CMOS Pulse Oscillators by suchenfz

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									Invisible Broken Wire Detector

                Amity University
                 Uttar Pradesh

Amity School of Engineering and Technology

                    Practical Training Report

Guided By:                             Submitted by:

Invisible Broken Wire Detector

        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

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

Invisible Broken Wire Detector


   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

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.

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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.

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                     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

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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.



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

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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

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.

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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.


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):

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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.

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CMOS Pulse Oscillators
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.

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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.

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.

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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

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                             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.

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

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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.


                          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

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

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                        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

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.

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                                Figure: A crystal Oscillator

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.

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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

   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.

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;

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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.

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  •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.

•High-speed switching.

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.

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

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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 [2002] ... 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.

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.

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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:

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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.

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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

     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.

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.

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           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
     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.
             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.

             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.

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.

Invisible Broken Wire Detector

The standard resistor colour code table:

                         First-band         Second-band       Third-band    Fourth-band
                            Digit              Digit           Multiplier    Tolerance
      Black                   0                  0        10 = 1
     Brown                    1                  1        10 = 10               1%
       Red                    2                  2        10 = 100              2%
     Orange                   3                  3        10 = 1000             3%
     Yellow                   4                  4        10 = 10000            4%
     Green                    5                  5        10 = 100000
      Blue                    6                  6        10 = 1000000
      Violet                  7                  7        10 = 10000000
      Gray                    8                  8        10 = 100000000
      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
       Black = 10 = 1
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
       Green = 10
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

Invisible Broken Wire Detector

       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
        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
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

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.

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)

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.


       Electronics for you magazine


       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

     - Application note 118


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