Radio Frequency Identification RFID

Part I : Basics

Introduction

RFID, its application, standardisation, and innovation are constantly changing. Its adoption is still relatively new and hence there are many features of the technology that are not well understood by the general populace. Developments in RFID technology continue to yield larger memory capacities, wider reading ranges, and faster processing. It’s highly unlikely that the technology will ultimately replace bar code - even with the inevitable reduction in raw materials coupled with economies of scale, the integrated circuit in an RF tag will never be as cost-effective as a bar code label. However, RFID will continue to grow in its established niches where bar code or other optical technologies aren’t effective. If some standards commonality is achieved, whereby RFID equipment from different manufacturers can be used interchangeably, the market will very likely grow exponentially.
This document tries to set out the basic information about RFID in a simple format that can be understood by everyone. AIM’s purpose is to provide education on RFID and hence increase the use of the technology. This is part one of a three part series that will also include:
Part II : Application Case Studies
Part III : Getting Started in RFID - A Step approach
A moment’s thought about radio broadcasts or mobile telephones and one can readily appreciate the benefits of wireless communication. Extend those benefits to communication of data, to and from portable low cost data carriers, and one is close to appreciating the nature and potential of radio frequency identification (RFID). RFID is an area of automatic identification that has quietly been gaining momentum in recent years and is now being seen as a radical means of enhancing data handling processes, complimentary in many ways to other data capture technologies such bar coding. A range of devices and associated systems are available to satisfy an even broader range of applications. Despite this diversity, the principles upon which they are based are quite straight forward, even though the technology and technicalities concerning the way in which they operate can be quite sophisticated. Just as one need not know the technicalities of a mobile phone or personal computer to use it, it is not necessary to know the technicalities to understand the principles, considerations and potential for using RFID. However, a little technical appreciation can provide advantage in determining system requirements and in talking to consultants and suppliers.

What is RFID?

The object of any RFID system is to carry data in suitable transponders, generally known as tags, and to retrieve data, by machine-readable means, at a suitable time and place to satisfy particular application needs. Data within a tag may provide identification for an item in manufacture, goods in transit, a location, the identity of a vehicle, an animal or individual. By including additional data the prospect is provided for supporting applications through item specific information or instructions immediately available on reading the tag. For example, the colour of paint for a car body entering a paint spray area on the production line, the set-up instructions for a flexible manufacturing cell or the manifest to accompany a shipment of goods.
A system requires, in addition to tags, a means of reading or interrogating the tags and some means of communicating the data to a host computer or information management system. A system will also include a facility for entering or programming data into the tags, if this is not undertaken at source by the manufacturer. Quite often an antenna is distinguished as if it were a separate part of an RFID system. While its importance justifies the attention it must be seen as a feature that is present in both readers and tags, essential for the communication between the two.

Data transfer rate and bandwidth

Choice of field or carrier wave frequency is of primary importance in determining data transfer rates. In practical terms the rate of data transfer is influenced primarily by the frequency of the carrier wave or varying field used to carry the data between the tag and its reader. Generally speaking the higher the frequency the higher the data transfer or throughput rates that can be achieved. This is intimately linked to bandwidth or range available within the frequency spectrum for the communication process. The channel bandwidth needs to be at least twice the bit rate required for the application in mind. Where narrow band allocations are involved the limitation on data rate can be an important consideration. It is clearly less of an issue where wide bandwidths are involved. Using the 2.4 - 2.5 GHz spread spectrum band, for example, 2 megabits per second data rates may be achieved, with added noise immunity provided by the spread spectrum modulation approach. Spread spectrum apart, increasing the bandwidth allows an increase noise level and a reduction in signal-to-noise ratio. Since it is generally necessary to ensure a signal is above the noise floor for a given application, bandwidth is an important consideration in this respect.

Range and Power Levels

The range that can be achieved in an RFID system is essentially determined by:
􀂾 The power available at the reader/interrogator to communicate with the tag(s)
􀂾 The power available within the tag to respond
􀂾 The environmental conditions and structures, the former being more significant at higher frequencies including signal to noise ratio
Although the level of available power is the primary determinant of range the manner and efficiency in which that power is deployed also influences the range. The field or wave delivered from an antenna extends into the space surrounding it and its strength diminishes with respect to distance. The antenna design will determine the shape of the field or propagation wave delivered, so that range will also be influenced by the angle subtended between the tag and antenna.
In space free of any obstructions or absorption mechanisms the strength of the field reduces in inverse proportion to the square of the distance. For a wave propagating through a region in which reflections can arise from the ground and from obstacles, the reduction in strength can vary quite considerable, in some cases as an inverse fourth power of the distance. Where different paths arise in this way the phenomenon is known as “multi-path attenuation”. At higher frequencies absorption due to the presence of moisture can further influence range. It is therefore important in many applications to determine how the environment, internal or external, can influence the range of communication. Where a number of reflective metal ‘obstacles’ are to encountered within the application to be considered, and can vary in number from time to time, it may also be necessary to establish the implications of such changes through an appropriate environmental evaluation.
The power within the tag is generally speaking a lot less than from the reader, requiring sensitive detection capability within the reader to handle the return signals. In some systems the reader constitutes a receiver and is separate from the interrogation source or transmitter, particularly if the ‘up-link’ (from transmitter-to-tag) carrier is different from the ‘down-link’ (from tag-to-reader).
Although it is possible to choose power levels to suit different application needs is not possible to exercise complete freedom of choice. Like the restrictions on carrier frequencies there are also legislative constraints on power levels. While 100 - 500mW are values often quoted for RFID systems actual values should be confirmed with the appropriate regulatory authorities, in the countries where the technology is to be applied. The authorities will also be able to indicate the form in which the power is delivered, pulsed or continuous, and the associated allowed values.
Having gained some grasp of the data communication parameters and their associated values it is appropriate to consider, in a little more detail, the components of an RFID system.

Transponders/Tags Reader / ProgrammerTransponderor TagReader AntennaAir InterfaceTagAntenna

The word transponder, derived from TRANSmitter/resPONDER, reveals the function of the device. The tag responds to a transmitted or communicated request for the data it carries, the mode of communication between the reader and the tag being by wireless means across the space or air interface between the two. The term also suggests the essential components that form an RFID system – tags and a reader or interrogator. Where interrogator is often used as an alternative to that of reader, a difference is sometime drawn on the basis of a reader together with a decoder and interface forming the interrogator.
The basic components of a transponder may be represented as shown below. Generally speaking they are fabricated as low power integrated circuits suitable for interfacing to external coils, or utilising "coil-on-chip" technology, for data transfer and power generation (passive mode).
Basic features of an RFID transponder:
The transponder memory may comprise read-only (ROM), random access (RAM) and non-volatile programmable memory for data storage depending upon the type and sophistication of the device. The ROM-based memory is used to accommodate security data and the transponder operating system instructions which, in conjunction with the processor or processing logic deals with the internal "house-keeping" functions such as response delay timing, data flow control and power supply switching. The RAM-based memory is used to facilitate temporary data storage during transponder interrogation and response.
The non-volatile programmable memory may take various forms, electrically erasable programmable read only memory (EEPROM) being typical. It is used to store the transponder data and needs to be non-volatile to ensure that the data is retained when the device is in its quiescent or power-saving "sleep" state.
Data buffers are further components of memory, used to temporarily hold incoming data following demodulation and outgoing data for modulation and interface with the transponder antenna. The interface circuitry provides the facility to direct and accommodate the interrogation field energy for powering purposes in passive transponders and triggering of the transponder response. Where programming is accommodated facilities must be provided to accept the data.

The transponder antenna is the means by which the device senses the interrogating field and, where appropriate, the programming field and also serves as the means of transmitting the transponder response to interrogation.
A number of features, in addition to carrier frequency, characterise RFID transponders and form the basis of device specifications, including:
􀂾 Means by which a transponder is powered
􀂾 Data carrying options
􀂾 Data read rates
􀂾 Programming options
􀂾 Physical form
􀂾 Costs
Powering tags - For tags to work they require power, even though the levels are invariably very small (micro to milliwatts). Tags are either passive or active, the designation being determined entirely by the manner in which the device derives its power.
Active tags are powered by an internal battery and are typically read/write devices. They usually contain a cell that exhibits a high power-to-weight ratio and are usually capable of operating over a temperature range of -50°C to +70°C. The use of a battery means that a sealed active transponder has a finite lifetime. However, a suitable cell coupled to suitable low power circuitry can ensure functionality for as long as ten or more years, depending upon the operating temperatures, read/write cycles and usage. The trade-off is greater size and greater cost compared with passive tags.
In general terms, active transponders allow greater communication range than can be expected for passive devices, better noise immunity and higher data transmissions rates when used to power a higher frequency response mode.
Passive tags operate without an internal battery source, deriving the power to operate from the field generated by the reader. Passive tags are consequently much lighter than active tags, less expensive, and offer a virtually unlimited operational lifetime. The trade-off is that they have shorter read ranges than active tags and require a higher-powered reader. Passive tags are also constrained in their capacity to store data and the ability to perform well in electromagnetically noisy environments. Sensitivity and orientation performance may also be constrained by the limitation on available power. Despite these limitations passive transponders offer advantages in terms of cost and longevity. They have an almost indefinite lifetime and are generally lower on price than active transponders.

Data carrying options - Data stored in data carriers invariable require some organisation and additions, such as data identifiers and error detection bits, to satisfy recovery needs. This process is often referred to as source encoding. Standard numbering systems, such as UCC/EAN and associated data defining elements may also be applied to data stored in tags. The amount of data will of course depend on application and require an appropriate tag to meet the need. Basically, tags may be used to carry:
􀂾 Identifiers, in which a numeric or alphanumeric string is stored for identification purposes or as an access key to data stored elsewhere in a computer or information management system, or
􀂾 Portable data files, in which information can be organised, for communication or as a means of initiating actions without recourse to, or in combination with, data stored elsewhere.
In terms of data capacity tags can be obtained that satisfy needs from single bit to kilobits. The single bit devices are essentially for surveillance purposes. Retail electronic article surveillance (EAS) is the typical application for such devices, being used to activate an alarm when detected in the interrogating field. They may also be used in counting applications.
Devices characterised by data storage capacities up to 128 bits are sufficient to hold a serial or identification number together, possibly, with parity check bits. Such devices may be manufacturer or user programmable. Tags with data storage capacities up to 512 bits, are invariably user programmable, and suitable for accommodating identification and other specific data such as serial numbers, package content, key process instructions or possibly results of earlier interrogation/response transactions.
Tags characterised by data storage capacities of around 64 kilobits may be regarded as carriers for portable data files. With increased capacity the facility can also be provided for organising data into fields or pages that may be selectively interrogated during the reading process.

Data read rate – It has been mentioned already that data transfer rate is essentially linked to carrier frequency. The higher the frequency, generally speaking the higher the transfer rates. It should also be appreciated that reading or transferring the data requires a finite period of time, even if rated in milliseconds, and can be an important consideration in applications where a tag is passing swiftly through an interrogation or read zone.

Areas of Application for RFID

Potential applications for RFID may be identified in virtually every sector of industry, commerce and services where data is to be collected. The attributes of RFID are complimentary to other data capture technologies and thus able to satisfy particular application requirements that cannot be adequately accommodate by alternative technologies. Principal areas of application for RFID that can be currently identified include:
􀂾 Transportation and logistics
􀂾 Manufacturing and Processing
􀂾 Security
A range of miscellaneous applications may also be distinguished, some of which are steadily growing in terms of application numbers. They include:
􀂾 Animal tagging
􀂾 Waste management
􀂾 Time and attendance
􀂾 Postal tracking
􀂾 Airline baggage reconciliation
􀂾 Road toll management
As standards emerge, technology develops still further, and costs reduce considerable growth in terms of application numbers and new areas of application may be expected.
Some of the more prominent specific applications include:
􀂾 Electronic article surveillance - clothing retail outlets being typical.
􀂾 Protection of valuable equipment against theft, unauthorised removal or asset management.
􀂾 Controlled access to vehicles, parking areas and fuel facilities - depot facilities being typical.
Automated toll collection for roads and bridges - since the 1980s, electronic Road-Pricing (ERP) systems have been used in Hong Kong.
􀂾 Controlled access of personnel to secure or hazardous locations.
􀂾 Time and attendance - to replace conventional “slot card” time keeping systems.
􀂾 Animal husbandry - for identification in support of individualised feeding programmes.
􀂾 Automatic identification of tools in numerically controlled machines - to facilitate condition monitoring of tools, for use in managing tool usage and minimising waste due to excessive machine tool wear.
􀂾 Identification of product variants and process control in flexible manufacture systems.
􀂾 Sport time recording
􀂾 Electronic monitoring of offenders at home
􀂾 Vehicle anti-theft systems and car immobiliser
A number of factors influence the suitability of RFID for given applications. The application needs must be carefully determined and examined with respect to the attributes that RFID and other data collection technologies can offer. Where RFID is identified as a contender further considerations have to be made in respect of application environment, from an electromagnetic standpoint, standards, and legislation concerning use of frequencies and power levels.

HOME SECURITY SYSTEM

Introduction

This is a digital home security system with voice feature which can monitor room temperature, smoke, motion, and
windows & doors.

The goal of this project is to utilize the after-market parts and build an integrated home security system. Besides
traditional magnetic switch equipped on doors and windows, we have also incorporated temperature sensor, smoke
detectors, and motion sensor. Hence the security system will sound an alert when there is an attempt of break-in
or if there is possible smoke or fire.

The system is fully digital and also be fully customized. It incorporated a 16x2 LCD display with a 4x4 keypad. Each
sensor can be enabled or disabled, and alarm frequency and skim can also be chosen by users. We have also
equipped a voice playback chip, and it will speak which sensor has gone wrong.

High Level Design
Project Idea

The idea of our project comes from lab 3 when we did a simple security system. However, that security
system is quite basic and only offers simple password lock. Hence we would like to enhance our
security system with different kinds of sensors. We have also browse some of the old final project and
found the "Phone Dialer" project from spring 2002. Originally, we were going to put Zarlink MT8880C
DTMF transceiver chip, so it will dial a desire number that user specify. When the phone connected, we
will use Winbond ISD1420 voice record and playback chip to play pre-recorded voice signal. However,
due to the lack of the phone jack in the lab, plus the majority of the Cornell campus has digital phone
line instead of analog phone line, we decided to put away this idea. Since ISD1420 chip has address bit
feature, we decided to make our system playback certain pattern of voice when the system goes into alert status.

Program & Hardware Design
Program Detail


The hardest part of the program is timing. When any sensor goes wrong, the program will wait for
certain seconds (set by user), and then make ISD1420 chip play back the desired voice pattern we
want. Originally, we though we can just output the appropriate address bit and then make the chip
play, however, later on we discovered there is a THOLD in the ISD1420 chip that we need to take care
of, otherwise it will reference to the previous address bits. The voice playback chip does not have a
very fast internal clock, so we have to manually use the delay function in our program after we set the
address bits, and then make the chip play. Although using the delay function is somehow undesirable,
however, we have implemented our program such that this delay will not cause any error in our
software.
Besides, we also need to implement the keypad function so it acts accordingly when the LCD is
displaying certain menu. This is not very difficult but we have to take care of all the possible
circumstances. We have 12 submenus in our system. Set temp define the lowest temperature allowed
before sounding the alarm (70~120F, with step size of 1F). The Sec. Allow is the time in second before
the voice alarm goes off (0~30sec, with step size of 2 seconds).
We also have simple de-bounce feature for our keypad, and it will sound a buzz when you press any
key (if you HOLD a key but buzz will only sound once). Although the de-bounce function is as easy as
1.Enable System
2.(*)Temp Sensor
3.(*)Mot. Sensor
4.(*)Smk. Sensor
5.(*)Mag. Switch
6.Set Temp: 100F
7.(*)Voice Alarm
8.(*)Buzz Alarm
9.New Pswd:
A.Buzz Freq: 7
B.Buzz Skim: 3
C.Sec. Allow: 10
We also have simple de-bounce feature for our keypad, and it will sound a buzz when you press any
key (if you HOLD a key but buzz will only sound once). Although the de-bounce function is as easy as
1.Enable System
2.(*)Temp Sensor
3.(*)Mot. Sensor
4.(*)Smk. Sensor
5.(*)Mag. Switch
6.Set Temp: 100F
7.(*)Voice Alarm
8.(*)Buzz Alarm
9.New Pswd:
A.Buzz Freq: 7
B.Buzz Skim: 3
C.Sec. Allow: 10
lines, it takes a while to think about the logic and how to actually implement it. Also we implement
the backspace feature so that when use enter a wrong password, this key can be used to delete the
previous entered number. Also just a quick note, our password is masked on LCD for a safer purpose.

Hardware Detail
The first sensor we have is the temperature sensor. Since we implemented a digital thermometer in lab
5, we decided to use the same circuit. So we incorporated National Semiconductor LM34 temperature
sensor, with National Semiconductor LMC7111 OpAmp chip to amplifier our output voltage going into
ADC. The final connection of our circuit look like the following.

The second sensor we have is the motion sensor. Although we do not have the diagram of the circuit (it
has some IC components), we discovered there are few NPN transistors in the circuit. NPN transistors
are like switches, so it is obvious these are used enable the original buzzer on the circuit. Hence we
took the base pin together with ground to connect to our ADC pin input. If the voltage exceed VTH
(threshold voltage), we know the alarm goes off.

The third sensor we have is the smoke detector. The smoke detectors mostly equipped with
piezoelectric buzzer, which has F (feed back), C (main electrode), M (metal plate) three pins.
Piezoelectric buzzer has an internal crystal and will sound if small current is applied (voltage drop).
Hence we took out the piezoelectric buzzer and connect the F pin into our ADC input. When the sensor
goes off, the voltage will go high.

The final sensor we have is the magnetic switches. It is normally closed. So when the switch is right
next to each other, the resistance is zero. When the switch is separated, the resistance will become
infinity as if it’s disconnected. So we drive the switch with an 10K pull-up resistor, and connect the
output to the ADC. Since we have two magnetic switches, we decided to build a simple AND/OR gate
by using 1 74LS00 chip. There are four NAND gates in 74LS00, and if we connect two of NAND gate in
parallel with their input signal to another NAND gate, we will get as if there are 2 AND gate in parallel
with their signals to an OR gate. The diagram can be found in our appendix.

Speed of Execution

The speed of the execution is work very well. In the beginning the system will boot up with default
password 1234. The user can now navigate through our menu, and enable or disable each type of
sensor. If a particular sensor is enabled, the LCD screen will output a * symbol before the sensor
name. User can also set the alert temperature, enable/disable voice or buzzer alarm, and even specify
the ring tone and frequency of the buzzer alarm and the time before voice alarm goes off. The button
de-bounce scheme also works fine so users can navigate through the menu and use the keypad
perfectly.


Accuracy

After the user enables the security system, the green status LED will lid to indicate the system status.
User can now enter proper password to unlock the system. If any sensor goes wrong, the LCD will
output ERROR and with proper initial for the sensor (T for temperature, M for motion, S for smoke, D
for door or window magnetic switch). The red led light be will flashing at 4Hz to indicate such event. If
the buzz alarm is enable, it will sound the tone that user choose. If the voice alarm is enabled, it will
wait for few seconds (user specified), if the system is still not locked, then it will start playing voice to
indicate which sensor goes wrong. (For example, "Temperature Error, please check and unlock the
security system.") If another sensor goes wrong after that, the system will also act accordingly and
indicate that in the voice alert in addition to the LCD screen. ("Temperature Motion Error, please check
and unlock the security system.")


Conclusions

Expectation and Improvement
The result of our design has met our expectation, in which every sensor is working and will sound
specific alarm when the system goes into alert status. The keypad and LCD also offer great interface
and users can be familiar with our system in less than few seconds.
If we have chance to design this project again, we will add a phone dialer chip like the Zarlink MT8880C
we mentioned before. By doing so, we can make sure if no one is at home or if no one is around the
area, someone else can be notified to take immediate action. In addition, we feel like our PORTB is a
little bit wasted. We only have 4 output patterns but we are using all 8 pins. Next time we will use 74LS
series chip together with only 2 output pins from MCP, so together we can save 6 I/O pins. Besides, we
will like to have another small microcontroller at a higher frequency, so we can output our buzz alarm
at a higher frequency tone.

Intellectual Property

Besides the reference circuit from ISD1420 chip specification, reference keypad decode scheme from
lab 3, and temperature sensor circuit from lab 5, we have designed and coded everything on our own.
There is no code from public domain, and we did not reuse any code from the previous lab (we do
reference, but not copy). Because we are using two pre-built sensor circuits (motion and smoke
sensor), we feel like we should not pattern our whole design. However, if we take out these two parts
and only have these “inputs,” we definitely have opportunity to pattern our design.

final year projects

FINAL YEAR ENGINEERING PROJECTS
FOR ELECTRONICS AND COMMUNICATION STUDENTS

Line follower Robot

This robot will follow the black line or it will only move on the black road ,and it will never go out of road.It will stop in case obsticle comes in it's passage. Based on 8051

We have fixed two light sensors on fore side on the robo. The principle of sensors is that black colour will normally observe the light where other colours will normally reflects the lights light source is fixed down ward Ld1 ,a white led reflected light will fall on the ldr if the light is more the resistance of the ldr is normally low and transister remains in cutoff state When the robo moves on the black road , the light reflected is less and the ldr resistance is increasd, vr1 forms a potential driver along with ldr due to increase in resistance the base voltage on t1 will rise to conductionlevel and transister will go into on (conduction)state. Resulting it’s collector which was getting high logic from the default microcontroller pin will become low. This low logic detection confirms that the robo is on the black road if the robo is our of the black road this logic will become high and it indicates off-road. Depending upon the left or right sensor robo will move towards right or left direction in order to stay on road out put from both the sensors shoul be low when the robo is on the road....

final year projects

R.F.I.D FOR DIFFERENT APPLICATIONS

You must have seen on discovery channel that the people used to connect a tag to animal and then they used to monitor their location so that they can study their behaviour. With the advancement of technology same rfid’s are becoming popular, modern rfid consists of a transmitter and a receiver. Transmitter dose not require any power supply it receives it,s power solely from it,s antenna coil attached to it.at I a very small antenna coil and has a very low transmitting range. Transmitter range is within the range of few mm.receiver will have a display device normally a lcd and a data port from where data can be sent to pc. Advanced receivers have Real time clock with enough memory to store the data and later on the data can be transmitted to pc when it’s memory is full.

Most of the commercial available rfid tags and receiver are costly and is not possible by students to develop such devices , even components required are not easily available.

Application area: 1 Bus route application. 2 Attendence register 3 Inventry application 4 Security application 5 Rfid can be given to any living or non living thing which need accountabilitry.

final year project

AUTOMATIC INTELLIGENT TOLL -TAX

Automatic toll tax project is designed ,using atmel 89c51 microcontroller & descreate componants. Heart of the project is an ir transmitter and receiver modules ,these strong powerfull modules transmits 38khz strong ir beam, has a range of more than 15 feets are sufficiently enough for our project. I have designed this project as a simple emplementation of the toll collection process automatically in a model form. This should not be considered as a real toll collection system which require much more considerations , tests and huge amount of money, before they are actually put into use.

However this project gives enough guidelines for the actual dvelopment of the toll collection system. For the sake of simplicity , we have to make coin box exactly same as used in pco coin box machine fixed on railway station or else whare. We have to make two coin size holes one for one rupee, and other for five rupee coin. You have to fixup coin sensors on these holes, one sensor should be fixed for five rupee coin and one sensor for one rupee coin.

OPERATION: when light vehicle is detected, one rupee sensor led will glow also the device will speak out " please enter one rupee" in three languages. if the coin is inserted, it will stop asking for the coin and gate will open. when the vehicle croses other side of the gate the gate will close. also the count value on the lcd will be updated . operation is similar for heavy vehicle where the device is going to ask for "five rupee coin" the project will maintain the complete details of all the vehicles crossing that way.. so no vehicle can cross without paying.

final year project

HOME/ OFFICE SECURITY SYSTEM (8051 BASED

Security is a matter of great concern to all of us in this world. Normally there are four types of security threat to our property. 1 )Thief, an inturder. 2)Fire, so we use fire sensor. 3)Water spilage /over flow, so we use water sensor. 4) Gas leak , we use gas sensor, whenever there is security breach from one of above or any combination of above. The project takes the following action 1) Sounds an ALARM to attract your or public attention . 2) If the reset sw is not pressed within 30 seconds the projects takes further action, 3) It makes an emergency call to deliver an emergency message stored in speech IC. 4) It will make five attempts to call you before it checks the conditions again. The project presented here is based on world’ s most powerful intel’ s mcs-51 family of microcontroller atmel at89c51.

CIRCUIT EXPLANATION: This project is based on 8051 microcontroller.(IC2) IC3 and is used as buffer. IC4 is a one time programmable(otp) chip where messages are stored. This is 21 second speech ic where total of 12 messages can be recorded on eight different locations, but total duration should not be more than 21 seconds. Recorded messages can be played back by setting the trigger pin 10 & 11 to high, making these pin low will stop the message, Setting these pin high will repeatedly replay the same message. IC5 is an audio amplifire . Audio output from speech ic(IC4) pin no 7 cout is coupled to this ic on pin no 3 through VR2 volume control and C10. Amplified output from pin no 5 drives the speaker through capacitor C14. R14 and C13 corrects the tone. .C15 and C16 couples the audio message to telephone line.

IC4 needs 3.3v operating voltage .R9 is a voltage dropping resistor, D7 is 3.3v zener diode and C7 is a filter capacitor. These components will always maintain the voltage to3.3v at pin 9,12 of IC4. capacitor C8 is a feed back capacitor.,C9 and R13 connected to pin no 7 of IC 4 are tone corrector.R12 along with the VR1 variable resistor performs the sampling rate adjustment. R10 and R11 connected to pin26 and pin 27 of the microcontroller are voltage dropping resistors. R15 and R16 connected to the base of transister Q1 and Q2 are voltage dropping resistors and drives transistors Q1 & Q2 when set to high logic by microcontroller. Q1 Drives the dial relay RL1and Q2 drives the off-hook relay.RL2........................

FINAL YEAR PROJECT

Pc controlled vehicle

In this project, a vehicle (CAR) is selected and fitted with servo motors to control its motion (gears & stearing controls), a camera is also fitted to capture the front road. Two cell phones are used to communicate between the remote station and the vechile. A digital signal (commands from the controler) are send to the mobile throught the voice channal and the video LIVE is converted into digital and transmitted back to the station through the mobile voice channel. At remote station the digital signal recevied by the mobile ear peice is converted back to video signal and displayed on the screan. Here the remote station might be a LAPTOP, as the laptop can display the LIVE video, the key strokes are converted into digital to steer the vehicle and send it to the destination through the mobile.

final year projects

MICROPROCESSOR BASED RAILWAY SYSTEM

The aim of this project is to demonstrate the incorporation of computer method in railway traffic control to improve, safety, speed of handling the traffic and reliability. Here we employ the microprocessor (Intel 8085) to handle the signaling, track changing and gate operation and to monitoring the traffic. The system starts with the tracking if the train is sensed at the station side or starts with the gate operation (i.e. gate closing and opening) along with the track changing if the train is sensed at the gate side. Once the train arrival is sensed at a distance of about 3 kms the microprocessor performs the gate operation along with the track changing, the identification of the train is done at a distance of 3 kms accordingly the particular operation is performed by the processor. Depending upon the priority of the incoming train, the unengaged track is given for train halting..