Download 555 Timer Final Report

555 - IC TIMER TESTER
A Project Report
Submitted in Partial fulfillment for the award of Bachelor of Engineering in
ELECTRICAL AND ELECTRONICS
Submitted to
RAJIV GANDHI PRODYOGIKI VISHWAVIDYALAYA
BHOPAL (M.P)
MINOR PROJECT REPORT
Submitted By
APURV SHARMA
0103EX051009
VISHAL MODI
0103EX051059
VIVEK PODDAR
0103EX051060
Under the Supervision of
Asst.. Prof. Amol Barve
ELECTRICAL & ELECTRONICS ENGINEERING
LAKSHMI NARAIN COLLEGE OF TECHNOLOGY,
BHOPAL (M.P.)
SESSION – 2005-09
LAKSHMI NARAIN COLLEGE OF TECHNOLOGY,
BHOPAL
ELECTRICAL & ELECTRONICS ENGINEERING
CERTIFICATE
This is to certify that Apurv Sharma (0103EX051009), Vishal Modi
(0103EX051059) and Vivek Poddar (0103EX051060), have satisfactorily completed
the work embodied in this preliminary entitled “555 IC TIMER TESTER”. It is a
bonafide piece of work, carried o ut under our /my guidance in the Electrical &
Electronics Engineering, Lakshmi Narain College of Technology, Bhopal for the
partial fulfillment of the Bachelor of Engineering during the academic year 2008.
Project Guide
Asst. Prof. Manish Khemariya
Approved By
Dr. R.K Shrivastava
Head of Department
Forwarded by
Dr. Gulab Singh
Principal
Lakshmi Narain College of Technology,
Bhopal
Lakshmi Narain College of Technology, Bhopal
ELECTRICAL & ELECTRONICS ENGINEERING
DECLARATION
Apurv Sharma (0103EX051009), Vishal Modi (0103EX051059) and Vivek Poddar
(0103EX051060), students of Bachelor of Engineering Electrical & Electronics
Engineering, Lakshmi Narain College of Technology, Bhopal. We hereby declare
that the work presented in this Minor Project is outcome of my own work, is
bonafide, correct to the best of my knowledge and this work has been carried out
taking care of Engineering Ethics. This work does not infringe any patented work
and had not been submitted to any University for die award of any degree or any
professional diploma.
APURV SHARMA
( 0103EX051009 )
VISHAL MODI
( 0103EX051059 )
VIVEK PODDAR
( 0103EX051060 )
Date :
-05-2008
CONTENTS
1.
INTRODUCTION
2.
COMPONENT LIST
3.
DESCRIPTION OF COMPONENTS
4.
OPERATING PRINCIPLE
5.
CIRCUIT DIAGRAMS
6.
WORKING
7.
MANUFACTURING PROCESS
8.
APPLICATION OF CIRCUIT
9.
PRECAUTIONS
INTRODUCTION
This is a simple and easy to use gadget which not only testes the IC 555 timer in its
entire basic configuration but also tests the functionally of each pin of the timer.
Once a timer is declared fit by this gadget, it will function satisfactorily in whatever
mode or configuration you may try it.
The circuit thus can be used to check:
(1) The timer IC in astable configuration.
(2) the timer IC in monostable configuration
(3) The capability of reset terminal to over ride all function and rest the output to
low.
(4) The function of the control terminal to change the ‘on’ or ‘high’ time of output
wave form in astable mode of operation and the output pulse width in
monostable mode of operation.
IC 555 TIMER –
The 555 is an integrated circuit (chip) implementing a variety of timer and
multivibrator applications. The IC was designed and invented by Hans R.
Camenzind. It was designed in 1970 and introduced in 1971 by Signetics (later
acquired by Philips). The original name was the SE555/NE555 and was called "The
IC Time Machine". It is still in wide use, thanks to its ease of use, low price and
good stability. As of 2006, 1.5 billion units are manufactured every year.
The 555 timer is one of the most popular and versatile integrated circuits ever
produced. It includes 23 transistors, 2 diodes and 16 resistors on a silicon chip
installed in an 8-pin mini dual-in-line package (DIP-8). The 556 is a 14-pin DIP that
combines two 555s on a single chip. The 558 is a 16-pin DIP that combines four,
slightly modified, 555s on a single chip (DIS & THR are connected internally; TR is
falling edge sensitive instead of level sensitive). Also available are ultra-low power
versions of the 555 such as the 7555 and TLC555. The 7555 requires slightly
different wiring using fewer external components and less power.
The 555 has three operating modes:
Monostable mode:
in this mode, the 555 functions as a "one-shot". Applications include timers, missing
pulse
detection,
bouncefree
switches,
touch
switches,
Frequency
Divider,Capacitance Measurement, Pulse Width Modulation (PWM) etc.
Astable mode :
Free Running mode: the 555 can operate as an oscillator. Uses include LED and
lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse
position modulation, etc.
Bistable mode:
the 555 can operate as a flip-flop, if the DIS pin is not connected and no capacitor is
used. Uses include bouncefree latched switches, etc.
The connection of the pins is as follows:
1.
2.
3.
4.
GND
TR
Q
R
5.
CV
6.
THR
7.
DIS
8.
V+, VCC
Ground, low level
A short pulse high → low on the trigger starts the timer
During a timing interval, the output stays at +VCC
A timing interval can be interrupted by applying a reset pulse to
low (0V)
Control voltage allows access to the internal voltage divider
(2/3 VCC)
The threshold at which the interval ends
(it ends if U.thr → 2/3 VCC)
Connected to a capacitor whose discharge time will influence
the timing interval.
The positive supply voltage which must be between 5 and 15 V,
high level
Schematic diagram :
Real picture
COMPONENT LIST
Number
Quantity
1. IC’S
IC-555
1
2. Transistors
BC548
2
3. Light emitting diodes (LED’S)
Red
Green
1
1
4. Electrolytic capacitors
10F/25V
100/25V
2
2
5. Ceramic capacitors
0.1
0.01
1
1
6. Variable resistor
Preset 1M
1
7. Carbon resistor
100K
10K
1K
1M
.33K
.47K
470K
2
2
2
1
1
1
1
8. Piezo element
1
10. 9V Battery
1
11. Switch
1
12. Miscellaneous
Icbase (8 pin)
Switch connector
Ferric chloride
Soldering wire
Soldering paste
Connecting wire
2
1
DISCRIPTION OF COMPONENTS
RESISTORS A Resistor is a heat-dissipating element and in the electronic circuits it is
mostly used for either controlling the current in the circuit or developing a voltage
drop across it, which could be utilized for many applications. There are various types
of resistors, which can be classified according to a number of factors depending
upon:
(I)
Material used for fabrication
(II)
Wattage and physical size
(III) Intended application
(IV) Ambient temperature rating
(V)Cost
Basically the resistor can be split in to the following four parts from the construction
viewpoint.
(1) Base
(2) Resistance element
(3) Terminals
(4) Protective means.
The following characteristics are inherent in all resistors and may be controlled by
design considerations and choice of material i.e. Temperature co–efficient of
resistance, Voltage co–efficient of resistance, high frequency characteristics, power
rating, tolerance & voltage rating of resistors. Resistors may be classified as
(1) Fixed
(2) Semi variable
(3) Variable resistor.
In our project carbon resistors are being used.
CAPACITORS:
The fundamental relation for the capacitance between two flat plates separated by a
dielectric material is given by:C=0.08854KA/D
Where: C= capacitance in pf.
K= dielectric constant
A=Area per plate in square cm.
D=Distance between two plates in cm
Design of capacitor depends on the proper dielectric material with particular
type of application. The dielectric material used for capacitors may be grouped in
various classes like Mica, Glass, air, ceramic, paper, Aluminum, electrolyte etc. The
value of capacitance never remains constant. It changes with temperature, frequency
and aging. The capacitance value marked on the capacitor strictly applies only at
specified temperature and at low frequencies.
LED (Light Emitting Diodes):
As its name implies it is a diode, which emits light when forward biased. Charge
carrier recombination takes place when electrons from the N-side cross the junction
and recombine with the holes on the P side. Electrons are in the higher conduction
band on the N side whereas holes are in the lower valence band on the P side.
During recombination, some of the energy is given up in the form of heat and light.
In the case of semiconductor materials like Gallium arsenide (GaAs), Gallium
phoshide (Gap) and Gallium arsenide phoshide (GaAsP) a greater percentage of
energy is released during recombination and is given out in the form of light. LED
emits no light when junction is reverse biased.
TRANSISTOR: A transistor consists of two junctions formed by sandwiching either p-type or n-type
semiconductor between a pair of opposite types. Accordingly, there are two types of
transistors namely: (1) n-p-n transistor
(2) p-n-p transistor
(NPN)
(PNP)
An n-p-n transistor is composed of two n-type semiconductors separated by a thin
section of p type. However a p-n-p transistor is formed by two p sections separated
by a thin section of n-type. In each type of transistor the following points may be
noted.
1.
There are two p-n junctions, therefore a transistor may be regarded as
combination of two diodes connected back to back.
2.
There are three terminals taken from each type of semiconductor.
3.
The middle section is a very thin layer, which is the most important factor in
the functioning of a transistor.
4.
Transistor can be used as an Amplifier also.
A transistor raises the strength of a weak signal and thus acts as an amplifier.
The weak signal is applied between emitter base junction and output is taken across
the load Rc connected in the collector circuit (in common emitter configuration). In
order to achieve faithful amplification, the input circuit should always remain
forward biased.
To do so, a dc voltage is applied in the input in addition to the signal. This dc
Voltage is known as biasing voltage and its magnitude and polarity should be such
that it always keeps the input circuit forward biased regardless of the polarity to the
signal to be amplified.
As the input circuit has low resistance a small change in signal voltage causes
an appreciable change in emitter current. This causes change in collector current (by
a factor called current gain of transistor) due to transistor action. The collector
current flowing through a high load resistance Rc produces a large voltage across it.
Thus a weak signal applied to the input circuit appears in the amplified form in the
collector circuit. This is how a transistor acts as an amplifier.
Transistor may be used in different configuration like CB (common base) & CC
(common collector) according to requirements of amplifier (impedance matching,
buffer amplifier etc.).
DIODES :
-
+
Diode is a two-terminal device (except that thermionic diodes may also have one or
two ancillary terminals for a heater). consisting of a P-N junction formed either of
Ge or Si crystal. The P and N type regions are referred to as anode and cathode
respectively. Diodes have two active electrodes between which the signal of interest
may flow, and most are used for their unidirectional current property. The varicap
diode is used as an electrically adjustable capacitor.
The directionality of current flow most diodes exhibit is sometimes generically called
the rectifying property. The most common function of a diode is to allow an electric
current to pass in one direction (called the forward biased condition) and to block it
in the opposite direction (the reverse biased condition). Thus, the diode can be
thought of as an electronic version of a check valve. Real diodes do not display such
a perfect on-off directionality but have a more complex non-linear electrical
characteristic, which depends on the particular type of diode technology. Diodes
also have many other functions in which they are not designed to operate in this onoff manner.
OPERATING PRINCIPLE
The two basic configurations in which a timer ic 555 can be used are the astable and
the monostable modes of operation.When the DPDT switch (s2) is in position 1-1,
the timer under test automatically gets wired as a monostable multivibrator. In this
case, the microswitch (S1) can trigger the monoshot. The denouncing circuit
constituted by the two NAND gates of IC1 (N1 and N2) produces a clean
rectangular pulse when the microswitch is pressed. Resistor R3, capacitor C1 and
diode D1 ensure that the trigger terminal of timer IC 555 (pin 2 the trigger terminal)
gets the desired positive to ground trigger pulse. This differentiator circuit also
ensures that the width of the trigger pulse is less than expected monoshot output
pulse.
The monoshot output pulse width is a function of the series combination of series
combination of resistor R8 and potentiometer VR2, and capacitor C4, when DPDT
switch S2 is in position 2-2, the timer gets configured for the astable mode of
operation. The output is a pulse train with the high time period determine by the
series combination of resistor R8, potentiometer VR2, resistor R9 and capacitor C4,
whereas the low time period is determined by resistor R9 and capacitor C4.
The reset terminal of timer IC (pin 4) should be tied to Vcc normally. More
precisely, the voltage at the pin 4 should be greater than 0.8 volt a voltage less than
resets the output .Whether you have connected the timer in the monoshot or astable
mode of operation, the output goes low the moment you bring the reset terminal
below 0.8V.
The control terminal (pin 5) can be used to change the high time (on time) of the
output pulse train in the astable mode and the output pulse width in the monoshot
mode by applying an external voltage. This external voltage basically changes the
reference voltage levels of the comparator inside the IC. The level are set by three
identical resistors of usually 5 kilo-ohms inside the IC connected from Vcc to
ground, at 2/3Vcc for pin 5 and 1/3 Vcc for pin 2. These levels can be changed by
connecting an external resistor between pin 5 and ground. Resister R10 and
potentiometer VR3 have been connected for this purpose.
The pulse width in the monoshot mode is given by:
(a) 1.1*total charging resistance charging capacitance.
(b) This expression is valid when three is no external resistor connected at pin 5.
The pulse width can be reduced by connecting an external resistor.
(c) The high and low time periods in the astable mode are:
High time period = 0.69*charging resistance*charging capacitance
Low time period = 0.69* charging resistance*charging capacitance.
Again the expressions sure true with no external resister at pin5. The high time
period can be made to decrease by connecting an external resistor between pin
5&Gnd.
CIRCUIT DESIGN
CIRCUIT DIAGRAM OF 555 IC TESTER
PCB LAYOUT :
WORKING
To test an 555 Timer :1. insert into the socket
2. Set the switch S2 in position 1-1.
3. Switch on the power supply by flipping switch S3 to on position .power
indicator LED (LED3) glows to indicate that the circuit is ready to test the IC
TIMER.
4. If the IC is okay, LED1 glows because the IC is wired as a monoshot and in
the absence of any trigger, its output is low.
5. Apply the trigger pulse by momentarily pressing switch s1 .LED1 stop
glowing .This and, in turn, LED2 glows. This confirms that the output of the
monoshot has gone high. After the predetermined time period, LED2 goes
off and LED1 again glows .Very preset VR2 and trigger the monoshot again
through switch S1. You will find that LED2 glows this time for a longer or a
smaller time period depending upon whether you increased or decreased VR2
resistance.
6. For checking the reset function of the timer, trigger the monoshot again, and
before the expected time is over, quickly decrease the pot meter VR1
resistance to bring the voltage at pin 4 below 0.8V .You will observe the
output going low (indicated by glowing LED1 and extinguished LED2).
7. For checking the control function of the timer IC, set potmeter VR1 again in
the maximum resistance position. Also set preset VR3 in the minimum
position .Trigger the monoshot using switch S1 .You will observe its output
going high for a time period that is much less than that determined from the
series combination of R8 and VR2, and capacitor C4. In fact, for any fixed
setting of this series combination, the output pulse width can be observed to
very for different values of potmeter VR3 resistance –by triggering the
monoshot several time, once for each setting of VR3.
8. Now set the DPDT switch in position in position 2-2 LED1 and LED2 glow
alternatively with the timing determined by the resistance in charge and
discharge paths. This means the timer IC is okay and wired in astable mode.
9. The function of reset and control pins can be checked in astable configuration
too in the same way as discussed above for the monoshot configuration.
P.C.B. MANUFACTURING PROCESS
It is an important process in the fabrication of electronic equipment. The design of
PCBs (Printed Circuit Boards) depends on circuit requirements like noise immunity,
working frequency and voltage levels etc. High power PCBs requires a special design
strategy.
The fabrication process to the printed circuit board will determine to a large extent
the price and reliability of the equipment. A common target aimed is the fabrication
of small series of highly reliable professional quality PCBs with low investment. The
target becomes especially important for customer tailored equipments in the area of
industrial electronics.
The layout of a PCB has to incorporate all the information of the board before one
can go on the artwork preparation. This means that a concept which clearly defines
all the details of the circuit and partly defines the final equipment, is prerequisite
before the actual lay out can start. The detailed circuit diagram is very important for
the layout designer but he must also be familiar with the design concept and with the
philosophy behind the equipment.
BOARD TYPES:
1.
Single Sided Boards
The single sided PCBs are mostly used in entertainment electronics where
manufacturing costs have to be kept at a minimum. However in industrial
electronics cost factors cannot be neglected and single sided boards should be
used wherever a particular circuit can be accommodated on such boards.
2.
Double Sided Boards
Double-sided PCBs can be made with or without plated through holes. The
production of boards with plated through holes is fairly expensive. Therefore
plated through hole boards are only chosen where the circuit complexities and
density of components does not leave any other choice.
CHRONOLOGY
The following steps have been followed in carrying out the project.
1.
Study the books on the relevant topic.
2.
Understand the working of the circuit.
3.
Prepare the circuit diagram.
4.
Prepare the list of components along with their specification.
5.
Estimate the cost and procure them after carrying out market survey.
6.
Plan and prepare PCB for mounting all the components.
7.
Fix the components on the PCB and solder them.
8.
Test the circuit for the desired performance.
9.
Trace and rectify faults if any.
10.
Give good finish to the unit.
11.
Prepare the project report.
DESIGN SPECIFICATION
(I)
STEPS TAKEN WHILE PREPARING CIRCUIT
(A)
PCB DESIGNING
The main purpose of printed circuit is in the routing of electric currents and signal
through a thin copper layer that is bounded firmly to an insulating base material
sometimes called the substrate. This base is manufactured with an integrally
bounded layers of thin copper foil which has to be partly etched or removed to
arrive at a pre-designed pattern to suit the circuit connections or other applications
as required.
The term printed circuit board is derived from the original method where a printed
pattern is used as the mask over wanted areas of copper. The PCB provides an ideal
baseboard upon which to assemble and hold firmly most of the small components.
From the constructor’s point of view, the main attraction of using PCB is its role as
the mechanical support for small components. There is less need for complicated
and time consuming metal work of chassis contraception except perhaps in
providing the final enclosure. Most straight forward circuit designs can be easily
converted in to printed wiring layer the thought required to carry out the inversion
cab footed high light an possible error that would otherwise be missed in
conventional point to point wiring .The finished project is usually neater and truly a
work of art.
Actual size PCB layout for the circuit shown is drawn on the copper board. The
board is then immersed in FeCl3 solution for 12 hours. In this process only the
exposed copper portion is etched out by the solution.
Now the petrol washes out the paint and the copper layout on PCB is rubbed with a
smooth sand paper slowly and lightly such that only the oxide layers over the Cu are
removed. Now the holes are drilled at the respective places according to component
layout as shown in figure.
(B)
LAYOUT DESIGN:
When designing the layout one should observe the minimum size (component body
length and weight). Before starting to design the layout we need all the required
components in hand so that an accurate assessment of space can be made. Other
space considerations might also be included from case to case of mounted
components over the printed circuit board or to access path of present components.
It might be necessary to turn some components around to a different angular
position so that terminals are closer to the connections of the components. The
scale can be checked by positioning the components on the squared paper. If any
connection crosses, then one can reroute to avoid such condition.
All common or earth lines should ideally be connected to a common line routed
around the perimeter of the layout. This will act as the ground plane. If possible try
to route the outer supply line to the ground plane. If possible try to route the other
supply lines around the opposite edge of the layout through the center. The first set
is tearing the circuit to eliminate the crossover without altering the circuit detail in
any way.
Plan the layout looking at the topside to this board. First this should be translated
inversely, later for the etching pattern large areas are recommended to maintain good
copper adhesion. It is important to bear in mind always that copper track width
must be according to the recommended minimum dimensions and allowance must
be made for increased width where termination holes are needed. From this aspect,
it can become little tricky to negotiate the route to connect small transistors.
There are basically two ways of copper interconnection patterns under side the
board. The first is the removal of only the amount of copper necessary to isolate the
junctions of the components to oneanother. The second is to make the
interconnection pattern looking more like conventional point wiring by routing
uniform width of copper from component to component.
(C)
ETCHING PROCESS:
Etching process requires the use of chemicals. acid resistant dishes and running
water supply. Ferric chloride is mostly used solution but other etching materials such
as ammonium per sulphate can be used. Nitric acid can be used but in general it is
not used due to poisonous fumes.
The pattern prepared is glued to the copper surface of the board using a latex type
of adhesive that can be cubed after use. The pattern is laid firmly on the copper
using a very sharp knife to cut round the pattern carefully to remove the paper
corresponding to the required copper pattern areas. Then apply the resistant
solution, which can be a kind of ink solution for the purpose of maintaining smooth
clean outlines as far as possible. While the board is drying, test all the components.
Before going to next stage, check the whole pattern and cross check with the circuit
diagram. Check for any free metal on the copper. The etching bath should be in a
glass or enamel disc. If using crystal of ferric- chloride these should be thoroughly
dissolved in water to the proportion suggested. There should be 0.5 lt. of water for
125 gm of crystal.
To prevent particles of copper hindering further etching, agitate the solutions
carefully by gently twisting or rocking the tray.
The board should not be left in the bath a moment longer than is needed to remove
just the right amount of copper. Inspite of there being a resistive coating there is no
protection against etching away through exposed copper edges. This leads to over
etching. Have running water ready so that etched board can be removed properly
and rinsed. This will halt etching immediately.
Drilling is one of those operations that calls for great care. For most purposes a
0.5mm drill is used. Drill all holes with this size first those that need to be larger can
be easily drilled again with the appropriate larger size.
(D) COMPONENT ASSEMBLY: -
From the greatest variety of electronic components available, which runs into
thousands of different types it is often a perplexing task to know which is right for a
given job.
There could be damage such as hairline crack on PCB. If there are, then they can be
repaired by soldering a short link of bare copper wire over the affected part.
The most popular method of holding all the items is to bring the wires far apart after
they have been inserted in the appropriate holes. This will hold the component in
position ready for soldering.
Some components will be considerably larger .So it is best to start mounting the
smallest first and progressing through to the largest. Before starting, be certain that
no further drilling is likely to be necessary because access may be impossible later.
Next will probably be the resistor, small signal diodes or other similar size
components. Some capacitors are also very small but it would be best to fit these
afterwards. When fitting each group of components mark off each one on the circuit
as it is fitted so that if we have to leave the job we know where to recommence.
Although transistors and integrated circuits are small items there are good reasons
for leaving the soldering of these until the last step. The main point is that these
components are very sensitive to heat and if subjected to prolonged application of
the soldering iron, they could be internally damaged.
All the components before mounting are rubbed with sand paper so that oxide layer
is removed from the tips. Now they are mounted according to the component
layout.
(E) SOLDERING: -
This is the operation of joining the components with PCB after this operation the
circuit will be ready to use to avoid any damage or fault during this operation
following care must be taken.
1. A longer duration contact between soldering iron bit & components lead can
exceed the temperature rating of device & cause partial or total damage of the
device. Hence before soldering we must carefully read the maximum soldering
temperature & soldering time for device.
2. The wattage of soldering iron should be selected as minimum as permissible for
that soldering place.
3 .To protect the devices by leakage current of iron its bit should be earthed
properly.
4. We should select the soldering wire with proper ratio of Pb & Tn to provide the
suitable melting temperature.
5. Proper amount of good quality flux must be applied on the soldering point to
avoid dry soldering.
APPLICATION OF CIRCUIT
The circuit thus can be used to check:
a. The timer IC in astable configuration.
b. The timer IC in monostable configuration
c. The capability of reset terminal to override all function and rest the output
to low.
d. The function of the control terminal to change the ‘on’ or ‘high’ time of
output wave form in astable mode of operation and the output pulse
width in monostable mode of operation.
This operates on a 9v battery which makes the gadget portable you can
construct easily on any general purpose PCB along with the 8 pin socket.
PRECAUTIONS :
1. The soldering iron being used for soldering of semiconductors should be of
low voltage.
2. While soldering semiconductors heat sinks should be used.
3. While soldering solder should not spread over the entire circuit and solder tip
should be sharp and smooth.
4. While mounting components their values should be visible.
5. Semiconductors and other polarized components should be mounted with
correct polarity.
6. Time should be carefully observed while etching process takes place on the
PCB.