electronic stethescope
TRANSCRIPT
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ELECTRONIC
STETHOSCOPE
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PRAKASAM ENGINEERING COLLEGE
KANDUKUR
(An ISO 9001:2000 certified)
(Approved by AICTE, Affiliated To JNTU KAKINADA)
Prakasam Dt-523105
ELECTRONICS AND COMMUNICATION ENGINEERING
CERTIFICATE
This is to certify that the Mini Project report entitled
ELECTRONIC STETHOSCOPE
Being submitted as a part of fulfilling III.B.Tech II Semester college requirements
By
1. K.V.SURESH (07F91A04B5)
2. SURESH- MANDAVA (07F91A04B6)
3. S.S.KALYAN (07F91A04B8)
4. VAMSI KRISHNA- BEZAVADA (07F91A04C0)
Signature of guide Head of the Department
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RESISTOR:
A resistor is a two-terminalelectronic componentthat produces avoltageacross its
terminals that is proportional to theelectric currentthrough it in accordance
withOhm's law:
V = IR
Resistors are elements ofelectrical networksand electronic
circuits and are ubiquitous in most electronic equipment. Practical resistors can be
made of various compounds and films, as well asresistance wire(wire made of a
high-resistively alloy, such as nickel-chrome).
Resistors restrict the flow of electric current, for example a resistor
is placed in series with a light-emitting diode (LED) to limit the current passing
through the LED.
The color coding is shown below..
Fig: the resistor shown in color codes
Black 0
Brown 1
Red 2
Orange 3
Yellow 4
Green 5
Blue 6
Violet 7
Grey 8
White 9
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Example:
Circuit symbol:
Resistor values are normally shown using colored bands.
Each colour represents a number as shown in the table.
Most resistors have 4 bands:
The first band gives the first digit. The second band gives the second digit. The third band indicates the number of zeros. The fourth band is used to shows the tolerance (precision) of the resistor
Resistors are used with transducers to make sensor subsystems.
Transducers are electronic components which convert energy from one form into
another, where one of the forms of energy is electrical. A light dependent resistor,
or LDR, is an example of an input transducer. Changes in the brightness of the
light shining onto the surface of the LDR result in changes in its resistance. As will
be explained later, an input transducer is most often connected along with a resistor
to to make a circuit called a potential divider. In this case, the output of the
potential divider will be a voltage signal which reflects changes in illumination.
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The primary characteristics of a resistor are theresistance,
thetolerance, the maximum working voltage and thepowerrating. Other
characteristics includetemperature coefficient,noise, andinductance. Less well-
known iscritical resistance, the value below which power dissipation limits the
maximum permitted current, and above which the limit is applied voltage. Critical
resistance is determined by the design, materials and dimensions of the resistor.
Fig: Resistors with color coding
Resistors can be integrated intohybridandprinted circuits, as
well asintegrated 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.
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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 fromJoule's first law.
Ohms 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. 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.
A resistor may have one or more fixed tapping points so that the resistance can be
changed by moving the connecting wires to different terminals. Some wirewound
power resistors have a tapping point that can slide along the resistance element,
allowing a larger or smaller part of the resistance to be used.
Where continuous adjustment of the resistance value during operation of
equipment is required, the sliding resistance tap can be connected to a knob
accessible to an operator. Such a device is called arheostatand has two terminals.
CAPACITOR:
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Capacitors store electric charge. They are used with resistors
intiming circuitsbecause it takes time for a capacitor to fill with charge. They are
used to smoothvarying DC supplies by acting as a reservoir of charge. They are
also used in filter circuits because capacitors easily pass AC (changing) signals but
they block DC (constant) signals.
Circuit symbol:
The capacitor is a reasonably general model for electric
fields within electric circuits. An ideal capacitor is wholly characterized by a
constant capacitance C, defined as the ratio of charge Q on each conductor to the
voltage V between them:[8]
Electrolytic capacitors are
polarized and they must be
connected the correct way
round, at least one of their leads
will be marked + or -. They are
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not damaged by heat when soldering.
fig: Electrolytic capacitors fig: Disk capacitors
A capacitor (formerly known as condenser) is a
passiveelectronic componentconsisting of a pair of conductors separated by
adielectric(insulator). When there is apotential difference(voltage) across the
conductors, a staticelectric fielddevelops in the dielectric that storesenergyand
produces a mechanical force between the conductors.
An ideal capacitor is characterized by a single constant value,
capacitance, measured infarads. This is the ratio of theelectric chargeon each
conductor to the potential difference between them.
There are many types of capacitor but they can be split into two
groups, polarized and unpolarised.
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Three prefixes (multipliers) are used, (micro), n (nano) and p (pico):
means 10-6 (millionth), so 1000000F = 1F n means 10-9 (thousand-millionth), so 1000nF = 1F p means 10
-12
(million-millionth), so 1000pF = 1nF
A basic capacitor is made up of twoconductorsseparated by an
insulator, or dielectric. The dielectric can be made of paper, plastic, mica, ceramic,
glass, a vacuum or nearly any other nonconductive material. Some capacitors are
called electrolytics, meaning that their dielectric is made up of a thin layer of oxide
formed on a aluminum or tantalum foilconductor
DIODE:
Diodes allow electricity to flow in only one direction. The arrow
of the circuit symbol shows the direction in which the current can flow. Diodes are
the electrical version of a valve and early diodes were actually called valves.
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Diodes operate in both forward and reverse voltages
Ordinary diodes can be split into two types: Signal diodes which pass small
currents of 100mA or less and Rectifier diodeswhich can pass large currents. In
addition there areLEDsandZenerdiodes.
Inelectronics, a diode is a two-terminalelectronic component that
conductselectric currentin only one direction. The term usually refers to
a semiconductor diode, the most common type today. This is a crystalline piece
ofsemiconductormaterial connected to two electrical terminals.[1]A vacuum tube
diode (now little used except in some high-power technologies) is avacuum
tubewith twoelectrodes: aplateand acathode.
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 acheck valve. This unidirectional
behavior is calledrectification, and is used to convertalternating currenttodirect
current, and to extractmodulationfrom radio signals in radio receivers.
There are two kinds ofsemiconductordiodes: aP-N
junctiondiode, which forms an electrical barrier at the interface betweenN-andP-typesemiconductorlayers, and a Schottky diode, whose barrier is formed between
metal andsemiconductorregions.
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Small signal diodes can be damaged by heat when soldering, but the risk is small
unless you are using a germanium diode (codes beginning OA...) in which case
you should use a heat sink clipped to the lead between the joint and the diode body.
A standard crocodile clip can be used as a heat sink.
TRANSISTORS:
A transistor is asemiconductordeviceused toamplifyand
switchelectronicsignals. 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)powercan be
much more than the controlling (input) power, the transistor
providesamplificationof a signal. Today, some transistors are packaged
individually, but many more are found embedded inintegrated circuits.
The transistor is the fundamental building block of modernelectronic devices, and
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 cheaperradios,calculators, andcomputers, amongst other things.
Transistor symbols:
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There are two types of standard transistors, NPN and PNP, with
different circuit symbols. The letters refer to the layers of semiconductor material
used to make the transistor. Most transistors used today are NPN because this is the
easiest type to make from silicon. If you are new to electronics it is best to start by
learning how to use NPN transistors.
ADarlington pairis two transistors connected together to give a very high current
gain.
The BC548 is general purpose silicon, NPN, bipolar junction transistor found
commonly in European electronic equipment. It is electrically similar to the North
American 2N3904 and Japanese 2SC1815 but has different lead assignments.
If the TO-92 package is held in front of one's face with the flat side facing toward
you and the leads downward, (see picture) the order of the leads, from left to right
is collector, base, emitter. Note that the pin assignment of the complementary PNP
device BC558 is exactly the same.
Fig: BC548 transistor fig:BC558 transistor
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Specifications:
The exact specs of a given device depend on the manufacturer. It
is important to check the datasheet for the exact device and brand you are dealing
with. Philips and Telefunken are two manufacturers of the BC548. Vcbo = 30
Volts, Ic = 100mA, Ptotal = 50 mW and ft = 300 MH
Thebipolar 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 theCMOSconfiguration, 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.
Advantages
The key advantages that have allowed transistors to replace their vacuum tube
predecessors in most applications are
Small size and minimal weight, allowing the development of miniaturizedelectronic devices.
Highly automated manufacturing processes, resulting in low per-unit cost. Lower possible operating voltages, making transistors suitable for small,
battery-powered applications.
No warm-up period for cathode heaters required after power application. Lower power dissipation and generally greater energy efficiency. Higher reliability and greater physical ruggedness.
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Extremely long life. Some transistorized devices have been in service for morethan 50 years.
Complementary devices available, facilitating the design ofcomplementary-symmetrycircuits, something not possible with vacuum tubes.
Insensitivity to mechanical shock and vibration, thus avoiding the problemofmicrophonicsin audio applications.
Limitations
Silicon transistors do not operate at voltages higher than about1,000volts(SiCdevices can be operated as high as 3,000 volts). In contrast,
electron tubes have been developed that can be operated at tens of thousands of
volts.
High power, high frequency operation, such as that used in over-the-airtelevision broadcasting, is better achieved in electron tubes due to
improvedelectron mobilityin a vacuum.
Silicon transistors are much more vulnerable than electron tubes toanelectromagnetic pulsegenerated by a high-altitudenuclear explosion.
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