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1. INTRODUCTION
1.1 Concept of project:-`
Our basic aim by this project is to build a circuit which acts as a device to detect the exact location of a broken point of the wire inside the PVC jacket thus reducing the wastage of time as well as resources.
To detect the exact location of the broken wire inside the PVC jacket we employ our circuit with a hex inverter CMOS which uses its actions to control an oscillator which in return detects the presence of ac current and thus shows us the exact location till where the wire is intact and allowing the passage of current through it.
2. LITERATURE SURVEY
2.1 The system:-
Portable loads such as video cameras, halogen flood lights, electrical irons, hand drillers, 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 of wires at any point. In such a case most people go for replacing the core/cable, as finding the exact location of a broken wire is difficult. In 3 core cables, it appears almost impossible to detect a broken wire and the point of break without physically disturbing all the three wires that are concealed in a PVC jacket.
3.2 Block diagram description:-
1.POWER SUPPLY :-
It provides3V dc supply for the whole Circuit.
2.OSCILLATOR CIRCUIT :-
The oscillator circuit oscillatesaround at1000 hertz in audio range.
3.PULSE GENERATOR :-
In this circuit gate N3 and N4 are used as a pulse generator that oscillatesaround at 1000 hertz frequency.
4.SENSOR :-
In this circuit LED is used as a sensor .
Circuit diagram operation:-
Portable loads such as video cameras,halogen flood lights, electrical irons, hand drillers, 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 of wires at any point. In such a case most people go for replacing the core/cable, as finding the exact location of a broken wire is difficult. In 3 core cables, it appears almost impossible to detect a broken wire and the point of break without physically disturbing all the three wires that are concealed in a PVC jacket.The circuit presented here can easily and quickly detect a broken/faulty wire and its breakage point in 1 core, 2 core, and 3 core cables without physically disturbing wires. It is built using hex inverter CMOS CD4069. Gates N3 and N4 are used as a pulse generator that oscillates at around 1000 Hz in audio range. Thefrequency 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 halfcycle, output pin 10 of gate N2 goes high. Thus during every positive half cycle of the mains frequency, the oscillator circuit is allowed to oscillate at around 1 kHz, making red LED (LED1) to blink. (Due to the persistence of vision, the LED appears to be glowing continuously.) This type of blinking reduces consumption of the current from button cells used for power supply. A 3V DC supply is sufficient for powering the whole circuit. AG13 or LR44 type button cells, which are also used inside laser pointers or in LED based continuity testers, can be used for the circuit. The circuit consumes 3 mA during the sensing of AC mains voltage. For audio visual indication, one may use a small buzzer (usually built inside quartz alarm time pieces) in parallel with one small (3mm) LCD in place of LED1 and resistor R5. In such a case, the current consumption of the circuit will be around 7 mA. Alternatively, one may use two 1.5V R6 or AA type batteries. Using this gadget, one can also quickly detect fused small filament bulbs in serial loops powered by 230V AC mains. The whole circuit can be accommodated in a small PVC pipe and used as a handy broken wire detector. 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 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. While testing a broken3 core rounded cable wire, bend the probe’s edge in the form of ‘J’ to increase its sensitivity and move the bent edge of the test probe closer over the cable. During testing avoid any strong electric field close to the circuit to avoid false detection.
General description of IC CD 4069 UB:-
The CD4069UB consists of six inverter circuits and 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. This device is intended for all general purpose inverter applications where the special characteristics of the MM74C901,MM74C907, and CD4049A Hex Inverter/BuffersAre 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.
5 PCB designing and Fabrication:-
3.5.1 Introduction to PCB:-
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non conductive substrate. It is also referred to as printed wiring board (PWB) or etched wiring board. A PCB populated with electronic components is a printed circuit assembly (PCA), also known as a printed circuit board assembly (PCBA).
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.
Conducting layers are typically made of thin copper foil. Insulating layers dielectricare typically laminated together with epoxy resinprepreg. The board is typically coated with a solder mask that is green in color. Other colors 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 polytetrafluoroethylene (Teflon), FR 4, FR 1, CEM 1 or CEM 3. Well known prepreg materials used in the PCB industry are FR 2 (Phenolic cotton paper), FR 3 (Cotton paper and epoxy), FR 4 (Woven glass and epoxy), FR 5 (Woven glass and epoxy), FR 6 (Matte glass and polyester). FR 4 is by far the most common material used today. The board with copper on it is called "copper clad laminate".
3.5.2 PCB fabrication steps
1) Layout of the circuit
2) Artwork designing
3) Printing
4) Etching
5) Drilling
6) Mounting of components and soldering
Layout :-
For layout we require Detailed circuit diagram, the design concept and the philosophy behind the equipment. First entire circuit diagram made on “EAGLE” OR “PCB 123” software. After making circuit diagram check any error present or not, and then schematic circuit diagram is converted into board by board command. The followings are the standards for width of holes and conducting copper line on pcb board.
A) Holes B) Conductor Widths
Standard holes Standard width, 0.5 mm
1.1 mm 1 mm
1.5 mm 2 mm
3.2 mm 4 mm
Artwork:-
The generation of PCB artwork should be considered as the first step of the PCB manufacturing process. After converting into the board there mirror image is print on the white transparent paper using printer.
Screen Printing:-
Line art and text may be printed onto the outer surfaces of a PCB by screen printing. When space permits, the screen print text can indicate component designators, switch setting requirements, test points, and other features helpful in assembling, testing, and servicing the circuit board.Screen print is also known as the silk screen, or, in one sided PCBs, the red print.Lately some digital printing solutions have been developed to substitute the traditional screen printing process.The screen-printing process is very simple. A screen fabric with uniform meshes and opening is stretched and fixed on a solid frame of metal or wood. The circuit pattern area open, while the meshes in the rest of the area is closed. In the actual printing step, ink is forced by the moving squeeze through the open meshes onto the surface of the material to be printed.
Pattern transfer onto the Screen:-
There are two different methods in use, and each method has its own advantages and disadvantages. With the direct method, we directly make the circuit diagram layout on the copper clad by using permanent black marker there is no need of exposing the light on to the paper and copper clad.
The indirect method makes use of a separate screen process film, supported on a backing sheet. The film on its backing sheet that is there after pressed onto the screen fabric and sticks there. Finally, the backing sheet is peeled off, opening all those screen meshes, which are not covered by the film pattern. The direct method provides very durable screen stencils with a higher dimensional accuracy but the finest details are not reproduced. The indirect method is more suitable for smaller series and where the finest details to be reproduced. The indirect method is faster as compare to direct and it is essential when circuit is complex.
Etching:-
In etching process we remove unwanted copper from the copper clad by deeping into the solution at high temperature near about 400degree C.
Solutions, which are used in etching process, are known as enchants.
I) Ferric Chloride
II) Cupric Chloride
III) Chromic Acid
IV) Alkaline Ammonia.
Out of these Ferric Chloride is widely used because it has short etching time and it can be stored for a long time. Tank or bubble etching, in which the boards kept in tank, were lowered and fully immersed into the agitated, has almost disappeared.
Drilling :-
Holes through a PCB are typically drilled with tiny drill bits made of solid tungsten carbide. The drilling is performed by automateddrilling machines with placement controlled by a drill tape or drill file. These computer-generated files are also called numerically controlled drill (NCD) files or "Excellon files". The drill file describes the location and size of each drilled hole. These holes are often filled with annular rings (hollow rivets) to create vias. Vias allow the electrical and thermal connection of conductors on opposite sides of the PCB.
When very small vias are required, drilling with mechanical bits is costly because of high rates 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.
Component Mounting:-
After the printed circuit board (PCB) is completed, electronic components must be attached to form a functional printed circuit assembly or PCA (sometimes called a "printed circuit board assembly" PCBA). In through-hole construction, component leads are inserted in holes. In surface-mount construction, the components are placed on pads or lands on the outer surfaces of the PCB. In both kinds of construction, component leads are electrically and mechanically fixed to the board with a molten metal solder.
Soldering:-
The next process after the component mounting is soldering. There are a variety of soldering techniques used to attach components to a PCB. High volume production is usually done with machine placement and bulk wave soldering or reflow ovens, but skilled technicians are able to solder very tiny parts by hand under a microscope, using tweezers and a fine tip soldering iron for small volume prototypes. Here we are using iron soldering.
Iron soldering:-
Soldering iron consists of an insulating handle connected through a metal shaft, of a bit accurately makes contact with the component parts of the joint and solder and heats them up. The electrical heating element is located in the hollow shank or handles to heat the bit.
Procedure of Soldering:-
The points to be joined must be cleaned first and fluxed. The hard solder iron and solder wire is applied to the work. The melted solder becomes bright and fluid. The iron must be removed after sufficient time and joint is allowed to coal. At the end, finishing is done.finally we make our PCB and now it is ready to use.