shadow alarm

SHADOW ALARM A Mini project report Submitted in the partial fulfillment for the requirements for the award Bachelor of technology In Electronics and Communication Engineering By A.VAISHNAVI (09UP1A0401) K.ANU (09UP1A0421) P.SUSHMA (09UP1A0431)

Under the esteemed guidance of Ms. SARITHA Assistant Professor, ECE Dept.

Department of Electronics and Communication Engineering VIGNANS’ INSTITUTE OF MANAGEMENT AND TECHNOLOGY FOR WOMEN (Approved by A.I.C.T.E. and Affiliated to JNT University, Hyderabad)Kondapur (V), Ghatkesar (M), R.R. Dist – 501 301

VIGNANS’ INSTITUTE OF MANAGEMENT AND TECHNOLOGY FOR WOMEN (Approved by A.I.C.T.E. and Affiliated to JNT University, Hyderabad) Kondapur (V), Ghatkesar (M), R.R. Dist – 501 301

Department of Electronics and Communications Engineering

CERTIFICATE This is to certify that the mini project entitled “SHADOW ALARM” is a bonafide work done and submitted by A.VAISHNAVI, K.ANU and P.SUSHMA in partial fulfillment of requirement for the award of Bachelor of Technology degree in Electronics and Communication

Engineering,

Vignan’s

Institute

of

Management and Technology for Women, Ghatkesar.

Project Guide

Head of the

Department Ms. Saritha

Mrs.

Assistant Professor,

H.O.D,

Dept of E.C.E,

Dept of E.C.E,

VMTW, Ghatkesar.

VMTW, Ghatkesar External Examiner

ACKNOWLEDGEMENT The successful completion of the mini project though it was an arduous task it has been made by the help of many people we are placed to express our thanks to the people whose suggestions, comments, criticisms greatly encouraged us in the better of the mini project. We extend our sincere thanks to Mrs.M.PRAMEELA, Principal, Vignan’s Institute of Management and Technology for Women, Ghatkesar, for support in completion of this mini project. We extend our heartfelt thanks to Mrs.

, Head of the Dept, ECE, Vignan’s

Institute of Management and Technology for Women, Ghatkesar, for support in completion of this mini project. We take this opportunity to express our gratitude to our project guide Mrs.

, Asst.

Professor for her efficient guidance, support and encouragement throughout the mini project. We take privilege expressing our gratitude to all the staff of ECE department, VMTW, Ghatkesar, for their support and their suggestions.

DECLARATION

I here by declare that this Mini Project entitled “SHADOW ALARAM” submitted by us is our original project work. It does not form part of any previous project work , thesis or report to the college or any other college.

K.Anu (09UP1A0421)

A.Vaishnavi (09UP1A0401)

P.Sushma (09UP1A0431)

CONTENTS TOPIC

PAGE NO

CERTIFICATE ACKNOWLEDGEMENT DECLARATION ABSTRACT LIST OF FIGURES LIST OF TABLES CHAPTER 1. CIRCUIT DESCRIPTION 1.1 INTRODUCTION 1.2 CIRCUIT DIAGRAM 1.3 COMPONENTS LIST CHAPTER 2. IC PIN DESCRIPTION 2.1 IC 555 2.2 IC 741 2.3 IC UM66 CHAPTER 3. CIRCUIT ELEMENTS 3.1 RESISTORS 3.2 CAPACITORS 3.3 TRANSISTORS 3.4 LIGHT EMITTING DIODES 3.5 ZENER DIODE CHAPTER 4. ADVANTAGES CHAPTER 5.CONCLUSION AND FUTURE SCOPE CHAPTER 6.REFERENCES

ABSTRACT Our mini-project is to design and check the functionality of ‘SHADOW ALARM’ circuit. Shadow Alarm is opto-sensitive circuit that sounds an alarm whenever a shadow falls on it .Now a days it is widely used in aspects of security systems, where security is our main concern .So it can be used at night by shopkeepers to protect the valuables in their showrooms. It can also be used to provide security at warehouses (go-downs) where storage and protection of various types of goods is main concern, and works good for home-security too. A dim lighting in the room is necessary to detect the moving shadow. Unlike optointerruption alarms based on light-dependent resistors (LDRs), it does not require an aligned light beam to illuminate the photo-sensor.

1. CIRCUIT DESCRIPTION

1.1. INTRODUCTION This opto-sensitive circuit sounds an alarm whenever a shadow falls on it. So it can be used at night by shopkeepers to protect the valuables in their showrooms. A dim light in the room is necessary to detect the moving shadow. Unlike opto interruption alarms based on lightdependent resistors (LDRs), it does not require an aligned light beam to illuminate the photosensor. The circuit is powered by a 9V PP3 battery and uses the most sensitive photo-sensor L14F1 to detect shadows. It is portable and can be used at any place that is to be monitored. Op-amp μA741 (IC1) is used as a voltage comparator. Its inverting input is biased by the voltage obtained from the junction of 100k resistor R1 and the collector of phototransistor T1. The non-inverting input of IC1 gets a controlled voltage from potential divider R2 and VR1. In the presence of ambient light, the phototransistor conducts and the inverting input (pin 2) of IC1 gets a lower voltage than its non-inverting input (pin 3). This makes the output of IC1 high, which is indicated by the glowing of LED1. When a shadow falls on the photo sensor, the output of IC1 goes low. This low pulse triggers the monostable (IC2) designed for a delay of 51 seconds using R6 and C3. The output of IC2 is used to light up LED2 and activate the alarm. Slide switch S2 is used to select either the buzzer or siren. When it is towards left the buzzer beeps, and when it is towards right IC UM66 (IC3) activates to give a loud alarm simulating a police siren. Resistor R8 and zener diode ZD1 provide 3.1V DC to IC UM66.

1.3. COMPONENTS LIST: 1. IC’s 1. IC1 741

1No

2. IC2 NE555

1No

3. IC3 UM66

1No

2. TRANSISTORS 1. T1 L14F1

1No

2. T2 BC548

1No

3. RESISTORS 1. 10

2 No’s

2. 100K

1No

3. 4.7K

1No

4. 100 Ohm

1No

5. 680 Ohm

1No

6. 47 Ohm

1No

7. 1 Mega Ohms

1No

8. 220 K

1No

9. 1 K

1No

4. CAPACITORS 1. 10UF

1No

2. 0.01UF

1No

3. 47UF 5. PRESET

47K

1No

6. LED

2No’S

7. ZENER DIODE 3.1V

1No

8. SPEAKER

1No

8Ohms/0.5w

2. IC PIN DESCRIPTION 2.1 IC NE555 PIN DIAGRAM The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element .It is easy to use, available at low price and has high stability.

PIN DIAGRAM

Pinout diagram The connection of the pins for a DIP package is as follows: Pin Name 1 2 3 4 5 6 7 8

GND

Purpose

Ground reference voltage, low level (0 V) The OUT pin goes high and a timing interval starts when this input falls below TRIG 1/2 of CTRL voltage (which is typically 1/3 of VCC, when CTRL is open). OUT This output is driven to approximately 1.7V below +VCC or GND. A timing interval may be reset by driving this input to GND, but the timing does RESET not begin again until RESET rises above approximately 0.7 volts. Overrides TRIG which overrides THR. CTRL Provides "control" access to the internal voltage divider (by default, 2/3 VCC). The timing (OUT high) interval ends when the voltage at THR is greater than THR that at CTRL. Open collector output which may discharge a capacitor between intervals. In DIS phase with output. Positive supply voltage, which is usually between 3 and 15 V depending on the VCC variation.

MODES OF OPERATION The 555 has three operating modes: •

Monostable mode: in this mode, the 555 functions as a "one-shot" pulse generator. Applications include timers, missing pulse detection, bounce free switches, touch switches, frequency divider, capacitance measurement, pulse-width modulation (PWM) and so on.

•

Astable mode: free running mode: the 555 can operate as an oscillator. Uses include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse position modulation and so on. The 555 can be used as a simple ADC, converting an analog value to a pulse length. E.g. selecting a thermistor as timing resistor allows the use of the 555 in a temperature sensor: the period of the output pulse is determined by the temperature. The use of a microprocessor based circuit can then convert the pulse period to temperature, linearize it and even provide calibration means.

•

Bistable mode or Schmitt trigger: the 555 can operate as a flip-flop, if the DIS pin is not connected and no capacitor is used. Uses include bounce-free latched switches.

MONOSTABLE OPERATION

Schematic of a 555 in monostable mode

The relationships of the trigger signal, the voltage on C and the pulse width in monostable mode In the monostable mode, the 555 timer acts as a "one-shot" pulse generator. The pulse begins when the 555 timer receives a signal at the trigger input that falls below a third of the voltage supply. The width of the output pulse is determined by the time constant of an RC network, which consists of a capacitor (C) and a resistor (R). The output pulse ends when the voltage on the capacitor equals 2/3 of the supply voltage. The output pulse width can be lengthened or shortened to the need of the specific application by adjusting the values of R and C.

The output pulse width of time t, which is the time it takes to charge C to 2/3 of the supply voltage, is given by

Where t is in seconds, R is in ohms and C is in farads. While using the timer IC in monostable mode, the main disadvantage is that the time span between any two triggering pulses must be greater than the RC time constant.

APPLICATIONS MONOSTABLE MODE •

Linear Ramp Generator

•

Pulse Width Modulator

•

Pulse Stretching

•

Frequency Divider

ASTABLE MODE •

Pulse Position Modulator

•

Square Wave Oscillator

2.2 IC 741 DESCRIPTION:

The Operational Amplifier is probably the most versatile Integrated Circuit available. It is very cheap especially keeping in mind the fact that it contains several hundred components. The most common Op-Amp is the 741 and it is used in many circuits. The OP AMP is a ‘Linear Amplifier’ with an amazing variety of uses. Its main purpose is to amplify (increase) a weak signal - a little like a Darlington Pair. The OP-AMP has two inputs, INVERTING ( - ) and NON-INVERTING (+), and one output at pin 6. The 741 is used in two ways. 1. An inverting amplifier. Leg two is the input and the output is always reversed. In an inverting amplifier the voltage enters the 741 chip through leg two and comes out of the 741 chip at leg six. If the polarity is positive going into the chip, it negative by the time it comes out through leg six. The polarity has been ‘inverted’ 2. A non-inverting amplifier. Leg three is the input and the output is not reversed. In a noninverting amplifier the voltage enters the 741 chip through leg three and leaves the 741 chip through leg six. This time if it is positive going into the 741 then it is still positive coming out. Polarity remains the same.

FEATURES: • Short Circuit Protection • Excellent Temperature Stability • Internal Frequency Compensation • High Input Voltage Range • Null of Offset

PIN DIAGRAM:

CONNECTION DIAGRAM:

2.3 IC UM66 DESCRIPTION:

UM66 is a melody integrated circuit. It is designed for use in bells, telephones, toys etc. It has an inbuilt tone and a beat generator. The tone generator is a programmed divider which produces certain frequencies. These frequencies are a factor of the oscillator frequency. The beat generator is also a programmed divider which contains 15 available beats. Four beats of these can be selected. There is an inbuilt oscillator circuit that serves as a time base for beat and tone generator. It has a 62 notes ROM to play music. A set of 4 bits controls the scale code while 2 bits control the rhythm code. When power is turned on, the melody generator is reset and melody begins from the first note. The speaker can be driven by an external npn transistor connected to the output of UM66.

PIN DIAGRAM:

PIN DESCRIPTION: Pin No

Function

Name

1

Melody output

Output

2

Supply voltage (1.5V - 4.5V)

Vcc

3

Ground (0V)

Ground

Zener diode rated 3.3V maintains the required 3.3V for UM66 IC. The output from Vo of UM66 is amplified by BC547 or BC548 transistor. .MELODY GENERATOR CIRCUIT:

Description Here is a simple melody generator circuit you can make using an IC. The UM66 series are CMOS IC’s designed for using in calling bell, phone and toys. It has a built in ROM programmed for playing music. The device has very low power consumption. Thanks for the CMOS technology. The melody will be available at pin3 of UM66 and here it is amplified by using Q1 to drive the speaker. Resistor R1 limits the base current of Q1 within the safe values. Capacitor C1 is meant for noise suppression. Notes •

Power supply must be between 1.5V & 4.5V .Do not exceed 4.5 V.

•

Speaker can be driven with external NPN transistor.

•

Melody begins from the first note if power is reseted.

•

Assemble the circuit on a good quality common board.

•

If transistor HE8050S is not available use any NPN transistor like BC548 or 2N2222.

3. PASSIVE ELEMENTS 3.1 RESISTORS Resistors (R), are the most commonly used of all electronic components, to the point where they are almost taken for granted. They are "Passive Devices", that is they contain no source of power or amplification but only attenuate or reduce the voltage signal passing through them. When used in DC circuits the voltage drop produced is measured across their terminals as the circuit current flows through them while in AC circuits the voltage and current are both in-phase producing 0o phase shift.

In all Electrical and Electronic circuit diagrams and schematics, the most commonly used resistor symbol is that of a "zig-zag" type line with the value of its resistance given in Ohms, Ω. RESISTOR SYMBOL The symbol used in schematic and electrical drawings for a Resistor can either be a "zigzag" type line or a rectangular box. RESISTOR TYPES All modern resistors can be classified into four broad groups; •

Carbon Composition Resistor - Made of carbon dust or graphite paste, low wattage

values •

Film or Cermet Resistor - Made from conductive metal oxide paste, very low

wattage values •

Wire-Wound Resistors. - Metallic bodies for heat sink mounting, very high wattage

ratings •

Semiconductor Resistors - High frequency/precision surface mount thin film

technology RESISTOR COLOUR CODE The resistance value, tolerance, and watt rating of the resistor are generally printed onto the body of the resistor as numbers or letters when the resistor is big enough to read the print, such as large power resistors. When resistors are small such as 1/4W Carbon and Film types, these specifications must be shown in some other manner as the print would be too small to read. So to overcome this, small resistors use coloured painted bands to indicate both their resistive value and their tolerance with the physical size of the resistor indicating its wattage rating. These coloured painted bands are generally known as a Resistors Colour Code.

The Standard Resistor Colour Code Chart.

The Resistor Colour Code Table.

Colour

Digit

Multiplier

Black

0

1

Brown

1

10

± 1%

Red

2

100

± 2%

Orange

3

1K

Yellow

4

10K

Green

5

100K

± 0.5%

Blue

6

1M

± 0.25%

Violet

7

10M

± 0.1%

Grey

8

White

9

Gold

0.1

± 5%

Silver

0.01

± 10%

None

Tolerance

± 20%

VARIABLE RESISTORS CONSTRUCTION Variable resistors consist of a resistance track with connections at both ends and a wiper which moves along the track as you turn the spindle. The track may be made from carbon, cermet (ceramic and metal mixture) or a coil of wire (for low resistances). The track is usually rotary but straight track versions, usually called sliders, are also available.

Variable resistors may be used as a rheostat with two connections (the wiper and just one end of the track) or as a potentiometer with all three connections in use. Miniature versions called presets are made for setting up circuits which will not require further adjustment. Variable resistors are often called potentiometers in books and catalogues. They are specified by their maximum resistance, linear or logarithmic track, and their physical size. The standard spindle diameter is 6mm. RHEOSTAT This is the simplest way of using a variable resistor. Two terminals are used: one connected to an end of the track, the other to the moveable wiper. Turning the spindle changes the

Rheostat

Symbol

resistance between the two terminals from zero up to the maximum resistance. PRESETS These are miniature versions of the standard variable resistor. They are designed to be mounted directly onto the circuit board and adjusted only when the circuit is built. A small screwdriver or similar tool is required to adjust presets. Presets are much cheaper than standard variable resistors so they are sometimes used in projects where a standard variable resistor would normally be used. Multitier presets are used where very

precise adjustments must be made. The screw must be turned many times (10+) to move the slider from one end of the track to the other, giving very fine control.

PRESET(OPEN STYLE)

MULTITURN PRESET

PRESET(CLOSED STYLE)

3.2 CAPACITORS INTRODUCTION Just like the Resistor, the Capacitor or sometimes referred to as a Condenser is a passive device, and one which stores energy in the form of an electrostatic field which produces a potential (Static Voltage) across its plates. When a voltage is applied to these plates, a current flows charging up the plates with electrons giving one plate a positive charge and the other plate an equal and opposite negative charge. This flow of electrons to the plates is known as the Charging Current and continues to flow until the voltage across the plates (and hence the capacitor) is equal to the applied voltage Vc. At this point the capacitor is said to be fully charged and this is illustrated below.

Capacitor Construction

Q=CxV UNITS OF CAPACITANCE • • •

Microfarad (μF) 1μF = 1/1,000,000 = 0.000001 = 10-6 F Nanofarad (nF) 1nF = 1/1,000,000,000 = 0.000000001 = 10-9 F Picofarad (pF) 1pF = 1/1,000,000,000,000 = 0.000000000001 = 10-12 F

TYPES OF CAPACITORS There are a very large variety of different types of Capacitors available in the market place and each one has its own set of characteristics and applications from small delicate trimming capacitors up to large power metal can type capacitors used in high voltage power correction and smoothing circuits. 1. DIELECTRIC Dielectric Capacitors are usually of the variable type such as used for tuning transmitters, receivers and transistor radios. They have a set of fixed plates and a set of moving plates that mesh with the fixed plates and the position of the moving plates with respect to the fixed plates determines the overall capacitance. The capacitance is generally at maximum when the plates are fully meshed. Variable Capacitor Symbols

As well as the continuously variable types, preset types are also available called Trimmers. These are generally small devices that can be adjusted or "pre-set" to a particular capacitance with the aid of a screwdriver and are available in very small capacitances of 100pF or less and are non-polarized. 2. FILM CAPACITORS Film Capacitors are the most commonly available of all types of capacitors, consisting of a relatively large family of capacitors with the difference being in their dielectric properties. These include polyester (Mylar), polystyrene, polypropylene, polycarbonate, metalized paper, teflon etc. Film type capacitors are available in capacitance ranges from 5pF to 100uF depending upon the actual type of capacitor and its voltage rating. Film capacitors also come in an assortment of shapes and case styles which include: •

Wrap & Fill (Oval & Round)

•

Epoxy Case (Rectangular & Round)

•

Metal Hermetically Sealed (Rectangular & Round)

3. CERAMIC CAPACITORS Ceramic Capacitors or Disc Capacitors as they are generally called, are made by coating two sides of a small porcelain or ceramic disc with silver and are then stacked together to make a capacitor. For very low capacitance values a single ceramic disc of about 3-6mm is used. Ceramic capacitors have a high dielectric constant (High-K) and are available so that relatively high capacitances can be obtained in a small physical size. They exhibit large nonlinear changes in capacitance against temperature and as a result are used as de-coupling or by-pass capacitors as they are also non-polarized devices. Ceramic capacitors have values ranging from a few picofarads to one or two microfarads but their voltage ratings are generally quite low. Ceramic types of capacitors generally have a 3-digit code printed onto their body to identify their capacitance value. For example, 103 would indicate 10 x 103 PF 4. ELECTROLYTIC CAPACITORS Electrolytic Capacitors are generally used when very large capacitance values are required. Here instead of using a very thin metallic film layer for one of the electrodes, a semi-liquid electrolyte solution in the form of a jelly or paste is used which serves as the second electrode (usually the cathode). The dielectric is a very thin layer of oxide which is grown electrochemically in production with the thickness of the film being less than ten microns. This insulating layer is so thin that it is possible to make large value capacitors of a small size. The majority of electrolytic types of capacitors are polarized, that is the voltage applied to the capacitor terminals must be of the correct polarity as an incorrect polarization will break down the insulating oxide layer and permanent damage may result. Electrolytic Capacitors are generally used in DC power supply circuits to help reduce the ripple voltage or for coupling and decoupling applications. Electrolytic's generally come in two basic forms; Aluminum Electrolytic and Tantalum Electrolytic capacitors.

3.3.TRANSISTOR

A transistor is a semiconductor device used to amplify and switch electronic signals. It is made of a solid piece of semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be much more than the controlling (input) power, the transistor provides amplification of a signal. Some transistors are packaged individually but many more are found embedded in integrated circuits.

PIN CONFIGURATION:-

L14F1

TRANSISTOR CHARACTERSTICS

ADVANTAGES The key advantages that have allowed transistors to replace their vacuum tube predecessors in most applications are •

Small size and minimal weight, allowing the development of miniaturized electronic devices.

•

Highly automated manufacturing processes, resulting in low per-unit cost.

•

Lower possible operating voltages, making transistors suitable for small, batterypowered applications.

•

Lower power dissipation and generally greater energy efficiency.

•

Higher reliability and greater physical ruggedness.

•

Extremely long life. Some transistorized devices have been in service for more than 30 years.

LIMITATIONS •

Silicon transistors do not operate at voltages higher than about 1,000 volts SiC devices can be operated as high as 3,000 volts). In contrast, electron tubes have been developed that can be operated at tens of thousands of volts.

•

High power, high frequency operation, such as that used in over-the-air television broadcasting, is better achieved in electron tubes due to improved electron mobility in a vacuum.

•

Silicon transistors are much more sensitive than electron tubes to an electromagnetic pulse, such as generated by an atmospheric nuclear explosion.

3.4.LIGHT EMITTING DIODES: A light-emitting diode (LED) is a semiconductor light source. The LED is based on the semiconductor diode. When a diode is forward biased (switched on), electrons are able to recombine with holes within the device, releasing energy in the form of photons. This effect is called electroluminescence and the color of the light (corresponding to the energy of the photon) is determined by the energy gap of the semiconductor.

In a diode formed from a direct band-gap semiconductor, such as gallium arsenide, carriers that cross the junction emit photons when they recombine with the majority carrier on the other side. Depending on the material, wavelengths (or colors) from the infrared to the near ultraviolet may be produced. The forward potential of these diodes depends on the wavelength of the emitted photons: 1.2 V corresponds to red, 2.4 V to violet. The first LEDs were red and yellow, and higher-frequency diodes have been developed over time. All LEDs produce incoherent, narrow-spectrum light; “white” LEDs are actually combinations of three LEDs of a different color, or a blue LED with a yellow scintillator coating. LEDs can also be used as low-efficiency photodiodes in signal applications. An LED may be paired with a photodiode or phototransistor in the same package, to form an opto-isolator.

Like a normal diode, the LED consists of a chip of semiconducting material doped with impurities to create a p-n junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side, or cathode, but not in the reverse direction. Charge-carriers—electrons and holes—flow into the junction from electrodes with different voltages. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon. The wavelength of the light emitted, and therefore its color, depends on the band gap energy of the materials forming the p-n junction. In silicon or germanium diodes, the electrons and holes recombine by a non-radiativetransition which produces no optical emission, because these are indirect band gap materials. The materials used for the LED have a direct band gap with energies corresponding to near-infrared, visible or near-ultraviolet light.

Colors and Materials: Color

Wavelength (nm)

Voltage (V)

Semiconductor Material

Infrared

Gallium arsenide (GaAs) Aluminium gallium arsenide (AlGaAs)

λ > 760

ΔV < 1.9

610 < λ < 760

Aluminium gallium arsenide (AlGaAs) Gallium arsenide phosphide (GaAsP) 1.63 < ΔV < Aluminium gallium indium phosphide 2.03 (AlGaInP) Gallium(III) phosphide (GaP)

590 < λ < 610

Gallium arsenide phosphide (GaAsP) 2.03 < ΔV < Aluminium gallium indium phosphide 2.10 (AlGaInP) Gallium(III) phosphide (GaP)

570 < λ < 590

Gallium arsenide phosphide (GaAsP) 2.10 < ΔV < Aluminium gallium indium phosphide 2.18 (AlGaInP) Gallium(III) phosphide (GaP)

500 < λ < 570

Indium gallium nitride (InGaN) / Gallium(III) nitride (GaN) [37] 1.9 < ΔV < Gallium(III) phosphide (GaP) 4.0 Aluminium gallium indium phosphide (AlGaInP) Aluminium gallium phosphide (AlGaP)

Blue

450 < λ < 500

Zinc selenide (ZnSe) Indium gallium nitride (InGaN) 2.48 < ΔV < Silicon carbide (SiC) as substrate 3.7 Silicon (Si) as substrate — (under development)

Violet

400 < λ < 450

2.76 < ΔV < Indium gallium nitride (InGaN) 4.0

Purple

Dual blue/red LEDs, 2.48 < ΔV < multiple types blue with red phosphor, 3.7 or white with purple plastic

Red

Orange

Yellow

Green

Ultraviolet λ < 400

White

3.1 < ΔV < 4.4

Broad spectrum ΔV = 3.5

Diamond (235 nm)[38] Boron nitride (215 nm)[39][40] Aluminium nitride (AlN) (210 nm)[41] Aluminium gallium nitride (AlGaN) Aluminium gallium indium nitride (AlGaInN) — (down to 210 nm)[42] Blue/UV diode with yellow phosphor

ADVANTAGES •

Efficiency

•

Size

•

On/Off time

•

Cycling

•

Dimming

•

Cool light

•

Slow failure

•

Lifetime

DISADVANTAGES •

High initial price

•

Temperature dependence

•

Voltage sensitivity

•

Light quality.

•

Area light source

•

Blue Blue pollution

APPLICATIONS Application of LEDs falls into four major categories: •

Visual signal application where the light goes more or less directly from the LED to the human eye, to convey a message or meaning.

•

Illumination where LED light is reflected from object to give visual response of these objects.

•

Generate light for measuring and interacting with processes that do not involve the human visual system.

•

Narrow band light sensors where the LED is operated in a reverse-bias mode and is responsive to incident light instead of emitting light.

3.5.ZENER DIODES: Zener diode is a type of diode that permits current not only in the forward direction like a normal diode, but also in the reverse direction if the voltage is larger than the breakdown voltage known as "Zener knee voltage" or "Zener voltage". A conventional solid-state diode will not allow significant current if it is reverse-biased below its reverse breakdown voltage. When the reverse bias breakdown voltage is exceeded, a conventional diode is subject to high current due to avalanche breakdown. Unless this current is limited by circuitry, the diode will be permanently damaged. In case of large forward bias (current in the direction of the arrow), the diode exhibits a voltage drop due to its junction built-in voltage and internal resistance. The amount of the voltage drop depends on the semiconductor material and the doping concentrations. A Zener diode exhibits almost the same properties, except the device is specially designed so as to have a greatly reduced breakdown voltage, the so-called Zener voltage. By contrast with the conventional device, a reverse-biased Zener diode will exhibit a controlled breakdown and allow the current to keep the voltage across the Zener diode at the Zener voltage. The Zener diode is therefore ideal for applications such as the generation of a reference voltage (e.g. for an amplifier stage), or as a voltage stabilizer for low-current applications.

The Zener diode's operation depends on the heavy doping of its p-n junction allowing electrons to tunnel from the valence band of the p-type material to the conduction band of the n-type material. In the atomic scale, this tunneling corresponds to the transport of valence band electrons into the empty conduction band states; as a result of the reduced barrier between these bands and high electric fields that are induced due to the relatively high levels of dopings on both sides. The breakdown voltage can be controlled quite accurately in the doping process. While tolerances within 0.05% are available, the most widely used tolerances are 5% and 10%. Breakdown voltage for commonly available zener diodes can vary widely from 1.2 volts to 200 volts.

4.ADVANTAGES AND APPLICAIONS ADVANTAGES

1. It is easy to understand that a security alarm system provides peace of mind when you are away from the business. 2. The main advantage of this circuit is that unike opto interruption alarm based on light dependent resistors (LDRs), it does not require an aligned beam to illuminate the photo sensor. 3. It is portable and can be used at any place that is to be monitored. 4. This circuit is easy to implement and all the components used in the circuit are economical. 5. We can reduce man work

APPLICATIONS 1. It can be used at night by shopkeepers to protect the valuables in their showrooms 2. It can be used to provide security at warehouses where storage and protection of various types of goods is main concern. 3. This circuit can also be used for home securities too.

5.CONCLUSION&FUTURE SCOPE CONCLUSION The circuit has found to have greater applications in security reliable and les expensive and is guaranteed o perform the best of the duration of their life time.

This project is accessible to anyone with an average expense

FUTURE SCOPE This circuit can be the front end of optical communication, voice transmission, alarm systems, remote controls etc.

6. REFERENCES  www.electronicsforyou.com  www.howstuffworks.com  www.wikipedia.org

 www.circuits-today.com  www.freedatasheets.com