Up/down counter
Synopsis
Submitted in partial fullfillment for the award of degree
Of
Bachelor in Technology
Submitted by :
Submitted to :
ANOOP KUMAR
DEPARTMENT OF ECE
ROLL-
Department of Electronic & Communication Engineering
Chandigarh Engineering college
Landran , Mohali
Affiliated to PTU, Jalandhar
Session: 2014-2018
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ACKNOWLEDGEMENT
I have taken efforts in this project. However, it would not have been possible without the kind
support and help of many individuals and organizations. I would like to extend my sincere thanks
to all of them.
I am highly indebted to CEC , LANDRAN faculty members for their guidance and constant
supervision as well as for providing necessary information regarding the project & also for their
support in completing the project.
I would like to express my gratitude towards my parents & member of CEC, LANDRAN for
their kind co-operation and encouragement which help me in completion of this project.
I would like to express my special gratitude and thanks to industry persons for giving me such
attention and time.
My thanks and appreciations also go to my colleague in developing the project and people who
have willingly helped me out with their abilities.
THANK YOU
ANOOP KUMAR
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INDEX
PART A: INTRODUCTION TO ELECTRONICS & COMMUNICATION
ENGINEERING
S NO.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
TOPIC
THEORETICAL STUDIES
BASIC COMPONENTS
ACTIVE COMPONENTS
TYPES OF DIODES
TRANSISTOR
FORWARD BIASING
REVERSE BIASING
PASSIVE COMPONENTS
LCD CONSTUCTION AND WORKING PRINCIPLE
MICROCONTROLLERS
SIGNALS
TYPES OF SIGNALS
LOGIC GATES
CRO (CATHODE RAY OSCILLOSCOPE)
COUNTERS
ADDERS
CLIPPER
ZENER DIODE
CLAMPER
3
PAGENO.
6
6
7
7
8
9
10
12
13
14
15
16
17
18
19
20
22
23
24
PART B: MINOR PROJECT
S NO.
TOPIC
PAGE
1
INTRODUCTION
26
2
TYPES OF COUNTERS
27
3
FIELD OF PROJECT
28
4
COMPONENT USED AND DESCRIPTION
29
5
METHODOLOGY
32
6
CIRCUIT DIAGRAM
32
7
WORKING OF PROJECT
34
8
RESULT AND FUTURE SCOPE
35
4
LIST OF FIGURES
FIGURE NO.
PAGE NO
Fig.(1)Basic components
4
Fig.(2) Diodes
5
fig.(3)Gunn diode characteristic
6
Fig(4) NPN Transistor
6
7
Fig(5) PNJunction Diodes
7
Fig(6) Forward Biasing
8
Fig(7) Reverse Biasing
9
Fig(8) Resistor
Fig(9) Capacitor
9
Fig(10) LCD
10
Fig(11) LED TV
11
Fig(12) Microcontroller
12
14
Fig(13) Signal propagation
15
Fig(14) Logic gates
16
Fig(15) CRO
Fig(16)Voltage clipping limits the voltage to a 19
device without affecting the rest of the waveform.
Fig(17) I/P and O/P in Diode clippers
Fig(18) I/P and O/P in Zener Diode
21
22
Fig(19)Clippper
22
5
Fig(20) 7 segment display
30
Fig(21) NE555 timer
31
Fig(22)IC
32
Fig(23)circuit design of 7 segment up down counter 33
Fig(24) 7 segment display pin configuration
34
Fig(25)pin configuration
34
Fig(26)Common anode display and it connection 35
with 74LS47
6
LIST OF ABBREVIATIONS
1. DC – DIRECT CURRENT
2. AC-ALTERNATING CURRENT
3. BJT-BIPOLAR JUNCTION TRANSISTOR
4. IC- INTEGRATED CIRCUIT
5. LCD-LIQUID CRYSTAL DISPLAY
6. LED-LIGHT EMMITING DIODE
7. BCD-BINARY CODED DECIMAL
8. TV-TELEVISION
9. CRT-CATHODE RAY TUBE
10. I/P-INPUT
11. O/P-OUTPUT
12. FET-FIELD EFFECT TRANSISTOR
13. CRO- CATHODE RAY OSCILLOSCOPE
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PART-A
1. THEORETICAL STUDIES
Electronics: It is the science of how to control electric energy, energy in which the electrons
have a fundamental role. Electronics deals with electrical circuits that involve active electrical
components such as vacuum tubes, transistors, diodes and integrated circuits, and associated
passive electrical components and interconnection technologies. Commonly, electronic devices
contain circuitry consisting primarily or exclusively of active semiconductors supplemented with
passive elements; such a circuit is described as an electronic circuit.
2. BASIC COMPONENTS: Electronic component is any basic discrete device or physical
entity in an electronic system used to affect electrons or their associated fields. Electronic
components are mostly industrial products, available in a singular form and are not to be
confused with electrical elements, which are conceptual abstractions representing idealized
electronic
fig.(1)Basic components
They are basically of two types:

Active components rely on a source of energy (usually from the DC circuit, which we have
chosen to ignore) and usually can inject power into a circuit, though this is not part of the
definition Active components include amplifying components such as transistors, triode
vacuum tubes (valves), and tunnel diodes

Passive components can't introduce net energy into the circuit. They also can't rely on a
source of power, except for what is available from the (AC) circuit they are connected to. As
8
a consequence they can't amplify (increase the power of a signal), although they may increase
a voltage or current (such as is done by a transformer or resonant circuit). Passive
components include two-terminal components such as resistors, capacitors, inductors, and
transformers.
3. ACTIVE COMPONENTS
DIODE is a two-terminal electronic component with asymmetric conductance it has low (ideally
zero) resistance to current in one direction, and high (ideally infinite resistance in the other. A
semiconductor diode the most common type today, is a crystalline piece of semiconductor
material with a p–n junction connected to two electrical terminals .A vacuum tube diode has two
electrodes a plate (anode) and a heated cathode. Semiconductor diodes were the first
semiconductor electronic devices was made by German physicist Ferdinand Braun in 1874.
FIG.(2) Diodes
4. TYPES OF DIODES:
1. Gun Diode
2. Zeiner Diode
3. Schottky Diode
4. P-N Junction
5. Tunnel Diode
Gun Diode
The Gun diode is not like a typical PN junction diode. Rather than having both p-type and n-type
semiconductor, it only utilises n-type semiconductor where electrons are the majority carriers.
The operation of the Gunn diode can be explained in basic terms. When a voltage is placed across
the device, most of the voltage appears across the inner active region. As this is particularly thin
this means that the voltage gradient that exists in this region is exceedingly high.
9
The device exhibits a negative resistance region on its V/I curve as seen below. This negative
resistance area enables the Gunn diode to amplify signals. This can be used both in amplifiers and
oscillators.
However
Gunn
diode
oscillators
are
the
most
commonly
found.
fig.(3)Gunn diode characteristic
This negative resistance region means that the current flow in diode increases in the negative
resistance region when the voltage falls - the inverse of the normal effect in any other positive
resistance element.
5. TRANSISTOR: A transistor is a semiconductor device used to amplify and switch
electronic signals and electrical power it is composed 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 through another pair of terminals. Because the
controlled (output) power can be higher than the controlling (input) power, a transistor can
amplify a signal. Today, some transistors are packaged individually, but many more are found
embedded in integrated circuits.
Bipolar junction transistor (BJT, or simply "transistor") – NPN or PNP
Fig(4) NPN Transistor
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Integrated Circuit: It is a set of electronic circuits on one small plate ("chip") of semiconductor
material, normally silicon. This can be made much smaller than a discrete circuit made from
independent electronic components ICs can be made very compact, having up to several
billion transistors and other electronic components in an area the size of a fingernail. The width
of each conducting line in a circuit can be made smaller and smaller as the technology advances;
in 2008 it dropped below 100 nanometers and now is tens of nanometer
PN JUNCTION DIODE:-
Fig(5) PNJunction Diodes
6. FORWARD BIASING
Fig(6) Forward Biasing
In forward bias, the holes in the p-region are shifted to the n-region and electrons in the n- region
shifted to the p-region because of repulsion with battery terminals. As a result, the thickness of
the depletion layer is decreased because the intensity of +ve and -ve ions is decreased in the
depletion layer because the electrons are came into this layer through the connecting wires and
11
goes near to the +ve ions and hence +ve ions disappeared similarly at -ve ions. The electrons are
attracted by battery +ve terminal and hence -ve ions disappeared.
Thus, the depletion layer thickness decreases as a result of the charge carriers easily cross that
layer. Hence conduction exist through the pn junction diode
7. REVERSE BIASING:
Fig(7) Reverse Biasing
Reverse biasing Diode does not conduct with change in applied voltage. The current remains
constant at a negligibly small value (in the range of micro amps) for a long range of change in
applied voltage. When the voltage is raised above a particular point, say 80 volts, the current
suddenly shoots (increases suddenly). This is called as “reverse current” and this particular
value of applied voltage, where reverse current through diode increases suddenly is known as
“break down voltage“
8. PASSIVE COMPONENTS
RESISTORS:
It is passive two-terminal electrical component that implements electrical
resistance as a circuit element. Resistors act to reduce current flow, and, at the same time, act to
lower voltage levels within circuits. In electronic circuits resistors are used to limit current flow,
to adjust signal levels, bias active elements, terminate transmission lines among other uses.
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Fig(8) Resistor
CAPACITOR
A capacitor (originally known as a condenser) is a passive two-terminal electrical component
used to store energy electrostatically in an electric field. The forms of practical capacitors vary
widely, but all contain at least two electrical conductors (plates) separated by a dielectric (i.e.
insulator).
Fig(9) Capacitor
INDUCTOR
An inductor, also called a coil or reactor, is a passive two-terminal electrical component which
resists changes in electric current passing through it. It consists of a conductor such as a wire,
usually wound into a coil. When a current flows through it, energy is stored temporarily in a
magnetic field in the coil.
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9. LCD CONSTUCTION AND WORKING PRINCIPLE
A liquid crystal display or LCD draws its definition from its name itself. It is combination of two
states of matter, the solid and the liquid. LCD uses a liquid crystal to produce a visible image.
Liquid crystal displays are super-thin technology display screen that are generally used in laptop
computer screen, TVs, cell phones and portable video games. LCD’s technologies allow displays
to be much thinner when compared to cathode ray tube (CRT) technology
Fig(10) LCD
PRINCIPLE: Behind the LCD’s is that when an electrical current is applied to the liquid
crystal molecule, the molecule tends to untwist. This causes the angle of light which is passing
through the molecule of the polarized glass and also cause a change in the angle of the top
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polarizing filter. As a result a little light is allowed to pass the polarized glass through a particular
area of the LCD. Thus that particular area will become dark compared to other. The LCD works
on the principle of blocking light. While constructing the LCD’s, a reflected mirror is arranged at
the back. The complete region of the LCD has to be enclosed by a common electrode and above
it should be the liquid crystal matter.Next comes to the second piece of glass with an electrode in
the form of the rectangle on the bottom and, on top, another polarizing film. It must be
considered that both the pieces are kept at right angles. When there is no current, the light passes
through the front of the LCD it will be reflected by the mirror and bounced back. As the electrode
is connected to a battery the currentfrom it will cause the liquid crystals between the commonplane electrode and the electrode shaped like a rectangle to untwist. Thus the light is blocked
from passing through.
.
WHY LED IS BETTER PROSPECTIVE THEN LCD?
An LED TV uses less power, provides a brighter display with better contrast, a thinner panel, and
lesser heat dissipation than a conventional LCD TV. This is because an LED TV uses lightemitting diodes for backlighting as opposed to the CCFLs of conventional LCD TVs. The display
of an LED TV is not an LED display so a more technically correct name for it would be "LEDbacklit LCD television."
Fig(11) LED TV
15
11. MICROCONTROLLERS: A microcontroller is a small computer on a single
integrated circuit containing a processor core, memory and output/input peripherals,
Programming memory in the form of Ferroelectric ROM.
Microcontrollers are used in automatically controlled products and devices, such as automobile
engine control systems, implantable medical devices, remote controls, office machines,
appliances, power tools, toys and other embedded system.
Fig(12) Microcontroller
8051 MICROCONTROLLER OVERVIEW:
1. 4 Kb of ROM is not much at all.
2. 128b of RAM (including SFRs) satisfies the user's basic needs.
3. 4 ports having in total of 32 input/output lines are in most cases sufficient to make all
necessary connections to peripheral environment.
11. SIGNALS
A signal as referred to in communication systems, and electronic "is a function that
conveys information about the behavior or attributes of some phenomenon". In the physical
world, any quantity exhibiting variation in time or variation in space (such as an image) is
potentially a signal that might provide information on the status of a physical system, or convey
a message between observers, among other possibilities. The IEEE Transactions on Signal
16
Processing states that the term "signal" includes audio, video, speech, image, communication,
geophysical, sonar, radar, medical and musical signals.
Other examples of signals are the output of a thermocouple, which conveys temperature
information, and the output of a pH meter which conveys acidity information. Typically, signals
are often provided by a sensor, and often the original form of a signal is converted to another
form of energy using a transducer. For example, a microphone converts an acoustic signal to
a voltage waveform, and a speaker does the reverse.
12. TYPES OF SIGNALS

ANALOG and DIGITAL SIGNALS:
ANALOG SIGNAL:Analog or analogue signal is any continuous signal for which the time
varying feature (variable) of the signal is a representation of some other time varying quantity,
i.e., analogous to another time varying signal. For example, in an analog audio signal, the
instantaneous voltage of the signal varies continuously with the pressure of the sound waves. It
differs from a digital signal, in which a continuous quantity is represented by a discrete
function which can only take on one of a finite number of values. The term analog signal usually
refers to electrical signals; however, mechanical, pneumatic, hydraulic, human speech, and other
systems may also convey or be considered analog signals.
An analog signal uses some property of the medium to convey the signal's information. For
example, an aneroid barometer uses rotary position as the signal to convey pressure information.
In an electrical signal, the voltage, current, requency of the signal may be varied to represent the
information.
DIGITAL SIGNALS:
A digital signal is a physical signal that is a representation of a sequence of discrete values
(a quantified discrete-time
signal),
for
example
of
an
arbitrary bit
stream,
or
of
adigitized (sampled and analog-to-digital converted) analog signal. The term digital signal can
refer to either of the following:
any continuous-time waveform signal used in digital communication, representing a bit stream or
other sequence of discrete valuesa pulse train signal that switches between a discrete number of
17
voltage
levels
or
levels
of
light
intensity,
also
known
as
a line
coded signal
or baseband transmission, for example a signal found in digital electronics or in serial
communications, or a pulse code modulation (PCM) representation of a digitized analog signal.
A signal that is generated by means of digital modulationpass ", to be transferred
between modems, is in the first case considered as a digital signal, and in the second case as
converted to an analog signal
SIGNAL PROCESSING: Signal processing is an enabling technology that encompasses
the fundamental theory, applications, algorithms, and implementations of processing or
transferring information contained in many different physical, symbolic, or abstract formats
broadly designated as signals. It uses mathematical, statistical, computational, heuristic, and
linguistic representations, formalisms, and techniques for representation, modelling, analysis,
synthesis, discovery, recovery, sensing, acquisition, extraction, learning, security, or forensics.
.
Fig(13) Signal propagation
13. LOGIC GATES :In electronics, a logic gate is an idealized or physical device implementing a Boolean function;
that is, it performs a on one or more logical inputs, and produces a single logical output.
Depending on the context, the term may refer to an ideal logic gate, one that has for instance
zero rise time and unlimited fan-out, or it may refer to a non-ideal physical device] (see Ideal and
real op-amps for comparison).
Logic gates are primarily implemented using diodes or transistors acting as es, but can also be
constructed using vacuum tubes, electromagnetic relays (relay logic), fluidic logic, pneumatic
logic, optics, molecules, or even mechanica""elements. With amplification, logic gates can be
18
cascaded in the same way that Boolean functions can be composed, allowing the construction of
a physical model of all of Boolean logic, and therefore, all of the algorithms and mathematics that
can be described with Boolean multiplexers Logic circuits include such devices as , (ALUs),
and computer memory, all the way up through complete microprocessors, which may contain
more than 100 million gates. In modern practice, most gates are made from field-effect
transistors (FETs), particularly MOSFETs (metal–oxide–semiconductor field-effect transistors)
TYPES OF LOGIC GATES:
•
OR GATE.
•
AND GATE.
•
NOR GATE.
•
NAND GATE.
•
EX_OR GATE.
•
EX_NOR GATE
Fig(14) Logic gates
VARIOUS LOGIC GATES WITH THEIR BOOLEAN EXPRESSIONS ARE SHOWN ABOVE
19
14. CRO (CATHODE RAY OSCILLOSCOPE)
The cathode ray oscilloscope is an extremely useful and versatile laboratory instrument used for
studying wave shapes of alternating currents and voltages as well as for measurement of voltage,
current, power and frequency, in fact, almost any quantity that involves amplitude and waveform.
It allows the user to see the amplitude of electrical signals as a function of time on the screen. It is
widely used for trouble shooting radio and TV receivers as well as laboratory work involving
research and” design. It can also be employed for studying the wave shape of a signal with
respect to amplitude distortion and deviation from the normal. In true sense the cathode ray
oscilloscope has been one of the most important tools in the design and development of modern
electronic circuits.
Fig(15) CRO
The instrument employs a cathode ray tube (CRT), which is the heart of the oscilloscope. It
generates the electron beam, accelerates the beam to a high velocity, deflects the beam to create
the image, and contains a phosphor screen where the electron beam eventually becomes visible.
For accomplishing these tasks various electrical signals and voltages are required, which are
provided by the power supply circuit of the oscilloscope. Low voltage supply is required for the
heater of the electron gun for generation of electron beam and high voltage, of the order of few
thousand volts, is required for cathode ray tube to accelerate the beam. Normal voltage supply,
say a few hundred volts, is required for other control circuits of the oscilloscope.
20
Horizontal and vertical deflection plates are fitted between electron gun and screen to deflect the
beam according to input signal. Electron beam strikes the screen and creates a visible spot. This
spot is deflected on the screen in horizontal direction (X-axis) with constant time dependent rate.
This is accomplished by a time base circuit provided in the oscilloscope. The signal to be viewed
is supplied to the vertical deflection plates through the vertical amplifier, which raises the
potential of the input signal to a level that will provide usable deflection of the electron beam.
Now electron beam deflects in two directions, horizontal on X-axis and vertical on Y-axis. A
triggering circuit is provided for synchronizing two types of deflections so that horizontal
deflection starts at the same point of the input vertical signal each time it sweeps.
15. COUNTERS
In digital logic and computing, a counter is a device which stores (and sometimes displays) the
number of times a particular event or process has occurred, often in relationship to a clock signal.
The most common type is a sequential digital logic circuit with an input line called the "clock"
and multiple output lines. The values on the output lines represent a number in
the binary or BCD number
system.
Each
pulse
applied
to
the
clock
input increments or decrements the number in the counter.
A counter circuit is usually constructed of a number of flip-flops connected in cascade. Counters
are a very widely-used component in digital circuits, and are manufactured as separate integrated
circuits and also incorporated as parts of larger integrated circuits.
TYPES OF COUNTERS:
1.
ASYNCHRONOUS COUNTERS
2.
SYNCHRONOUS COUNTERS
3.
DECADE COUNTERS
4.
RING COUNTERS
5.
JOHNSON COUNTERS
ASYNCHRONOUS COUNTERS: An asynchronous (ripple) counter is a single d-type
flip-flop, with its J (data) input fed from its own inverted output. This circuit can store one bit,
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and hence can count from zero to one before it overflows (starts over from 0). This counter will
increment once for every clock cycle and takes two clock cycles to overflow, so every cycle it
will alternate between a transition from 0 to 1 and a transition from 1 to 0.
SYNCHRONOUS COUNTERS: In synchronous counters, the clock inputs of all the flipflops are connected together and are triggered by the input pulses. Thus, all the flip-flops change
state simultaneously (in parallel). Synchronous counters can also be implemented with
hardware finite-state machines, which are more complex but allow for smoother, more stable
transitions
DECADE COUNTERS: A decade counter is one that counts in decimal digits, rather than
binary. A decade counter may have each (that is, it may count in binary-coded decimal, as
the 7490 integrated circuit did) or other binary encodings. "A decade counter is a binary counter
that is designed to count to 1010b (decimal 10).
A decade counter is one that counts in decimal digits, rather than binary. It counts from 0 to 9 and
then resets to zero. The counter output can be set to zero by pulsing the reset line low. The count
then increments on each clock pulse until it reaches 1001 (decimal 9
RING COUNTER:
A ring counter is a circular shift register which is initiated such that only one of its flip-flops is
the state one while others are in their zero states.
A ring counter is a Shift Register (a cascade connection of flip-fliop) with the output of the last
one connected to the input of the first, that is, in a ring. Typically, a pattern consisting of a single
bit is circulated so the state repeats every n clock cycles if n flip-flops are used.
JOHANSANCOUNTERS:
A Johnson counter (or switchtail ring counter, twisted-ring counter, walking-ring counter, or
Moebius counter) is a modified ring counter, where the output from the last stage is inverted and
fed back as input to the first stage.[ The register cycles through a sequence of bit-patterns, whose
length is equal to twice the length of the shift register, continuing indefinitely. These counters
find specialist applications, including those similar to the decade counter, digital-to-analog
22
conversion, etc. They can be implemented easily using D- or JK-type flip-flops. It is also known
as twisted ring counter.
16. ADDERS
In electronics,
an adder or summer is
a
device that
performs addition of
numbers.
In
many computers and other kinds of processors, adders are used not only in the logic, but also in
other parts of the processor, where they are used to calculate addresses, table indices, increment
and dicrement, and similar operations
. The half adder adds two single binary digits A and B. It has two outputs, sum (S) and carry (C).
The carry signal represents an overflow into the next digit of a multi-digit addition. The value of
the sum is 2C + S.
The half adder adds two input bits and generates a carry and sum, which are the two outputs of a
half adder. The input variables of a half adder are called the augend and addend bits. The output
variables are the sum and carry.
Truth table for half adder is as follows:-
Inputs
Outputs
A
B
C
S
0
0
0
0
1
0
0
1
0
1
0
1
1
1
1
0
Fig (15) Truth table for half adders
23
17. CLIPPERS:In electronics, a clipper is a device designed to prevent the output of a circuit from exceeding a
predetermined voltage level without distorting the remaining part of the applied waveform.
A clipping circuit consists of linear elements like resistors and non-linear elements like junction
diodes or transistors, but it does not contain energy-storage elements like capacitors. Clipping
circuits are used to select for purposes of transmission, that part of a signal wave form which lies
above or below a certain reference voltage level.
Thus a clipper circuit can remove certain portions of an arbitrary waveform near the positive or
negative peaks. Clipping may be achieved either at one level or two levels. Usually under the
section of clipping, there is a change brought about in the wave shape of the signal.
Clipping circuits are also called slicers, amplitude selectors or limiters.
Fig(16)Voltage clipping limits the voltage to a device without affecting the rest of the
waveform.
TYPES
DIODE CLIPPER
A simple diode clipper can be made with a diode and a resistor. This will remove either the
positive, or the negative half of the waveform depending on the direction the diode is connected.
The simple circuit clips at zero voltage (or to be more precise, at the small forward voltage of the
forward biased diode) but the clipping voltage can be set to any desired value with the addition of
a reference voltage. The diagram illustrates a positive reference voltage but the reference can be
24
positive or negative for both positive and negative clipping giving four possible configurations in
all.
The simplest circuit for the voltage reference is a resistor potential divider connected between the
voltage rails. This can be improved by replacing the lower resistor with a zener diode with a
breakdown voltage equal to the required reference voltage. The zener acts as a voltage regulator
stabilising the reference voltage against supply and load variations.
Fig(15) I/P and O/P in Diode clippers
18. ZENER DIODE:In the example circuit , two zener diodes are used to clip the voltage VIN. The voltage in either
direction is limited to the reverse breakdown voltage plus the voltage drop across one zener
diode.
Fig(16) I/P and O/P in Zener Diode
OP-AMP PRECISION CLIPPER :25
For very small values of clipping voltage on low-level signals the I-V curve of the diode can
result in clipping onset that is not very sharp. Precision clippers can be made by placing the
clipping device in the feedback circuit of an operational amplifier in a similar way to precision
rectifiers.
An operational amplifier (abbreviated op-amp) is an integrated circuit . In other words, the lowvoltage clipping circuit has no effect on voltages greater than Vref.
The purpose of op amp circuitry is the manipulation of the input signal in some fashion.
Fig(17)Clippper
19 . CLAMPERS
A clamper is an electronic circuit that fixes either the positive or the negative peak excursions of
a signal to a defined value by shifting its DC value. The clamper does not restrict the peak-topeak excursion of the signal, it moves the whole signal up or down so as to place the peaks at the
reference level. A diode clamp (a simple, common type) consists of a diode, which conducts
electric current in only one direction and prevents the signal exceeding the reference value; and a
capacitor which provides a DC offset from the stored charge. The capacitor forms a time constant
with the resistor load which determines the range of frequencies over which the clamper will be
effective.
26
GENERAL FUNCTION
A clamping circuit (also known as a clamper) will bind the upper or lower extreme of a
waveform to a fixed DC voltage level. These circuits are also known as DC voltage restorers.
Clampers can be constructed in both positive and negative polarities. When unbiased, clamping
circuits will fix the voltage lower limit (or upper limit, in the case of negative clampers) to 0
Volts. These circuits clamp a peak of a waveform to a specific DC level compared with a
capacitively coupled signal which swings about its average DC level.
CLAMPING FOR INPUT PROTECTION
Clamping can be used to adapt an input signal to a device that cannot make use of or may be
damaged by the signal range of the original input.
PRINCIPLES OF OPERATION
The schematic of a clamper includes a capacitor, followed by a diode in parallel with the load.
The clamper circuit relies on a change in the capacitor's time constant; this is the result of the
diode changing current path with the changing input voltage. The magnitude of R and C are
chosen so that the time constant, \tau = RC , is large enough to ensure that the voltage across the
capacitor does not discharge significantly during the diode's non-conducting interval. On the
other hand the capacitor is chosen small enough to allow it to charge quickly during the diode's
conducting interval.
During the first negative phase of the AC input voltage, the capacitor in the positive clamper
charges rapidly. As Vin becomes positive, the capacitor serves as a voltage doubler; since it has
stored the equivalent of Vin during the negative cycle, it provides nearly that voltage during the
positive cycle; this essentially doubles the voltage seen by the load. As Vin becomes negative,
the capacitor acts as a battery of the same voltage of Vin. The voltage source and the capacitor
counteract each other, resulting in a net voltage of zero as seen by the load.
BIASED VERSUS NON-BIASED
By using a voltage source and resistor, the clamper can be biased to bind the output voltage to a
different value. The voltage supplied to the potentiometer will be equal to the offset from zero
27
(assuming an ideal diode) in the case of either a positive or negative clamper (the clamper type
will determine the direction of the offset. If a negative voltage is supplied to either positive or
negative, the waveform will cross the x-axis and be bound to a value of this magnitude on the
opposite side. Zener diodes can also be used in place of a voltage source and potentiometer,
hence setting the offset at the Zener voltage.
EXAMPLES
Clamping circuits were common in analog television receivers. These sets have a DC restorer
circuit, which returns the voltage of the signal during the back porch of the line blanking period
to 0 V. Low frequency interference, especially power line hum, induced onto the signal spoils the
rendering of the image, and in extreme cases causes the set to lose synchronization. This
interference can be effectively removed via this method.
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PART B: MINOR PROJECT
1.Introduction
Counter is a sequential circuit. A digital circuit which is used for a counting pulses is known
counter. Counter is the widest application of flip-flops. a counter is a device which stores (and
sometimes displays) the number of times a particular event or process has occurred, often in
relationship to a clock signal. The most common type is a sequential digital logic circuit with an
input line called the "clock" and multiple output lines. The values on the output lines represent a
number in the binary or BCD number system. Each pulse applied to the clock input increments or
decrements the number in the counter.A counter circuit is usually constructed of a number of flipflops connected in cascade. Counters are a very widely-used component in digital circuits, and
are manufactured as separate integrated circuits and also incorporated as parts of larger integrated
circuits.A counter which can be made to count in either the forward or reverse direction is called
an up-down, a reversible or forward-backward counter.
Down Counter
A binary counter with a reverse count is called a binary down counter. In a down counter, the
binary counter is decremented by 1 with every input count pulse. The count of a 4-bit down
counter starts from binary 15 and continues to binary counts 14, 13, 12… 0 and then back to 15.
In a binary down counter, outputs are taken from the complement terminals Q’ of all flip
flops.For a down counter, when Q goes from 0 to 1, Q’ will go from 1 to 0 and complement the
next flip flop.
Up Counter
A binary counter with a normal count is called a binary up counter. In a up counter, the binary
counter is incremented by 1 with every input clock pulse. Outputs are taken drom the normal
output terminal Q of all flip flops. For a up counter when Q goes from 1 to 0, it complements the
next flip flop.
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2. Types of counters – Synchronous Counter & Asynchronous Counter.
Synchronous Counter
In a synchronous counter, the input pulses are applied to all clock pulse inputs of all flip flops
simultaneously (directly). Synchronous counter is also known as parallel sequential circuit. Examples of
Synchronous Counters are as below:
1.Ring Counter
2.Johnson Counter (Switch Tail or Twisted Ring Counter)
Asynchronous Counter
In an asynchronous counter, the flip flop output transition serves as a source for triggering other
flip flops. In other words, the clock pulse inputs of all flip flops, except the first, are triggered not
by the incoming pulses, but rather by the transition that occurs in previous flip flop’s output..
Asynchronous counter is also known as serial sequential circuit. Example of Asynchronous
Counters are as below:
1.Binary Ripple Counter
2.Up Down Counter
Synchronous counters are faster than asynchronous counter because in synchronous counter all
flip flops are clocked simultaneously.
3.Field of project
Digital electronics
Digital electronics are those electronics systems that use a digital signal instead of an analog
signal. Digital electronics are the most common representation of Boolean algebra and are the
basis of all digital circuits for computers, mobile phones, and numerous other consumer
productsThe most common fundamental unit of digital electronics is the logic gate. By combining
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numerous logic gates (from tens to hundreds of thousands) more complex systems can be created. The
complex system of digital electronics is collectively referred to as a digital circuit. To most electronic
engineers, the terms "digital circuit", "digital system" and "logic" are interchangeable in the context of
digital circuits.
Advantage
1.) Digital systems interface well with computers and are easy to control with software. It is often possible
to add new features to a digital system without changing hardware, and to do this remotely, just by
uploading new software. Design errors or bugs can be worked-around with a software upgrade, after the
product is in customer hands.
2.) Information storage can be much easier in digital systems than in analog ones. In particular, the great
noise-immunity of digital systems makes it possible to store data and retrieve it later without degradation.
In an analog system, aging and wear and tear will degrade the information in storage, but in a digital
system, as long as the wear and tear is below a certain level, the information can be recovered perfectly.
Disadvantage
1.) Digital circuits use more energy than analog circuits to accomplish the same calculations and signal
processing tasks, thus producing more heat as well.
2.) Digital systems can be fragile, in that if a single piece of digital data is lost or misinterpreted, the
meaning of large blocks of related data can completely change.
Need and significance of project
Counters are basic building blocks in many digital system with some application requiring
counter that are both fast and long, but speed and size are conflicting because of the carry
propagation from low order to high order. By using logic gates combination and ICs it is possible
to design counter that are long and fast . earlier it was believed that
Count either up or down or up/down. Up only counter have increasing output sequence,while
down only counter have decreasing only sequence while an “up down counter” can channge
“direction” in any clock cycle under the control of a input signal.
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4.Components used and Description
1.) 7 Segment display
2.) IC1 – NE555 Timer
3.) IC2- 74LS192 Decade Counter
4.) IC3- 74LS47 BCD Counter(Binary Coded Decimal)
5.) Resistor – 1k , 10k ,100k ,330 ohm ,560 ohm
6.) Capacitor – 1 microfarad
7.) Switch
8.) 9 volt supply
9.) Copper plate
10.) Connecting wire
7 segment display
even segment displays are LED displays that can show numbers 0 to 9. They are made up of
seven LED "segments" and may also have a extra LED used as a decimal point.The seven
segments are labelled a to g and the decimal point is usually labelled DP. When more than one
seven segment display is used, larger numbers can be displayed.
fig20. 7 segment display
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Seven segment displays usually join all the cathodes or all the anodes of the LEDs in the display
together. When all the cathodes are joined, the display is called a common cathode seven segment
display. When all the anodes are joined, they are called common anode seven segment displays.
NE555 Timer
The NE555 timing circuit is a highly stable controller capable of producing accurate time delays
or oscillation. In the time delay modeof operation, the time is precisely controlled by one external
resistor and capacitor. For a stableoperation as an oscillator, the free running frequency and the
duty cycle are both accuratelycontrolled with two external resistors and onecapacitor. It is called
so because it have 3 resistors connected in series.
Fig21. NE555 timer
It works in two mode ASTABLE & MONOSTABLE mode.
IC1-74LS192
The SN54/74LS192 is an UP/DOWN BCD Decade (8421) Counter. Separate Count Up and
Count Down Clocks are used and in either counting mode the circuits operate synchronously.
The outputs change state synchronous with the LOW-to-HIGH transitions on the clock inputs.
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Fig22.IC
IC3 – 74LS47
It is bcd to 7 segment decoders. The BCD to 7 Segments Decoder is used exclusively for the drive the
display of decimal digits; therefore it is usually called Decoder Driver.
BCD to 7 Segments Decoders are the TTL the 74(LS)47 which drives the common anode
displays and the 74(LS)48 which drives the common cathode displays. CMOS technology
decoder is the CD4511 which drives the common cathode display with latch ability.
fig. 74LS47 pin config
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5.)METHODOLOGY
As soon as the project was assigned ,I commenced with the process of overviewing the research
papers and various websites to finalise the component I need to employ making an UP/DOWN
COUNTER . Various websites were searched .Finally according to the ease of using the
component, availability were finalised.
6.)CIRCUIT DIAGRAM
Fig23.CIRCUIT DESIGN OF 7 SEGMENT UP/DOWN COUNTER
The single digit Up/Down counter consists of a seven segment displays connected to IC-74LS47.
The seven segment display consists of 8 pins and one common pin.
There are mainly two types of seven segment displays 1) common cathode 2) common anode.
The display here used is common Anode display. Generally for common Cathode displays,
common pin should be grounded and for common anode, it should be connected to VCC. In,
Seven segment display, there are seven segments and they are similar to seven LEDs. Seven pins
belong to these seven segments where as the last pin is dot at the coner of the display. For
common cathode, display assigning logic1 to the segment pin glows particular segment. In case
of common anode, the segment pin should be assigned logic0 in order to glow the segment. Each
segment is given one name starting from ‘a ‘and last segment dot is ‘h’.
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Fig24. 7 segment display pin configuration
Fig25 .pin configuration
In our circuit, seven segment display is connected to micro controller through a current limiting
resistor of 330 ohms.
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7.CONNECTION WITH IC
FIG26. Common anode display and it connection with 74LS47
In both these integrated circuits the BCD number bound to be decoded is inserted to the inputs D(6), C(2),
B(1), A(7) where the input D corresponds to the most significant bit (MSB), while the input A
corresponds to the least significant bit (LSB) of the BCD input.When the light test input LT is activated in
LOW, causes the lighting of all the parts a - g.The line BI/RBO functions as an input or an output. It
becomes an output when the input RBI is activated in LOW. When the blackening input BI is activated (in
LOW), the display is blackened, meaning that the outputs become OFF (in the 7447 they become HIGH
and in the 7448 they become LOW). By activating the RBI input (in LOW), the terminal BI/RBO it
changes into a blackening output RBO and is turned into LOW. We remind you that "blanking” means
that none of the lights of the LED display is turned on.Many applications, like the calculators, require
blackening of the primary zeros.
8.WORKING OF PROJECT
555 timer work in astable mode. capacitor is connected to ground through a resistor of some good
value.This is to make the pulse of random length to the 555. The 555 sends its pulses to a BCDcounter (74LS192), which is connected to a BCD-to-seven-decoder (74LS47) which in tur
connected to seven segment display common anode.
We can see BCD counters are binary counters that count from 0000 to 1001 and then resets as it
has ability to clear all of its flip flop after ninth count. If we connect a push button switch(sw1) to
clock input clk a, each time the yhe pushbuttton switch is released the counter will count by one.
Succesive application of pushbuttons will increase the count up to nine,1001. At the tenth
application the output ABCD will reset back to zero to start a new count sequence.
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If we want to display the count sequence using seven segment display, the BCD output needs to
be decoded appropriately before it can be displayed. A digital circuit that can decode the four out
put of our 74LS192 Decade BCD counter and light up th required segment of the display.
BCD TO 7 Segment Driver
The 74LS47 has four input for BCD digits A,B,C,D and output for each of the segment.
The 74LS47 display decoder recieves the BCD code generates the necessary signals to activate
the appropriate LED segment responsible for displaying the numbers of pulses applied. As the
74LS47 decoder is designed for driving a common anode display , a LOW(logic-0) output will
illumnate an LED segment while HIGH(logic-1) output will turn it “off” .
The 74LS BCD inputs can be connected to th corresponding outputs of 74LS192 BCD counter to
display the count sequence on the 7 segment display.
Result
So with the use of some IC a UP/ down counter can be made.
9.Future scope
1. Counters can be used to count moving objects
2. To control Automated parking lot gate
3. Digtal clocks
4. Score Boards
5. In manufacturing companies
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