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Invisible Broken Wire Detector Amity University Uttar Pradesh Amity School of Engineering and Technology Practical Training Report On Guided By: Submitted by: 1 Invisible Broken Wire Detector ACKNOWLEDGEMENT I would like to acknowledge the help of Mr. and Ms. under whose supervision we have completed our in house Practical Training. We are thankful to them for their great support and help. Without their able guidance, we would not been able to complete our Practical Training. They were helpful throughout the training working in guiding us and helping us to complete our work. The hardware testing and construction has been prepared by our group while working in the college laboratories throughout the training period. The information covered in this report is true to the best of our knowledge. The relevant references have also been mentioned. I am also thankful to almighty God and my parents with whose blessings I was able to successfully complete my Practical Training project. Thanking you. Yours sincerely 2 Invisible Broken Wire Detector INDEX 1. Introduction 5 2. Materials and Methods 6 3. Components and Methodology Used CMOS 7 CMOS HEX INVERTER CD 4069 9 CMOS Pulse Oscillators 11 AG13 OR LR44 TYPE BUTTON CELLS 17 Diodes used (1N4148) 19 Transistor used (BC547) 20 Resistors used 24 Light Emitting Diode 28 4. Results and Discussions 30 5. Conclusions and Recommendations 31 6. References 31 7. Appendix xx ABSTRACT 3 Invisible Broken Wire Detector In our day to day life we use various electronic appliances employing various complex components in there circuitry. And in the present era everyone is over dependent on electronic gadgets, we use them as phones for communication, as a microwave for cooking, as a camera for taking pictures. All these modern day gadgets are having there power supply wires covered with a pvc jackets for the protection of both the wire as well as the user from getting electric shock. But sometime this protection also becomes a cause of problem for the user. Whenever the inner wire breaks, the device becomes inactive and the user cannot easily detect what is the reason. 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 entire wire. 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. So we have built a circuit which can easily detect the exact location of the broken wire and thus reduces unnecessary expenses of the user. 4 Invisible Broken Wire Detector INTRODUCTION 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 without physically damaging 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 which employs 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 . For this purpose we move our test probe across the faulty wire and wherever the LED goes off that point is the broken point of the wire .The LED is glowing till the wire is getting ac supply and as soon as the broken point arises the LED goes off as the ac supply is no more available. The inverter gates detect the presence of the ac voltage and thus signals it to the oscillator circuit which in turn directs the LED. 5 Invisible Broken Wire Detector MATERIALS AND METHODS Process methodology 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. 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. 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. The whole circuit can be 6 Invisible Broken Wire Detector 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 broken 3-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. COMPONENTS AND METHODOLOGY USED CMOS Complementary metal–oxide–semiconductor (CMOS) is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits. CMOS technology is also used for several analog circuits such as image sensors, data converters, and highly integrated transceivers for many types of communication. CMOS is also sometimes referred to as complementary-symmetry metal– oxide–semiconductor (or COS-MOS). The words "complementary-symmetry" refer to the fact that the typical digital design style with CMOS uses complementary and symmetrical pairs of p- type and n-type metal oxide semiconductor field effect transistors (MOSFETs) for logic 7 Invisible Broken Wire Detector functions. CMOS circuits are constructed so that all PMOS transistors must have either an input from the voltage source or from another PMOS transistor. Similarly, all NMOS transistors must have either an input from ground or from another NMOS transistor. The composition of a PMOS transistor creates low resistance between its source and drain contacts when a low gate voltage is applied and high resistance when a high gate voltage is applied. On the other hand, the composition of an NMOS transistor creates high resistance between source and drain when a low gate voltage is applied and low resistance when a high gate voltage is applied. When the voltage of input A is low, the NMOS transistor's channel is in a high resistance state. This limits the current that can flow from Q to ground. The PMOS transistor's channel is in a low resistance state and much more current can flow from the supply to the output. Because the resistance between the supply voltage and Q is low, the voltage drop between the supply voltage and Q due to a current drawn from Q is small. The output therefore registers a high voltage. On the other hand, when the voltage of input A is high, the PMOS transistor is in an off (high resistance) state so it would limit the current flowing from the positive supply to the output, while the NMOS transistor is in an on (low resistance) state, allowing the output to drain to ground. Because the resistance between Q and ground is low, the voltage drop due to a current drawn into Q placing Q above ground is small. This low drop results in the output registering a low voltage. In short, the outputs of the PMOS and NMOS transistors are complementary such that when the input is low, the output is high, and when the input is high, the output is low. Because of this opposite behavior of input and output, the CMOS circuits' output is the inversion of the input. Two important characteristics of CMOS devices are high noise immunity and low static power consumption. Significant power is only drawn while the transistors in the CMOS device are switching between on and off states. Consequently, CMOS devices do not produce as much waste heat as other forms of logic, for example transistor-transistor logic (TTL) or NMOS logic, which uses all n-channel devices without p-channel devices. CMOS also allows a high density of logic functions on a chip. The phrase "metal–oxide–semiconductor" is a reference to the physical structure of certain field-effect transistors, having a metal gate electrode placed on top of an oxide insulator, which in turn is on top of a semiconductor material. 8 Invisible Broken Wire Detector CMOS HEX INVERTER CD 4069 General Description 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/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 diode clamps to VDD and VSS. Features Wide supply voltage range: 3.0V to 15V High noise immunity: 0.45 VDD type Low power TTL compatibility: Fan out of 2 driving 74L Operating Temperature Range (TA) −55°C to +125°C Power Dissipation (PD): 9 Invisible Broken Wire Detector Schematic Diagram Absolute Maximum Ratings “Absolute Maximum Ratings” are those values beyond which the safety of the device cannot be guaranteed. They are not meant to imply that the devices should be operated at these limits. DC Supply Voltage (VDD) −0.5V to +18 VDC Input Voltage (VIN) −0.5V to VDD +0.5 VDC Storage Temperature Range (TS) −65°C to +150°C Power Dissipation (PD) Dual-In-Line 700 mW Small Outline 500 mW Lead Temperature (TL) (Soldering, 10 seconds) 260°C Recommended Operating Conditions The table of “Recommended Operating Conditions” and Electrical Characteristics table provide conditions for actual device operation. DC Supply Voltage (VDD) 3V to 15VDC Input Voltage (VIN) 0V to VDD VDC Operating Temperature Range (TA) −55°C to +125°C VSS = 0V unless otherwise specified. 10 Invisible Broken Wire Detector CMOS Pulse Oscillators Introduction There are several square wave oscillators that can be built using CMOS logic elements. These circuits offer the following advantages: • Guaranteed start ability • Relatively good stability with respect to power supply variations • Operation over a wide supply voltage range (3V to 15V) • Operation over a wide frequency range from less than 1 Hz to about 15 MHz • Low power consumption (see AN-90) • Easy interface to other logic families and elements including TTL Several RC oscillators and two crystal controlled oscillators are described. The stability of the RC oscillator will be sufficient for the bulk of applications; however, some applications will probably require the stability of a crystal. Some applications that require a lot of stability are: 1. Timekeeping over a long interval. A good deal of stability is required to duplicate the performance of an ordinary wrist watch (about 12 ppm). This is, of course, obtainable with a crystal. However, if the time interval is short and/or the resolution of the timekeeping device is relatively large, an RC oscillator may be adequate. For example: if a stopwatch is built with a resolution of tenths of seconds and the longest interval of interest is two minutes, then an accuracy of 1 part in 1200 (2 minutes x 60 seconds/minute x 10 tenth/second) may be acceptable since any error is less than the resolution of the device. 2. When logic elements are operated near their specified limits. It may be necessary to maintain clock frequency accuracy within very tight limits in order to avoid exceeding the limits of the logic family being used, or in which the timing relationships of clock signals in dynamic MOS memory or shift register systems must be preserved. 3. Baud rate generators for communications equipment. 4. Any system that must interface with other tightly specified systems. Particularly those that use a “handshake” technique in which Request or Acknowledge pulses must be of specific widths. 11 Invisible Broken Wire Detector LOGICAL OSCILLATOR Before describing any specific circuits, a few words about logical oscillators may clear up some recurring confusion. Any odd number of inverting logic gates will oscillate if they are tied together in a ring as shown in Figure. Many beginning logic designers have discovered this (to their chagrin) by inadvertently providing such a path in their designs. However, some people are confused by the circuit in Figure below because they are accustomed to seeing sine wave oscillators implemented with positive feedback, or amplifiers with non-inverting gain. Since the concept of phase shift becomes a little strained when the inverters remain in their linear region for such a short period, it is far more straightforward to analyze the circuit from the standpoint of ideal switches with finite propagation delays rather than as amplifiers with 180° phase shift. It then becomes obvious that a “1” chases itself around the ring and the network oscillates. Figure: Odd Number of Inverters will always oscillate The frequency of oscillation will be determined by the total propagation delay through the ring and is given by the following equation. Where: f = frequency of oscillation Tp = Propagation delay per gate n = number of gates This is not a practical oscillator, of course, but it does illustrate the maximum frequency at which such an oscillator will run. All that must be done to make this a useful oscillator is to slow it down to the desired frequency. To determine the frequency of oscillation, it is necessary to examine the propagation delay of the inverters. CMOS propagation delay depends on supply voltage and load capacitance. Several curves for propagation delay of CMOS gates can be reproduced. From these, the natural frequency of oscillation of an odd number of gates can be determined. 12 Invisible Broken Wire Detector STABLE RC OSCILLATOR Figure below illustrates a useful oscillator made with three inverters. Actually, any inverting CMOS gate or combination of gates could be used. This means left over portions of gate packages can be often used. Figure: Three Gate Oscillator The duty cycle will be close to 50% and will oscillate at a frequency that is given by the following expression: 13 Invisible Broken Wire Detector Figure: Waveforms of Oscillator The voltage V2 will be clamped by input diodes when V1 is greater than VCC or more negative than ground. During this portion of the cycle current will flow through R2. At all other times the only current through R2 is a very minimal leakage term. Note also that as soon as V1 passes through threshold (about 50% of supply) and the input to the last inverter begins to change, V1will also change in a direction that reinforces the switching action; i.e., providing positive feedback. This further enhances the stability and predictability of the network. This oscillator is fairly insensitive to power supply variations due largely to the threshold tracking close to 50% of the supply voltage. Just how stable it is will be determined by the frequency of oscillation; the lower the frequency the more stability and vice versa. This is because propagation delay and the effect of threshold shifts comprise a smaller portion of the overall period. Stability will also be enhanced if R1 is made large enough to swamp any variations in the CMOS output resistance. TWO GATE OSCILLATOR WILL NOT NECESSARILY OSCILLATE A popular oscillator is shown in Figure (a). The only undesirable feature of this oscillator is that it may not oscillate. This is readily demonstrated by letting the value of C go to zero. The network then degenerates into Figure (b), which obviously will not oscillate. This illustrates that there is some value of C1 that will not force the network to oscillate. The real difference between this two gate oscillator and the three gate oscillator is that the former must be forced to oscillate by 14 Invisible Broken Wire Detector the capacitor while the three gate network will always oscillate willingly and is simply slowed down by the capacitor. The three gate network will always oscillate, regardless of the value of C1 but the two gate oscillator will not oscillate when C1 is small. (a) (b) Figure: Less than Perfect Oscillator The only advantage the two gate oscillator has over the three gate oscillator is that it uses one less inverter. This may or may not be a real concern, depending on the gate count in each user‟s specific application. However, the next section offers a real minimum parts count oscillator. A SINGLE SCHMITT TRIGGER MAKES AN OSCILLATOR The figure illustrates an oscillator made from a single Schmitt trigger. Since the MM74C14 is a hex Schmitt trigger, this oscillator consumes only one sixth of a package. The remaining 5 gates can be used either as ordinary inverters like the MM74C04 or their Schmitt trigger characteristics can be used to advantage in the normal manner. Assuming these five inverters can be used elsewhere in the system, Figure 6 must represent the ultimate in low gate count oscillators. 15 Invisible Broken Wire Detector Figure (1): Schmitt Trigger Oscillator Voltage V1 is depicted in Figure (2) and changes between the two thresholds of the Schmitt trigger. If these thresholds were constant percentages of VCC over the supply voltage range, the oscillator would be insensitive to variations in VCC. However, this is not the case. The thresholds of the Schmitt trigger vary enough to make the oscillator exhibit a good deal of sensitivity to VCC. Applications that do not require extreme stability or that have access to well regulated supplies should not be bothered by this sensitivity to VCC. Variations in threshold can be expected to run as high as four or five percent when VCC varies from 5V to 15V. Figure: Waveforms for Schmitt Trigger Oscillator A CMOS CRYSTAL OSCILLATOR Figure below illustrates a crystal oscillator that uses only one CMOS inverter as the active element. Any odd number of inverters may be used, but the total propagation delay through the ring limits the highest frequency that can be obtained. Obviously, the fewer inverters that are used, the higher the maximum possible frequency. 16 Invisible Broken Wire Detector Figure: A crystal Oscillator CONCLUSIONS A large number of oscillator applications can be implemented with the extremely simple, reliable, inexpensive and versatile CMOS oscillators described in this note. These oscillators consume very little power compared to most other approaches. Each of the oscillators requires less than one full package of CMOS inverters of the MM74C04 variety. Frequently such an oscillator can be built using leftover gates of the MM74C00, MM74C02, and MM74C10 variety. Stability superior to that easily attainable with TTL oscillators is readily attained, particularly at lower frequencies. These oscillators are so versatile, easy to build, and inexpensive that they should find their way into many diverse designs. AG13 or LR44 type button cells As a 3v Power supply is required for powering the whole circuit, AG13 or LR44 type battery cells can be used. LR44 is a standard type of 1.5 volt button cell alkaline battery, commonly used in small LED flashlights, digital thermometers and calipers, watches, clocks, and laser pointers. Alkaline batteries and alkaline cells (a battery being a collection of multiple cells) are a type of disposable battery or rechargeable battery dependent upon the reaction between zinc and manganese dioxide (Zn/MnO2). Compared with zinc-carbon batteries of the Leclanché or zinc chloride types, while all produce approximately 1.5 volts per cell, alkaline batteries have a higher energy density and longer shelf-life. Compared with silver-oxide batteries, which alkaline commonly compete against in button cells, they have lower energy density and shorter lifetimes but lower cost. The alkaline battery gets its name because it has an alkaline electrolyte of potassium hydroxide, instead of the acidic ammonium chloride or zinc chloride electrolyte of the zinc-carbon batteries which are offered in the same nominal voltages and physical size. Other battery systems also use alkaline electrolytes, but they use different active materials for the electrodes. 17 Invisible Broken Wire Detector The silver-oxide battery variant SR44 has the same outer dimensions and approximately the same nominal voltage as an LR44 cell, but higher energy density and a more stable voltage output over the battery's lifetime. Although LR44 and SR44 are two distinctly different batteries, in common usage they are usually considered the same battery with only a "quality" difference. R44 indicates a round (cylindrical) 11.4±0.2 mm diameter and 5.2±0.2 mm height as defined by the British/European standard BS EN 60086:1998, Primary batteries. The first and second letter of this battery code conforms to the alphanumeric coding system defined by the International Electro technical Commission (IEC) in its 60086-3 standard (Primary batteries, part 3 Watch batteries). The first letter indicates the electrochemical system used: L: (−) zinc electrode – alkali metal hydroxide electrolyte – manganese dioxide electrode (+) S: (−) zinc electrode – alkali metal hydroxide electrolyte – silver oxide electrode (+) The second letter R indicates a round (cylindrical) form. Characteristics Name: LR1154 (manganese dioxide, “alkaline”); SR1154 (silver-oxide); ANSI/NEDA name : 1166A (alkaline), 1107SO (silver-oxide), 1131SOP (silver-oxide); Other colloquial names: AG13, A76, 157 (alkaline), SG13, S76, 357 (silver-oxide); Typical capacity (mAh):150 (alkaline), 200 (silver-oxide); Nominal voltage : 1.50 (alkaline); 1.55 (silver-oxide); Shape: button; Terminal layout: + bottom/sides, - top; Dimensions (max): D 11.6 mm, H 5.4 mm; 18 Invisible Broken Wire Detector DIODES USED In electronics, a diode is a two-terminal electronic component that conducts electric current in only one direction. The term usually refers to a semiconductor diode, the most common type today. This is a crystalline block of semiconductor material connected to two electrical terminals. A vacuum tube diode (now little used except in some high-power technologies) is a vacuum tube with two electrodes; a plate and a cathode. The most common function of a diode is to allow an electric current to pass in one direction (called the diode's forward direction) while blocking current in the opposite direction (the reverse direction). Thus, the diode can be thought of as an electronic version of a check valve. This unidirectional behavior is called rectification, and is used to convert alternating current to direct current, and to extract modulation from radio signals in radio receivers. However, diodes can have more complicated behavior than this simple on-off action, due to their complex non-linear electrical characteristics, which can be tailored by varying the construction of their P-N junction. These are exploited in special purpose diodes that perform many different functions. For example, specialized diodes are used to regulate voltage (Zener diodes), to electronically tune radio and TV receivers (varactor diodes), to generate radio frequency oscillations (tunnel diodes), and to produce light (light emitting diodes). Diodes were the first semiconductor electronic devices. The discovery of crystals' rectifying abilities was made by German physicist Ferdinand Braun in 1874. The first semiconductor diodes, called cat's whisker diodes were made of crystals of minerals such as galena. Today most diodes are made of silicon, but other semiconductors such as germanium are sometimes used. 1N4148 High Speed switching diodes The 1N4148 and 1N4448 are high-speed switching diodes fabricated in planar technology, and encapsulated in hermetically sealed leaded glass SOD27 (DO-35) packages. 19 Invisible Broken Wire Detector FEATURES •Hermetically sealed leaded glass SOD27 (DO-35) package •High switching speed: max. 4 ns •General application •Continuous reverse voltage: max. 100 V •Repetitive peak reverse voltage: max. 100 V •Repetitive peak forward current: max. 450 mA. APPLICATIONS •High-speed switching. TRANSISTOR USED: What is Transistor in general? A transistor is a semiconductor device used to amplify and switch electronic signals. It is made of a solid piece of semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be much more than the controlling (input) power, the transistor provides amplification of a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits. The transistor is the fundamental building block of modern electronic devices, and its presence is ubiquitous in modern electronic systems. Following its release in the early 1950s the transistor revolutionized the field of electronics, and paved the way for smaller and cheaper radios, calculators, and computers, amongst other things. Importance The transistor is the key active component in practically all modern electronics, and is considered by many to be one of the greatest inventions of the twentieth 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. Although several companies each produce over a billion individually packaged (known  as discrete) transistors every year, the vast majority of transistors now produced are 20 Invisible Broken Wire Detector in integrated circuits (often shortened to IC, microchips or simply chips), along with diodes, resistors, capacitors and other electronic components, to produce complete electronic circuits. A logic gate consists of up to about twenty transistors whereas an advanced microprocessor, as of 2009, can use as many as 2.3 billion transistors (MOSFETs). "About 60 million transistors were built this year  ... for [each] man, woman, and child on Earth." 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 and write a computer program to carry out a control function than to design an equivalent mechanical control function. Usage The bipolar junction transistor, or BJT, was the most commonly used transistor in the 1960s and 70s. Even after MOSFETs became widely available, the BJT remained the transistor of choice for many analog circuits such as simple amplifiers because of their greater linearity and ease of manufacture. Desirable properties of MOSFETs, such as their utility in low-power devices, usually in the CMOS configuration, allowed them to capture nearly all market share for digital circuits; more recently MOSFETs have captured most analog and power applications as well, including modern clocked analog circuits, voltage regulators, amplifiers, power transmitters, motor drivers, etc. Simplified Operation The essential usefulness of a transistor comes from its ability to use a small signal applied between one pair of its terminals to control a much larger signal at another pair of terminals. This property is called gain. A transistor can control its output in proportion to the input signal, that is, can act as an amplifier. Alternatively, the transistor can be used to turn current on or off in a circuit as an electrically controlled switch, where the amount of current is determined by other circuit elements. The two types of transistors have slight differences in how they are used in a circuit. A bipolar transistor has terminals labeled base, collector, and emitter. A small current at the base terminal (that is, flowing from the base to the emitter) can control or switch a much larger current between the collector and emitter terminals. For a field-effect transistor, the terminals are labeled gate, source, and drain, and a voltage at the gate can control a current between source and drain. The image to the right represents a typical bipolar transistor in a circuit. Charge will flow between emitter and collector terminals depending on the current in the base. Since internally the base and emitter connections behave like a semiconductor diode, a voltage drop develops between base and emitter while the base current exists. The amount of this voltage depends on the material the transistor is made from, and is referred to as VBE. 21 Invisible Broken Wire Detector Description of the BC547 transistor The transistor is a component with 3 electric wires coming out of it. They are named B (base), C (collector), and E (emitter). The drawing of BC547 transistor is as under: 22 Invisible Broken Wire Detector How it is used If one connects a tension source between the wires C and E, the transistor will not let any current trough (fig. 1). But between B and E there is a shortcut. If one wants to make a given current go trough B and E, one must use a tension source and a resistor (fig. 2). If one sends a current of IB amperes between B and E, then the resistor will allow a current of IC = ß . IB amperes pass between C et E (fig. 3). In this case, ß is about 100. 23 Invisible Broken Wire Detector Resistors Used A resistor is a two-terminal electronic component that produces a voltage across its terminals that is proportional to the electric current passing through it in accordance with Ohm's law: V = IR Resistors are elements of electrical networks and electronic circuits and are ubiquitous in most electronic equipment. Practical resistors can be made of various compounds and films, as well as resistance wire (wire made of a high-resistivity alloy, such as nickel/chrome). The primary characteristics of a resistor are the resistance, the tolerance, maximum working voltage and the power rating. Other characteristics include temperature coefficient, noise, and inductance. Less well-known is critical resistance, the value below which power dissipation limits the maximum permitted current flow, and above which the limit is applied voltage. Critical resistance is determined by the design, materials and dimensions of the resistor. Resistors can be integrated into hybrid and printed circuits, as well as integrated circuits. Size, and position of leads (or terminals) are relevant to equipment designers; resistors must be physically large enough not to overheat when dissipating their power. Units The ohm (symbol: Ω) is the SI unit of electrical resistance, named after Georg Simon Ohm. Commonly used multiples and submultiples in electrical and electronic usage are the milliohm −3 3 6 (1x10 ), kilo ohm (1x10 ), and mega ohm (1x10 ). Power Dissipation The power dissipated by a resistor (or the equivalent resistance of a resistor network) is calculated using the following: All three equations are equivalent. The first is derived from Joule's first law. Ohm‟s Law derives the other two from that. The total amount of heat energy released is the integral of the power over time: If the average power dissipated is more than the resistor can safely dissipate, the resistor may depart from its nominal resistance and may become damaged by overheating. 24 Invisible Broken Wire Detector Excessive power dissipation may raise the temperature of the resistor to a point where it burns out, which could cause a fire in adjacent components and materials. There are flameproof resistors that fail (open circuit) before they overheat dangerously. Note that the nominal power rating of a resistor is not the same as the power that it can safely dissipate in practical use. Air circulation and proximity to a circuit board, ambient temperature, and other factors can reduce acceptable dissipation significantly. Rated power dissipation may be given for an ambient temperature of 25 °C in free air. Inside an equipment case at 60 °C, rated dissipation will be significantly less; a resistor dissipating a bit less than the maximum figure given by the manufacturer may still be outside the safe operating area and may prematurely fail. Color Codes of resistors The 4-band code is used for marking low precision resistors with 5%, 10% and 20% tolerances. Identifying the value will become easy with a little practice, as there are only a few simple rules to remember: The first two bands represent the most significant digits of the resistance value. Colours are assigned to all the numbers between 0 and 9, and the colour bands basically translate the numbers into a visible code. Black is 0, brown is 1, red is 2 and so on (see the colour code table below). So, for example, if a resistor has brown and red as the first two bands, the most significant digits will be 1 and 2 (12). The third band indicates the multiplier telling you the power of ten to which the two significant digits must be multiplied (or how many zeros to add), using the same assigned value for each colour as in the previous step. For example, if this band is red (2), you will 2 multiply it by 10 = 100 (or add 2 zeros). So, for the resistor we used in the previous example, the value would be: 12 x 100 = 1200Ω (1.2kΩ). Note: If the multiplier band is gold or silver, the decimal point is moved to the left by one or two places (divided by 10 or 100). The tolerance band (the deviation from the specified value) is next, usually spaced away from the others, or it's a little bit wider. A colour is assigned to each tolerance: gold is 5%, silver is 10%. 20% resistors have only 3 colour bands - the tolerance band is missing. So, for a 560 ohm, 5% resistor the color stripes will be green, blue, brown and gold. 1 Green and blue are the first significant digits (56); brown is the multiplier (10 = 10) and gold is the tolerance (5%). 56 x 10 = 560Ω. 2 If the 3rd band would be red instead of brown, the multiplier would be (10 = 100) instead of 10 and the resistor value would be 56 x 100 = 5600 ohms = 5.6 k ohms. 25 Invisible Broken Wire Detector If the multiplier band is gold or silver, then the decimal point is moved to the left one or two places (divided by 10 or 100). For example, a resistor with green, blue, silver and gold rings has a value of 56 x 0.01 = 0.56Ω. The 5-band code The 5 band code is used for marking high quality, precision resistors with 2%, 1% or lower tolerances. The rules are similar to the previous system; the only difference is the number of digit bands. The first 3 bands will represent the value, the 4th band will be the multiplier and the 5th stripe will give us the tolerance. Optional band A few resistors have an additional band - often giving beginners a bit of trouble - indicating either the reliability or the temperature coefficient. The reliability band specifies the failure rate per 1000 hours (assuming that a full wattage being applied to the resistor). This stripe is found primarily on 4-band resistors made for military applications and seldom used in commercial electronics. The temperature coefficient is more commonly marked, especially on quality 5-band resistors, as it starts to become an important factor for precision components. For a resistor with temperature coefficient of 200 ppm, for example, a change in temperature of 50°C causes a value change of 1%. The most common values for this band are presented in the color chart above. 26 Invisible Broken Wire Detector The standard resistor colour code table: First-band Second-band Third-band Fourth-band Colour Digit Digit Multiplier Tolerance 0 Black 0 0 10 = 1 1 Brown 1 1 10 = 10 1% 2 Red 2 2 10 = 100 2% 3 Orange 3 3 10 = 1000 3% 4 Yellow 4 4 10 = 10000 4% 5 Green 5 5 10 = 100000 6 Blue 6 6 10 = 1000000 7 Violet 7 7 10 = 10000000 8 Gray 8 8 10 = 100000000 9 White 9 9 10 = 1000000000 Gold 5% Silver 10% None 20% Types of resistors used in the Circuit 1. 47 ohm Resistor The 47 ohm resistor has yellow, violet and black bands across it. The value is calculated as under: Yellow = 4 Violet = 7 0 Black = 10 = 1 0 So, the value of resistor = 47 x 10 = 47Ω 2. 1M ohm Resistor The 1M ohm resistor has Brown, Black and Green bands across it. The value is calculated as under: Brown = 1 Black = 0 5 Green = 10 5 So, the value of resistor = 10 x 10 = 1MΩ 3. 560 ohm Resistor The 560 ohm resistor has Green, Blue, Brown bands across it. The value is calculated as under: Green = 5 Blue = 6 27 Invisible Broken Wire Detector 1 Brown = 10 So, the value of resistor = 56 x 10 = 560Ω 4. 220 ohm Resistor The 220 ohm resistor has Red, Red, Brown bands across it. The value is calculated as under: Red = 2 Red = 2 1 Brown = 10 So, the value of resistor = 22 x 10 = 220Ω Light Emitting Diode A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps in many devices, and are increasingly used for lighting. Introduced as a practical electronic component in 1962, early LEDs emitted low-intensity red light, but modern versions are available across the visible, ultraviolet and infrared wavelengths, with very high brightness. The LED is based on the semiconductor diode. When a diode is forward biased (switched on), electrons are able to recombine with holes within the device, releasing energy in the form of photons. This effect is called electroluminescence and the color of the light (corresponding to the energy of the photon) is determined by the energy gap of the semiconductor. An LED is 2 usually small in area (less than 1 mm ), and integrated optical components are used to shape its radiation pattern and assist in reflection. LEDs present many advantages over incandescent light sources including lower energy consumption, longer lifetime, improved robustness, smaller 28 Invisible Broken Wire Detector size, faster switching, and greater durability and reliability. However, they are relatively expensive and require more precise current and heat management than traditional light sources. Current LED products for general lighting are more expensive to buy than fluorescent lamp sources of comparable output. They also enjoy use in applications as diverse as replacements for traditional light sources in aviation lighting, automotive lighting (particularly indicators) and in traffic signals. The compact size of LEDs has allowed new text and video displays and sensors to be developed, while their high switching rates are useful in advanced communications technology. Infrared LEDs are also used in the remote control units of many commercial products including televisions, DVD players, and other domestic appliances. 29 Invisible Broken Wire Detector RESULTS AND DISCUSSIONS During the course of the practical training project, there were many practical problems were encountered where many difficulties were faced by the group in getting the proper output sometimes due to loosely placed components and improper orientations of components on the PCB board etc. The proper orientation of all the components such as the notch of the IC, the polarity of the diodes, and direction of resistances and capacitors and other components has to be taken care of during mounting of components on the board before soldering is done. Any mistake committed in doing so can result in improper functioning of the circuit. The modifications were done as and when required, to make the circuit more accurate and neat. Thus the circuit was made successfully which can easily detect broken point in the wire inside the PVC jacket without physically disturbing it. The whole circuit can be accommodated in a small PVC pipe and used as a handy broken-wire detector. This will make the circuit more compact and easy to handle. The handy bro0ken-wire detector can be taken anywhere and everywhere and becomes less prone to damage. (Picture of original circuit to be scanned and placed here) 30 Invisible Broken Wire Detector Conclusions and Recommendations Thus using just an hex inverter and few resistors we are able to construct a device which can easily detect a faulty broken wire and thus save the extra cost of an user which is incurred on replacing the faulty wire and not repairing it which is otherwise too difficult. Future Scope: We can use an inverter in between the LED and the oscillator which will then turn on the LED only when the broken point is detected and keeping it off when the wire is not broken. By making this change we can make our detector more user friendly which now directly shows the broken point. References Electronics for you magazine www.educypedia.be/electronics references of CMOS 4069 IC Simple, low cost electronics projects by Fred Blechmann(Page 66) Electrical technology by B.L.Theraja Baker, R. Jacob (2008). CMOS: Circuit Design, Layout, and Simulation, Revised Second Edition. Reference of transistor 547 Electronic devices and circuits: principles and applications Deshpande Page 330 Journal of electronic engineering Electronic Devices And Circuit Theory, Robert Boylestad and Louis Nashelsky,Eight Edition www.fairchildsemi.com - Application note 118 31
"CMOS Pulse Oscillators"