Electronic Stethescope

7/27/2019 Electronic Stethescope

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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.
http://en.wikipedia.org/wiki/Complementary-symmetryhttp://en.wikipedia.org/wiki/Complementary-symmetryhttp://en.wikipedia.org/wiki/Complementary-symmetryhttp://en.wikipedia.org/wiki/Complementary-symmetryhttp://en.wikipedia.org/wiki/Microphonicshttp://en.wikipedia.org/wiki/Microphonicshttp://en.wikipedia.org/wiki/Microphonicshttp://en.wikipedia.org/wiki/Voltshttp://en.wikipedia.org/wiki/Voltshttp://en.wikipedia.org/wiki/Voltshttp://en.wikipedia.org/wiki/Silicon_carbidehttp://en.wikipedia.org/wiki/Silicon_carbidehttp://en.wikipedia.org/wiki/Silicon_carbidehttp://en.wikipedia.org/wiki/Televisionhttp://en.wikipedia.org/wiki/Televisionhttp://en.wikipedia.org/wiki/Televisionhttp://en.wikipedia.org/wiki/Electron_mobilityhttp://en.wikipedia.org/wiki/Electron_mobilityhttp://en.wikipedia.org/wiki/Electron_mobilityhttp://en.wikipedia.org/wiki/Electromagnetic_pulsehttp://en.wikipedia.org/wiki/Electromagnetic_pulsehttp://en.wikipedia.org/wiki/Electromagnetic_pulsehttp://en.wikipedia.org/wiki/Nuclear_explosionhttp://en.wikipedia.org/wiki/Nuclear_explosionhttp://en.wikipedia.org/wiki/Nuclear_explosionhttp://en.wikipedia.org/wiki/Nuclear_explosionhttp://en.wikipedia.org/wiki/Electromagnetic_pulsehttp://en.wikipedia.org/wiki/Electron_mobilityhttp://en.wikipedia.org/wiki/Televisionhttp://en.wikipedia.org/wiki/Silicon_carbidehttp://en.wikipedia.org/wiki/Voltshttp://en.wikipedia.org/wiki/Microphonicshttp://en.wikipedia.org/wiki/Complementary-symmetryhttp://en.wikipedia.org/wiki/Complementary-symmetry

Electronic Stethescope

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