DESIGN AND CONSTRUCTION OF A TWIN FLUORESCENT FITTING TO REDUCE STROBOSCOPIC

EFFECT IN WORKSHOPS

SULEIMAN A. A SALIFU 01052249D

ISHMAEL QUAYSON MBIR 01052206D

SUBMITTED IN PARTIAL FULFILMENT FOR THE AWARD OF HIGHER NATIONAL DIPLOMA IN ELECTRICAL/ELECTRONICS

ENGINEERING

DEPARTMENT OF ELECRICAL/ELECTRONICS ENGINEERING ACCRA POLYTECHNIC

SEPTAMBER 2008

CERTIFICATION BY SUPERVISOR

I hereby certify that this project work was carried out under my

supervision. I therefore approve that the work is adequate in scope

and quality for the partial fulfillment of the requirement for the award

of a Higher National Diploma (HND) in Electrical/Electronics

Engineering.

SUPERVISOR:

SIGN…………………………….

DATE……………………………

I

DEDICATION

This project is dedicated to

II

DECLARATION

I ………………………………………………….. Declares that the work

was undertaken whilst in Accra Polytechnic.

I further affirm that, this work so far as I know has not been

submitted to any institution for the award of any certificate and the

source of information has been fully acknowledged

NAME………………………………………..

SIGN…………………………….

DATE……………………………

III

ACKNOWLEDGEMENT

IV

ABSTRACT

The project in question is a Twin Fluorescent Fitting to Reduce

Stroboscopic Effect in Workshops.

The report is to investigates and solve the visual illusions caused by

the stroboscopic effects of lighting on rotating and reciprocating

machinery. The lamps studied were fluorescent, mercury vapor, and

incandescent. The results from the experimentation showed

stroboscopic effects for the fluorescent and the mercury vapor

lamps. No stroboscopic effects were observed from the

incandescent lamps.

The lights are powered by the same source of a power, but are

timed to a different frequency to create variation in movement of the

rotating part of the machine.

V

TABLE OF CONTENTS

CONTENT PAGE

CHAPTER ONE

1.1 INTRODUCTION 1

1.2 BACKGROUND 2

1.3 DEFINATION 3

1.4 OBJECTIVES 4

1.5 SIGNIFICANCE OF STUDY 5

1.6 METHOLOGY 6

CHAPTER TWO

2.1 7

VI

CHAPTER THREE

3.1

CHAPTER FOUR

4.1 GENERAL MODE OF OPERATION

4.2 IMPORTANT

4.3 PRECAUTIONS

4.4 SUMMARY

4.5 RECORMENDATIONS

REFERNCE

VII

CHAPTER ONE

1.1 INTRODUCTION

In an installation where rotating machinery is present and where

discharge lamps are used, there is a risk that, the raotating parts

may appear stationary. This effect is known as stroboscopic effect.

It only occurs on discharge lamp, because their discharge is being

extinguished twice every cycle, which causes them to flicker 10ms.

This does not happen in incandescent lamps because their filament

does not cool fast enough to show any signed of cycle variation.

The simplest way to understand stroboscopic effect is to consider

the spoke of rotating wheel. At the moment in time the discharge

lamp is receiving zero voltage, a spoke is always in the position that

was occupied by another spoke whose particular time difference is

equal to one half-cycle of the supply frequency.

1

1.2 BACKGROUND

With the achievement of technological aspect, the present

inventions are relative to stroboscopic effects. These effects can be

minimized by two methods.

If a three phase supply is available this effect can be reduced by

connecting the lamps to alternate phase. As the lamp attain their

maximum and minimum values of light output in sequence, the

overall illumination is kept practically constant thereby keeping the

stroboscopic effect to minimum.

If a single-phase supply is available the head-lag circuit can be

used. In this case we are not going to deal with the single-phase.

The construction of a twin circuit these lamps A and B are supplied

by an oscillating source with frequency different from that of the

phase supplied to the machine.

2

1.3 DEFINITION

The mentioned project is a twin fluorescent light which is oscillated

to different frequency as compared to the frequency of the supply

power to the rotating machine to make a rotating part of a machine

visible.

Even though most industrial machine uses three phase supply,

there’s no guarantee that the problem could be solved by giving the

lighting system to a single phase out of the three. Lamps like

filament bulbs could had been used to solve this problem because

the coil in the bulbs does not cool down, but because of the high

power loss, heat and power consumption it also has become

impossible that type of light to be approved for our industries.

The best way so far is to construct a twin fluorescent lighting system

which is powered with power supply with different frequency from

the main supply.

3

1.4 OBJECTIVES

The main objective of this is to keep stroboscopic effect in Ghana in

to minimum such as our industries and local workshop where there

is so much revolving machines operating all the time.

The aim of this project is to minimize the dangerous situation which

could let ignorant people come in contact with these rotating parts.

4

1.5 SIGNIFICANCE OF STUDY

The main significance of this project is that:

1. the lighting system is easy to operate

2. the system is lass expensive as compared to hazards that

this project helps to avoid

3. it consumes less expensive and consumes less power.

5

1.6 METHODOLOGY

The required electronics components for this project shall be

acquired from a market at hand and the rest imported via Maplin

Electronics UK.

All important information needed for this project to takeoff was

acquired form two main source namely primary and secondary

sources.

Primary source were sources were the personal interactions with my

supervisor and workers of a well equipped and well knowledgeable

on this project.

Secondary sources were the research at the library and the internet.

6

CHAPTER TWO

2.1 TEMPORAL ALIASING

Temporal aliasing is the term applied to a visual phenomenon also

known as the stroboscopic effect. It also accounts for the "wagon-

wheel effect", so called because in video or motion pictures, spoke

wheels on horse-drawn wagons sometimes appear to be turning

backwards.

Temporal aliasing is one example of a range of phenomena called

aliasing that occur when continuous motion is represented by a

series of short or instantaneous samples. It occurs when (a) the

view of a moving object is represented by a series of short samples

as distinct from a continuous view, and (b) the moving object is in

rotational or other cyclic motion at a rate close to the sampling rate.

7

2.2 EXPLANATION

Consider the stroboscope as used in mechanical analysis. This may

be a "strobe light" that is fired at an adjustable rate. Suppose you

are looking at something rotating at 60 revolutions per second: if you

view it with a series of short flashes at 60 times per second, each

flash illuminates the object at the same position in its rotational

cycle, so it appears that the object is stationary. Furthermore, at a

frequency of 60 flashes per second, persistence of vision smoothes

out the sequence of flashes so that the perceived image is

continuous.

If you view the same rotating object at 61 flashes per second, each

flash will illuminate it at a slightly earlier part of its rotational cycle.

Sixty-one flashes will occur before you see the object in the same

position again, and you will perceive the series of images as if it is

rotating backwards once per second.

The same effect occurs if you view the object at 59 flashes per

second, except that each flash illuminates it a little later in its

rotational cycle and so, it seems to be slowly rotating forwards.

In the case of motion pictures, action is captured as a rapid series of

still images and the same stroboscopic effect can occur.

8

2.3 WAGON-WHEEL EFFECT

The wagon-wheel effect, (alternatively, or stagecoach-wheel effect,

stroboscopic effect) is an optical illusion in which a spoked wheel

appears to rotate differently from its true rotation. The wheel can

appear to rotate more slowly than the true rotation, it can appear

stationary, or it can appear to rotate in the opposite direction from

the true rotation. This last form of the effect is sometimes called the

reverse rotation effect.

The wagon-wheel effect is most often seen in film or television

depictions of stagecoaches or wagons in Western movies, although

recordings of any regularly spoked wheel will show it, such as

helicopter rotors and aircraft propellers. It can also commonly be

seen when a rotating wheel is illuminated by flickering light. These

forms of the effect are known as stroboscopic effects and they arise

from temporal aliasing: the original smooth rotation of the wheel is

visible only intermittently.

9

A version of the wagon-wheel effect can also be seen under

continuous illumination.

Wagon-wheel Effect under stroboscopic conditions

Stroboscopic conditions ensure that the visibility of a rotating wheel

is broken into a series of brief episodes in which its motion is either

absent (in the case of movie cameras) or minimal (in the case of

stroboscopes), interrupted by longer episodes of invisibility. It is

customary to call the former episodes frames. A movie camera

typically operates at 24 frames per second, and standard television

operates at 59.94 or 50 images per second (a video frame is two

separate images; see interlace.) A stroboscope can typically have

its frequency set to any value. Artificial lighting that is temporally

modulated when powered by alternating current, such as gas

discharge lamps (including neon, mercury vapor, sodium vapor and

fluorescent tubes), flicker at twice the frequency of the power line

(for example 120 times per second on a 60 cycle line). In each cycle

of current the power peaks twice (once with positive voltage and

once with negative voltage) and twice goes to zero, and the light

output varies accordingly. In all of these cases, a person sees a

rotating wheel under stroboscopic conditions. Imagine that the true

rotation of a four-spoke wheel is clockwise.

10

The first instance of visibility of the wheel may occur when one

spoke is at 12 o'clock. If by the time the next instance of visibility

occurs, the spoke previously at 9-o'clock has moved into the 12-

o'clock position, then a viewer will perceive the wheel to be

stationary. If at the second instance of visibility, the next spoke has

moved to the 11:30 position, then a viewer will perceive the wheel to

be rotating backwards. If at the second instance of visibility, the next

spoke has moved to the 12:30 position, then a viewer will perceive

the wheel to be rotating forwards, however more slowly than the

wheel is actually rotating.

The effect relies on a motion perception property called beta

movement: motion is seen between two objects in different positions

in the visual field at different times providing the objects are similar

(which is true of spoked wheels - each spoke is essentially identical

to the others) and providing the objects are close (which is true of

the originally 9-o'clock spoke in the second instant - it is closer to 12

o'clock than the originally 12-o'clock spoke). The wagon-wheel effect

is exploited in some engineering tasks, such as adjusting the timing

of an engine. This same effect can make some rotating machines,

such as lathes, dangerous to operate under artificial lighting

because at certain speeds the machines will falsely appear to be

stopped or to be moving slowly.

11

Finlay, Dodwell, and Caelli (1984) and Finlay and Dodwell (1987)

studied perception of rotating wheels under stroboscopic illumination

when the duration of each frame was long enough for observers to

see the real rotation. Despite this, the rotation direction was

dominated by the wagon-wheel effect. Finlay and Dodwell (1987)

argued that there are some critical differences between the wagon-

wheel effect and Beta motion, but their argument has not troubled

the consensus.

2.4 ETYMOLOGY

In electrical engineering, when a continuous signal is replaced by a

series of samples — say, a 24.1 Hz signal is sampled 24 times per

second — the result seems the same as if a 0.1 Hz signal were

sampled 24 times per second, so 0.1 Hz is said to be an "alias" of

24.1 Hz.

12

2.5 STROBOSCOPE

A stroboscope, also known as a strobe, is an instrument used to

make a cyclically moving object appear to be slow-moving, or

stationary. The principle is used for the study of rotating,

reciprocating, oscillating or vibrating objects. Machine parts and

vibrating strings are common examples.

In its simplest form, a rotating disc with evenly-spaced holes is

placed in the line of sight between the observer and the moving

object. The rotational speed of the disc is adjusted so that it

becomes synchronized with the movement of the observed system,

which seems to slow and stop. The illusion is caused by temporal

aliasing, commonly known as the "stroboscopic effect".

In electronic versions, the perforated disc is replaced by a lamp

capable of emitting brief and rapid flashes of light. The frequency of

the flash is adjusted so that it is equal to, or a unit fraction below or

above the object's cyclic speed, at which point the object is seen to

be either stationary or moving backward or forward, depending on

the flash frequency.

13

APPLICATIONS

Stroboscopes play an important role in the study of stresses on

machinery in motion, and in many other forms of research. They are

also used as measuring instruments for determining cyclic speed.

As a timing light they are used to set the ignition timing of internal

combustion engines.

In medicine, stroboscopes are used to view the vocal cords for

diagnosis. The patient hums or speaks into a microphone which in

turn activates the stroboscope at either the same or a slightly

different frequency. The light source and a camera are positioned by

endoscope.

Another application of the stroboscope can be seen on many

gramophone turntables. The edge of the platter has marks at

specific intervals so that when viewed by incandescent lighting

powered at mains frequency, and provided the platter is rotating at

the correct speed, the marks appear to be stationary.

Flashing lamp strobes are also adapted for pop use, as a lighting

effect for discotheques and night clubs where they give the

impression of dancing in slow motion.

14

OTHER EFFECTS

Rapid flashing can give the illusion that white light is tinged with

colour, known as Fechner colour. Within certain ranges, the

apparent colour can be controlled by the frequency of the flash, but

it is an illusion generated in the mind of the observer and not a real

colour. The Benham's top demonstrates the effect.

At certain frequencies, flashing light can trigger epileptic seizures in

some people.

STROBE LIGHT

Strobe light or stroboscopic lamp, commonly called a strobe, is a

device used to produce regular flashes of light. It is one of a number

of devices that can be used as a stroboscope. The word originated

from the Greek strobes, meaning "act of whirling."

Strobe lights have many uses, including scientific and industrial

applications, but are particularly popular in clubs where they are

used to give an illusion of slow motion (cf. temporal aliasing). Other

well-known applications are in alarm systems, theatrical lighting

(most notably to simulate lightning), and as high-visibility running

lights. They are still widely used in law enforcement and other

emergency vehicles, though they are slowly being replaced by LED

15

technology in this application, as they themselves largely replaced

halogen lighting. Strobe lighting has also been used to see the

movements of the vocal cords in slow motion during speech, a

procedure known as video-stroboscopy. Special calibrated strobe

lights, capable of flashing up to hundreds of times per second, are

used in industry to stop the motion of rotating and other repetitively-

operating machinery and to measure the rotation speeds or cycle

times. Strobelights are often used in nightclubs and raves, and are

available for home use for special effects or entertainment. A typical

commercial strobe light has a flash energy in the region of 10 to 150

joules, and discharge times as short as a few milliseconds, often

resulting in a flash power of several kilowatts. Larger strobe lights

can be used in “continuous” mode, producing extremely intense

illumination.

The light source is commonly a xenon flash lamp, which has a

complex spectrum and a color temperature of approximately 5,600

Kelvin’s. In order to obtain colored light, colored gels must be used.

16

CHAPTER THREE

3.1 Stages of Operation

There are two main stages involved in the operation of this system.

These are

1. Converting 50Hz To 0Hz (AC to DC)

2. Converting 0Hz to 50Hz (DC to AC)

3.2 Converting 50Hz to 0Hz (AC to DC)

In the conversion of the mains from 50Hz to 0Hz there three stages

involves namely

a. Stepping Down

b. Rectification

c. Smoothing

a. Stepping Down

In stepping down a transformer is used to step the voltage of the

mains from 220V/50Hz to 12Volts.

A transformer is a device that transfers electrical energy from one

circuit to another through inductively coupled electrical conductors.

A changing current in the first circuit (the primary) creates a

changing magnetic field; in turn, this magnetic field induces a

changing voltage in the second circuit (the secondary).

17

By adding a load to the secondary circuit, one can make current flow

in the transformer, thus transferring energy from one circuit to the

other.

The secondary induced voltage VS, of an ideal transformer, is scaled

from the primary VP by a factor equal to the ratio of the number of

turns of wire in their respective windings: Vs/Vp = Ns/Np

By appropriate selection of the numbers of turns, a transformer thus

allows an alternating voltage to be stepped up — by making NS

more than NP — or stepped down, by making it less.

Transformers are some of the most efficient electrical 'machines',

with some large units able to transfer 99.75% of their input power to

their output. Transformers come in a range of sizes from a

thumbnail-sized coupling transformer hidden inside a stage

microphone to huge units weighing hundreds of tons used to

interconnect portions of national power grids. All operate with the

same basic principles, though a variety of designs exist to perform

specialized roles throughout home and industry.

18

b. Rectification

Rectifier diodes are used in power supplies to convert alternating

current (AC) to direct current (DC), a process called rectification.

Bridge rectifiers

There are several ways of connecting diodes to make a rectifier to

convert AC to DC. The bridge rectifier is one of them and it is

available in special packages containing the four diodes required.

Bridge rectifiers are rated by their maximum current and maximum

reverse voltage. They have four leads or terminals: the two DC

outputs are labelled + and -, the two AC inputs are labelled .

The diagram below shows the operation of a bridge rectifier as it

converts AC to DC. Notice how alternate pairs of diodes conduct.

19

c. The Smoothing Capacitor

The full-wave bridge rectifier however, gives us a greater mean d.c. value (0.637Vmax)

with less superimposed ripple while the output wveform is twice that of the frequency

of the input supply frequency. We can therefore increase its average d.c. output level

even higher by connecting a suitable smoothing capacitor across the output of the

bridge circuit as shown below.

The smoothing capacitor converts the full-wave rippled output of the

rectifier into a smooth d.c. output voltage.

20

Two important parameters to consider when choosing a suitable a

capacitor are its Working Voltage, which must be higher than the no-

load output value of the rectifier and its Capacitance Value, which

determines the amount of ripple that will appear superimposed

ontop of the d.c. voltage. Too low a value and the capacitor has little

effect. As a general rule of thumb, we are looking to have a ripple

voltage of less than 100mV peak to peak.The main advantages of a

full-wave bridge rectifier is that it has a smaller a.c. ripple value for a

given load and a smaller reservoir or smoothing capacitor than an

equivalent half-wave rectifier. The fundamental frequency of the

ripple voltage is twice that of the a.c. supply frequency (100Hz)

where for the half-wave rectifier it is exactly equal to the supply

frequency (50Hz). The amount of ripple voltage that is

superimposed on top of the d.c. supply voltage can be virtually

eliminated by adding an an improved π-filter (pi-filter) to the ouput

terminals of the bridge rectifier. This type of low-pass filter consists

of two smoothing capacitors, usually of the same value and a choke

or inductance across them to introduce a high impeadance path to

the alternating ripple component.

21

3.2 Converting 0Hz to 50Hz (DC to AC).

The DC to AC converter also known as power inverter operates in

four stages namely (a) Regulating (b) Pulse generation (oscillating),

(c) Amplification and (d)Stepping Up.

(a)Regulating

Since the amplitude of the oscillator is determined by the Vcc. or the

power supplied to it, is very important to regulate it to match the

Gate to Source voltage of the Mosfets which would be used to

amplify the signals from the Oscillator.

The simplest voltage regulator uses just a resistor and a zener

diode. In the circuit diagram you can see a resistor (R1) and a zener

diode (ZD1) connected across a power supply. The resistor is

connected to the positive (+ve) supply wire and the zener diode

anode is connected to the zero volt (ground) wire. At the junction of

these two components the voltage is clamped by the zener diode to

its specified voltage - in this case 5.6 volts but can be changed to

9.1 or any voltage to suit the Vbe of the transistor(Mosfets) in the

amplifier.

This method is OK for low currents but the resistor becomes too hot

if larger currents are needed. To cope with this problem we can add

the NPN transistor (Q1) .

22

Now the transistor passes the current required at the output.

What is the output voltage?

It is easy to calculate. The voltage at Q1 base connection is 5.6

volts.

The voltage between base and emitter of a silicon transistor is

always 0.6 volts if the transistor is "on".

So the voltage at the Q1 emitter (Vout) must be 5.6 - 0.6 = 5.0 volts.

The output voltage will remain at a constant voltage of 5.0 volts

provided that the input voltage from the supply is more than 6 volts

(the zener voltage plus a little to compensate for that "lost" across

the resistor).

23

In fact the input voltage can be swinging up and down between, say,

6 volts and 12 volts and the output voltage at Q1 emitter will still be

a steady 5.0 volts.

The limiting factors are the amount of heat generated by R1, ZD1

and Q1 since all excess voltage must be shed as heat. The

"wattage" ratings of the individual components must be calculated to

suit:

1. The average input current (through R1 and ZD1) and the output

current (through Q1). can be calculated from Ohms Law and is

decided by whatever the regulator is to supply voltage to.

Ohms Law I = V/R

V = Volts

I = Amps if R = Ohms or

I = mA if R = k½

Let's assume the following:

The circuit which this regulator is driving needs 9.0v at a current of 200A.

A TIP41 transistor is suitable since it can handle current up to 15 A.Its gain at 40 is listed as 40 (typ) so it's easy to see that it will need at least 1mA into its base to allow 15A to flow from collector to emitter.

24

Watts = Volts x Amps milliWatts = Volts x milliAmps

Volts x Amps = Watts

Since the regulating voltage is 9volts and the maximum current from

the transistor is 15A

9volts x 15A = 135watts.

25

0V

+Ve

C2C1

Q2Q1

R4R3R2R1

(b) Pulse Generation (oscillating)

Since the DC power haves no frequency, there’s a need for an

introduction of an oscillator such as an astable multivibrator to

change the frequency from zero to 50Hz.

A multivibrator is an electronic circuit used to implement a variety

of simple two-state systems such as oscillators, timers and flip-flops.

It is characterized by two amplifying devices (transistors, electron

tubes or other devices) cross-coupled by resistors and capacitors.

The most common form is the astable or oscillating type, which

generates a square wave - the high level of harmonics in its output

is what gives the multivibrator its common name.

Astable Multivibrator circuit

26

This circuit shows a typical simple astable circuit, with an output

from the collector of Q1, and an inverted output from the collector of

Q2. Suggested values which will yield a frequency of about 48 to

50Hz:

R1, R4 = 220Ω

R2, R3 = 10K Ω

C1, C2 = 1μF

Q1, Q2 = BC547 or C945 NPN switching transistor

Basic mode of opera tion

The circuit keeps one transistor switched on and the other switched

off. Suppose that initially, Q1 is switched on and Q2 is switched off.

State 1:

Q1 holds the bottom of R1 (and the left side of C1) near

ground (0V).

The right side of C1 (and the base of Q2) is being charged by

R2 from below ground to 0.6V.

R3 is pulling the base of Q1 up, but its base-emitter diode

prevents the voltage from rising above 0.6V.

27

R4 is charging the right side of C2 up to the power supply

voltage (+V). Because R4 is less than R2, C2 charges faster

than C1.

When the base of Q2 reaches 0.6V, Q2 turns on, and the following

positive feedback loop occurs:

Q2 abruptly pulls the right side of C2 down to near 0V.

Because the voltage across a capacitor cannot suddenly

change, this causes the left side of C2 to suddenly fall to

almost -V, well below 0V.

Q1 switches off due to the sudden disappearance of its base

voltage.

R1 and R2 work to pull both ends of C1 toward +V, completing

Q2's turn on. The process is stopped by the B-E diode of Q2,

which will not let the right side of C1 rise very far.

This now takes us to State 2, the mirror image of the initial state,

where Q1 is switched off and Q2 is switched on. Then R1 rapidly

pulls C1's left side toward +V, while R3 more slowly pulls C2's left

side toward +0.6V. When C2's left side reaches 0.6V, the cycle

repeats

28

Multivibrator Frequency

Where...

f is frequency in Hertz.

R2 and R3 are resistor values in ohms.

C1 and C2 are capacitor values in farads.

T is period time (In this case, the sum of two period durations).

f is frequency in Hertz.

R2 and R3 are resistor values in ohms.

C1 and C2 are capacitor values in farads.

T is period time (In this case, the sum of two period durations).

(c) Amplification

Angle of flow or conduction angle

50% of the input signal is used (Θ = 180° or π, i.e. the active

element works in its linear range half of the time and is more or less

turned off for the other half). In most Class B, there are two output

devices (or sets of output devices), each of which conducts

alternately (push–pull) for exactly 180 deg (or half cycle) of the input

signal; selective RF amplifiers can also be implemented using a

single active element.

29

These amplifiers are subject to crossover distortion if the handoff

from one active element to the other is not perfect, as when two

complimentary transistors (i.e. one PNP, one NPN) are connected

as two emitter followers with their base and emitter terminals in

common, requiring the base voltage to slew across the region where

both devices are turned off.

The amplifier is built from a class B push to push amplifier with

independent inputs unlike the normal audio amplifier because in the

normal system, the inputs are bridged together to one input and the

output also bridged. But to obtain a angle of 3600 of input used the

two inputs has to be separated to for the inputs to swing at 90-90-

90-90 making the out put still maintained as a sinodial signal.

30

(d) Stepping Up.

For stepping up the signal amplified it is important to use a

transformer which has low power loss. One ideal type of transformer

is a sandwich double wounded transformer with laminated core.

The transformer is made 12-0-12 or 9-0-9 at the primary and 220-

240 at the secondary.

Laminated core

This is the most common type of transformer, widely used in

appliances to convert mains voltage to low voltage to power

electronics

Widely available in power ratings from 1.2w to several

kilowatts

Insulated laminations minimize eddy current losses

Most use a split bobbin, giving a high level of insulation

between the windings

Rectangular core

31

220/240V

0V

0V

9V

9V T1

Core laminate stampings are usually in EI shape pairs. Other

shape pairs are sometimes used.

Mumetal shields can be fitted to reduce EMI (electromagnetic

interference)

A screen winding is occasionally used between the 2 power

windings

Many such transformers have a thermal cut out built in, many

don't

4 turns per volt is typical for continuous use

Occasionally seen in low profile format for use in restricted

spaces

laminated core made with silicon steel with high permeability

32

3.3 Schematic Diagram

33

3.4 COMPONENT LIST

COMPONENT DESCRIPTION QUANTITY

T1 9-0-9/220V STEP-UP

TRANSFORMER

1

T2 220V /12vSTEP-DOWN

TRANSFORMER

1

ZD1 9v ZENER DIODE 1

D1 BRIDGE DIODE[GBU8M] 1

LED 1-3 LED(LIGHT EMITTING DIODE) 3

Q2-Q6 RFP40N10 4

C1,C2 15000uf 2

Q1 C2580 1

R1 1kΩ 1

SCK1 Dual 13amps 3pin 1

F1 20A Circuit Breaker 1

34

Component List for Oscillator

Q1,Q2 C945 2

C1,C2 1uf 2

R1,R4 220Ω 2

R2,R3 10KΩ 2

PCB Vero Board 1

Auxiliaries

Cable 6mm Auto flex 2

R4,R5,R7,R8 470Ω resistor

Heat sink Aluminum heat sink with fins 1

NOTE:

R - RESISTOR C - CAPACITOR

T - TRANSFORMER D - DIODE

Q - TRANSISTOR ZD- ZINER DIODE

35

3.5 CABLE SELECTION

Cables are the main material that connects on component to the

other so it is very important that the right cable is used to deliver the

right amount of power needed at a particular place.

Cables for dc applications should not be less than 6mm in diameter

and colors are also very important because to clearly explain to

someone the type of signal passing through the cable whether it is

positive or negative. For example a Red cable clearly explains that

the power passing through the cable is positive.

36

3.6 LIMITATIONS

The difficulties involved in getting the major component from an

original source was very difficult because all the companies

who manufactures these components do not sell components in

small quantities and it was very hectic getting all these

components.

37

4.5 CIRCUIT CONSTRUCTION

This circuit was first divided into four stages and each stage was

carefully tested with electronics stimulator software and then

assembled.

The oscillator circuit was assembled on a Vero board (PCB) and

then tested with a signal generator and an oscilloscope to check the

frequency response. This circuit was finally tested after all he four

parts were puts together to check and correct its short falls.

Much consideration was given to meter readings or voltages and

current.

38

4.6 GENERAL MODE OF OPERATION

220 volts AC (alternating current) /50Hz is connected to a

transformer to step it down to 15 volts AC. The supply is then

rectified and smoothened.

The smoothened power is then connected to an oscillator to change

its frequency back to 50Hz. The output of the oscillator is then

amplified by a push pull amplifier which has a step-up transformer to

raise the signal from 12volts AC to 220volts AC.

39

4.7 PRECAUTIONS

In other to arrive at a good and a successful project, the following

precautions were taken into consideration:

1. The circuit was built under supervision to ensure accuracy.

2. The circuit diagram was first tested with schematic circuit

stimulator software and then mounted on a Vero board and

then rechecked for accuracy to prevent damage of any

component.

3. The right size of cables was used at high current lines like the

main positive input which is connected from and to the battery.

4. The entire component were thoroughly checked and tested for

consistency and efficiency.

5. Correct soldering techniques were ensured as well as the

usage of a correct solder.

6. The right tools and equipment were used for this project.

7. Suitable equivalent replacement of components was ensured

at places where the original components were not available.

40

4.8 CONCLUSION

The entire project was finally concluded that; this lighting system

could enhance the sight of worker who use4s rotating machine to

caution them that there’s a rotating machine.

This project could go a long way to help reduce accident caused by

this problem in the workshop and also help in creating employment

for the youth if encouraged in the country.

41SUMMARY

From the above project it was realized that, when the supply given

to lights have different phase angle to the supply of the rotating

machine the rotating parts would be more visible to avoid accidents

in the workshop.

42

RECOMMENDATIONS

My recommendations for workshops, machine shops and industries

who uses rotating machine or machines with rotating parts and also

for industries who work in the night with machines which uses three

phases.

43

REFERENCES

1. Carols Advance Electronics and Training Centre.

2. www.wikipedia.com/english