OVER VOLTAGE UNDER VOLTAGE TRIPPING MECHANISM

OVER VOLTAGE OR UNDER VOLTAGE
TRIPPING MECHANISM
Mini Project report submitted in partial fulfillment of the requirement
for the award of the Degree of
BACHELOR OF TECHNOLOGY
By
I.N.M.SANTHOSH :12006029
S.VISHNU MADHURI :12006041
M.SAI KUMAR :12006110
SYED NAZIA NOOR :12006280
K.MAHESHWARA REDDY :12006310
Under the esteemed guidance of
B.JYOTHI
K L UNIVERSITY, GREEN FIELDS
VADDESWARAM, GUNTUR DISTRICT
2013-2014
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ACKNOWLEDGEMENT
We take this opportunity to express our profound gratitude and deep regards to our
guide B.JYOTHIfor her exemplary guidance, monitoring and constant encouragement
throughout the course of this thesis. The blessing, help and guidance given by her time to
time shall carry us a long way in the journey of life on which we are about to embark.
We also take this opportunity to express a deep sense of gratitude to in-charge
B.JYOTHIfor his cordial support, valuable information and guidance, which helped us in
completing this task through various stages.
We are obliged to our Head of the department Dr.M.UMAVANIfor giving this great
opportunity. We are grateful for their cooperation during the period of our assignment.
Lastly, we thank every one of our batch for their cooperation, support and for their constant
encouragement without which this assignment would not be possible
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DECLARATION
We declare the project work “Over voltage and under voltage tripping mechanism”
was carried-out by us during 1nd semester (A.Y 2013-14) and this work is not the same as that
of any other and has not been submitted for awards of any other degree/diploma
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Place:KoneruLakshmaiah University
Date: 1st November
S. VISHNU MADHURI :12006041

KLUNIVERSITY, GREENFIELDS
VADDESWARAM, GUNTUR DISTRICT
DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING
CERTIFICATE
This is to certify that the project report entitled “Over voltage and under voltage
tripping mechanism” being submitted by the following students
S. VISHNU MADHURI :12006041
In partial fulfillment for the award of the Degree of Bachelor of Technology in EEE
to the KL University is a record of benefited work carried out by him under my guidance and
supervision.
GUIDE HEAD OF THE DEPARTMENT
(B.JYOTHI) ( Dr.UMA VANI)
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CONTENTS
ABSTRACT -6
INTRODUCTION -7
COMPONENTS - 8
CIRCUIT - 9
DESCRIPTION -10
WORKING -32
SUMMARY -33
CONCLUSION -34
OUTPUT -35
BIBLOGRAPHY -38

ABSTRACT
The aim of this project is to develop a low voltage and high voltage tripping
mechanism to protect the load from damage. The fluctuation in AC mains supply is frequent
in homes and industries. The sensitive electronic devices in these conditions can get easily
damaged. It is preferable to have a tripping mechanism to protect the load. This proposed
system will trip the load in the event of the input voltage falling below/above a set value.
Two 555 timers are used as window comparator. This delivers an error output if the input
voltage to them crosses the range beyond the voltage window. A relay is then operated to cut-off
the load for safety reasons. A lamp is used as load in this project. The concept in future
can be extended by integrating an alarm, which sounds when voltage fluctuations occur. It
can also be interfaced with a GSM modem to convey alert message to the user via SMS to
take appropriate action.
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INTRODUCTION
Voltage, electrical potential difference, electric tension or electric pressure (denoted
ΔV and measured in units of electric potential: volts, or joules per coulomb) is the electric
potential difference between two points, or the difference in electric potential energy of a unit
charge transported between two points. Voltage is equal to the work done per unit charge
against a static electric field to move the charge between two points. A voltage may represent
either a source of energy (electromotive force), or lost, used, or stored energy (potential
drop).
A voltmeter can be used to measure the voltage (or potential difference) between two points
in a system; usually a common reference potential such as the ground of the system is used as
one of the points. Voltage can be caused by static electric fields, by electric current through a
magnetic field, by time-varying magnetic fields, or some combination of these three.
OVER VOLTAGE:
When the voltage in a circuit or part of it is raised above its upper design limit, this is known
as overvoltage. The conditions may be hazardous. Depending on its duration, the overvoltage
event can be transient—a voltage spike—or permanent, leading to a power surge
LOW VOLTAGE:
Under Voltage condition occurs when a load is suddenly connected to a power supply.The
load will start to draw current, this causes the voltage to temporarily drop.
Measuring instruments
Multimeter set to measure voltage
Instruments for measuring voltages include the voltmeter, the potentiometer, and
the oscilloscope. The voltmeter works by measuring the current through a fixed resistor,
which, according to Ohm's Law, is proportional to the voltage across the resistor. The

potentiometer works by balancing the unknown voltage against a known voltage in a bridge
circuit. The cathode-ray oscilloscope works by amplifying the voltage and using it to deflect
an electron beam from a straight path, so that the deflection of the beam is proportional to the
voltage.
Components:
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• Transformer 12v
• Bridge wave rectifier
• Capacitors-480,0.1micro farads
• Regulator 7812
• Potentiometer-50k
• Zener diode-6.8v,6.0v
• Resistances -10k,5k,1k
• IC LM324
• Led
• Diode of IN4007
• Relay
• Load

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DESCRIPTION:
TRANSFORMER:
A transformer is a static electrical device that transfers energy by inductive coupling
between its winding circuits. A varying current in the primary winding creates a varying
magnetic flux in the transformer's core and thus a varying magnetic flux through the
secondary winding. This varying magnetic flux induces a varying electromotive force (emf)
or voltage in the secondary winding. Transformers can be used to vary the relative voltage of
circuits or isolate them, or both.
Transformers range in size from thumbnail-sized used in microphones to units
weighing hundreds of tons interconnecting the power grid. A wide range of transformer
designs are used in electronic and electric power applications. Transformers are essential for
the transmission, distribution, and utilization of electrical energy.
APPLICATIONS:
Transformers are used to increase voltage before transmitting electrical energy over
long distances through wires. Wires have resistance which loses energy through joule heating
at a rate corresponding to square of the current. By transforming power to a higher voltage
transformers enable economical transmission of power and distribution. Consequently,
transformers have shaped the electricity supply industry, permitting generation to be located
remotely from points of demand. All but a tiny fraction of the world's electrical power has
passed through a series of transformers by the time it reaches the consumer.
Transformers are also used extensively in electronic products to step-down the supply
voltage to a level suitable for the low voltage circuits they contain. The transformer also
electrically isolates the end user from contact with the supply voltage.
Signal and audio transformers are used to couple stages of amplifiers and to match
devices such as microphones and record players to the input of amplifiers. Audio
transformers allowed telephone circuits to carry on a two-way conversation over a single pair
of wires.

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BRIDGE RECTIFIER:
We us this rectifier as the supply is of ac so we need to convert the ac to dc so the
bridge rectifier is used instead of this we can use full wave also but it is has more losses than
this rectifier as we don’t use center tap in this rectifier as it forms continuous flow of direct
current. We will use four diodes in this rectifier and one capacitor parallel to this acts as
filtering of the ac currents from dc currents.
It requires four diodes instead of two, but avoids the need for a center tapped
transformer.
During the positive half cycle of the secondary voltage, diodes D1 and D3 are
conducting and D2 and D4 are no conducting. Therefore, current flows through the secondary
winding, diode D1 and D3, resistor RL.
During the negative half cycle of the secondary voltage, the diodes D2 &D4 conduct
and diodes D1 and D3 do not conduct. Then current flows through the secondary winding,
diode D2 D4 and Resistor RL. In both cases current passes through the load resistor in the
same direction

A bridge rectifier, is a group of rectifiers (4 in a single phase) wired so that each half
of an AC current is passed to respective positive and negative lines of a DC output.
It provides full wave rectification of AC into DC.
ADVANTAGES:
 With the availabilities of low-cost, highly reliable and small-sized silicon
diodes bridge rectifier is becoming more and more popular in comparison to
center-tap and half-wave rectifier. It has many advantages over a center-tap
and half-wave rectifier, as given below.
 The rectification efficiency of full-wave rectifier is double of that of a half-wave
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rectifier.
 The ripple voltage is low and of higher frequency in case of full-wave rectifier
so simple filtering circuit is required.
 Higher output voltage, higher output power and higher Transformer
Utilization Factor (TUF) in case of a full-wave rectifier.
 In a full-wave rectifier, there is no problem due to dc saturation of the core
because the dc current in the two halves of the two halves of the transformer
secondary flow in opposite directions.
No centre tap is required in the transformer secondary so in case of a bridge rectifier
the transformer required is simpler. If stepping up or stepping down of voltage is not
required, transformer can be eliminated even.
The PIV is one half that of centre-tap rectifier. Hence bridge rectifier is highly suited
for high voltage applications.
Transformer utilization factor, in case of a bridge rectifier, is higher than that of a
centre-tap rectifier.
For a given power output, power transformer of smaller size can be used in case of the
bridge rectifier because current in both (primary and secondary) windings of the supply
transformer flow for the entire ac cycle.

IC 7812:
This is the voltage regulator IC which gives you +12 volts. after the capacitor it is being used
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in power supply.In 7812 , the 78 denotes (+ve)
This is a 9V power supply which will work even on power failure. It uses a rechargeable
battery and regulators. A transformer with 15-0-15 AC volts output is required. In the first
regulator U1 the output is lifted up by 1.4V and in the second regulator U2 by a resistor
divider. In the second regulator the voltage across resistor R3 is 5V, so the current is 5V / 1K
= 5mA this adds to the quiescent current of 5mA from the regulators ground terminal and
flows into the resistors R1 and R2 in parallel which form 404 ohms, 10mA thru 404 ohms is
4V. So the output will be 5 + 4 = 9V. Note that the charge and discharge paths of the battery
are separated with diodes.

In this regulator we will use two capacitors of 1micro farads of either side of the
regulator as it will supply the power even there is no power and also it will reduce the
fluctuations in the voltage.This capacitor is there to filter out any noise coming from the voltage
source (the battery). The voltage regulator works best and will be most efficient when a clean DC
signal is fed into it. We don't want any ac noise (ripple) imposed on the DC line voltage. The
second capacitor, the 0.1uF ceramic capacitor, is hooked up after the voltage regulator. This
capacitor is there again to filter out any noise or high-frequency (ac) signals that may be on the
DC voltage line.
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ADVANTAGES:
- Internal thermal overload protection
- No external components required
- Output transistor safe area protection
- Internal short circuit current limit

CAPACITORS:
Capacitors store and release electrical charge. They are used for filtering power supply lines,
tuning resonant circuits, and for blocking DC voltages while passing AC signals, among numerous
other uses.
470micro farads:
15
0.1 micro capacitor

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LM324:
It is a 14pin IC consisting of four independent operational amplifiers (op-amps)
compensated in a single package. Op-amps are high gain electronic voltage amplifier with
differential input and, usually, a single-ended output. The output voltage is many times higher
than the voltage difference between input terminals of an op-amp.
These op-amps are operated by a single power supply LM324 and need for a dual supply is
eliminated. They can be used as amplifiers, comparators, oscillators, rectifiers etc. The
conventional op-amp applications can be more easily implemented with LM324.
Pin Diagram:

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Pin Description:
Pin
No
Function Name
1 Output of 1st comparator Output 1
2 Inverting input of 1st comparator Input 1-
3 Non-inverting input of 1st comparator Input 1+
4 Supply voltage; 5V (up to 32V) Vcc
5 Non-inverting input of 2nd comparator Input 2+
6 Inverting input of 2nd comparator Input 2-
7 Output of 2nd comparator Output 2
8 Output of 3rd comparator Output 3
9 Inverting input of 3rd comparator Input 3-
10 Non-inverting input of 3rd comparator Input 3+
11 Ground (0V) Ground
12 Non-inverting input of 4th comparator Input 4+
13 Inverting input of 4th comparator Input 4-
14 Output of 4th comparator Output 4
Integrated circuits (ICs) are very important components found in many circuits. They
are also called silicon chips or microchips. Basic 555 timer circuits ranging to complex PIC
Microcontroller circuits and computer processors (CPUs) are based on the use of integrated
circuits.
People often get confused with the term integrated circuit. The diagrams below
clearly show the integrated circuit package with its 8 pins. However, the integrated circuit is
found inside the package. The package is the outer casing, usually made from non-conducting
ceramic material. The IC is connected to the pins by fine wires. Diagram ‘A’ shows part of
the package cut away revealing the IC inside. Diagram ‘B’ shows the package as transparent.
This means that the connecting wires from the IC to the pins can be seen

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DIAGRAM A
DIAGRAM B
Integrated circuits are composed hundreds, thousands and even hundreds of thousands
of electronic components. These are formed on interlocking layers / wafers of silicon making
it possible to create small individual electronic components. An example of the an integrated
circuit with its many layers can be seen opposite. If an area of an integrated circuit is
magnified thousands of times its various layers can be seen. The drawing opposite shows
three layers, each layer is shown as a specific colour. Although transistors and resistors donot
look like typically sized components, the interlocking layers form miniature versions and
they work in the same way.

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Zener diode:
We use two diodes in this project near the low voltage and high voltage near low
voltage we use 6.0v and near high voltage 6.8v diode. As this diodes are used as break down
voltage
Constructions:
The zener diode's operation depends on the heavy doping of its p-n junction. The
depletion region formed in the diode is very thin (<1 μm) and the electric field is
consequently very high (about 500 kV/m) even for a small reverse bias voltage of about 5 V,
allowing electrons to tunnel from the valence band of the p-type material to the conduction
band of the n-type material.
In the atomic scale, this tunneling corresponds to the transport of valence band
electrons into the empty conduction band states; as a result of the reduced barrier between
these bands and high electric fields that are induced due to the relatively high levels of
dopings on both sides.[2] The breakdown voltage can be controlled quite accurately in the
doping process. While tolerances within 0.05% are available, the most widely used tolerances
are 5% and 10%. Breakdown voltage for commonly available zener diodes can vary widely
from 1.2 volts to 200 volts.

This diode has only a unidirectional flow of current that also allow current to flow in the
opposite direction, but only when exposed to enough voltage. And while that sounds a bit
esoteric, they’re actually among the handiest components ever to cross an engineer’s bench,
providing great solutions to a number of common needs in circuit design.
A Zener diode is a diode which allows current to flow in the forward direction in the same
manner as an ideal diode, but will also permit it to flow in the reverse direction when the
voltage is above a certain value known as the breakdown voltage, "Zener knee voltage" or
"zener voltage" or "Avalanche point".
Zener Diode as Voltage Regulators.The function of a regulator is to provide a constant output
voltage to a load connected in parallel with it in spite of the ripples in the supply voltage or
the variation in the load current and the zener diode will continue to regulate the voltage until
the diodes current falls below the minimum IZ(min) value in the reverse breakdown region. It
permits current to flow in the forward direction as normal, but will also allow it to flow in the
reverse direction when the voltage is above a certain value - the breakdown voltage known as
the Zener voltage. The Zener diode specially made to have a reverse voltage breakdown at a
specific voltage. Its characteristics are otherwise very similar to common diodes. In
breakdown the voltage across the Zener diode is close to constant over a wide range of
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currents thus making it useful as a shunt voltage regulator. The purpose of a voltage regulator
is to maintain a constant voltage across a load regardless of variations in the applied input
voltage and variations in the load current. A typical Zener diode shunt regulator is shown in
Figure 3. The resistor is selected so that when the input voltage is at VIN(min) and the load
current is at IL(max) that thecurrent through the Zener diode is at least Iz(min). Then for all
other combinations of input voltage and load current the Zener diode conducts the excess
current thus maintaining a constant voltage across the load. The Zener conducts the least
current when the load current is the highest and it conducts the most current when the load
current is the lowest.
Resistors:
We use somany resistances to reduce the current flow and to safe the circuit without
damaging due to high current. We use 10k(4),5k(2),1k(2).
1st. Two Digits- Multiplier- Tolerance- Temp. Co-eff.
Black 0 Black 1 Not Used Not Used
Brown 1 Brown 10 Brown 1% Brown 100
Red 2 Red 100 Red +2% Red 50
Orange 3 Orange 1K Not Used Orange 15
Yellow 4 Yellow 10K Not Used Yellow 25
Green 5 Green 100K Not Used Green 0.5
Blue 6 Blue 1M Not Used Blue 0.25
Violet 7 Violet 10M Not Used Violet 0.1
Grey 8 Not Used Not Used Not Used
White 9 Not Used Not Used Not Used
- Silver 0.01 Silver+10% Not Used
- Gold 0.1 Gold +5% Not Used
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There are various devices whose resistance changes with various quantities. The
resistance of NTC exhibit a strong negative temperature coefficient, making them useful for
measuring temperatures. Since their resistance can be large until they are allowed to heat up
due to the passageof current, they are also commonly used to prevent
excessive currentsurges when equipment is powered on. Similarly, the resistance of
a humistor varies with humidity. Metal oxide visitor’s drop to a very low resistance when a
high voltage is applied, making them useful for protecting electronic equipment by absorbing
dangerous voltage surges. The third band of a four-banded resistor represents multiplier and
the fourth band as tolerance. Whereas, the five and six colour-banded resistors, the third band
rather represents as third digit but the fourth and fifth bands represent as multiplier and
tolerance respectively.
10ohms resistance
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1k ohms resistor:
5k resistance

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Variable resistance:
We use two variable resistances of 50kohm these resistances are mainly used near the
low voltageand high voltage ic2 circuit the main uses of using there is to various themout
come resistanceA common element in electronic devices is a three-terminal resistor with a
continuously adjustable tapping point controlled by rotation of a shaft or knob. These variable
resistors are known aspotentiometers when all three terminals are present, since they act as a
continuously adjustable voltage divider. A common example is a volume control for a radio
receiver.
Accurate, high-resolution panel-mounted potentiometers (or "pots") have resistance
elements typically wirewound on a helical mandrel, although some include a conductive-plastic
resistance coating over the wire to improve resolution. These typically offer ten turns
of their shafts to cover their full range. They are usually set with dials that include a simple
turns counter and a graduated dial. Electronic analog computers used them in quantity for
setting coefficients, and delayed-sweep oscilloscopes of recent decades included one on their
panels.
Potentiometer (Pot) is another class of variable resistors and is used as an adjustable
voltage divider. It consists of a fixed resistance track having connections at both ends and a
sliding contact, called wiper, which moves along this track by turning the spindle. If only one
of the connections and wiper are used, it behaves as a variable resistor or rheostat. In case
wiper is not used, it will offer fixed resistance across the two connections. They are specified
by their fixed value resistance. Learn about internal structure and working of potentiometer.
Potentiometer also known as pot is generally used in circuits to provide variable resistance or

variable voltage. The heart of the potentiometer is a resistive strip inside it through which one
can adjust the amount of resistance/voltage to pass in a circuit through it. Potentiometers are
commonly used in circuits for various purposes like to control volume in audio circuits, to
regulate the speed of the motor in a fan, as light dimmer, etc.
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SPECIFICATIONS:
Various parameters like size, type of track and also resistance is used to define a
variable resistance. Usually the spindle diameter of a variable resistor is 6mm.
If the variable resistor has a straight track it is defined in the component by the short form
LIN representing a linear track. If it is a rotary track it is represented in short as LOG, as for a
logarithmic track.
A common representation is given below.
5K6 LIN – 5.6 kilo ohm with a linear track.
2M LOG – 2 Mega ohm with a logarithmic track.
LED (LIGHT EMITTING DIODES):
LEDs lights produce light from a solid matter known as semi conductor. It produces
the light through the movement of electrons through that solid matter. The semi conductor
consists of the positive and negative layers which helps for the movement of electrons. When
the power hits the semiconductor, the electrons in negative layer gets charged and moves
through the positive layer. This helps to produce light in a LED light. LED is an abbreviation
for light-emitting diode. An LED consists of a chip of semiconducting material doped with
impurities to create a p-n junction. As in other diodes, current flows easily from the p-side, or
anode, to the n-side, or cathode, but not in the reverse direction. Charge-carriers - electrons

and holes - flow into the junction from electrodes with different voltages. When an electron
meets a hole, it falls into a lower energy level, and releases energy in the form of a photon
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ADVANTAGES:
LED bulbs emit considerably less heat than ordinary bulbs. Many LED bulbs are
actually cool to the touch when in use. This makes them safer for use in a variety of areas
throughout the home and office, especially in areas like nurseries or family rooms where
children are present.
EFFICIENCY:
LED bulbs are energy savers. At 80% efficiency, LED bulbs convert 80% of the electricity
they use into light energy. The remaining 20% is converted to heat.

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DIODE:
In this project we use two specific diodes of IN4007 diodes .this diode are of p-n-p are
n-p-n transistor When an ‘inductor’ device such as a relay is turned off a high voltage can be
generated for a short time (Dia1). This voltage ‘spike’ can damage the relay and other
components. However, the diode does not allow current to pass through it in the wrong
direction and short circuits this spike.The diode can also be used to protect a ‘meter’ from a
reverse current
Diodes are frequently used to conduct damaging high voltages away from sensitive
electronic devices. They are usually reverse-biased (non-conducting) under normal
circumstances. When the voltage rises above the normal range, the diodes become forward-biased
(conducting)

A diode can be used as a temperature measuring device, since the forward voltage
drop across the diode depends on temperature, as in a silicon bandgap temperature sensor.
From the Shockley ideal diode equation given above, it might appear that the voltage has
a positive temperature coefficient (at a constant current), but usually the variation of
the reverse saturation current term is more significances than the variation in the thermal
voltage term
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Applications:
 A diode offers a very low resistance in one direction and a very high resistance
in other direction, thus permitting an easy current flow in only one direction.
 Application in wave-shaping circuits(ideal diodes)
Features
 PeakRepeat Reverse Voltage (Vrms): 1000V
 Max. RMS Reverse Voltage (Vr): 700V
 Average Rectified Current (Io): 1.0A
 Max. Reverse Current (Ir): 0.01mA
 Max. Forward Voltage Drop (Vf): 1.1V

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RELAYS:
A relay is an electrically operated switch. Many relays use an electromagnet to
operate a switching mechanism mechanically, but other operating principles are also used.
Relays are used where it is necessary to control a circuit by a low-power signal (with
complete electrical isolation between control and controlled circuits), or where several
circuits must be controlled by one signal. The first relays were used in long distance telegraph
circuits, repeating the signal coming in from one circuit and re-transmitting it to another.
Relays were used extensively in telephone exchanges and early computers to perform logical
operations.
A type of relay that can handle the high power required to directly control an electric
motor or other loads is called a contactor. Solid-state relays control power circuits with no
moving parts, instead using a semiconductor device to perform switching. Relays with
calibrated operating characteristics and sometimes multiple operating coils are used to protect
electrical circuits from overload or faults; in modern electric power systems these functions
are performed by digital instruments still called "protective relays".
Operation:
When an electric current is passed through the coil it generates a magnetic field that
activates the, and the armature consequent movement of the movable contact(s) either makes
or breaks (depending upon construction) a connection with a fixed contact. If the set of
contacts was closed when the relay was de-energized, then the movement opens the contacts
and breaks the connection, and vice versa if the contacts were open. When the current to the

coil is switched off, the armature is returned by a force, approximately half as strong as the
magnetic force, to its relaxed position. Usually this force is provided by a spring, but gravity
is also used commonly in industrial motor starters. Most relays are manufactured to operate
quickly. In a low-voltage application this reduces noise; in a high voltage or current
application it reduces arcing.
When the coil is energized with direct current, a diode is often placed across the coil
to dissipate the energy from the collapsing magnetic field at deactivation, which would
otherwise generate a voltage spike dangerous to semiconductor circuit components. Some
automotive relays include a diode inside the relay case. Alternatively, a contact protection
network consisting of a capacitor and resistor in series (snubber circuit) may absorb the
surge. If the coil is designed to be energized with alternating current (AC), a small copper
"shading ring" can be crimped to the end of the solenoid, creating a small out-of-phase
current which increases the minimum pull on the armature during the AC cycle.
A solid-state relay uses a thyristor or other solid-state switching device, activated by
the control signal, to switch the controlled load, instead of a solenoid. An optocoupler (a
light-emitting diode (LED) coupled with a photo transistor) can be used to isolate control and
controlled circuits.
Applications:
Relays are used for:
 Amplifying a digital signal, switching a large amount of power with a small operating
29
power. Some special cases are:
 A telegraph relay, repeating a weak signal received at the end of a long
wireControlling a high-voltage circuit with a low-voltage signal, as in some types of
modems or audio amplifiers,
 Controlling a high-current circuit with a low-current signal, as in the starter solenoid
of an automobile,
 Detecting and isolating faults on transmission and distribution lines by opening and
closing circuit breakers (protection relays).

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TRANSISTOR:
A transistor is a semiconductor device used to amplify and switch electronic signals
and electrical power. It is composed 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 through another pair of terminals. Because the
controlled (output) power can be higher than the controlling (input) power, a transistor can
amplify a signal. Today, some transistors are packaged individually, but many more are
found embedded in integrated circuits.
Importance:
A Darlington transistor opened up so the actual transistor chip (the small square) can
be seen inside. A Darlington transistor is effectively two transistors on the same chip. One
transistor is much larger than the other, but both are large in comparison to transistors in
large-scale integration because this particular example is intended for power applications.
The transistor is the key active component in practically all modern electronics. Many
consider it to be one of the greatest inventions of the 20th century. Its importance in today's
society rests on its ability to be mass-produced using a highly automated process
(semiconductor device fabrication) that achieves astonishingly low per-transistor costs. The
invention of the first transistor at Bell Labs was named an IEEE Milestone in 2009.
The transistor's low cost, flexibility, and reliability have made it a ubiquitous device.

Transistorized mechatronic circuits have replaced electromechanical devices in controlling
appliances and machinery. It is often easier and cheaper to use a standard microcontroller.
Advantages:
• The key advantages that have allowed transistors to replace their vacuum tube
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predecessors in most applications are
• No power consumption by a cathode heater.
• Small size and minimal weight, allowing the development of miniaturized electronic
devices.
• Low operating voltages compatible with batteries of only a few cells.
• No warm-up period for cathode heaters required after power application.
• Lower power dissipation and generally greater energy efficiency.
• Higher reliability and greater physical ruggedness.
• Extremely long life. Some transistorized devices have been in service for more than
50 years.
• Complementary devices available, facilitating the design of complementary-symmetry
circuits, something not possible with vacuum tubes.
• Insensitivity to mechanical shock and vibration, thus avoiding the problem of
microphones in audio applications.
Limitations:
o Silicon transistors can age and fail.High-power, high-frequency operation,
such as that used in over-the-air television broadcasting, is better achieved in
vacuum tubes due to improved electron mobility in a vacuum.
• Solid-state devices are more vulnerable to Electrostatic discharge in handling and
operation
• A vacuum tube momentarily overloaded will just get a little hotter; solid-state devices
have less mass to absorb the heat due to overloads, in proportion to their rating
• Sensitivity to radiation and cosmic rays (special radiation hardened chips are used for
spacecraft devices).
• Vacuum tubes create a distortion, the so-called tube sound that some people find to be
more tolerable to the ear.

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WORKING:
We are giving 220 volts ac as a input to the transformer. We are using step down
transformer it serves to reduce the pressure remaining 12 volts, through a D1-D4 connected
to Direct rectifier bridge circuit. This rectifier converts ac to dc but the obtained dc is not pure
dc it is a pulsating dc, to obtain pure dc we are using regulator (ICLM7812) so that we can
obtain pure dc. Here the capacitors are used for filtering. In the regulator the voltage across
the pins 1 and 2 will be the input and output will be from the pins 2and 3.
Here we are using another IC that is IC LM324 which as 14 pins. The 4th pin in this IC act as
V cc and the 11th pin will be grounded. Here we are using two zener diodes of 6.8v and 6v.
The 6.8 volts zener diode is connected to the 2nd pin of IC2/1 and 6 volts zener diode is
connected to the 5th pin of IC2/2. The voltage coming from the diodes D2 and D4 goes to 3rd
pin of IC2/1 and 6th pin of IC2/2. Here IC2/1 act as high voltage detector and IC2/2 act as
low voltage detector.
When the voltage obtained across the 3rd pin is greater than the voltage at the 3rd pin then
IC2/1(high voltage detector) will function and the switch will be closed and load will be and
LED glows. This is the indication of high voltage.

33
Summary:
• The 12 volt approach looks good, we don’t need:
• An electrician
• Expensive mounting
• Wires buried deep
• To worry about shock
• So far, except for the need of a transformer, 12V is a winner.
Disadvantages:
• In this project relay is use as it is making of sound so some noise pollution
• And it is specified of minimum range of the higher voltage and lower voltage.

34
CONCLUSION:
It will indicate the high voltage and low voltage. Due to this we can safe guard our
home appliances without damaging the equipments.
D2
1
3N250
2
4
3
T1
TS_PQ4_12
C1
470μF
C2
1μF
C3
1μF
R1
10kΩ
R2
10kΩ
R3
5kΩ
50kΩ R4
Key=A
50 % D3
02DZ4.7
8
4 RST OUT 3
2 TRI
LED1 D4
1N4007GP
D5
1N4007GP
Q1
2N3904
R5
1kΩ
LED2
R6
1kΩ
R7
10kΩ
R8
5kΩ
R10
50kΩ
Key=A 50 %
R9
10kΩ
D6
ZPD6.2
U1
LMC555CM
GND
1
7 DIS
VCC
6 THR
5 CON

BIBLOGRAPHY
38
WWW.elekfrospoji.si
WWW.onsemi.com
WWW.engineersgarage.com
WWW.microsystemservices.com
http://en.wikipedia.org/wiki/Voltage#Measuring_instruments
http://www.google.co.in/imgres?sa=X&biw=1366&bih=667&tbm=isch&tb
nid=EIOzNEVeJSnCwM:&imgrefurl=http://www.123rf.com/stock-photo/
high_voltage_sign.html&docid=OGYlqtjvcU61bM&imgurl=http://us
.123rf.com/400wm/400/400/skovoroda/skovoroda1111/skovoroda111100005
/11135588-high-voltage-sign-with-red-thunder-isolated-on-white-background.
jpg&w=1200&h=1200&ei=u11rUofCO8STiQfYl4GICw&zoo
m=1&iact=rc&page=1&tbnh=178&tbnw=178&start=0&ndsp=12&ved=1t:
429,r:10,s:0&tx=1040&ty=424

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