CHAPTER ONE

1.0 INTRRODUCTION

The basic function of a hand dryer is to dry hands using an electric source. Hand hygiene

is a very important aspect in preventing spread of communicable diseases. Since many disease-

caused by germs spread through touch, hand dryers were devised so that people can dry their

hands without actually touching the roll of towel available for common use in public restrooms.

Hand drying machines not only help in maintaining hygiene, but also help in reducing waste

produced by the use of towels.

Some years back, these devices were switched on using a button. When the button was

pressed, the device started blowing warm air for drying hands. But nowadays hand dryers have

infrared motion sensors installed in them. The device detects motion and automatically turns on

when hands are placed for drying. Similarly, it automatically turns off when hands are moved

away from the dryer, thereby preventing wastage of electricity.

Warm air is produced by a hand dryer using a heating coil made up of Nichrome, a hybrid of

chromium and nickel. The warm air is then blown out of the device through a tube or a vent

facing downwards. Hands are placed in the path of warm air coming out of hand dryer for

drying. The warmth and pressure of air coming out of the dryer is sufficient to evaporate water

from wet hands. First, the air pressure blows off water droplets from the hands and then the

warmth dries out the moisture from the hands. Traditional hand dryers need around 45 seconds to

dry hands, whereas new-age dryers take around 15 seconds to do this task. 

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1.1 STATEMENT OF THE PROBLEM

The transmission of bacteria and other micro-organisms is most likely to occur from wet

skin than from dry skin. Careful hand drying is a critical factor determining the level of touch-

contact associated bacterial transfer following hand washing. Hence, the proper drying of hands

should be an integral component of effective hand hygiene procedures in health care settings.

Cloth towel, paper towel and electric air hand dryer are commonly used to dry washed

hands. Although there is wide consensus that hand drying is an essential part of hand hygiene

process, there is much less consensus regarding the most effective method of hand drying in

terms of hand hygiene in health care settings.

1.2.1 SIGNIFICANCE OF THE STUDY

Hand dryers have been popular and more economical in many homes, hand dryers can

cut cost by 99.5% (for example a company may spend 500,000 per year on paper towels, where

as the hand dryer expenditure would be as low as 30,000 per year. This would vary due to cost of

towels .Also, due to the reduction in liter and waste in comparison with towels, which cannot be

recycled, hand dryers are also claimed to be better for the environment .

Hand dryers are more hygienic compared to a towel. It does not require close contact before

it commences its operation neither does it require washing after use.

1.3 OBJECTIVES OF THE STUDY

The objective of this project is to construct a machine that will automatically dries up the

wetness of a hand, when those hand are placed before it.

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1.3.1 SCOPE OF THE STUDY

The automatic hand drier is operated automatically using a sensor called light dependent

resistor (LDR). The LDR operates whenever it senses darkness or shadow in the absence of light.

The resistance of the LDR is reduced whenever it experiences darkness thereby allowing the

flow of electric current through it. Thus, this project is limited to a light dependent resistor, there

are other type of sensor used in the modification of an automatic hand drier.

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CHAPTER TWO

2.0 LITERATURE REVIEW

George Clemens invented the hand dryer. George Clemens a Chicago nature invented

the dryer in 1948. Over the years, the hand dryer as had minimal up-grades but some hand dryers

have been up-grade to no touch sensor. Clemens invention eliminated the nud to purchase towels

for the customers to dry their hands. In today’s society, the hand dryer as still efficient, however,

some consider the hand dryer to be not as hygiene as paper towel. George Clemens invention

uses a depressed button to operates, which produces more noise while it is pressed ON.

(Accessed from www.answers.yahoo.com on 18th of October,2013)

In 1991, Mitsubishi engineers set out to develop a solution to traditional hand dryers.

With land fill area scares in Japan, an effective hand dryer would significantly reduce waste

produced from restrooms and help lessen the environmental impact of hand drying. R and D

began testing new ideas for high speed hand drying, discovering that a minimum air speed of 134

is needed to blow water from hands. (Accessed from www.answers.yahoo.com on 18th of

October,2013)

In 1993, the first Jet Towel, JT-16A is released after experimenting with more than 50

different prototypes. Operating at 160watts the first Jet Towel introduces the world to the

concept of dual-Jet hand drying, but operates at an uncomfortable 71dB. After two years of

gathering feedback and testing new ideas, Mitsubishi release 3rd Jet-Towel JT-16c still at

900watts and 65dB, the JT-16c improves operating noise by eliminating high frequency sounds

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and improves water flow to drain tank. (Accessed from www.answers.yahoo.com on 18th of

October,2013)

The first hand dryers were not as efficient as the current models. Newer hand dryer have

infrared sensors and will not run if you do not have your hands under the sensor. This saves

energy over former models thus ran on a timer and were often left running after you we finished

drying your hands. Newer models also generates stream of air pressure that is higher than former

models, which can dry hands in much less time there by requiring less electricity. It was

developed by Denis Gagnon and was introduced into market in year 2001.(Accessed from

www.exceldryer.com on 18th of October, 2013).

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CHAPTER THREE

3.0 COMPONENTS ANALYSIS

3.1.1 TRANSFORMER

A transformer is a static electromagnetic device that transfers an electrical power from

one circuit to another without change of frequency. It accomplishes this by electromagnetic

induction and where the circuits are in mutual inductive influence of each other. A transformer

consists of a core and two or more windings coupled electromagnetically. There are primary

windings and secondary windings. The winding in which in which energy is delivered is known

as the primary winding while the winding to which energy is received is known as the secondary

winding. It is shown below.

FIG 3.1 AN IDEAL TRANSFORMER

WORKING PRINCIPLE OF A TRANSFORMER

A transformer works on the principle of mutual induction between two or more

inductively coupled coil .It consists of primary and secondary windings. When the primary

winding is energized by sinusoidal voltage, an alternating current flows in the primary winding.

The alternating current so produced in the primary winding set up an alternating magnetic flux in

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the core .The alternating flux link up the secondary winding thereby inducing e.m.f in the

secondary winding.

The type of transformer used in this project is a step-down transformer, which steps the

voltage from 220v to 12v.

3.1.2 RESISTOR

A resistor is an electric component that opposes and impedes the flow of electric

current .It is fabricated from a substance that is a poor conductor of electricity, such as carbon or

nichromes wires and serves to oppose the flow of electric current in a circuit

The type of resistor used in this project is a carbon resistor because of its ability to

withstand high energy pulses i.e. when current flows through the resistor, the entire carbon

composition body conducts. Resistors also serve the purpose of producing voltage drop and

dissipating heat in circuit.

A resistor is a passive two terminal electrical component that implements electrical

resistance as a circuit element. The current through a resistor is in direct proportion to the voltage

across the resistor’s terminal. This relationship is represented by ohm’s law, i.e.

I=V/R

Where I is the current through the conductor in units of amperes is the potential difference

measured across the conductor in units of volts and R is the resistance of the conductor in units

of ohm’s .It symbol is shown below.

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FIG. 3.2 SYMBOL OF A RESISTOR

3.1.2.1 TABLE SHOWING COLOUR CODE OF RESISTORS

COLOUR CODE

BLACK 0

BROWN 1

RED 2

ORANGE 3

YELLOW 4

GREEN 5

BLUE 6

VIOLET 7

GREY 8

WHITE 9

GOLD 5%

SILVER 10%

3.1.3 LIGHT DEPENDENT RESISTOR (LDR)

A light dependent resistor also known as photoresistor or photocell is a variable resistor

whose value of resistance decreases with increasing incident light intensity, i.e. it exhibits

photoconductivity.

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A photoresistor is made up of high resistance semi conductor, if light falling on the

device is of high frequency, photons absorbed by the semi conductor gives bund electrons

enough energy to jump into the conduction band. The resulting free electrons (and its hole

partner) conduct electricity, thereby lowering the resistance. The symbol is shown below.

FIG 3.3 SYMBOL OF LIGHT DEPENDENT RESISTOR

The variation of the resistance of a LDR with the intensity of the light falling o it is

illustrated in the graph below

High

RESISTANCE

FIG 3.4 GRAPH SHOWING VARIATION OF RESISTANCE OF LDR WITH LIGHT

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LIGHT

3.1.4 INTEGRATED CIRCUIT (IC)

An integrated circuit or monolithic is a set of electronic circuit on one plate or “chips” of

semi conductor material, normally silicon. This can be made much smaller than a discrete circuit

made from independent components.

Integrated circuit are used in virtually all electronics equipment today and have

revolutionized the world electronics. All integrated circuit is capable of producing accurate time

base, it can be made to produce one shot (monostable) or free running (astable).the configuration

employed in this project is the monostable.

All IC rely upon an external capacitor to determine the OFF and ON time interval of the

output pulses. Those times are clearly defined and can be calculated given the value of resistance

and capacitance. It symbol is shown below.

FIG 3.5 GRAPHICAL SYMBOL OF 555 TIMER

3.1.5 CAPACITOR

A capacitor is a device capable of storing electrical energy. In general, a capacitor

consists of two metal plates insulated from each other by a dielectric. The capacitance of a

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capacitor depends primarily upon the size, shape and relative permittivity of the medium

between the plates.

Also, they are used to store energy, passes high frequencies and reject low frequencies,

produce an a.c voltage drop and to introduce a time delay or phase difference. It takes a finite

period of time for a capacitor charge or discharge through a resistor. Assume that the capacitor is

initially discharged. When the switch is closed, the capacitor begins to charge through the

resistor. The voltage across the capacitor rises from zero up to the value of the applied

voltage .The type of capacitor used in this project is the electrolytic capacitor and it is used as a

filter in the circuit. It symbol is shown below.

FIG 3.6 SYMBOL OF A CAPACITOR

3.1.6 LIGHT EMITTING DIODE (LED)

This is a semi conductor light source which are used as indicator lamps in many

devices and are increasingly used for general lighting. It is a forward biased PN junction which

emits visible light when energized. The forward voltage across a LED is considerably greater

than silicon PN junction diode. The LED emits light in response to a sufficient forward current.

The amount of power output translated into light is directly proportional to the forward current.

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LED is used for different applications. Before it can be used for a particular

application, one or more of the following points have to be considered; wavelength of light

emitted, input power required, efficiency, mounting arrangement, light intensity and brightness.

It is used as power indicator in this project to show the presence of light in the circuit. It symbol

is shown below.

FIG 3.6 A SYMBOL OF LIGHT EMITTING DIODE

3.1.7 TRANSISTOR

This is an active semi conductor with three terminals which may be used as an

amplifier, detector or a switch. There are basically two types of a transistor, which are the bipolar

junction transistor (BJT) and the field effect transistor (FET).

The BJT is used in this project and it is shown below.

FIG 3.7 SYMBOL OF A BIPOLAR JUNCTION TRANSISTOR

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The terminals labeled B,C and E indicates the base, collector and the emitter respectively. There

are two types of bipolar junction transistor (BJT) arrangement and doping of their semi

conductor materials. These are the NPN and the PNP type.

3.1.8 DIODE

In electronics, a diode is a two terminal electronic component with asymmetric

conductance; it has low (ideally zero) resistance to current flow in one direction and high (ideally

infinite) resistance in the other. The most common function of a diode is to allow electric current

to flow in one direction (called diodes forward direction), while blocking current in the opposite

direction (reverse direction).

Thus a diode can be viewed as an electronic version of a check valve. This

unidirectional behavior is called rectification and is used to convert alternating current to direct

current. It symbol is shown below

FIG 3.8 SYMBOL OF A DIODE

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3.1.9 RELAY

A relay is an electrically operated switch. Many relays uses an electromagnet to operate

a switching mechanisms mechanically, but other operating principles are also used. Relays are

used where it is necessary to control a circuit by low a power signal (with complete electrical

isolation between control and controlled circuit), or where several circuits must be controlled by

one signal.

A simple electromagnetic relay consists of a coil of wire wrapped around a soft iron core, an iron

York which provides a low reluctance path for magnetic flux, a movable iron armature and one

or more sets of contacts. When an electric current is passed through the coil, it generates a

magnetic field that activates the armature and consequent movement of the movable contacts

either makes or breaks (depending upon construction) a connection with a fixed contact. The

symbol is shown below

FIG 3.9 SYMBOL OF A RELAY

3.1.10 HEATING ELEMENT

Heating elements are resistive conductors mostly made from nickel, an alloy of iron

whose working temperature is around 9500 c and can withstand high temperature for a long

period.

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Below are some of the requirements for a good heating element

1) It must be ductile

2) It must have mechanical strength

3) High specific resistance

4) High oxidizing temperature

5) Low temperature

It symbol is shown below

FIG 3.9.1 SYMBOL OF A HEATING ELEMENT

3.2 SPECIFICATION OF MATERIALS

ITEM

A

DESCRIPTION

POWER SUPPLLY

QUANTITY RATING

1 TRANSFORMER 1 220/12

2 DIODES 4 IN4001

3 CAPACITOR 1 4700f

B SENSOR STAGE

1 LIGHT DEPENDENT RESISTOR 1

2 VARIABLE RESISTORS 1 100k

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3 TRANSISTOR 2 BC 108

4 FIXED RESISTOR 5 4.7K, IK, 2.7K,

2.2K

C TIMER STAGE

1 RESISTOR 1 470K

2 CAPACITOR 2 100f, 0.1f

3 555 TIMER (I.C) 1

D SWITCHING STAGE

1 RESISTOR 3 10K, 1K, 33K

2 LIGHT EMITTING DIODE (LED) 1

3 TRANSITOR 1 BC 109

4 DIODE 1 1N4001

5 RELAY 1 12V

E MOTOR & ATING ELEMENT

STAGE

1 FAN 1 220V

2 HEATING ELEMENT 1 40W

FIG 3.9.2 COMPONENTS SPECIFICATION

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CHAPTER FOUR

4.0 CONSTRUCTION, TESTING AND PACKAGING

4.1 THE BLOCK DIAGRAM OF THE SYSTEM

In a simple term, a block diagram shows the basic electronic units and functions of a

device. The automatic hand drier is made up of five stages, these are as shown below:

FIG. 4.1 BLOCK DIAGRAM OF THE SYSTEM

4.2 POWER SUPPLY

Most electronic devices and circuits require direct voltage power supply .Obtaining direct

voltage is expensive using a battery; hence D.C is obtained from A.C(Alternative current) using

the process of verification. The block diagram of a d.c power supply is shown below:-

FIG. 4.2 BLOCK DIAGRAM OF A POWER SUPPLY

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POWER

STAGE

TIMER

STAGE

SENSOR

STAGE

SWITCHING

STAGE

MOTOR ANDELEMENT STAGE

SOURCE OR MAINS

SMOOTHING CIRCUIT

VOLTAGE REGULATION

LINE D.C

From the above diagram, the transformer steps down the a.c voltage from 240v to12v a.c.

The rectifier converts the a.c voltage to d.c and the process is shown :-

FIG. 4.3 FULLWAVE RECTIFICATION

The type of rectifier used in the circuit is the full wave rectifier.

The smoothing circuit minimizes the supply of the output voltage of a rectifier. This is

done using capacitors in parallel with a resistive load.

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4.2.2 SENSORY STAGES

This stage consist of light dependent resistor (LDR), variable resistor, fixed value resistor

and transistors .The major component in this stage is the LDR. When the LDR is covered, its

resistance increases and low current flows, this leads to a decrease in the voltage drop across the

variable resistor (100kw).The base of the transistor (TR1); which is converted to a high current

and made to feed the base of the next transistor (TR2) through a resistor. TR2 also converts the

high current to give a low collector current, which is below 1/3vce,is sufficient to trigger the pin

2 of the 555 timer in the next stage. The transistor used in this project is a npn bipolar transistor.

FIG 4.4 CIRCUIT DIAGRAM OF THE SENSOR STAGE

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4.2.3 TIMER STAGE

The timer stage is made up of the 555 timer resistor and capacitor. The 555 timer is

configured to give one shot (mono stable operation) by connecting external resistor and capacitor

to it. The schematic diagram is shown below.

FIG 4.5 MONOSTABLE CONFIGURATION OF 555 TIMER

The low voltage from the previous stage triggers the pin 2 of the 555 timer, thus causing

the device output to jump to the high level. The resistor and capacitor determine the duration at

which the system will remain in the ON state.

4.2.4 SWITCHING STAGE

The switching stage comprises of the transistor and resistor, high emitting diode ,rectifier

diode and a relay .The voltage from the output of the 555 timer is thereby making the base

current of transistor TR3 to be high. A high base current gives a low collector current, which

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switches ON the relay. The diode connected in parallel to the relay is to prevent reversal of the

current diagram is shown below:-

FIG. 4.6 CIRCUIT DIAGRAM OF SWITCHING STAGE

4.2.5 MOTOR AND HEATING ELEMENT STAGE

The motor and heating element are connected as shown below .The motor is mounted

above the heating element so that as the element heats up, the fan blows hot air from the hand.

The diagram is shown below.

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FIG. 4.7 COUPLED FAN WITH HEATING ELEMENT

4.2.6 CIRCUIT DIAGRAM OF AN AUTOMATIC HAND DRYER

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FIG. 4.8 CIRCUIT DIAGRAM OF AN AUTOMATIC HAND DRYER

4.3 TESTING

Various tests were carried out on the components using multi meter. These tests are as

follows:

The transformer was tested to determine its continuity using a multi meter.

The rectifier diodes were tested to verify the unidirectional flow of current and its

continuity using a multi meter.

The transistors were also tested to determine their terminals, types and whether they

were good or not using a multi meter.

The capacitors were also tested to determine their terminals using a multi meter.

The fan was run to ascertain whether it was free from stiffness.

4.3.1 ASSEMBLING

All the components used were assembled in an aluminum box. The dimension of the box

is 14 x 10 inches. The box is divided into three compartments. The upper compartment houses

Vero board, the left compartment houses the squirrel cage fan and the heating element. A

circular hole and an exhaust grill are provided beneath the box for the light dependent resistor

(LDR) and the heating element. Also, a small hole is provided on the front side for the LED.

4.3.2 TROUBLESHOOTING

The following are the common faults that can occur in the hand drier and the actions to

be carried out in order to rectify them.

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COMMON FAULTS RECTIFICATION

1 Device not working at all Check the power supply and all the

terminal connections.

2. Device not producing heat Check the LDR or the heating element for

possible break or relay

3. Fan not rotating Check the fan for stiffness or the relay

4.3.3 GENERAL PRECAUTION

1. Cover construction was made from aluminum for durability

2. All internal parts were plated with corrosion resistance material.

3. Components were mounted in a manner in which hazards such as an open circuit,

short circuit, were avoided.

4. I ensured that IC socket was mounted first and not the 555 timer

5. The heating element is suspended from the aluminum casing to prevent electric

shock.

4.3.4 MAINTAINANCE OF THE SYSTEM

1. The hand drier should be kept in a good environment, moist or damp environment should

be avoided.

2. Dust should be prevented from the electronic components by cleaning it up with a blower

on a monthly basis.

3. When used in an office environment, it should be isolated from power supply after

working hours.

4. Any fault should be traced using the circuit diagram of the system.

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CHAPTER FIVE

5.0 CONCLUSION AND RECOMMENDATION

5.1 CONCLUSION

The task of construction of the automatic hand drier was challenging and interesting.

It can be seen that the described circuit (Automatic hand drier) will operate when a user places

his hands in the direction zone and remains there for a short moment, but the drier will not

operate for an overly long period of time, which would waste power. Neither would the drier

operate in response to momentary or passing signals, but it will shut off if a user momentarily

removes his hands from detection zone. The objective of this project work was actually realized.

5.2 RECOMMENDATION

The automatic hand drier is recommended for us in academic environments, offices,

hotels, and eateries and residential home. This automatic hand drier is recommended for use in

Rector’s office. It is also recommended that more research should be carried out on the design

and construction of the hand drier so that a reduced size can be achieved.

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REFERENCE

Accessed from www.answers.yahoo.com on 18th of October,2013

Accessed from www.exceldryer.com on 18th of October, 2013

A.K and B.I (2005) A Textbook on Electrical Technology: published by S. Chad & Company

Ltd7361,Ram Niger,New Delhi-110055.

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