electronic cardlock system

7/30/2019 Electronic Cardlock System

1/55

1

1.INTRODUCTION

The present inventions relates to an electronic locking system that can

be easily installed and achieves a security level not possible in traditional mechanical locking

systems. It is well known facts that mechanical locks, such the pin tumbler block, dead bolt

and side bar lock have security disadvantages in that these locks can be opened by

unauthorized persons who have some expertise in this field.

In an Electronic card lock system, a lock, a card slot for said lock, an electronic card

made of insulating material injected into the mechanism. This drives the particular

application. For particular application certain card has to be used. This project is a simple

version of card lock system where the advanced versions of this may lead to vast applications

in modern technological world.

The important components in this project are Infra red Leds, Photo Diodes and

relays. Where optical sensors make sensing of rays. Where octal buffers and relay drivers are

also used to store some data and to drive relays respectively. Here we used leds as the

output agents where the output observed by various ordinary leds.


2/55

2

2.CIRCUIT DIAGRAM

Figure 2.1: Circuit diagram


3/55

3

3.LIST OF COMPONENTS

NAME OF COMPONENT QUANTITY

Resistors:

100-ohm : 5 10k-ohm : 3Capacitors:

1000uf : 1 470uf : 1Diodes:

IN4007 : 3 Photo diodes : 4LEDs:

Red led [1-3] : 3 IR Leds : 3TRANSISTORs:

BC548 : 1ICs: 74LS244 : 1 ULN2003 : 1 7805 : 1 UM66 : 1Miscellaneous:

Ic base 20 pin : 1 Ic base 16 pin : 1 Relays (12v DC) : 3Push to on switch:

Transformer (12-0-12v) : 1 Insulating cards : 3


4/55

4

4.COMPONENTS DESCRIPTION

4.1 RESISTOR:

The resistor is the most common and well-known of the passive electrical

components. A resistor resists or limits the flow of electric current in a circuit. There are

many uses for resistors: they are used to drop voltage, limit current, attenuate signals, act as

heaters, act as fuses, furnish electrical loads and divide voltages.

Symbol of resistor:

Figure 4.1:symbol of resistor

Units of resistor: ohm

Resistors limit current. In a typical application, a resistor is connected in series with an LED:Types of resistors:

Figure 4.2:Types of Resistors

Fixed resistors: A fixed resistor is one in which the value of its resistance cannot change.


5/55

5

Variable resistors: A variable resistor is a resistor whose value can be adjusted by turning ashaft or sliding a control. They are also called potentiometers or rheostats and allow the

resistance of the device to be altered by hand.

Non-Linear resistors: A non-linear resistor is a resistor that has resistances that varysignificantly with applied voltage, temperature or light.

Types of non-linear resistors are varistors, thermistors and photo resistors.Color coding of resistors:

Resistors are coded to indicate the resistance value and tolerance. Carbon-composition and

carbon film resistors are too small to have the resistance value printed on their housings.

Therefore, bands of color are used to represent the resistance value.

Figure 4.3: Color coding of Resistors

The first and second band represents the numerical value of the resistor, and the color

of the third band specifies the power-of-ten multiplier. The color bands are always read from

left to right starting with the side that has a band closer to the edge.

Tolerance:

For carbon-composition and carbon film resistors, the common tolerances are 5%,

10%, and 20%, indicating that the actual value of the resistor can vary from the nominal

value by 5%, 10% and 20%. If the band is gold, it specifies a 5% tolerance; silver

specifies a 10% tolerance; if no band is present, the tolerance is 20%. Note that the color-

code system for capacitors is very similar to that of resistors except there is a fifth band

representing the temperature coefficient. This band is the first one closest to one end of the

capacitor. The other four fall into the same order as mentioned for resistors. In this case, the

second, third, and fourth bands are used to determine the capacitance. The fifth band


6/55

6

represents the tolerance of the capacitor. The table below shows the color code and their

associated value:

Resistor Symbols

Resistor schematic symbols of electrical & electronic circuit diagram - resistor,

potentiometer, and variable resistor.

Table of resistor symbols:

Resistor (IEEE)Resistor reduces the current flow.

Resistor (IEC)

Potentiometer (IEEE)

Adjustable resistor - has 3 terminals.

Potentiometer (IEC)

Variable Resistor /

Rheostat (IEEE) Adjustable resistor - has 2 terminals.

Variable Resistor /

Rheostat (IEC)

Trimmer Resistor Preset resistor

ThermistorThermal resistor - change resistance when

temperature changes

Photo resistor / Light Changes resistance according to light


7/55

7

dependent resistor

(LDR)

4.2 CAPACITORS:

A capacitor is a passive electronic component that stores energy in the form of an

electrostatic field. In its simplest form, a capacitor consists of two conducting plates

separated by an insulating material called the dielectric. The capacitance is directly

proportional to the surface areas of the plates, and is inversely proportional to the separation

between the plates. Capacitance also depends on the dielectric constant of the substance

separating the plates.

The standard unit of capacitance is the farad, abbreviated.

This is a large unit; more common units are the microfarad, abbreviated F (1 F =10-6

F) and

the picofarad, abbreviated pF (1 pF = 10-12

F).

Capacitors can be fabricated onto integrated circuit (IC) chips. They are

commonly used in conjunction with transistors in dynamic random access memory (DRAM).

The capacitors help maintain the contents of memory. Because of their tiny physical size,

these components have low capacitance. They must be recharged thousands of times per

second or the DRAM will lose its data.

Symbol of capacitor:

Figure 4.4:symbol of capacitor
http://whatis.techtarget.com/definition/0,,sid9_gci815498,00.htmlhttp://whatis.techtarget.com/definition/0,,sid9_gci812011,00.htmlhttp://searchcio-midmarket.techtarget.com/sDefinition/0,,sid183_gci213503,00.htmlhttp://searchcio-midmarket.techtarget.com/sDefinition/0,,sid183_gci213503,00.htmlhttp://whatis.techtarget.com/definition/0,,sid9_gci812011,00.htmlhttp://whatis.techtarget.com/definition/0,,sid9_gci815498,00.html


8/55

8

Characteristics: In its most elementary state a capacitor consists of two metal plates

separated by a certain distance d, in between the plates lies a dielectric material with

dielectric constant = o, where o is the dielectric of air.The dielectric material allows for

charge to accumulate between the capacitor plates. Air (Actually vacuum) has the lowest

dielectric value ofo = 8.854 * 10-12

Farads/meter where the Farad is the unit for

capacitance. All other materials have higher dielectric values, since they are higher in density

and can therefore accumulate more charge.

Capacitance is defined to be the amount of charge Q stored in between the two plates

for a potential difference or voltage V existing across the plates. In other words:

The capacitance C is given by C = Q/V (electrical definition)

The Physical meaning of capacitance can be seen by relating it to the physical

characteristics of the two plates, so that, the capacitance is related to the dielectric of the

material in between the plates, the square area of a plate and the distance between the plates

by the formula: C = o A/d

Clearly, the larger the area of the plate the more charge can be accumulated and hence

the larger the capacitance. Also, note that as the distance d increases the Capacitance

decreases since the charge cannot be contained as 'densely' as before. Both definitions of

Capacitance are compatible, although for our purposes we will be referring mostly to the

electrical definition.


9/55

9

Types of Capacitors:

The simple two-plate capacitor model falls short in representing all capacitors since

we have different types such as: ceramic disc capacitors, electrolytic capacitors, polyester

capacitors, tantalum capacitors and surface mount capacitors. Each type is selected according

to several criteria, essentially: the maximum voltage the capacitor can hold the value of the

dielectric, dimensions and tolerance ratings.

Figure 4.5: Types of Capacitors

Polyester Film Capacitor: Polyester film capacitors are used where cost is a consideration

as they do not offer a high tolerance. Many polyester film capacitors have a tolerance of 5%

or 10%, which is adequate for many applications. They are generally only available as leaded

electronics components.

Electrolytic capacitor: Electrolytic capacitors are a type of capacitor that is polarized. They

are able to offer high capacitance values - typically above 1F, and are most widely used for

low frequency applications - power supplies, decoupling and audio coupling applications as

they have a frequency limit if around 100 kHz.

Surface mount:SMD capacitors are used in vast quantities. After SMD resistors they are the

most widely used type of component. There are many different types of SMD capacitor

ranging from ceramic types, through tantalum varieties to electrolytic and more. Of these, theceramic SMD capacitors are the most widely used.

Ceramic capacitor: The ceramic capacitor is a type of capacitor that is used in many

applications from audio to RF. Values range from a few picofarads to around 0.1

microfarads. Ceramic capacitors are by far the most commonly used type of capacitor being

cheap and reliable and their loss factor is particularly low although this is dependent on the

exact dielectric in use


10/55

10

Applications of capacitor:

The following is the typical capacitor applications in electronic industries:

DC blocking capacitor: In this application the capacitor blocks the passage of DC current(after completely charged) and yet allows the AC to pass at certain portion of a circuit.

Capacitor as a filter: Capacitors are the main elements of filters. There are several types offilters that are used in electronic circuits, such as LPF (Low Pass Filter), HPF (high Pass

Filter), BPF (Band Pass Filter), etc.Since the reactance of the capacitor is inversely related

to the frequency, therefore it can be used to increase or decrease the impedance of the circuit

at certain frequencies and therefore does the filtration job.

Capacitor as a discharge unit: Capacitors used as a charging unit and the release of thecharge (discharge energy) is used for triggering, ignition, and in high scale as a power source.

By Pass capacitor: The reactance of capacitor decreases as the frequency increases.Therefore in certain application it is used in parallel with other components to bypass it at a

specified frequency.

4.3 Diodes:

An electronic device that restricts current flow chiefly to one direction. A diode is a

specialized electronic component with two electrodes called the anode & the cathode. Mostdiodes are made with semiconductor materials such as silicon, germanium, or selenium.

Some diodes are comprised of metal electrodes in a chamber evacuated or filled with a pure

elemental gas at low pressure. Diodes can be used as rectifiers, signal limiters, voltage

regulators, switches, signal modulators, signal mixers, signal demodulators, and oscillators.

Symbol of diode:

Figure 4.6:Symbol of diode
http://searchcio-midmarket.techtarget.com/sDefinition/0,,sid183_gci212960,00.htmlhttp://searchtelecom.techtarget.com/sDefinition/0,,sid103_gci213079,00.htmlhttp://searchtelecom.techtarget.com/sDefinition/0,,sid103_gci213079,00.htmlhttp://searchcio-midmarket.techtarget.com/sDefinition/0,,sid183_gci212960,00.html


11/55

11

Types of diodes:

Several types of diodes are available for use in electronics design. Some of the different types

of diodes are:

Figure 4.7:Types of diodes

Light Emitting Diode (LED): It is one of the most popular types of diodes and when this

diode permits the transfer of electric current between the electrodes, light is produced. In

most of the diodes, the light (infrared) cannot be seen as they are at frequencies that do not

permit visibility. When the diode is switched on or forward biased, the electrons recombine

with the holes and release energy in the form of light (electroluminescence).The color of light

depends on the energy gap of semiconductor.

Avalanche Diode: This type of diode operates in the reverse bias, and used avalanche effect

for its operation. The avalanche breakdown takes place across the entire PN junction, when

the voltage drop is constant and is independent of current. Generally, the avalanche diode is

used for photo-detection, wherein high levels of sensitivity can be obtained by the avalanche

process.

Laser Diode: This type of diode is different from the LED type, as it produces coherent light.

These diodes find their application in DVD and CD drives, laser pointers, etc. However, they

are cheaper than other forms of laser generators. Moreover, these laser diodes have limited

life.


12/55

12

Schottky Diodes: The lower forward voltage drop may be somewhere between 0.15 and 0.4

volts at low currents, as compared to the 0.6 volts for a silicon diode. In order to achieve this

performance, these diodes are constructed differently from normal diodes, with metal to

semiconductor contact. Schottky diodes are used in RF applications, rectifier applications and

clamping diodes.

Zener diode: This type of diode provides a stable reference voltage, thus is a very useful

type and is used in vast quantities. The diode runs in reverse bias, and breaks down on the

arrival of a certain voltage. A stable voltage is produced, if the current through the resistor is

limited. In power supplies, these diodes are widely used to provide a reference voltage.

Photodiode: Photodiodes are used to detect light and feature wide, transparent junctions.

Generally, these diodes operate in reverse bias, wherein even small amounts of current flow,

resulting from the light, can be detected with ease. Photodiodes can also be used to generate

electricity, used as solar cells and even in photometry in the photo diode.

Varicap Diode or Varactor Diode: This type of diode feature a reverse bias placed upon it,

which varies the width of the depletion layer as per the voltage placed across the diode. This

diode acts as a capacitor and capacitor plates are formed by the extent of conduction regions

and the depletion region as the insulating dielectric. By altering the bias on the diode, the

width of the depletion region changes, thereby varying the capacitance.

Rectifier Diode: These diodes are used to rectify alternating power inputs in power supplies.

They can rectify current levels that range from an amp upwards. If low voltage drops are

required, then Schottky diodes can be used, however, generally these diodes are PN junction

diodes.

ZENER DIODE: A silicon semiconductor device used as a voltage regulator because of its

ability to maintain an almost constant voltage with a wide range of currents.

Example: Circuit symbol:

a = anode, k = cathode

Figure 4.8:zener diode


13/55

13

Zener diodes are used to maintain a fixed voltage. They are designed to 'breakdown' in a reliable and

non-destructive way so that they can be used in reverseto maintain a fixed voltage across their

terminals. The diagram shows how they are connected, with a resistor in series to limit the current.

Zener diodes can be distinguished from ordinary diodes by their code and breakdown voltage which

are printed on them. Zener diode codes begin BZX... or BZY... Their breakdown voltage is printed

with V in place of a decimal point, so 4V7 means 4.7V for

example.

Zener diodes are rated by their breakdown voltage and

maximum power:

The minimum voltage available is 2.4V. Power ratings of 400mW and 1.3W are common.

Diode operation:

Forward bias: In forward bias operation, the diode will not conduct significant

current until the voltage reaches about 0.7V. After that point large increases in current cause

little change in voltage.

Reverse bias: In reverse bias operation, the diode will not conduct significant current

until some breakdown threshold voltage which is typically quite large (e.g. 200V). This

voltage must be somewhat greater than the peak input voltage (PIV) rating of the diode.

(Device dependent)

Figure 4.9:Diode Characteristics


14/55

14

4.4 PHOTO DIODE:

A photodiode is a type ofphoto detector capable of converting light into either current

or voltage, depending upon the mode of operation. The common, traditional solar cell used to

generate electric solar power is a large area photodiode.

Photodiodes are similar to regular semiconductor diodes except that they may be

either exposed (to detect vacuum UV or X-rays) or packaged with a window or optical fiber

connection to allow light to reach the sensitive part of the device. Many diodes designed for

use specifically as a photodiode use a PIN junction rather than a p-n junction, to increase the

speed of response. A photodiode is designed to operate in reverse bias

Symbol of Photo Diode:

Figure 4.10:Symbol of photo diode

Principle of operation:

A photodiode is a p-n junction or PIN structure. When a photon of sufficient energy

strikes the diode, it excites an electron, thereby creating a free electron (and a positively

charged electron hole). This mechanism is also known as the inner photoelectric effect. If the

absorption occurs in the junction's depletion region, or one diffusion length away from it,

these carriers are swept from the junction by the built-in field of the depletion region. Thus

holes move toward the anode, and electrons toward the cathode, and a photocurrent is

produced. This photocurrent is the sum of both the dark current (without light) and the light

current, so the dark current must be minimized to enhance the sensitivity of the device.
http://en.wikipedia.org/wiki/Photodetectorhttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Solar_cellhttp://en.wikipedia.org/wiki/Solar_powerhttp://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Diodehttp://en.wikipedia.org/wiki/Vacuum_UVhttp://en.wikipedia.org/wiki/X-rayshttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/PIN_diodehttp://en.wikipedia.org/wiki/P-n_junctionhttp://en.wikipedia.org/wiki/Reverse_biashttp://en.wikipedia.org/wiki/P-n_junctionhttp://en.wikipedia.org/wiki/PIN_diodehttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Free_electronhttp://en.wikipedia.org/wiki/Photoelectric_effecthttp://en.wikipedia.org/wiki/Depletion_regionhttp://en.wikipedia.org/wiki/Anodehttp://en.wikipedia.org/wiki/Cathodehttp://en.wikipedia.org/wiki/Photocurrenthttp://en.wikipedia.org/wiki/Photocurrenthttp://en.wikipedia.org/wiki/Cathodehttp://en.wikipedia.org/wiki/Anodehttp://en.wikipedia.org/wiki/Depletion_regionhttp://en.wikipedia.org/wiki/Photoelectric_effecthttp://en.wikipedia.org/wiki/Free_electronhttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/PIN_diodehttp://en.wikipedia.org/wiki/P-n_junctionhttp://en.wikipedia.org/wiki/Reverse_biashttp://en.wikipedia.org/wiki/P-n_junctionhttp://en.wikipedia.org/wiki/PIN_diodehttp://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/X-rayshttp://en.wikipedia.org/wiki/Vacuum_UVhttp://en.wikipedia.org/wiki/Diodehttp://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Solar_powerhttp://en.wikipedia.org/wiki/Solar_cellhttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Photodetector


15/55

15

Figure 4.11: Characteristics of Photo diode

Photovoltaic mode:

When used in zero bias or out of the photovoltaic mode, the flow of photocurrent

device is restricted and a voltage builds up. This mode exploits the photovoltaic effect, which

is the basis for solar cellsa traditional solar cell is just a large area photodiode.

Photoconductive mode:

In this mode the diode is often reverse biased ,dramatically reducing the response time

at the expense of increased noise. This increases the width of the depletion layer, which

decreases the junction's capacitance resulting in faster response times. The reverse bias

induces only a small amount of current along its direction while the photocurrent remains

virtually the same. For a given spectral distribution, the photocurrent is linearly proportional

to the luminance.

Applications:

1. P-N photodiodes are used in similar applications to other photo detectors, such asphotoconductors, charge-coupled devices, and photomultiplier tubes. They may be used to

generate an output which is dependent upon the illumination (analog; for measurement and

the like), or to change the state of circuitry (digital; either for control and switching, or digital

signal processing).
http://en.wikipedia.org/wiki/Bias_%28electrical_engineering%29http://en.wikipedia.org/wiki/Photovoltaic_effecthttp://en.wikipedia.org/wiki/Solar_cellhttp://en.wikipedia.org/wiki/P-n_junction#Reverse_biashttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/Illuminancehttp://en.wikipedia.org/wiki/Photodetectorhttp://en.wikipedia.org/wiki/Photoconductorhttp://en.wikipedia.org/wiki/Charge-coupled_devicehttp://en.wikipedia.org/wiki/Photomultiplierhttp://en.wikipedia.org/wiki/Photomultiplierhttp://en.wikipedia.org/wiki/Charge-coupled_devicehttp://en.wikipedia.org/wiki/Photoconductorhttp://en.wikipedia.org/wiki/Photodetectorhttp://en.wikipedia.org/wiki/Illuminancehttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/P-n_junction#Reverse_biashttp://en.wikipedia.org/wiki/Solar_cellhttp://en.wikipedia.org/wiki/Photovoltaic_effecthttp://en.wikipedia.org/wiki/Bias_%28electrical_engineering%29


16/55

16

2. Photodiodes are used in consumer electronics devices such as compact disc players, smokedetectors, and the receivers for infrared remote control devices used to control equipment

from televisions to air conditioners. For many applications either photodiodes or

photoconductors may be used. Either type of photo sensor may be used for light

measurement, as in camera light meters, or to respond to light levels, as in switching on street

lighting after dark.

3. Photo sensors of all types may be used to respond to incident light, or to a source of lightwhich is part of the same circuit or system. A photodiode is often combined into a single

component with an emitter of light, usually a light-emitting diode (LED), either to detect the

presence of a mechanical obstruction to the beam (slotted optical switch), or to couple two

digital or analog circuits while maintaining extremely high electrical isolation between them,

often for safety (optocoupler).

4. Photodiodes are often used for accurate measurement of light intensity in science andindustry. They generally have a more linear response than photoconductors.

5. They are also widely used in various medical applications, such as detectors for computedtomography (coupled with scintillators), instruments to analyze samples (immunoassay), and

pulse oximeters.

6. PIN diodes are much faster and more sensitive than p-n junction diodes, and hence are oftenused for optical communications and in lighting regulation.

4.5 Light Emitting Diodes (LEDs):

Circuit symbol:

Figure 4.12:Symbol of LED

Parts in LED:
http://en.wikipedia.org/wiki/Consumer_electronicshttp://en.wikipedia.org/wiki/Compact_dischttp://en.wikipedia.org/wiki/Smoke_detectorhttp://en.wikipedia.org/wiki/Smoke_detectorhttp://en.wikipedia.org/wiki/Remote_controlhttp://en.wikipedia.org/wiki/Televisionhttp://en.wikipedia.org/wiki/Camerahttp://en.wikipedia.org/wiki/Light-emitting_diodehttp://en.wikipedia.org/wiki/Slotted_optical_switchhttp://en.wikipedia.org/wiki/Coupling_%28electronics%29http://en.wikipedia.org/wiki/Electrical_isolationhttp://en.wikipedia.org/wiki/Optocouplerhttp://en.wikipedia.org/wiki/Computed_tomographyhttp://en.wikipedia.org/wiki/Computed_tomographyhttp://en.wikipedia.org/wiki/Scintillatorhttp://en.wikipedia.org/wiki/Immunoassayhttp://en.wikipedia.org/wiki/Pulse_oximeterhttp://en.wikipedia.org/wiki/PIN_diodehttp://en.wikipedia.org/wiki/Optical_communicationhttp://en.wikipedia.org/wiki/Optical_communicationhttp://en.wikipedia.org/wiki/PIN_diodehttp://en.wikipedia.org/wiki/Pulse_oximeterhttp://en.wikipedia.org/wiki/Immunoassayhttp://en.wikipedia.org/wiki/Scintillatorhttp://en.wikipedia.org/wiki/Computed_tomographyhttp://en.wikipedia.org/wiki/Computed_tomographyhttp://en.wikipedia.org/wiki/Optocouplerhttp://en.wikipedia.org/wiki/Electrical_isolationhttp://en.wikipedia.org/wiki/Coupling_%28electronics%29http://en.wikipedia.org/wiki/Slotted_optical_switchhttp://en.wikipedia.org/wiki/Light-emitting_diodehttp://en.wikipedia.org/wiki/Camerahttp://en.wikipedia.org/wiki/Televisionhttp://en.wikipedia.org/wiki/Remote_controlhttp://en.wikipedia.org/wiki/Smoke_detectorhttp://en.wikipedia.org/wiki/Smoke_detectorhttp://en.wikipedia.org/wiki/Compact_dischttp://en.wikipedia.org/wiki/Consumer_electronics


17/55

17

Figure 4.13: parts of LED

Function: LEDs emit light when an electric current passes through them.

PIN DIAGRAM:

Figure 4.14:Pin diagram of LED


18/55

18

LED Specifications:

These are infrared LEDs; the light output is not visible by our eyes. They can

be used as replacement LEDs for remote controls, night vision for camcorders, invisible

beam sensors, etc.

Size (mm) 5mm

Lens Color Light Blue

Peak wavelength up 940nm

Continuous Forward Current IF 20 am

Typical Voltage (V) 1.3

Peak Forward Current IFP 1.0 A

Reverse Voltage VR 5 V

Operating Temperature Top -40 ~ +85

Storage Temperature TSgt -40 ~ +85

Soldering Temperature Ts l 260

Connecting and soldering:

LEDs must be connected the correct way round, the diagram may be

labeled a or + for anode and k or - for cathode. The cathode is the short lead

and there may be a slight flat on the body of round LEDs. If you can see inside

the LED the cathode is the larger electrode. LEDs can be damaged by heat when soldering,

but the risk is small unless you are very slow. No special precautions are needed for soldering

most LEDs. Figure 4.15:testing an LED

Testing an LED:

Never connect an LED directly to a battery or power supply! It will be

destroyed almost instantly because too much current will pass through and burn

it out.LEDs must have a resistor in series to limit the current to a safe value, for


19/55

19

quick testing purposes a 1k resistor is suitable for most LEDs if your supply

voltage is 12V or less. Remember to connect the LED the correct way round!

Colors of LEDs:

LEDs are available in red, orange, amber, yellow, green, blue and white. Blue and

white LEDs are much more expensive than the other colors.

The colour of an LED is determined by the semiconductor material, not by the

coloring of the 'package' (the plastic body). LEDs of all colors are available in uncolored

packages which may be diffused (milky) or clear (often described as 'water clear'). The

colored packages are also available as diffused (the standard type) or transparent.

Tri-colour LEDs:

The most popular type of tri-colour LED has a red and a green LED

combined in one package with three leads. They are called tri-colour because

mixed red and green light appears to be yellow and this is produced when both the

red and green LEDs are on. The diagram shows the construction of a tri-colour LED. Note

the different lengths of the three leads. The centre lead (k) is the common cathode for both

LEDs, the outer leads (a1 and a2) are the anodes to the LEDs allowing each one to be lit

separately, or both together to give the third colour.

Bi-colour LEDs:

A bi-colour LED has two LEDs wired in 'inverse parallel' (one

forwards, one backwards) combined in one package with two leads.

Only one of the LEDs can be lit at one time and they are less useful

than the tri-colour LEDs described above.

As well as a variety of colors, sizes and shapes, LEDs also vary in their viewing

angle. This tells you how much the beam of light spreads out. Standard LEDs have a viewing

angle of 60 but others have a narrow beam of 30 or less.

Connecting LEDs in series:

If you wish to have several LEDs on at the same time it may be possible to connect

them in series. This prolongs battery life by lighting several LEDs with the same current as

just one LED. All the LEDs connected in series pass the same current so it is best if they

are all the same type. The power supply must have sufficient voltage to provide about 2V for


20/55

20

each LED (4V for blue and white) plus at least another 2V for the resistor. To work out a

value for the resistor you must add up all the LED voltages and use this for VL.

Calculating an LED resistor value:

An LED must have a resistor connected in series to limit the current through the LED,

otherwise it will burn out almost instantly.

The resistor value, R is given by:

R = (VS - VL) / I

VS=supply-voltage

VL = LED voltage (usually 2V, but 4V for blue

and white LEDs) I = LED current (e.g.

10mA = 0.01A,

or 20mA = 0.02A)

Make sure the LED current you choose is less than the maximum permitted

and convert the current to amps (A) so the calculation will give the resistor value in

ohms.To convert mA to A divide the current in mA by 1000 because 1mA = 0.001A.

If the calculated value is not available choose the nearest standard resistor value

which is greater, so that the current will be a little less than you chose. In fact you may wish

to choose a greater resistor value to reduce the current (to increase battery life for example)

but this will make the LED less bright.

Avoid connecting LEDs in parallel!:


21/55

21

Connecting several LEDs in parallel with just one resistor shared between them is

generally not a good idea. If the LEDs require slightly different voltages only the lowest

voltage LED will light and it may be destroyed by the larger current flowing through it. If

LEDs are in parallel each one should have its own resistor.

Reading a table of technical data for LEDs:

Suppliers' catalogues usually include tables of technical data for components such as

LEDs. These tables contain a good deal of useful information in a compact form but they can

be difficult to understand if you are not familiar with the abbreviations used.

The table below shows typical technical data for some 5mm diameter round LEDs

with diffused packages (plastic bodies). Only three columns are important and these are

shown in bold. Please see below for explanations of the quantities.

Type ColourIF

max.

VF

typ.

VF

max.

VR

max.

Luminous

intensity

Viewing

angleWavelength

Standard Red 30mA 1.7V 2.1V 5V5mcd @

10mA60 660nm

StandardBright

red30mA 2.0V 2.5V 5V

80mcd @

10mA60 625nm

Standard Yellow 30mA 2.1V 2.5V 5V32mcd @

10mA60 590nm

Standard Green 25mA 2.2V 2.5V 5V32mcd @

10mA60 565nm

High

intensityBlue 30mA 4.5V 5.5V 5V

60mcd @

20mA50 430nm

Super

brightRed 30mA 2.5V 5V

500mcd @

20mA60 660nm

4.6 INFRA RED LED:

An IR LED, also known as IR transmitter, is a special purpose LED that transmits

infrared rays in the range of 760 nm wavelength. Such LEDs are usually made of gallium

arsenide or aluminum gallium arsenide. They, along with IR receivers, are commonly used as

sensors.
http://www.engineersgarage.com/content/ledhttp://www.engineersgarage.com/content/led


22/55

22

Symbol of IR LED:

Figure 4.16:Symbol of IR LED

The appearance is same as a common LED. Since the human eye cannot see the

infrared radiations, it is not possible for a person to identify whether the IR LED is working

or not, unlike a common LED. To overcome this problem, the camera on a cell phone can be

used. The camera can show us the IR rays being emanated from the IR LED in a circuit.


23/55

23

4.7 TRANSISTOR:

Bipolar junction transistor (BJI) or simply transistor was invented in 1950 by Schockely. It is the

invention of the junction transistor that has brought the revolution change in the field of electronics.

The name transistor was coined from the words transfer resistor. Because this semiconductor device

offers low resistance to the flow of current in one portion (Emitter-Base junction) while high

resistance in the other portion (collection-base junction) of the device. It means that transistor

transforms current flow from low resistance path to the high resistance path.

FORMATION OF TRANSISTORS:

A transistor is basically a silicon or germanium crystal containing three separate regions. It is formed

by the sandwich of a thin layer of one type (either N type or p type) semiconductor material between

two layers of other semiconductor material. So transistor may be regarded as two back junctions in a

single piece of semi conductor.

The two junctions give rise to three regions. The middle region is called base and the outer two

regions are called as Emitter and collector. Even though outer regions are of the same type theirfunction cannot be interchanged. Because, the two regions have different physical & electrical

properties. Three terminals were taken from three regions, namely Emitter Base & Collector. The PN

junction or Emitter junction and the PN junction between Base and collectors called Collector Base

junction or simply collector junction.

So transistor is a three layers, two junction, and three terminal semiconductor device.

EMITTER (E):

It is that region of the transistor which emits majority charge carriers into base region. Physical area of emitter is less than collector but more the base region. Its doping concentration is more than both base and collector.

BASE (B):

It is the middle region of the transistor.


24/55

24

It is very thin and lightly doped as compared to either emitter or collector.

COLLECTOR (C):

It is that region of the transistor which collects the majority charge carriers emitted bythe emitter through the base region

Its doping concentration is greater than base region & less than emitter region. In general collector region is made physically larger than emitter and base to dissipate

much heat generated

BC548:

BC548 is general purpose silicon, NPN, bipolar junction transistor. It is used for

amplification and switching purposes. The current gain may vary between 110 and 800. The

maximum DC current gain is 800.

Its equivalent transistors are 2N3904 and 2SC1815. These equivalent transistors however

have different lead assignments. The variants of BC548 are 548A, 548B and 548C which

vary in range of current gain and other characteristics.

The transistor terminals require a fixed DC voltage to operate in the desired region of its

characteristic curves. This is known as the biasing. For amplification applications, the

transistor is biased such that it is partly on for all input conditions. The input signal at base is

amplified and taken at the emitter. BC548 is used in common emitter configuration for

amplifiers. The voltage divider is the commonly used biasing mode. For switching

applications, transistor is biased so that it remains fully on if there is a signal at its base. In

the absence of base signal, it gets completely off.

Figure 4.17:Pin diagram of BC548.


25/55

25

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 electronicdevices.

Highly automated manufacturing processes, resulting in low per-unit cost. Lower possible operating voltages, making transistors suitable for small, battery-

powered applications.

No warm-up period for cathode heaters required after power application. 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

50 years.

Complementary devices available, facilitating the design of complementary-symmetry circuits, something not possible with vacuum tubes.

Insensitivity to mechanical shock and vibration, thus avoiding the problemof microphones in audio applications.

Limitations:

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

a vacuum.

Silicon transistors do not operate at voltages higher than about1,000 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.

Silicon transistors are much more vulnerable than electron tubes to an electromagneticpulse generated by a high-altitude nuclear explosion.


26/55

26

4.8 RELAY:

A relay is usually an electromechanical device that is actuated by an electrical

current. The current flowing in one circuit causes the opening or closing of another circuit.

Relays are like remote control switches and are used in many applications because of their

relative simplicity, long life, and proven high reliability.

Relays are used in a wide variety of applications throughout industry, such as in

telephone exchanges, digital computers and automation systems. Highly sophisticated relays

are utilized to protect electric power systems against trouble and power blackouts as well as

to regulate and control the generation and distribution of power.

In the home, relays are used in refrigerators, washing machines and dishwashers, and

heating and air-conditioning controls. Although relays are generally associated with electrical

circuitry, there are many other types, such as pneumatic and hydraulic. Input may be

electrical and output directly mechanical, or vice versa.

Relay Design:

There are only four main parts in a relay. They are

Electromagnet Movable Armature Switch point contacts Spring

The figures given below show the actual design of a simple relay.

Relay Construction:

It is an electro-magnetic relay with a wire coil, surrounded by an iron core. A path of

very low reluctance for the magnetic flux is provided for the movable armature and also the

switch point contacts. The movable armature is connected to the yoke which is mechanically

connected to the switch point contacts. These parts are safely held with the help of a spring.


27/55

27

The spring is used so as to produce an air gap in the circuit when the relay becomes de-

energized.

Figure 4.18:Relay construction

Working of Relay:

The working of a relay can be better understood by explaining the following diagram

given below.

Figure 4.19: working of relay

The diagram shows an inner section diagram of a relay. An iron core is surrounded by

a control coil. As shown, the power source is given to the electromagnet through a control

switch and through contacts to the load. When current starts flowing through the control coil,

the electromagnet starts energizing and thus intensifies the magnetic field. Thus the upper

contact arm starts to be attracted to the lower fixed arm and thus closes the contacts causing a


28/55

28

short circuit for the power to the load. On the other hand, if the relay was already de-

energized when the contacts were closed, then the contact move oppositely and make an open

circuit.

As soon as the coil current is off, the movable armature will be returned by a force

back to its initial position. This force will be almost equal to half the strength of the magnetic

force. This force is mainly provided by two factors. They are the spring and also gravity.

Relays are mainly made for two basic operations. One is low voltage application and

the other is high voltage. For low voltage applications, more preference will be given to

reduce the noise of the whole circuit. For high voltage applications, they are mainly designed

to reduce a phenomenon called arcing.

Relay Basics:

The basics for all the relays are the same. Take a look at a 4pin relay shown below.

There are two colors shown. The green color represents the control circuit and the red color

represents the load circuit. A small control coil is connected onto the control circuit. A switch

is connected to the load. This switch is controlled by the coil in the control circuit. Now let us

take the different steps that occur in a relay. Relay operation:

Energized Relay (ON):

As shown in the circuit, the current flowing through the coils represented by pins 1

and 3 causes a magnetic field to be aroused. This magnetic field causes the closing of the pins

2 and 4. Thus the switch plays an important role in the relay working. As it is a part of the

load circuit, it is used to control an electrical circuit that is connected to it. Thus, when the

relay in energized the current flow will be through the pins 2 and 4.


29/55

29

Energized Relay (ON)

DeEnergized Relay (OFF):

As soon as the current flow stops through pins 1 and 3, the switch opens and thus the

open circuit prevents the current flow through pins 2 and 4. Thus the relay becomes de-

energized and thus in off position. De-Energized Relay (OFF)

In simple, when a voltage is applied to pin 1, the electromagnet activates, causing a

magnetic field to be developed, which goes on to close the pins 2 and 4 causing a closed

circuit. When there is no voltage on pin 1, there will be no electromagnetic force and thus no

magnetic field. Thus the switches remain open.

Relay Applications:

Relays are used to realize logic functions. They play a very important role in providing

safety critical logic.

Relays are used to provide time delay functions. They are used to time the delay open anddelay close of contacts.

Relays are used to control high voltage circuits with the help of low voltage signals. Similarlythey are used to control high current circuits with the help of low current signals.

They are also used as protective relays. By this function all the faults during transmission andreception can be detected and isolated.


30/55

30

Advantages of Relays:

The complete electrical isolation improves safety by ensuring that high voltages and currentscannot appear where they should not be.

It is easy to tell when a relay is operating - you can hear a click as the relay switches on andoff and you can sometimes see the contacts moving.

Disadvantages of Relays:

Being mechanical though, relays do have some disadvantages over other methods of

electrical isolation:

Their parts can wear out as the switch contacts become dirty - high voltages and currentscause sparks between the contacts.

They cannot be switched on and off at high speeds because they have a slow response and theswitch contacts will rapidly wear out due to the sparking.

SPEAKER:

In tis circuit we used 8ohms,0.5w speaker to produce the desired out put melody at the out

put side. the external view of the speaker is

Figure 4.20: Speaker

4.9INTEGRATED CIRCUITS:4.9.1 IC 7805:

7805 is a voltage regulator integrated circuit. It is a member of 78xx series of

fixed linear voltage regulator ICs. The voltage source in a circuit may have fluctuations

and would not give the fixed voltage output. The voltage regulator IC maintains the

output voltage at a constant value. The xx in 78xx indicates the fixed output voltage it is

designed to provide. 7805 provides +5V regulated power supply. Capacitors of suitable

values can be connected at input and output pins depending upon the respective voltage

levels.


31/55

31

Figure 4.21:PIN DIAGRAM FOR 7805

Pin Description:

Pin No Function Name

1 Input voltage (5V-18V) Input

2 Ground (0V) Ground

3 Regulated output; 5V (4.8V-5.2V) Output

4.9.2 IC 74LS244:

General Description:

These buffers/line drivers are designed to improve both the performance and PC board

density of 3-STATE buffers/drivers employed as memory-address drivers, clock drivers, and

bus-oriented transmitters/receivers.

Featuring 400mV of hysteresis at each low current PNP data line input, they provide

improved noise rejection and high fan-out outputs and can be used to drive terminated lines

down to133

Figure 4.22:IC 74LS244


32/55

32

Features:

3-STATE outputs drive bus lines directly PNP inputs reduce DC loading on bus lines Hysteresis at data inputs improves noise margins Typical propagation delay times Inverting 10.5 ns No inverting 12 ns Typical enable/disable time 18 ns Typical power dissipation (enabled)

.

Function Table:

L =>LOW Logic Level

H =>HIGH Logic Level

X =>Either LOW or HIGH Logic Level

Z =>High Impedance

PIN Diagram:

These octal buffers and line drivers are designed specifically to improve both the

performance and density of three-state memory address drivers, clock drivers, and bus-

oriented receivers and transmitters. The designer has a choice of selected combinations of

inverting and non-inverting outputs, symmetrical, active-low output-control (G) inputs, and

complementary output-control (G and G) inputs. The SN74LS and SN74S devices can be

used to drive terminated lines down to 133.

inputs outputs

G A Y

L

L

H

L

H

X

L

H

Z


33/55

33

Logic Diagram :

Figure 4.23:Pin diagram of IC 74LS244

4.9.3 IC ULN 2003

DESCRIPTION

The ULN2003 is a monolithic high voltage and high current Darlington transistor

arrays. It consists of seven NPN darlington pairs that features high-voltage outputs with

common-cathode clamp diode for switching inductive loads. The collector-current rating of a

single darlington pair is 500mA. The darlington pairs may be paralleled for higher current

capability. Applications include relay drivers, hammer drivers, lamp drivers, display

drivers(LED gas discharge),line drivers, and logic buffers.

FEATURES

500mA rated collector current(Single output) High-voltage outputs: 50V Inputs compatible with various types of logic. Relay driver application


34/55

34

Figure 4.24: IC ULN2003

Logic Diagram:

Figure 4.25:pin diagram of IC ULN2003


35/55

35

MELODY GENERATOR(UM66):

General description

Um66 basically a MELODY INTEGRATED CIRCUIT .The UTC

UM66TXXL series are CMOS LSI designed for using in door bell, telephone and toy

application. It is an on-chip ROM programmed for musical performance. Produced by

CMOS technology, the device results in very low power consumption. Since the UTC

UM66TXXL series include oscillation circuits a compact melody module can be

constructed with only a few additional components.

Pin Configuration:

Figure 4.26:Pin configuration of UM66

Pin Description:


36/55

36

Block Diagram:

Figure 4.27: Block diagram of UM66

Functional description:

Oscillator circuit

The oscillator frequency is used as a time base for tone and beat generators. Its accuracy

affects the quality of the music.

Tone generator

Tone frequencies are oscillator frequencies divided by m, where M is any even number from

64 to 254. Within a melody, 14 scales can be selected including PAUSE code and END


37/55

37

code. The tone generator is a programmed divider. The range of scales is fromC4:toC6

and range of frequency varies from 258Hz to 32768Hz

Beat Generator

The beat generator is also a programmed divider. It contain 15 available beats as

follows:1/4,1/2, 3/4, 1, 1-1/4, 1-1/2, 1-3/4, 2, 2-1/4, 2-1/2, 2-3/4, 3, 3-1/4, 3-1/2, 3-

3/4.four beats can be selected from these.

Melody ROM

The mask ROM can memorize 64 notes with 6 bits; 4 bits are used for controlling the scalecode and 2 bits are used for the controlling rhythm code

Typical application circuits:

One Short Mode for Piezo: One Short Mode for Piezo

(normal open switch)


38/55

38

5.PRINTED CIRCUIT BOARD

A printed circuit board, or PCB, is used to mechanically support and

electrically connect electronic components using conductive pathways, tracks or signal traces

etched from copper sheets laminated onto a non-conductive substrate. It is also referred to

as printed wiring board (PWB) or etched wiring board. A PCB populated with electronic

components is a printed circuit assembly (PCA), also known as a printed circuit board

assembly(PCBA). Printed circuit boards are used in virtually all but the simplest

commercially produced electronic devices.

PCBs are inexpensive, and can be highly reliable. They require much more

layout effort and higher initial cost than either wire wrap or point-to-point construction, but

are much cheaper and faster for high-volume production; the production and soldering of

PCBs can be done by automated equipment. Much of the electronics industry's PCB design,

assembly, and quality control needs are set by standards that are published by

the IPC organization.

Solder resist: Areas that should not be soldered may be covered with a polymer solder

resist (solder mask) coating. The solder resist prevents solder from bridging between

conductors and creating short circuits. Solder resist also provides some protection from the

environment. Solder resist is typically 2030 micrometres thick.
http://en.wikipedia.org/wiki/Electronic_componenthttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Laminatedhttp://en.wikipedia.org/wiki/Wire_wraphttp://en.wikipedia.org/wiki/Point-to-point_constructionhttp://en.wikipedia.org/wiki/IPC_(electronics)http://en.wikipedia.org/wiki/IPC_(electronics)http://en.wikipedia.org/wiki/Point-to-point_constructionhttp://en.wikipedia.org/wiki/Wire_wraphttp://en.wikipedia.org/wiki/Laminatedhttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Electronic_component


39/55

39

6.SOLDERING

Soldering is a process in which two or more metal items are joined together

by melting and flowing a filler metal (solder) into the joint, the filler metal having a

lower melting point than the workpiece. Soldering differs from welding in that soldering does

not involve melting the work pieces.

There are three forms of soldering, each requiring higher temperatures and each

producing an increasingly stronger joint strength:

1. soft soldering, which originally used a tin-lead alloy as the filler metal,2. silver soldering, which uses an alloy containing silver,3. brazing which uses a brass alloy for the filler.

The alloy of the filler metal for each type of soldering can be adjusted to modify the

melting temperature of the filler. Soldering appears to be a hot glueprocess, but it differs from

gluing significantly in that the filler metals alloy with the workpiece at the junction to form a

gas- and liquid-tight bond.[1]

Soft soldering is characterized by having a melting point of the filler metal below

approximately 400 C (752 F), whereas silver soldering and brazing use higher

temperatures, typically requiring a flame or carbon arc torch to achieve the melting of the

filler. Soft solder filler metals are typically alloys (often containing lead) that

have liquidus temperatures below 350C.In the soldering process, heat is applied to the parts

to be joined, causing the solder to melt and to bond to the workpieces in an alloying process

called wetting. In stranded wire, the solder is drawn up into the wire by capillary action in a

process called 'wicking'. The joint strength is dependent on the filler metal used, where soft

solder is the weakest and the brass alloy used for brazing is the strongest. Soldering, which

uses metal to join metal in a molecular bond has electrical conductivity and is water- and gas-

tight.
http://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Solderhttp://en.wikipedia.org/wiki/Melting_pointhttp://en.wikipedia.org/wiki/Weldinghttp://en.wikipedia.org/wiki/Alloyhttp://en.wikipedia.org/wiki/Silverhttp://en.wikipedia.org/wiki/Brazinghttp://en.wikipedia.org/wiki/Brasshttp://en.wikipedia.org/wiki/Hot_gluehttp://en.wikipedia.org/wiki/Soldering#cite_note-indiumcorporation-0http://en.wikipedia.org/wiki/Soldering#cite_note-indiumcorporation-0http://en.wikipedia.org/wiki/Soldering#cite_note-indiumcorporation-0http://en.wikipedia.org/wiki/Leadhttp://en.wikipedia.org/wiki/Liquidushttp://en.wikipedia.org/wiki/Wettinghttp://en.wikipedia.org/wiki/Capillary_actionhttp://en.wikipedia.org/wiki/Capillary_actionhttp://en.wikipedia.org/wiki/Wettinghttp://en.wikipedia.org/wiki/Liquidushttp://en.wikipedia.org/wiki/Leadhttp://en.wikipedia.org/wiki/Soldering#cite_note-indiumcorporation-0http://en.wikipedia.org/wiki/Hot_gluehttp://en.wikipedia.org/wiki/Brasshttp://en.wikipedia.org/wiki/Brazinghttp://en.wikipedia.org/wiki/Silverhttp://en.wikipedia.org/wiki/Alloyhttp://en.wikipedia.org/wiki/Weldinghttp://en.wikipedia.org/wiki/Melting_pointhttp://en.wikipedia.org/wiki/Solderhttp://en.wikipedia.org/wiki/Metal


40/55

40

Steps for solderingtechnique:

Here is the step by step procedure for soldering.

1. First of all keep the solder iron plugged in for about a minute and a half beforestarting to use it. By that time the solder iron may get heated to the optimum

temperature [250 degree Celsius].

2. Bend the leads of the different devices that are to be connected to the PCB. For aclean bend, the approximate distance of bend is about 2mm from its body ends.

3. If you are connecting a resistor to the PCB, find its spot and place it into the hole ofthe PCB.

4. After placing the resistor flip the PCB in such a way that the inserted leads lookstowards you.

5. Take the soldering iron in the right hand and the solder wire in the left hand. Thesolder wire must be placed on your finger tips with about 3 inches extending from

your finger grip.

6. Bring both the solder iron tip and the solder wire tip close to the base of the lead ofthe resistor and copper track of the PCB. Make them come in contact at the same

instant at the junction.

7. The solder wire starts to melt as soon as the contact is made.8. When the wire starts melting keep pushing it till the joint has been filled up with the

molten alloy.

9. Move away the solder wire and the solder iron simultaneously and allow the moltenwire to solidify. Thus one lead of the resistor has been connected to the PCB. Do the

same step for the other lead and also for all other components.

Precautions to be taken while Soldering:

For a good heat transfer, the solder wire and the solder iron must be well

cleaned before starting. It must also be pre-tinned with solder. In order to avoid the

overheating of PCB, the components are usually elevated above the PCB. After the

component is inserted in the PCB hole, the excess lead is cut off, thus leaving a length ofabout the radius of the pad.

After soldering, the soldered joints must also be cleaned after it has been solidified.

Some components that are to be soldered may be heat sensitive. For such

components a heat sink may be used on the leads which will reduce the heat transfer to the

components. The only problem is that for such components more heat will be required from

the solder iron to complete the joint.


41/55

41

De-soldering and Re-soldering:

There may be cases where a soldered PCB may be taken for re-soldering.

The problem is that the solder that is already used has some dissolved base metals that make

it unfit for reuse. If you try to re-solder onto it, the new solder will not properly bond with the

base metal and will cause the formation of a brittle cold solder joint with a crystalline

appearance.

So,before re-soldering it is good practice to de-solder and thus remove the

solder from the joint. For this purpose there are de-soldering equipments called solder

suckers. By doing this a lot of flux is released which will clear the dissolved base metals and

all other contaminants from the copper trace. Thus a bright, shiny, clean junction will be

ready to be re-soldered.


42/55

42

7.CIRCUIT CONSTRUCTION

Connect the transformer (12-0-12) to the three terminal bases. Connect the

diodes, capacitors and IC 7805 according to the given 5v power supply as shown below:

Connect the IR Leds parallel in series with the 330 ohms resistors. Connect the anode

of Leds to + 5v power supply by means of resistors so as to prevent Leds from d amage.

Connect the cathode of Leds to ground.

Now, connect the photo diodes in reverse bias mode so as the cathode is connected to

+5v power supply with the help of series resistor (10K-ohm) and the anode is connected to

ground terminal. The corresponding outputs from photo diodes are given to the octal buffer

i.e., IC1 74LS244 to store the energy and to drive the various Leds connected at particular

pins.

Here for IC1 we consider the input pins are: 2, 4, 6 and the corresponding output pins

are: 18, 9, and 5 respectively. The 10 pin connected to ground and the 20 pin connected to

+5v power supply.

The output pins of the octal buffer are given to IC2 ULN 2003 (relay driver) to drive

the relays. The input pins of IC2 are: 1, 5, 7 and the corresponding output pins are: 16, 12,

and 10 respectively. These outputs are connected to relays.

The red Leds are connected to the output of IC1 pins.


43/55

43

8.CIRCUIT DESCRIPTION

The circuit presented here can be used as a lock for importantelectronic/electrical appliances. When card is inserted inside its mechanism, depending upon

the position of punched hole on the card, a particular appliance would be switched on. The

card is inserted just like a floppy disk inside the disk drive. The circuit uses three photo

diodes. When there is no card in the lock, the system remains idle. The IC 74LS244 is active

enabled. The optical sensor unit constructed by using an infrared LED in conjunction with a

matched photo detector (photo diodes) makes the system insensitive to ambient light. Hence

system constitutes negligible noise source as the operating wavelength falls out of the visible

spectrum. The ciruit will be enabled only when there is a continuous radiation from infrared

Led to photo diode.

You can make these cards using a black, opaque plastic sheet or any insulator material

which obstructs the infrared rays to reach photodiodes. A small rectangular notch is made on

this card to indicate proper direction for insertion of the card. When card for any appliance

(say appliance 1) is completely inserted in the mechanism, the particular RED LEDs are

turned on and at the output side particular Led is made to ON. The operation starts as a card

is inserted into the system, the particular photodiode which is unable to detect the radiation

sensed from the corresponding infrared led drives high the IC1 74LS244 integrated circuit

(line driver/ buffer). As the IC output is connected to leds (red and green) respective leds

will turned on.

And the IC2 ULN2003 connected to the output of IC1 used to drive the relays. In this

circuit IC1 (74LS244) is used as buffer with Schmitt trigger. The outputs of this IC1 are

connected to IC2 (ULN2003) which is used as relay driver. IC2 consists of seven high current

relay drivers having integral diodes.

When an input of this IC is made logic high, the corresponding output will go logic

low and relay connected to that pin gets energized. This switches on a specific appliance and

the corresponding LED. Once a specific card is inserted to switch on a specific relay, that

relay gets latched through its second pair of contacts. The only way to reenergize a latched

relay after removal of the corresponding card is to switch off the corresponding switch which

would cut-off the supply to the desired relay.

The +5V and +12V supplies can be obtained with conventional arrangement using a

step-down transformer followed by rectifier, filter and regulator (using 7805 and 7812 etc).


44/55

44

9.POWER SUPPLY

To make things really simple lets start with a simple

power supply ,and it is also the one they usually give you in your first electronics

project.Well the reason is quite obvious because all electronics circuits require a DC power

supply to work.You really do plug in the wires of your electronic items in AC mains supply

but they do have AC to DC converters to to provide DC to the circuits .All this is done with a

power supply in the right place.

This circuit is a small +5V power supply .The circuit will provide a regulated

voltage to the external circuit which may also I am required in any part of the external circuit

or the whole external circuit .The best part is that you can also use it to convert AC voltage toDC and then regulate it , simply you need a transformer to make the AC main drop down to a

safe value i.e., 12-15 volts and then us a rectifier to convert AC into DC.

This circuit can give +5V output at about 150 mA current, but it can be increased

to 1 A when good cooling is added to 7805 regulator chip.

The circuit has over overload and terminal protection. The capacitors must have

enough high voltage rating to safely handle the input voltage feed to circuit. The circuit is

very easy to build for example into a piece of veroboard.

If you need other voltages than +5V, you can modify the circuit by replacing the

7805 chips with another regulator with different output voltage from regulator 78xx chip

family. The last numbers in the the chip code tells the output voltage. Remember that the

input voltage must be atleast 3V greater than regulator output voltage ot otherwise the

regulator does not work well.

The power supply in the circuit uses a transformer, rectifier and a regulator as shown

Figure 9.1:power supply circuit


45/55

45

Summary of circuit features:

Brief description of operation: Gives out well regulated +5V output, output currentcapability of 100 mA.

Circuit protection: Built-in overheating protection shuts down output when regulator ICgets too hot.

Circuit complexity: Very simple and easy to build. Circuit performance: Very stable +5V output voltage, reliable operation. Availability of components: Easy to get, uses only very common basic components. Design testing: Based on datasheet example circuit, I have used this circuit succesfully as

part of many electronics projects.

Applications: Part of electronics devices, small laboratory power supply. Power supply voltage: Unreglated DC 8-18V power supply. Power supply current: Needed output current + 5 mA. Component costs: Few dollars for the electronics components + the input transformer cost.
http://www.epanorama.net/circuits/psu_5v.htmlhttp://www.epanorama.net/circuits/psu_5v.htmlhttp://www.epanorama.net/circuits/psu_5v.htmlhttp://www.epanorama.net/circuits/psu_5v.htmlhttp://www.epanorama.net/circuits/psu_5v.htmlhttp://www.epanorama.net/circuits/psu_5v.html


46/55

46

10.APPLICATIONS

This project is a simple version of card lock system where the advanced versions of thismay lead to vast applications in modern technological world.

These are highly secured devices, hence these may used in banks asSafe DepositLockers.

These are very easily operated ,hence used in any lock system like car door lockingpurpose, home appliances for door locks.

Advantages of Electronic Access Control: An electronic access control system

offers several advantages over traditional locks and keys. Here are some of the most

important to keep in mind when considering your access control options:

1) Electronic Keys are Difficult to Duplicate

While physical keys can be copied very easily, duplicating electronic keys requires a

much higher degree of sophistication. This makes your access system much more secure than

it could ever be with physical keys.

2) You NEVER have to Change the Locks:

An electronic user database means that you never have to change locks at your sites.

If a keycard is ever lost, it can be immediately removed from the database and a new one can

be issued. If an employee leaves your company, his or her access rights can be deleted within

seconds. This greatly lowers your overall exposure to risk.

3) You Only Have to Remember One Key:

With electronic access, your single key or access code grants you access to every door

you need to access, so there's no chance of forgetting the key for a particular door. If you get

to a site where you need access and you are not recognized by the system, a network operator

can add you or your supervisor to the list instantly.
http://www.axisbank.com/webforms/applyonline.asp?ucode=Personal&ccode=OtherServices&pcode=lockers&Applytitle=Apply%20Onlinehttp://www.axisbank.com/webforms/applyonline.asp?ucode=Personal&ccode=OtherServices&pcode=lockers&Applytitle=Apply%20Onlinehttp://www.axisbank.com/webforms/applyonline.asp?ucode=Personal&ccode=OtherServices&pcode=lockers&Applytitle=Apply%20Onlinehttp://www.axisbank.com/webforms/applyonline.asp?ucode=Personal&ccode=OtherServices&pcode=lockers&Applytitle=Apply%20Onlinehttp://www.axisbank.com/webforms/applyonline.asp?ucode=Personal&ccode=OtherServices&pcode=lockers&Applytitle=Apply%20Online


47/55

47

11.RESULT

The assembly of Electronic card lock system is taking up with care, real and

full of responsible. Incorporating the various components as per the circuit diagram on the

printed circuit board solders the unit. After the assembly it is tested as per the design and

specifications. By doing this project we have gained some knowledge about various

components and there operations in practical. We learned many things about various basic

components and uses of them. The electronic card lock system is used for various appliances

by using certain cards.


48/55

48

12.CONCLUSION

This project is a simplest version of Electronic Card lock system where the

advanced versions lead to the vast applications in the technological world .By using

this system we can increase the security and prevent the unauthorized persons from

opening the lock.


49/55

49

13.BIBLIOGRAPHY

TEXT BOOKS:

Op-Amps and Linear Integrated Circuits

- Ramakant A. Gayakwad .

Linear integrated circuits

-D. Roy Choudhury, B. Jain.

Integrated Electronics

-Jacob Millman, Christos C. Halkias.

WEBSITES:

Electronics For You.

http://en.wikipedia.org/wiki/Main_Page

http://www.learn-c.com.

http://www.kpsec.freeuk.com.
http://books.google.co.in/books/about/Op_amps_and_linear_integrated_circuits.html?id=KXweAQAAIAAJhttp://books.google.co.in/books/about/Op_amps_and_linear_integrated_circuits.html?id=KXweAQAAIAAJhttp://www.google.co.in/search?tbo=p&tbm=bks&q=inauthor:%22D.+Roy+Choudhury%22http://www.google.co.in/search?tbo=p&tbm=bks&q=inauthor:%22D.+Roy+Choudhury%22http://www.google.co.in/search?tbo=p&tbm=bks&q=inauthor:%22B.+Jain%22http://www.google.co.in/search?hl=en&sa=G&tbo=1&tbm=bks&tbm=bks&q=inauthor:%22Jacob+Millman%22&ei=jXfvTo-qN8jsrAfI-cWQCQ&ved=0CD0Q9Aghttp://www.google.co.in/search?hl=en&sa=G&tbo=1&tbm=bks&tbm=bks&q=inauthor:%22Jacob+Millman%22&ei=jXfvTo-qN8jsrAfI-cWQCQ&ved=0CD0Q9Aghttp://www.google.co.in/search?hl=en&sa=G&tbo=1&tbm=bks&tbm=bks&q=inauthor:%22Jacob+Millman%22&q=inauthor:%22Christos+C.+Halkias%22&ei=jXfvTo-qN8jsrAfI-cWQCQ&ved=0CD4Q9Aghttp://en.wikipedia.org/wiki/Main_Pagehttp://www.learn-c.com/74ls244.pdfhttp://www.kpsec.freeuk.com/http://www.kpsec.freeuk.com/http://www.learn-c.com/74ls244.pdfhttp://en.wikipedia.org/wiki/Main_Pagehttp://www.google.co.in/search?hl=en&sa=G&tbo=1&tbm=bks&tbm=bks&q=inauthor:%22Jacob+Millman%22&q=inauthor:%22Christos+C.+Halkias%22&ei=jXfvTo-qN8jsrAfI-cWQCQ&ved=0CD4Q9Aghttp://www.google.co.in/search?hl=en&sa=G&tbo=1&tbm=bks&tbm=bks&q=inauthor:%22Jacob+Millman%22&ei=jXfvTo-qN8jsrAfI-cWQCQ&ved=0CD0Q9Aghttp://www.google.co.in/search?tbo=p&tbm=bks&q=inauthor:%22B.+Jain%22http://www.google.co.in/search?tbo=p&tbm=bks&q=inauthor:%22D.+Roy+Choudhury%22http://books.google.co.in/books/about/Op_amps_and_linear_integrated_circuits.html?id=KXweAQAAIAAJ


50/55

50

http://www.scitec.uk.com/irleds/notes.php

http://www.datasheetarchive.com
http://www.scitec.uk.com/irleds/notes.phphttp://www.datasheetarchive.com/http://www.datasheetarchive.com/http://www.datasheetarchive.com/http://www.scitec.uk.com/irleds/notes.php


51/55

51


52/55

52


53/55

53


54/55

54


55/55

electronic cardlock system

Documents