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INVISIBLE BROKEN WIRE DETECTOR 1

1. INTRODUCTION

In our day to day life we are dealing with electricity as well as so many electrical equipments. In this electrical equipment the household appliances play a major role. So the fault occurring with them is also a major problem. Generally the fault seen is the breaking of wire inside the two layer or three layer cables or the short circuit between them. Portable loads such as video cameras, halogen flood lights, electrical irons, hand drill, grinders, and cutters are powered by connecting long 2- or 3-core cables to the mains plug. Due to prolonged usage, the power cord wires are subjected to mechanical strain and stress, which can lead to internal snapping or short circuiting of wires at any point. In such a case most people go for replacing the core/cable, as finding the exact location of a fault of the wire is difficult. In 3- core cables, it appears almost impossible to detect a fault portion of the wire and the point of break or short circuit without physically disturbing all the three Wires that are concealed in a PVC jacket.

Invisible Broken Wire Detector:

The circuit presented here can easily and quickly detect a faulty wire and its point of open circuit or short circuit in 1-core, 2-core, and 3-core cables without physically disturbing the wires. The circuit present here can work in the two modes of operation. One is the mode of invisible broken wire detector and the second as a short checker. The invisible broken wire detector exactly find the location of the fault due to the breakage of wire inside the cables while the second circuit will find whether the fault is a short circuit fault which is happening due to the burning of insulation inside the cables. Hence this circuit offers a simple and better way of finding the faults in the household appliances.

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Circuit Components

The circuit of invisible broken wire detector is a simple circuit which is built using a hex inverter CMOS IC CD4069. This IC has six inverters that is NOT gate. Out of these six inverters the gates N3 and N4 are used as a pulse generator that oscillates at around 1000Hz in the audio range. The frequency is determined by timing Components comprising resistors R3 and R4, and capacitor C1. Gates N1 and N2 are used to sense the presence of 230V AC field around the live wire and buffer weak AC voltage picked from the test probe. The voltage at output pin 10 of gate N2 can enable or inhibit the oscillator circuit. When the test probe is away from any high-voltage AC field, output pin 10 of gate N2 remains low. As a result, diode D3 conducts and inhibits the oscillator circuit from oscillating. Simultaneously, the output of gate N3 at pin 6 goes ‘low’ to cut off transistor T1. As a result, LED1 goes off. When the test probe is moved closer to 230V AC, 50Hz mains live wire, during every positive half cycle, output pin 10 of gate N2 goes high.

Figure.1. Circuit of Invisible Broken Wire Detector

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The combination of resistors R3 and R4 and the capacitor makes the timing circuit for this circuit. R-C circuits are useful where timing errors of a few percent are acceptable, but where accurate timing is a must, crystal oscillators or other circuits using stable resonators should be used. The oscillator circuit is often referred to as the clock, since it generates time intervals that are counted in some way to produce the desired timing interval. However, the simplest timers are based on the charging and discharging of a capacitor through a resistor or current source. This approach has been around for a long time, even though its accuracy is somewhat limited (1- 10 percent) The pins N3 and N4 act as pulse generators in order to sense and buffer the weak voltages. Simple pulse generators usually allow control of the pulse repetition rate (frequency), pulse width, delay with respect to an internal or External trigger and the high- and low-voltage levels of the pulses. These Oscillators are circuits that generate a continuous voltage output waveform at a required. Frequency with the values of the inductors, capacitors or resistors forming a frequency network. The transistor T1 is act as a switch that is it is used to energies the light emitting diode.

Here a transistor can be employed as an electronic switch. Operating a transistor as a switch means operating the switch either in saturation in cutoff but nowhere else in the load line because when in saturation condition the transistor act as a closed switch while in cutoff it is like an open switch .the whole circuit is powered using the 3v battery. The piezobuzzer provided in this circuit gives a beep sound when a short is found out in the cables. A continuity tester is handy for checking that there is a conducting path between two points. The following circuit has the advantage that it is very sensitive and it gives both a visual and audible indication of continuity

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The circuit diagram shows that the continuity tester is made up of a sensitive one- transistor switch which turns on a LED.

Figure.2. Short Checker

Here two contacts namely contact 1 and contact 2 is used as the probes. The piezobuzzer provided in there circuit will beep when there is a short circuit in between the two contacts. Here also the transistor is acting in its switching mode. The led provided in the circuit gives the visual indication. This circuit is also powered using the 3V dc supply.

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2. LITERATURE SURVEY

In our endeavor to built this project we have done substantial research on various aspects of winding in motors and also on internal and external connections of various day by day appliances. The main task was to find out a suitable topic which was simple enough to be done within the specified time, which worked with components we already studied, and which has considerable uses in the present day. All the information that we gathered from various books, articles, internet etc laid a foundation for our project. Thorough knowledge of these paved an easy way for implementing our project. In this fast changing world we don’t find much time in repairing or maintaining the appliances. The main components of our project are CMOS IC CD4069, BC547, and Diode 1N4148 which combines the advantages of both the CMOS technology as well as bipolar transistor on the monolithic chip

Objective:

The main objective of our mini project is to design a simple device which can perform efficiently for domestic purposes. Hence we choose this topic invisible broken wire detector. In this project we have analyzed the circuit thoroughly and by making some modifications the present circuit was created. So in this project we have implemented a new circuit which is a combination of invisible broken wire detector and the short checker. By the circuit we can find fault in the household appliances that is open circuit fault or short circuit fault. If it is an open circuit fault then we can easily determine the position of that fault. This circuit provides a better and cheaper way of finding the fault. If it is an open circuit fault then we can easily determine the position of that fault. People who don’t have any idea about this field can also use this circuit without any hazards.

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Power Saving

Even while considering the working aspects of this circuit only a 9V DC supply is required for the proper working of the whole circuit. The main advantage of this circuit is that it does not need contact with the live wire, hence it is free from shock or other hazards. With the help of this circuit we can find the fuse of bulbs, halogen bulbs, neon bulbs, sodium vapor bulbs and other colored bulbs that are difficult to find whether it’s in working condition, unless we give supply to it we never know that. This device helps in even finding exact location of broken wire and serves as a handy tool. For the audio indication we can efficiently use a small buzzer in parallel with the LED and resistor. In the case also the power consumption will be very less. Therefore there is no question of getting electrical shock or about the power loss occurring in the circuit. The construction and the maintenance can be carried out very easily. Since there are neither rotating parts nor do any parts come in contact in it there is hardly any tear and wear.

Assembling the Project:

The experiment invisible broken wire detector is not an ordinary detector; by some studies we combined a new circuit which is used to detect the short circuit in the cables. So with the help of our guide we started making knowledge about our circuit. Our next aim was to purchase the components. We did the same without any delay in the next week itself. We thoroughly examined all the components. Made a study about them and by testing we assured that they are in working condition. The components were mounted on the breadboard and were wired up. For a couple of times the circuit showed wrong results, connection mistakes burned up one of the IC , it was replaced and experiment continued until we got the indented result. As the circuit wasfoundtobeworkingperfectlyitwasnowsafetofabricateitonaprintedcircuitboard.

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So we decided to design a PCB for our circuit. Since we are dealing with the PCB for the first time. We give this job to a near by person who is expert in PCB designing. After designing the PCB we started soldering process. Soldering of the components took a long time as we were soldering for the first time and we couldn’t afford to make a mistake there. So we soldered slowly and most carefully trying not to short between components, and after a long time we succeeded in completing it. The circuit was tested randomly and was found to be error free and accurate. The invisible broken wire detector was then ready to use. In the next project date we showed our project to our guide. After this we submitted our project diary to our guide then the date of project presentation was decided and we presented our project in front of the faculties of our college. When the diary was got corrected we submitted the rough copy and then the fair.

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3. CIRCUIT DESCRIPTION

The mini project circuit is a simple circuit of invisible broken wire detector. The project gives an easy way to detect the normal types of cables fault. The circuit requires the following list of components in Table 1.

Table.1.Circuit components

1. Diode 1N 4148(3 no.s)

2. IC CD 4069

3. Transistor BC 547(2 no.s)

4. LED(2 no.s)

5. PCB

6. Piezobuzzer

7. Resistors

8. Capacitors

9. Mode control switch

10. Probe

11. AA Battery (2 no.s)

Familiarization of IC CD4069

An integrated circuit, commonly referred to as an IC, is a microscopic array of electronic circuits and components that has been diffused or implanted onto the surface of a single crystal, or chip, of semi conducting material such as silicon. It is

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called an integrated circuit because the components, circuits, and base material are all made together, or integrated, out of a single piece of silicon, as opposed to a discrete circuit in which the components are made separately and assembled later

Figure.3.Internal Circuit Diagram of CD4069

ICs range in complexity from simple logic modules and amplifiers to complete microcomputers containing millions of elements. The CD4069UB is a CMOS IC consists of six inverter circuits. It is manufactured using complementary MOS (CMOS) to achieve wide power supply operating range, low power consumption, high noise immunity, and symmetric controlled rise and fall times. CMOS logic is a newer technology, based on the use of complementary MOS transistors to perform logic functions with almost no current required. This makes these gates very useful in battery-powered applications. The fact that they will work with supply voltages as low as 3 volts and as high as 15 volts is also very helpful. Six inverter circuit means that the circuit consists of six NOT gates which is built using the complementary metal oxide semiconductor.

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Figure.4.Pin Diagram of CD4069

Complementary metal-oxide semiconductor is the semiconductor technology used in the transistors that are manufactured into most of today's computer microchips. Here both kinds of transistors are used in a complementary way to form a current gate that forms an effective means of electrical control. CMOS transistors use almost no power when not needed. As the current direction changes more rapidly, however, the transistors become hot. This characteristic tends to limit the speed at which microprocessors can operate. The terminal Vdd and Vss is simple the positive supply and the negative supply voltage that is applying to the IC. The inverter performs the basic logic operation called as inversion or complementation. The purpose of the inverter is to change the one logic level in to opposite level. This gate has only one input and one output. The output of a not gate for pulsed output is show below and the truth table 2.

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Table.2.Truthtable of an Inverter

 

 

 

 

INPUT

 

OUTPUT

 

 

 

 

High

 

Low

 

 

 

 

Low

 

High

 

 

 

 

 

 

 

This device is intended for all general purpose inverter applications where the special characteristics of the MM74C901, MM74C907, and CD4049A Hex Inverter/Buffers are not required. In those applications requiring larger Noise immunity the MM74C14 or MM74C914 Hex Schmitt Trigger is suggested. All inputs are protected from damage due to static discharge by diode clamps to VDD and VSS.

Figure.5.Output of an Inverter for Pulsed Input

Familiarization of IN4148

A semiconductor diode is simply a P-N junction with connecting leads or terminals on the two sides of the pn junction. A diode is a unidirectional device permitting the easy flow of current in direction but restraining the flow in other direction. The 1N4148 is a standard small signal silicon diode used in signal processing. Its name follows the JEDEC nomenclature. The 1N4148 is generally available in a DO-35 glass package and is very useful at high frequencies with a reverse recovery time of no more than 4ns. This permits rectification and detection of radio frequency

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signals very effectively, as long as their amplitude is above the forward conduction threshold of silicon (around0.7V) or the diode is biased The semiconductor Signal Diode is a small non-linear semiconductor devices generally used in electronic circuits, where small currents or high frequencies are involved such as in radio, television and digital logic circuits or where a low Value of capacitance is required in between the terminals of the device.

A signal diode is one of many types of diodes, which are small components of electrical circuits, manufactured from semiconductors that force electricity to flow in only one direction. Signal diodes which are also sometimes known by their older name of the Point Contact or Glass Diode are physically very small in size compared to their larger Power Diode cousins and control small currents up to about 100mA. Generally, the PN-junction of a signal diode is encapsulated in glass to protect it and they generally have a red or black band at one end of their body to help identify which end is its Cathode terminal. Signal diodes are designed to pass very small currents, and have several applications in the signal processing field. The most widely used of all the glass encapsulated signal diode is the very common 1N4148 signal diode show in figure.6

Figure.6.Diagram of 1N4148

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The arrow points in the direction of conventional current flow through the diode meaning that the diode will only conduct if a positive supply is connected to the Anode (A) terminal and a negative supply is connected to the Cathode (K) terminal thus only allowing current to flow through it in one direction only, acting more like a one way electrical valve, (Forward Biased Condition). However, we know that if we connect the external energy source in the other direction the diode will block any current flowing through it and instead will act like an open switch, in reverse biased mode as shown in figure.7

Figure.7. Diode in Forward and Reverse Biased Condition

The characteristics of a signal point contact diode are different for both germanium and silicon types and are given as: Germanium Signal Diodes - These have a low reverse resistance value giving a lower forward volt drop across the junction, typically only about 0.2-0.3v, but have a higher forward resistance value because of their small junction area. Silicon Signal Diodes - These have a very high value of reverse resistance and give a forward volt drop of about 0.6-0.7v across the

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junction. They have fairly low values of forward resistance giving them high peak values of forward current and reverse voltage. Signal Diodes are manufactured in a wide range of voltage and current ratings. There are bewildering arrays of static characteristics associated with the humble signal diode but the important ones are as follows Maximum Forward Current, Peak Inverse Voltage, and Maximum Operating Temperature.

Figure.8. Diode and its Characteristics

LightEmittingDiode:

A light-emitting diode (LED) is a semiconductor device that emits visible light when an electric current passes through it. The light is not particularly bright, but in most LEDs it is monochromatic, occurring at a single wavelength. The output from an LED can range from red (at a wavelength of approximately 700 nanometers) to

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blue-violet (about 400 nanometers). An LED consists of two elements of processed material called P-type semiconductorS and N-type semiconductorS. These two In this elements are placed in direct contact, forming a region called the P-N junction. In this respect, the LED resembles the most other type diode types, but there are Important other differences between the light emitting diode and the normal diodes.

Figure.9. Internal Diagram of a Light Emitting Diode

The LED has a transparent package, allowing visible or IR energy to pass through. Also, the LED has a large PN-junction area whose shape is tailored to the application. Light Emitting Diodes or LED´s, are among the most widely used of all the types of diodes available. They are the most visible type of diode that emits a fairly narrow bandwidth of either visible colored light, invisible infra-red or laser type light when a forward current is passed through them. A "Light Emitting Diode" or LED as it is more commonly called, is basically just a specialized type of PN- junction diode, made from a very thin layer of fairly heavily doped semiconductor

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material. When the diode is Forward Biased, electrons from the semiconductors conduction band combine with holes from the valence band, releasing sufficient energy to produce photons of light. Because of this thin layer a reasonable number of these photons can leave the junction and radiate away producing a colored light output. Light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps in many devices. The LED is based on the effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor. Like a normal diode, the LED consists of a chip of semi conducting material doped with impurities to create a p-n junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side, or cathode, but not in the reverse direction. Charge-carriers electrons and holes flow into the junction from electrodes with different voltages. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon. The wavelength of the light emitted, and therefore its color, depends on the band gap energy of the materials forming the p-n junction

Figure.10.LED and its Characteristics Curves

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The key advantages of LED-based lighting are its high efficiency, as measured by its light output per unit power input. LEDs are subject to very limited wear and tear if operated at low currents and at low temperatures. LEDs can be very small (smaller than 2 mm2) and are easily populated onto printed circuit boards. Low power requirement that is most types can be operated with battery power supplies. High efficiency that is Most of the power supplied to an LED is converted into radiation in the desired form, with minimal heat production. Long life that is when properly installed, an LED can function for decades.

RC Timing Circuit:

Timers and timing circuits are used in a wide variety of applications. From short time delays of a few nanoseconds used in digital circuitry and computers, to long periods of thousands of hours, used to control daily, weekly, or yearly events, electronic circuits can provide this function reliably, accurately and repeatable, with no need to provide any user input or monitoring once the time has been set. The voltage across a capacitor is equal to the charge on it divided by the capacitance, in any consistent system of units. Charge is usually measured in Coulombs, and capacitance in Farads. Current is defined as a flow of charge. The Ampere, or unit of current, is defined as that current produced by one coulomb of charge flowing across a given surface in one second. A one ohm resistor will show a 1 volt drop across it with one ampere (or one coulomb per second) flowing through it. In a practical situation, the presence of one ampere of current in a wire signifies that one coulomb of charge flows past a given point in one second. A one farad capacitor will have a charge of one coulomb when there is one volt of potential difference between the plates. If we connect a one ampere current source across a one farad capacitor, the voltage across it will rise at the rate of one volt per second,

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continuing to rise at this rate as long as the charging current remains constant. By knowing the current and the capacitance, we can accurately predict how long it will take to reach a certain voltage. This voltage may be that needed to produce some desired action. Conversely, if we know the capacitance, final voltage needed to produce that action, and the time delay desired, we can calculate the necessary charging current. This can be used as a basis for a timer circuit.

Figure.11. RC Charging Circuit

When the switch S1 is closed and S2 is opened, voltage V is applied to the circuit. C1 has initially (and ideally) zero voltage across it and an initial current equalling V/R flows. However, the voltage across C1 starts to rise, and now the voltage across R1 is slightly less. This causes the charging current to drop. This process continues, the current dropping as the capacitor charges toward a final value equal to the voltage V The exact waveform of the current is given by the mathematical plot of the function e^-αt where α = 1/RC and t = time.

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The equation is given by di(t)/dt + i(t) / RC = 0, This differential equation says that i(t) has a rate of change with respect to time that equals the original current I(t) divided by RC.

Transistor BC547 as a Switch:

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. Transistors are commonly used as electronic switches, for both high power applications including switched-mode power supplies and low power applications such as logic gates. 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. When used as an AC signal amplifier, the transistors Base biasing voltage is applied so that it operates within its "Active" region and the linear part of the output characteristics curves are used. However, both the NPN & PNP type bipolar transistors can be made to operate as an "ON/OFF" type solid state switch for controlling high power devices such as motors, solenoids or lamps.

Figure.12. Terminals of BC547

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If the circuit uses the Transistor as a Switch, then the biasing is arranged to operate in the output characteristics curves Seen previously in the areas known as the "Saturation" and "Cut-off" regions as shown below.

Figure.12.Load Line Diagram

The shaded area at the bottom represents the "Cut-off" region. Here the operating conditions of the transistor are zero input base current (Ib), zero output collector current (Ic) and maximum collector voltage (Vce) which results in a large depletion layer and no current flows through the device. The transistor is switched "Fully- OFF". The area to the left represents the "Saturation" region. Here the transistor will be biased so that the maximum amount of base current is applied, resulting in Maximum collector current flow and minimum collector emitter voltage which results in the depletion layer being as small as possible and maximum current flows

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through the device. The transistor is switched "Fully-ON". Then we can summarize this as: Cut-off Region - junctions are Reverse-biased, Base current is zero or very small resulting in zero Collector current flowing, and the device is switched fully "OFF". Saturation Region - Both junctions are Forward-biased, Base current is high enough to give a Collector-Emitter voltage of 0v resulting in maximum Collector current flowing, the device is switched fully "ON".

Table.3. Maximum Ratings of BC 547

AA Battery

An AA battery is a standard size of battery. Batteries of this size are commonly used in portable electronic devices. An AA battery is composed of a single electrochemical cell. The exact terminal voltage and capacity of an AA size battery depends on the cell chemistry. Some rechargeable cells are made in the AA size. AA batteries have around 400–900 milliamp-hours capacity, depending entirely on test conditions, duty cycle, and cut-off voltage selected. A zinc-carbon dry cell or battery

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is packaged in a zinc can that serves as both a container and negative terminal. Zinc-carbon batteries are the least expensive primary batteries and thus a popular choice by manufacturers when devices are sold with batteries included. They are commonly labeled as "General Purpose" batteries. They can be used in remote controls, flashlights, clocks, or transistor radios, since the power drain is not too heavy.

Figure.14. AA Battery

Piezobuzzer

A piezoelectric buzzer is a device that uses the piezoelectric effect to measure pressure, acceleration, strain or force by converting them to an electrical signal. Piezoelectric buzzer has proven to be versatile tools for the measurement of various processes. They are used for quality assurance, process control and for research and development in many different industries. A piezoelectric transducer has very high DC output impedance and can be modeled as a proportional voltage source and filter network. The voltage V at the source is directly proportional to the applied force, pressure, or strain. The output signal is then related to this mechanical force as if it

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had passed through the equivalent circuit. However, it is not true that piezoelectric buzzer can only be used for very fast processes or at ambient conditions. Even though piezoelectric buzzers are electromechanical systems that react to compression, the sensing elements show almost zero deflection. This is the reason why piezoelectric buzzer are so rugged, have an extremely high natural frequency and an excellent linearity over a wide amplitude range. Additionally, piezoelectric technology is insensitive to electromagnetic fields and radiation, enabling measurements under harsh conditions.

Figure.15. Piezobuzzer

The piezobuzzer is chosen depending upon the various parameters that is, normally, the operating voltage for a magnetic buzzer is from 1.5V to 24V, for a piezo buzzer is from 3V to 220V. However, in order to get enough SPL, we suggest giving at least 9V to drive a piezo buzzer. According to the different voltage, the consumption current of a magnetic buzzer is from dozens to hundreds of mill amperes; oppositely, the piezo type saves much more electricity, only needs a few mill amperes, and consumes three times current when the buzzer start to work. Both magnetic and piezo buzzer have self drive type to choose. Because of the internal set drive circuit, the self drive buzzer can emit sound as long as connecting with the direct current.

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4. CIRCUIT WORKING

The circuit of our mini project consists of invisible broken wire detector and the short checker which works on the mode control basis. The switch which controls the circuit has 6 terminals. In the mode of invisible broken wire detector the switch terminals 2 and 3 will be connected and in short checker mode terminals 1 and 2 will be connected. The 3V AA battery provides supply for both the circuits.

Figure.16.Circuit Diagram

Invisible Broken Wire Detector:

In the case of invisible broken wire detector the terminals 3 and 2 of SW1A and that of SW1B will be in contact with each other. In this mode probe 1 is enough to find the location of the fault. When the circuit is powered with the battery, the Vss and Vdd

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is required to bias the integrated chip is applied to the 14th pin of the IC. When the probe if away from the strong ac field the output pin of the gate N2 remains low due to the unavailability of the signal so that the diode D3 will be conducting and inhibits the oscillator from oscillating. Simultaneously the output of the gate N3 at pin 6 will become also low. Therefore the transistor will be forced to work in the cut off mode of operation or transistor will act as an open switch. As a result of this the LED1 goes of which shows the presence of the broken fault.

Now let us consider that the probe is moved near to a cable which is flowing with 230V ac supply 50 Hz live wire, the diode D1 will clip off the each negative half cycle and the gates N1 and N2 will be used to buffer the weak signal picked up by the test probe that is an amplifying action. The diode D2 is used to suppress the negative half cycles of the 50 Hz frequency. Therefore the output pin of gate N2 high which is buffered by the previous gates. And for every half cycle of the frequency the oscillator is allowed to oscillates around the frequency of 1 kHz .this makes the output of gate N3 high and the transistor conducts and become acting like a closed switch making the LED to blink continuously showing the presence of the strong electric field. This blinking of the LED reduces the consumption of current from the battery which is used to power the circuit. In short IC CD4069 picks up the weak signal in presence of electrical field making the transistor switch on and making the LED glow and in the absence of electric field making the transistor switch open and hence making the LED off.

Short Checker:

This circuit is used to find whether there is a short circuit in a cable. This can be done only on a floating wire other wise it may lead to wrong result. In the short checker mode the terminals 2 and 1 of SW1A and SW1B will be in contact with each other.

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And the major thing to notice is that this checking can be carried out only with the help of both the probes. Here voltage is applied to the probe 2 and probe one is connected to the base of transistor. Some times the fault occurring is due to the short inside the cable so the cable is removed from the appliance making it in floating condition. Now both probes are connected to the two wires inside the cable. If there is a short inside the wire then there will be conducting path in between probe1 and probe2 and making the transistor conducting that is ON and hence the piezobuzzer will beep and the LED will glow give both audio and visual indication about the fault. If there is no short circuit in the wire there will not be any connection path in between the two probes and hence there will not be any indication and in this way we can find the short circuit fault also. This is the general working of a little modified version of the invisible broken wire detector.

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5. PCB ASSEMBLING

A printed circuit board, or PCB, is a self-contained module of interconnected electronic components found in devices ranging from common beepers, or pagers, and radios to sophisticated radar and computer systems. Printed circuit boards, PCBs, form an essential part of any electronics equipment these days. The PCB design and layout forms an integral part of the design of the whole product, and it can be the key to the success of the product meeting its performance requirements in many instances The connections on the PCB should be identical to the circuit diagram, but while the circuit diagram is arranged to be readable, the PCB layout is arranged to be functional, so there is rarely any visible correlation between the circuit diagram and the layout. The circuits are formed by a thin layer of conducting material deposited, or "printed," on the surface of an insulating board known as the substrate. Individual electronic components are placed on the surface of the substrate and soldered to the interconnecting circuits. Contact fingers along one or more edges of the substrate act as connectors to other PCBs or to external electrical devices such as on-off switches. A printed circuit board may have circuits that perform a single function, such as a signal amplifier, or multiple functions.

Schematic Capture:

Schematic capture or schematic entry is a step in the design cycle of electronic design automation (EDA) at which the electronic diagram, or electronic schematic of the designed electronic circuit is created by a designer. This is done interactively with the help of a schematic capture tool also known as schematic editor. The circuit. Design is the very first step of actual design of an electronic circuit typically sketches are drawn on paper, and then entered into a computer using a schematic editor.

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Therefore schematic entry is said to be a front-end operation of several others in the design flow. CAD software is easier to use and is available in full-featured expensive packages, very capable mid-range packages that sometimes have free versions and completely free versions that are either open source or directly linked to a printed circuit board fabrication company. When the PCB design has been finalized and checked, it is printed out onto butter sheet using a laser printer. You need to be careful because some acetate sheets are designed for use in laser printers and others are designed for use in photocopiers. If you use the wrong type, the butter sheet may melt and glue up the inside of the printer/photocopier.

Photo Engraving and PCB Milling:

After taking the print out Next, you need to get a piece of photo-etch circuit board. This consists of a sheet of insulating material, such as fiber glass. On top of the fiber glass, there is a thin layer of copper which covers the whole of the board and on top of that there is a layer of photographic emulsion. Finally, there is a layer of black plastic which protects the emulsion and prevents it from being exposed to daylight. Photo-etch board is expensive. Cut it down to the right size for your PCB before you do anything else.

A PCB milling machine is referred to as a pcb prototype operates in a similar way to a plotter, receives a command from the host software that controls the position of the milling head. Now the layout available in the butter sheet is now ready for screen printing. For this purpose we have to choose a material board know as copper clad having dimension as that of our printed circuit board. Copper clad is a plate having the layers of copper tin and lead. Therefore the copper clad obtained after the screen printing have the marks of the layout in its surface.

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Dipping in the Solution Exposed Plating and Coating:

Place your board design between iron and the blank PCB that you had cut out. Place iron on board, and push down really hard. Wait for it to cool down. After ironing go over your tracks with an etch resistant pen to fix any possibly damaged tracks. Put under cold water and carefully peel the glossy. Place PCB into ferric chloride and wait for the copper around the track you want to totally dissolve. While the board is in the ferric chloride agitate the container. The process can be sped up by putting the ferric chloride container, in a bucket of hot water, to heat up the ferric chloride. Take the board from the solution, the board thus contains only the tracks which is exactly as in the layout and the excess around the tracks will be washed away.

Figure.17.Layout

Drilling:

Some PCB has trace layers inside the PCB and are called multi layer PCBs. These are formed by bonding together separately etched thin boards holes through a PCB Are typically drilled with tiny frill bits made of solid tungsten carbide.

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The drilling is performed by the automated drilling machines with placement controlled by a drill tape or drill file. Vias allow electrical and thermal connection of the conductors on opposite sides of the PCB. When very small vias are required, drilling with mechanical bits is costly because high tares of wear and breakage. In this case, the vias may be evaporated by lasers. Laser drilled vias typically have an inferior surface finish inside the hole. These holes are called micro vias.

Placing the Components and Soldering:

Now the PCB after drilling is ready for soldering. Now the components are placed in the PCB as shown in the connection layout diagram. Flux is lightly applied on the surface that is to be soldered. The components placed are soldered carefully with the help of a solder and removed the excess connecting leads. Now the circuit is mounted on the PCB is and can be contained is a cabinet of suitable size and is ready to use.

Figure.18.Connection Layout

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6. RESULTS AND DISCUSSION

Completed the project work and submitted it in front of the project guide. For the purpose of the demonstration we detected both open circuit and short circuit fault in front of our guide. To detect the breakage point, turn on switch S1 and slowly move the test probe closer to the faulty wire, beginning with the input point of the live wire and proceeding towards its other end. LED1 starts glowing during the presence of AC voltage in faulty wire. When the breakage point is reached, LED1 immediately extinguishes due to the non-availability of mains AC voltage. The point where LED1 is turned off is the exact broken-wire point. And that is the result of our project. The entire cost of out projects is up to the half of the products available in the market including the price of electronics components. The circuit is very efficient in operation

Testing:

Before detecting broken faulty wires, take out any connected load and find out the faulty wire first by continuity method using any multimeter or continuity tester. Then connect 230V AC mains live wire at one end of the faulty wire, leaving the other end free. Connect neutral terminal of the mains AC to the remaining wires at one end. However, if any of the remaining wires is also found to be faulty, then both ends of these wires are connected to neutral. For single-wire testing, connecting neutral only to the live wire at one end is sufficient to detect the breakage point. In this circuit, a 5cm (2-inch) long, thick, single-strand wire is used as the test probe. To detect the breakage point, turn on switch S1 and slowly move the test probe closer to the faulty wire, beginning with the input point of the live wire and proceeding towards its other end. LED1 starts glowing during the presence of AC voltage in faultywire.

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When the breakage point is reached, LED1 immediately Extinguishes due to the non-availability of mains AC voltage. The point where LED1 is turned off is the exact broken-wire point.

Advantages and Disadvantages:

The circuit invisible broken wire detector is a simple circuit which consists of some active as well as passive devices. The circuit presented here is very cheap. The total cost of this circuit including fabrication of PCB will be around 500 Rs. The circuit is very reliable. A 9V DC supply is sufficient for powering the whole circuit; any type of AA size battery can be used for the circuit. The circuit consumes 3 mA during the sensing of AC mains voltage. Hence only small amount of power is required since the circuit is small the whole circuit can be accommodated in a small box and used as a handy detector.

During the testing of the circuit the presence of high electric field near the circuit may lead to false detection. When the number of core increases the sensitivity decreases, this lead to the failure in detection. The short checker can be used only under floating condition. These were the major disadvantage that is faced by the circuit invisible broken wire detector advanced.

Chances of Further Advancement:

For visual indication, one may Use a LCD in place of LED1 and resistor R5. In such a case, the current consumption of the circuit will be around 7 mA. Or by using the microprocessor or micro controller by doing the suitable programming we can make this circuit to find the fault in more than 3 core cables having long length

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CONCLUSION

Faults in electrical appliances are common in our day today life. This occurs due to ageing, mechanical stresses, overloads etc. These situations are unavoidable in the case of any home appliances. Faults in home appliances will create difficulties in doing the works at home. We are living in a busy society and we don’t have any time to find the faults in appliances or in cables. For this reason people will have a mentality of use and throw. This will create lot of environmental problems such as soil pollution, undegradable material explosion, ozone layer depletion and other sorts of pollutions. For these reasons we have to recycle the products or to repair the appliances. Invisible broken wire detector with short checker is a simple and handy device which helps us to find the faults. The circuit can be used to find whether the fault is in the cable or in the appliance. If the fault is dealt within the cable we can find it by using the circuit, or fault may be in the appliance. The circuit invisible broken wire detector provides us the easy way of finding and replacing the cables which is not properly working due to the fault. The heart of the system CD4069 makes the detection very easy. The light emitting diodes and the piezobuzzer gives the indication. The basic concept of this circuit is that when a supply flows through a cable a magnetic field of particular frequency will be available in the outer layer of the core. The detection of this frequency is the basis of finding the fault. The circuit invisible broken wire detector is a simple circuit which consists of some active as well as passive devices. The circuit presented here is very cheap. The total cost of this circuit including fabrication of PCB will be around 500 Rs. A 9V DC supply is sufficient for powering the whole circuit, any type of AA size battery can be used for the circuit. The circuit is very reliable. This is a very good device which can be used in all houses for the detection of the fault in our day to day using appliances.

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REFERENCES

1.http://www.answers.com/topic/circuit-board

2.http://www.electronics-tutorials.ws

3.http://www.ehow.com/how_5311761_make-printed-circuit-board-pcb.html.

4.http://www.fairchildsemi.com/ds/CD/CD4069UBC.pdf

5.http://www.techlib.com

6.Electronic Devices and Circuits (Twenty Second Edition, 1999), G.K.Mithal

7.Electronics for You, August 2001

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