Download mobile charger - Kaushik Science Projects

PROJECT REPORT
ON
MOBILE CHARGER
IN PARTIAL FULFILMENT OF THE
REQUIREMENT FOR THE
DIPLOMA IN ELECTRONICS AND COMMUNICATION ENGG.
(Session 2010-2013)
SUBMITTED BY :
NAME
ROLL. NO.
NARENDER
(21/10)
RAVI NATH
(33/10)
RINKU VERMA
(80/05)
UNDER THE GUIDENCE OF:
SH. VINOD KUMAR
E.C.E. DEPARTMENT
SH. PARVINDER SINGH
HEAD OF THE DEPARTMENT
DEPARTMENT OF ELECTRONICS AND
COMMUNICATION ENGG.
GOVERNMENT POLYTECHNIC SONIPAT
SONIPAT-131001
CERTIFICATE
It is to be certified that this project made by Narender, Ravi nath, and rinku verma on
MOBILE CHARGER during year 2012 under the keen guidance of sh. Vinod munjal
submitted in partial fulfillment of requirenment for award of diploma in E.C.E.
Principal
Sh. BIHARI LAL
Guided By
Sh. Vinod Munjal
Head of the Department
Sh. Parvinder Singh
ACKNOWLEDGEMENT
This Ploytechnic has in its alumni distinguished personalities and indebeted to many
individuals for their contribution of materials and assistance during the project work.
I am greatly thankful to my guide Sh. Vinod Munjal, Department of Electronics and
Communication, who took pains to see that I come out successfully in doing this project.
He give whole hearted guidance and cooperation. Thus he played an important role in
completion of this project.
Finally I express my deep debts to my beloved parents and all the people who help me
directly or indirectly to complete this project successfully.
Narender
ravi nath
rinku verma
INDEX
1. Introduction
2. Block Diagram Description
3. Circuit Diagram Description
4. List of Parts
5. Component Detail
6. PCB Preparation
7. Soldering Techniques
8. Assembling and Testing
9. Cabinet Designing
10. Bibilography
INTRODUCTION
Cell phone charging is a problem when you are away from home or where main source is
not available. A fully charged phone may last its battery up to 3 to 8 hours depending
how it is used. When you are out for picnics, camping, and or having adventure with your
cell phone battery empty, you cannot receive calls, take pictures or listen to music, thus a
simple and portable mobile charger is a need.
A good charger has an output of 4V DC to 8V DC and a current capacity of 100mA up to
500mA.With this charger capacity, standard 3.7V at 850mA battery can be charged up to
2 hours to 4 hours.
In this project, the charger can deliver a current up to 240mA which can fully charge a
cell phone in about 3.5 hours. For the charger to be portable and handy, the electronic
parts are minimal and powered only by a single 9V battery with only 3 to 5 cheap parts.
BLOCK DIAGRAM DESCRIPTION
Sensing process: In this process LDR is used as a sensor. When
any vehicle crosses the first laser light beam, LDR1 will trigger
IC1. The output of goes high for the time set to cross 10 meter with
the selected speed and LED1 glows during for period.
When the vehicle crosses the second laser light beam, the output of
IC2 goes high and LED2 glows for this period.
Counter: In this after sensing, the counter starts counting
when the first laser beam is intercepted and stops when the
second laser beam is intercepted. The time taken by the
vehicle to cross both the laser beam is displayed on the 7segment display.
A/D Converter: In analog to digital (A/D) converter, converts an analog input voltage
into an equivalent digital form because the outputs of most of the transducers are analog
signals. Therefore A/D converters are all the more essential, if information about the
physical phenomena is to be processed, stored and displayed as digital data. The data in
the digital form can be easily processed, stored recorded and displayed. Therefore A/D
converters find applications in digital processing equipments, instrumentation and
process control, computers, communication etc.
Digital Display Device: These devices are used in the final stage of any measurement for
presentation of the output. And also these devices are used for indicating the output.
These devices indicate the value of measure and in the form of decimal number. These
are cheap and simple. The power requirement is considerably smaller, since the output of
digital device is in digital form and therefore the output may be directly fed into memory
devices like floppy discs, tape recorders etc for future computations.
CIRCUIT DIGRAM DESCRIPTION
It has been designed assuming that the maximum permissible speed for highways is
either 40 kmph or 60 kmph as per the traffic rule. The circuit is built around five NE555
timer IC’s (IC1 through IC5), four CD4026 counter IC’s (IC6 through IC9) and four 7segment displays (DIS1 through DIS4). IC1 through IC3 functions as monostables, with
IC1 serving as count-start mono, IC2 as count as mono and IC3 as speed detector mono,
controlled by IC1 and IC2 outputs. Bistable set-reset IC4 is also controlled by the outputs
of IC1and IC2 and it (IC4), in turn, controls switching on/off of the 100 Hz astable
timersIC5. The time period of timer NE555 (IC1) count-start monostable multiviberator
is adjusted using preset VR1 or VR2 and capacitor C1. For 40 kmph limit the time period
is set for 9 seconds using preset VR1, while for 60 kmph limit the time period is set for 6
seconds using preset VR2. Slide switch S1 is used to be select the time period as per the
speed limit (40 kmph and 60 kmph respectively). The junction of LDR1 and resistor R1
is coupled to pin to of IC1. Normally, light from the laser keeps falling on the LDR
sensor continuously and thus the LDR offers a lower resistance and pin2 of IC1 is high.
Whenever light falling on the LDR is interrupted by any vehicle, the LDR resistance goes
high and hence pin2 of IC1 goes low to trigger the monostable. As a result, output pin3
goes high for the preset period (9 or 6 seconds) and LED1 glows to indicate it. Reset pin4
is controlled by the output of NANO gate N3 at power on or whenever reset switch S2 is
pushed.
For IC12, the monostable is triggered in the same way as IC1, when the vehicle intersects
the laser beam incident on LDR2 to generate a small pulse for stopping the count and for
used in speed detection. LED2 glows for the duration for which pin3 of IC2 are fed to
input pins2 and 1 of NAND gate N1, respectively. When the outputs of IC1 and IC2 go
high simultaneously (meaning that the vehicle has crossed the preset speed limit), output
pin3 of gate N1 goes low to trigger monostable timer IC3.
The output of IC3 is used for driving piezobuzzer PZ1, which alerts the operator of speed
limit violation. Resistor Rq and capacitor C5 decide the time period for which the
piezobuzzer sounds. The output of IC1 triggers the bistable (IC4) through gate N2 at the
leading edge of the count start pulse. When pin2 of IC4 goes low, the high output at its
pin3 enables astable clock generator IC5. Since the count stop pulse output of IC2 is
connected to pin6 of IC4 via diode D1, it reset the clock generatorIC5. IC5 can also be
reset via diode D2 at power on as when as reset switch S2 is pressed.
IC5 is configured as an astable viberator whose time period is decided by preset VR3,
resistor R12 and capacitor C10, using preset VR1, the frequency of the astable
multiviberator is set as 100Hz. The output of IC5 is fed to clock pin1 of decode
counter/7-segment decoder IC6 CD4026. The counter advances by one count at the
positive clock signal transition. The carryout signal from CD4026 provides one clock
after every ten clock inputs to clock the succeeding decade counter in a multidecade
counting chain. This is achieved by connecting pin5 of each CD4026 to pin1 of the next
CD4026. A high reset signal clears the decade counter to its zero count. Pressing switch
S2 provides a reset signal to pin15 of all CD4026 IC5 and also IC1 and IC14, capacitor
C12 and resistor R14 generate the power on reset signal. The seven decoded output ‘a’
through ‘g’ of CD4026 illuminate the proper segment of the 7- segment display (DIS1
through DIS4) used for representing the decimal digits ‘o’ through ‘9’. Resistors R16
through R19 limit the current across DIS1 through DIS4, respectively.
WORKING
When any vehicle crosses the first laser light beam, LDR1 will trigger IC1. The output of
IC1 goes high for the time set to cross 10m with the selected speed (40 kmph) and LED1
glows during for period.
When the vehicle crosses the second laser beam light, the output of IC2 goes high and
LED2 glows for this period. Piezobuzzer PZ1 sounds an alarm if the vehicle crosses the
distance between the laser setups at more than the selected speed (lesser period than
present period). The counter starts counting when the first laser beam is intercepted and
stops when the second laser beam is intercepted. The time taken by laser beam is
displayed on the 7-segment display.
LIST OF PARTS
Resistors: R1, R4, R2, R5, R6, R8, R10  100K
R11, R14, R3, R7, R13  10K
R16 – R19  470K
R9  470K
R12, R15  1K
VR1, VR2  100K
VR3  20K
Capacitors: C1, C2, C4, C6  100F, 25V electrolytic
C8, C11  0.01F ceramic disk
C3, C13, C15  0.1F ceramic disk
C5  10F, 25V electrolytic
C7  0.47F, 25V electrolytic
C9  0.2F, ceramic disk
C10  1F, electrolytic
C12  47F, electrolytic
C14  1000F, electrolytic
Semiconductors: IC1 – IC5  NE555 timer
IC6 – IC9  CD4026 decade counter/ 7- segment decoder
IC10  CD4011 NAND gate
IC11  7812 12V regulator
D1, D2, D7  1N4148 switching diode
D3, D6  iN4007 rectifier diode
LED1  green LED
LED2, LED3  red LED
DIS1 – DIS4  LTS543 common cathode, 7- segment display
Miscellaneous: PZ1  piezobuzzer
LDR1, LDR2  LDR
S1  ON/OFF switch (SPDT)
S2  push-to-on switch
S3  ON/OFF toggle switch
COMPONENTS DETAIL
CAPACITOR: The capacitor has been derived from the word capacity to store the
charge electrons. A number of different types of capacitor have been developed since
then using different types of dielectric material such as vacuum, plastic, glass, ceramic,
mica aluminum oxide etc.
ELECTROLYTIC CAPACITOR
These capacitors are made in the same way as electrolytic capacitors. Tantalium foil are
used in place of aluminium foils. These capacitors offers higher capacitance density
because of higher dielectric constant of tantalium oxide. These capacitors can be used at
higher temperature (200C) because of higher boiling point of the eletrolyte
CERAMIC CAPACITOR
These capacitors use ceramic as dielectric material. These capacitors can be divide into
two classes:1. Low loss low permitivity type
2. High permitivity type
Low loss permitivity type: The low types are usually made from steatite, which is
naturally occurring substance. It is finely ground, compressed and heated to 900C to
remove impurities. It is then reground and reformed at about 1300C. A thin plate or film
is metallised on both sides and leads are soldered to the metallised layers. These
capacitors are made in disc, tubular and rectangular form. The body is then given several
coats of insulating lacquer. These capacitors have low temperature co-efficient
(30ppm/C) and are used in temperature compensating applications by passing.
High permitivity type: These capacitors employ high permitivity ceramic material as
dielectric. The material used is barium ditanate (BaTiO3). These are manufactured in
same way. These capacitors have relatively large capacitance in small volume. These
capacitors are used for general purpose coupling and decoupling where wide variation in
capacitance value due to temperature, frequency, voltage and time can be tolerated.
RESISTORS
A resistor is a passive component. It introduces opposition to flow of current in a circuit.
Resistor are used in electronic circuit for setting base, voltage division, controlling gain,
fixing time constant, matching and loading circuit, heat generation and related
application.
CARBON COMPOSITION RESISTOR
The carbon composition consisting of finally ground carbon, resin binder and insulating
filter is made. The resulting mixture is compressed into shape of resistance and then fired
by metal sparing the end soldering tinned copper wire around it or moulding the lead
directly.
Typical specification: Voltage coefficient + 0.02 – 0.1% / V
Temp. coefficient + 0.05 – 0.25% / C
Self stability + 2% / yr.
VARIABLE RESISTORS
Variable resistors permit adjustment of resistance value between zero to maximum. These
essentially consist of a track of some kind of resistive material to which movable wiper
makes contact. These resistors can be classified on the basis of material used and
application. On the basis of application they are known as general purpose and precision
type. But on the basis of resistive material they are classified as:1. Carbon composition variable resistor
2. Wire wound variable
3. Cermet type variable resistor
CARBON COMPOSITION VARIABLE RESISTOR
Low power carbon variable resistors are manufactured from carbon composition either in
solid track type or a coating of carbon film. Both of these consist of an annular ring of
substrate material (ceramic or plastic). A resistive carbon layer is grown over it. The
movable contact slides over it.
Typical specifications:- Low (resistance) – Linear
Value - 100 to 10M
Tolerance - 20%
Temperature coefficient:- 1000ppm/C
Stability - 20%
Life expected – 20,000 rotations.
DIODE
The characteristics of N-type and P-type semiconductors have also been dealt separately
but as such P-type and N-type material taken separately are of every limited use. If we
join a piece of P-type material to a piece of N-type material such that the crystal structure
remains continues at the boundary, a P-N junction is formed. Such a P-N junction makes
a very useful device and is called a semiconductor diode.
Different types of diode:1. Tunnel diode
2. Zener diode
3. Schottky diode
4. Varacter diode
5. Photo diode
6. Light emitting diode (LED)
7. Power diodes
SPECIFICATION OF DIODE
The main specifications of diodes are:1.
2.
3.
4.
5.
6.
7.
Construction (material)
Peak inverse voltage (V)
Maximum forward current (mA)
Maximum reverse current (A)
Junction capacitance (pF)
Power rating
Case outline
Construction: This refers to which material has been used for manufacture of diode.
Peak inverse voltage: This is the maximum voltage that diode can with stand when
reverse biased.
Maximum forward current: This is maximum forward current that diode can carry
without appreciable damage to the diode.
Maximum reverse current: This is the current that flows during reverse bias condition.
It should be possible minimum. It is in  amperes.
Junction capacitance: Due to presence of junction, diode offers capacitance. It is in pF.
Power rating: It refers to maximum power that can be dissipated by diode safely.
Case outline: It refers to the case/ packaging style of the diode.
LIGHT EMMITINDG DIODE
It is an P-N junction which when forward biased, emits light. Charge carrier
recombinations occur at the junction as the electrons cross from N side and recombine
with holes on P side. When these recombinations take place, charge carriers give up
energy in the form of light and heat. If the semiconducting material used is translucent,
the light is emitted and the junction acts as source of light.
Semiconducting material used for manufacture of LED is gallium, phosphide which emits
red or yellow light and gallium arsenide which gives green or red light emission.
ADVANTAGES OF LED:
1.
2.
3.
4.
5.
6.
Low working voltage and current
Less power consumption
No warm up time
Very fast switching
Small size and weight
Long life
Application of LED:
1. LED’s are extensively used as display device. Several LED’s are added in series
to form segmental and dot matrix displays.
2. These are used in optical communication systems.
Specifications of LED:
1.
2.
3.
4.
5.
6.
7.
Color
Wavelength at peak emission
Forward voltage
Forward current
Power dissipation
Luminous intensity
Maximum reverse current
INTEGRATED CIRCUIT
The integrated circuit is nothing but a very small single crystal chip of silicon in which
many discrate components along with some of their interconnections are fabricated and
as such these different components along with their interconnections became an integral
part of the small crystal chip of silicon and hence called an “Integrated circuit”
NE 555 TIMER
The NE555 is a highly stable controller, capable of producing accurate timing pulses.
With monostable operation, the time delay is controlled by one external resistor and one
capacitor. With astable operation, the frequency and duty cycle are accurately controlled
with two external resistors and one capacitor. Supply voltage ranges from 4.5V to 16V
DC.
Features:
1. Direct replacement for SA 555/LM 555
2. High current drive capability (200mA)
3. Adjustable duty cycle
Applications:
1.
2.
3.
4.
Precision timing
Pulse generator
Time delay generator
Sequential timing
CD4011 – NAND GATE
It is a quad 2- input NAND gate, monolithic complement MOS (CMOS) integrated
circuit constructed with P- channel enhancement mode transistors. The device has
buffered outputs, which improve transfer characterstics by providing very high gain. All
inputs are protected against static discharge with diodes to VDD and VSS. Voltage
operating range (VDD) is from 3V DC to 15V DC.
CD4026 DECADE COUNTER/7-SEGMENT DECODER
It consists of 5- stage Johnson counter and output decoder which converts the Johnson
code into a 7-segment decoded output for driving the display. The advantage of this IC is
that it can be used as counter as well as 7-segment display decoder voltage operating
range (VDD) is from 3V DC to 18V DC.
PIEZOBUZZER
Piezobuzzer PZ1, which alerts the operator of speed-limit violation. Piezobuzzer sounds
an alarm if the vehicle crosses the distance between the laser setups at more than the
selected speed (lesser period than preset period).
LASER
Laser stands for emission of radiation. This device is able to produce a beam of radiation
with usual properties. The laser beam is coherent i.e. the waves are in phase, it is
monochromatic i.e. the waves are of effectively the same wavelength, it is highly
directional and very-very intense.
Characteristics of laser beam:
1.
2.
3.
4.
It is highly unidirectional.
It is highly monochromatic.
It is intense beam of light.
It is coherent.
Use of laser:
1.
2.
3.
4.
5.
6.
Laser welding
Spot welding
Seam welding
Laser cutting
Laser drilling
Laser based alighnment
LDR
LDR stands for light dependent resistor. In this circuit there are two LDR’s used. And
this LDR are used as sensor when laser beam is falling on them. The system basically
comprises two laser transmitter – LDR sensor pairs, which are installed on the highway
10m apart, with the transmitter and the LDR sensor of each pair on the opposite sides of
the road whenever light falling on the LDR is interrupted by any vehicle.
BATTERY
In mobile application of the circuit, where 230V AC is not available. So we use an
external +12V battery is required to operate this circuit.
SWITCHES
A switch is defined as the device for making, breaking or changing connection sequence
in an electric circuit, switch thus essentially consists of a fixed part and a moving contact.
There are switches which have several contacts in one assembly.
PUSH - TO - ON SWITCH
These switches have an axial spring leading on the contact, which may be at the side or at
bottom. If it is at side, an insulating cam, when pushed, locks under pressure on to the
spring contact, pushing it against the fixed contact. These switches are available in
locking and non-locking types. Illuminated push button switches are available which
have provision for bulb, inside the housing contact ratings and life vary to a large extent
from one type of switch to another and from manufacturer to manufacturer.
Multiple push button switches have a common frame with interaction between switches
so that they perform interrelated functions that a single switch cannot perform.
ON/OFF TOGGLE SWITCH
This switch is mainly used for ON/OFF control of AC mains or DC power supplies.
These switches employ sliding contact system. The switch closure is accomplished by a
lever. Commercially available toggle switches can be locking or non-locking type. Two
and three position switches are available.
SPECIFICATION OF SWITCHES
The important electrical and mechanical specifications of switches are described here:Electrical specification:
1. Contact resistance: This is measured as the voltage drop from tail to tail of the
mated contacts with specified current flowing through the contact and is specified
in milli ohms.
2. Breakdown voltage: This is the voltage between open contacts of the switch at
which the insulation breakdown occurs. The breakdown voltage depends upon
contact spacing and geometry.
3. Insulation resistance: This is the resistance between contact and body of switch.
It depends upon the type of material used, geometry of the switch and
environmental conditions. It is measure of leakage current.
4. Contact current rating: This is the maximum amount of DC or r.m.s.a.c. current
that can pass continuously through the contacts. The contacts are closed for
specified temperature rise. Usually contact rating is specified at 25C and
maximum allowable temperature rise is 70C.
MANUFACTURING OF COMPONANTS
MANUFACTURING OF RESISTORS: The following steps are involved generally in the
manufacturing of resistors:1. Preparation of substrate or base:- The base or substrate used is an insulating
material, over which resistive element (coating or wire winding) is applied or
mounted. This also provides mechanical strength to the complete assembly.
2. Preparation of resistive element:- Metal alloys, carbon and graphite with binders
are resistive materials generally used. The resistance wire used has lower
temperature coefficient. The generally used resistance wires are Nickel, Copper,
Nickel Chromium and Nickel Chromium Almunium.
Resistive element may be in the form of film or slug conductive coating or films are
formed on to the base for making end connections.
3. End connections or terminal fitting:- terminals are used to make electrical
connections of the resistive element to the circuit. This is done by using wire
leads, metallic legs and metallic ferulles. The lead configuration is either radial or
axial. These terminals are either pressifitted, welded or soldered to end caps.
4. Protective coating:- The protective coating on resistance element provides
protection against mechanical and environmental forces. By choosing proper
coating material, the resistor can with stand higher temperatures. Cement mixed
with binder, vitreous, enamel or silicon are generally used as protective coating
material.
5. Identification marking:- Sorted resistors are color coded or marked for their
values, tolerance and other ratings. These are finally packed.
MANUFACTURING OF INTEGRATED CIRCUIT
Integrated circuits form a branch of the general field of microelectronics. The hybrid
circuits are those, which contain resistors and capacitors made by depositing thin film of
metal on a substrate together with discrete active devices. The functional devices are
generally electrical filters. The main technologies that are of interest to us are:1. Monolithic integrated circuits
2. (a) Thick film circuits
(b) Thin film circuits
Monolithic integrated circuits:- Monolithic means a resulting circuit is formed on
a single silicon chipor crystal. This technology which is also called “planner
circuit technology” has most widespread acceptance and consists of following
four basic layers:1. The first is P-type silicon layer and is 100m thick and this serves as a
substrate upon which the integrated circuit is to be built.
2. The second layer is of N-type material is only 20-25m thick.
3. The third layer is of silicon dioxide (SiO2)
4. The fourth layer is a metallic layer made of Aluminium and is added to
supply the required interconnections b/w different fabricated components.
(a) Thick film circuits:- In thick film circuits the resistors and their
interconnections patterns are printed on a ceramic substrate by
silk screen or some other method. Thick films are about 25m
thick.
(b) Thin film circuits:- Thin film technique permits greater precision
and miniaturization and is generally preferred when space is of
important consideration. Thin film interconnection patterns and
resistors are vacuum deposited on a glass or ceramic substrate.
Thin films are typically 0.1m to 0.5m thick.
MANUFACTURING OF DIODES
Semiconductor diodes are normally of the following types:1. Grown junction:- Diodes of this type are formed during the czochralski crystal
pulling process. Impurities of p and n type can be alternately added to the molten
semiconductor material in the crucible, resulting in a p-n junction when the
crystal is pulled. After slicing, the large area device can then be cut into large
number of smaller area semiconductor diodes.
2. Alloy type:- The alloy process will result in a junction type. Semiconductor diode,
which will have a high current rating and large PIV rating. The junction
capacitance is also large due the large junction area. An alloy will result that,
when cooled, will produce a p-n junction at the boundary of the alloy and
substrate.
3. Diffusion type:- The diffusion process of forming semiconductor junction diodes
canemploy either solid or gaseous diffusion. The process requires more time than
the alloy process, but it is relatively inexpensive and can be very accurately
controlled. Diffusion is a process by which a heavy conc. of particles will diffuse
in to a surrounding region of lesser concentration.
4. Epitaxial growth:- Then + indicates a very high doping level for a reduced
resistance characteristic. It’s purpose is to act as a semiconductor extension of the
conductor and not the n-type material of the p-n junction.
5. Point contact type:- The point contact semiconductor diode is constructed by
processing a phosphorus bronze spring against an n-type substrate. Hence, the
point contact diode can be used in applications where very high frequencies are
encountered, such as in microwave mixtures and detectors.
FAILURES OF COMPONENTS
The failure rate and mode of a resistor depends upon its type, the method of manufacture,
the operating and environmental conditions and resistance value.
Any resistor has dissipated power during operation. High powers can be dissipated at low
ambient temp., but lower dissipation will give improved stability and lower values of
failure rate. Since most resistors are uniform in construction, the temperature rise caused
by the power being dissipated will be a maximum in the middle of resistor body. This is
known as hot spot temperature. As the resistor value drifts out of specification, a partial
and gradual failure rates. However failures do occur because, during the passage of time,
mechanical stress and vibration, heat, applied voltage and humidity all act to cause
chemical or other changes and lead to gradual deterioration. The most common failures in
resistors are open circuit or short circuit.
Variable resistor has a moving part and depends for its operation on a good contact
between the wiper and a resistance track is bound to have higher failure rate than fixed
type. Failure rate depends upon the manufacturing method. Partial failures, such as rise in
wiper contact resistance giving increased electrical noise, are common. This may be
caused by particles of dust and abrasive matter trapped between wiper and track.
Complete failures will be open circuit, either between track and the end connections or
the wiper to track. This can be caused by corrosion of metal parts by moisture, distortion
of plastic parts.
FAILURES IN CAPACITOR
Generally capacitors are reliable components which have low failure rates especially
when derated. Life can further be increased by operating the capacitor with in the rated
specifications. As all capacitors are metal foils or electrodes separated by a dielectric, the
possible failures are:1.
2.
3.
4.
Short circuit due to dielectric breakdown.
Open circuit due to failure of end connection.
Gradual fall in insulation resistance or increase in leakage current.
Rise in series resistance i.e. increase in dissipation factor.
Some of the causes of failure are:(a) Manufacturing defects:- Manufacturing defects can result from included
impurities which can cause corrosion of internal connections. Mechanical
damage to end connection of capacitor resulting in over heating and short
circuit.
(b) Misuse:- This type of failure of capacitor results when it is subjected to
stresses beyond its specifications. Poor assembly methods use can also
stress end connection and seals
(c) Environmental:- Environmental factors like shock and vibration,
temperature variation, pressure variation etc. can also lead to failure of a
given capacitor.
TESTING OF COMPONENTS
Testing of resistors: The following two types of tests can be conducted on resistors:
1. Simple verification of resistor operation for checking for opens and shorts using
ohmmeter. When making reading with an ohmmeter, care must be taken to have
firm electrical connection between meter leads and wire terminals of the resistor
under measurement. Sometimes it is necessary to scrap the lead of resistors.
Fingers must not touch resistor leads, otherwise reading given by meter will be
equivalent to resistance of operator body in parallel with resistor.
When fairly accurate measurement of the value of resistance is required, wheat stone
bridge arrange meant is shown in figure, when it is balanced
Ra/Rb = Rx/Rs
The detector indication is then minimum. This is because the voltage drop across Rb is
then the same as that of resistor Rs. The balance point does not depend upon supply
voltage and any sensitive indicator can be used.
At balance position, Ra and Rb have been adjusted for null position.
Ra/Rb = Rx/Rs
Thus
Rx = Rs.Ra/Rb
TESTING OF CAPACITOR
1. Capacitor checks using ohmmeter:- Three capacitor defects are detestable with
an ohmmeter. Short, open and partial short. If the capacitor is in a circuit, it must
be separated by disconnecting one lead. The shorted capacitor has a dielectric
breakdown. When this condition is there, the ohmmeter will this show a studyzero reading. All capacitors checks should be made on the highest resistance
range of the ohmmeter. Make all checks with current in both directions. Connect
the leads in a selected manner for one check, reverse the leads and check again.
This double check will prevent erreous indirections from partially charged
capacitors.
When a good capacitor is kept b/w the leads of an ohmmeter, the
needle will swing from zero to infinity as the capacitor charges. The speed of needle
movement will be determined by the size of the capacitor. After capacitor is charged the
reading will hold steadily on infinity.
2. Checking capacitor with a voltmeter:- Open, short and partial short of
capacitors can also be checked by using a voltmeter.
The out of circuit capacitor is placed across a direct voltage source and allowed time
for charging. The applied voltage should never exceed the working voltage source
and check the charged capacitor with a voltmeter.
A good capacitor or an open capacitor should show zero voltage. However, the initial
reading may show some value of voltage due to capacitor charge. If the voltage
indication remains, the capacitor is leaking.
TESTING OF DIODES
The condition of a semiconductor diode can be quickly determined by using an
ohmmeter such as is found on the standard volt ohmmeter. The internal battery
(often1.5V) of the ohmmeter section will either forward or reverse bias the diode
when applied.
If the positive lead is connected to the anode and negative lead to the cathode, the
diode is forward biased and the meter should indicate a low resistance. The Rx 1000
or Rx 10000 setting should be suitable for the measurement with the reverse polarity
the internal battery will reverse bias the diode and the resistance is very large. A small
reverse bias resistance reading indicates a short condition while a large forward
resistance will indicate an open situation.
Most digital multimeters (DMMs) have a built in diode check represented by a diode
symbol →/- as a range selection. A forward bias connection will give the cut in
voltage while back bias will indicate open circuit state.
PCB PREPARATION
The various step involved in fabrication of plate are:1.
2.
3.
4.
5.
6.
7.
Cleaning of plate
Designing
Painting
Etching
Washing
Drilling
Soldering
Cleaning of plate:- The start with the general purpose is washed with CCL or any other
suitable organic solvent so as to any oxide, grease or dirt.
Designing:- Making of PCB drawing is done by placement of components in same order
as in circuit diagram on a piece of graph. We have to in the location of hole, deciding of
the diameter of various optimum area that each component should occupy shape and
location of is land converting two or more component at a plate full space utilization and
prevention of over crowding of component etc. There is no. other way to assume at the
correct then by trail and error for a drawing the leads of component 1mm diameter holes
and for fixing of PCB 3mm diameter holes are recommended.
Painting:- One does well if he or she has a good hand in good drawing lines with a
brush concentrate in a PCB pattern and the drilling holes in plate. Join the holes with
lines according to pattern with the brush dipped in the each avoid to narrow or too wide
lines. Below dry the painting with your mouth. If in case there is any shorting of line or
not knifed respectively with a blade or a knife after has dried.
Etching:- For etching the plate, take any utensil of any anticrowing material and wash it
properly in it take water just enough to immerse the board and add 20-30gm. FeCl3
carefully without any polishing one may heat this solution. Polishing one may heat this
solution. For quicker result keep checking the tray in a slow motion.
Washing:- The print or the pattern is removed by scrubbing with a rag soached in sector
till the entire copper pattern. Now wash the PCB in water.
Drilling:- The drilling if the holes is in such manner so as to corresponding to the IC base
exactly in inserting the pin of the base.
Soldering:- Soldering is the process of joining. Two metal at a temperature below
melting point having melting point 450 degree Celsius binds the metal. Bx chemical and
physical process or chemically solder reacts with small part of each metal to be jointed or
soldered thus forming a new compound physically the liquid solder alloy then enter the
exposed prose of the metal.
Solder:- Most of the soldering in electronics is done by using tin lead alloy. The phase
diagram show the behavior of the mixture of the tin and lead as this is heated for different
ratio of two metals.
Fluxes:- The soldering process require that the surface should be totally clear to the joint
area. Flux is impeded in the solder Rosim core solder it is available in paste or in liquid
form.
SOLDERING TECHNIQUES
Soldering is a process used for joining metal parts. It is necessary to use molten metal
known as solder. The melting temperature of solder is below to that of the metal joined so
that its surface is only wetted without melting. During soldering, relative positioning of
the surfaces to be joined. Wetted of these surfaces with molten solder and colling time for
solidification are important.
Soft soldering implies that joining process occurs at temperature below 450◦C. soldering
is of various types. In mass soldering, a large number of joints are to be soldered
simultaneously. It has productivity and reliability of assembly.
Various stages in mass soldering are:1.
2.
3.
4.
5.
6.
Assembling the board
Flux application
Flux drying or preheating
soldering
cooling
Flux removal
ASSEMBLING AND TESTING
1. Clean off any dust and dirt from the PCB with paper towel soaked in thinner/
acetone (nail polish remover).
2. Trace the conductor lines and component markings on PCB and mount each
component correctly.
3. Check correct polarity of the power supply before connecting power to the circuit.
4. In the circuit, use long wires for connecting the two LDR, so that you can take
them out of the PCB and install on one side of the highway, 20m apart.
5. Install the tow laser transmitters (such as laser torches) on the other side of the
highway exactly opposite to the LDRS such that laser light falls directly on the
LDRS.
6. Reset the circuit by pressing switch S2, SQ the display shows ‘ooooo’ using
switch S1, select the speed limit (say, 40kmph) for the highway.
7. For 40kmph speed setting, with timer frequency set at 100Hz, if the display count
is less than ‘400’, it means that the vehicle has crossed the speed limit (and
simultaneously the buzzer sounds). Reset the circuit for monitoring the speed of
the next vehicle.
CABINET DESIGNING
The cabinet is used for many purposes in the electronic circuit s. there are various types
and sizes of the cabinets used in the electronics. It provides mechanical protection to
various section of a system.
1. A cabinet design for speed checker for highway is made of wooden box.
2. At the top of wooden box a plane transparent glass is attached with due to this
transparent glass we can easily observe the display device with our naked eyes.
3. A PCB with shouldering components is placed inside the wooden box. Cabinet.
4. There is three holes on the wooden box cabinet one is for buzzer sound and
another two is for wires using LDR to measure the speed of the vehicle.
BIBILOGRAPHY
1. Electronics for you
December 2005
2. Electronic components and materials byK.S. Jamwal
3. Electronic Components and materials byMadhuri A. Joshi