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DESIGN OF AN ELECTRONIC SIREN CIRCUIT

Final Year report submitted to

Kampala International University in partial fulfillment of the requirement for

the award of the degree

of

Bachelor of Science

in Telecommunications Engineering

by

MOHAMED HASSAN JAMA BSTC/36056/122/DF

DEPARTMENT OF ELECTRICAL AND TELECOMMUNICATION ENGINEERING

SCHOOL OF ENGINEERING AND APPLIED SCIENCES

APRIL 2016

©2016, Mohamed. Hassan Jama. All rights reserved.

i

Declaration

I Mohamed Hassan Jama, hereby affirm that this work was done by me and has never

been presented anywhere else for the award of a degree.

Mohamed Hassan Jama

Signature……………………. Date……………………..

ii

Approval

It is certified that the work contained in the project titled “design of an electronic siren

circuit” by Mohamed Hassan Jama BSTC/36056/122/DF has been carried out under my

supervision and that this work has not been submitted elsewhere for a degree final

project.

Project Supervisor

Mr. Adabara Ibrahim

Signature….…………….. Date…………………

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Dedication

I dedicate this project to the Glory of Almighty Allah and to my family.

I would like to said thanks my parents dear Father Hassan Jama Ahmed, dear mother

Amina Jama ahmed, and a special thanks to my dear uncle Mohamoud Haaji Adam

ahmed who support me.

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Acknowledgement

Our profound gratitude goes to Allah Almighty for his love, guidance, protection,

provision, favours and blessings all through the period of my study.

I would also like to thanks my parents special thanks to my uncle Mohamoud Haaji

Adam Ahmed who support financial and friends who helped me a lot in finalizing this

project within the limited time frame.

My appreciation is also greatly expressed to my supervisor Mr. Adabara Ibrahim and to

the entire staff of the department.

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TABLE OF CONTENT

Declaration ................................................................................................................... i

Approval ...................................................................................................................... ii

Dedication .................................................................................................................. iii

Acknowledgement ..................................................................................................... iv

LIST OF TABLES ........................................................................................................ vii

LIST OF FIGURES ..................................................................................................... viii

CHAPTER ONE ............................................................................................................. 1

1.0 Introduction ...................................................................................................................................... 1

1.1 Background ....................................................................................................................................... 1

1.2 Problem statement .......................................................................................................................... 2

1.3 Significance of the project .............................................................................................................. 2

1.4. Aim and Objectives ................................................................................................. 3

1.4.1. General objective......................................................................................................................... 3

1.4.2. The specific objectives................................................................................................................ 3

1.5 Scope of the project. ....................................................................................................................... 3

CHAPTER TWO ............................................................................................................ 4

LITTERATURE REVIEW ................................................................................................ 4

2.1 HISTORY ........................................................................................................................................... 4

2.2 DEVELOPMENT OF A SIREN ........................................................................................................... 5

2.3 Approvals or certifications .............................................................................................................. 8

2.4 Circuit Components ......................................................................................................................... 9

2.4.1 Transistor ....................................................................................................................................... 9

2.4.2 Resistors ...................................................................................................................................... 12

2.4.3 Capacitor ...................................................................................................................................... 13

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2.4.4 Battery .......................................................................................................................................... 13

2.4.5 SIREN ........................................................................................................................................... 14

CHAPTER THREE ......................................................................................................15

METHODOLOGY .........................................................................................................15

3.0 Introduction .................................................................................................................................... 15

3.1 System Block .................................................................................................................................. 15

3.2 CIRCUIT DESIGN AND CIRCUIT OPERATION ........................................................................... 16

3.3 CIRCUIT DESIGN CALCULATIONS .............................................................................................. 18

CHAPTER FOUR .........................................................................................................19

RESULT AND DISCUSSION ........................................................................................19

CHAPTER FIVE...........................................................................................................20

CONCLUSION AND RECOMMENDATION ....................................................................20

5.1 CONCLUSION .................................................................................................................................. 20

5.2 RECOMMENDATION ...................................................................................................................... 20

REFERENCES .............................................................................................................21

Appendix I:Budget ....................................................................................................21

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LIST OF TABLES

Table A1: Budget Table…………………………………………………………………21

viii

LIST OF FIGURES

Fig 2.4.1 Symbol of NPN & PNP transistor .......................................................... 10

Fig 2.4.2 Symbol of transistor amplification ........................................................ 11

Fig 2.4.3 Schematic of transistor amplification mechanism................................... 11

Fig 2.4.4 Resistor .............................................................................................. 13

Fig 2.4.5 Electrolytic Capacitor ........................................................................... 13

Fig 2.4.6 Battery Cell ......................................................................................... 14

Fig. 2.4.7. System Block .................................................................................... 15

Fig. 2.4.8. Circuit Design and Circuit Operation ................................................... 16

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CHAPTER ONE

1.0 Introduction

This chapter provides an overview of the project by giving description of the problem.

Chapter one discusses about the background of the project, problem description, and

aims and objective and project limitation.

1.1 Background

Siren is a device that produces loud noise. They are the means communication. Sirens

can be seen in emergency vehicles such as police cars, ambulances and fire trucks.

Generally, sirens are used as indication or warning. There are different circuits to

produce different sirens.

The word siren first originated in Greek mythology and was also later used to refer to

mermaids. Language and literature have used the word siren as indicative of dangerous

temptations. The siren as we understand today is not something dangerous, but is

generally a warning signal either to stop or proceed, based upon who has used it. So,

though the siren is in itself not dangerous, ignoring a siren, especially a police siren,

can have dangerous consequences.

The two basic types of sirens are pneumatic sirens and electronic sirens. All

conventional sirens were pneumatic sirens and its energy requirements were much

more compared to present day electronic sirens. Pneumatic sirens are also known as

mechanical sirens. In electronic sirens different types of sounds are synthesized with

the combined action of sound modulators, oscillators, and amplifiers. A siren today is

mostly an electronic siren though some emergency vehicles may be fitted with both a

pneumatic siren and an electronic siren

Volume is also an issue. A loud siren will alert people far away but too loud and you’re

potentially damaging the hearing of people not in cars or the vehicle crew. Too quiet

and it doesn’t give people enough time to react. Sirens need to cut through the

background distractions of music, speech or road noises and get past muffling car

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soundproofing. Current sirens resort to high pitched frequencies but these high

frequencies are especially prone to damping from car sound proofing.

This electronic siren circuit design explained here uses minimum number components

and yet is able to produce an ear piercing alarm sound each time it's switched ON,

although it can be use for any other relevant application too, depending upon the user's

preference

In the automobile field this siren is also popularly know as the "Mega Siren" due to the

massive decibel level it generates.

The siren circuit is important in various alarm. For example : the emergency alert,

burglar alarm circuits, Fire alarm circuits, Timer , sensor controls, etc. But sirens are not

always heard as unnecessary noise. Sirens are also used as musical instruments.

Robison’s first siren was described as a musical instrument. Sirens have been used by

various composers/musicians.

1.2 Problem statement

While some frequencies are better heard than others, warnings sounds will generally be

more resilient against environmental. Electronic siren warning will be effective in all

types of lighting and weather conditions.

1.3 Significance of the project

To design an electronic siren device that will serve well in any conditions.

To design and prototype a warning mechanism, which can be triggered when an

emergency situation is detected and which will effectively alert the individual at

risk.

In particular, it must be easy to use, easy to detect, and efficient in mobilizing the

operator to take preventive action.

It is also equally as important that the design is technically and fiscally feasible and

users are willing and inclined to use this mechanism. The success of this project could

potentially save hundreds of lives and fill a niche where no other alerting mechanism

currently exists.

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For the users of this system, it could offer personalized security and peace of mind in

an otherwise stressful environment.

1.4. Aim and Objectives

1.4.1. General objective

The aim of this project is to design an electronic siren circuit which can be used as a

warning and alerting in emergency situations in order to make the lives of humans

easier.

1.4.2. The specific objectives

This circuit can be used in civil defense sirens to give warning at the time of

natural disasters.

This can be used in emergency signals such as search and rescue operations.

It can be used as an intruder alarm.

1.5 Scope of the project

Development of clap switch for devices is a difficult task which requires a good

knowledge in electronics. As this is a complex project, special scope of work is yet to be

determined so that the main objective and goal can be achieved.

These scopes help us to be focused and know about the project. The major steps that

will be involved in this current project are: literature review on electronic sirens, the

design of an electronic siren device will be implemented in home/industries, emergency

vehicles e.t.c. with two transistors to control the switching, the assembling of the

different equipment to obtain the relevant system, testing of the system.

These scopes require: punctuality, self-discipline, time management and problem

solving so that to obtain sufficient and good result.

This circuit is tested theoretically, to implement practically it may require changes.

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CHAPTER TWO

LITTERATURE REVIEW

This chapter will discuss more about all of the information related to the project. It

discusses about the previous history and the present work about the project. The

literature review in this paper is based on internet, journal, books, and articles.

2.1 HISTORY

Siren devices have been used to provide warning and alerting in emergency situations

for ages. Beating on various metal objects was used in ancient times. Later bell towers

were built for this purpose and at the beginning of the 20th century mechanical rotating

sirens started to appear. These are basically formed by an electric motor with a

specially treated head that emits a sound while rotating. Those sirens are still used in

many countries. The development of electronics, however, has also influenced this area

and first electronic sirens started to appear at the end of the 20th century. Electronic

sirens are basically high-performance electronic amplifiers just like those in home sound

systems. However, these sirens work with substantially higher outputs and specific

demands are placed on them in terms of desired extreme reliability and different

methods of their control. Control infrastructure must also be reliable and usually two

independent control channels are required. The loudspeakers for these amplifiers are

placed in a specially-designed sound baffles (horns) and they play the signals stored in

the siren’s digital memory or signals fed to the siren from external sources a

microphone, phone, radio station, common radio and television broadcasting

Electronic sirens are either used as separate, locally controlled equipment or as a part

of larger warning systems, which is their most common application. Unlike the small

systems consisting of several sirens, large systems can be formed by thousands of

connected sirens. Considering the fact that these systems are used only in the

situations of real danger, which is an occasional event, one has to be sure that they will

really function at the time when they are actually needed. Therefore great demands are

placed on automatic testing functions in connection with both sirens and related

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infrastructure. Experience from all over the world shows that power failures and

telecommunication infrastructure failures are very often part of the emergencies

The points of siren are to alert, warn people that an emergency vehicle or situation is

approaching so that they can get out of its way. As such, the sirens are designed to

catch human attention (thus the "up-down" sound you describe). There are many

different types of sirens, and most emergency vehicles have the option to switch

between multiple sirens to avoid putting drivers into a trance like state with the use of

just a single siren. Many times emergency vehicles (especially ambulances and fire

apparatus) will layer multiple sirens simultaneously during a response. Popular siren

types are: "the power call," "Federal Q Siren," (mostly used on fire engines) "hi-lo"

(popular in Europe), "ultra hi-lo," "Yelp," "Wail," "Priority," and "Rumbler" (a new low-

frequency siren)

2.2 DEVELOPMENT OF A SIREN

The history of emergency warning sounds is linked to the history of man's ability to

shape sound. In New York, before the turn of the century, the firemen themselves

pulled the wagons carrying pumps and ladders, while one of them ran ahead through

the congestion shouting and blowing a trumpet. After the turn of the century, the

mechanical siren was invented, the slow rising and falling sound which we associate

with air-raid warnings. It was mounted on the wagon and activated by cranking a

handle.

When fire trucks became motorized, someone had the idea of putting a whistle on the

end of the exhaust pipe and letting the engine-exhaust gasses blow it. It made such a

horrendous shriek that it was finally outlawed. With the arrival of electricity the

mechanical siren was motorized. The operator made it sound with a pedal on the floor;

when he pressed it, the sound would begin to rise; when he released it, the pitch would

fall.

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In the 1960s, when it had become practical to make loud sounds electronically, our

present-day siren arrived. The sounds of the mechanical siren and horns were

synthesized electronically and projected from loudspeakers, mounted on the roof of the

car

Looking at the history of these devices, it becomes clear that the sounds themselves

have never actually been designed. They are, instead, the product of whatever could be

found to make a loud noise.

Yet, with the introduction of the electronic siren, a fundamental change had occurred;

for the first time the sound possibilities were unlimited. It was as practical to synthesize

one sound as any other. But, instead of searching for better sounds, the existing

sounds were simply copied and the limits of the old sirens were passed on to the new

generation.

It turns out these sounds have many problems, the major one being that they are

almost impossible to locate.

Universally people say that they cannot tell where a siren sound is coming from until it

is upon them. Unable to find the sound and becoming more nervous by its approach,

many drivers simply stop and block traffic until they figure out what to do. Others

ignore the sound until they are directly confronted by the vehicle, sometimes with lethal

results. Obviously it is not enough just to let people know there is an emergency vehicle

moving somewhere in the city. They need much more information if they are to know

what to do.

The passage of a siren through a city is one of the largest sonic events in daily life. In

dense urban centers it usually occurs more than one hundred times a day.

In the context of this project, any warning must be effective in all types of lighting and

weather conditions.

It is likely that a visual system would not be suitable for this requirement. On the road

at night, traffic headlights can cause much light pollution and glare and at different

times of the year fog, frost, dew and dirt can also significantly degrade visibility

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In fact, in one study, “Rumar and Ost (1974) reported that, under unfavorable

condition, dirt accumulation can reduce reflected light and contrast on small traffic signs

up to75% and 95% respectively.

The audible frequency range detection for the human ear is from 20 Hz to 20,000 Hz.

Knowing this range is important for the study, as siren noise is included in only a very

small segment of this spectrum.

The most common unit of noise measurement is the decibel (dB) which is a logarithmic

representation of the strength of a sound unit, relative to a specified reference level;

the threshold of hearing.

While some frequencies are better heard than others, warnings sounds will generally be

more resilient against environmental noise if they are composed of multiple sinusoidal

tones.

Amplitude of a sound wave is synonymous with the volume of a signal. The louder the

signal, the more easily it will be heard.

However, high volume alarms can cause distraction to an unintended audience,

annoyance, and for safety reasons.

“A rule of thumb is that when sounds increase in level by approximately 10 dB (or dBA),

their perceived loudness doubles”.

Auditory alarm guidelines suggest that a high urgency warning should be 10-­‐30

decibels higher than the masked threshold, a measurement of listener hearing threshold

based on frequency and decibel level.

A better set of sound signals could not only save lives, but as world population becomes

more and more dense they could also go a long way towards making future urban life

livable.

To expand upon the previously stated definition, a siren is a device or system that

produces acoustical signals that continuously vary in frequency and call for the right of

warning or alerting. These signals (and the electrical signals that are responsible for

producing them) are generally referred to as siren signals. With this definition, it is

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important to note that sirens are generally classified as either electronic (AKA electrical)

or electromechanical (AKA mechanical) siren systems

An electrical siren system is composed of two main components; the first is an

electronic siren amplifier, which is a device powered by the electrical system of the

vehicle and produces an electrical signal that drives an electronic siren speaker, which is

the second component. An electronic siren speaker is comprised of a transducer that

converts the electrical signal produced by the electronic siren amplifier into acoustical

energy. On the other hand, a mechanical siren system is a device that converts

electrical energy directly into acoustical energy without the aid of an electronic power

amplifier. Currently, many emergency vehicles equipped with mechanical sirens are

being outfitted with electrical siren systems. Another important characteristic of the

mechanical and electrical sirens is the corresponding sound waves they produce. The

mechanical system produces a waveform that approximates a square wave, while the

electrical system produces the traditional sine wave.

A NATO study from 2006 indicates Acoustic device/weapon applications identified in the

research include government uses for border security; crowd control and long-range

communication for public safety agencies; and search and rescue and coastal

surveillance for harbour/port police. Military applications include enforcement of

exclusion zones; critical infrastructure protection; psychological operations; traffic

control points/access control points; interdiction operations; checkpoint operations; and

detainee operations.

2.3 Approvals or certifications

Governments may have standards for vehicle-mounted sirens. For example, in

California, sirens are designated Class A or Class B. A Class A siren is loud enough that

it can be mounted nearly anywhere on a vehicle. Class B sirens are not as loud and

must be mounted on a plane parallel to the level roadway and parallel to the direction

the vehicle travels when driving in a straight line.

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Sirens must also be approved by local agencies, in some cases. For example, the

California Highway Patrol approves specific models for use on emergency vehicles in the

state. The approval is important because it ensures the devices perform adequately.

Moreover, using unapproved devices could be a factor in determining fault if a collision

occurs.

The Society of Automotive Engineers, (SAE), Emergency Warning Lights and Devices

committee oversees the SAE emergency vehicle lighting practices and the siren

practice, J1849. This practice was updated through cooperation between the SAE and

NIST, the National Institute of Standards. Though this version remains quite similar to

the California Title 13 standard for sound output at various angles, this updated practice

enables an acoustic laboratory to test a dual speaker siren system for compliant sound

output

2.4 Circuit Components

2.4.1 Transistor

A transistor is a semiconductor device used to amplify and switch electronic signals and

electrical power. It is composed of semiconductor material with at least three terminals

for connection to an external circuit. A voltage or current applied to one pair of the

transistor's terminals changes the current flowing through another pair of terminals.

Because the controlled (output) power can be higher than the controlling (input) power,

a transistor can amplify a signal. Today, some transistors are packaged individually, but

many more are found embedded in integrated circuits.

Transistors fall into two major classes: the bipolar junction transistor (BJT) and the

field-effect transistor (FET). Bipolar junction transistor (BJT) is used

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Bipolar Junction Transistors

The most common type of transistor is a bipolar junction transistor. This is made up of

three layers of a semi-conductor material in a sandwich. In one configuration the outer

two layers have extra electrons, and the middle layer has electrons missing (holes). In

the other configuration the two outer layers have the holes and the middle layer has

the extra electrons.

Fig 2.4.1 Symbol of NPN & PNP transistor

Layers with extra electrons are called N-Type, those with electrons missing called P-

Type. Therefore the bipolar junction transistors are more commonly known as PNP

transistor and NPN transistors respectively. Bipolar junction transistors are typically

made of silicon and so they are very cheap to produce and purchase.

Basic Transistor Amplifiers

An electrical signal can be amplified by using a device which allows a small current or

voltage to control the flow of a much larger current from a dc power source. Transistors

are the basic device providing control of this kind. There are two general types of

transistors, bipolar and field-effect. Very roughly, the difference between these two

types is that for bipolar devices an input current controls the large current flow through

the device, while for field-effect transistors an input voltage provides the control.

To set a transistor to a certain DC level is done by setting up the and

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Fig 2.4.2 Symbol of transistor amplification

The three terminals of a bipolar transistor are called the emitter, base, and collector

(Figure 2.4.3). A small current into the base controls a large current flow from the

collector to the emitter. The current at the base is typically one hundredth of the

collector-emitter current. Moreover, the large current flow is almost independent of the

voltage across the transistor from collector to emitter.

This makes it possible to obtain a large amplification of voltage by taking the output

voltage from a resistor in series with the collector. We will begin by constructing a

common emitter amplifier, which operates on this principle.

Fig 2.4.3 Schematic of transistor amplification mechanism

Transistor as a switch

The bipolar NPN transistors used in this design are basically used as switch, to trigger

the relay and as amplifier to boost the sound level. When a transistor is used as switch,

it must be either OFF or fully ON. In the fully ON state, the voltage VCE across the

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transistor is almost zero and the transistor is said to be saturated because it cannot

pass any more collector current IC. The transistor is off when VIN is less than 0.7 V,

because the base current will be zero. The power developed in a switching transistor is

very small

In the OFF state

Power = VC *IC but IC = 0 (3.1)

P = 0

In the ON state

Power = VC * IC but VCE ≈ O (almost) (3.2)

P ≈ 0

So, the power is very small.

2.4.2 Resistors

Resistors are the most common passive electronic component (one that does not

require power to operate). They are used to control voltages and currents. While a

resistor is a very basic component, there are many ways to manufacture them. In the

past, most resistors were manufactured from carbon composition, a baked mixture of

graphite and clay. These have been almost completely superseded by carbon or metal

film resistor. Wire-wound resistors are used for comparatively low values of resistance

where precise value is important, or for high dissipation. Each style has its own

characteristics that make it desirable in certain types of applications. Choosing the right

type of resistor is important to making high-performance or precision circuits work well.

There are several different resistor construction methods and body styles (or packages)

that are designed for a certain range of applied voltage, power dissipation, or other

considerations. The construction of the resistor can affect its performance at high

frequencies where it may act like a small inductor or capacitor has been added, called

parasitic inductance or capacitance

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Fig 2.4.4 Resistor

2.4.3 Capacitor

A capacitor is a tool consisting of two conductive plates, each of which hosts an

opposite charge. These plates are separated by a dielectric or other form of insulator,

which helps them maintain an electric charge. There are several types of insulators

used in capacitors. Examples include ceramic, polyester, tantalum air, and polystyrene.

Other common capacitor insulators include air, paper, and plastic. Each effectively

prevents the plates from touching each other.

Capacitor has ability to store charge and release them at a later time. Capacitance is

the measure of the amount of charge that a capacitor can store for a given applied

voltage. The unit of capacitance is the farad (F) or microfarad. The capacitors that will

be used in the circuit are electrolytic-capacitor

Fig 2.4.5 Electrolytic Capacitor

2.4.4 Battery

In electricity, a battery is a device consisting of one or more electrochemical cells that

convert stored chemical energy into electrical energy. Since the invention of the first

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battery (or "voltaic pile") in 1800 by Alessandro Volta and especially since the

technically improved Daniel cell in 1836, batteries have become a common power

source for many household and industrial applications.

According to a 2005 estimate, the worldwide battery industry generates US$48 billion in

sales each year, with 6% annual growth.

There are two types of batteries: primary batteries (disposable batteries), which are

designed to be used once and discarded, and secondary batteries (rechargeable

batteries), which are designed to be recharged and used multiple times. Batteries come

in many sizes, from miniature cells used to power hearing aids and wristwatches to

battery banks the size of rooms that provide standby power for telephone exchanges

and computer data canters

Fig 2.4.6 Battery Cell

2.4.5 SIREN

A siren is a circuit which uses two transistors the NPN and PNP to produce a high

frequency by using a speaker, the output of high frequency will be vibrating the

speaker at high frequency hence producing a very sharply sound.

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CHAPTER THREE

METHODOLOGY

3.0 Introduction

This chapter explains in detail the methodology and components of this project

proposal. Each part and component that has been selected has as its own purpose

mostly focused on functionality and low cost. In this chapter as well, the technical plan,

analysis and the specifications are being explained.

3.1 System Block

Fig. 2.4.7. System Block

This block diagram shows us how the circuit will be split up into different sections.

When someone connect the supply voltage to the circuit and switched it on, the electric

signal are passed through the transistors that act as a switching devices where by the

siren is generated at first before sending the output to the speaker. The signal heard

from the speaker will be an increasing or decreasing tone depending on whether the

switch S1 is pressed or released.

Power

supply

Switch Transistors Siren Speak

er

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3.2 CIRCUIT DESIGN AND CIRCUIT OPERATION

Fig 2.4.8 Circuit Design and Circuit Operation

This circuit generates a tone that sounds very similar to a siren. The generator part of

the circuit is made of the combination of PNP and NPN transistors. Together, the two

transistors build up a free running multivibrator.

So to generate an up and down going signal tone, the resistor R2 is fed from an RC

circuit. When the switch S1 is pressed, the capacitor C1 charges via R1 slowly until it

reaches the maximum voltage level of 4 volts. This increasing voltage results to a

decreasing time constant at the R2/C3 junction. This furthermore results to an

increasing frequency of the multivibrator.

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After the switch S1 is released, the capacitor C1 discharges slowly resulting to a

decreasing frequency cycle. Through the combination of the two time constants a

sawtooth waveform is generated.

The signal heard from the speaker will be an increasing or decreasing tone depending

on whether the switch S1 is pressed or released.

The sound produced imitates the rise and fall of an American police siren. When first

switched on the 10u capacitor is discharged and both transistors are off. When the push

button switch is pressed to 10u capacitor will charge via the 22k resistor. This voltage is

applied to the base of the BC108B which will turn on slowly. When the switch is

released the capacitor will discharge via the 100k and 47k base resistors and the

transistor will slowly turn off. The change in voltage alters the frequency of the siren.

Oscillator action is as follows. As the BC108B transistor switches on its collector voltage

falls and so the 2N3702 transistor is switched on. This happens very quickly (less than

1us). The 22n capacitor will charge very quickly as well. As this capacitor is connected

between the collector of the 2N3702 and the base of the BC108B, it soon reaches

almost full supply voltage. The charging current for the capacitor is then much reduced

and the collector emitter voltage of the 2N3072 is therefore increased; the collector

potential will fall. This change in voltage is passed through the 22n capacitor to the

base of the BC108B causing it to come out of saturation slightly. As this happens its

collector voltage will rise and turn off the 2N3072 transistor more. This continues until

both transistors are off. The 22n capacitor will then discharge via the 100k, 22k

resistor, the closed push button switch, 9V battery, the speaker and 56 ohm resistor.

The discharge time takes around 5-6msec. As soon as the 22n capacitor is discharged,

the BC108B transistor will switch on again and the cycle repeats. The difference in

voltage at the collector of the BC108B (caused by the charging 10u capacitor) causes

the tone of the siren to change. As the 10u capacitor is charged, the tone of the siren

will rise, and as it is discharged, it will fall. A 64 ohm loudspeaker may be used in place

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of the 8 ohm and 56 resistor, and the values of components may be altered to produce

different sound effects.

Current drain is fairly high in this circuit so a suitable power supply is required. The

duration the tone takes to rise and fall is determined by the 10u and 22k resistor. These

values may be varied for different effects.

3.3 CIRCUIT DESIGN CALCULATIONS

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CHAPTER FOUR

RESULT AND DISCUSSION

A good way to start is to assemble all the components on a breadboard and connecting

all of them using jumper wires on the board. Power up the board using 9V DC power

supply and test the functionality of the circuit before proceeding to solder them onto

the PCB strip board.

During the practical implementation of the project, some of the values or components

had to be changed in order to get more accurate result. The circuit was first performed

on National Instrumentation software and only after successful implementation and

satisfied output.

In the output, an 8 ohms speaker is used for the siren sound.

A 9 volts power supply has been used instead of the 5 volts power supply to get

satisfied results.

The siren can be used in any type of alerting/warning device such as police siren,

emergency vehicle, schools etc.

The loudness is the most fundamental of the sound quality, and one that many other

sound quality metrics are based on. Loudness has been shown to have much better

correlation to human perception than simple A-weighting of the measured data. The

mechanical siren system has more loudness than the electrical siren, which would also

correspond to better perceptibility.

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CHAPTER FIVE

CONCLUSION AND RECOMMENDATION

5.1 CONCLUSION

It should be noted that the electrical system is replacing the mechanical siren due to

lower unit cost and reduced electrical power requirement for operation.

This finding can be adapted to similar characteristics such as perceived annoyance and

alerting nature, all of which are desirable characteristics for an emergency siren.

5.2 RECOMMENDATION

At this stage of the alert Development process, prototyping is primarily focused, but

there are some up and coming technologies that will be highly relevant to an industrial

implementation of the type of alerting mechanism that is design.

While it is evident this study attended to the goal of Designing an electronic siren,

opportunities for further research and work still exist. Future work on siren can be on;

Experimental testing of different mounting options of siren systems, i.e. outside

of the front grill, or height of the siren speaker.

Emergency Siren noise effect.

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REFERENCES

Max, Neuhaus (1991) Siren.

Douglas A. Riach (2003). Emergency vehicle siren noise.

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www.electronic hub.org

Appendix I:Budget

22

Table A1: Budget Table

Item Description Quantity Unit Price Amount

1 Resistors 6 500 Ugx 3,000 Ugx

2 Capacitors 5 1,000 Ugx 5,000 Ugx

3 Transistor BC 108BP 4 1,000 Ugx 4,000 Ugx

4 Battery 9V 1 5,000 Ugx 5,000 Ugx

5 Jumper wires 1 5,000 Ugx 5,000 Ugx

6 Speaker 2 5,000 Ugx 10,000 Ugx

7 Power switch 3 2,000 Ugx 2,000 Ugx

8 Miscellaneous 55,000 Ugx

TOTAL 93,000 Ugx