ABSTRACT

Automatic Night Lamp with Morning Alarm system is a simple yet powerful

concept, which uses transistor as a switch. By using this system manual works are

100%removed. It automatically switches ON lights when the sunlight goes below the

visible region of our eyes. This is done by a sensor called Light Dependant Resistor

(LDR) which senses the light actually like our eyes. It automatically switches OFF

lights whenever the sunlight comes, visible to our eyes and activates the morning

alarm.

By using this system energy consumption is also reduced because nowadays the

manually operated street lights are not switched off even the sunlight comes and also

switched on earlier before sunset. In this project, no need of manual operation like ON

time and OFF time setting. LDR and transistor are the main components of the

project. The resistance of light dependant resistor (LDR) varies according to the light

falling on it. This LDR is connected as biasing resistor of the transistor. According to

the light falls on the LDR, the transistor is operated in saturation and cut off region.

CHAPTER 1

INTRODUCTION

Automatic Night Lamp with Morning Alarm System is a simple yet powerful

concept, which uses transistor as a switch. By using this system manual works are

100%removed. It automatically switches ON lights when the goes below the visible

region of our eyes. This is done by a sensor called Light Dependant Resistor (LDR)

which senses the light actually like our eyes. it automatically switches OFF lights

whenever the sunlight comes, visible to our eyes and activates the morning alarm

By using this system energy consumption is also reduced because nowadays the

manually operated street lights are not switched off even the sunlight comes and also

switched on earlier before sunset. In this project, no need of manual operation like ON

time and OFF time setting. LDR and transistor are the main components of the

project. The resistance of light dependant resistor (LDR) varies according to the light

falling on it. This LDR is connected as biasing resistor of the transistor. According to

the light falls on the LDR, the transistor is operated in saturation and cut off region.

This transistor switches the relay to switch on / off the light. This project uses

regulated 12V, 750mA power supply. 7812 three terminal voltage regulator is used

for voltage regulation. Bridge type full wave rectifier is used to rectify the ac output

of secondary of230/18V step down transformer.

This chapter includes the general introduction and the organization of the

project. The general introduction includes how this project is useful today and

organization of the project includes how the project is organized in chapters.

1.1 Organization of the Project

This project is organised as follows:

Chapter 1 Contains General Introduction.

Chapter 2 Consists of Description of Various Components Used.

Chapter 3 Explains Circuit Diagram and its Operation.

Chapter 4 Includes Results obtained

Chapter 5 Gives Conclusion and Future scope of the Project

CHAPTER 2

DESCRIPTION OF COMPONENTS

2.1 GENERAL THEORY

This chapter discuss about the primary components that are required to make this

project and their description in detail with necessary figures and images.

Components Needed for Making this Hidden floor switch

Resistors

capacitor

Transistor

Loud speaker

Diode

Um66IC

Transformer

IC 7806

LDR

LED

Toggle switch

IC: IC 555

9v Battery

2.2 Basic Components:

The following are the primary components used in this project.

Resistors

Capacitors

2.2.1Resistors

For designing any electronic circuit, we basically require Resistors. A Resistor

is a two-terminal electronic component that produces a voltage across its terminals

that is proportional to the electric current passing through it in accordance with Ohm‟s

law. The voltage equation according to Ohm‟s law is as follows,

V=IR

Resistors are 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).

Fig. 2.1Resistor

A resistor is a component which opposes the flow of current through it. They

are “Passive Devices”, that is they contain no source of power or amplification but

only attenuate or reduce the voltage signal passing through them. When used in DC

circuits the voltage drop produced is measured across their terminals as the circuit

current flows through them while in AC circuits the voltage and current are both in-

phase producing 0o phase shift. Generally resistance is measured in ohms.

Basically, resistors are classified depending upon their function.

Fixed Resistors.

Variable Resistors.

Fixed Resistors

Resistors whose values are fixed are called as fixed resistors. These fixed

resistors are further classified as,

Carbon Composition Resistors.

Carbon Film Resistors.

Metal Oxide Film Resistors.

Wire Wound Resistors.

The values of fixed resistors can be calculated by making use of the following:

Table 2.1 Colour Coding of Resistors

Colour 1st

band

2nd

band

3rd band

(multiplier)

4th band

(tolerance)

Temp.

Coefficient

Black 0 0 ×100

Brown 1 1 ×101 ±1% (F) 100 ppm

Red 2 2 ×102 ±2% (G) 50 ppm

Orange 3 3 ×103 15 ppm

Yellow 4 4 ×104 25 ppm

Green 5 5 ×105 ±0.5% (D)

Blue 6 6 ×106 ±0.25% (C)

Violet 7 7 ×107 ±0.1% (B)

Gray 8 8 ×108 ±0.05% (A)

White 9 9 ×109

Gold ×10−1

±5% (J)

Silver ×10−2

±10% (K)

None ±20% (M)

In this project, the resistors are used in the order of Kilo Ohms (KΩ) like 1K,

10K, and 1M Ohm resistors.

Variable Resistors

Sometimes it is necessary to have a resistor in a circuit whose value can be

changed after the circuit has been built. This might be to allow the circuit to be „fine

tuned‟ by the manufacturer, or adjusted by the user e.g. to change the volume on a

radio. The type of resistor required in this situation is called a variable resistor.

Variable resistors are often called Potentiometers in books and catalogues. They are

specified by their maximum resistance, linear or logarithmic track, and their physical

size. The standard spindle diameter is 6mm.

Fig 2.2 Internal View of Variable Resistor

Variable Resistor as Potentiometer

Variable resistors used as potentiometers have all three terminals connected.

This arrangement is normally used to vary voltage, for example to set the switching

point of a circuit with a sensor, or control the volume (loudness) in an amplifier

circuit. If the terminals at the ends of the track are connected across the power supply

then the wiper terminal will provide a voltage which can be varied from zero up to the

maximum of the supply.

Fig 2.3 PCB mounted Preset Variable Resistor (Potentiometer)

2.2.2 Capacitors

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

consisting of a pair of conductors separated by a dielectric (insulator). When a

potential difference (voltage) exists across the conductors, an electric field is present

in the dielectric. This field stores energy and produces a mechanical force between the

conductors. The effect is greatest when there is a narrow separation between large

areas of conductor; hence capacitor conductors are often called plates.

An ideal capacitor is characterized by a single constant value, capacitance,

which is measured in farads. This is the ratio of the electric charge on each conductor

to the potential difference between them. In practice, the dielectric between the plates

passes a small amount of leakage current. The conductors and leads introduce an

equivalent series resistance and the dielectric has an electric field strength limit

resulting in a breakdown voltage.

The capacitor‟s function is to store electricity, or electrical energy. The

capacitor also functions as a filter, passing alternating current (AC), and blocking

direct current (DC). This symbol „F‟ is used to indicate a capacitor in a circuit

diagram. The capacitor is constructed with two electrode plates facing each other, but

separated by an insulator. When DC voltage is applied to the capacitor, an electric

charge is stored on each electrode. While the capacitor is charging up, current flows.

The current will stop flowing when the capacitor has fully charged.

Fig 2.4 Capacitor Construction and Symbol

2.2.2.1 Types of Capacitors

Capacitors can be divided in two types based on their construction. They are:

Ceramic Capacitors

Electrolytic Capacitors

Ceramic Capacitors:

Ceramic capacitors are constructed with materials such as titanium acid barium used

as the dielectric. Internally, these capacitors are not constructed as a coil, so they can

be used in high frequency applications. Ceramic capacitors are normally used for

radio frequency and some audio applications. Ceramic capacitors range in value from

figures as low as a few Pico farads to around 0.1 micro farads.

Fig 2.5 Various Capacitors

Electrolytic Capacitors (Electrochemical type capacitors):

Large values of capacitance can be obtained in comparison with the size of the

capacitor, because the dielectric used is very thin. The most important characteristic

of electrolytic capacitors is that they have polarity. They have a positive and a

negative electrode [Polarized]. This means that it is very important which way round

they are connected. Electrolytic capacitors range in value from about 1µF to

thousands of µF. Mainly, this type of capacitor is used as a ripple filter in a power

supply circuit, or as a filter to bypass low frequency signals, etc.

Fig 2.6 Electrolytic Capacitors

In this project, electrolytic capacitors of the order of F are used like 0.01, 47

and a ceramic capacitor of 0.1µf.

2.3 Transistor

A Transistor is a semiconductor device used to amplify and switch electronic

signals. It is made of a solid piece of semiconductor material, with at least three

terminals for connection to an external circuit. A voltage or current applied to one pair

of the transistor‟s terminals changes the current flowing through another pair of

terminals. Because the controlled (output) power can be much more than the

controlling (input) power, the transistor provides amplification of a signal. The

transistor is the fundamental building block of modern electronic devices. A transistor

can control its output in proportion to the input signal; that is, it can act as an

amplifier. Alternatively, the transistor can be used to turn current on or off in a circuit

as an electrically controlled switch, where the amount of current is determined by

other circuit elements. Modern transistor audio amplifiers of up to a few hundred

watts are common and relatively inexpensive.

In many circuits a resistor is used to convert the changing current to a

changing voltage, so the transistor is being used to amplify voltage. A transistor may

be used as a switch (either fully on with maximum current, or fully off with no

current) and as an amplifier (always partly on). Today, some transistors are packaged

individually, but many more are found embedded in integrated circuits. A simple

transistor is shown in figure 2.7.

Fig 2.7: Transistors

The BJT (Bipolar Junction Transistor) has three terminals, corresponding to

the three layers of semiconductor-an emitter, a base and a collector. It is useful in

amplifiers, oscillators and many applicants because the currents at the emitter and

collector are controlled by relatively small base current. In this circuit the transistors

are used as amplifiers. “An NPN transistor operating in the active region, the emitter-

base junction is forward biased (electrons and holes are formed at the junction), and

electrons are injected into the base region. Because the base is narrow, most of these

electrons will diffuse into reverse-biased (electronics and holes are formed at, and

move away from the junction) base-collector junction and is swept into the collector;

perhaps one hundredth of the electrons will recombine in the base current”.

By controlling the number of electrons that can leave the base, which is the

dominant mechanism in the base current. Collector current is approximately β

(commonly emitter current gain) times the base current. It is typically greater than 100

small-signal transistors but can be smaller in transistors designed for high power

applications. The NPN and PNP transistors are shown in figure 2.8.

(a) (b)

Fig 2.8: BJT symbols (a) PNP transistor (b) NPN transistor

2.3.1 BC 548

BC548 is general purpose silicon, NPN, bipolar junction transistor. BC stands

for base to collector. There are many other devices based on the BC54x family, such

as the surface-mount versions of the BC547, BC548 and BC549.

Fig 2.9 Transistor BC548

The BC548 transistor is a semiconductor that works to switch electronic

signals, and in some cases amplify them. BC548 transistors are mainly used in

Europe. They are fairly common there, used typically in lower power household

electronics such as net book processors and plasma televisions. In the United States

and Canada, a similar transistor is named 2N3904. Japan's near-equivalent is the

2SC1815. The BC548 can be replaced with similar BC transistors without the danger

of burning out or failing. The BC548 transistor is shown in figure 2.9.

The strengths and weaknesses of the BC548 transistor are derived mainly from

its design. A transistor at its most basic consists of a semiconductor material, a

number of terminals referred to as leads, and an overall packaging or enclosure. Like

many similar designs, theBC548 transistor has three leads that connect to the rest of a

circuit. This makes it a bipolar junction transistor;

2.4 Integrated Circuit(IC 555)

In electronics, an Integrated Circuit (also known as IC, chip, or microchip)

is a miniaturized electronic circuit (consisting mainly of semiconductor devices, as

well as passive components) that has been manufactured in the surface of a thin

substrate of semiconductor material. Integrated circuits are used in almost all

electronic equipment in use today and have revolutionized the world of electronics.

Computers, cellular phones, and other digital appliances are now inextricable parts of

the structure of modern societies, made possible by the low cost of production of

integrated circuits.

A hybrid integrated circuit is a miniaturized electronic circuit constructed of

individual semiconductor devices, as well as passive components, bonded to a

substrate or circuit board. A monolithic integrated circuit is made of devices

manufactured by diffusion of trace elements into a single piece of semiconductor

substrate a chip.

Fig 2.10 Integrated Circuits

Integrated circuits were made possible by experimental discoveries which

showed that semiconductor devices could perform the functions of vacuum tubes and

by mid-20th-century technology advancements in semiconductor device fabrication.

The integration of large numbers of tiny transistors into a small chip was an enormous

improvement over the manual assembly of circuits using electronic components. The

integrated circuits mass production capability, reliability, and building-block approach

to circuit design ensured the rapid adoption of standardized ICs in place of designs

using discrete transistors.

There are two main advantages of ICs over discrete circuits: cost and

performance. Cost is low because the chips, with all their components, are printed as a

unit by photolithography and not constructed as one transistor at a time. Furthermore,

much less material is used to construct a circuit as a packaged IC die than as a discrete

circuit. Performance is high since the components switch quickly and consume little

power (compared to their discrete counterparts) because the components are small and

close together. As of 2006, chip areas range from a few square millimetres to around

350 mm2, with up to 1 million transistors per mm2.

2.4.1 NE555 TIMER:

The 8-pin 555 timer must be one of the most useful ICs ever made and it is

used in many projects. With just a few external components it can be used to build

many circuits, not all of them involve timing. A popular version is the NE555 and this

is suitable in most cases where a '555 timer' is specified. The 556 is a dual version of

the 555 housed in a 14-pin package, the two timers (A and B) share the same power

supply pins. The circuit diagrams on this page show a 555, but they could all be

adapted to use one half of a 556.

Low power versions of the 555 are made, such as the ICM7555, but these

should only be used when specified (to increase battery life) because their maximum

output current of about 20mA (with a 9V supply) is too low for many standard 555

circuits. The ICM7555 has the same pin arrangement as a standard 555. The circuit

symbol for a 555 is a box with the pins arranged to suit the circuit diagram: for

example 555 pin 8 at the top for the +Vs supply, 555 pin 3 outputs on the right.

Usually just the pin numbers are used and they are not labelled with their function.

The 555 and 556 can be used with a supply voltage (Vs) in the range 4.5 to 15V (18V

absolute maximum).

Standard 555 IC create a significant 'glitch' on the supply when their output

changes state. This is rarely a problem in simple circuits with no other ICs, but in

more complex circuits a smoothing capacitor (e.g. 100µF) should be connected across

the +Vs and 0V supply near the 555 or 556.

Features

1. High Current Drive Capability (200mA).

2. Adjustable Duty Cycle.

3. Temperature Stability of 0.005%/°C.

4. Timing From μs to Hours.

5. Turn off Time less than 2μSec.

The IC NE 555 timer is shown below:

Fig 2.11 NE 555 timer pin diagram

The connection of the pins is as follows:

Table 2.2: Connection pins of NE555

No. Name Purpose

1 GND Ground, low level (0V).

2 TRIG A short pulse high- to-low on the trigger starts the timer.

3 OUT During a timing interval, the output stays at +Vcc.

4 RESET A timing interval can be interrupted by applying a reset pulse

to low (0V).

5 CTRL Control Voltage allows access to the internal voltage divider

(2/3 Vcc).

6 THR The threshold at which the interval ends (It ends if the

voltage at THR is at least 2/3Vcc).

7 DIS Connected to a capacitor whose discharge time will influence

the timing interval.

8 V+, Vcc The positive supply Voltage which must be between 3 and 15

V.

2.4.2 INTERNAL BLOCK DIAGRAM

Fig 2.12: Internal diagram of NE555

Trigger input discharging of timing capacitor in an astable circuit. It has a

high input impedance > 2M .

THRESHOLD INPUT

When > 2/3 Vs ('active high') this makes the output low (0V). It monitors the

charging of the timing capacitor in astable and monostable circuits. It has a high input

impedance> 10MΩ providing the trigger input is > 1/3 Vs, otherwise the trigger input

will override the threshold input and hold the output high (+Vs).

RESET INPUT

When less than about 0.7V ('active low') this makes the output low (0V),

overriding other inputs. When not required it should be connected to +Vs. It has input

impedance of about 10 .

CONTROL INPUT

This can be used to adjust the threshold voltage which is set internally to be

2/3 Vs. Usually this function is not required and the control input is connected to 0V

with a 0.01µF capacitor to eliminate electrical noise. It can be left unconnected if

noise is not a problem. The discharge pin is not an input, but it is listed here for

convenience. It is connected to 0V when the timer output is low and is used to

discharge the timing capacitor in astable and monostable circuit

2.5 MONOSTABLE OPERATION

Fig 2.13 Monostable Circuit diagram

When the START switch is pressed the OUTPUT wire goes to 9 volts. It stays

at 9 volts for a time interval called T which depends on the values of R and C. To

calculate T = approx R C Secs. Putting a VARIABLE RESISTOR in place of R will

give you a variable time period. The chart below shows the approximate time period

for various resistors and capacitors.

The 555 timer output can either supply(source) up to 200mA to operate small

bulbs or buzzers or it can absorb (sink) up to 200mA.If you want to switch something

that draws more than 200 mA then you can put a RELAY onto the output terminals

(either as a source or a sink ). You can then switch any device; even a 240 volt AC

powered one. You can also use a TRANSISTOR to operate loads up to about 1 amp

(BFY 51/BC639). RESET BUTTON - If you press this button it connects pin 4 to 0

volts. This makes the output return to 0 volts even when the timer is in the middle of

an operation.

Fig 2.14 Wave forms of Monostable Operation

2.6 PCB (Printed Circuit Board)

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

electrically connect electronic components using conductive pathways, tracks, or

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). PCBs are inexpensive, and can be highly

reliable. They require much more layout effort and higher initial cost than either wire-

wrapped or point-to-point constructed circuits, but are much cheaper and faster for

high-volume production. Much of the electronics industry's PCB design, assembly,

and quality control needs are set by standards that are published by the IPC

organization.

Fig 2.15 General Purpose PCB

Conducting layers are typically made of thin copper foil. Insulating layers

dielectric is typically laminated together with epoxy resin prepreg. The board is

typically coated with a solder mask that is green in colour. Other colours that are

normally available are blue and red. There are quite a few different dielectrics that can

be chosen to provide different insulating values depending on the requirements of the

circuit. Some of these dielectrics are poly tetra fluoro ethylene (Teflon).

2.7 Power Supply

The most common form of nine-volt battery is commonly called the transistor

battery, introduced for the early transistor radios. This is a rectangular prism shape

with rounded edges and a polarized snap connector at the top. This type is commonly

used in pocket radios, smoke detectors, carbon monoxide alarms, guitar effect units,

and radio-controlled vehicle controllers. They are also used as backup power to keep

the time in certain electronic clocks. This format is commonly available in primary

carbon-zinc and alkaline chemistry, in primary lithium iron disulfide, and in

rechargeable form in nickel-cadmium, nickel-metal hydride and lithium-ion. Mercury

oxide batteries in this form have not been manufactured in many years due to their

mercury content. When < 1/3 Vs ('active low') this makes the output high (+Vs). Most

nine-volt alkaline batteries are constructed of six individual 1.5V LR61 cells enclosed

in a wrapper. These cells are slightly smaller than LR8D425 AAAA cells and can be

used in their place for some devices, even though they are 3.5 mm shorter. Carbon-

zinc types are made with six flat cells in a stack, enclosed in a moisture-resistant

wrapper to prevent drying.

As of 2007, 9-volt batteries accounted for 4% of alkaline primary battery sales

in the US. In Switzerland as of 2008, 9-volt batteries totaled 2% of primary battery

sales and 2% of secondary battery sales. Other 9-volt batteries of different sizes exist,

such as the British “Ever Ready” PP series and certain lantern batteries.

Fig 2.16: A 9V Battery

2.8 CONNECTORS:

The battery has both terminals in a snap connector on one end. The smaller

circular (male) terminal is positive, and the larger hexagonal or octagonal (female)

terminal is the negative contact. The connectors on the battery are the same as on the

connector itself; the smaller one connects to the larger one and vice versa. The same

snap style connector is used on other battery types in the Power Pack (PP) series.

Battery polarization is normally obvious since mechanical connection is usually only

possible in one configuration. A problem with this style of connector is that it is very

easy to connect two batteries together in a short circuit, which quickly discharges

batteries, generating heat and possibly a fire. The clips on the nine-volt battery can be

used to connect several nine-volt batteries in series to create higher voltage.

2.9 TECHNICAL SPECIFICATIONS:

These batteries are commonly named 9-volt, and also colloquially named PP3,

Radio battery, square (sic) battery, and Japan ”006P”.They all have a rectangular

shape; the dimensions are height 48.5 mm, length 26.5 mm, width 17.5 mm. Both

terminals are at one end and their centres are 12.7 mm apart. Inside an alkaline or

carbon-zinc 9-volt battery there are six cells, either cylindrical or flat type, connected

in series. Some brands use welded tabs internally to attach to the cells, others press

foil strips against the ends of the cells. Formerly, mercury batteries were made in this

size.

They had higher capacity than carbon-zinc types, a nominal voltage of 8.4

volts, and a very stable voltage output. Once used in photographic and measuring

instruments or long- life applications, they are now unavailable due to environmental

restrictions. Devices designed to use "9V" batteries are generally designed to work

properly over the operating voltage range of a "9V" battery, from fully charged

(typically up to 9.6 V) to nearly dead (typically 5.0 V).

2.10 SELF DISCHARGE:

An alkaline battery that is unused or used with extremely low power

consumption devices (transistor leak current, etc.) can be expected to last

approximately for 6 years, essentially the self- life of a new battery.

Table2.3

Type IEC

name

ANSI/NEDA

name

Typical

Capacity(mAh)

Nominal voltage

Primary (disposable)

Alkaline 6LR61 1604A 565

9 Zinc– carbon

6F22 1604D 400

Lithium 1604LC 1200 9.6

Rechargeable

NiCd 6KR61 11604 120 7.2 8.4 (some)

NiMH 6HR61 7.2H5 175-300 7.2 some

8.4 9.6

Lithium-

ion polymer

520 7.3

CHAPTER 3

VOLTAGE REGULATOR

3.1 INTRODUCTION

A regulated power supply is very much essential for several electronic devices

due to the semiconductor material employed in them have a fixed rate of current as

well as voltage. The device may get damaged if there is any deviation from the fixed

rate. The AC power supply gets converted into constant DC by this circuit. By the

help of a voltage regulator DC unregulated output will be fixed to a constant voltage.

The circuit is made up of linear voltage regulator 7805 along with capacitors and

resistors with bridge rectifier made up from diodes. From giving an unchanging

voltage supply to building confident that output reaches uninterrupted to the

appliance, the diodes along with capacitors handle elevated efficient signal conveyed.

Fig: 3.1 Voltage Regulator

A LM7805 Voltage Regulator is a voltage regulator that outputs +5 volts. An

easy way to remember the voltage output by a LM78XX series of voltage regulators is

the last two digits of the number. A LM7805 ends with "05"; thus, it outputs 5 volts.

The "78" part is just the convention that the chip makers use to denote the series of

regulators that output positive voltage. The other series of regulators, the LM79XX, is

the series that outputs negative voltage. So:

LM78XX: Voltage regulators that output positive voltage, "XX"=voltage output.

LM79XX: Voltage regulators that output negative voltage, "XX"=voltage output

3.2 EXPLANATION OF 7805 PINS:

The LM7805, like most other regulators, is a three-pin IC.

Pin 1 (Input Pin): The Input pin is the pin that accepts the incoming DC voltage,

which the voltage regulator will eventually regulate down to 5 volts.

Pin 2 (Ground): Ground pin establishes the ground for the regulator.

Pin 3 (Output Pin): The Output pin is the regulated 5 volts DC.

Fig: 3.2 LM7805Regulator pins

3.3 ADVANTAGES:

78xx series ICs do not require additional component to provide a constant,

regulated source of power, and are really easy to use.

78xx series ICs have built- in protection against a circuit drawing too much

power.

They have protection against overheating and short-circuits.

In some cases, the current- limiting features of the 78xx devices can

provide protection not only for the 78xx itself, but also for other parts

of the circuit.

The best part is they don‟t really cost much..!! They are quiet inexpensive.

3.4 DISADVANTAGES:

The input voltage must be always slightly greater than 5 volts

They are linear regulators input current required is always the same as the

output current

These types of voltage regulator dissipates a lot of heat therefore a heat

sink is suggested in case you are working with higher voltage like 20 volts

or so but even with 12 volts of input they generate decent amount of heat.

3.5 LOUDSPEAKER

A loudspeaker (or loud-speaker or speaker) is an electro acoustic transducer a

device which converts an electrical audio signal into a corresponding sound. The first

crude loudspeakers were invented during the development of telephone systems in the

late 1800s, but electronic amplification by vacuum tube beginning around 1912 made

loudspeakers truly practical. By the 1920s they were used in radios,

phonographs, public address systems and theatre sound systems for talking motion

pictures.

The most widely-used type of speaker today is the dynamic speaker, invented in 1925

by Edward W. Kellogg and Chester W. Rice. The dynamic speaker operates on the

same basic principle as a dynamic microphone, but in reverse, to produce sound from

an electrical signal. When an alternating current electrical audio signal input is

applied through the voice coil, a coil of wire suspended in a circular gap between the

poles of a permanent magnet, the coil is forced to move rapidly back and forth due to

Faraday's law of induction, which causes a diaphragm (usually conically shaped be

used to convert an electrical signal into sound.

Speakers are typically housed in an enclosure which is often a rectangular or square

box made of wood or sometimes plastic. Where high fidelity reproduction of sound is

required, multiple loudspeakers may be mounted in the same enclosure, each

reproducing a part of the audible frequency range. In this case the individual speakers

are referred to as "drivers" and the entire unit is called a loudspeaker. Miniature

loudspeakers are found in devices such as radio and TV receivers, and many forms of

music players. Larger loudspeaker systems are used for music, sound reinforcement in

theatres and concerts, and in public address systems.

3.6 Ideal transformer

Ideal transformer equations

By Faraday's law of induction

. . . (1)

. . . (2)

Combining ratio of (1) & (2)

Turns ratio . . . (3)

Where for step-down transformers, a > 1

for step-up transformers, a < 1

By law of Conservation of Energy, apparent, real and reactive power are each

conserved in the input and output

. . . (4)

Combining (3) & (4) with this endnote yields the ideal transformer identity

. (5)

By Ohm's Law and ideal transformer identity

. . . (6)

Apparent load impedance Z'L (ZL referred to the primary)

. (7)

It is very common, for simplification or approximation purposes, to analyze the

transformer as an ideal transformer model as represented in the two images. An ideal

transformer is a theoretical, linear transformer that is lossless and perfectly coupled;

that is, there are no energy losses and flux is completely confined within the magnetic

core. Perfect coupling implies infinitely high core magnetic permeability and winding

inductances and zero net magneto motive force.

Fig3.3 : Ideal transformer and induction law

Ideal transformer connected with source VP on primary and load impedance

ZL on secondary, where 0 < ZL < ∞. A varying current in the transformer's primary

winding creates a varying magnetic flux in the core and a varying magnetic field

impinging on the secondary winding. This varying magnetic field at the secondary

induces a varying electromotive force (EMF) or voltage in the secondary winding.

The primary and secondary windings are wrapped around a core of infinitely high

magnetic permeability so that all of the magnetic flux passes through both the primary

and secondary windings. With a voltage source connected to the primary winding and

load impedance connected to the secondary winding, the transformer currents flow in

the indicated directions.

According to Faraday's law of induction, since the same magnetic flux passes

through both the primary and secondary windings in an ideal transformer, a voltage is

induced in each winding, according to eq. (1) in the secondary winding case,

according to eq. (2) in the primary winding case. The primary EMF is sometimes

termed counter EMF. This is in accordance with Lenz's law, which states that

induction of EMF always opposes development of any such change in magnetic field.

The transformer winding voltage ratio is thus shown to be directly

proportional to the winding turns ratio according to eq. (3). According to the law

of Conservation of Energy, any load impedance connected to the ideal transformer's

secondary winding results in conservation of apparent, real and reactive power

consistent with eq. (4).

Fig 3.4 Instrument transformer, with polarity dot and X1 marking on LV side

terminal

The ideal transformer identity shown in eq. (5) is a reasonable approximation

for the typical commercial transformer, with voltage ratio and winding turns ratio

both being inversely proportional to the corresponding current ratio. By Ohm's

Law and the ideal transformer identity: The secondary circuit load impedance can be

expressed as eq. (6). The apparent load impedance referred to the primary circuit is

derived in eq. (7) to be equal to the turns ratio squared times the secondary circuit

load impedance.

3.7 POLARITY:

A dot convention is often used in transformer circuit diagrams, nameplates or

terminal markings to define the relative polarity of transformer windings. Positively-

increasing instantaneous current entering the primary winding's dot end induces

positive polarity voltage at the secondary winding's dot end.

The ideal transformer model neglects the following basic linear aspects in real

transformers. Core losses, collectively called magnetizing current losses, consist of

Hysteresis losses due to nonlinear application of the voltage applied in the transformer

core, and Eddy current losses due to joule heating in the core that are proportional to

the square of the transformer's applied voltage. Whereas windings in the ideal model

have no resistances and infinite inductances, the windings in a real transformer have

finite non-zero resistances and inductances associated with Joule losses due to

resistance in the primary and secondary windings Leakage flux that escapes from the

core and passes through one winding only resulting in primary and secondary reactive

impedance.

Fig3.5: leakage flux of a transformer

3.8 LEAKAGE FLUX

The ideal transformer model assumes that all flux generated by the primary

winding links all the turns of every winding, including itself. In practice, some flux

traverses paths that take it outside the windings. Such flux is termed leakage flux, and

results in leakage inductance in series with the mutually coupled transformer

windings. Leakage flux results in energy being alternately stored in and discharged

from the magnetic fields with each cycle of the power supply. It is not directly a

power loss, but results in inferior voltage regulation, causing the secondary voltage

not to be directly proportional to the primary voltage, particularly under heavy load.

Transformers are therefore normally designed to have very low leakage inductance.

In some applications increased leakage is desired, and long magnetic paths, air

gaps, or magnetic bypass shunts may deliberately be introduced in a transformer

design to limit the short-circuit current it will supply. Leaky transformers may be used

to supply loads that exhibit negative resistance, such as electric arcs, mercury vapour

lamps, and neon signs or for safely handling loads that become periodically short-

circuited such as electric arc welders. Air gaps are also used to keep a transformer

from saturating, especially audio-frequency transformers in circuits that have a DC

component flowing in the windings.

Knowledge of leakage inductance is also useful when transformers are

operated in parallel. It can be shown that if the percent impedance and associated

winding leakage reactance-to-resistance (X/R) ratio of two transformers were

hypothetically exactly the same, the transformers would share power in proportion to

their respective volt-ampere ratings (e.g. 500 kVA unit in parallel with 1,000 kVA

unit, the larger unit would carry twice the current).

However, the impedance tolerances of commercial transformers are

significant. Also, the Z impedance and X/R ratio of different capacity transformers

tends to vary, corresponding 1,000 kVA and 500 kVA units' values being, to

illustrate, respectively, Z ≈ 5.75%, X/R ≈ 3.75 and Z ≈ 5%, X/R ≈ 4.75.

DEFINITION OF TRANSFORMER

Electrical power transformer is a static device which transforms electrical

energy from one circuit to another without any direct electrical connection and with

the help of mutual induction between two windings. It transforms power from one

circuit to another without changing its frequency but may be in

different voltage level.

WORKING PRINCIPLE OF TRANSFORMER

The working principle of transformer is very simple. It depends

upon Faraday‟s law of electromagnetic induction. Actually, mutual induction between

two or more winding is responsible for transformation action in an electrical

transformer.

FARADAY’S LAWS OF ELECTROMAGNETIC INDUCTION

According to these Faraday‟s laws, "Rate of change of flux linkage with

respect to time is directly proportional to the induced EMF in a conductor or coil".

Basic Theory of Transformer

Say you have one winding which is supplied by an alternating electrical

source. The alternating current through the winding produces a continually changing

flux or alternating flux that surrounds the winding. If any other winding is brought

nearer to the previous one, obviously some portion of this flux will link with the

second. As this flux is continually changing in its amplitude and direction, there must

be a change in flux linkage in the second winding or coil. According to Faraday‟s law

of electromagnetic induction, there must be an EMF induced in the second. If the

circuit of the later winding is closed, there must be a current flowing through it. This

is the simplest form of electrical power transformer and this is the most basic

of working principle of transformer.

For better understanding, we are trying to repeat the above explanation in a

more brief way here. Whenever we apply alternating current to an electric coil, there

will be an alternating flux surrounding that coil. Now if we bring another coil near the

first one, there will be an alternating flux linkage with that second coil. As the flux is

alternating, there will be obviously a rate of change in flux linkage with respect to

time in the second coil. Naturally EMF will be induced in it as per Faraday‟s law of

electromagnetic induction. This is the most basic concept of the theory of

transformer. The winding which takes electrical power from the source, is generally

known as primary winding of transformer. Here in our above example it is first

winding.

3.9 PIN DIAGRAM:

3.9.1 IC UM66:

The winding which gives the desired output voltage due to mutual induction in

the transformer, is commonly known as secondary winding of transformer. Here in

our example it is second winding.UM66T is a melody integrated circuit. It is designed

for use in bells, telephones, toys etc. It has an inbuilt tone and a beat generator. The

tone generator is a programmed divider which produces certain frequencies. These

frequencies are a factor of the oscillator frequency. The beat generator is also a

programmed divider which contains 15 available beats. Four beats of these can be

selected. There is an inbuilt oscillator circuit that serves as a time base for beat and

tone generator. It has a 62 notes ROM to play music. A set of 4 bits controls the scale

code while 2 bits control the rhythm code. When power is turned on, the melody

generator is reset and melody begins from the first note. The speaker can be driven by

an external NPN transistor connected to the output of UM66. Many versions of

UM66T are available which generate tone of different songs. For example, UM66T01

generates tone for songs „Jingle bells‟, „Santa Claus is coming to town‟ and „We wish

you a merry X mas‟.

FIG 3.6: IC UM66 and IC 7806

The above mentioned form of transformer is theoretically possible but not

practically, because in open air very tiny portion of the flux of the first winding will

link with second; so the current that flows through the closed circuit of later, will be

so small in amount that it will be difficult to measure. The rate of change of flux

linkage depends upon the amount of linked flux with the second winding. So, it is

desired to be linked to almost all flux of primary winding to the secondary winding.

This is effectively and efficiently done by placing one low reluctance path common to

both of the winding. This low reluctance path is core of transformer, through which

maximum number of flux produced by the primary is passed through and linked with

the secondary winding. This is the most basic theory of transformer.

3.9.2 IC7806: 7806 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. 7806 provide +6V regulated power supply

Capacitors of suitable values can be connected at input and output pins depending

upon the respective voltage levels.

3.10 LIGHT-EMITTING DIODE (LED)

Parts of an LED. Although not directly labelled, the flat bottom surfaces of the

anvil and post embedded inside the epoxy act as anchors, to prevent the conductors

from being forcefully pulled out from mechanical strain or vibration. A light-emitting

diode (LED) is a two- lead semiconductor light source. It is a PN-junction diode,

which emits light when activated. When a suitable voltage is applied to the leads, 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 band 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. A bulb-shaped modern

retrofit LED lamp with aluminium heat sink, a light diffusing dome and E27

screw base, using a built- in power supply working on mains voltage

Fig 3.7 Light Emitting Diodes

Appearing as practical electronic components in 1962, the earliest LEDs

emitted low-intensity infrared light. Infrared LEDs are still frequently used as

transmitting elements in remote-control circuits, such as those in remote controls for a

wide variety of consumer electronics. The first visible-light LEDs were also of low

intensity, and limited to red. Modern LEDs are available across the visible, ultraviolet,

and infrared wavelengths, with very high brightness. Early LEDs were often used as

indicator lamps for electronic devices, replacing small incandescent bulbs. They were

soon packaged into numeric readouts in the form of seven-segment displays, and were

commonly seen in digital clocks.

Recent developments in LEDs permit them to be used in environmental and

task lighting. LEDs have many advantages over incandescent light sources including

lower energy consumption, longer lifetime, improved physical robustness, smaller

size, and faster switching. Light-emitting diodes are now used in applications as

diverse as aviation lighting, automotive headlamps, and advertising, lighting, traffic,

and camera flashes. However, LEDs powerful enough for room lighting are still

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

compact fluorescent lamp sources of comparable output. LEDs have allowed new

text, video displays, and sensors to be developed, while their high switching rates are

also useful in advanced communications technology.

SWITCHES

The most familiar form of switch is a manually

operated electromechanical device with one or more sets of electrical contacts, which

are connected to external circuits. Each set of contacts can be in one of two states:

either "closed" meaning the contacts are touching and electricity can flow between

them, or "open", meaning the contacts are separated and the switch is non conducting.

The mechanism actuating the transition between these two states (open or closed) can

be either a "toggle" (flip switch for continuous "on" or "off") or "momentary" (push-

for "on" or push-for "off") type.

A switch may be directly manipulated by a human as a control signal to a

system, such as a computer keyboard button, or to control power flow in a circuit,

such as a light switch. Automatically operated switches can be used to control the

motions of machines, for example, to indicate that a garage door has reached its full

open position or that a machine tool is in a position to accept another work piece.

Switches may be operated by process variables such as pressure, temperature, flow,

current, voltage, and force, acting as sensors in a process and used to automatically

control a system. For example, a thermostat is a temperature-operated switch used to

control a heating process. A switch that is operated by another electrical circuit is

called a relay. Large switches may be remotely operated by a motor drive mechanism.

Some switches are used to isolate electric power from a system, providing a visible

point of isolation that can be padlocked if necessary to prevent accidental operation of

a machine during maintenance, or to prevent electric shock.

An ideal switch would have no voltage drop when closed, and would have no

limits on voltage or current rating. It would have zero rise time and fall time during

state changes, and would change state without "bouncing" between on and off

positions. Practical switches fall short of this ideal; they have resistance, limits on the

current and voltage they can handle, finite switching time, etc. The ideal switch is

often used in circuit analysis as it greatly simplifies the system of equations to be

solved, but this can lead to a less accurate solution. Theoretical treatment of the

effects of non- ideal properties is required in the design of large networks of switches,

as for example used in telephone exchanges.

TOGGLE SWITCH

In the simplest case, a switch has two conductive pieces, often metal,

called contacts, connected to an external circuit, that touch to complete (make) the

circuit, and separate to open (break) the circuit. The contact material is chosen for its

resistance to corrosion, because most metals form insulating oxides that would

prevent the switch from working. Contact materials are also chosen on the basis

of electrical conductivity ,hardness (resistance to abrasive wear), mechanical strength,

low cost and low toxicity.

Fig 3.8: A toggle switch in the "ON" position.

Sometimes the contacts are plated with noble metals. They may to wipe

against each other to clean off any contamination. Non metallic conductors, such as

conductive plastic, are sometimes used. To prevent the formation of insulating oxides,

a minimum wetting current may be specified for a given switch design.

CHAPTER 4

CIRCIUT DIAGRAM

4.1 CIRCUIT DIAGRAM AND OPERATION:

Fig 4.1: Automatic Night Lamp with Morning Alarm

This circuit automatically turns on a night lamp when bedroom light is

switched off. The lamp remains on ‟until the light sensor senses daylight in the

morning. A super bright white LED is used as the night lamp. It gives bright and cool

light in the room. When the sensor detects the daylight in the morning, a melodious

morning alarm sounds. The circuit is powered from a standard 0-9V transformer.

Diodes D1 through D4 rectify the AC voltage and the resulting DC voltage is

smoothed by C1. Regulator IC 7806gives regulated 6V DC to the circuit. A battery

backup is provided to power the circuit when mains fail. When mains supply is

available, the 9V rechargeable battery charges via diode D5 and resistor R1 with a

reasonably constant current. In the event of mains failure, the battery automatically

takes up the load without any delay.

Diode D5 prevents the battery from discharging backwards following the mains

failure and diode D6 provides current path from the battery. The circuit utilizes light-

dependant. Resistors (LDRs) for sensing darkness and light in therm. The resistance

of LDR is very high in darkness, which reduces to minimum when LDR is fully

illuminated. LDR1detects darkness, while LDR2 detects light in the morning. The

circuit is designed around the popular timer IC NE555 (IC2), which is configured as a

monostable. IC2 is activated by a low pulse applied to its trigger pin 2. Once

triggered, output pin 3 of IC2 goes high and remains in that position until IC2 is

triggered again at its pin 2. When LDR1 illuminated with ambient light in the room,

its resistance remains low, this keeps trigger pin 2 of IC2 at a positive potential.

As a result, output pin 3 of IC2 goes low and the white LED remains off. As

the illumination of LDR1‟s sensitive window reduces, the resistance of the device

increases. In total darkness, the specified LDR has a resistance in excess of 280 kilo

ohms. When the resistance of LDR1 increases, a short pulse is applied to trigger pin 2

of IC2 via resistor R2 (150 kilo ohms).

This activates the monostable and its output goes high, causing the white LED to

glow. Low-value capacitor C2 maintains the monostable for continuous operation,

eliminating the timer effect. By increasing the value of C2, the „on‟ time of the white

LED can be adjusted to a predetermined time. LDR2 and associated components

generate the morning alarm at dawn.

LDR2 detects the ambient light in the room at sunrise and its resistance

gradually falls and transistor T1 starts conducting. When T1 conducts, melody-

generator IC UM66 (IC3) gets supply voltage from the emitter of T1 and it starts

producing the melody. The musical tone generated by IC3 is amplified by single-

transistor amplifier T2. Resistor R7 limits the current to IC3 and zener diode ZD

limits the voltage to a safer level of 3.3 volts.

The circuit can be easily assembled on a general-purpose PCB. Enclose it in a

good-quality plastic case with provisions for LDR and LED. Use a reflective holder

for white LED to get a spotlight effect for reading. Place LDRs away from the white

LED, preferably on the backside of the case, to avoid unnecessary illumination. The

speaker should be small so as to make the gadget compact.

This circuit automatically turns on a night lamp when bedroom light is

switched off. The lamp remains „on‟ until the light sensor senses daylight in the

morning. A super- bright white LED is used as the night lamp. It gives bright and cool

light in the room. When the sensor detects the daylight in the morning, a melodious

morning alarm sounds. The circuit is powered from a standard 0-9V transformer.

Diodes D1 through D4 rectify the AC voltage and the resulting DC voltage is

smoothed by C1. Regulator IC 7806 gives regulated 6V DC to the circuit. A battery

backup is provided to power the circuit when mains fail. When mains supply is

available, the 9V rechargeable battery charges via diode D5 and resistor R1 with a

reasonably constant current. In the event of mains failure, the battery automatically

takes up the load without any delay. Diode D5 prevents the battery from discharging

backwards following the mains failure and diode D6 provides current path from the

battery

The circuit utilizes light-dependant resistors (LDRs) for sensing darkness and

light in the room. The resistance of LDR is very high in darkness, which reduces to

minimum when LDR is fully illuminated. LDR1 detects darkness, while LDR2

detects light in the morning. The circuit is designed around the popular timer IC

NE555 (IC2), which is configured as a monostable. IC2 is activated by a low pulse

applied to its trigger pin 2. Once triggered, output pin 3 of IC2 goes high and remains

in that position until IC2 is triggered again at its pin 2. When LDR1 is illuminated

with ambient light in the room, its resistance remains low, which keeps trigger pin 2

of IC2 at a positive potential. As a result, output pin 3 of IC2 goes low and the white

LED remains off. As the illumination of LDR1‟s sensitive window reduces, the

resistance of the device increases.

In total darkness, the specified LDR has a resistance in excess of 280 kilo ohms.

When the resistance of LDR1 increases, a short pulse is applied to trigger pin 2 of IC2

via resistor R2 (150 kilo ohms). This activates the monostable and its output goes

high, causing the white LED to glow. Low-value capacitor C2 maintains the

monostable for continuous operation, eliminating the timer effect. By increasing the

value of C2, the „on‟ time of the white LED can be adjusted to a predetermined time.

LDR2 and associated components generate the morning alarm at dawn. LDR2

detects the ambient light in the room at sunrise and its resistance gradually falls and

transistor T1 starts conducting. When T1 conducts, melody-generator IC UM66 (IC3)

gets supply voltage from the emitter of T1 and it starts producing the melody. The

musical tone generated. By IC3 is amplified by single-transistor amplifier T2.

Resistor R7 limits the current to IC3 and zener diode ZD limits the voltage to a safer

level of 3.3 volts. The circuit can be easily assembled on a general-purpose PCB.

Enclose it in a good-quality plastic case with provisions for LDR and LED. Use a

reflective holder for white LED to get a spotlight effect for reading. Place LDRs away

from the white LED, preferably on the backside of the case, to avoid unnecessary

illumination. The speaker should be small so as to make the gadget compact.

4.2 ADVANTAGES:

Highly sensitive

Works according to the light intensity

Fit and Forget system Low cost and reliable.

Complete elimination of man power.

Can handle heavy loads up to 7A

System can be switched into manual mode whenever required.

4.3APPLICATIONS:

Bed Rooms

Hostels and Hotels

Balcony / stair case / parking Lightings

Street lights Garden Light

CHAPTER-4

OUTPUT OF THE CIRCUIT

CHAPTER -5

CONCLUSION AND FUTURESCOPE

The project AUTOMATIC LED NIGHT LAMP makes use of a super bright

LED as the night lamp. It is powered by a 0 -9v transformer. In case of power failure,

battery backup is also provided which keeps the circuit in active mode. Light

dependent resisters or LDR‟S are used for sensing the darkness in the room.

Once the bed room light is switched off the LDR resistance becomes

minimum and LED glows. The LED provides a bright at cool night. In the morning,

the sensor detects the sunlight and switches off along with an alarm that goes ON. The

circuit in the project can be easily assembly on a PCB. Also the speaker should be a

small one to make the circuit compact.

The project described hear has got high sensitivity and depend on light intensity

for it‟s working. It other advantages are its low cost and reliability no manual

operation is required and loads up to 7A can be handled. However it‟s also has

manual mode of operation too. This project can be applied a variety of places like

bedrooms hostels, hotels. Also to save electricity it can be applied to street lamps and

gardens. Thus the working of the automatic night lamp with morning alarm was

explained in detail. In this project, no need of manual operation like ON time and

OFF time setting so we reduce manual works by 100%. By using this system energy

consumption is also reduced

REFERENCES

1) http://ece-eee.mini-projects.in

2) http://seminarprojects.com

3) http://www.allprojectreports.com

4) S. Reegan & Elan Johnson “Automatic Night Lamp with Morning Alarm”, Dept.

of E.C.E., S.V.P.C.E.T., Puttur, published in http://www.scribd.com

5) http://www.eeweb.com

6) http://www.princeton.edu

7) D. Mohan Kumar “Automatic Night Lamp with Morning Alarm” published in

Circuit Ideas, Electronics for you, December 2003