Flash programming and verification.

Port 2:

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 memories that use 16-bit addresses (MOVX @DPTR). In

this application, it uses strong internal pull-ups when emitting 1s. During accesses to

external data memories 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.

Port 3:

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

Port 3 also serves the functions of various special features of the AT89C51 as listed

below:

Port 3 also receives some control signals for Flash programming and verification

Tab 6.2.1 Port pins and their alternate functions

3.1.7 Oscillator Characteristics:

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

which can be configured for use as an on-chip oscillator, as shown in Figs 6.2.3. Either a

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

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

Figure 6.2.4.There are no requirements on the duty cycle of the external clock signal,

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

minimum and maximum voltage high and low time specifications must be observed.

Fig 6.2.3 Oscillator Connections Fig 6.2.4 External Clock Drive Configuration

3.1.8 Serial Communication:

Computers can transfer data in two ways: parallel and serial. In parallel data

transfers, often 8 or more lines (wire conductors) are used to transfer data to a device that

is only a few feet away. Examples of parallel data transfer are printers and hard disks;

each uses cables with many wire strips. Although in such cases a lot of data can be

transferred in a short amount of time by using many wires in parallel, the distance cannot

be great. To transfer to a device located many meters away, the serial method is used. In

serial communication, the data is sent one bit at a time, in contrast to parallel

communication, in which the data is sent a byte or more at a time. The 8051 has serial

communication capability built into it, thereby making possible fast data transfer using

only a few wires.

Serial data communication uses two methods, asynchronous and synchronous. The

synchronous method transfers a block of data at a time, while the asynchronous method

transfers a single byte at a time.

Start and stop bits

Asynchronous serial data communication is widely used for character-oriented

transmissions, while block-oriented data transfers use the synchronous method. In the

asynchronous method, each character is placed between start and stop bits. This is called

framing. In the data framing for asynchronous communications, the data, such as ASCII

characters, are packed between a start bit and a stop bit. The start bit is always one bit, but

the stop bit can be one or two bits. The start bit is always a 0 (low) and the stop bit (s) is

1 (high).

Data transfer rate

The rate of data transfer in serial data communication is stated in bps (bits per second).

Another widely used terminology for bps is baud rate. However, the baud and bps rates

are not necessarily equal.

RS232 pins

RS232 cable is commonly referred to as the DB-25 connector. In labeling, DB-

25P refers to the plug connector (male) and DB-25S is for the socket connector (female).

Since not all the pins are used in PC cables, IBM introduced the DB-9 Version of the

serial I/O standard, which uses 9 pins only, as shown in table.

8051 connection to RS232

The RS232 standard is not TTL compatible; therefore, it requires a line driver such as the

MAX232 chip to convert RS232 voltage levels to TTL levels, and vice versa. The

interfacing of 8051 with RS232 connectors via the MAX232 chip is the main topic.

The 8051 has two pins that are used specifically for transferring and receiving data

serially. These two pins are called TXD and RXD and a part of the port 3 group (P3.0 and

P3.1). Pin 11 of the 8051 is assigned to TXD and pin 10 is designated as RXD. These

pins are TTL compatible; therefore, they require a line driver to make them RS232

compatible. One such line driver is the MAX232 chip.

MAX232 converts from RS232 voltage levels to TTL voltage levels, and vice versa. One

advantage of the MAX232 chip is that it uses a +5V power source which, is the same as

the source voltage for the 8051. In the other words, with a single +5V power supply we

can power both the 8051 and MAX232, with no need for the power supplies that are

common in many older systems. The MAX232 has two sets of line drivers for

transferring and receiving data. The line drivers used for TXD are called T1 and T2,

while the line drivers for RXD are designated as R1 and R2. In many applications only

one of each is used.

CONNECTING μC to PC using MAX 232

3.2 LCD (Liquid Crystal Display )

Liquid crystal displays (LCD s) have materials which combine the properties of

both liquids and crystals. Rather than having a melting point, they have a temperature

range within which the molecules are almost as mobile as they would be in a liquid, but

are grouped together in an ordered form similar to a crystal.

3.2.1 LCD pin description

The LCD discussed in this section has 14 pins. The function of each pin is given in table.

Pin Symbol I/O Description

1 Vss -- Ground

2 Vcc -- +5V power supply

3 VEE -- Power supply to

control contrast

4 RS I RS=0 to select

command register

RS=1 to select

data register

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

R/W=1 for read

6 E I/O Enable

7 DB0 I/O The 8-bit data bus

The LCDs used exclusively in watches, calculators and measuring instruments are the

simple seven-segment displays, having a limited amount of numeric data. The recent

advances in technology have resulted in better legibility, more information displaying

capability and a wider temperature range. These have resulted in the LCDs being

extensively used in telecommunications and entertainment electronics. The LCDs have

even started replacing the cathode ray tubes (CRTs) used for the display of text and

graphics, and also in small TV applications.

3.2.2 LCD INTERFACING:

Sending commands and data to LCDs with a time delay:

To send any command from table 2 to the LCD, make pin RS=0. For data, make

RS=1.Then place a high to low pulse on the E pin to enable the internal latch of the LCD.

3.3 MAX-232:

The MAX232 from Maxim was the first IC which in one package contains the necessary

drivers (two) and receivers (also two), to adapt the RS-232 signal voltage levels to TTL

logic. It became popular, because it just needs one voltage (+5V) and generates the

necessary RS-232 voltage levels (approx. -10V and +10V) internally. This greatly

simplified the design of circuitry. Circuitry designers no longer need to design and build a

power supply with three voltages (e.g. -12V, +5V, and +12V), but could just provide one

+5V power supply, e.g. with the help of a simple 78x05 voltage converter. The MAX232

has a successor, the MAX232A. The ICs are almost identical, however, the MAX232A is

much more often used (and easier to get) than the original MAX232, and the MAX232A

only needs external capacitors 1/10th the capacity of what the original MAX232 needs.

It should be noted that the MAX 232(A) is just a driver/receiver. It does not generate the

necessary RS-232 sequence of marks and spaces with the right timing, it does not decode

the RS-232 signal, it does not provide a serial/parallel conversion. All it does is to convert

signal voltage levels. The MAX 232(A) has two receivers (converts from RS-232 to TTL

voltage levels) and two drivers (converts from TTL logic to RS-232 voltage levels). This

means only two of the RS-232 signals can be converted in each direction. The old

MC1488/1498 combo provided four drivers and receivers.

MAX232 to RS232 DB9 Connection as a DCE

MAX232 Pin Nbr. MAX232 Pin Name Signal Voltage DB9 Pin

7 T2out CTS RS-232 7

8 R2in RTS RS-232 8

9 R2out RTS TTL n/a

10 T2in CTS TTL n/a

11 T1in TX TTL n/a

12 R1out RX TTL n/a

13 R1in TX RS-232 3

14 T1out RX RS-232 2

15 GND GND 0 5

3.3.1 Features

Meet or Exceed TIA/EIA-232-F and ITU

Recommendation V.28

Operate With Single 5-V Power Supply

Operate Up to 120 kbit/s

Two Drivers and Two Receivers

30-V Input Levels

Low Supply Current . . . 8 mA Typical

Designed to be Interchangeable With

Maxim MAX232

ESD Protection Exceeds JESD 22

2000-V Human-Body Model (A114-A)

3.3.2 Description/ordering information

The MAX232 is a dual driver/receiver that includes a capacitive voltage generator to

supply EIA-232 voltage levels from a single 5-V supply. Each receiver converts EIA-232

inputs to 5-V TTL/CMOS levels. These receivers have a typical threshold of 1.3 V and a

typical hysteresis of 0.5 V, and can accept 30-V inputs. Each driver converts

TTL/CMOS input levels into EIA-232 levels. The driver, receiver, and voltage-generator

functions are available as cells in the Texas Instruments Lin ASIClibrary.

RF transmitter:

RF transmitters are electronic devices that create continuously varying electric current,

encode sine waves, and broadcast radio waves. RF transmitters use oscillators to create

sine waves, the simplest and smoothest form of continuously varying waves, which

contain information such as audio and video. Modulators encode these sign wives and

antennas broadcast them as radio signals. There are several ways to encode or modulate

this information, including amplitude modulation (AM) and frequency modulation.

3.4 ASK Transmitter Module (ST-TX01-ASK (Saw Type) :

3.4.1 General Description:

The ST-TX01-ASK is an ASK Hybrid transmitter module. ST-TX01-ASK is

designed by the Saw Resonator, with an effective low cost, small size, and simple-to-use

for designing.

Frequency Range: 315 / 433.92 MHZ.

Supply Voltage: 3~12V.

Output Power: 4~16dBm.

Circuit Shape: Saw.

315/434 MHz ASK TRANSMITTER

Applications

*Wireless security systems

*Car Alarm systems

*Remote controls.

*Sensor reporting

*Automation systems

Here in this project the RF transmitter module is not directly connected to

microcontroller. An Encoder is connected between the RF module and the controller, in

order to encode the data for efficient transmission of the data.

RF receiver module:

RF receivers are electronic devices that separate radio signals from one another and

convert specific signals into audio, video, or data formats. RF receivers use an antenna to

receive transmitted radio signals and a tuner to separate a specific signal from all of the

other signals that the antenna receives. Detectors or demodulators then extract

information that was encoded before transmission. There are several ways to decode or

demodulate this information, including amplitude modulation (AM) and frequency

modulation (FM). Radio techniques limit localized interference and noise. With direct

sequence spread spectrum, signals are spread over a large band by multiplexing the signal

with a code or signature that modulates each bit. With frequency hopping spread

spectrum, signals move through a narrow set of channels in a sequential, cyclical, and

predetermined pattern.

3.4.2 Pin Description:

The RX04 is a low power ASKS receiver IC which is fully compatible with the

MitelKESRX01 IC and is suitable for use in a variety of low power radio applications

including remote keyless entry. The RX04 is based on a single-conversion, super-

heterodyne receiver architecture and incorporates an entire phase-locked loop (PLL) for

precise local oscillator generation.

3.5 Encoder HT640:

The 3 to the power 18 encoders are a series of CMOS LSIs for remote control

system applications. They are capable of encoding 18 bits of information which consists

of N address bits and 18-N data bits. Each address/data input is externally ternary

programmable if bonded out. It is otherwise set floating internally. Various packages of

the 3-18 encoders offer flexible combinations of programmable address/data to meet

various application needs. The programmable address/data is 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 type or a DATA trigger type further enhances

the application flexibility of the 3-18 series of encoders.

3.5.2 Pin description

Fig: Pin functions.

3.6 Decoder HT648L

The radio frequency spectrum is filled with noise and other signals, especially

those frequencies where unlicensed transmitter operation under FCC part 15 rules is

allowed. When using a wireless remote control system it is desirable to have a way of

filtering out or ignoring those unwanted signals to prevent false data from being received.

A simple way to accomplish this is to use an encoder IC at the transmitter and a decoder

IC at the receiver. The encoder generates serial codes that are automatically sent three

times and must be received at least twice before data is accepted as valid by the decoder

circuit.

3.6.1 General description:

The “3 to the power 18” decoders are a series of CMOS LSIs for remote control system

applications. They are paired with the “3 to the power18” series of encoders. For proper

operation a pair of encoder/decoder pair with the same number of address and data format

should be selected (refer to the encoder/decoder cross reference tables).

The “3 to the power 18” series of decoders receives serial address and data from that

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

medium. It then compares the serial input data twice continuously with its local address.

If no errors or unmatched codes are encountered, the input data codes are decoded and

then transferred to the output pins. The VT pin also goes high to indicate a valid

transmission.

The “3 to the power 18” decoders are capable of decoding 18 bits of information that

consists of N bits of address and 18–N bits of data. To meet various applications they are

arranged to provide a number of data pins whose range is from 0 to 8 and an address pin

whose range is from 8 to 18. In the mother board the decoder used is HT648L.

3.6.2 Pin description:

HT648L device is available in SOP/SDIP packages with 24 pins. Here we are using the

SDIP package whose pin diagram is as shown in the figure.

Fig 10: Pin description.

Functional description:

Pin Name I/0 Internal Connection Description

A0 - A9

I TRANSMISSION GATE

Input pins for address A0 – A9setting.

They can be externally set to VDD,

VSS, or left open.

D10 – D17 O CMOS OUT Output data pins.

DIN I CMOS IN Serial data input pin

VT O CMOS OUT Valid transmission, active high

OSC1 I OSCILLATOR Oscillator input pin

OSC2 O OSCILLATOR Oscillator output pin

VSS I __ Negative power supply(GND)

VDD I __ Positive power supply

3.7 Power supply:

The power supplies are designed to convert high voltage AC mains electricity to a

suitable low voltage supply for electronic circuits and other devices. A power supply can

by broken down into a series of blocks, each of which performs a particular function. A

d.c power supply which maintains the output voltage constant irrespective of a.c mains

fluctuations or load variations is known as “Regulated D.C Power Supply”

For example a 5V regulated power supply system as shown below:

Transformer:

A transformer is an electrical device which is used to convert electrical power from one

Electrical circuit to another without change in frequency.

Transformers convert AC electricity from one voltage to another with little loss of

power. Transformers work only with AC and this is one of the reasons why mains

electricity is AC. Step-up transformers increase in output voltage, step-down

transformers decrease in output voltage. Most power supplies use a step-down

transformer to reduce the dangerously high mains voltage to a safer low voltage. The

input coil is called the primary and the output coil is called the secondary. There is no

electrical connection between the two coils; instead they are linked by an alternating

magnetic field created in the soft-iron core of the transformer. The two lines in the middle

of the circuit symbol represent the core. Transformers waste very little power so the

power out is (almost) equal to the power in. Note that as voltage is stepped down current

is stepped up. The ratio of the number of turns on each coil, called the turn’s ratio,

determines the ratio of the voltages. A step-down transformer has a large number of turns

on its primary (input) coil which is connected to the high voltage mains supply, and a

small number of turns on its secondary (output) coil to give a low output voltage.

An Electrical Transformer

Turns ratio = Vp/ VS = Np/NS

Power Out= Power In

VS X IS=VP X IP

Vp = primary (input) voltage

Np = number of turns on primary coil

Ip = primary (input) current

RECTIFIER:

A circuit which is used to convert AC to DC is known as RECTIFIER. The

process of conversion A to DC is called “rectification”

Here in this project we use bridge rectifier.

Bridge Rectifier:

A bridge rectifier makes use of four diodes in a bridge arrangement to achieve

full-wave rectification. This is a widely used configuration, both with individual diodes

wired as shown and with single component bridges where the diode bridge is wired

internally.

A bridge rectifier makes use of four diodes in a bridge arrangement as shown in

fig(a) to achieve full-wave rectification. This is a widely used configuration, both with

individual diodes wired as shown and with single component bridges where the diode

bridge is wired internally.

Fig(A)

Operation:

During positive half cycle of secondary, the diodes D2 and D3 are in forward biased

while D1 and D4 are in reverse biased as shown in the fig(b). The current flow direction

is shown in the fig (b) with dotted arrows.

Fig(B)

During negative half cycle of secondary voltage, the diodes D1 and D4 are in forward

biased while D2 and D3 are in reverse biased as shown in the fig(c). The current flow

direction is shown in the fig (c) with dotted arrows.

Fig(C)

Filter:

A Filter is a device which removes the AC component of rectifier output but allows the

AC component to reach the load

Capacitor Filter:

Ripples can be removed by one of the following methods of filtering. A capacitor, in

parallel to the load, provides an easier by –pass for the ripples voltage though it due to

low impedance. At ripple frequency and leave the d.c.to appears the load

Filtering is performed by a large value electrolytic capacitor connected across the

DC supply to act as a reservoir, supplying current to the output when the varying DC

voltage from the rectifier is falling. The capacitor charges quickly near the peak of the

varying DC, and then discharges as it supplies current o the output. Filtering significantly

increases the average DC voltage to almost the peak value (1.4 × RMS value).

To calculate the value of capacitor(C),

C = ¼*√3*f*r*R l

Where,

f = supply frequency,

r = ripple factor,

R l = load resistance.

Regulator:

Voltage regulator ICs is available with fixed (typically 5, 12 and 15V) or variable output

voltages. The maximum current they can pass also rates them. Negative voltage

regulators are available, mainly for use in dual supplies. Most regulators include some

automatic protection from excessive current ('overload protection') and overheating

('thermal protection'). Many of the fixed voltage regulator IC have 3 leads and look like

power transistors, such as the 7805 +5V 1A regulator shown on the right. The LM7805 is

simple to use. You simply connect the positive lead of your unregulated DC power supply

(anything from 9VDC to 24VDC) to the Input pin, connect the negative lead to the

Common pin and then when you turn on the power, you get a 5 volt supply from the

output pin.

Fig 6.1.6 A Three Terminal Voltage Regulator

The Bay Linear LM78XX is integrated linear positive regulator with three

terminals. The LM78XX offer several fixed output voltages making them useful in wide

range of applications. When used as a zener diode/resistor combination replacement, the

LM78XX usually results in an effective output impedance improvement of two orders of

magnitude, lower quiescent current. The LM78XX is available in the TO-252, TO-220 &

TO-263packages,

Features:

• Output Current of 1.5A

• Output Voltage Tolerance of 5%

• Internal thermal overload protection

• Internal Short-Circuit Limited

• No External Component

• Output Voltage 5.0V, 6V, 8V, 9V, 10V,12V, 15V, 18V, 24V

• Offer in plastic TO-252, TO-220 & TO-263

• Direct Replacement for LM78XX

Circuit description:

In this project we required operating voltage for Microcontroller 89C51 is 5V. Hence the 5V D.C.

power supply is needed for the IC’s. This regulated 5V is generated by stepping down the voltage

from 230V to 18V now the step downed a.c voltage is being rectified by the Bridge Rectifier using

1N4007 diodes. The rectified a.c voltage is now filtered using a ‘C’ filter. Now the rectified,

filtered D.C. voltage is fed to the Voltage Regulator. This voltage regulator provides/allows us to

have a Regulated constant Voltage which is of +5V. The rectified; filtered and regulated voltage is

again filtered for ripples using an electrolytic capacitor 100μF. Now the output from this section is

fed to 40th pin of 89C51 microcontroller to supply operating voltage. The microcontroller 89C51

with Pull up resistors at Port0 and crystal oscillator of 11.0592 MHz crystal in conjunction with

couple of 30-33pf capacitors is placed at 18th & 19th pins of 89C51 to make it work (execute)

properly. In our project we have two sections, one is transmitter section and another one is

Receiver section. The two sections are designed around a microcontroller as a control unit with all

the devices interfaced to it. The main aim of the project is to transmit the data using wireless

communication. At the receiver side, it will display on LCD which works like a notice board.

4. Proposed Algorithm

6.Result

1. Click on the Keil u Vision Icon on Desktop

2. The following fig will appear

3. Click on the Project menu from the title bar

4. Then Click on New Project

5. Save the Project by typing suitable project name with no extension in u r own

folder sited in either C:\ or D:\

6. Then Click on save button above.

7. Select the component for u r project i.e., Atmel……

8. Click on the + Symbol beside of Atmel

9. Select AT89C51 as shown below

10. Then Click on “OK”

11. The Following fig will appear

12. Then Click either YES or NO………mostly “NO”

13. Now your project is ready to USE

14. Now double click on the Target1, you would get another option “Source group

1” as shown in next page.

15. Click on the file option from menu bar and select “new”

16. The next screen will be as shown in next page, and just maximize it by double

clicking on its blue boarder.

17. Now start writing program in either in “C” or “ASM”

18. For a program written in Assembly, then save it with extension “. asm” and

for “C” based program save it with extension “ .C”

19. Now right click on Source group 1 and click on “Add files to Group Source”

20. Now you will get another window, on which by default “C” files will appear.

21. Now select as per your file extension given while saving the file

22. Click only one time on option “ADD”

23. Now Press function key F7 to compile. Any error will appear if so happen.

24. If the file contains no error, then press Control+F5 simultaneously.

25. The new window is as follows

26. Then Click “OK”

27. Now Click on the Peripherals from menu bar, and check your required port as

shown in fig below

28. Drag the port a side and click in the program file.

29. Now keep Pressing function key “F11” slowly and observe.

30. You are running your program successfully

Appendix

serial#include <REGX51.H>

#include <serial.h>

/*********** PIN CONNECTIONS ************/

sfr rfdata =0x90;

sbit te=P3^2;

/************* VARIABLE DECLARATIONS ************/

unsigned char a[30],i,k,t;

bit f1;

/*************** SERIAL ISR **********/

void serialint (void) interrupt 4

if (RI)

t=SBUF;

a[i++]=t;

if(a[i-1]==0x0d){f1=1;a[i]='\0';}

EA=0;serial_tx(a[i-1]);EA=1;

RI=0;delay1(10);

/******************* RF TRANS fun***************/

void trans_tx(unsigned char t)

rfdata=t;

serial_tx(t);

delay1(50);

void trans(unsigned char *x)

while(*x!='\0')

trans_tx(*x++);

delay1(50);

/*************** MAIN FUNCTION ****************/

void main()

/************ SERIAL INITILISATIONS *******/

sconfig();

serial("WELCOME TO THE PROJECT:");

serial_tx(0x0d);

_tx(0x0a);

serial("ENTER DATA:");

ES=1;f1=0;i=0;

while(1)

if(f1==1)

delay1(50);

serial_tx(0x0d);

serial_tx(0x0a);

serial("ENTER DATA:");

EA=1;f1=0;i=0;

} serial_tx(0x0a);

serial("SENDING...."); trans(a);

serial("SENDED....");

5.Introduction to Software

Embedded C*Keil software for c programming

ABOUT KEIL SOFTWARE:

It is possible to create the source files in a text editor such as Notepad, run the

Compiler on each C source file, specifying a list of controls, run the Assembler on each

Assembler source file, specifying another list of controls, run either the Library Manager

or Linker (again specifying a list of controls) and finally running the Object-HEX

Converter to convert the Linker output file to an Intel Hex File. Once that has been

completed the Hex File can be downloaded to the target hardware and debugged.

Alternatively KEIL can be used to create source files; automatically compile, link and

covert using options set with an easy to use user interface and finally simulate or perform

debugging on the hardware with access to C variables and memory. Unless you have to

use the tolls on the command line, the choice is clear. KEIL Greatly simplifies the process

of creating and testing an embedded application.

Simulator/Debugger:

The simulator/ debugger in KEIL can perform a very detailed simulation of a micro

controller along with external signals. It is possible to view the precise execution time of

a single assembly instruction, or a single line of C code, all the way up to the entire

application, simply by entering the crystal frequency. A window can be opened for each

peripheral on the device, showing the state of the peripheral. This enables quick trouble

shooting of mis-configured peripherals. Breakpoints may be set on either assembly

instructions or lines of C code, and execution may be stepped through one instruction or

C line at a time. The contents of all the memory areas may be viewed along with ability to

find specific variables. In addition the registers may be viewed allowing a detailed view

of what the microcontroller is doing at any point in time.

7.Conclusion and Future Scope

The project “NOTICE BOARD WITH USING RF” has been successfully designed and

tested. Integrating features of all the hardware components used have developed it.

Presence of every module has been reasoned out and placed carefully thus contributing to

the best working of the unit. Secondly, using highly advanced IC’s and with the help of

growing technology the project has been successfully implemented.

BIBLIOGRAPHY

The 8051 Micro controller and Embedded Systems

-Muhammad Ali Mazidi

Janice Gillispie Mazidi

The 8051 Micro controller Architecture, Programming & Applications

-Kenneth J. Ayala

Fundamentals Of Micro processors and Micro computers

-B. Ram

Micro processor Architecture, Programming & Applications

- Ramesh S. Gaonkar

Electronic Components

-D.V. Prasad

Wireless Communications

- Theodore S. Rappaport

Mobile Tele Communications

- William C.Y. Lee

References on the Web:

www.national.com

www.atmel.com

www.microsoftsearch.com

www.geocities.com

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