engineering practices lab manual

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STUDY OF ACCESSORIES, TOOLS USED IN WIRING &

SAFETY PRECAUTIONS

AIM:

To study the various types of accessories and tools used in house wiring. To study safety precautions for electrical engineering practice

ACCESSORIES REQUIRED:

Switch, Lamp Holder, Lamp holder adopter, Ceiling roses, Mounting blocks, Socket outlets, Plugs, Main switch, Distribution fuses boards.

TOOLS REQUIRED:

Cutting pliers, Flat nose pliers, Screwdriver, Neon tester, Hammer, knife, Poker, Pincer, Center punch, twist drill, Soldering rod. ACCESSORIES:

1. Switch

A switch is used to make or break an electric circuit. Under some abnormal conditions it must retain its rigidity and keep its alignment between switchblades and contacts correct to a fraction of centimeter.

2. Lamp Holders

A lamp holder is used to hold the lamp required for lighting purposes.

3. Lamp Holder Adopter

It is used for tapping temporary power for small portable electric appliances from lamp holders. Such a practice is not advised.

4. Ceiling Roses

It is an end point of an electrical wire, which provides a cover to the wire end. These are used to provide a tapping to the lamp holder through the flexible wire or a connection to a fluorescent tube or a ceiling fan. It consists of a circular base and a cover made of bakelite. One end of the plates is connected to supply and the other end to a flexible wire connected to appliances. 5. Mounting Blocks

These are nothing but wooden round blocks. They are used in conjunction with ceiling roses, batten holder, surface switches, ceiling switches, etc.

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6. Socket Outlets

It is a wiring accessory to which electrical appliances are connected for power supply. These have insulated base with molded or socket base having three terminal sleeves. The two thin terminal sleeves are meant for making connection to the load circuit wires and the third terminal sleeve, larger in cross section, is used for an earth connection.

7. Plugs

These are used for tapping power from socket outlets. Two-pin plugs and three-pin plugs are commonly available.

8. Main Switch

This is used at the consumer’s premises so that he may have self-control of the entire distribution circuit. This switch is a master control of all the wiring circuit made in the building. The different classifications are double poled and triple poled switches.

9. Distribution Fuse Boards

In industries or in very big buildings, where a number of circuits are to be wired, distribution fuse boards are used. They are usually iron clad and are designed with a large space for wiring and splitting the circuits. The fuse bank in the distribution board can easily be removed.

10. Fuse

A fuse is a protective device, which is connected such that the current flowing through the protected circuit also flows through the fuse. There is a resistive link inside the fuse body that heats or melts up when current flows through it. If the current is beyond the permissible limit, the resistive link burns open, which stops all current to flow in the circuit. At this condition we say that the fuse is blown.

11. Earthing When a wire is connected from the ground to the outer metal casing of the electrical appliances, then it attain zero potential and the appliance is said to be earthed and this process is known as earthing.

12. Purpose of Earthing

Under normal condition, there is no electrical potential is available in the outer metal casing of the electrical appliances. When some fault develops in the appliances, then electrical potential leaked to the metal casing causes heavy current flow due to earthing. This heavy current blows the fuse and cutoff electrical supply to the appliances. Thus earthing provides protection to human being and electrical appliances.

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TOOLS:

1. Cutting Pliers

They are used to cut the wires, nipping by hand and twisting the wires and also to hold them. Long nose pliers are used to hold the wires in small space and also to tighten and loosen small nuts.

2. Nose Pliers

Long nose pliers are used to hold the wires in small space and also to tighten and loosen small nuts.

3. Screw Driver

They are used to drive and tighten screws into pointed holes in the switches and electrical machines. They are generally insulated.

4. Hammer

Ball peen and claw hammers are commonly used in electrical work where greater power is required in striking. It is best suited for riveting purposes in sheet metal works.

5. Line Tester

It is used to check the electric supply in the line or phase wire. It has a small neon bulb, which indicates the presence of power supply. It can also be used as a screw driver.

6. Knife

It is generally used for removing the insulation from the wire. The closing type knife is always preferred.

7. Poker

It is a long sharp tool used for making pilot holes in wood before fixing and tightening wood screws.

8. Pincer The pincer is used for extracting nails from the wood. 9. Center Punch

When a hole is to be drilled in a material, the center punch is always used for making the starting hole.

10. Twist Drill

It is used for drilling holes into metals and woods.

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11. Soldering Rod

It is used for soldering wires to small joints with solder. It consists of pointed oval Cu bit fixed to an iron rod, which is heated by an electric element only.

SAFETY PRECAUTIONS:

1. While work on electrical installations, wear always rubber shoes and avoid loose shirting.

2. Do not work on live circuits, if unavoidable use rubber gloves, rubber mats etc

3. Use wooden or PVC insulated handle screwdrivers when working

on electric circuits.

4. Do not touch bare conductors

5. Replace or remove fuses only after switching OFF the circuit

switches.

6. Never extend wiring by using temporary wiring.

7. Stand or rubber mats while working or operating switch panels,

control gears etc.

8. Always use safety belts while working on poles or high rise points.

9. Do not connect earthing to the water pipe lines.

10. Only skilled persons should do electric work.

11. Wear all the protective clothing and use all the necessary safety

equipment.

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12. In case of any person suffered by electrical shook and if the victim

is still in contact with the supply, break the contact either by switching off or by removing the plug or pulling the cable free.

13. Do not give an unconscious person anything to eat or drink and do

not leave an unconscious person unattended.

14. First restore the normal breathing to the victim and ensure that the patient can breathe normally unaided. Then we can render other first aids.

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RESULT:

Thus a study on the various types of accessories, tools used in house wiring and safety precautions for electrical engineering practice was performed.

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CIRCUIT DIAGRAM:

Layout Diagram:

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EXPERIMENT No: DATE:-

RESIDENTIAL HOUSE WIRING USING SWITCHES, FUSE,

INDICATOR, LAMP AND ENERGY METER.

AIM:

To construct residential house wiring using switches, fuse, indicator, lamp and energy meter.

MATERIALS REQUIRED:

S.No Components Description Quantity

1 Lamps loads 5A 3

2 Bulb holder 3 3 Fuses 3 4 One way switches 3 5 Wires required

TOOLS REQUIRED:

S.No Components Quantity

1 Plier 1

2 Knife 1 3 Side cutter 1 4 Screw driver 1

PROCEDURE:

• Collect the materials required for this experiment.

• Draw the layout of the given circuit diagram in the circuit board.

• Fix the necessary materials, by using drilling machine in the layout board.

• The lamps are fixed on the lamp holders.

• Connections are checked and supply is given.

• Switches are operated to see the output of the lamp.

PRECAUTIONS:

• The metal covering of all appliances are to be properly earthed in order to avoid electrical shock due to leakage or failure of insulation.

• Every line has to be protected by a fuse of suitable rating as per the requirement.

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Fuse rating calculations:

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RESULT:

Thus the single-phase wiring has been constructed, tested and the results are tabulated.

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FLUORESCENT TUBE WIRING

CIRCUIT DIAGRAM:


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FLUORESCENT LAMP WIRING

AIM:

To construct a Fluorescent tube wiring.

MATERIALS REQUIRED:


1 Tube light 1

2 Choke 1

3 Starter 1 4 Connecting wires 5 Screws and nuts

TOOLS REQUIRED:


1 Plier 1 2 Knife 1

3 Side cutter 1 4 Screw driver 1

THEORY:

The fluorescent tubes are available in lengths of 0.61m and 1.22m.The tubes are coated from inside with phosphorous, which is used to convert ultra violet radiations into visible light and to give the required colour sensation. A choke is used to give a transient high voltage so as to initiate the electron movement. With the switch S closed, the circuit gets closed. The current flows through the choke and the starter. The starter suddenly breaks thereby breaking the circuit. Due to high inductive property of the choke, a transient high voltage is available across the filaments. Hence electrons are emitted and travel through the tube. Such a continuous flow of electrons produces the sensation of light to human eyes.

PROCEDURE:

• The tube light wiring is made as per the wiring diagram.

• Supply is given and circuit is checked.

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RESULT:

Thus the fluorescent tube wiring has been constructed and the working is tested.

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STAIRCASE WIRING

CIRCUIT DIAGRAM:


Power drawn by the circuit =40 watts Voltage of circuit =230volts P=VI cos Ø Assuming cos Ø = 1 Current in the circuit = power/ voltage = 40W/ 230V = 0.174A Fuse rating of the circuit = rounding off the current to the nearest 5 =5A (Normally fuses are available in the ratings of 5A, 10A and etc.)

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STAIRCASE WIRING AIM:

To setup a staircase wiring using the given lamps, controlled by switches.

MATERIALS REQUIRED:


1 PVC pipes

2 Junction boxes 1 3 Bulb holder 1

4 PVC plates 1 5 Drilling machine 1 6 Wires 7 Two-way switch 2

TOOLS REQUIRED:


1 Neon tester 1 2 cutting pliers 1 3 Screwdriver 1

THEORY: In this wiring a single lamp is controlled from two places. For this purpose

two numbers of two-way switches are used.

PROCEDURE:


• Draw the layout of the given circuit diagram in the circuit board.

• Fix the necessary materials, by using drilling machine in the layout board.

• One end of the lamp holder is connected to neutral point and another point is connected at the center of the two-way switch B.

• The center of the switch A is connected to the phase line.

• The connection of the other two ends of two-way switch is connected as follows. The point 1 of switch A is connected to point 1 of switch B and point 2 of A is connected to 2 of B.

• The given lamp is fixed on the lamp holders.

• Controlling the switches, the circuit is checked and results are tabulated.

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LAYOUT DIAGRAM:

Sl.no Switch A Switch B Output-Lamp

1 1 2 OFF

2

3

4

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RESULT:

Thus the staircase wiring has been constructed, tested and the results are tabulated

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CIRCUIT DIAGRAM:

RLC Circuit

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MEASUREMENT OF ELECTRICAL QUANTITIES – VOLTAGE,

CURRENT, POWER & POWER FACTOR IN RLC CIRCUIT.

AIM:

To measure real power, reactive power, power factor and impedance RLC

circuit using voltmeter and ammeter

MATERIALS REQUIRED:

S.No Name of the Equipment Range Type Quantit

y

1 Auto transformer 1φ 1 1 2 Rheostat 200 Ω, 150 Ω 300/2A 1

3 DCB 10uf, 4uf UPF 2 4 DIB 1 H 1 5 Voltmeter (0-150) V 6 Ammeter (0-200) mA 1

7 Connecting wires

PROCEDURE:

• Connect the RLC circuit as shown in circuit diagram.

• After verification of circuit close the DPST switch.

• Precaution set the auto transformer to minimum position.

• Vary the auto transformer such that 200 mA of current flows through ammeter.

• Note down drop across R, R-L and C also current in the circuit.

• Readings are tabulated.

• Bring the auto transformer to original position before opening DPSTS. Calculate power factor (cos), impedance (Z), real power (P), reactive power (Q), and total power(S).

CALCULATION:

V1 = Supply voltage = IZ in volts VC = Drop across capacitor = IX C in volts VR = Drop across resistor = IR in volts VL = Drop across inductor = IX L in volts V = Drop across R, L &C =

I2

C

2 )X()( −++ LXrR in volts

I= V/Z in Amps –Current through RLC network

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1. XC = 1 / 2π fc in ohms 2. Powe rfactor Cosφ = R/ Z (p.f.)

3. Impedance Z= 2

C

2 )X()( −++ LXrR

4. Real power P = I 2(R + r) in Watts

5. Reactive power = I 2[ XL − XC ] in VAR

6. Total power S = P + jQ = 22 Q( +P in VA

7. Impedance Z=V/I in ohms 8. Real Power P= VI Cosφ in Watts

9. Reactive Power Q = VI Sinφ in VAR

10. Total power S = P + jQ = 22 Q( +P

11 Powerfactor Cosφ = (VR + Vr)/V

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RESULT:

The voltage, current, power and power factor of the series RLC circuit are

determined

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CIRCUIT DIAGRAM:

PHASOR DIAGRAM:

D

A B C

V

V

IXL – IXC

V Vr

β

θ

φ

~ 24~


MEASUREMENT OF ENERGY USING SINGLE PHASE ENERGY

METER. AIM:

To measure the energy using single phase energy meter at UPF load

condition APPARATUS REQUIRED:

S.No Name of the Equipment Range Type Quantity

1 Voltmeter (0 – 300) V M.I. 1 2 Ammeter (0 – 5) A M.I. 1

3 Wattmeter 300V, 5A UPF 2

4 1 Φ Variable resistive load kW 1 5 Connecting wires 6 Stop clock 1

PRECAUTIONS:

• There should be no load at the time of starting.

• The connections must be made proper for UPF.

PROCEDURE:

• The connections are made as per the circuit diagram.

• The DPST switch is closed and the supply is affected and load is adjusted to full load value.

• The time taken for 10 revolutions of the aluminum disc in the energy meter is noted.

• The error is calculated if it is more than +3% the brake magnet is adjusted such that the error is within +3%.

• The load is reduced in steps and for each step, step #. 3 is repeated and the %error is calculated.

FORMULAE USED:

• Energy meter specification = 1200 rev/Kwhr

• = 1 Kwhr

• 1rev = 1Kwhr/1200 = (3600 * 100) / 1200 = 3000 Watt – sec

• For UPF conditions, Power calculated from energy meter reading = 3000 / (time taken for 10

rev)

• %Error =(Power calculated from energy meter reading – wattmeter reading) /(Wattmeter reading) * 100

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TABULAR COLUMN:

S.No. Ammeter

reading

(A)

Time for 10

revolutions

(Sec)

Wattmeter reading

(W)

Power from

Energy

meter

(W)

% Error

(%)

Observed

value

Actual value

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RESULT:

Thus the energy is measured using single phase energy meter and the %error is calculated.

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BLOCK DIAGRAM

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MEASUREMENT OF RESISTANCE TO EARTH OF AN ELECTRICAL

EQUIPMENT

AIM:

To measure the earth resistance using megger.

MATERIALS REQUIRED:


1 Megger 1

2 Rod 2

TOOLS REQUIRED:


1 Connecting Wires 1 2 Hammer 1

THEORY:

Earthing means generally connected to the mass of the earth. It shall be in such a means as to ensure at all times an immediate & safe discharge of electric current due to leakage, fault etc. All metallic parts of every electrical insulation such as conduit, metallic sheathing, metallic panels, motor, gear, Transformer regulator shall be earthed using continuous bus wire if one earth bus for installation is found impracticable move than one earthing system shall be introduced the earthing conductors when taken outdoors to the earthing point, shall be incased in pipe securely supported and continued upto point not less than 0.3m below the ground. No joints are permitted in earth bus whenever there is lighting conductors system installed in a building. Its earthing shall not be bonded to the earthing of electric installation. Before the electric supply on apparatus is energized all earthing system shall be tested for electrical resistance to ensure efficient earthing. It shall not be more than 2ohms including the ohmic value of earth electrode.

PROCEDURE:


• The terminal of ohmmeter E is first connected to earth.

• The two earth rods are fixed to feet away from the ohmmeter. So that they are triangle with base 50 feet.

• The wires are connected to each rod and the ohmmeter terminals are shown.

• The ohmmeter is ranked and the readings are taken.

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CIRCUIT DIAGRAM :

1. CURRENT ELECTRODE 2. POTENTIAL ELECTRODE 3. EARTH

TABULAR COLUMN:

S.No Distance Between Electrode(Feet) Resistance(Ohms)

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RESULT:

The earth resistance was measured in the given area.

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EX: NO: STUDY OF ELECTRONIC COMPONENTS AND

DATE: EQUIPMENT

Aim:

To study electronic components and equipment such as resistor colour coding,

usage of CRO and Multimeter

Components Required:

1. Resistors

2. 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 of yellow, 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% Ω.

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Resistor Colour Coding:

Resistor Standard Colour Code Table

Colour Value Digit Multiplier Tolerance

Black 0 x100

Brown 1 x101 ±1%

Red 2 x102 ±2%

Orange 3 x103

Yellow 4 x104

Green 5 x105 ±0.5%

Blue 6 x106 ±0.25%

Violet 7 x107 ±0.1%

Grey 8 x108 ±0.05%

White 9 x109

Gold x10-1 ±5%

Silver x10-2 ±10%

None ±20%

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Oscilloscope:

An oscilloscope (sometimes abbreviated CRO for cathode-ray oscilloscope) is

electronic test equipment that allows signal voltages to be viewed, usually as a two-

dimensional graph of one or more electrical potential differences (vertical axis) plotted as

a function of time or some other voltage (horizontal axis).

A typical oscilloscope is a rectangular box with a small screen, numerous input

connectors and control knobs and buttons on the front panel. To aid measurement, a grid

called the graticule is drawn on the face of the screen. Each square in the graticule is

known as a division. The signal to be measured is fed to one of the input connectors,

which is usually a coaxial connector such as a BNC or N type.

In the simplest mode, the oscilloscope repeatedly draws a horizontal line called

the trace across the middle of the screen from left to right. One of the controls, the time

base control, sets the speed at which the line is drawn, and is calibrated in seconds per

division. If the input voltage departs from zero, the trace is deflected either upwards or

downwards. Another control, the vertical control, sets the scale of the vertical deflection,

and is calibrated in volts per division. The resulting trace is a graph of voltage against

time.

If the input signal is periodic, a nearly stable trace can be obtained just by setting

the time base to match the frequency of the input signal. For example, if the input signal

is a 50 Hz sine wave, then its period is 20 ms, so the time base should be adjusted so that

the time between successive horizontal sweeps is 20ms. This mode is called continual

sweep. To provide a more stable trace, modern oscilloscopes have a function called the

trigger. When using triggering, the scope will pause each time the sweep reaches the

extreme right side of the screen. The scope then waits for a specified event before

drawing the next trace. The trigger event is usually the input waveform reaching some

user-specified threshold voltage in the specified direction (going positive or going

negative).

The effect is to resynchronise the time base to the input signal, preventing

horizontal drift of the trace. In this way, triggering allows the display of periodic signals

such as sine waves and square waves. Trigger circuits also allow the display of no

periodic signals such as a single pulses or pulses that don’t recur at a fixed rate.

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Tabulation

Sl. No. Resistance Value by Colour Coding (Ω) Resistance Value by Multimeter (Ω)

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Most oscilloscopes allow the user to bypass the time base and feed an external signal into

the horizontal amplifier. This is called X-Y mode, and is useful for viewing the phase

relationship between tow signals, which is commonly done in radio and television

engineering. When the two signals are sinusoids of varying frequency and phase, the

resulting trace is called a Lissajous curve.

Oscilloscopes may have two or more input channels, allowing them to display

more than one input signal on the screen. Usually, the oscilloscope has a separate set of

vertical controls for each channel, but only one triggering system and time base.

Usage of CRO:

One of the most frequent uses of oscilloscopes is troubleshooting malfunctioning

electronic equipments. An oscilloscope can graphically show signals: whereas a

voltmeter can show totally unexpected voltage, a scope may reveal that the circuit is

oscillating. In other cases, the precise shape of pulse is important.

In electronic equipment, for example, the connections between stages (e.g.

electronic mixers, electronic oscillators, amplifiers) may be ‘probed’ for the expected

signal, using the scope as a simple signal tracer. If the expected signal is absent or

incorrect, some preceding stage of the electronics circuit is not operating correctly. Since

most failures occur because of a single faculty component, each measurement can prove

that half of the stages of a complex piece of equipment either work or probably did not

cause the fault.

Once the faulty stage is discovered, further probing can usually tell a skilled

technician exactly which component has failed. Once the component is replaced, the unit

can be restored to service, or at least the next fault can be isolated.

Another use is to check newly designed circuitry. Often a newly designed circuit

will suffer from design errors, bad voltage levels, electrical noise etc.

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Multimeter:

A Multimeter is an electronic measuring instrument that contributes several

functions in one unit. 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%

Result:

Thus the resistor colour coding, usage of CRO and multimeter are studied.

~ 39~

Pin Diagrams:

AND Gate:

OR Gate:

NOT Gate:

IC 7408

~ 40~

EX: NO: STUDY AND VERIFICATION OF LOGIC GATES

DATE:

Aim:

To verify the truth table of the logic gates AND, OR, NOT, NAND & NOR using

74XX ICs.


IC 7432(OR Gate)

IC 7408(AND Gate)

IC 7404(NOT Gate)

IC 7400(NAND Gate)

IC 7402(NOR Gate)

Digital IC trainer kit

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:

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

~ 41~

NAND Gate:

NOR Gate:

IC 7400

~ 42~

OR Gate:

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

NOT Gate:

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 the inverter is:

F = x’

NAND Gate:

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)′

~ 44~

NOR Gate:

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)′

Procedure:

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 LED’s.

Result:

Thus the logic gates AND, OR, NOT, NAND and NOR are studied and their truth tables verified.

~ 45~

CIRCUIT DIAGRAM :

+Vcc=+5V

5.1K+2.2K

OA79

3.3K+330ΩΩΩΩ

Vo

0.01µµµµF

0.01µµµµF

4 8 7

IC555 6 3 2

5 1

~ 46~

EX: NO: Generation of Clock Signal

DATE:

AIM:

To generate a clock signal of 1KHz (square waveform) by an astable multivibrator using IC555 timer. APPARATUS REQUIRED:

Equipments &

Components

Range Quantity

1. Power Supply 2.Resistors 3.Capacitors 4.CRO 5.Diode 0A79 6.IC555

(0-30) V

3300+330=3.630KΩ,

5.1+2.2=7.3KΩ

0.01µF

0.1µF (0-20) MHz

1 1 1 1 1 1 1 1

DESIGN:

Case (I)

Given f = 1KHz and D =0.5

Frequency of astable multivibrator, f = C)R+R(

45.1

BA

Then C =f)R+R(

45.1

BA

D = )R+R(

R

BA

B = 0.5

0.5RA +0.5RB = RB

RA = RB

~ 47~

TABULAR COLUMN:

Amplitude (V) Timeperiod (ms)

Output

MODEL GRAPH:

Vcc

2/3 Vcc

1/3 Vcc

0

t (ms)

~ 48~

Let C = 0.1µF, RA =RB =R

f = C)R+R(

45.1

BA

f =RC2

45.1 =>1KHz =

R*10*0.1*2

45.16-

R = 7.2Kohm

Case (ii)

Given f = 1KHz and D =0.25

Frequency of astable multivibrator,

f = C)R2+R(

45.1

BA

Then C = f)R2+R(

45.1

BA

D = BA

B

R2+R

R = 0.25

RA +2RB = 4RB RA = 2RB

Let C = 0.1µF, RA = 2RB

f = C)R2+R(

45.1

BA

f = CR4

45.1

B

=>1KHz = B

6- R*10*0.1*4

45.1

RB = 3.625Kohm

RA =7.25Kohms

~ 50~

THEORY:

The 555 timers is a highly stable device for generating accurate time delay or oscillation. A single 555 timer can provide time delay ranging from microseconds to hours whereas counter timer can have a maximum timing range of days. An astable multi vibrator is a square waveform generator. Forcing the Op-amp to operate in the saturation region generates square waveform. It is a free running symmetrical multivibrator because it does not require any external trigger

PROCEDURE:

1. The connections are given as shown in the circuit diagram. 2. The square waveform is obtained at output pin of Op-amp. 3. Note the amplitude & Time period of the of the waveform & Plot it in the graph. 4. Duty cycle is calculated using the formula given.

RESULT:

Thus IC555 timer was operated in astable mode to generate square wave. Theoretical Duty cycle: 25%

Practical Duty cycle : -----------.

~ 51~

EX: NO: SOLDERING AND CHECKING CONTINUITY

DATE:

Aim:

To practice soldering of plates and wires

Tools Required:

1. Soldering iron

2. Solder and

3. Flux

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.

~ 53~

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.

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.

~ 54~

Electronic Components

Resistor Capacitor

PN Diode

Transistor

Integrated Circuit (IC)

~ 55~

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


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.

~ 57~

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, IC’s 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.

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.

~ 59~

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.

~ 60~

Circuit diagram :( Half wave rectifier with capacitor)

15 1N 4007 + +

470Ω -470 µµµµF /25V

230 V 0 R Vdc +

- Vac 15 -

Circuit diagram:(Half wave rectifier without capacitor)

15

1N 4007

470Ω CRO

230 V 0 R

Vac 15 Circuit diagram: (Full wave Rectifier without capacitor)

15V

D1 D2 230 V 1N 4007

+

D3 D4 R + 470 µµµµF

470Ω Vdc - 25 V

-

Vac

Circuit diagram: (Full wave Rectifier with capacitor)

15V

D1 D2 230 V 1N 4007

D3 D4 + 470 µµµµF CRO

R - 25 V

A

A

A

A

~ 61~

EX: NO: 5 MEASUREMENT OF RIPPLE FACTOR FOR

DATE: HALF-WAVE AND FULL-WAVE RECTIFIER Aim:

To study half-wave and full-wave rectifiers and measure the ripple factors with

and without capacitor filter.

Apparatus Required:

Sl. No. Component Name Range Quantity Required

i) CRO (0 – 20 MHz) 1

ii) Multimeter 1

iii) PN Junction Diode IN 4007 1

iv) Transformer 230 Volts /

15 – 0 –15 Volts,

200 mA

1

v) Resistor 470Ω 1

vi) Capacitor 470 µF / 25 V 1

vii) Breadboard - 1

viii) Connecting Wires - As required

Theory:

The process of converting AC voltage and current to Direct current is called

rectification. An electronic device that offers a low resistance to current in one direction

and a high resistance in the other direction is capable of converting a sinusoidal

waveform into a unidirectional waveform. Diodes have this characteristic, which makes it

a useful component in the design of rectifiers. In order to achieve a constant/pure DC

voltage at the output, filtering should be done to the pulsating DC output of the rectifier.

The output varies with the variation in AC mains. Hence a voltage regulator is used to

maintain the output voltage at the same value.

~ 62~

Model Graph:

VI(v)

t (msec) Input Wave Form

Vo (V) With filter Without filter

t (msec) Half Wave Rectifier Output

VO (V) With filter Without filter t (msec) Full Wave Rectifier Output

~ 63~

Diodes are used in a rectifier circuit to convert AC into DC. When only one half

of the AC cycle is rectified, it is known as half-wave rectification. When both the half

cycles are rectified, it is known as full-wave rectification.

Procedure:

Half Wave Rectifier:

(i) Without Capacitor filter:

1. Test your transformer: Give 230v, 50Hz source to the primary coil of the

transformer and observe the AC waveform of rated value without any distortion at

the secondary of the transformer.

2. Connect the half wave rectifier as shown in figure.

3. Measure the Vdc & Vac using DC and AC Voltmeters.

4. Calculate the Ripple factor

5. Compare the theoretical ripple factor with the practical ripple factor.

(ii) With capacitor:

1. Connect the half wave rectifier with filter circuit as shown in fig.

2. Assume r= 10% of ripple peak-to-peak voltage for R= 500Ω. Calculate C using

the formula r = 1/2√3fRC

3. Connect CRO across load.

4. Keep the CRO switch in ground mode and observe the horizontal line and adjust

it to the X-axis.

5. Switch the CRO into DC mode and observe the waveform.

Full wave Rectifier:

(i) Without Capacitor:

1. Test your transformer: Give 230v, 50Hz source to the primary coil of the

transformer and observe the AC waveform of rated value without any distortion

at the secondary of the transformer.

2. Connect the full wave rectifier as shown in figure.

3. Measure the Vdc & Vac using DC and AC Voltmeters.

~ 65~

4. Calculate the Ripple factor

5. Compare the theoretical ripple factor with the practical ripple factor.

(ii)With capacitor:

1. To plot ripple peak-to-peak voltage Vs. Idc to choose C a ripple factor of 0.15 is

assumed.

2. To get a variable load resistance a number of 500Ω, 5W of resistance are to be

connected in parallel. Hence Idc = Vdc /(N X 500). Where N is number of 500Ω

resistances connected in parallel.

3. Plot the graph Idc Vs ripple peak to peak.

4. The above steps are repeated for the various values of capacitance.

Result:

Thus the Half-wave and Full-wave rectifiers, with and without filters are constructed and their ripple factors are obtained.

~ 66~

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

~ 67~

ADDITIONAL EXPERIMENT

EX: NO: 6 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


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′ + A′B

S = A ⊕ B

Carry, C = A.B

where A & B are the input variables and S & C are the output variables. Thus to get the

output sum an XOR gate is used. To get the output carry an AND gate is used.

~ 68~

Full Adder

IC 7486IC 7486

IC 7408

IC 7408

IC 7432

A

B

Cin

S=A B Cin⊕ ⊕

Cout = AB+ACin+BCin

1

2

3

5

46

1

2

3

4

5

6

1

2

3

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

~ 69~

Full Adder

A Combinational circuit that performs the addition of three bits is called as a full

adder. The circuit consists of three inputs and two outputs. The input variables denote the

augend, addend and carry from the previous stage. Sum and carry are the outputs.

The Boolean expressions for the outputs are:

SUM, S = A ⊕ B ⊕ Cin

CARRY, Cout=(A ⊕ B).Cin + A.B

Where x and y are the addend & augend and z is the carry from the previous stage i.e. the

third input.

Procedure:

1. Connections are given as per the logic diagram.

2. Supply and ground connections are given to all the ICs according to their pin

diagrams.

3. Inputs are applied by using switches and the outputs are observed by using

LEDs.

4. The truth table for the given function is verified for all the input

combinations.

Result:

Thus the half adder and full adder circuits are designed with their truth tables verified.

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