Chapter 1

INTRODUCTION

1.1 RF Communication Systems:

Communication Systems are playing a vital role in our personal and professional life. It is a key area of development from last century. Earlier we use wired communication mediums.Those are very costly and bulky.But with the development of last technologies a new medium of communication has been built.

It’s possible to transmit data through the radio frequency over a short distance. It represents the concept of Radio frequency communication. We are using a keyboard to enter the text, which is processed by the microcontroller and displayed on the LCD then RF modules are used to transmit this data to receiver end.

Unlike Bluetooth or wireless USB devices, R.F. devices have the ability to form a mesh network between nodes. Meshing is a type of daisy chaining from one device to another. This technique allows the short range of an individual node to be expanded and multiplied, covering a much larger area.RF is the most leading communication medium in today’s life.

At the transmitter, the data is first converted into coded signals.Then it is converted into radio frequency signals by RF module.At the receiver end RF module receives the encoded data.Then decodes the received data.In this way,it generates the actual form of information and display it on the notice board.

Fig.1.1 RF Communication Systems

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1.2 Project Overview:

We have used RF frequency in this project to design a wireless RF notice board. In this project data is transferred one end to another end through RF. Data will be transmitted by 433 MHz RF transmitter. At the receiving side these codes will be received by 433 MHz RF receiver.

We use AT89S52 microcontroller. This controller is basically a 40 pin ic. ROM of 89s52 is 8k and ram is 256 byte. We are using 16*2 lcd in this project. Lcd is connected to port 0 which will display the data. We are using a keyboard to enter the text, which is processed by the microcontroller and displayed on the LCD then RF modules are used to transmit this data to receiver end.

At the receiver end RF module receives the encoded data and generates the actual form and display it on the notice board.

This projects used two power supplies +5v DC and +9VDC. 5 volt dc power supply is a regulated power supply. For the regulated power supply we use IC 7805 as a regulator to provide a fix 5 volt power supply. For the +9V we used the 9v battery.

Hardware Breakpoint of ProjectRF transmitter

• RF module

• Microcontroller circuit

• Keyboard

• Lcd16*2

RF receiver

• RF module

• Microcontroller circuit

• LCD

1.3 Block Diagrams:

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Fig.1.2 Block Diagram of RF Transmitter

Fig.1.3 Block Diagram of RF receiver

1.4 Applications:-

• It can be used as very short range intercom or one way communication3

• College Notice boards

• Multi story malls

• Food junctions

• Waiting Rooms

• Company Reception Areas

• Cinemas

• Factory Production Areas

• Hospitals

• Public Transport Timetables

• Shop window advertising

• In shop offers or promotions

• Travel Agents

• Property Agents

• Exhibition Centres

• Art Galleries

• Car Show Rooms

Chapter 2

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LITERATURE REVIEW

2.1 Project Working

Power supply is the essential part of any device or project. We are using microcontroller and LCD. These components needs +5V DC supply. So we need a power supply circuit of +5V DC. Power supply circuit includes step down transformer, rectifier circuit, filter circuit and regulator circuit. An indicating component is also attached with the power supply to indicate the power ON condition of power supply unit.

The wireless Electronic Notice Board consists of two modules;Transmitter and Receiver module.There are five parts in transmitter module and four parts in receiver module.In transmitter module,there are Keyboard,Liquid crystal display(LCD),Microcontroller,encoder and transmitter.In receiver module,there are receiver,decoder,Microcontroller and Liquid Crystal Display(LCD).This project is based on AT89S8252 microcontroller.Assembly language is used to program the microcontroller. . In this paper we have proposed a system by which only authorized people can access the notice board using a graphical user interface. We can also make the system compatible with more than one wireless technology.

When microcontroller is powered up then due to the reset circuit microcontroller goes reset and go to first location of ROM. We have written the program from the very first location of ROM. After the microcontroller goes reset it start executing instruction from 00h to the end of program. All the instructions are executed sequentially. Crystal circuit is providing clock frequency to the microcontroller. After the initialization of microcontroller first step of microcontroller is to initialize the LCD and display the welcome message. After this microcontroller reads the Keyboard and display it on the LCD and then after it waits for the enter key. After this “enter key” microcontroller asks for the password if the password is correct then it sends the digital value to the RF module at the 9600 bps (approximate). RF module, which is designed to work at 10kbps (maximum) transmit this value at the receiver end.

At the receiver end RF modules receives the data and send it to the microcontroller, then microcontroller read the data from SBUF and display the digital value on the LCD.

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2.2 Circuit Diagrams:-

Fig.2.1 Circuit Diagram of Power Supply

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Fig.2.2 Circuit Diagram of Transmitter

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Fig.2.3 Circuit Diagram of Receiver

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2.3 Material Used:-

• Microcontroller

• Transformer (12V)

• Diodes (IN4007)

• Capacitor (470uF,1000uf,22pf)

• Voltage Regulator (7805 & 7812)

• Resistors

• LED

• RF module

• LCD

• Keyboard

• Transistors

• IC bases

• Ribbon wire

• Jumper wire

• Soldering Iron

• Soldering Wire

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• Multimeter

• PCB

• Cutter

• Screw & Nuts

Chapter 3

PROJECT DESCRIPTION

3.1 Components’ Description

3.1.1 Transformer:-Transformer works on the principle of mutual inductance. We know that if two coils or windings are placed on the core of iron, and if we pass alternating current in one winding, back emf or induced voltage is produced in the second winding. We know that alternating current always changes with the time. So if we apply AC voltage across one winding, a voltage will be induced in the other winding. Transformer works on this same principle. It is made of two windings wound around the same core of iron. The winding to which AC voltage is applied is called primary winding. The other winding is called as secondary winding. Transformers are of two types Step Up transformer and Step Down transformer.

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Fig.3.1 Transformer Schematic Diagram

Step Up transformer: -These transformers are used to increase the voltage level at the output means Voltage at secondary winding is more than the primary winding. In this transformer secondary winding has more number of turns than primary winding. These types of transformers are generally used in power station.

Step Down transformer: - These transformers are used to decrease the voltage level at the output winding means voltage of secondary winding is less than the primary winding. In this transformer secondary winding has less number of turns than primary winding. These types of transformers have major applications in electronics industry. Further these are divided into two categories:

I. Simple Transformer

II. Central tapped transformer

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Fig.3.2 Real life Transformer

I. Simple Transformer: - It’s a four wire transformer. These types of transformer have 2 wires on primary winding and 2 wires on secondary output. Symbol of this transformer is shown below. Voltage rating of these transformer expressed as 6V,12V, 24V etc.

Fig 3.3 Simple Transformer

II. Central Tapped transformer: - It’s a 5 Wire transformer. This type of transformer has 2 wires on primary winding and 3 wires on secondary. Middle one is known as Common. Voltage rating of these transformer expressed as 6-0-6 V,12-0-12 V, 24-0-24 V etc.

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Fig.3.4 Central Tapped transformer

Specification of Transformer:-While purchasing a transformer generally two considerations have to be kept in mind, first one is voltage rating and second is current rating. Voltage rating depends upon the circuit’s operating voltage its generally 5 or 12 Volt so 6 or 12 Volt transformers are generally used. Current rating of transformer depends upon the load of circuit. If our load current is more than the transformer current then due to loading effects transformer can burn out. So to protect our transformer, current rating of transformer should be more than the load current. All transformer comes with different current rating e.g. 6 V transformer is available in 500m A, 750mA, 1A, 2A so on. One thing should be kept in mind as the ampear increases cost of transformer also increases. We have to choose best one according to our circuit requirements.

3.1.2 Resistors:-The flow of charge (or current) through any material, encounters an opposing force similar in many respect to mechanical friction. This opposing force is called resistance of the material. It is measured in ohms. In some electric circuits resistance is deliberately introduced in the form of the resistor.

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Resistors are of following types:

1. Wire wound resistors.2. Carbon resistors.3. Metal film resistors.

1.Wire Wound Resistors:

Wire wound resistors are made from a long (usually Ni-Chromium) wound on a ceramic core. Longer the length of the wire, higher is the resistance. So depending on the value of resistor required in a circuit, the wire is cut and wound on a ceramic core. This entire assembly is coated with a ceramic metal. Such resistors are generally available in power of 2 watts to several hundred watts and resistance values from 1ohm to 100k ohms. Thus wire wound resistors are used for high currents.

2.Carbon Resistors:

Carbon resistors are divided into three types:

a) Carbon composition resistors are made by mixing carbon grains with binding material (glue) and moduled in the form of rods. Wire leads are inserted at the two ends. After this an insulating material seals the resistor. Resistors are available in power ratings of 1/10, 1/8, 1/4 , 1/2 , 1.2 watts and values from 1 ohm to 20 ohms.

b) Carbon film resistors are made by deposition carbon film on a ceramic rod. They are cheaper than carbon composition resistors.

c) Cement film resistors are made of thin carbon coating fired onto a solid ceramic substrate. The main purpose is to have more precise resistance values and greater stability with heat. They are made in a small square with leads.

Fig.3.5 Carbon Resistors 1

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Fig.3.6 Carbon Resistors 2

3.Metal Film Resistors:

They are also called thin film resistors. They are made of a thin metal coating deposited on a cylindrical insulating support. The high resistance values are not precise in value; however, such resistors are free of inductance effect that is common in wire wound resistors at high frequency.

Variable Resistors:

Potentiometer is a resistor where values can be set depending on the requirement. Potentiometer is widely used in electronics systems. Examples are volume control, tons control, brightness and contrast control of radio or T.V. sets.

Fig.3.7 Variable Resistor

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Resistor Color Code

Color 1st band 2nd band 3rd band (multiplier) 4th band (tolerance) Temp. Coefficient

Black 0 0 ×100

Brown 1 1 ×101 ±1% (F) 100 ppm

Red 2 2 ×102 ±2% (G) 50 ppm

Orange 3 3 ×103 15 ppm

Yellow 4 4 ×104 25 ppm

Green 5 5 ×105 ±0.5% (D)

Blue 6 6 ×106 ±0.25% (C)

Violet 7 7 ×107 ±0.1% (B)

Gray 8 8 ×108 ±0.05% (A)

White 9 9 ×109

Gold ×10−1 ±5% (J)

Silver ×10−2 ±10% (K)

None ±20% (M)

Table3.1:Resistor color code

Example: 1k or 1000 ohms

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Band1

Band 2

Band 3

Band 4

Fig.3.8 1K Resistor

3.1.3 Capacitors

A capacitor can store charge, and its capacity to store charge is called capacitance. Capacitors consist of two conducting plates, separated by an insulating material (known as dielectric). The two plates are joined with two leads. The dielectric could be air, mica, paper, ceramic, polyester, polystyrene, etc. This dielectric gives name to the capacitor. Like paper capacitor, mica capacitor etc.

Types of Capacitors:- Capacitors are of two Types

I. Fixed

II. Variable capacitor.

Fixed types of capacitor are further of two types:-

I. Polar Capacitor:- Those capacitor have polarity are known as polar capacitor. Electrolytic capacitor are the example of polar capacitors.

Fig.3.9 Polar Capacitor

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II. Non Polar Capacitor:- Those capacitor have no polarity are known as NON- polar capacitor. Ceramic capacitor are the example of non polar capacitors

Fig.3.10 Non Polar Capacitor

Electrolytic Capacitor: Electrolytic capacitors have an electrolyte as a dielectric. When such an electrolyte is charged, chemical changes takes place in the electrolyte. If its one plate is charged positively, same plate must be charged positively in future. We call such capacitors as polarized. Normally we see electrolytic capacitor as polarized capacitors and the leads are marked with positive or negative on the can. Non-electrolyte capacitors have dielectric material such as paper, mica or ceramic. Therefore, depending upon the dielectric, these capacitors are classified.

Fig.3.11 Electrolytic Capacitor

Ceramic Capacitor: Such capacitors have disc or hollow tabular shaped dielectric made of ceramic material such as titanium dioxide and barium titanate. Thin coating of silver compounds is deposited on both sides of dielectric disc, which acts as capacitor plates. Leads are attached to each sides of the dielectric disc and whole unit is encapsulated in a moisture proof coating. Disc type capacitors have very high value up to 0.001uf. Their working voltages range from 3V to 60000V. These capacitors have very low leakage current. Breakdown voltage is very high.

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Fig.3.12 Ceramic Capacitors

3.1.4 Diode:-

Diodes are semiconductor devices which might be described as passing current in one direction only. Diodes have two terminal, an anode and a cathode. The cathode is always identified by a dot, ring or some other mark. Diode is a unidirectional device. In this current flows in only one direction.

Fig.3.13 Practical Diode Indication

Diodes can be used as voltage regulators, tuning devices in rf tuned circuits, frequency multiplying devices in rf circuits, mixing devices in rf circuits, switching applications or can be used to make logic decisions in digital circuits. There are also diodes which emit "light", of course these are known as light-emitting-diodes or LED's.

A rectifying diode of the 1N4001-07 ( 1A) type or even one of the high power, high current stud mounting types. You will notice the straight bar end has the letter "k", this denotes the "cathode"

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while the "a" denotes anode. Current can only flow from anode to cathode and not in the reverse direction, hence the "arrow" appearance. This is one very important property of diodes.

The principal early application of diodes was in rectifying 50 / 60 Hz AC mains to raw DC which was later smoothed by choke transformers and / or capacitors. This procedure is still carried out today and a number of rectifying schemes for diodes have evolved, half wave, full wave and bridge, full wave and bridge rectifiers.

Fig.3.14 Full,Half and Bridge Rectifiers

As examples in these applications the half wave rectifier passes only the positive half of successive cycles to the output filter through D1. During the negative part of the cycle D1 does not conduct and no current flows to the load. In the full wave application it essentially is two half wave rectifiers combined and because the transformer secondary is centre tapped, D1 conducts on the positive half of the cycle while D2 conducts on the negative part of the cycle. Both add together. This is more efficient. The full wave bridge rectifier operates essentially the same as the full wave rectifier but does not require a cetre tapped transformer. Further discussion may be seen on the topic power supplies.

1N400X series Diode:-

Features

• Diffused Junction

• High Current Capability and Low Forward Voltage Drop

• Low Reverse Leakage Current

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• Lead Free Finish

Fig.3.15 1N400X Series Diode

3.1.5 Transistor:-

The schematic representation of a transistor is shown. Note the arrow pointing down towards the emitter. This signifies it's an NPN transistor A transistor is basically a current amplifier. Say we let 1mA flow into the base. We may get 100mA flowing into the collector. Note: The currents flowing into the base and collector exit through the emitter (sum off all currents entering or leaving a node must equal zero). The gain of the transistor will be listed in the datasheet as either βDC or Hfe. The gain won't be identical even in transistors with the same part number. The gain also varies with the collector current and temperature.

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Fig.3.16 Transistor Symbols

Fig.3.17 npn Transistor

Fig.3.18 pnp Transistor

3.1.6 LED:-

LED means light emitting diode. Its function is similar to the diode. But these are not made up from silicon or germanium. These are generally used as a indicating device. There are variety of LEDs are available in market depending upon their size and colour.

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Fig 3.19 Various LEDs

Polarity of LED:- LED have polarity. We can judge its polarity by watching flags in its structure. Bigger flag is known as cathode and smaller flag is known as anode as shown below.

Fig.3.20 Polarity of LED

3.1.7 Voltage Regulator:-

The LM78XX 3-terminal positive voltage regulators employ internal current-limiting, thermal shutdown and safe-area compensation, making them essentially indestructible. Heat sinking is provided; they can deliver over 1.0A output current. They are intended as fixed voltage regulators in a wide range of applications including local (on-card) regulation for elimination of noise and

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distribution problems associated with single-point regulation. In addition to use as fixed voltage regulators.

Fig.3.21 Voltage Regulator

Features:

■ Output current up to 1 A

■ Output voltages of 5; 6; 8; 9; 12; 15; 18; 24 V

■ Thermal overload protection

■ Short circuit protection

3.1.8 Crystal: -

It’s a 2 terminal component. This component has no polarity. Its basic function to generate a Square Wave of some fixes frequency. Its value is measure in MHz.

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Fig.3.22 Crystal

3.1.9 Liquid Crystal Display:-

A liquid crystal display (LCD) is a thin, flat electronic visual display that uses the light modulating properties of liquid crystals (LCs). LCs does not emit light directly. LCDs therefore need a light source and are classified as "passive" displays. Some types can use ambient light such as sunlight or room lighting. There are many types of LCDs that are designed for both special and general uses.

LCDs are more energy efficient, and offer safer disposal, than CRTs. Its low electrical power consumption enables it to be used in battery-powered electronic equipment.

The LCD Module can easily be used with an 8051 microcontroller such as the 162A. The LCD Module comes with a 16 pin connector. This can be plugged into connector 16 pin.

Most common LCDs connected to the 8051 are 16x2 and 20x2 displays. This means 16 characters per line by 2 lines and 20 characters per line by 2 lines, respectively.

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Fig.3.23 LCD Character 2 x 16 Module

Character LCDs use a standard 14-pin interface and those with backlights have 16 pins.

Pin configuration

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The user may select whether the LCD is to operate with a 4-bit data bus or an 8-bit data bus. If a 4-bit data bus is used, the LCD The 44780 standard requires 3 control lines as well as either 4 or 8

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PIN Name Function

1 VSS Ground voltage

2 VCC +5V

3 VEE Contrast voltage

4 RSRegister Select0 = Instruction Register1 = Data Register

5 R/WRead/ Write, to choose write or read mode0 = write mode1 = read mode

6 EEnable0 = start to latch data to LCD character1= disable

7 DB0 LSB

8 DB1 -

9 DB2 -

10 DB3 -

11 DB4 -

12 DB5 -

13 DB6 -

14 DB7 MSB

15 BPL Back Plane Light

16 GND Ground voltage

I/O lines for the data bus. The user may select whether the LCD is to operate with a 4-bit data bus or an 8-bit data bus. If a 4-bit data bus is used, the LCD will require a total of 7 data lines (3 control lines plus the 4 lines for the data bus). If an 8-bit data bus is used, the LCD will require a total of 11 data lines (3 control lines plus the 8 lines for the data bus). The three control lines are referred to as EN, RS, and RW.

Enable(E):-The EN line is called "Enable." This control line is used to tell the LCD that you are sending it data. To send data to the LCD, your program should first set this line high (1) and then set the other two control lines and/or put data on the data bus. When the other lines are completely ready, bring EN low (0) again. The 1-0 transition tells the 44780 to take the data currently found on the other control lines and on the data bus and to treat it as a command.

Register Select(RS):-The RS line is the "Register Select" line. When RS is low (0), the data is to be treated as a command or special instruction (such as clear screen, position cursor, etc.). When RS is high (1), the data being sent is text data which should be displayed on the screen. For example, to display the letter "T" on the screen you would set RS high.

Read Write(R/W):-The RW line is the "Read/Write" control line. When RW is low (0), the information on the data bus is being written to the LCD. When RW is high (1), the program is effectively querying (or reading) the LCD. Only one instruction ("Get LCD status") is a read command. All others are write commands--so RW will almost always be low.

Finally, the data bus consists of 4 or 8 lines (depending on the mode of operation selected by the user). In the case of an 8-bit data bus, the lines are referred to as DB0, DB1, DB2, DB3, DB4, DB5, DB6, and DB7.

3.2 Power supply

Power supply is the essential part of any device or project. We are using microcontroller and LED. These components needs +5V DC supply. So we need a power supply circuit of +5V DC. Power supply circuit includes step down transformer, rectifier circuit, filter circuit and regulator circuit. An indicating component is also attached with the power supply to indicate the power ON condition of power supply unit.

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Fig.3.24 Ciruit Diagram of Power Supply

Now the aim is to design the power supply section which converts 230V AC in to 5V DC. Since 230V is too high to reduce it to directly 5V DC, therefore we need a step down transformer that reduces the line voltage to certain voltage that will help us to convert it in to a 5V DC. Considering the efficiency factor of the full wave, we came to a conclusion to choose a transformer, whose secondary voltage is 3-4 higher than the required voltage. Thus a step down transformer of 9 V and 500 mA is used to step down the AC power supply. This transformer can provide current up to 750 mA. Our circuit load is below 750 mA. So there will not be any loading effect on transformer. Output of transformer is given to the rectifier circuit. We are using a central tapped full wave rectifier. In this rectifier we are using 1N4007 pn diode to rectify AC voltage. Output of this rectifier is not purely DC. Output of rectifier is rippled DC. So we need some filtering section to rectify these ripples. Output voltage of rectifier can be calculated by:-

Vout = (Vin * √2)- (Forward voltage drop of diode)

1N4007 is a silicon semiconductor material based diode. So in this case forward Voltage drop is .7 V. Final output of this rectifier be:-

Vout= (12*√2)- .7

Vout= 16.1 V

Rectifier circuit is build of capacitor. A capacitor of 1000uF,25V is used to filter the ripples. Output of capacitor is almost pure DC. But its voltage is 16V and we need +5V DC. So we are using a voltage regulator to get the desired +5V DC. A 7805 voltage regulator is a suitable component for this purpose. Output of 7805 regulator is +5V DC. A capacitor of 470uf, 10V is used to further filter out the critical ripples. A LED is used as an indicating device. Most of LED operates at 1.5 to 2.5V voltage range with 8-10 mA. LED used here is of 5mm size. We consider

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that LED operating at 1.6V with 8mA current. We can calculate the value of resistor using the KVC law.

Total Voltage = Voltage across resistor+ Voltage across LED

LED and resistor are connected in series so same current will flow. Means 8mA current will flow through the resistor.

Now Total Voltage is =5V

Voltage across resistor is =1.6v

Current is = 10mA

So our equation will be

5V= (10mA * resistance) + 1.6V

3.4V=10mA * resistance

Resistance =3.4/10mA

= 450 ohm.Thus we can calculate the any series resistor for any input voltage and LED

3.3 Keyboard Protocol

To send a key stroke, the keyboard begins driving the clock line. On the falling edge of the clock line, the data line represents the current bit. Each keystroke is sent as 11 bits: first a start bit of 0, then the 8 bits of the scan code (least significant bit first), then a parity bit (odd parity, which we did not implement for simplicity's sake), and finally a stop bit (always 1).

Fig.3.25 Keyboard Clock Scanning

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Scan Codes:As is the unfortunate case with standards and protocols there are usually more than one different version of it. Most PS/2 keyboards you find default to Scan Code Set 2. Even though most of the common characters are represented with a single 8 bit scan code, some of the keys are "extended" keys whose scan code is more than 8 bits. In that case, the keyboard just sends two sets of 11 bit frames.

In addition to letting you know when a key was pressed, the keyboard also sends a break code when a key is released. The break code for most characters happens to be 0xF0 followed by the code for the key. Our simple implementation ignores realease keys for the most part, except in the case of the Shift key. It does keep track of when the shift key is pressed, and when it is released. It is up to the main code, not the interrupt, to adjust the displayed characters accordingly.

Our code uses an array to store the relationship between scan codes and the character pressed. We use the scan code to index into an array of characters that holds the correct character at a given position. For example, the 'a' key has a scan code 0x1C (this is a way of saying 1C in hexadecimal, which is 28 in decimal or 00011100 in binary). Our mapping array holds the character a, in the 0x1Cth position. This way, to render a scan code into a character we merely need to do a constant time lookup into the array with the scan code.

The PS/2 protocol can actually do two-way communication -- that is to say you can actually send information to the keyboard. This can be used to set the LED lights on the keyboard (can anybody says dancing lights routine?). You can also adjust certain parameters on the keyboard including the delay between repeating keys, and the rate at which the keyboard sends repeating keys.

3.4 RF Modules:-

Radio frequency (RF) is a rate of oscillation in the range of about 30 kHz to 300 GHz, which corresponds to the frequency of electrical signals normally used to produce and detect radio waves. RF usually refers to electrical rather than mechanical oscillations, although mechanical RF systems do exist

In order to receive radio signals an antenna must be used. However, since the antenna will pick up thousands of radio signals at a time, a radio tuner is necessary to tune in to a particular frequency (or frequency range). This is typically done via a resonator – in its simplest form, a circuit with a capacitor and an inductor forming a tuned circuit. The resonator amplifies oscillations within a particular frequency band, while reducing oscillations at other frequencies outside the band. Often the inductor or the capacitor of the tuned circuit is adjustable allowing the user to change the frequencies at which it resonates. The resonant frequency of a tuned circuit is given by the formula

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where f0 is the frequency in hertz, L is inductance in henries, and C is capacitance in farads.

Special properties of RF electrical signals:-Electrical currents that oscillate at RF have special properties not shared by direct current signals. One such property is the ease with which they can ionize air, creating a conductive path through it. This property is exploited by 'high frequency' units used in electric arc welding, although strictly speaking these machines do not typically employ frequencies within the HF band. Another special property is that RF current cannot penetrate deeply into electrical conductors but flows along the surface of conductors; this is known as the skin effect. Another property is the ability to appear to flow through paths that contain insulating material, like the dielectric insulator of a capacitor. The degree of effect of these properties depends on the frequency of the signals.

Radio Frequency (RF) is the use of radio signals to communicate real-time data from the warehouse floor to the WMS database and back to the floor. This expedites processing in the warehouse. Scanners collect the data and transmit it via radio frequency to antennas located throughout the warehouse. From the antennas, the signal proceeds to an access point that communicates with the warehouse management system. This process reduces paper, data entry time delays, cycle count processing, out of stock quantities, typing errors, and misshipments

The receiver also operates at 433.92MHz, and has a sensitivity of 3uV. The RWS-434 receiver operates from 4.5 to 5.5 volts-DC, and has both linear and digital outputs.

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Fig:3.26. Pin Diagram of RWS-434

The TWS-434 and RWS-434 are extremely small, and are excellent for applications requiring short-range RF remote controls. The transmitter module is only 1/3 the size of a standard postage stamp, and can easily be placed inside a small plastic enclosure.

TWS-434: The transmitter output is up to 8mW at 433.92MHz with a range of approximately 400 foot (open area) outdoors. Indoors, the range is approximately 200 foot, and will go through most walls.TWS-434 transmitter accepts both linear and digital inputs, can operate from 1.5 to 12 Volts-DC.The TWS-434 as approximately the size of a standard postage stamp.

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Fig 3.27 Pin Diagram of TWS-434

Chapter 4

ASSEMBLY PROGRAMMING

4.1 Software Details(KEIL)

• Open Keil from the Start menu

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The Figure below shows the basic names of the windows referred in this document

• Select New Project from the Project Menu.

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• Name the project ‘Toggle.a51’

• Click on the Save Button.

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• The device window will be displayed.

• Select the part you will be using to test with. For now we will use the Dallas

Semiconductor part at89s52.

• Double Click on the Atmel Semiconductor.

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• Scroll down and select the at89s52 Part and Click OK.

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• Click File Menu and select New.

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• A new window will open up in the Keil IDE.

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4.2 Program Code for Transmitter:-

;RF Notice board Transmitter;************************************************************

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RS BIT P2.5 RW BIT P2.4 E BIT P2.3 FL BIT P0.7 LCD EQU P0 kclock BIT P2.0kdata BIT P2.1C1 EQU 31H C2 EQU 32H C3 EQU 33H d1 equ 34hd2 equ 35hd3 equ 36h d4 equ 37h C4 EQU 38HC5 EQU 39HC6 EQU 3AHRFTX equ 3bh ORG 00H ;;;;;;;;;;;;;;;;;;;;start: MOV A,#38H ;2*16 MATRIX CALL COMMAND MOV A,#06 ;RETURN HOME CALL COMMAND MOV A,#01 ;CLEAR DISPLAY SCREEN CALL COMMAND MOV A,#0CH ;DISPLAY ON CURSOR OFF CALL COMMAND MOV A,#80H ;MOVE CURSOR TO FIRST LINE SECOND COLOUMN CALL COMMAND MOV DPTR,#TABLE1 CALL DISPLAY back:CALL KEYBOARDREAD;jnb p1.0,aa0MOV A,C6CJNE A,#'*',BACK

mov a,#80hacall command

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mov dptr,#table2acall displaymov b,#10mov r1,#40hback2:CALL KEYBOARDREADacall delay1aas: mov @r1,a

inc r1dec r2

jmp read_pass

read_pass: mov a,40hcjne a,#'1',invalidclr amov a,41hcjne a,#'4',invalidclr amov a,42hcjne a,#'3',invalid

mov a,#80hacall commandmov dptr,#table3acall displaydec r2

hhj:mov a,@r0MOV RFTX,acall send_dataacall delay1inc r0djnz r2,hhjljmp start

invalid:mov a,#80Hacall command mov dptr,#table4acall displayacall delay1acall delay1acall delay1

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ljmp start

SEND_DATA:mov a,RFTX ; data byteCALL serial_txret

serial_tx:mov tmod,#20hmov th1,#-3 mov scon,#50hsetb tr1 mov sbuf,ahere: jnb ti,here

clr tiRET

delay1:acall delayacall delayacall delayacall delayret

Keyboardread:RECHECK:MOV C5,#00 ; MAKE STORE VALUE ZEROMOV A,P2ANL A,#03HCJNE A,#00H,RECHECK ;ANY BUTTON PRESSED

FINDKEY:MOV C4,#08H

NEXTBIT:JNB KCLOCK,$JB KCLOCK,$ ; WAIT FOR ONE CLOCK

CYCLEJNB KDATA,LOWDATASETB C

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JMP SHIFTDATALOWDATA: CLR CSHIFTDATA:MOV A,C5

RLC A MOV C5,A

DJNZ C4,NEXTBIT

FINDOUT: ; mov a,#0c0h; acall command

MOV A,C5CJNE A,#56,B2MOV A,#'A'MOV C6,#'A'CALL WRITEJMP Keyboardreadret

B2: CJNE A,#76,B3MOV A,#'B'MOV C6,#'B'CALL WRITEJMP Keyboardreadret

B3: CJNE A,#196,B4MOV A,#'D'MOV C6,#'D'CALL WRITEJMP Keyboardreadret

B4: CJNE A,#36,B5MOV A,#'E'MOV C6,#'E'CALL WRITEJMP Keyboardreadret

B5: CJNE A,#212,B6MOV A,#'F'MOV C6,#'F'CALL WRITEJMP Keyboardreadret

B6: CJNE A,#44,B7MOV A,#'G'MOV C6,#'G'CALL WRITE

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JMP KeyboardreadretB7: CJNE A,#204,B8

MOV A,#'H'MOV C6,#'H'CALL WRITEJMP Keyboardreadret

B8: CJNE A,#194,B9MOV A,#'I'MOV C6,#'I'CALL WRITEJMP Keyboardreadret

B9: CJNE A,#220,B10MOV A,#'J'MOV C6,#'J'CALL WRITEJMP Keyboardreadret

B10: CJNE A,#66,B11MOV A,#'K'MOV C6,#'K'CALL WRITEJMP Keyboardreadret

B11: CJNE A,#210,B12MOV A,#'L'MOV C6,#'L'CALL WRITEJMP Keyboardreadret

B12: CJNE A,#92,B13MOV A,#'M'MOV C6,#'M'CALL WRITEJMP Keyboardreadret

B13: CJNE A,#140,B14MOV A,#'N'MOV C6,#'N'CALL WRITEJMP Keyboardreadret

B14: CJNE A,#34,B15MOV A,#'O'MOV C6,#'O'CALL WRITE

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JMP KeyboardreadretB15: CJNE A,#178,B16

MOV A,#'P'MOV C6,#'P'CALL WRITEJMP Keyboardreadret

B16: CJNE A,#168,B17MOV A,#'Q'MOV C6,#'Q'CALL WRITEJMP Keyboardreadret

B17: CJNE A,#180,B18MOV A,#'R'MOV C6,#'R'CALL WRITEJMP Keyboardreadret

B18: CJNE A,#216,B19MOV A,#'S'MOV C6,#'S'CALL WRITEJMP Keyboardreadret

B19: CJNE A,#52,B20MOV A,#'T'MOV C6,#'T'CALL WRITEJMP Keyboardreadret

B20: CJNE A,#60,B21MOV A,#'U'MOV C6,#'U'CALL WRITEJMP Keyboardreadret

B21: CJNE A,#84,B22MOV A,#'V'MOV C6,#'V'CALL WRITEJMP Keyboardreadret

B22: CJNE A,#184,B23MOV A,#'W'MOV C6,#'W'CALL WRITE

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JMP KeyboardreadretB23: CJNE A,#68,B24

MOV A,#'X'MOV C6,#'X'CALL WRITEJMP Keyboardreadret

B24: CJNE A,#172,B25MOV A,#'Y'MOV C6,#'Y'CALL WRITEJMP Keyboardreadret

B25: CJNE A,#88,B26MOV A,#'Z'MOV C6,#'Z'CALL WRITEJMP Keyboardreadret

B26: CJNE A,#104,B27MOV A,#'1'MOV C6,#'1'CALL WRITEJMP Keyboardreadret

B27: CJNE A,#132,B28MOV A,#'C'MOV C6,#'C'CALL WRITEJMP Keyboardreadret

B28: CJNE A,#120,B29MOV A,#'2'

MOV C6,#'2'CALL WRITEJMP Keyboardreadret

B29: CJNE A,#100,B30MOV A,#'3'

MOV C6,#'3'CALL WRITEJMP Keyboardreadret

B30: CJNE A,#164,B31MOV A,#'4'

MOV C6,#'4'CALL WRITE

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JMP KeyboardreadretB31: CJNE A,#116,B32

MOV A,#'5'MOV C6,#'5'

CALL WRITEJMP Keyboardreadret

B32: CJNE A,#108,B33MOV A,#'6'

MOV C6,#'6'CALL WRITEJMP Keyboardreadret

B33: CJNE A,#188,B34MOV A,#'7'

MOV C6,#'7'CALL WRITEJMP Keyboardreadret

B34: CJNE A,#124,B35MOV A,#'8'

MOV C6,#'8'CALL WRITEJMP Keyboardreadret

B35: CJNE A,#98,B36MOV A,#'9'

MOV C6,#'9'CALL WRITEJMP Keyboardreadret

B36: CJNE A,#162,C37MOV A,#'0'

MOV C6,#'0'CALL WRITEJMP Keyboardreadret

C37: CJNE A,#90,C38MOV C6,#'*'

JMP Keyboardreadret

C38: CJNE A,#148,Keyboardreadret2MOV A,#' '

MOV C6,#' 'CALL WRITEJMP Keyboardreadret

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Keyboardreadret:MOV A,C6mov @r0,ainc r2inc r0

Keyboardreadret2:RET

LCDCLR: MOV A,#01H ;CLEAR DISPLAY SCREEN ACALL COMMAND RET ; DISPLAY DATA ON LCD

HTD: ;CONVERT HEX(BINARY) TO ASCII MOV B,#10 DIV AB MOV C1,B MOV B,#10 DIV AB MOV C2,B MOV C3,A RET

OUT1: MOV A,C3 ORL A,#30H ACALL WRITEMOV A,C2 ORL A,#30H ACALL WRITE MOV A,C1 ORL A,#30H ACALL WRITE RET

DISPLAY: CLR A MOVC A,@A+DPTR JZ NEXT ACALL WRITE INC DPTR JMP DISPLAY NEXT:

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RET WRITE: ACALL delay_lcd MOV LCD,A SETB RS CLR RW SETB Enopnop CLR E RET COMMAND: ACALL delay_lcd MOV LCD,A CLR RS CLR RW SETB E nopnop CLR E RET

delay_lcd: mov r7,#15h

jjk: mov r6,#200djnz r6,$djnz r7,jjkret

DELAY: MOV R6,#255 AGAIN: MOV R7,#255 BACK7: DJNZ R7,BACK7 DJNZ R6,AGAIN RET TABLE1: DB 'Data ',0 TABLE2: DB 'Password ',0 TABLE3: DB 'Sending...',0 TABLE4: DB 'Invalid ',0 End

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4.3 Program Code for Receiver:-

RF Module (Receiver section);****************************************************************** RS BIT P2.5 RW BIT P2.4 E BIT P2.3 FL BIT P0.7 LCD EQU P0 C1 EQU 31H C2 EQU 32H C3 EQU 33H rxbyte equ 34h DATA_BYTE equ 35h

ORG 00H START: MOV A,#38H ;2*16 MATRIX ACALL COMMAND MOV A,#06 ;RETURN HOME ACALL COMMAND MOV A,#01 ;CLEAR DISPLAY SCREEN ACALL COMMAND MOV A,#0CH ;DISPLAY ON CURSOR OFF ACALL COMMAND MOV A,#80H ;MOVE CURSOR TO FIRST LINE SECOND COLOUMN ACALL COMMAND MOV DPTR,#TABLE1 ;DISPLAY ERP ACALL DISPLAY mov a,#0c0hacall commandMAIN:CALL SERIAL_RXMOV DATA_BYTE,A ; DATA BYTEcall writeJMP MAIN

SERIAL_RX:mov tmod,#20hmov th1,#-3 ; 24= 1200BPS

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mov scon,#50hsetb tr1clr rijnb ri,$mov a,sbufmov rxbyte,aREtDISPLAY: ; DISPLAY DATA ON LCD

CLR A MOVC A,@A+DPTR JZ NEXT ACALL WRITE INC DPTR JMP DISPLAY

NEXT: RET

WRITE: CALL LCD_DELAY MOV LCD,A SETB RS CLR RW SETB E CLR E RET

COMMAND: CALL LCD_DELAY MOV LCD,A CLR RS CLR RW SETB E

CLR E RET

LCD_DELAY: MOV R6,#5

AGAIN: MOV R7,#255 BACK: DJNZ R7,BACK

DJNZ R6,AGAIN

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RET

TABLE1: DB ' Notice Board ',0 End

Chapter 5

CONCLUSION AND FUTURE SCOPE

5.1 ConclusionWireless operations permit services, such as long-range communications, that are impossible or impractical to implement with the use of wires. It provides fast transfer of information and are

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cheaper to install and maintain. This paper provides an efficient way of displaying messages on Notice Board using Radio Frequency. It also provides user authentication in order to avoid any misuse of proposed system.We conclude that RF Notice Boards have various advantages:

• Instant information updates - no need to walk round pinning up lots of notices or posters.

• Environmentally friendly - reduce paper and printer toner usage and costs

• More visual messages - visual messages stand out more and attract attention

• Live information - can link to other computer systems for live information

• Relevant notices - set an expiry date to ensure notices are only shown when relevant

5.2 Future Scope

Reception Area Displays:Electronic Notice Boards are ideal for School, Business, Hotel and other Reception Areas. They can be used to display personalised greeting messages for clients, or display notices and information for other users. Read more about Reception Area Displays for Business and Electronic Notice boards in schools and education.

Call Centre Wallboards:Call centers have traditionally used scrolling LED electronic message boards, which are very limited in what information they can display. MediaCAT driven Electronic Notice Boards can not only display the same call statistics on the screen, but also scrolling messages for staff, product information and graphs of performance and targets. Read more about Call Centre Wallboards.

Wayfinding and Meeting Room Signs:Digital Wayfinding is an exciting new application for Electronic Notice Boards which allows Hotels, Conference and Exhibition Centers and Large Corporates to enhance their customers experience of their facilities. By using MediaCAT Digital Signage players to create dynamic Wayfinding signs in reception areas , foyers, hallways and meeting rooms, customers can be shown the way to their appointments and meetings with automatic directional signage.

CHAPTER 6

SUMMARY

We have used RF frequency in this project to design a wireless RF notice board. In this project data is transferred one end to another end through RF. Data will be transmitted by 433 MHz RF transmitter. At the receiving side these codes will be received by 433 MHz RF receiver.

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We use AT89S52 microcontroller. This controller is basically a 40 pin ic. ROM of 89s52 is 8k and ram is 256 byte. We are using 16*2 lcd in this project. Lcd is connected to port 0 which will display the data. We are using a keyboard to enter the text, which is processed by the microcontroller and displayed on the LCD then RF modules are used to transmit this data to receiver end.

At the receiver end RF module receives the encoded data and generates the actual form and display it on the notice board.

This project used two power supplies +5v DC and +9VDC. 5 volt dc power supply is a regulated power supply. For the regulated power supply we use IC 7805 as a regulator to provide a fix 5 volt power supply. For the +9V we used the 9v battery.

REFERENCES

A. Mazidi, Muhammad Ali & Janice Gillispie & Mckinlay,Rolin D. “8051 Microcontroller and Embedded Systems”,Pearson Education.

B. J. S. Lee, ”Performance Evaluation of IEEE 802.15.4 for Low-Rate Wireless Personal Area Networks”, IEEE Transactions on Consumer Electronics, vol. 52, no. 3, pp. 742-749 , August 2006.

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Websites:www.logitechprojects.com

www.atmel.com

www.keil.com

www.rentron.com

www.datasheet4u.com/datasheet/T/W/S/ TWS - 434 _ETC.pdf.html

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