Article title: Design and Construction of Electric Doorbell

Authors: Icighan TORIKPA[1]

Affiliations: Physics Department, Federal University of Agriculture Makurdi, Benue State Nigeria[1]
Orcid ids: 0000-0002-1765-3337[1]
Contact e-mail: icighanikpa@gmail.com
License information: This work has been published open access under Creative Commons Attribution License
http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, distribution, and reproduction in any
medium, provided the original work is properly cited. Conditions, terms of use and publishing policy can be found at
https://www.scienceopen.com/.
Preprint statement: This article is a preprint and has not been peer-reviewed, under consideration and submitted to
ScienceOpen Preprints for open peer review.
DOI: 10.14293/S2199-1006.1.SOR-.PP6VMNU.v1
Preprint first posted online: 08 December 2022
 Design and Construction of Electric Door Bell

by

Icighan TORIKPA

Department of Physics, Federal University of Agriculture, Makurdi, Benue State, Nigeria.

1
Abstract

The purpose of the project is to design and construct an electric Doorbell based on the
principle of electromagnetism, powered and controlled by Arduino circuit board. The
aim of which is to bridge the gap between the old mechanical doorbell and the new
Arduino technology/circuit board being powered by a 12volt battery. On the successful
construction of the device, it was found to be very useful to the deaf and blind as the
LED component when activated, blinks and notifies the deaf at the presence of a
visitor or someone at the door. It is therefore highly recommended for homes and
offices with such disabilities.

2
 CHAPTER ONE

INTRODUCTION

1.1 Background of the study

A doorbell is a common and useful device used in every household. A doorbell is a

signalling device typically placed near a door. Most doorbells emit a ringing sound to

alert the occupant of the building to a visitor's presence when the visitor presses a

button. A doorbell is a signalling device typically placed near an entrance to a

building. When a visitor presses a button the bell rings inside the building, alerting the

occupant of the presence of the visitor.

This work is concerned with the modern doorbells which are electronic in nature. This

doorbell is basically divided into two components; the switch, normally placed near an

entrance to buildings and the ringing component placed inside buildings which gives

the signal when operated outside. The ringing component is comprised basically of an

electromagnet controlled by a microcontroller which shall replace the conventional

make and brake arrangement in the old doorbells. This arrangement shall strike a

balance between the old mechanical and conventional and modern electronic

doorbells.

Doorbells are supposed to be common features on buildings, but a few interaction and

observation reveals that contrary to the general conception, only few houses have it

and a very few have it and actually make use of it. The scarcity of doorbell on

buildings is traceable to the following factors; first that, they are not readily available

3
at electronic stores like other electronics such as radios, televisions and electric house

wares like sockets, switches, cables to mention a few. Hence the design and

production of this gadget and placing it in electronic shops shall make it readily

available for consumers to use. Secondly, the cost of installing one could be a factor

due to the economic nature of the country one may not see the necessity of installing

this common and simple feature. Hence the provision of a low cost doorbell will make

available this beautiful device in many homes. Lastly, the other possible reason why

doorbells are scarce could be due to its short life span and also the epileptic power

supply in the county by reason of their dependence on electricity. Therefore, the

production of a long lasting and battery dependent doorbell shall bridge this gap. It is

in the bid to salvage the afore mentioned problems that this project work becomes

timely.

The need for affordable doorbells is daily increasing due to large compounds and

complex buildings. This is because the distance between the entrances to building and

where the occupants are located are usually far apart that hand knocking most often

does not get the attention of the occupants of the house, hence the need for a simple

signalling device. More so, with the increase in electronic gadgets like televisions,

radios, phone and head phones, which produce a lot of noise thereby shutting people

completely out of what happens in their environment, doorbells can serve as devices

that will call attention to what happens outside the immediate surrounding particularly

when a visitor wishes to make an entry. This goes a long way to eliminate the fear of

many whose thought of visiting houses with gates gets them paranoid because of the

4
difficulty in getting the attention of those in the building they wish to go in, thereby

standing helpless at the entrance.

This project shall make use of the Arduino technology. John, (2013) explained that,

Arduino is a technology based on a printed circuit board (PCB) that is specifically

designed to use a microcontroller chip as well as other input and outputs. It also has

many other electronic components that are needed for the microcontroller to function

or to extend its capabilities. Massimo, (2011) noted that, prototyping is at the heart of

the Arduino way; he added that, objects are built to interact with other objects, people

and other networks, with the aim of finding simpler and faster ways to prototype in the

cheapest possible way. Thus the Arduino circuit board shall be used in this project to

regulate the functions of the components of the doorbell ranging from its ringing

frequency to the control of the LED system embedded in the doorbell.

1.2 Statement of the problem

This research work seeks to build a lasting, functional and low price doorbell

equipped with modern technology and useful for all kind of people. With addition of a

LED as an indicator on the doorbell, this project shall also be useful to the deaf who

over the years doorbells are meaningless to due to their inability to hear. It will also

synergise the old mechanical doorbells with modern Arduino technology. It shall also

use a 12volts battery which shall give it leverage over the modern once that use

electricity and will fail to function when there is power outage. That is, the

combination of electromagnet and microchip makes this doorbell unique since there is

none of such so far.

5
1.3 Aim and objectives of the study

The aim of this project is to design and construct electric doorbell. The objectives are

thus;

➢ To design and construct a doorbell using an electromagnet controlled by an

Arduino circuit board.

➢ To design and construct a doorbell that shall be useful to the deaf.

➢ To design and construct a low budget doorbell equipped with modern

technology.

➢ To design and construct a doorbell which shall consume a comparatively low

voltage.

➢ To add beauty to homes and offices by constructing and making available

affordable doorbells.

1.4 Significance of the study

The increase in electronic gadgets makes an electronic doorbell a welcome addendum

to the already existing ones. A fanciful and affordable doorbell shall not only serve the

purpose of alerting but will also add beauty to buildings of all kinds. This doorbell

will perfectly find its use in homes, commercial buildings, offices, hotels, hospitals

and studios. With increase in insecurity in the country and the world at large, a simple

doorbell as this can go a long way to checkmate intruders who will have to be

permitted before making an entrance, which by this time the house owners must have

been prepared to receive who ever will be coming in. In a little way this will also fight

the insecurity in the country.

6
Researchers wishing to carry out further studies in this area may design and construct

doorbell with a feedback system i.e. with a speaker embedded in the switch which

shall inform the visitor to come in or not. This will go a long way to eliminate the

stress of going to open the door or giving a loud shout which may not be heard.

Researchers can further add some security features such as cameras and infrared lights

to doorbells thereby increasing its sensitivity. This will give more details to who is

coming in thereby guaranteeing the security of lives and property.

1.5 The scope and limitation of the study

This project shall deal with the design and construction of an electric doorbell. This

work shall exclude doorbells with embedded security features or motion detectors

such as a camera, infrared or any of such features. It shall make use of an

electromagnet and a microcontroller built on an Arduino circuit board as its major

components.

The limiting factor to this project is time; the short time given for this work makes it

difficult to design and construct an elaborate gadget. More so, the little time allocated

places a great constraint in consulting the relevant personnel’s in other to do a more

trough work.

7
 CHAPTER TWO

REVIEW OF RELATED LITERATURES

2.1 Introduction

This review is carried out under the following headings; a brief history of magnets

shall be given, then electromagnets shall be considered and finally, microcontrollers

shall be discussed as they apply to this work.

2.2 Brief history of magnets

The history of magneto statics, like electrostatics, starts with the Greeks. According to

Jearl et al, (2008), the first known magnets were the lodestone, which have been

magnetised (made magnet) naturally. The fact that magnetic iron ore, sometimes

known as “lodestone", can attract pieces of iron was apparently known to Thales. He

thought that he had found the soul in the stone. The word “magnetism" comes from

the Greek town Magnesia, which is situated in an area rich in lodestone.

It took over 1500 years to turn Thales' observation into something useful. In the 11th

century, the Chinese scientist Shen Kuo realized that magnetic needles could be used

to build a compass, greatly improving navigation. The modern story of magnetism

begins from electrostatics, with William Gilbert. From the time of Thales, it had been

thought that electric and magnetic phenomena were related. One of Gilbert's important

discoveries was, ironically, to show that this is not the case: the electrostatic forces

and magneto static forces are different.

Yet over the next two centuries, suspicions remained. Several people suggested that

electric and magnetic phenomena were related, although no credible arguments were

8
given. The two just smelled alike. The following insightful quote from Henry Elles,

written in 1757 to the Royal Society, pretty much sums up the situation: “There are

some things in the power of magnetism very similar to those of electricity. But I do

not by any means think them the same". A number of specific relationships between

electricity and magnetism were suggested and all subsequently refuted by experiment.

Vesdara, (2013) noted that in the early days, electricity and magnetism were

considered to be totally separate. However, in 1820, the Danish scientist Hans

Christian Ørsted noticed that the needle on a magnet was deflected when a current was

turned on or off. After that, progress was rapid. Within months, Ørsted was able to

show that a steady current produces the circular magnetic field around a wire. In

September that year, Ørsted's experiments were reproduced in front of the French

Academy by Francois Arago, a talk which seemed to mobilise the country's entire

scientific community. First out of the blocks were Jean-Baptiste Biot and Felix Savart

who quickly determined the strength of the magnetic field around a long wire and the

mathematical law which bears their name.

Of those inspired by the Arago's talk, the most important was Andre-Marie Ampere.

Skilled in both experimental and theoretical physics, Ampere determined the forces

that arise between current carrying wires and derived the mathematical law which now

bears his name: B. dr = 0. He was also the first to postulate that there exists an atom of

electricity, what we would now call the electron. Ampere's work was published in

1827 a book with the catchy title “Memoir on the Mathematical Theory of

9
Electrodynamics Phenomena, Uniquely Deduced from Experience". It is now viewed

as the beginning of the subject of electrodynamics (David, 2016).

Furthermore, Maxwell’s equations, devised in 1863 represented the relationships

between electric and magnetic fields in the presence of electric charges and currents,

whether steady or rapidly fluctuating, in a vacuum or in matter. The equations

represent one of the most elegant and concise way to describe the fundamentals of

electricity and magnetism. They pull together in consistent way earlier results known

from the work of Gauss, Faraday, Ampère, Biot, Savart and others.

The laws are summarized thus; the first known as Gauss’ flux theorem shown in

equation 2.1, states that, the flux of electric field out of a closed region is proportional

to the total electric charge Q enclosed within the surface. This law relates an electric

field to the charge distribution that created it (Serway and Beichner, 2000).
𝜌
∇∙𝐸 = 2.1
𝜀

Where 𝜌= charge density

𝜀= permittivity in free space

The second is the Gauss’ law for magnetism: It states that the net magnetic flux out of

any closed surface is zero. Jearl et al, (2008) further asserts that the equation confirms

the fact that, the simplest magnetic structure that can exist is a magnetic dipole.

Magnetic monopoles do not exist. Therefore equation 2.2 is a formal way of saying

that magnetic monopoles do not exist.

∇∙𝐵 = 0 2.2

Where B= magnetic flux density

10
The third law as indicated in equation 2.3 is known as the Faraday's Law of Induction.

This Maxwell equation relates time varying magnetic fields to electric fields. Fisbane

et al, (1993) pointed out that, the minus sign is very important: it represents the fact

that the induced electric field were it not to act on charges, would give rise to an

induced current that opposes the charge in the magnetic flux (Len’s law) in other

words the electromotive force round a circuit is proportional to the rate of change of

flux of magnetic field through the circuit.

𝜕𝐵
∇×𝐸 =− 2.3
𝜕𝑡

Where B= magnetic flux density

E= electric field

t= time

The forth law known as the Amperes circuit law. Giambattista et al, (2004) explains

that, the changing electric fields as well as currents are sources of magnetic fields.

Magnetic field lines are still always closed loops, but the loops do not have to

surround currents; they can surround changing electric fields as well.

𝜕𝐸
∇×𝐵 =𝑗+ 2.4
𝜕𝑡

Where j= current density (Christopher, 2004).

2.3 Electromagnet

The Oxford dictionary of Physics, (2005) defines electromagnet as a magnet

consisting of a soft ferromagnetic core with a coil of insulated wire wound round it

such that when current flows through the wire the core becomes magnetized; when the

current ceases to flow the core loses its magnetization. An electromagnet consists of a

soft iron core in a current carrying solenoid. The magnetic field strength due to such a

11
solenoid is increased by the presence of the soft iron core or rod within the solenoid.

An electromagnet is a temporary magnet (Anyakoha, 2011).

A solenoid is a coil of wire with electric current flowing through it, giving it a

magnetic field, in other words it is a long, tightly wound helical coil of wire (Jearl et

al, 2008). The electromagnetic field of the solenoid magnetizes the iron bar by

aligning its magnetic domains. The combined magnetic force of the magnetized iron

bar and the wire coil makes an electromagnet very strong. In fact, electromagnets are

the strongest magnets made. Some of them are strong enough to lift a train. An

example is the maglev train which contains permanent magnets. Strong

electromagnets in the track repel the train magnets, causing the train to levitate above

the track.

Like a solenoid, an electromagnet is stronger if there are more turns in the coil or

more current is flowing through it. A bigger bar or one made of material that is easier

to magnetize also increases an electromagnet’s strength. Electromagnets are useful

because you can turn the magnet on and off by completing or interrupting the circuit,

respectively. This behaviour of electromagnets makes them an integral component of

an electric doorbell (Peter and Christopher, 2013).

The doorbell is a good example of how electromagnets can be used in applications

where permanent magnets just wouldn’t make any sense. When a guest pushes the

button on your front door, the electronic circuitry inside the doorbell closes an

electrical loop, meaning the circuit is completed and “turned on.” The closed circuit

allows electricity to flow, creating a magnetic field causing the clapper to become

12
magnetized. The hardware of most doorbells consists of a metal bell and metal clapper

that, when the magnetic charges it cause it to clang together, you hear the chime inside

and you can answer the door. The bell rings, the guest releases the button, the circuit

opens and the doorbell stops its ringing. Hair dryers, fans, CD players, telephones,

Particle accelerators and doorbells are examples of devices that make use of

electromagnets (Peter and Christopher, 2013).

2.4 Microcontrollers

2.4.0 What is a Microcontroller?

A microcontroller is a computer-on-a-chip, or, put in other words, a single-chip

computer. Micro suggests that the device is small, and controller tells you that the

device might be used to control objects, processes, or events. Another term to describe

a microcontroller is embedded controller, because the microcontroller and its support

circuits are often built into, or embedded in, the devices they control.

You can find microcontrollers in all kinds of things these days. Any device that

measures, stores, controls, calculates, or displays information is a candidate for

putting a microcontroller inside. The largest single use for microcontrollers is in

automobiles just about every car manufactured today includes at least one

microcontroller for engine control, and often more to control additional systems in the

car. In desktop computers, you can find microcontrollers inside keyboards, modems,

printers, and other peripherals. In test equipment, microcontrollers make it easy to add

features such as the ability to store measurements, to create and store user routines,

and to display messages and waveforms. Consumer products that use microcontrollers

13
include cameras, video recorders, compact-disk players, and ovens. And these are just

a few examples. (Jan Axelson, 1997)

Furthermore, a microcontroller is a self-contained system with peripherals, memory

and a processor that can be used as an embedded system (a combination of computer

hardware and software, and perhaps additional mechanical or other parts, designed to

perform a dedicated function (Jack, 2003). They are equipped with CPU, Memory and

I/O (input /output), timers and other on-chip periphery use for operating stand-alone.

They are design in particular for monitoring and or controlling tasks (Gunther &

Bettina, 2007). Most programmable microcontrollers that are used today are

embedded in other consumer products or machinery including phones, peripherals,

automobiles and household appliances such as; clocks, door locks, thermostat, air

conditional, remote and micro oven. They are also found in computer systems- Input

and output devices include solenoids, LCD displays, relays, switches and sensors for

data like humidity, temperature or light level, amongst others (John, 2008).

Some characteristics and uses of Microcontrollers are that they can be used for control

and measurements, does one task and runs one program continuously, they require

low power, they don’t have keyboard and monitor jacks and must use ports to perform

I/O. Microcontrollers are categorized into: 16 bit Digital Controller (DSC), 16 bit

General Purpose, 32 bit, and 8 bit.

14
2.4.1 Elements of a Microcontroller

Serial
ADC
Digital I/O

RAM

CPU
CORE

ROM

Parallel
Digital I/O Timers

Figure 1a. Block diagram of microcontroller elements

Central Processing Unit (CPU); The CPU, or central processing unit, executes

program instructions. Types of instructions include arithmetic (addition, subtraction),

logic (AND, OR, NOT), data transfer (move), and program branching (jump)

operations. An external crystal provides a timing reference for clocking the CPU. (Jan

Axelson, 1997).

Read Only Memory (ROM); A code of 4k memory is incorporated as on chip in

ROM in 8051microcontroller. The 8051 ROM is a nonvolatile memory, meaning that

its contents cannot be altered and hence has a similar range of data and program

memory, i.e, they can address program memory as well as a 64 separate block of data

memory (M. Akshay, 2013).

15
Random Access Memory (RAM); the 8051 microcontroller is composed of 128

bytes of internal RAM. This is a volatile memory since its contents will be lost if

power is switched off. These 128 bytes of internal RAM are divided into 32 working

registers which in turn constitute 4 register banks with each bank consisting of 8

registers. There are 128 addressable bits in the internal RAM (M. Akshay, 2013).

Input/output (I/O) Ports

Microcontrollers send and receive information to the outside world using ports Brian

Brammer & Susan Brammer (1991) has it that, I/O interface contains circuits to

control the peripheral devices and status of control registers which respectively enable

a program running in the CPU to, determine the state of the a device and control also

control a device.

The ability to directly monitor and control hardware is the main characteristic of

microcontrollers. As a consequence, practically all microcontrollers have at least 1-2

digital I/O pins that can be directly connected to hardware (within the electrical limits

of the controller). In general, you can find 8-32 pins on most controllers, and some

even have a lot more than that (like Motorola’s HCS12 with over 90 I/O pins). I/O

pins are generally grouped into ports of 8 pins, which can be accessed with a single

byte access. Pins can either be input only, output only, or most commonly,

bidirectional, that is, capable of both input and output. Apart from their digital I/O

capabilities, most pins have one or more alternate functions to save pins and keep the

chip small. All other modules of the controller which require I/O pins, like the analog

module or the timer, use in fact alternate functions of the digital I/O pins. The

application programmer can select which function should be used for the pin by

16
enabling the functionality within the appropriate module. Of course, if a pin is used

for the analog module, then it is lost for digital I/O and vice versa, so the hardware

designer must choose carefully which pins to use for which functions. In this section,

we will concentrate on the digital I/O capability of pins. Later sections will cover the

alternate functions. (Gunther. G & Bettina. W, 2007).

Power Supply Connectors

Power pins are used to distribute power to input and output where it’s needed. John

Davis, (2008), further stressed that; there are ground and power supply connections.

Ground is labeled VSS and is taken to define 0V. The supply connection is VCC. For

many years, the standard for logic was VCC =+5V but most devices now work from

lower voltages and a range of 1.8–3.6V is specified for the F2013. The performance of

the device depends on VCC. For example, it is unable to program the flash memory if

VCC < 2.2V and the maximum clock frequency of 16MHz is available only if VCC

≥3.3V.

Timers and Counters

Timers are typically constructed using a clock source and a counter. Counters count

clock periods that are input to them. John Davies (2008) stresses that, Clock is

essential for every synchronous digital system, basically the clock signal is a square

wave whose edges trigger hardware throughout the device so that the changes in

different components are synchronized. Clocks for microcontrollers used to be simple.

Usually a crystal with a frequency of a few MHz would be connected to two pins. It

would drive the CPU directly and was typically divided down by a factor of 2 or 4 for

the main bus. Unfortunately, the conflicting demands for high performance and low

17
power mean that most modern microcontrollers have much more complicated clocks,

often with two or more sources. In many applications the MCU spends most of its

time in a low-power mode until some event occurs, when it must wake up and handle

the event rapidly. It is often necessary to keep track of real time, either so that the

MCU can wake periodically (every second or minute, for instance) or to time-stamp

external events.

A.K Mukhopadhyay, (2007), stated that, this unit controls all internal and external

units of a microcontroller system. It makes the instruction to be fetched into

instruction register (IR) from the memory and decodes the instruction and then

controls the necessary internal and external units to realize the decoded instruction to

be executed. This operation is continued in a cyclic order so long as the power is on. It

also checks an input to the CPU that can directly alter the sequence of operation at the

hardware level. This type of input signals is termed as INTERRUPTS.

The Serial Ports

Jan Axelson, (1997), highlighted that; the serial port automatically takes care of many

of the details of serial communications. On the transmit side, the serial port translates

bytes to be sent into serial data, including adding start and stop bits and writing the

data in a timed sequence to SER OUT. On the receive side, the serial port accepts

serial data at SER IN and sets a flag to indicate that a byte has been received. BASIC-

52 uses the serial port for communicating with a host computer.

18
 CHAPTER THREE

MATERIALS AND METHODOLOGY

3.1 MATERIALS

The materials used in the construction of this doorbell are listed below;

S/N MATERIAL RATING

1 Arduino 5V

2 Resistor 10KΩ

3 Switch 0.5Ω

4 MOSFET Transistor IRF520

5 LED bulbs 2V

6 Battery 9V

7 Electromagnet 3.6Ω

3.2 METHODOLOGY

3.2.1 Power Supply

The power supply of this project consist of two 9 volts batteries; one the batteries

powers the Arduino circuit board, the outside component of the doorbell consisting of

three LED bulbs and a push button switch and the inside components of the doorbell

consisting of three LED bulbs and two push button switches. The second battery is

specifically used for powering the electromagnet. The separation of the batteries is to

help the doorbell function more efficiently thereby lengthening the battery effective

life span.

19
 9V battery Arduino Board Outside switch

9V battery Electromagnet

Figure 1: power supply block diagram

3.2.2 Arduino Circuit Board

Figure 2 the Arduino circuit board

The Arduino circuit board is basically made of; an Integrated Circuit (IC), capacitors,

microcontroller, USB port, resistors, transistors, power pins, digital pins, power

connector and a reset button. Arduino is an open source physical computing platform

based on a simple input/output (I/O) board and a development environment that

implements the processing language (Massimo, 2011). Hence the code that instructs

the circuit on what to do having been written is uploaded via the USB port into the

microcontroller which executes it as intended. Therefore, basically the Arduino is

20
composed of two major parts namely, the Arduino board which is a piece of hardware

you work on when you build your objects and the Arduino Integrated Development

Environment (IDE)- that is the piece of software that runs on the computer.

3.2.3 Explanation of the Arduino Circuit Board Sockets as used in the Project

The sockets on the Arduino board serves as an extension of the microcontroller pins;

how the pins were used in the design and construction of the doorbell are discussed

below;

Pin3. This sends signals to the RGB LED which is the ALERT. It turns it on

whenever the ring button is depressed. It shares the same pin with the outside

awareness button thereby working together whenever the ring button is HIGH

(depressed).

Pin4. Sends signals to the outside RED LED. It is turn ON whenever the inside button

is HIGH and OFF when in LOW state.

Pin5. This is connected to the outside GREEN LED. It comes on whenever the power

button (sw2) is in HIGH state indicating that the system is in ON.

Pin6. This is linked to the inside button. In its HIGH state it turns the inside RED

LED ON and the outside awareness RED LED ON.

Pin7. The inside RED LED receives signals from this pin. This pin turns the LED ON

when sw2 is turned ON.

Pin8. Linked to sw3, it causes the bell to ring whenever in HIGH state. It also turns

the inside alert LED i.e the RGB LED ON with the ORANGE LED on the outside.

Pin10. This is linked to the GATE lead of the transistor. It sets the transistor in HIGH

state whenever sw3 is HIGH.

21
Pin12. Serves as an attachment to the inside caution LED with red colour. It causes it

to glow whenever the sw2 is HIGH.

Pin5v. This pin supplies the inside and outside circuits of the doorbell with 5v each

for their operation. It also triggers the IRF 520 MOSFET on thereby causing the bell

to ring whenever the ring button sw3 is used.

Pin GND. This serves as the neutral pin for the inside and outside circuits of the

doorbell thereby completing the circuit.

3.2.4 MOSFET IRF 520 Transistor

Figure 3. MOSFET IRF 520 transistor diagram

This serves as a digital switch interfacing the Arduino board and the bell. This

transistor receives signals from the board through the GATE pin represented by 1

(Figure 3) .When sw3 is closed, this action sends 5volts to the transistor via SOURCE

pin represented by 3 thereby turning it ON. This causes the DRAIN and the SOURCE

to be closed hence completing the circuit thereby serving as the ground voltage to one

end of the coil, while the other end is connected directly to the positive terminal of the

9volts battery.

22
In this arrangement the MOSFET helps in communicating directly with the board and

the bell since the board can only supply a maximum of 5volts while the bell needs

about 9volts to function. This prevents the electromagnet from damaging the Arduino

board. Therefore the board triggers the MOSFET ON and OFF and serves as link in

supplying the bell with the 9volts it needs directly from a battery and still controlled

by the Arduino board as designed.

3.2.5 External Features of the Doorbell

OUTSIDE
INSIDE
ORANGE LED Sw2

RED LED RED LED RGB LED RED LED

GREEN LED
Sw1

Sw3

BATTERY

ˉ˗+

Figure 4. Block diagram of the doorbell showing its external features

The doorbell is made up of six Light Emitting Diodes (LED), with different colours

codes each symbolizing a particular state of the system, three switches (sw) and the

bell part with its electromagnet. The function of each LED is discussed below

23
according to their colours codes under the subheads; inside LED and outside LED

according to the design of the doorbell.

Inside LEDs

➢ Red LED 1; when ON indicates that the doorbell is on and ready for use and

when OFF means the doorbell is OFF.

➢ Red LED 2; when ON, it’s an indication that the system is set in a state that

visitors are not allowed to come in. It is therefore, synchronised with the

outside red LED. When OFF its indication that the occupants of the building

are ready to receive visitors on ringing the bell.

➢ Red, Green and Blue (RGB) LED; this works only when the outside ring

button is depressed, it also serves as an alert LED. Its signal the occupants of

the house who may have hearing impairment of the presence of somebody. It

produces different colours OF light thereby adding beauty to the apartment.

Outside LEDs

➢ Red LED; when on indicates that the occupants to such buildings are not

present.

➢ Green LED; its serves an indicator, symbolizing that the occupants are present.

➢ Orange LED; comes on whenever the ring button is depressed-It assures the

visitor that the doorbell is ringing.

24
3.2.6 Buttons/Switch

There are two buttons and a switch on the doorbell; one button on the outside and two

situated on the inside component of the doorbell labelled sw1, sw2 and sw3

respectively. They are discussed below;

➢ The outside push button switch (sw3) this is located on the outside component

of the doorbell when depressed it causes the bell to ring on the inside.

➢ Inside push button switch (sw2) is use for turning the system completely ON

or OFF.

➢ Inside push button switch (sw1) is use to set the red alert LED both inside and

outside ON or OFF state.

3.2.7 The Doorbell Electromagnet

Figure 5: Electromagnet showing the clockwise and anticlockwise wring

This component as seen in figure 5 consists of a coil wring round two soft iron cores.

On one of the irons the solenoid is worn clockwise and on the other anticlockwise

direction. This arrangement gives the two soft iron cores a north (N) and south (S)

polarity this is based on the fact that like poles repels while unlike poles attract.

Therefore, the two unlike poles produces a magnet that attracts the armature which

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carries a hammer on its other end. This hammer is attracted whenever the circuit is

closed thereby striking a metal gong positioned close to it thereby producing a ring

sound.

3.3 The Doorbell Mode of Operation

The doorbell works based on the concept of electromagnetism. The coil wrings on

two soft iron cores, one is connected to positive pole of the battery and the other end

connected to the adjuster positioned behind the armature (see figure 3). The armature

is constructed such that it is normally in contact with the adjuster. At the other end of

the armature a wire is connected to the LOAD lead of the MOSFET. Whenever the

outside switch three (sw3) is in HIGH state the Arduino board sends a signal to the

MOSFET thereby turning it on hence sending current through the electromagnet

circuit causing it to be a magnet temporarily. On becoming a magnet it attracts the soft

iron armature which strikes a metal gung attached close to it thereby producing sound.

In the cause of attraction the circuit is broken at its contact with the adjuster. This

causes the soft iron to lose its magnetic properties completely thereby returning to its

normal position and the same process of magnetization and demagnetization repeats

with each cycle producing ringing sound in a split of seconds.

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Conclusion and Recommendation

It was concluded that, doorbell is a necessary addendum to buildings, as it beautifies

and makes access to building more convenient. The constructed is also found to be

inclusive as the deaf were able to notice the presence of some one at the door when

the LED blinked. This project also made it possible for the harnessing of the old and

new technology. Therefore, the following recommendations are proposed:

i. The electric Doorbell should be placed in homes and offices with disabled

people particularly the deaf. The LED would notify the deaf of the presence

of a visitor at the door

ii. The electric doorbell is fancible hence they should be included as home

accessories

iii. The doorbell can be reconstructed and run by solar energy

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References:

A Dictionary of Physics (Oxford Paperback Reference) 5th (fifth) Edition published by

House U.S.A.

Jan Akelson (1997). The Microcontroller Idea book .Introduction to Microcontrollers

Courses 182.064 & 182.074 Vienna University of Technology Institute of

Computer Engineering Embedded Computing Systems Group February 26,

2007 Version 1.4 Gunther Gridling, Bettina Weiss

John Davies (2008). Microcontroller Basics

Jordan Hill, Oxford OX2 8DP, UK
Massimo Banzi(2011). Getting Started with Arduino Make Make:Books, Publishing

OUP Oxford (2005).

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