Laser Synopses

8/7/2019 Laser Synopses

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A

SYNOPSES

ON

Data Communication & Security SystemUsing LASER

Submitted To

Electronics &Communication Engineering Department

of

MAHARANA PRATAP ENGINEERING COLLEGE ,

KOTHI, MANDHANA, KANPUR

SESSION :- (2009-10)


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ACKNOWLEDMENT

We wish to express our deep sense of gratitude to those whose encouragement and co-

operation has been a source of inspiration. Specially, it is an honor to thank Mr. Sunil

Kushwaha for acknowledge our Project topic Data Communication & Security

SystemUsing LASER.

We would also like to express our thanks to all those respected faculty

members of Department of Electronics & Communication Engineering who have

helped us and gave their permission for initiate our project.

Group Members

NEERAJ SAHU

MAHENDRA SHUKLA

AMIT KUMAR

ADISH JAIN

Staff Counselor Submitted By

Electronics & Communication

Engineering Department

NEERAJ SAHU

(0604631060)MAHENDRA SHUKLA(0604631047)AMIT KUMAR(0504631006)

ADISH JAIN (0604631005)E.C. - IV Year


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E.C. 4th year

ABSTRACT

In this project we will transmits the data using a LASER beam by inputting the data from

our PC then receive the corresponding data wirelessly and transmitted data will visible on

DIGITAL DISPLAY SYSTEM.

The laser module (TIM202) module is a small (38x14x14 mm) semicunductor;similar to those types used in laser pointers which takes 3V 45mA and outputs 3-5mW

670nm laser beam. We implement a simple LASER data link using this semiconductor

laser module and some kind of receiver. We will use a fiber optic receiver module as a

receiver. module is designed for 665nm wavelength and it can operate up to 5 mbit/s.Now we connected the circuit to the serial-port of a PC. Using a PC circuit can be operate

with different communication speeds. At the receiver side well use a display system onwhich we can see the transmitted data

( text or number ).

Undertaking the laser for security system therefor If any person try to hack the

transmitted data from communication medium (LASER path through air) the securityalarm will get ON. Well also show in our project how to protect a object by using

LASER beam.


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CONTENT

Introduction of Datacommunication

Security system

LASER

LASER Cunstruction

LASER Physics

Spectral Outputs of Several LASER

Sensors

PC Interfacing

RS-232

RS232 Data Interface

Signals

RTS/CTS handshaking

IC Used

Circuit Diagram for Data Communication

Transmitter Block Diagram

Reciever block Diagram

Security System Circuit Diagram

An introduction of Visual Basic

References


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Introduction of Data Communication:-

To send digital information through the laser communication device, the inputaudio

signal must be converted into a series of digital bits. Before this can beaccomplished,some formatting has to be performed on the analog audio signal comingfrom the CD

player. The analog input is a 100-200mVp-p signal. It is first sent through a filtering

circuit to block any DC offset and center the input signal at 0V. The signal is then

amplified with a gain of 20 using an opamp. Finally, a filter and clamping circuitare usedto attenuate frequencies below 10Hz and flip the negative values positive forA/D

conversion. The conversion is completed using an AD7819 chip. This chip samples the

analog signal at 125kHz (controlled by a clock signal from 555 timer) and outputs to an8-bit parallel interface. Sampling is accomplished by reading the voltage level of the

analog signal at a certain time interval (for this system, the sample period is 8 s). This

voltage is then assigned one of 256 distinct voltage levels and given an 8-bit sequence todescribe the voltage level in digital terms.

The 8-bit sequence is then sent in parallel (8 lines sending the bits all at the same time) to

an array of transistors. The transistors switch 8 lasers off and on to transmit the digitalsequences. A 1 turns a given laser on while a 0 turns it off. The laser light pulses are

sensed by eight phototransistors that are give off a 1 when excited by laser light and a0 when not excited.To reverse the process for output to the audio speaker, digital to analog conversion needs

to take place. To do this, the digital bits from the laser are fed into a latch (74HC161) that

sustains the digital values coming from the lasers until another value overwrites it. Aftergoing through an inverter array, the 8-bit signal arrives at the D/A converter chip. This

chip takes each 8-bit digital sample and converts it to one of the 256 voltage levels used

by the A/D chip. The output analog signal is then amplified by a variable gain opamp

circuit and taken to the speaker.


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Security System:-

Torch powered by 3V or above power-supply is used for generating a laser beam. A

combination of plain mirrors M1 through M6 is used to direct the laser beam around theobject that you want to protect . The laser beam is directed to finally fall on an LDR that

forms part of the receiver unit .Any interruption of the beam by a thief/ trespasser

(Hacker for data communication) will result into energisation of the alarm. The 3Vpower-supply circuit is a conventional full wave rectifier-filter circuit.

Any alarm unit that operates on 230V AC can be connected at the output. The

receiver unit comprises two identical step-down transformers (X1 and X2), two 6V relays(RL1 and RL2), an LDR, a transistor, and a few other passive components. When

switches S1 and S2 are activated, transformer X1, followed by a full-wave rectifier and

smoothing capacitor C1, drives relay RL1 through the laser switch. The laser beamshould be aimed continuously on LDR. As long as the laser beam falls on LDR, transistor

T1 remains forward biased and relay RL1 is thus in energized condition. When a person

crosses the line of laser beam, relay RL1 turns off and transformer X2 gets energized to

provide a parallel path across N/C contact and the pole of relay RL1. In this condition,the laser beam will have no effect on LDR and the alarm will continue to operate as long

as switch S2 is ON. When the torch is switched on, the pointed laser beam is reflected

from a definite point/place on the periphery of the any object. Making use of a set of

properly oriented mirrors one can form an visible net of laser rays as shown in the blockdiagram. The final ray should fall on LDR of the circuit.


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Note. LDR should be kept in a long pipe to protect it from other sources of light, and its

total distance from the source may be kept limited to 500 meters.

Laser:-

A laser is a device that emits light (electromagnetic radiation) through a process calledstimulated emission. The term laser is an acronym forlight amplification by stimulated

emission of radiation. Laser light is usually spatially coherent, which means that the

light either is emitted in a narrow, low-divergence beam, or can be converted into one

with the help of optical components such as lenses. Typically, lasers are thought of asemitting light with a narrow wavelengthspectrum ("monochromatic" light). This is not
http://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Electromagnetic_radiationhttp://en.wikipedia.org/wiki/Stimulated_emissionhttp://en.wikipedia.org/wiki/Acronymhttp://en.wikipedia.org/wiki/Coherence_(physics)http://en.wikipedia.org/wiki/Coherence_(physics)http://en.wikipedia.org/wiki/Beam_divergencehttp://en.wikipedia.org/wiki/Lenshttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Electromagnetic_spectrumhttp://en.wikipedia.org/wiki/Electromagnetic_radiationhttp://en.wikipedia.org/wiki/Stimulated_emissionhttp://en.wikipedia.org/wiki/Acronymhttp://en.wikipedia.org/wiki/Coherence_(physics)http://en.wikipedia.org/wiki/Beam_divergencehttp://en.wikipedia.org/wiki/Lenshttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Electromagnetic_spectrumhttp://en.wikipedia.org/wiki/Light


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true of all lasers, however: some emit light with a broad spectrum, while others emit light

at multiple distinct wavelengths simultaneously. The coherence of typical laser emissionis distinctive. Most other light sources emit incoherent light, which has aphase that varies

randomly with time and position.

Laser construction:-

A laser consists of a gain medium inside a highly reflectiveoptical cavity, as well as a

means to supply energy to the gain medium. The gain medium is a material withproperties that allow it to amplify light by stimulated emission. In its simplest form, a

cavity consists of two mirrors arranged such that light bounces back and forth, each time

passing through the gain medium. Typically one of the two mirrors, the output coupler, is

partially transparent. The output laser beam is emitted through this mirror.Light of a specific wavelength that passes through the gain medium is amplified

(increases in power); the surrounding mirrors ensure that most of the light makes manypasses through the gain medium, being amplified repeatedly. Part of the light that is

between the mirrors (that is, within the cavity) passes through the partially transparentmirror and escapes as abeam of light. .

The process of supplying the energyrequired for the amplification is calledpumping. Theenergy is typically supplied as an electrical current or as light at a different wavelength.

Such light may be provided by a flash lamp or perhaps another laser. Most practical

lasers contain additional elements that affect properties such as the wavelength of theemitted light and the shape of the beam.

Laser physics:-

A helium-neon laser demonstration . The glowing ray in the middle is an electric

discharge producing light in much the same way as a neon light. It is the gain mediumthrough which the laser passes, notthe laser beam itself, which is visible there. The laser

beam crosses the air and marks a red point on the screen to the right.
http://en.wikipedia.org/wiki/Phase_(waves)http://en.wikipedia.org/wiki/Laser_constructionhttp://en.wikipedia.org/wiki/Active_laser_mediumhttp://en.wikipedia.org/wiki/Optical_cavityhttp://en.wikipedia.org/wiki/Optical_cavityhttp://en.wikipedia.org/wiki/Output_couplerhttp://en.wikipedia.org/wiki/Optical_amplifierhttp://en.wikipedia.org/wiki/Optical_amplifierhttp://en.wikipedia.org/wiki/Light_beamhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Laser_pumpinghttp://en.wikipedia.org/wiki/Laser_pumpinghttp://en.wikipedia.org/wiki/Laser_pumpinghttp://en.wikipedia.org/wiki/Xenon_flash_lamphttp://en.wikipedia.org/wiki/Helium-neon_laserhttp://en.wikipedia.org/wiki/Active_laser_mediumhttp://en.wikipedia.org/wiki/Phase_(waves)http://en.wikipedia.org/wiki/Laser_constructionhttp://en.wikipedia.org/wiki/Active_laser_mediumhttp://en.wikipedia.org/wiki/Optical_cavityhttp://en.wikipedia.org/wiki/Output_couplerhttp://en.wikipedia.org/wiki/Optical_amplifierhttp://en.wikipedia.org/wiki/Light_beamhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Laser_pumpinghttp://en.wikipedia.org/wiki/Xenon_flash_lamphttp://en.wikipedia.org/wiki/Helium-neon_laserhttp://en.wikipedia.org/wiki/Active_laser_medium


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Spectrum of a helium neon laser showing the very high spectral purity intrinsic to nearly

all lasers. Compare with the relatively broad spectral emittance of a light emitting diode.See also: Laser science

The gain medium of a laser is a material of controlled purity, size, concentration, and

shape, which amplifies the beam by the process of stimulated emission. It can be of any

state: gas, liquid,solid orplasma. The gain medium absorbs pump energy, which raisessome electrons into higher-energy ("excited") quantum states. Particles can interact with

light both by absorbing photons or by emitting photons. Emission can be spontaneous or

stimulated. In the latter case, the photon is emitted in the same direction as the light thatis passing by. When the number of particles in one excited state exceeds the number of

particles in some lower-energy state,population inversion is achieved and the amount of

stimulated emission due to light that passes through is larger than the amount ofabsorption. Hence, the light is amplified. By itself, this makes an optical amplifier. When

an optical amplifier is placed inside a resonant optical cavity, one obtains a laser.

The light generated by stimulated emission is very similar to the input signal in terms of

wavelength, phase, and polarization. This gives laser light its characteristic coherence,and allows it to maintain the uniform polarization and often monochromaticity

established by the optical cavity design.

The optical cavity, a type ofcavity resonator, contains a coherent beam of light between

reflective surfaces so that the light passes through the gain medium more than oncebefore it is emitted from the output aperture or lost to diffraction or absorption. As light

circulates through the cavity, passing through the gain medium, if the gain (amplification)

in the medium is stronger than the resonator losses, the power of the circulating light canrise exponentially. But each stimulated emission event returns a particle from its excited

state to the ground state, reducing the capacity of the gain medium for further

amplification. When this effect becomes strong, the gain is said to be saturated. Thebalance of pump power against gain saturation and cavity losses produces an equilibriumvalue of the laser power inside the cavity; this equilibrium determines the operating point

of the laser. If the chosen pump power is too small, the gain is not sufficient to overcome

the resonator losses, and the laser will emit only very small light powers. The minimumpump power needed to begin laser action is called the lasing threshold. The gain medium

will amplify any photons passing through it, regardless of direction; but only the photons

aligned with the cavity manage to pass more than once through the medium and so havesignificant amplification.

The beam in the cavity and the output beam of the laser, if they occur in free space rather

than waveguides (as in an optical fiber laser), are, at best, low order Gaussian beams.However this is rarely the case with powerful lasers. If the beam is not a low-orderGaussian shape, the transverse modes of the beam can be described as a superposition of

Hermite-GaussianorLaguerre-Gaussian beams (for stable-cavity lasers). Unstable laser

resonators on the other hand, have been shown to produce fractal shaped beams. [5] Thebeam may be highly collimated, that is being parallel without diverging. However, a

perfectly collimated beam cannot be created, due to diffraction. The beam remains

collimated over a distance which varies with the square of the beam diameter, and

eventually diverges at an angle which varies inversely with the beam diameter. Thus, abeam generated by a small laboratory laser such as a helium-neon laserspreads to about

1.6 kilometers (1 mile) diameter if shone from the Earthto theMoon. By comparison, the
http://en.wikipedia.org/wiki/File:Red-YellowGreen-Blue_LED_spectra.pnghttp://en.wikipedia.org/wiki/Laser_sciencehttp://en.wikipedia.org/wiki/State_of_matterhttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Solidhttp://en.wikipedia.org/wiki/Plasma_(physics)http://en.wikipedia.org/wiki/Plasma_(physics)http://en.wikipedia.org/wiki/Excited_statehttp://en.wikipedia.org/wiki/Quantum_statehttp://en.wikipedia.org/wiki/Population_inversionhttp://en.wikipedia.org/wiki/Optical_amplifierhttp://en.wikipedia.org/wiki/Phase_(waves)http://en.wikipedia.org/wiki/Cavity_resonatorhttp://en.wikipedia.org/wiki/Exponential_growthhttp://en.wikipedia.org/wiki/Lasing_thresholdhttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Gaussian_beamhttp://en.wikipedia.org/wiki/Transverse_modehttp://en.wikipedia.org/wiki/Hermite_polynomialshttp://en.wikipedia.org/wiki/Gaussian_functionhttp://en.wikipedia.org/wiki/Gaussian_functionhttp://en.wikipedia.org/wiki/Laguerre_polynomialshttp://c/Documents%20and%20Settings/aaaaa/Desktop/015/New%20Folder/Laser.htm#cite_note-4#cite_note-4http://en.wikipedia.org/wiki/Collimated_lighthttp://en.wikipedia.org/wiki/Beam_divergencehttp://en.wikipedia.org/wiki/Beam_divergencehttp://en.wikipedia.org/wiki/Diffractionhttp://en.wikipedia.org/wiki/Helium-neon_laserhttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Moonhttp://en.wikipedia.org/wiki/Moonhttp://en.wikipedia.org/wiki/File:Red-YellowGreen-Blue_LED_spectra.pnghttp://en.wikipedia.org/wiki/Laser_sciencehttp://en.wikipedia.org/wiki/State_of_matterhttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Solidhttp://en.wikipedia.org/wiki/Plasma_(physics)http://en.wikipedia.org/wiki/Excited_statehttp://en.wikipedia.org/wiki/Quantum_statehttp://en.wikipedia.org/wiki/Population_inversionhttp://en.wikipedia.org/wiki/Optical_amplifierhttp://en.wikipedia.org/wiki/Phase_(waves)http://en.wikipedia.org/wiki/Cavity_resonatorhttp://en.wikipedia.org/wiki/Exponential_growthhttp://en.wikipedia.org/wiki/Lasing_thresholdhttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Gaussian_beamhttp://en.wikipedia.org/wiki/Transverse_modehttp://en.wikipedia.org/wiki/Hermite_polynomialshttp://en.wikipedia.org/wiki/Gaussian_functionhttp://en.wikipedia.org/wiki/Laguerre_polynomialshttp://c/Documents%20and%20Settings/aaaaa/Desktop/015/New%20Folder/Laser.htm#cite_note-4#cite_note-4http://en.wikipedia.org/wiki/Collimated_lighthttp://en.wikipedia.org/wiki/Beam_divergencehttp://en.wikipedia.org/wiki/Diffractionhttp://en.wikipedia.org/wiki/Helium-neon_laserhttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Moon


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output of a typical semiconductor laser, due to its small diameter, diverges almost as soon

as it leaves the aperture, at an angle of anything up to 50. However, such a divergentbeam can be transformed into a collimated beam by means of a lens. In contrast, the light

from non-laser light sources cannot be collimated by optics as well.

Although the laser phenomenon was discovered with the help ofquantum physics, it is

not essentially more quantum mechanical than other light sources. The operation of a freeelectron lasercan be explained without reference toquantum mechanics.

Spectral output of several types of lasers:-
http://en.wikipedia.org/wiki/Lens_(optics)http://en.wikipedia.org/wiki/Quantum_physicshttp://en.wikipedia.org/wiki/Free_electron_laserhttp://en.wikipedia.org/wiki/Free_electron_laserhttp://en.wikipedia.org/wiki/Free_electron_laserhttp://en.wikipedia.org/wiki/Quantum_mechanicshttp://en.wikipedia.org/wiki/Quantum_mechanicshttp://en.wikipedia.org/wiki/Quantum_mechanicshttp://en.wikipedia.org/wiki/Lens_(optics)http://en.wikipedia.org/wiki/Quantum_physicshttp://en.wikipedia.org/wiki/Free_electron_laserhttp://en.wikipedia.org/wiki/Free_electron_laserhttp://en.wikipedia.org/wiki/Quantum_mechanics


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Sensor:- A Photo detector is used for detection of the intensity modulated data.
http://en.wikipedia.org/wiki/File:Laser_spectral_lines.svg


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A sensor is a device which measures a physical quantity and converts it into a signalwhich can be read by an observer or by an instrument.

For example, a mercury thermometer converts the measured temperature into expansionand contraction of a liquid which can be read on a calibrated glass tube. A thermocouple

converts temperature to an output voltage which can be read by a voltmeter. For

accuracy, all sensors need to be calibrated against known standards.Sensors are used in everyday objects such as touch-sensitive elevator buttons and lamps

which dim or brighten by touching the base. There are also innumerable applications for

sensors of which most people are never aware. Applications include automobiles,machines, aerospace, medicine, industry, and robotics.

A sensor's sensitivity indicates how much the sensor's output changes when the measured

quantity changes. For instance, if the mercury in a thermometer moves 1cm when the

temperature changes by 1, the sensitivity is 1cm/1. Sensors that measure very smallchanges must have very high sensitivities.

Technological progress allows more and more sensors to be manufactured on a

microscopic scale as micro sensors using MEMS technology. In most cases, a microsensor reaches a significantly higher speed and sensitivity compared with macroscopic

approaches.

LDR:- It refers to light dependent resister. The resistence of LDR is increased in dark.It is used as a sensor of light.

PC Interfacing:-


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RS-232

In telecommunication RS-232 (Recommended Standard 232) is a standard for serialbinary data signals connecting between a DTE (Data terminal equipment) and a DCE(Data Circuit-terminating equipment). It is commonly used in computer serial ports. A

similarITU-T standard is V.24.

Standard details:

In RS-232, data is sent as a time-series of bits. Both synchronous and asynchronous

transmissions are supported by the standard. In addition to the data circuits, the standard

defines a number of control circuits used to manage the connection between the DTE and

DCE. Each data or control circuit only operates in one direction that is, signaling from aDTE to the attached DCE or the reverse. Since transmit data and receive data are separate

circuits, the interface can operate in a full duplex manner, supporting concurrent data

flow in both directions. The standard does not define character framing within the data

stream, or character encoding.

RS232 Data Interface


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RS-232 is simple, universal, well understood and supported but it has some serious

shortcomings as a data interface. The standards to 256kbps or less and line lengths of

15M (50 ft) or less but today we see high speed ports on our home PC running very highspeeds and with high quality cable maxim distance has increased greatly. The rule of

thumb for the length a data cable depends on speed of the data, quality of the cable.

Signals:-

Commonly-used signals are:


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I. Transmitted Data (TxD)Data sent from DTE to DCE.

II. Received Data (RxD)

Data sent from DCE to DTE.

III. Request To Send (RTS)Asserted (set to 0) by DTE to prepare DCE to receive data. This may require action onthe part of the DCE, e.g. transmitting a carrier or reversing the direction

IV. Clear To Send (CTS)Asserted by DCE to acknowledge RTS and allow DTE to transmit.

Data Terminal Ready (DTR) Asserted by DTE to indicate that it is ready to be connected.If the DCE is a modem, this may "wake up" the modem, bringing it out of a power saving

mode. This behaviour is seen quite often in modern PSTN and GSM modems. When this

signal is de-asserted, the modem may return to its standby mode, immediately hanging upany calls in progress.

V. Data Set Ready (DSR)Asserted by DCE to indicate an active connection. If DCE is not a modem (e.g. a null

modem cable or other equipment), this signal should be permanently asserted (set to 0),

possibly by a jumper to another signal.

VI. Data Carrier Detect (DCD)Asserted by DCE when a connection has been established with remote equipment.

VII. Ring Indicator (RI)Asserted by DCE when it detects a ring signal from the telephone line. The standard

defines RTS/CTS as the signaling protocol for flow control for data transmitted from

DTE to DCE. The standard has no provision for flow control in the other direction.

Various implementations of compatible ports may reassign other pins for flow control.

RTS/CTS handshaking


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The standard RS-232 use of the RTS and CTS lines is asymmetrical. The DTE asserts

RTS to indicate desire to transmit to the DCE. The DCE asserts CTS in response to grantpermission. This allows for half-duplex modems that disable their transmitters when not

required, and must transmit synchronization preamble to the receiver when they are re-

enabled. There is no way for the DTE to indicate that it is unable to accept data from theDCE.

A non-standard symmetrical alternative is widely used: CTS indicates permission fromthe DCE for theDTE to transmit, and RTS indicates permission from the DTE for theDCE to transmit. The "request to transmit" is implicit and continuous. Thus, with this

alternative usage, one can think of RTS asserted (logic 0) meaning "ready to receive

characters" from the DTE, rather than a "request to transmit" to the

DCE.

Signal rate selection

The DTE or DCE can specify use of a "high" or "low" signaling rate. The rates as well aswhich device will select the rate must be configured in both the DTE and DCE. The

prearranged device selects the high rate by setting pin 23 to ON.

Loopback testing

Many DCE devices have a loop back capability used for testing. When enabled, signals

are echoed back to the sender rather than being sent on to the receiver. If supported, the

DTE can signal the local DCE (the one it is connected to) to enter loop back mode by

setting pin 18 to ON, or the remote DCE (the one the local DCE is connected to) to enterloop back mode by setting pin 21 to ON. The latter tests the communications link as well

as both DCE's. When the DCE is in test mode it signals the DTE by setting Pin 25 toON.A commonly used version of loop back testing doesn't involve any special capability

of either end. A hardware loop back is simply a wire connecting complementary pins

together in the same connector. SeeLoopback.

Loopback testing is often performed with a specialized DTE called a Bit Error Rate

Tester (BERT).

Timing signals


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Some synchronous devices provide a clock signal to synchronize data transmission,

especially at higher data rates. Two timing signals are provided by the DCE on pins 15and 17. Pin 15 is the transmitter

Clock, or send timing (ST); the DTE puts the next bit on the data line (pin 2) when this

clock transitions OFF to ON (so it is stable during the ON to OFF transition when theDCE registers the bit). Pin 17

is the receiver clock, or receive timing (RT); the DTE reads the next bit from the data line(pin 3) when this clock transitions from ON to OFF.

Alternatively, the DTE can provide a clock signal, called transmitter timing (TT), on pin

24 for transmitted data. Again, data is changed when the clock transitions from OFF to

ON and read during theON to OFF transition. TT can be used to overcome the issue where ST must traverse a

cable of unknown length and delay, clock a bit out of the DTE after another unknown

delay, and return it to theDCE over the same unknown cable delay. Since the relationbetween the transmitted bit and TT can be fixed in the DTE design, and since both

signals traverse the same cable length, using TT eliminates the issue. TT may be

generated by looping ST back with an appropriate phase change to align it with thetransmitted data. ST loop back to TT lets the DTE use the DCE as the frequency

reference, and correct the clock to data timing.

RS232 physical properties

The RS232 standard describes a communication method capable of communicating in

different environments. This has had its impact on the maximum allowable voltages etc.

on the pins. In the original definition, the technical possibilities of that time were taken

into account. The maximum baud rate defined for example is 20 kbps. With currentdevices like the 16550A UART, maximum speeds of

1.5 Mbps are allowed.

IC Used :-For the security system comparator IC is required. we can use one of the given below


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Advantages :-

Two internally compensated op amps in a single package

Eliminates need for dual supplies

Allows directly sensing near GND and VOUT also goes to GND

Compatible with all forms of logic

Power drain suitable for battery operation

Pin-out same as LM1558/LM1458 dual operational amplifier

Circuit Diagram for Data Communication :-


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For Audio Transmission:-

Simple Transmitter:-

Simple Reciever:-

For Digital Data:-


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Transmitter Block Diagram:-

possible circuits for receiving:-

PCPOWERSUPPL

Y

AMPLIFIRESWITCHING

DEVICE

LASER


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Before trying the HBFR-2521 fiberoptical receiverr module I tried to use Simple infra-red detectoras the detector /that circuit was also sensitive to visible light). That circuit

did not give any useful results because it was too slow. I thought that using simple thistype prototransistor circuit were not usable in this application.

Good results up to 9600 bps using the following receiving circuit:

+5v

|| collector

| /---> |/ phototransistor

light |---> |\

| V emitter|_________________________ 0 and +5 out|/\ 1.5k/\

|gnd

The circuit it gives out 0 and 5 volts which is not compatible with RS232. The circuit

must be followed with MC1488 (or some other) rs232 driver to convert this to RS232. Ihave not tried this circuit, but the idea seems to be worth to try.

Security System Circuit Diagram:-
http://www.epanorama.net/counter.php?url=http://www.hut.fi/~then/circuits/irdetector.htmlhttp://www.epanorama.net/counter.php?url=http://www.hut.fi/~then/circuits/irdetector.htmlhttp://www.epanorama.net/counter.php?url=http://www.hut.fi/~then/circuits/irdetector.htmlhttp://www.epanorama.net/counter.php?url=http://www.hut.fi/~then/circuits/irdetector.html


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Here we will use a dark detector circuit.if the laser beam falls continuously on the LDR

so the buzzer will in OFF position. When the LASER beam is interrupted the buzzerreached in ON position.

we can use IC555 (timer IC) as a comparator.

Programming Language Used:-

Visual Basic


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HistoryMicrosoft released Visual Basic in 1987. It was the first visual development tool from

Microsoft, and it was to compete with C, C++, Pascal and other well-knownprogramming languages. From the start, Visual Basic wasn't a hit. It wasn't until release

2.0 in 1991 that people really discovered the potential of the language, and with release3.0 it had become the fastest-growing programming language on the market.

What Is Visual Basic?Programmers have undergone a major change in many years of programming variousmachines. For example what could be created in minutes with Visual Basic could take

days in other languages such: as "C" or "Pascal". Visual Basic provides many interesting

sets of tools to aid you in building exciting applications. Visual Basic provides these tools

to make your life far easier because all the real hard code is already written for you.With controls like these you can create many applications which use certain parts of

windows.

Visual Basic

Paradigm :- Event-driven

Developer :- Microsoft

Latest release :- VB6/ 1998

Typing discipline :- Static, strong

Influenced by :- Quick BASIC

Influenced :- Visual Basic.NET

OS :- Microsoft Windows

Visual Basic (VB) is a third-generation event driven programming language andassociated development environment from Microsoft for its COM programming model.

Visual Basic was derived from BASIC and enables the rapid application development(RAD) of graphical user interface (GUI) applications, access to databases using

DAO,RDO or ADO and creation ofActive X controls and objects. Scripting languagessuch as VBA and VB Script are syntactically similar to Visual Basic, but performdifferently.

A programmer can put together an application using the components provided with

Visual Basic itself.Programs written in Visual Basic can also use the Windows API, but doing so requires

external function declarations.In business programming, Visual Basic has one of the largest user bases. In a survey

conducted in 2005, 62 percent of developers reported using some form of Visual Basic. Itcurrently competes with C++, C# and Java for dominance in the business world. Java

Script is another competitor to Visual Basic.

The final release was version 6 in 1998. Microsoft extended support will end in 2008 andthe designated successor is Visual Basic .NET.

Areas of Application:


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The term "Personal Programming" refers to the idea that, wherever you work,whatever you do, you can expand your computer's usefulness by writing applications to

use in your own job. Personal Programming is what Visual Basic is all about. Using

Visual Basic's tools, you quickly translate an abstract idea into a program design you canactually see on the screen. VB encourages you to experiment, revise, correct, and

network your design until the new project meets your requirements. However , most ofall, it inspires your imagination and creativity.Visual Basic is ideal for developing applications that run in the new Windows 95

operating system. VB presents a 3-step approach for creating programs:

1. Design the appearance of your application.

2. Assign property settings to the objects of your program.

3. Write the code to direct specific tasks at runtime.

Visual Basic can used in a number of different areas, for example:

Education

Research

Medicine

Business

Commerce

Marketing and Sales

Accounting

Consulting

Law

References


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www.wikipedia.org

www.google.com

www.infomit.com www.engineeringproject.4u.com
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