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ELECTRONICS ENGINEERING
PRACTICE LAB
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LIST OF EXPERIMENTS
1. Study of Electronic Components and Equipments - CRO and
Multimeters.
2. Soldering simple electronics circuits and checking continuity.
3. Assembling electronic components on a small PCB and testing.
4. Study of logic gates.
5. Study of Telephone, FM radio and low-voltage power supplies.
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EX: NO:
DATE: STUDY OF ELECTRONIC COMPONENTS AND EQUIPMENT
Aim:
To study electronic components and equipment such as resistor colour coding,
usage of CRO and Multimeter.
Components Required:
1. Resistors
2. Cathode Ray Oscilloscope
3. Multimeter
Theory:Resistor colour coding:
Resistor colour coding is used to indicate the values or ratings of resistors. It is
also used in capacitors and inductors. The advantage of colour coding is that essential
information can be marked on small components of cylindrical shape without the need to
read tiny printing. Resistor values are always coded in ohms.
Band A is the first significant digit of component value.
Band B is the second significant digit.
Band C is the decimal multiplier.
Band D if present, indicates tolerance of value in percent (no colour means 20%).
For example, a resistor with bands ofyellow, violet, red and gold will have first digit
4(yellow), second digit 7(violet), followed by 2(red) zeros: 4,700 ohms. Gold signifies
that the tolerance is 5%.
Actual resistor value = 4700 5% .
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Resistor Colour Coding:
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Cathode-Ray Oscilloscope:
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that
provides accurate time and amplitude measurements of voltage signals over a wide range of
frequencies. Its reliability, stability, and ease of operation make it suitable as a general
purpose laboratory instrument. We can measure the following parameters using CRO: ACor DC voltage, Time (t)=1/f, Phase relation, Wave form evaluation, rise and fall time; ON
time, OFF time, distortion etc. we can also measure the following parameters non electrical
physical quantities like pressure, strain, temperature, acceleration etc.. by converting into
electrical quantity using transducer.
MAJOR BLOCKS:
Cathode Ray Tube(CRT)
Vertical amplifier
Horizontal amplifier
Sweep generator
Trigger circle
Associated power supply.
CATHODE RAY TUBE(CRT):
The CRT is the heart of CRO. The CRT is enclosed in an evacuated glass envelop
to permit the electron beam to transverse the tube easily. The main functional units of CRT
are as follows
Electron gun assembly Deflection plate unit. Electron gun assembly Screen
ELECTRON GUN ASSEMBLY
The electron gun assembly consists of an indirectly heated cathode and the
necessary heater, control grid, focusing anode and acceleration anode. The time purpose of
an electron gun assembly is to provide a source of electron coverage and focus into a
narrow beam which is acceleration towards the speed. The control grid is at negative
potential which controls the flow of electron towards the screen. Due to the focusing and
accelerating anode, the electrons are repelled away from the cylinder value and therefore
stream through, where they move into the screen electric field of the focusing and
accelerating anodes. The acceleration anode excerts on the electron a force that will depend
on the magnitude and electric field and the magnitude of the charge of the electron.
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After the electron leave the electron gun assembly they enter and pass through the
region controlled by the deflection. One pair of plates control the vertical motion of the
beam. The electron beam is deflected by a force exerted on each electron by the beam that
must be deflected to a considerable distance (eg TV) electrostatic deflection offers the
advantages of higher frequency operations and the fact that deflection plates are mounted
inside the CRT thus saving the space. The other pair controls the horizontal motion of the
beam.
When the electron beam strikes the phosphor coated screen of the CRT, a spot of
light is produced when the electron strikes the ph coated screen.
It absorbs the kinetic energy from the electron and give up the energy in the form of light
(fluorescence). The electrons that strike the screen either repelled by collision or cause
secondary
Emission to provide a written path to ground for these electrons inside surface of CRT
except for the further screen coated with a graphite called AQUADAG.
The beam is deflected upward and to the right by signal applied to the upper
deflection plates that increases linearly with time (RAMP VOLTAGE). This ramp voltage
causes the beam to be deflected equal distance horizontally per unit of time. In the normal
operation the switch is set to internal sweep. When the instrument is used in X-Y mode(
phase measurement). The horizontal amplifier amplifies the signal that is amplified to the
horizontal input terminal and this is amplified by the horizontal amplifier.
BEAM DEFLECTION
The amplitude of the deflection voltages on both the horizontal and verticaldeflected plates determines the position of the beam on the screen.
VERTICAL AMPLIFIER:
The vertical amplifier is the main factor in determining the bandwidth and
sensitivity of an oscilloscope. Vertical sensitivity is a measure of how much the electron
beam will be deflected for a specified input signal on the front panel or the oscilloscope one
can see a knob attached to rotary switch is electrically connected to input attenuation. The
setting of rotary switch indicates what amplitude signal required to deflect the beam
vertically one division.
HORIZONTAL AMPLIFIER
On the normal mode of operation the horizontal amplifier will amplify apply the
sweep generator input. When the CRO is being used in the X-Y mode. The horizontal
amplifier will amplify the signal used to the horizontal input terminal. Although the vertical
amplifier must be able to faithfully reproduce low amplitude high frequency signals with
fast rise time. The horizontal amplifier is only required to provide a faithful reproducing of
the sweep signal which has a relatively high amplitude and low rise time.
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SWEEP GENERATOR
If the wave form is to be accurately reproduced the beam must have constant
horizontal velocity since the beam velocity is a function of the deflecting voltage,
deflecting voltage must increase linearly with time. A voltage with this characteristic is
called ramp voltage.
During rise time of the sweep voltage, the beam moves from left to right across the
CRT screen. The beam is deflected to the right by increasing the amplitude to the ramp
voltage and the fact that the positive voltage attracts the negative electron. During the
return or fall time the beam return to the left side of the screen to prevent undesirable
retrace pattern. From appearing on the screen during retrace the control grid is generally
GATED OFF which blanks out the beam during replace. Figure 2. gives the sweep
generator waveform.
SIGNAL SYNCHRONIZATION
Signals are synchronized. If the vertical input frequency is not exactly equal to or an
exact multiple of the saw tooth. The wave form will not be synchronized and the display
runs across the screen. If the pattern moves towards the right the frequency of the saw tooth
curve is too low when both the signal are at the same frequency and internal synchronize
pulse will lock the sweep generator into the vertical input (frequency and amplitude). These
limitations are overcome by the incorporation of a trigger circuit onto the oscilloscope. The
trigger circuit may receive input from one of the three sources depending on the switch
setting. The input signal may come from an external source when the trigger select a switch
is set to EXT or from low amplitude AC voltage at line frequency when the switch is said
to be line or from the vertical amplifier. When the switch is set from internal triggering the
trigger circuit receives its input from the vertical amplifier.
BLOCK DIAGRAM OF CATHODE RAY OSCILLOSCOPE:
DUAL TRACE OSCILLOSCOPE:
It has vertical input channel and the electronic switch that alternatively connects the
two input channels to the vertical amplifier they are generally minimum for four modes of
operations. They are A,B alternate and chopped. When set A or B only input at that
channels A or B is displayed on the alternate mode. The inputs displayed in alternate isgenerally preferred when displayed relatively high frequency signal. The switching rate is
synchronized with the sweep generator.
In the chopped mode electronic switch occurs at a rate completely independent of
the sweep rate and therefore each display has portions missing during each time the other
signal is being displayed. The chopped mode is normally used at low sweep rate when the
alternate mode would provide display with appreciate fixer. Block diagram of a typical
oscilloscope given in Figure 3.
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Setting the controls of Oscilloscope:
After plugging in the oscilloscope, take a look at the front panel. It is divided into threemain sections labeled Vertical, Horizontal, and Trigger. Your oscilloscope may have other
sections, depending on the model and type (analog or digital).
Notice the input connectors on your oscilloscope. This is where you attach probes. Most
oscilloscopes have at least two input channels and each channel can display a waveform onthe screen. Multiple channels are handy for comparing waveforms.
Ground the Oscilloscope:
Proper grounding is an important step when setting up to take measurements or work on a
circuit. Properly grounding the oscilloscope protects you from a hazardous shock andgrounding yourself protects your circuits from damage. Grounding the oscilloscope is
necessary for safety. If a high voltage contacts the case of an ungrounded oscilloscope, any
part of the case, including knobs that appear insulated, it can give you a shock. However,
with a properly grounded oscilloscope, the current travels through the grounding path to
earth ground rather than through you to earth ground.
To ground the oscilloscope means to connect it to an electrically neutral reference point
(such as earth ground). Ground your oscilloscope by plugging its three-pronged power cord
into an outlet grounded to earth ground. Grounding is also necessary for taking accurate
measurements with your oscilloscope. The oscilloscope needs to share the same ground asany circuits you are testing.
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Vertical Controls:
Use the vertical controls to position and scale the waveform vertically. Following Figure
shows a typical front panel and on-screen menus for the vertical controls.
Horizontal Controls:
Use the horizontal controls to position and scale the waveform horizontally. Following
Figure shows a typical front panel and on-screen menus for the horizontal controls.
Trigger Position:
The trigger position control may be located in the horizontal control section of youroscilloscope. It actually represents "the horizontal position of the trigger in the waveformrecord.
Standard positions include the following:
Set the oscilloscope to display channel 1 Set the volts/division scale to a mid-range position
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Turn off the variable volts/division Turn off all magnification settings Set the channel 1 input coupling to DC Set the trigger mode to auto Set the trigger source to channel 1 Turn trigger hold off to minimum or off Set the intensity control to a nominal viewing level Adjust the focus control for a sharp display
Procedure to take measurements using the Oscilloscope:
The oscilloscope can take automatic measurements of most displayed signal. To
measure signal frequency, period, and peak-to-peak amplitude, do the following steps:
Connect the output of the function generator to CH1 of the oscilloscope.Turn on the power switch of the function generator.Select the Sine wave button of the function generator and set the input to 1000Hz, 200 mV P-PTurn on the power switch of the oscilloscope.Waveform Measurements in Oscilloscope:
1. Frequency and PeriodIf a signal repeats, it has a frequency. The frequency is measured in Hertz (Hz) and equalsthe number of times the signal repeats itself in one second (the cycles per second). A
repeating signal also has a period - this is the amount of time it takes the signal to complete
one cycle. Period and frequency are reciprocals of each other, so that 1/period equals the
frequency and 1/frequency equals the period. So, for example, the sine wave in followingfigure has a frequency of 3 Hz and a period of 1/3 second.
Frequency and Period
2. VoltageVoltage is the amount of electric potential (a kind of signal strength) between two points ina circuit. Usually one of these points is ground (zero volts) but not always - you may want
to measure the voltage from the maximum peak to the minimum peak of a waveform,
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referred to at the peak-to-peak voltage. The word amplitude commonly refers to the
maximum voltage of a signal measured from ground or zero volts.
3. PhasePhase is best explained by looking at a sine wave. Sine waves are based on circular motionand a circle has 360 degrees. One cycle of a sine wave has 360 degrees, as shown infollowing figure.
Multimeter:
A multimeter is a device used to measure voltage, resistance and current in
electronics & electrical equipment. It is also used to test continuity between to 2 points to
verify if there are any breaks in a circuit or line. The most basic instruments include
ammeter, voltmeter, and ohmmeter. Analog multimeters are sometimes referred to as
volt-ohmmeters, abbreviated as VOM. A multimeter is a handheld device and used
to find basic fault and for field service work. It can measure to seven or eight and
a half digit of accuracy. Current, voltage and resistance measurements are considered
standard features for multimeter.
A multimeter may be implemented with an analog meter deflected by an
electromagnet, as a classic galvanometer; or with a digital display such as an LCD or
vacuum fluorescent display. Modern multimeters are, exclusively digital and identified
by the term DMM or digital multimeter. In such an instrument, the signal under test is
converted to a digital voltage and an amplifier with an electronically controlled gain
preconditions the signal. Since the digital display directly indicates a quantity as a
number, there is no risk of error when viewing a reading. Similarly, better circuitry and
electronics have improved the meter accuracy. Older analog meters might have basic
accuracies of 5%. Modern potable DMMs have accuracies as good as 0.025%.
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Common DMM Symbols:
Multimeter Leads:
RedMeter Lead is connected to voltage/Resistance or Amperage port and are consideredthe positive connection.
The Probes are the handles used to hold tip on the connection being tested. The Tips are at
the end of the probe and provides a connection point.
Black Meter Lead is connected to the common/ground port and is considered the negative
connection.
Fig. Multimeter and Probes Diagram
Digital Display shows
measured value.
Meter Dial used to change
the functions
Panel Indicator shows
each function and setting
range
Probe Connections
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Measuring Voltage:
Voltage (V) is the unit of electrical pressure; one volt is the potential differenceneeded to cause one amp of current to pass through one ohm of resistance
Voltage is broke up into 2 sections AC & DC Alternating Current (AC) is housevoltage (110vac) Direct Current (DC) is battery voltage (12vdc)
On switched meters use one value higher than your expected value Be very careful to not touch any other electronic components within the equipment
and do not touch the tips to each other while connected to anything else.
To measure voltage connect the leads in parallel between the two points where themeasurement is to be made. The multimeter provides a parallel pathway so it needs
to be of a high resistance to allow as little current flow through it as possible.
Fig. Measuring Voltage
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Measuring Resistance and Continuity:
Resistance () is the opposition to current Resistance is measured in Ohm's Disconnect power source before testing Remove component or part from system before testing Measure using lowest value, if OL move to next level Testing for continuity is used to test to verify if a circuit, wire or fuse is complete
with no open
Audible continuity allows an alarm if circuit is complete If there is no audible alarm, a resistance reading of .1 ohm to 1 ohm should be
present
Fig. Measuring Resistance
Fig. Measuring or Testing Continuity
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Measuring Current:
Current (amps) is the flow of electrical charge though a component or
conductor
Current is measured in amps or amperes
Disconnect power source before testing
Disconnect completed circuit at end of circuit
Place multimeter in series with circuit
Reconnect power source and turn ON
Select highest current setting and work your way down.
Fig. Measuring Current
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Oscilloscope:
Input to the CRO:
Output in CRO:
Model Graph:
Multimeter:
Result:
Thus the resistor colour coding, usage of CRO and multimeter are studied.
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STUDY AND VERIFICATION OF LOGIC GATES
The Breadboard:
The breadboard consists of two terminal strips and two bus strips (often broken in the
centre). Each bus strip has two rows of contacts. Each of the two rows of contacts are anode. That is, each contact along a row on a bus strip is connected together (inside the
breadboard). Bus strips are used primarily for power supply connections, but are also used
for any node requiring a large number of connections. Each terminal strip has 60 rows and
5 columns of contacts on each side of the centre gap. Each row of 5 contacts is a node.
You will build your circuits on the terminal strips by inserting the leads of circuit
components into the contact receptacles and making connections with 22-26 gauge wire.
There are wire cutter/strippers and a spool of wire in the lab. It is a good practice to wire
+5V and 0V power supply connections to separate bus strips.
Fig 1. The breadboard. The lines indicate connected holes.
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OR Gate: (IC 7432)
Pin Configurations
Logic Symbol
Truth table
Circuit
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AND Gate: (IC 7408)
Pin Configurations:
Logic Symbol
Truth Table
Circuit
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NOT Gate: (IC 7404)
Pin Configurations
Logic Symbol
Truth table
Circuit
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NOR Gate: (IC 7402)
Pin Configurations
Logic symbol
Truth table
Circuit
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NAND Gate: (IC 7400)
Pin Configurations:
Logic Symbol
Truth table
Circuit
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Ex-OR Gate: (IC 7486)
Pin Configurations
Logic Symbol
Truth table
Circuit
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EX: NO: STUDY AND VERIFICATION OF LOGIC GATES
DATE:
Aim:
To verify the truth table of the logic gates AND, OR, NOT, NAND, NOR & Ex- ORusing 74XX ICs.
Components Required:
S.NO COMPONENTS TYPE/RANGE QUANTITY
1 AND GATE IC7408 1
2 OR GATE IC7432 1
3 NOT GATE IC7404 1
4 NOR GATE IC7402 1
5 NAND GATE IC7400 1
6 Ex-OR GATE IC 7486 1
7 RESISTOR 330 OHMS 1
8 LED 1
9 Bread board 1
10 Power Supply 5V 1
Theory:
Logic gates are digital circuits with one or more input signals and only one output
signal. Gates are digital circuits because the input and output signals are either low or
high voltages. Gates are often called logic circuits because they can be analysed using
Boolean algebra.
AND Gate: (IC 7408)
An AND gate can have two or more inputs but only one output. Its output can go to
logic 1 if all its inputs are at the high state.
The Boolean expression for a two input AND gate is: F=x.y
OR Gate: (IC 7432)
An OR gate can have two or more inputs but only one output. Its output will be at
logic 1 if any or both of its inputs are at the high state.
The Boolean expression for a two input OR gate is: F = x+y
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NOT Gate: (IC 7404)
A NOT gate has a single input and a single output. It is also called as an inverter. The
output will be at logic 1 if its input is at low state, otherwise its output will be at logic 0.
Thus its output is the complement of its input. The Boolean expression for a NOT Gate is
F= x.
NAND Gate: (IC 7400)
It is the combination of AND gate and NOT gate. It is also called as an universal
gate. The output of this gate will go to logic 0 iff all its inputs are at the high state.
The Boolean expression for a two input NAND gate is F = (x.y)
NOR Gate: (IC 7402)
It is the combination of an OR gate and a NOT gate. It is also called as an universal
gate. The output of this gate will go to logic 1 iff all its inputs are at the low state.
The Boolean expression for a two input NOR gate is:
F = (x + y)
Ex-OR Gate: (IC 7486)
The Ex-OR (exclusive-OR) gate acts in the same way as the logical either/or. The
output is true if either , but not both, of the inputs are true. The output is false if both
inputs are false or if the both the inputs are true. The Boolean function is F=x y.
Procedure:
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1. Connections are given as per the logic diagrams and the pin-out diagrams of
the individual ICs.
2. Supply and ground connections are given to the ICs.
3. Inputs are applied by using the switches that provide the logic High and
Low levels.
4. The outputs are observed by using the LEDs.
Result:
Thus the logic gates AND, OR, NOT, NAND and NOR are studied and their truth
tables verified.
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EX: NO: SOLDERING AND CHECKING CONTINUITY
DATE:
Aim:
To practice soldering of plates and wires and checking the continuity.
Tools Required:
1. Soldering iron2. Solder3. Flux4. PCB
Theory:
Soldering:
Soldering is the process of joining thin metal plates or wires made of steel, copper
or brass. It is very commonly used to join wires in electrical work and mount electronic
components on a circuit board. The joining material used in soldering is called as solder
or filler rod. An alloy of tin and lead is commonly used as the solder. The flux is used to
clean the surface of the plates/wires to be soldered. Aluminium chloride or zinc chloride
is commonly used as flux. A good soldering iron is a variable temperature setting type
with interchangeable irons and tips. The tip should be removed regularly to prevent
oxidation scale from accumulating between the heating element and the tip.
Procedure:
1. The surface to be soldered is cleaned and flux applied.
2. The soldering iron is heated to the required temperature.
3. The soldering iron melts the solder rod and a thin film of solder spreads over
the surface to join the plates/wires.
Soldering Simple Electronic Components:
A printed circuit board (PCB) consists of copper strips and pads bonded to a
plastic board. The copper strip is the network of interconnecting conductive path. Leads
of components mounted on the board are inserted through holes on the board and the
conductive copper. These leads are soldered to the copper at the end of the hole. If
excessive heat is applied to copper, it may get lifted from the board or the components on
the board get damaged. Soldering pencil gun of about 30 Watts is used to heat the
junction. The surface of copper bonded to the board should be properly prepared and
cleaned before soldering. Flux is applied on circuits and component leads.
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Check the conductive strips and pads on the board before soldering. Avoid excess
solder to prevent two copper paths from bridging. When solder globules form on the
junction area, remove them by cleaning the soldering tip using a cloth.
Checking Continuity:The continuity of a wire conductor without a break has practically zero ohms of
resistance. Therefore, an ohmmeter may be used to test continuity. To test continuity,
select the lowest ohm range. A wire may have an internal break, which is not visible due
to insulation, or the wire may have a bad connection at the terminals. Checking for zero
ohms between any two points tests the continuity. A break in the conducting path is
evident from the reading of infinite resistance.
In a cable of wires, individual wires are identified with colours. Consider the
figure, where the individual wires are not seen, but you wish to find the wire that
connects to terminal A. This is done by, checking continuity of each wire to terminal A.
The wire that has zero ohms is the one connected to this terminal. Continuity of a long
cable may be tested by temporarily short-circuiting the other ends of the wires. The
continuity of both wires may be checked for zero ohms.
In a digital multimeter, a beep mode is available to check continuity. The
connectivity between the terminals is identified by the beep sound.
Result:
The electronic components are soldered and continuity of a circuit or wire is
checked.
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Electronic Components
Resistor Capacitor
PN Diode
Transistor
Integrated Circuit (IC)
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EX: NO: ASSEMBLING ELECTRONIC COMPONENTS ON
DATE: A PCB AND TESTING
Aim:
To assemble electronic components on a PCB and test it
Tools Required:
1. Soldering iron
2. Solder and
3. Flux
Components Required:
1. PCB and
2. Electronic Components
Procedure:
The electronic components are carefully assembled as per the circuit design. The
assembling of electronic components on a PCB involves the following steps.
Component Lead Preparation:
Components such as capacitors have leads and are bent carefully to mount on
PCB. The lead bending radius should be approximately two times the diameter of the
lead. The bent leads should fit into the holes perpendicular to the board, so that the stress
on the component lead junction is minimized. Suitable bending tools may be used for
perfect bending. Leads are bent and assembled on board in such a way that the polarity
symbols are seen after mounting the component.
Component Mounting:
Components are mounted on one side of the board and leads are soldered on the
other side of the board. The components are oriented both horizontally and vertically but
uniformity in reading directions must be maintained. The uniformity in orientation of
diodes, capacitors, transistors, ICs etc. is determined at the time of PCB design.
Components dissipating more heat should be separated from the board surface.
Manual Assembly of Components:
The components to be assembled on a PCB are arranged conveniently. The board
to be assembled is held in a suitable frame and the components are kept in trays or bins.
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The insertion tools, if required, must be kept in the easy reach of the worker. The work is
divided depending on number of parts to be assembled and the size of each part. The
number of different components to be assembled for one worker should not be more than
20.
Inspection and Testing:
The components assembled on the PCB are tested before they are soldered to the
board. It is a common practice to have the assembled boards checked prior to soldering.
An assembly inspector is located at the end of the assembly line for inspection. The
inspection includes verifying component polarity, orientation, value and physical
mounting.
Soldering and Lead Cutting:
The components are soldered on the PCB. The excess lead is cut after soldering.
The performance and reliability of the solder joints are best if lead cutting is carried
before soldering so that the lead end gets protected. However, this is not practiced in
hand soldering.
PCB Cleaning:
The soldered PCB may have contaminants that could cause trouble during the
functioning of the circuit. The contaminants include flux and chips of plastics, metals,and other materials. Hence, the PCB must be cleaned before use. A wide range of
cleaning media is available; usually chemicals such as acetone and alcohols are used.
Result:
The electronic components are assembled on PCB and are tested.
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Half Adder:
Truth Table for Half Adder:
Addend
(A)
Augend
(B)
Sum
(S)
Carry
(C)
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
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ADDITIONAL EXPERIMENT
EX: NO: HALF ADDER & FULL ADDER
DATE:
Aim:
To design and construct a half adder and a full adder using suitable logic gates and to
verify their truth table
Components Required:
IC 7432(OR Gate)
IC 7408(AND Gate)IC 7486(EX-OR Gate)
Digital IC trainer kit
Theory:
Half Adder
A Combinational circuit that performs the addition of two binary digits is called a
half adder. When two single bit data are added, the result can have a maximum of two
bits i.e. the sum bit and a carry bit. Thus this circuit needs two binary inputs and two
outputs. The inputs are designated as addend and augend.
The Boolean expression for sum and carry are:
Sum, S = AB + AB
S = ABCarry, C = A.B
where A & B are the input variables and S & C are the output variables. Thus to get theoutput sum an XOR gate is used. To get the output carry an AND gate is used.
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Full Adder
A
B
Cin
13
2 IC 7486
1
46
5IC 7486
3
S=ABCin
2 IC 7408
46
5 IC 7408
13
2 IC 7432
Cout = AB+ACin+BCin
Truth Table for Full Adder
Addend
(A)
Augend
(B)
Carry-in
(Cin)
Sum
(S)
Carry- out
(Cout)
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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