Project report

on

emergency light

Submitted to:

Submitted by:

Description and Working:Automatic lamp control is our minor project. We can use this system as our stydy lamp

table.we are using a relay derive circuit at the ouput side. We can also take an example of

LED. In this project we are tried make LED lamp using leds and DC power supply. We

made 5v DC regulated supply for this purpose. An LED lamp (LED light bulb) is a solid-

state lamp that uses light-emitting diodes (LEDs) as the source of light. The LEDs

involved may be conventional semiconductor light-emitting diodes, to organic LEDs

(OLED), or polymer light-emitting diodes (PLED) devices, although PLED technologies

are not currently commercially available.

Since the light output of individual light-emitting diodes is small compared to

incandescent and compact fluorescent lamps, multiple diodes are often used together. In

recent years, as diode technology has improved, high power light-emitting diodes with

higher lumen output are making it possible to replace other lamps with LED lamps. One

high power LED chip used in some commercial LED lights can emit 7,527 lumens while

using only 100 watts. LED lamps can be made interchangeable with other types of lamps.

Diodes use direct current (DC) electrical power, so LED lamps must also include internal

circuits to operate from standard AC voltage. LEDs are damaged by being run at higher

temperatures, so LED lamps typically include heat management elements such as heat

sinks and cooling fins. LED lamps offer long service life and high energy efficiency, but

initial costs are higher than those of fluorescent lamps.

This circuit is a small +05 volts power supply, which is useful when experimenting with

digital electronics. Small inexpensive wall transformers with variable output voltage are

available from any electronics shop. Those transformers are easily available, but usually

their voltage regulation is very poor, which makes them not very usable for digital circuit

experimenter unless a better regulation can be achieved in some way. The following

circuit is the answer to the problem.

This circuit can give +05V output at about 1A current. The circuit has overload and

terminal protection.

Summary of circuit features

Brief description of operation: Gives out well regulated +5V output, output

current capability of 700 mA.

Circuit protection: Built-in overheating protection shuts down output when

regulator IC gets too hot.

Circuit complexity: Simple and easy to build.

Circuit performance: Stable +9V output voltage, reliable operation.

Availability of components: Easy to get, uses only common basic components.

Design testing: Based on datasheet example circuit, I have used this circuit

successfully as part of other electronics projects.

Applications: Part of electronics devices, small laboratory power supply.

Power supply voltage: Unregulated DC 5-18V power supply.

Power supply current: Needed output current 1A.

Components cost: Few rupees for the electronic components plus the cost of input

transformer.

Circuit diagram of power supply

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Component list

1. IN4007 Diodes

2. 7805 regulator IC.

3. 1000 uf electrolytic capacitor, at least 25V voltage rating.

4. 470 uf electrolytic capacitor, at least 25V voltage rating.

5. 470 Ohms Resistance

6. LED

We are using center taped full wave rectifier and Pi- filter for filtering.

Component Description1) Voltage Regulator LM7805:

The above circuit utilizes the voltage regulator IC 7805 for the constant power supply.

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 Vero board.

1 2 3

Pin diagram of 7805regulator IC

PIN 1 : Unregulated voltage input

PIN 2 : Ground

PIN 3 : Regulated voltage output

2) About Rectifiers

A rectifier is an electrical device that converts alternating current (AC) to direct current

(DC), a process known as rectification. Rectifiers have many uses including as

components of power supplies and as detectors of radio signals. Rectifiers may be made

of solid state diodes, vacuum tube diodes, mercury arc valves, and other components.

A device which performs the opposite function (converting DC to AC) is known as an

inverter.

When only one diode is used to rectify AC (by blocking the negative or positive portion

of the waveform), the difference between the term diode and the term rectifier is merely

one of usage, i.e., the term rectifier describes a diode that is being used to convert AC to

DC. Almost all rectifiers comprise a number of diodes in a specific arrangement for more

efficiently converting AC to DC than is possible with only one diode. Before the

development of silicon semiconductor rectifiers, vacuum tube diodes and copper(I) oxide

or selenium rectifier stacks were used.

Early radio receivers, called crystal radios, used a "cat's whisker" of fine wire pressing on

a crystal of galena (lead sulfide) to serve as a point-contact rectifier or "crystal detector".

Rectification may occasionally serve in roles other than to generate D.C. current per se.

For example, in gas heating systems flame rectification is used to detect presence of

flame. Two metal electrodes in the outer layer of the flame provide a current path, and

rectification of an applied alternating voltage will happen in the plasma, but only while

the flame is present to generate it.

Half-wave rectification

In half wave rectification, either the positive or negative half of the AC wave is passed,

while the other half is blocked. Because only one half of the input waveform reaches the

output, it is very inefficient if used for power transfer. Half-wave rectification can be

achieved with a single diode in a one-phase supply, or with three diodes in a three-phase

supply. The output DC voltage of a half wave rectifier can be calculated with the

following two ideal equations.

Full-wave rectification

A full-wave rectifier converts the whole of the input waveform to one of constant polarity

(positive or negative) at its output. Full-wave rectification converts both polarities of the

input waveform to DC (direct current), and is more efficient. However, in a circuit with a

non-center tapped transformer, four diodes are required instead of the one needed for

half-wave rectification. (See semiconductors, diode). Four diodes arranged this way are

called a diode bridge or bridge rectifier:

Graetz bridge rectifier: a full-wave rectifier using 4 diodes.

For single-phase AC, if the transformer is center-tapped, then two diodes back-to-back

(i.e. anodes-to-anode or cathode-to-cathode) can form a full-wave rectifier. Twice as

many windings are required on the transformer secondary to obtain the same output

voltage compared to the bridge rectifier above.

Full-wave rectifier using a transformer and 2 diodes.

Full-wave rectifier, with vacuum tube having two anodes.

A very common vacuum tube rectifier configuration contained one cathode and twin

anodes inside a single envelope; in this way, the two diodes required only one vacuum

tube. The 5U4 and 5Y3 were popular examples of this configuration.

A three-phase bridge rectifier.

3-phase AC input, half & full wave rectified DC output waveforms

For three-phase AC, six diodes are used. Typically there are three pairs of diodes, each

pair, though, is not the same kind of double diode that would be used for a full wave

single-phase rectifier. Instead the pairs are in series (anode to cathode). Typically,

commercially available double diodes have four terminals so the user can configure them

as single-phase split supply use, for half a bridge, or for three-phase use.

Disassembled automobile alternator, showing the six diodes that comprise a full-wave

three-phase bridge rectifier.

Most devices that generate alternating current (such devices are called alternators)

generate three-phase AC. For example, an automobile alternator has six diodes inside it

to function as a full-wave rectifier for battery charging applications.

3) About filters

Electronic filters are electronic circuits which perform signal processing functions,

specifically intended to remove unwanted signal components and/or enhance wanted

ones. Electronic filters can be:

passive or active

analog or digital

discrete-time (sampled) or continuous-time

linear or non-linear

infinite impulse response (IIR type) or finite impulse response (FIR type)

The most common types of electronic filters are linear filters, regardless of other aspects

of their design. See the article on linear filters for details on their design and analysis.

History

The oldest forms of electronic filters are passive analog linear filters, constructed using

only resistors and capacitors or resistors and inductors. These are known as RC and RL

single pole filters respectively. More complex multipole LC filters have also existed for

many years and the operation of such filters is well understood with many books having

been written about them.

Hybrid filters have also been made, typically involving combinations of analog amplifiers

with mechanical resonators or delay lines. Other devices such as CCD delay lines have

also been used as discrete-time filters. With the availability of digital signal processing,

active digital filters have become common.

Classification by technology

Passive filters

Passive implementations of linear filters are based on combinations of resistors (R),

inductors (L) and capacitors (C). These types are collectively known as passive filters,

because they do not depend upon an external power supply.

Inductors block high-frequency signals and conduct low-frequency signals, while

capacitors do the reverse. A filter in which the signal passes through an inductor, or in

which a capacitor provides a path to earth, presents less attenuation to low-frequency

signals than high-frequency signals and is a low-pass filter. If the signal passes through a

capacitor, or has a path to ground through an inductor, then the filter presents less

attenuation to high-frequency signals than low-frequency signals and is a high-pass filter.

Resistors on their own have no frequency-selective properties, but are added to inductors

and capacitors to determine the time-constants of the circuit, and therefore the

frequencies to which it responds.

At very high frequencies (above about 100 Megahertz), sometimes the inductors consist

of single loops or strips of sheet metal, and the capacitors consist of adjacent strips of

metal. These inductive or capacitive pieces of metal are called stubs.

The inductors and capacitors are the reactive elements of the filter. The number of

elements determines the order of the filter. In this context, an LC tuned circuit being used

in a band-pass or band-stop filter is considered a single element even though it consists of

two components.

Single element types

The simplest passive filters consist of a single reactive element. These are constructed of

RC, RL, LC or RLC elements.

The quality or "Q" factor is a measure that is sometimes used to describe simple band-

pass or band-stop filters. A filter is said to have a high Q if it selects or rejects a range of

frequencies that is narrow in comparison to the centre frequency. Q may be defined as the

ratio of centre frequency divided by 3dB bandwidth. It is not commonly employed with

higher order filters where other parameters are of more concern.

4) Diode

A diode is an electrical device allowing current to move through it in one direction with

far greater ease than in the other. The most common kind of diode in modern circuit

design is the semiconductor diode, although other diode technologies exist.

Semiconductor diodes are symbolized in schematic diagrams such as Figure below. The

term “diode” is customarily reserved for small signal devices, I ≤ 1 A. The term rectifier

is used for power devices, I > 1 A.

Semiconductor diode schematic symbol: Arrows indicate the direction of electron current

flow.

When placed in a simple battery-lamp circuit, the diode will either allow or prevent

current through the lamp, depending on the polarity of the applied voltage. (Figure

below)

Diode operation: (a) Current flow is permitted; the diode is forward biased. (b) Current

flow is prohibited; the diode is reversed biased.

When the polarity of the battery is such that electrons are allowed to flow through the

diode, the diode is said to be forward-biased. Conversely, when the battery is “backward”

and the diode blocks current, the diode is said to be reverse-biased. A diode may be

thought of as like a switch: “closed” when forward-biased and “open” when reverse-

biased. Oddly enough, the direction of the diode symbol's “arrowhead” points against the

direction of electron flow. This is because the diode symbol was invented by engineers,

who predominantly use conventional flow notation in their schematics, showing current

as a flow of charge from the positive (+) side of the voltage source to the negative (-).

This convention holds true for all semiconductor symbols possessing “arrowheads:” the

arrow points in the permitted direction of conventional flow, and against the permitted

direction of electron flow.

Diode behavior is analogous to the behavior of a hydraulic device called a check valve. A

check valve allows fluid flow through it in only one direction as in Figure below.

Hydraulic check valve analogy: (a) Electron current flow permitted. (b) Current flow

prohibited.

Check valves are essentially pressure-operated devices: they open and allow flow if the

pressure across them is of the correct “polarity” to open the gate (in the analogy shown,

greater fluid pressure on the right than on the left). If the pressure is of the opposite

“polarity,” the pressure difference across the check valve will close and hold the gate so

that no flow occurs. Like check valves, diodes are essentially “pressure-” operated

(voltage-operated) devices. The essential difference between forward-bias and reverse-

bias is the polarity of the voltage dropped across the diode. Let's take a closer look at the

simple battery-diode-lamp circuit shown earlier, this time investigating voltage drops

across the various components in Figure below.

Diode circuit voltage measurements: (a) Forward biased. (b) Reverse biased.

A forward-biased diode conducts current and drops a small voltage across it, leaving

most of the battery voltage dropped across the lamp. If the battery's polarity is reversed,

the diode becomes reverse-biased, and drops all of the battery's voltage leaving none for

the lamp. If we consider the diode to be a self-actuating switch (closed in the forward-

bias mode and open in the reverse-bias mode), this behavior makes sense. The most

substantial difference is that the diode drops a lot more voltage when conducting than the

average mechanical switch (0.7 volts versus tens of millivolts).

This forward-bias voltage drop exhibited by the diode is due to the action of the depletion

region formed by the P-N junction under the influence of an applied voltage. If no

voltage applied is across a semiconductor diode, a thin depletion region exists around the

region of the P-N junction, preventing current flow. (Figure below (a)) The depletion

region is almost devoid of available charge carriers, and acts as an insulator:

Diode representations: PN-junction model, schematic symbol, physical part.

The schematic symbol of the diode is shown in Figure above (b) such that the anode

(pointing end) corresponds to the P-type semiconductor at (a). The cathode bar, non-

pointing end, at (b) corresponds to the N-type material at (a). Also note that the cathode

stripe on the physical part (c) corresponds to the cathode on the symbol.

If a reverse-biasing voltage is applied across the P-N junction, this depletion region

expands, further resisting any current through it. (Figure below)

Depletion region expands with reverse bias.

Conversely, if a forward-biasing voltage is applied across the P-N junction, the depletion

region collapses becoming thinner. The diode becomes less resistive to current through it.

In order for a sustained current to go through the diode; though, the depletion region must

be fully collapsed by the applied voltage. This takes a certain minimum voltage to

accomplish, called the forward voltage as illustrated in Figure below.

Inceasing forward bias from (a) to (b) decreases depletion region thickness.

For silicon diodes, the typical forward voltage is 0.7 volts, nominal. For germanium

diodes, the forward voltage is only 0.3 volts. The chemical constituency of the P-N

junction comprising the diode accounts for its nominal forward voltage figure, which is

why silicon and germanium diodes have such different forward voltages. Forward voltage

drop remains approximately constant for a wide range of diode currents, meaning that

diode voltage drop is not like that of a resistor or even a normal (closed) switch. For most

simplified circuit analysis, the voltage drop across a conducting diode may be considered

constant at the nominal figure and not related to the amount of current.

5) Resistor

A resistor is a two-terminal passive electronic component which implements electrical

resistance as a circuit element. When a voltage V is applied across the terminals of a

resistor, a current I will flow through the resistor in direct proportion to that voltage. The

reciprocal of the constant of proportionality is known as the resistance R, since, with a

given voltage V, a larger value of R further "resists" the flow of current I as given by

Ohm's law:

Resistors are common elements of electrical networks and electronic circuits and are

ubiquitous in most electronic equipment. Practical resistors can be made of various

compounds and films, as well as resistance wire (wire made of a high-resistivity alloy,

such as nickel-chrome). Resistors are also implemented within integrated circuits,

particularly analog devices, and can also be integrated into hybrid and printed circuits.

The electrical functionality of a resistor is specified by its resistance: common

commercial resistors are manufactured over a range of more than 9 orders of magnitude.

When specifying that resistance in an electronic design, the required precision of the

resistance may require attention to the manufacturing tolerance of the chosen resistor,

according to its specific application. The temperature coefficient of the resistance may

also be of concern in some precision applications. Practical resistors are also specified as

having a maximum power rating which must exceed the anticipated power dissipation of

that resistor in a particular circuit: this is mainly of concern in power electronics

applications. Resistors with higher power ratings are physically larger and may require

heat sinking. In a high voltage circuit, attention must sometimes be paid to the rated

maximum working voltage of the resistor.

The series inductance of a practical resistor causes its behavior to depart from ohms law;

this specification can be important in some high-frequency applications for smaller

values of resistance. In a low-noise amplifier or pre-amp the noise characteristics of a

resistor may be an issue. The unwanted inductance, excess noise, and temperature

coefficient are mainly dependent on the technology used in manufacturing the resistor.

They are not normally specified individually for a particular family of resistors

manufactured using a particular technology.[1] A family of discrete resistors is also

characterized according to its form factor, that is, the size of the device and position of its

leads (or terminals) which is relevant in the practical manufacturing of circuits using

them.

6) Capacitor

A capacitor (formerly known as condenser) is a passive electronic component consisting

of a pair of conductors separated by a dielectric (insulator). When there is a potential

difference (voltage) across the conductors, a static electric field develops in the dielectric

that stores energy and produces a mechanical force between the conductors. An ideal

capacitor is characterized by a single constant value, capacitance, measured in farads.

This is the ratio of the electric charge on each conductor to the potential difference

between them.

Capacitors are widely used in electronic circuits for blocking direct current while

allowing alternating current to pass, in filter networks, for smoothing the output of power

supplies, in the resonant circuits that tune radios to particular frequencies and for many

other purposes.

The effect is greatest when there is a narrow separation between large areas of conductor,

hence capacitor conductors are often called "plates", referring to an early means of

construction. In practice the dielectric between the plates passes a small amount of

leakage current and also has an electric field strength limit, resulting in a breakdown

voltage, while the conductors and leads introduce an undesired inductance and resistance.

7) LED

A light-emitting diode (LED) (pronounced /ˌ ɛ l iː ˈdiː/ , L-E-D[1]) is a semiconductor light

source. LEDs are used as indicator lamps in many devices, and are increasingly used for

lighting. Introduced as a practical electronic component in 1962,[2] early LEDs emitted

low-intensity red light, but modern versions are available across the visible, ultraviolet

and infrared wavelengths, with very high brightness. When a light-emitting diode is

forward biased (switched on), electrons are able to recombine with electron 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. An LED is often small in area

(less than 1 mm2), and integrated optical components may be used to shape its radiation

pattern.[3] LEDs present many advantages over incandescent light sources including lower

energy consumption, longer lifetime, improved robustness, smaller size, faster switching,

and greater durability and reliability. LEDs powerful enough for room lighting are

relatively expensive and require more precise current and heat management than compact

fluorescent lamp sources of comparable output.

Light-emitting diodes are used in applications as diverse as replacements for aviation

lighting, automotive lighting (particularly brake lamps, turn signals and indicators) as

well as in traffic signals.

TRANSISTOR (BC558)

A transistor is semi conductor device consisting of three regions

separated by two P-N junctions. The three regions are Base, Emitter &

Collector.

The base may be of N- type or P- type. The emitter and collector have

same impurities but different from that of base. Thus if base is of N- type

then emitter and collector are of P- type then transistor is called P-N-P

transistor and vice versa transistor is called N-P-N transistor.

The base is made thin and number density of majority carriers is

always less than emitter and collector. The base provides junction for proper

interaction between emitter and collector.

Electrons are majority charge carriers in N- region and in P-region,

holes are the majority charge carriers. Thus two types of charge carriers are

involved in current flow through N-P-N or P-N-P transistor.

SYMBOLS FOR TRANSISTORS :

In schematic symbols, the emitter is always represented by an arrow

indicating the direction of conventional current in the device.

In case of N-P-N transistor arrow points away from base and in case

of P-N-P transistor it points towards base.

When transistor is used in circuit, emitter - base junction is always

forward biased while base - collector junction is always reverse biased.

Fig. Structure and symbol of P-N-P transistor

BIASING OF TRANSISTOR :

The two junctions can be biased in four different ways:

Both junctions may be forward biased. It causes large current to flow

across junctions. Transistor is to be operated in “SATURATION

REGION”.

Both junctions may be reversed biased. It causes very small current to

flow across junctions. Transistor is to be operated in “CUT OFF

REGION”.

E-B junction is forward biased and C-B junction is reverse biased.

The transistor is said to be operated in “ACTIVE REGION”. Most of

the transistors work in this region.

E-B junction is reversed biased and C-B junction is forward biased.

The transistor is said to be operated in “INVERTED MODE”.

Fig. (a) P-N-P transistor biasing (b) N-P-N transistor biasing

CIRCUIT CONFIGURATIONS :

There are three possible ways in which a transistor can be connected

in the circuit which are following :

Common Base Configuration : Base is made common in this

configuration.

Common Emitter Configuration : Emitter is made common in this

configuration.

Common Collector Configuration : Collector is made common in this

configuration.

Fig. PNP Common Base Configuration

Fig. PNP Common Emitter Fig. NPN Common Collector

Configuration Configuration

BC558

Absolute Maximum Rating : Ta = 25°C unless otherwise noted

Parameter Symbol Value

Collector – Emitter Voltage VCEO -30

Collector – Base Voltage VCBO -30

Emitter – Base Voltage VEBO -5

Collector Current (DC) IC -100

Collector Dissipation PC 500

Junction Temperature TJ 150

Storage Temperature TSTG -65 to 150

Electrical Characteristics : Ta = 25°C unless otherwise noted

Parameter Symbol Test Condition Min. Type

Collector Cut-off Current ICBO VCB = -30V, IE=0

DC Current Gain hfe VCB = -5V, IC=2mA 110

Collector Emitter Saturation

Voltage

VCE(sat) IC= -10mA, IB= -0.5mA

IC= -100mA, IB= -5mA

-90

-250

Collector Base Saturation

Voltage

VBE(sat) IC= -10mA, IB= -0.5mA

IC= -100mA, IB= -5mA

-700

-900

Base Emitter On Voltage VBE(On) VCE= -5V, IC= -2mA

VCE= -5V, IC= -10mA

-600 -660

Current Gain Bandwidth

Product

fT VCE= -5V, IC= -10mA,

f=10MHz

150

Output Capacitance Cob VCB= -

10V,IE=0,f=1MHz

Noise Figure NF VCE= -5V, IC= -200mA 2

DIODE

It is a P-type region and N-type region formed in the same crystal

structure, and hence a P-N junction is produced. Some of the conduction

electrons near the junction diffuse in to P-type semiconductor from the N-type

semiconductor across the junction combing with the holes. The loss of

electrons makes the N-type semiconductor positively charged and hence the

neutralization of the holes on the other hand makes P-type semiconductor

negatively charged. This region where positive and negative charges develop is

called depletion region.

Fig. Diode

If a P-region is made positive with respect to the N-region by an external

circuit then junction is forward biased and junction has a very low resistance to

the flow of current. Holes in the positive P-type material are attracted across the

junction to the negative side and the free electrons in the N-type material are

like wise attracted to the opposite side. If a positive voltage is applied to N-

zone with respect to the P-zone terminal, the P-N junction is reverse biased.

Fig. Volt-Ampere Characteristics of a P-N Diode

Temperature Dependence of V-I Characteristics

The cut-in voltage decreases at the rate of 2.5 mV/°C. Also above 25°C,

the reverse saturation current I0 doubles for every 6°C (10°C) for Si (Ge)

diodes. However, the shape of overall characteristic does not alter with

temperature.

Diode Resistance

Static Resistance : The static resistance of a diode denoted by R is the ratio

of diode voltage V to diode current I. The static resistance R varies

widely as the operating point shifts and it does not constitute a useful

parameter.

Dynamic or Incremental Resistance : The dynamic resistance of a diode

is defined as the reciprocal of the slope of the current voltage

characteristic. Thus dynamic resistance is given by -

r dV/dI …………(1)

The dynamic resistance forms an important parameter for small

signal operation of the diode. The dynamic resistance, however, is not a

constant but varies with the operating point.

For a semiconductor diode, the dynamic resistance r as per V-I

characteristic is given by,

r dV/dI = VT/I0V/VT = VT/(I+I0) ……….(2)

If the reverse bias is greater than a few tenth of a volt, then

V/V >>1 and r is extremely large.

For forward bias exceeding a few tenths of volt, I>>I0, so that

r = VT/I ……..(3)

Thus dynamic forward resistance varies inversely as the current I.

At room temperature, i.e.

T = 300°K, for = 1.

R = 26/I ……..(4)

where r is in ohms and I is in milli-amperes.

Depletion Layer Capacitance (Transition Capacitance) CT

The width W of the depletion layer at the junction increases with the

increase of reverse bias magnitude. This depletion region along with the

concentration of uncovered immobile charges constitutes a capacitor whose

incremental capacitance CT is given by,

CT = dQ/dV

where dQ is the increase in charge resulting from a change dV in

voltage. Hence a voltage change dV in time interval dt will result in a current i

given by,

i = dQ/dt ……..(5)

CT = dV/dt ……..(6)

LIGHT EMITTING DIODE

LED falls within the family of P-N junction devices. The light emitting

diode (LED) is a diode that will give off visible light when it is energized. In

any forward biased P-N junction there is, within the structure and primarily

close to the junction, a recombination of holes and electrons. This

recombination requires that the energy possessed by the unbound free electron

be transferred to another state.

The process of giving off light by applying an electrical source of energy

is called electroluminescence. As shown in fig., with its graphic symbol, the

conducting surface connected to the P-material is much smaller, to permit the

emergence of the maximum number of photons of light energy. Note in the

figure that the recombination of the injected carriers due to the forward-biased

junction results in emitted light at the site of recombination. There may, of

course, be some absorption of the packages of photon energy in the structure

itself, but a very large percentage are able to leave, as shown in the fig.

Fig. Process of electroluminescence in the LED

Absolute Maximum Ratings at TA = 25°C

Parameter High Eff. Red 4160 Units

Power dissipation 120 mW

Average forward current 20[1] mA

Peak forward current 60 mA

Operating and storage temperature range -55°C to 100°C

Lead soldering temperature

[1.6mm (0.063 in.) from body]

230°C for 3 seconds

[1] Derate from 50°C at 0.2 mA/°C

Electrical/Optical Characteristics at TA = 25°C

Parameter Symbol High Eff. Red 4160 Units Test

Conditions

Min. Type Max

Axial luminous intensity Iv 1.0 3.0 mcd IF = 10mA

Included angle between

half luminous intensity

points

21/2 80 deg. -

Peak wave length peak 635 nm Measureme

nt at Peak

Dominant wave length d 628 nm -

Speed of response s 90 ns

Capacitance C 11 pF VF=0;

f=1 MHz

Thermal resistance JC 120 °C/W Junction to

cathode lead

at 0.79 mm

(0.031 in)

from body

Forward voltage VF 2.2 3.0 V IF = 10mA

Reverse breakdown

voltage

BVR 5.0 V IR = 100A

Luminous efficacy v 147 Lm/V -

RESISTANCE

Resistance is the electronic component used to control the current

passing through the circuit. They are calibrated in ohms. In the other words

resistance are circuit elements having the function introducing electrical

resistance into the circuit. There are three basic types :

1. Fixed Resistance

2. Rheostat

3. Potentiometer

A fixed Resistance is a two terminal resistance whose electrical

resistance is constant. A rheostat is a resistance that can be changed in

resistance value without opening the circuit to make adjustment.

potentiometer is an adjustable resistance with three terminals one each end

of the resistance element and third movable along its length.

CAPACITOR

A capacitor is a device capable of storing an electric charge (static

electricity). It consists of two metal plates separated by dielectric material.

Capacitors are available in values ranging from less than one picofarad to

thousands of microfarad. While using a capacitor it’s ratings must be carefully

observed to make certain that the potential to be applied across the capacitor is

not greater than the rated value.

TYPES OF CAPACITORS :

Depends upon the basis of dielectric used:

Air insulated & vaccum capacitors

Paper insulated capacitors

Mica capacitors

Plastic film capacitors

Ceramic capacitors

Electrolytic & tantalum capacitors

CERAMIC CAPACITOR :

In this project, 0.01 microfarad capacitor is a ceramic capacitor.

The basis of the ceramic material is mainly barium titanate or a similar

material, but other ceramic substance including hydrous silicate of magnesia or

talc are also used. The electrodes are applied in the form of silver which is

either spread or plated on to the opposite faces of a thin tube, wafer or disc

made from the ceramic material. Connecting wires are then soldered to this

deposit and the whole capacitor dipped in for a suitable coating.

Fig. Tabular and disc type ceramic capacitors

ELECTROLYTIC CAPACITOR :

In this project, 10f capacitor is an electrolytic capacitor. In this type of

capacitors, the dielectric consists of an extremely thin film of aluminum oxide

formed on one of its aluminum foil plates. Intimate contact with the other plate

is achieved by impregnating the paper between the foils with an electrolyte in

the form of viscous substance, such as ammonium borate. The sandwich is then

rolled into a cylindrical element and housed in either metallic cardboard, plastic

or ceramic protective tube.

Fig. Electrolytic and Tantalum capacitor

RELAYS

STRIP

OUT N/C

OUT N/O

SPRING

MAGNET

230V P

Error: Reference source not found

A relay is an electrically operated switch. The relay contacts can be made to

operate in the pre-arranged fashion. For instance, normally open contacts

close and normally closed contacts open. In electromagnetic relays, the

contacts however complex they might be, they have only two position i.e.

OPEN and CLOSED, whereas in case of electromagnetic switches, the

contacts can have multiple positions.

NEED FOR THE USE OF RELAY

The reason behind using relay for switching loads is to provide complete

electrical isolation. The means that there is no electrical connection between

the driving circuits and the driven circuits. The driving circuit may be low

voltage operated low power circuits that control several kilowatts of power.

In our circuit where a high fan could be switched on or off depending upon

the output from the telephone.

Since the relay circuit operated on a low voltage, the controlling circuit is

quite safe. In an electromagnetic relay the armature is pulled by a magnetic

force only. There is no electrical connection between the coil of a relay and

the switching contacts of the relay. If there are more than one contact they

all are electrically isolated from each other by mounting them on insulating

plates and washers. Hence they can be wired to control different circuits

independently.

Some of the popular contacts forms are described below:

1. Electromagnetic relay

2. Power Relay.

3. Time Delay Relay.

4. Latching Relay.

5. Crystal Can Relay.

6. Co-axial Relay.

1. Electromagnetic relay:

An electromagnetic relay in its simplest form consists of a coil, a DC current

passing through which produces a magnetic field. This magnetic field

attracts an armature, which in turn operates the contacts. Normally open

contacts close and normally closed contacts open. Electromagnetic relays are

made in a large variety of contacts forms.

2. Power relays:

Power relays are multi-pole heavy duty lapper type relays that are capable of

switching resistive loads of upto 25amp.. These relays are widely used for a

variety of industrial application like control of fractional horse power

motors, solenoids, heating elements and so on. These relays usually have

button like silver alloy contacts and the contact welding due to heavy in rush

current is avoided by wiping action of the contacts to quench the arc during

high voltage DC switching thus avoiding the contact welding.

3. Time Delay Relay:

A time delay relay is the one in which there is a desired amount of time

delay between the application of the actuating signal and operation of the

load switching devices.

4. Latching Relay:

In a Latching Relay, the relay contacts remain in the last energized position

even after removal of signal in the relay control circuit. The contacts are

held in the last relay-energized position after removal of energisation either

electrically or magnetically. The contacts can be released to the normal

position electrically or mechanically.

5. Crystal Can Relay:

They are so called, as they resemble quartz crystal in external shapes. These

are high performance hermetically sealed miniature or sub-miniature relay

widely used in aerospace and military application. These relays usually have

gold plated contacts and thus have extremely low contact resistance. Due to

low moment of inertia of the armature and also due to statically and

dynamically balanced nature of armature, these relays switch quite reliably

even under extreme condition of shock and vibration.

6. Co-axial Relay:

A Co-axial Relay has two basic parts, an actuator which is nothing but some

kind of a coil and a cavity, housing the relay contacts. The co-axial relay are

extensively used for radio frequency switching operations of equipment

THE JUNCTION TRANSISTOR

Collector Collector

Base Base

Emitter Emitter

C C

B B

E E

NPN PNP

_ _ _ _ _ _ _ _ _ _

+ + + + + _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

+ + + + + + + + + +

+ + +

+ + + + + + + + + +

+ + + + + -- -- -- --

How to control sensors

What is a voltage divider?

You are going to find out but don't be in too much of a hurry. Work through

the Chapter and allow the explanation to develop.

The diagram below shows a light dependent resistor, or LDR, together

with its circuit symbol:

The light-sensitive part of the LDR is a wavy track of cadmium sulphide.

Light energy triggers the release of extra charge carriers in this material, so

that its resistance falls as the level of illumination increases.

A light sensor uses an LDR as part of a voltage divider.

The essential circuit of a voltage divider, also called a potential divider, is:

What happens if one of the resistors in the voltage divider is replaced by an

LDR? In the circuit below, Rtop is a 10 resistor, and an LDR is used as

Rbottom :

Suppose the LDR has a resistance of 500 , 0.5 , in bright light, and 200

in the shade (these values are reasonable).

When the LDR is in the light, Vout will be:

In the shade, Vout will be:

In other words, this circuit gives a LOW voltage when the LDR is in the

light, and a HIGH voltage when the LDR is in the shade. The voltage divider

circuit gives an output voltage which changes with illumination.

A sensor subsystem which functions like this could be thought of as a 'dark

sensor' and could be used to control lighting circuits which are switched on

automatically in the evening.

Perhaps this does not seem terribly exciting, but almost every sensor circuit

you can think of uses a voltage divider. There's just no other way to make

sensor subsystems work.

Here is the voltage divider built with the LDR in place of Rtop :

Temperature sensors

A temperature-sensitive resistor is called a thermistor. There are several

different types:

The resistance of most common types of thermistor decreases as the

temperature rises. They are called negative temperature coefficient, or ntc,

thermistors. Note the -t° next to the circuit symbol. A typical ntc thermistor

is made using semiconductor metal oxide materials. (Semiconductors have

resistance properties midway between those of conductors and insulators.)

As the temperature rises, more charge carriers become available and the

resistance falls.

Although less often used, it is possible to manufacture positive temperature

coefficient, or ptc, thermistors. These are made of different materials and

show an increase in resistance with temperature.

How could you make a sensor circuit for use in a fire alarm? You want a

circuit which will deliver a HIGH voltage when hot conditions are detected.

You need a voltage divider with the ntc thermistor in the Rtop position:

How could you make a sensor circuit to detect temperatures less than 4°C to

warn motorists that there may be ice on the road? You want a circuit which

will give a HIGH voltage in cold conditions. You need a voltage divider

with the thermistor in place of Rbottom :

This last application raises an important question: How do you know what

value of Vout you are going to get at 4°C?

Key point: The biggest change in Vout from a voltage divider is obtained

when Rtop and Rbottom are equal in value

Sound sensors

Another name for a sound sensor is a microphone. The diagram shows a

cermet microphone:

Cermet' stands for 'ceramic' and 'metal'. A mixture of these materials is used

in making the sound-sensitive part of the microphone. To make them work

properly, cermet microphones need a voltage, usually around 1.5 V across

them. A suitable circuit for use with a 9 V supply is:

The 4.7 and the 1 resistors make a voltage divider which provides

1.6 V across the microphone. Sound waves generate small changes in

voltage, usually in the range 10-20 mV. To isolate these small signals from

the steady 1.6 V, a capacitor is used.

Signals from switches

When a switch is used to provide an input to a circuit, pressing the switch

usually generates a voltage signal. It is the voltage signal which triggers the

circuit into action. What do you need to get the switch to generate a voltage

signal? . . . You need a voltage divider. The circuit can be built in either of

two ways:

The pull down resistor in the first circuit forces Vout to become LOW

except when the push button switch is operated. This circuit delivers a HIGH

voltage when the switch is pressed. A resistor value of 10 is often used.

In the second circuit, the pull up resistor forces Vout to become HIGH

except when the switch is operated. Pressing the switch connects Vout

directly to 0 V. In other words, this circuit delivers a LOW voltage when the

switch is pressed.

In circuits which process logic signals, a LOW voltage is called 'logic 0' or

just '0', while a HIGH voltage is called 'logic1' or '1'. These voltage divider

circuits are perfect for providing input signals for logic systems.

What kinds of switches could you use. One variety of push button switch is

called a miniature tactile switch. These are small switches which work well

with prototype board:

SOLDERING

Soldering is the process of joining two metallic conductors the joint

where two metal conductors are to be joined or fused is heated with a device

called soldering iron and then as allow of tin and lead called solder is applied

which melts and converse the joint. The solder cools and solidifies quickly to

ensure is good and durable connection between the jointed metal converting the

joint solder also present oxidation.

SOLDERING & DESOLDERING TECHNIQUES :

There are basically two soldering techniques:

I. Manual soldering with iron.

II. Mass soldering.

The iron consist of an insulated handle connected via a metal shank to

the bit the function of bit is to

1. Stare host & convey it to the component

2. To store and deliver molten solder 7 flux.

3. To remove surplus solder from joints.

Soldering bit are made of copper because it has good heat capacity &

thermal conductivity. It may erode after long term use to avoid it coating of

nickel or tin is used.

SOLDERING WITH IRON :

The surface to be soldered must be cleaned & fluxed. The soldering iron

switched on & bellowed to attain soldering temperature. The solder in form of

wire is allied hear the component to be soldered &b heated with iron. The

surface to be soldered is filled, iron is removed & the joint is cold without

disturbing.

Solder joint are supposed to

1. Provide permanent low resistance path

2. Make a robust mechanical link between PCB & leads of components.

3. Allow heat flow between component, joining elements & PCB.

4. Retain adequate strength with temperature variation.

The following precaution should be taken while soldering.

1. Use always an iron plated copper core tip for soldering iron.

2. Slightly fore the tip with a cut file when it is cold.

3. Use a wet sponge to wipe out dirt from the tip before soldering instead of

asking the iron.

4. Tighten the tip screw if necessary before iron is connected to power

supply.

5. Clean component lead & copper pad before soldering.

6. Use proper tool for component handling instead of direct handling.

7. Apply solder between component leads, PCB pattern & tip of soldering

iron.

8. Iron should be kept in contact with the joint s for 2-3 second s only

instead of keeping for very long or very small time.

9. Use optimum quantity of solder.

10. Use multistoried wire instead of single strands solvent like isopropyl

alcohol.

11. Every time soldering is over, put a little clean solder on the tip.

Advantages :

1. Low power consumption- leds consume very less power as compare to CFL. Bulb

of 15 leds consume 150mA*1.5v only. Each led is of 1.5 v and 10mA

2. Reliablity is more- if one led will get damage even then over torch will work.

3. Low cost. LED lamp is less costly as compare to CFL.

Disadvantages-

1. Light intensity is less