ACKNOWLEDGMENT

We dedicate our project to our Supervisor ......for his support and guidance that lead us to fulfill

our project. Than we dedicate our project to our parents who supported us throughout our

Educational career financially and morally

1

ABSTRACT

Under the Noise Control Ordinance, noise generated from industrial or commercial activities

should comply with the noise standards as stipulated in the relevant Technical Memorandum. It

is generally recognized that operation of ventilation systems is one of these noisy activities.

Our project highlights the importance of planning against noise problems. It gives a brief

description of potential noise problems associated with ventilation systems and provides

guidelines on practical noise control measures that are applicable for new designs and for

retrofitting existing designs. Therefore it is recommended to consult independent experts

throughout the process for ensuring the use of proper and cost effective noise control measures.

Our project is designed specially for real time applications like restaurant operators, building

operators and those ventilation contractors who do not have sufficient noise control knowledge.

2

TABLE OF CONTENTSACKNOWLEDGMENT.................................................................................................................1ABSTRACT....................................................................................................................................2TABLE OF CONTENTS................................................................................................................3Chapter 1..........................................................................................................................................5INTRODUCTION...........................................................................................................................5

1.1 ACOUSTICAL CHARACTERISTICS............................................................................61.2 Problem Statement............................................................................................................61.3 Proposed Solution.............................................................................................................61.4 Objective...........................................................................................................................61.5 SOUND AND NOISE......................................................................................................61.6 Principal of noise control..................................................................................................8

Chapter 2........................................................................................................................................10LITERATURE REVIEW..............................................................................................................10

2.1 Acoustics.........................................................................................................................102.2 Noise Control Mechanism..............................................................................................122.3 Acoustics/Filter Design and Implementation..................................................................13

Design....................................................................................................................................182.4 Temperature....................................................................................................................18

Chapter 3........................................................................................................................................21PROJECT DESIGN AND IMPLEMENTATION........................................................................21

3.1 Block Diagram................................................................................................................213.2 Methodology...................................................................................................................223.3 Circuit Design.................................................................................................................22

Chapter 4........................................................................................................................................25TOOLS AND TECHNIQUES.......................................................................................................25

4.1 Arduino Uno...................................................................................................................25Reset Button.........................................................................................................................28Power LED Indicator..........................................................................................................28TX RX LEDs........................................................................................................................29Main IC.................................................................................................................................29Voltage Regulator................................................................................................................29

4.2 Air Ducts.........................................................................................................................314.3 Resistor............................................................................................................................35

3

4.4 Solar Panel......................................................................................................................374.5 Gear DC motor................................................................................................................414.6 LM35...............................................................................................................................424.7 7805 IC...........................................................................................................................454.8 78L12 IC........................................................................................................................464.9 Capacitor.........................................................................................................................464.10 Mosfet..........................................................................................................................47

Chapter 5........................................................................................................................................49CONCLUSION..............................................................................................................................49REFERNCES.................................................................................................................................50

4

LIST OF ACRONYMS

IC Integrated Circuit

PCB Printed Circuit Board

LED Light emitting diode

AC Alternating Current

DC Direct Current

W.R.T With Respect To

VCC Voltage Source

GND Ground

 SPL sound pressure level

5

Chapter 1

INTRODUCTION

1.1 ACOUSTICAL CHARACTERISTICS

There are several acoustical characteristics that occupants typically notice when entering a space.

The first is often background noise, that is how loud or quiet a space is. Another is how

reverberant a space is. When there are surrounding occupied spaces, the noise isolation (or lack

thereof) provided by building assemblies can become apparent.

1.2 Problem StatementAs now a days Solar panels are most frequently used, but unfortunately there are is a very little

work done on dc fans and coolers and having no filters with such systems. That’s why we came

up with an idea to design our own prototype model. With filters and acoustic noise reduction

system. in our project we will design dc cooler system instead of ac. As ac coolers are already

there in market.

1.3 Proposed SolutionIn the conventional systems the ducting for the AC cooling plants/ room coolers is done in such

a way, that in room the ducts opening remain open all the time due to which the noise

continuously enters in room through those ducts. this problem can be solved if we make some

mechanical adjustments along with the noise reduction filters. We will make a filter to eliminate

the electrical noise generated in dc motor during the power mode operation. So will solve the

acoustic noise and electrical noise by the use of mechanical and electrical filter.

6

1.4 ObjectiveThe main objective of this project is to design such a system that will minimize the noise with

acoustic and electrical. Plus the desired system will also be capable of the automatic speed

control of the dc fan depending on the temperature.

1.5 SOUND AND NOISESound waves in air result from a physical disturbance of air molecules, such as when a truck

drives by a building or when guitar strings are plucked. Sound waves combine and reach a

listener via numerous direct and indirect pathways. The listener’s inner ear contains organs that

vibrate in response to these molecular disturbances, converting the vibrations into changing

electrical potentials that are sensed by the brain, allowing hearing to occur.

Acoustical analysis involves not only the sound source but also the listener and everything in

between on the path of the sound. The perception of the receiver can be influenced by the

treatment of either the path or the source. Some source sound is desirable, for example a

lecturer’s voice, and some source sound is undesirable, such as the sound output from an idling

truck outside a window. Undesirable sound is usually called noise. Unless it is a pure tone, a

sound wave is typically made up of vibrations at different frequencies. Like the impact of a stone

in a lake, ripples in the water are created that are analogous to sound in the air. The frequency is

basically the number of waves that pass a single point in one second, moving at the speed of

sound in air. One wave per second is a frequency of one hertz (Hz). A frequency of 1,000 hertz is

a kilohertz (kHz). Human speech contains frequencies between 200 Hz and 5 kHz, while the

human ear can actually hear sound generally between 25 Hz and 13 kHz, a wider range.

Frequencies below 20 Hz can be sensed as a vibration, though not audible to most people.

7

Sound and noise are described using a metric called the decibel. The decibel scale is logarithmic,

similar to the Richter scale used to describe seismic events, and translates a wide range of sound

pressure levels that affect the human ear to a logarithmic scale. The range of decibels most

commonly encountered in acoustics extends from 0 to 140 dB. correlates the sound pressure

levels of common sound sources to the logarithmic decibel scale.

1.6 Principal of noise controlThere are three basic elements in any noise control system, as illustrated in

1. The source of the sound

2. The path through which the sound travels

3. The receiver of the sound

In many situations, of course, there are several sources of sound, various paths for the sound, and

more than one receiver, but the basic principles of noise control would be the same as for the

more simple case. The objective of most noise control programs is to reduce the noise at the

receiver. This may be accomplished by making modifications to the source, the path, or the

receiver, or to any combination of these elements. The source of noise or undesirable sound is a

vibrating surface, such as a panel in an item of machinery, or small eddies with fluctuating

velocities in a fluid stream, such as the eddies in a jet stream leaving an air vent pipe. The path

for the sound may be the air between the source and receiver, as is the case for machinery noise

8

transmitted directly to the operator’s ears. The path may also be indirect, such as sound being

reflected by a wall to a person in the room. Solid surfaces, such as piping between a vibrating

pump and another machine element, may also serve as the path for the noise propagation. It is

important that the acoustic engineer identify all possible acoustic paths when considering a

solution for a noise problem.

9

10

Chapter 2

LITERATURE REVIEW

2.1 AcousticsAcoustics is the interdisciplinary science that deals with the study of all mechanical waves in

gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound. A

scientist who works in the field of acoustics is an acoustician while someone working in the field

of acoustics technology may be called an acoustical engineer. The application of acoustics is

present in almost all aspects of modern society with the most obvious being the audio and noise

control industries.

Hearing is one of the most crucial means of survival in the animal world, and speech is one of

the most distinctive characteristics of human development and culture. Accordingly, the science

of acoustics spreads across many facets of human society music, medicine, architecture,

industrial production, warfare and more. Likewise, animal species such as songbirds and frogs

use sound and hearing as a key element of mating rituals or marking territories. Art, craft,

science and technology have provoked one another to advance the whole, as in many other fields

of knowledge. Robert Bruce Lindsay's 'Wheel of Acoustics' is a well accepted overview of the

various fields in acoustics.

The word "acoustic" is derived from the Greek word ἀκουστικός (akoustikos), meaning "of or

for hearing, ready to hear" and that from ἀκουστός (akoustos), "heard, audible", which in turn

derives from the verb ἀκούω (akouo), "I hear".

The Latin synonym is "sonic", after which the term sonics used to be a synonym for acoustics

and later a branch of acoustics. Frequencies above and below the audible range are called

"ultrasonic" and "infrasonic", respectively.

11

Fundamental concepts of acoustics

Wave propagation: pressure levels

In fluids such as air and water, sound waves propagate as disturbances in the ambient pressure

level. While this disturbance is usually small, it is still noticeable to the human ear. The smallest

sound that a person can hear, known as the threshold of hearing, is nine orders of magnitude

smaller than the ambient pressure. The loudness of these disturbances is called the sound

pressure level (SPL), and is measured on a logarithmic scale in decibels.

Wave propagation: frequency

Physicists and acoustic engineers tend to discuss sound pressure levels in terms of frequencies,

partly because this is how our earsinterpret sound. What we experience as "higher pitched" or

"lower pitched" sounds are pressure vibrations having a higher or lower number of cycles per

second. In a common technique of acoustic measurement, acoustic signals are sampled in time,

and then presented in more meaningful forms such as octave bands or time frequency plots. Both

of these popular methods are used to analyze sound and better understand the acoustic

phenomenon.

The entire spectrum can be divided into three sections: audio, ultrasonic, and infrasonic. The

audio range falls between 20 Hz and 20,000 Hz. This range is important because its frequencies

can be detected by the human ear. This range has a number of applications, including speech

communication and music. The ultrasonic range refers to the very high frequencies: 20,000 Hz

and higher. This range has shorter wavelengths which allow better resolution in imaging

technologies. Medical applications such as ultrasonography and elastography rely on the

ultrasonic frequency range. On the other end of the spectrum, the lowest frequencies are known

as the infrasonic range. These frequencies can be used to study geological phenomena such as

earthquakes.

Analytic instruments such as the spectrum analyzer facilitate visualization and measurement of

acoustic signals and their properties. The spectrogram produced by such an instrument is a

12

graphical display of the time varying pressure level and frequency profiles which give a specific

acoustic signal its defining character.

Transduction in acoustics

A transducer is a device for converting one form of energy into another. In an electroacoustic

context, this means converting sound energy into electrical energy (or vice versa).

Electroacoustic transducers

include loudspeakers, microphones, hydrophones and sonar projectors. These devices convert a

sound pressure wave to or from an electric signal. The most widely used transduction principles

areelectromagnetism, electrostatics and piezoelectricity.

The transducers in most common loudspeakers (e.g. woofers and tweeters), are electromagnetic

devices that generate waves using a suspended diaphragm driven by an electromagnetic voice

coil, sending off pressure waves. Electret microphones and condenser microphones employ

electrostatics—as the sound wave strikes the microphone's diaphragm, it moves and induces a

voltage change. The ultrasonic systems used in medical ultrasonography employ piezoelectric

transducers. These are made from special ceramics in which mechanical vibrations and electrical

fields are interlinked through a property of the material itself.

2.2 Noise Control MechanismActive Noise control

Modifying and canceling sound field by electro-acoustical approaches is called active noise

control. There are two methods for active control. First by utilizing the actuators as an acoustic

source to produce completely out of phase signals to eliminate the disturbances. second method

is to use flexible and vibro-elastic materials to radiate a sound field interfering with the

disturbances and minimize the overall intensity. The latter method is called active structural

acoustic control (ASAC).

Passive Noise Control

Passive noise control refers to those methods that aim to suppress the sound by modifying the

environment close to the source. Since no input power is required in such methods, Passive noise

control is often cheaper than active control, however the performance is limited to mid and high

13

frequencies. active control works well for low frequencies hence, the combination of two

methods may be utilized for broadband noise reduction.

2.3 Acoustics/Filter Design and ImplementationAcoustic filters, or mufflers, are used in a number of applications requiring the suppression or

attenuation of sound. Although the idea might not be familiar to many people, acoustic mufflers

make everyday life much more pleasant. Many common appliances, such as refrigerators and air

conditioners, use acoustic mufflers to produce a minimal working noise. The application of

acoustic mufflers is mostly directed to machine components or areas where there is a large

amount of radiated sound such as high pressure exhaust pipes, gas turbines, and rotary pumps.

Although there are a number of applications for acoustic mufflers, there are really only two main

types which are used. These are absorptive and reactive mufflers. Absorptive mufflers

incorporate sound absorbing materials to attenuate the radiated energy in gas flow. Reactive

mufflers use a series of complex passages to maximize sound attenuation while meeting set

specifications, such as pressure drop, volume flow, etc. Many of the more complex mufflers

today incorporate both methods to optimize sound attenuation and provide realistic

specifications.

Basic filter design

For simple filters, a long wavelength approximation can be made to make the analysis of the

system easier. When this assumption is valid (e.g. low frequencies) the components of the

14

system behave as lumped acoustical elements. Equations relating the various properties are

easily derived under these circumstances.

The following derivations assume long wavelength. Practical applications for most conditions

are given later.

Low-pass filter

These are devices that attenuate the radiated sound power at higher frequencies. This means the

power transmission coefficient is approximately 1 across the band pass at low frequencies

where k is the wavenumber , L &   are length and area of expansion respectively, and S is the

area of the pipe.

The cut-off frequency is given by:

15

These are devices that attenuate the radiated sound power at lower frequencies. Like before, this

means the power transmission coefficient is approximately 1 across the band pass at high

frequencies (see figure to right).

High-pass filter

This is equivalent to a short side branch (see figure to right) with a radius and length much

smaller than the wavelength (lumped element assumption). This side branch acts like an acoustic

mass and applies a different acoustic impedance to the system than the low-pass filter. Again

using continuity of acoustic impedance at the junction yields a power transmission coefficient of

the form :

16

where a and L are the area and effective length of the small tube, and S is the area of the pipe.

The cut-off frequency is given by:

Band-stop filter

These are devices that attenuate the radiated sound power over a certain frequency range (see

figure to right). Like before, the power transmission coefficient is approximately 1 in the band

pass region.

Since the band-stop filter is essentially a cross between a low and high pass filter, one might

expect to create one by using a combination of both techniques. This is true in that the

combination of a lumped acoustic mass and compliance gives a band-stop filter. This can be

realized as a helmholtz resonator (see figure to right). Again, since the impedance of the

helmholtz resonator can be easily determined, continuity of acoustic impedance at the junction

can give the power transmission coefficient as:

These are devices that attenuate the radiated sound power over a certain frequency range (see

figure to right). Like before, the power transmission coefficient is approximately 1 in the band

pass region.

Since the band-stop filter is essentially a cross between a low and high pass filter, one might

expect to create one by using a combination of both techniques. This is true in that the

combination of a lumped acoustic mass and compliance gives a band-stop filter. This can be

realized as a helmholtz resonator (see figure to right). Again, since the impedance of the

helmholtz resonator can be easily determined, continuity of acoustic impedance at the junction

can give the power transmission coefficient as :

17

where  is the area of the neck, L is the effective length of the neck, V is the volume of the

helmholtz resonator, and S is the area of the pipe. It is interesting to note that the power

transmission coefficient is zero when the frequency is that of the resonance frequency of the

helmholtz. This can be explained by the fact that at resonance the volume velocity in the neck is

large with a phase such that all the incident wave is reflected back to the source .

The zero power transmission coefficient location is given by

18

Design

If the long wavelength assumption is valid, typically a combination of methods described above

are used to design a filter. A specific design procedure is outlined for a helmholtz resonator, and

other basic filters follow a similar procedure .

Two main metrics need to be identified when designing a helmholtz resonator :

1. Resonance frequency desired:   where  .

2. - Transmission loss:   based on TL level. This constant is found from a

TL graph (see HR pp. 6).

This will result in two equations with two unknowns which can be solved for the unknown

dimensions of the helmholtz resonator. It is important to note that flow velocities degrade the

amount of transmission loss at resonance and tend to move the resonance location upwards.

In many situations, the long wavelength approximation is not valid and alternative methods must

be examined. These are much more mathematically rigorous and require a complete

understanding acoustics involved. 

2.4 TemperatureThe prediction of the temperature distribution inside an operating electric motor is one of the

most important issues during its design. This prediction allows the engineer to evaluate if the

machine will reach the thermal class for which it is being designed, establishing the bearing

lubrication intervals as well as checking if the supplied air flow of the cooling system is

sufficient for ensuring normal motor operation at rated conditions.

It provides a means to estimate the impact voltage/frequency variation have on the winding

insulation life once the temperature change is determined. for every 10°C increase in winding

temperature, the expected thermal life of the winding is reduced by half. There may also be a

notable decrease in bearing lubricant life as operating temperature of the motor increases.

19

The main mechanisms of heat generation in induction electric motors are generally divided in

four groups, related mainly to the places where they occur. These are Joule losses, iron losses,

stray load losses and mechanical losses. Each

one of these kinds of energy conversion from electric to thermal energy is detailed below.

Joule Losses

This mechanism corresponds to the conversion of electric energy into thermal energy in

electrical conducting media.

This type of losses is directly related to the electric resistance of the conductor and changes

proportionally to the square

of the current, i.e., Pj = R*I². Energy conversion by Joule effect in squirrel cage induction

electric motors occurs in the stator (copper windings) and in the squirrel cage (aluminum bars).

Iron Losses

These losses are due to the conversion of electric energy into thermal energy in the iron. They

are divided in hysteresis and Foucault (eddy currents) losses. The eddy-current losses are Joule

losses that occur in the iron due to the flow of an induced electric current. The hysteresis losses

are due to the energy expended to align the iron magnetic poles to the applied magnetic field and

their order of magnitude corresponds to the area of the hysteresis loop in the electrical induction

(B) versus magnetic field (H) .

Stray load losses

The stray load losses are minor losses in the electric motor operation and their quantification is

very difficult. They include the losses due to the skin effect, high frequency, among others, that

are unknown or not easily quantified.

Mechanical losses

These losses comprise the conversion of the mechanical energy into thermal energy due to

mechanical friction and viscous losses. Here are included mainly the losses in the rolling

bearings (balls/rings interface) and the cooling fan losses. The cooling fan losses are due to the

mechanical energy required for blowing air over the motor surface, including the conversion of

air kinetic energy, flow work and viscous dissipation.

Contribution of Each Group

For the correct modeling, it is important to quantify the suitable value and location of the heat

generation. In general, the quantification of the losses is directly related to the location where

20

these losses occur in the electric motor, excepting the stray losses. the distribution of these losses

and the respective locations where they occur.

21

Chapter 3

PROJECT DESIGN AND IMPLEMENTATION

3.1 Block Diagram

22

controller "atmega328"

Filter

Temperature sensorlm35

Power

air duct

Dc Cooler Solar panel

3.2 MethodologyIn this project we will make a dc operated room cooler prototype model. We will provide the voltage

from the solar panel. Then a special filter will be designed to minimize the electrical noise due to the

involvement of other frequencies and will be used with a specially designed mechanical ducting. And

a temperature control system will be developed to keep the temperature constant.

3.3 Circuit Design

This is the circuit that we will start working with and will develop the program to check we if get the

desired output. It’s a 12V dc motor with current great then 4 ampere. That’s why we selected a high

ampere mosfet about 50A. as large current will be flowing through the mosfet so we will install a

heat sink. This mosfet will work together with the temperature “ lm35” the motor speed will vary

according the temperature . The Motor will be provided with the external source.

23

Chapter 4

TOOLS AND TECHNIQUES

4.1 Arduino UnoIntroduction

The Arduino microcontroller is an easy to use yet powerful single board computer. The Arduino is

open-source, which means hardware is reasonably priced and development software is free. The

Arduino project was started in Italy to develop low cost hardware for interaction design.

The ATmega328 microcontroller operating at 5 V with 2 Kb of RAM, 32 Kb of flash memory for

storing programs and 1 Kb of EEPROM for storing

parameters. The clock speed is 16 MHz, which translates to about executing about 300,000 lines of

C source code per second. The board has 14 digital I/O pins and 6 analog input pins.There is a

USB connector for talking to the host computer and a DC power jack for connecting an external 6-

20 V power source, for example a 9 V battery, when running a program while not connected to the

24

host computer. Headers are provided for interfacing to the I/O pins using 22 solid wire or header

connectors.

The Arduino programming language is a simplified version of C/C++. If you know C,

programming the Arduino will be familiar. If you do not know C, no need to worry as only a few

commands are needed to perform useful functions.

An important feature of the Arduino is that you can create a control program on the host PC,

download it to the Arduino and it will run automatically. Remove the USB cable connection to the

PC, and the program will still run from the top each time you push the reset button. Remove the

battery and put the Arduino board in a closet for six months. When you reconnect the battery, the

last program you stored will run. This means that you connect the board to the host PC to develop

and debug your program, but once that is done, you no longer need the PC to run the program.

What Does it Do?

The Arduino hardware and software was designed for artists, designers, hobbyists, hackers,

newbies, and anyone interested in creating interactive objects or environments. Arduino can

interact with buttons, LEDs, motors, speakers, GPS units, cameras, the internet, and even your

smart-phone or your TV! This flexibility combined with the fact that the Arduino software is free,

the hardware boards are pretty cheap, and both the software and hardware are easy to learn has led

to a large community of users who have contributed code and released instructions for

a huge variety of Arduino-based projects.

For everything from robots and a heating pad hand warming blanket to honest fortune-telling

machines, and even aDungeons and Dragons dice-throwing gauntlet, the Arduino can be used as

the brains behind almost any electronics project

What's on the board?

There are many varieties of Arduino boards (explained on the next page) that can be used for

different purposes. Some boards look a bit different from the one below, but most Arduinos have

the majority of these components in common:

25

Power (USB / Barrel Jack)

Every Arduino board needs a way to be connected to a power source. The Arduino UNO can be

powered from a USB cable coming from your computer or a wall power supply (like this) that is

terminated in a barrel jack. In the picture above the USB connection is labeled (1) and the barrel

jack is labeled (2).

The USB connection is also how you will load code onto your Arduino board. More on how to

program with Arduino can be found in our Installing and Programming Arduino tutorial.

NOTE: Do NOT use a power supply greater than 20 Volts as you will overpower (and thereby

destroy) your Arduino. The recommended voltage for most Arduino models is between 6 and 12

Volts.

Pins (5V, 3.3V, GND, Analog, Digital, PWM, AREF)

The pins on your Arduino are the places where you connect wires to construct a circuit (probably

in conjuction with abreadboard and some wire. They usually have black plastic ‘headers’ that

26

allow you to just plug a wire right into the board. The Arduino has several different kinds of pins,

each of which is labeled on the board and used for different functions.

GND (3): Short for ‘Ground’. There are several GND pins on the Arduino, any of which

can be used to ground your circuit.

5V (4) & 3.3V (5): As you might guess, the 5V pin supplies 5 volts of power, and the

3.3V pin supplies 3.3 volts of power. Most of the simple components used with the

Arduino run happily off of 5 or 3.3 volts.

Analog (6): The area of pins under the ‘Analog In’ label (A0 through A5 on the UNO)

are Analog In pins. These pins can read the signal from an analog sensor (like

a temperature sensor) and convert it into a digital value that we can read.

Digital (7): Across from the analog pins are the digital pins (0 through 13 on the UNO).

These pins can be used for both digital input (like telling if a button is pushed) and digital

output (like powering an LED).

PWM (8): You may have noticed the tilde (~) next to some of the digital pins (3, 5, 6, 9,

10, and 11 on the UNO). These pins act as normal digital pins, but can also be used for

something called Pulse-Width Modulation (PWM).

AREF (9): Stands for Analog Reference. Most of the time you can leave this pin alone.

It is sometimes used to set an external reference voltage (between 0 and 5 Volts) as the

upper limit for the analog input pins.

Reset Button

Just like the original Nintendo, the Arduino has a reset button (10). Pushing it will temporarily

connect the reset pin to ground and restart any code that is loaded on the Arduino. This can be

very useful if your code doesn’t repeat, but you want to test it multiple times. Unlike the original

Nintendo however, blowing on the Arduino doesn’t usually fix any problems.

Power LED Indicator

Just beneath and to the right of the word “UNO” on your circuit board, there’s a tiny LED next to

the word ‘ON’ (11). This LED should light up whenever you plug your Arduino into a power

source. If this light doesn’t turn on, there’s a good chance something is wrong. Time to re-check

your circuit!

27

TX RX LEDs

TX is short for transmit, RX is short for receive. These markings appear quite a bit in electronics

to indicate the pins responsible for serial communication. In our case, there are two places on the

Arduino UNO where TX and RX appear – once by digital pins 0 and 1, and a second time next

to the TX and RX indicator LEDs (12). These LEDs will give us some nice visual indications

whenever our Arduino is receiving or transmitting data (like when we’re loading a new program

onto the board).

Main IC

The black thing with all the metal legs is an IC, or Integrated Circuit (13). Think of it as the

brains of our Arduino. The main IC on the Arduino is slightly different from board type to board

type, but is usually from the ATmega line of IC’s from the ATMEL company. This can be

important, as you may need to know the IC type (along with your board type) before loading up

a new program from the Arduino software. This information can usually be found in writing on

the top side of the IC. If you want to know more about the difference between various IC’s,

reading the datasheets is often a good idea.

Voltage Regulator

The voltage regulator (14) is not actually something you can (or should) interact with on the

Arduino. But it is potentially useful to know that it is there and what it’s for. The voltage

regulator does exactly what it says – it controls the amount of voltage that is let into the Arduino

board. Think of it as a kind of gatekeeper; it will turn away an extra voltage that might harm the

circuit. Of course, it has its limits, so don’t hook up your Arduino to anything greater than 20

volts.

Installing the Software

This is the indication that you have all software and drivers successfully

installed and can start exploring with your own programs.

28

Troubleshooting

If there is a syntax error in the program caused by a mistake in typing, an error message will appear

in the bottom of the program window. Generally, staring at the error will reveal the problem. If you

continue to have problems, try these ideas

Run the Arduino program again

Check that the USB cable is secure at both ends.

Reboot your PC because sometimes the serial

Solderless Breadboards

A solderless breadboard is an essential tool for rapidly prototyping electronic circuits.

Components and wire push into breadboard holes. Rows and columns of holes are internally

connected to make connections easy. Wires run from the breadboard to the I/O pins on the Arduino

board. Make connections using short lengths of 22 g solid wire stripped of insulation about 0.25” at

each end. The pairs of horizontal runs at the top and bottom are useful for running power and

ground. Convention is to make the red colored run +5 V and the blue colored run Gnd. The power

runs are sometimes called “power busses”.

Flashing an LED

Light emitting diodes (LED's) are handy for checking out Arduino .For this task, we need an LED,

a 330 ohm resistor, and some short pieces of 22 or 24 g wire.Using 22 g solid wire, connect the 5V

power pin on the Arduino to the bottom red power bus on the breadboard and the Gnd pin on the

Arduino to the bottom blue power buss.

Arduino Hardware

The power of the Arduino is not its ability to crunch code, but rather its ability to interact with the

outside world through its input-output (I/O) pins. The Arduino has 14 digital I/O pins labeled 0 to

13 that can be used to turn motors and lights on and off and read the state of switches.Each digital

pin can sink or source about 40 mA of current. This is more than adequate for interfacing to most

devices, but does mean that interface circuits are needed to control devices other than simple

LED's. In other words, you cannot run a motor directly using the current available from an Arduino

pin, but rather must have the pin drive an interface circuit that in turn drives the motor.

29

A later section of this document shows how to interface to a small motor.To interact with the

outside world, the program sets digital pins to a high or low value using C code instructions, which

corresponds to +5 V or 0 V at the pin. The pin is connected to external interface electronics and

then to the device being switched on and off. The sequence of events is shown in this figure.

To determine the state of switches and other sensors, the Arduino is able to read the voltage

value applied to its pins as a binary number. The interface circuitry translates the sensor signal into

a 0 or +5 V signal applied to the digital I/O pin. Through a program command, the Ardiomp

interrogates the state of the pin. If the pin is at 0 V, the program will read it as a 0 or LOW. If it is

at +5 V, the program will read it as a 1 or HIGH. If more than +5 V is applied, you may blow out

your board, so be careful. The sequence of events to read a pin is shown in this figure.

Interacting with the world has two sides. First, the designer must create electronic interface

circuits that allow motors and other devices to be controlled by a low (1-10 mA) current signal that

switches between 0 and 5 V, and other circuits that convert sensor readings into a switched 0 or 5

V signal. Second, the designer must write a program using the set of Arduino commands that set

and read the I/O pins.

When reading inputs, pins must have either 0 or 5V applied. If a pin is left open or "floating", it

will read random voltages and cause erratic results. This is why switches always have a 10K pull

up resistor connected when interfacing to an Arduino pin.The Arduino also has six analog input

pins for reading continuous voltages in the range of 0 to 5 V from sensors such as potentiometers

Programming Concepts

A computer program is a sequence of step-by-step instructions for the computer to follow. The

computer will do exactly what you tell it to do, no more no less. The computer only knows what's

in the program, not what you intended. Thus the origin of the phrase, "Garbage in, garbage out".

4.2 Air DuctsDucts are used in heating, ventilation, and air conditioning (HVAC) to deliver and remove air. The

needed airflows include, for example, supply air, return air, and exhaust air.[1]Ducts commonly

also deliver ventilation air as part of the supply air. As such, air ducts are one method of ensuring

acceptable indoor air quality as well as thermal comfort.

30

A duct system is also called ductwork. Planning (laying out), sizing, optimizing, detailing, and

finding the pressure losses through a duct system is called duct design.

Materials

Ducts can be made out of the following materials:

Galvanized steel

Galvanized mild steel is the standard and most common material used in fabricating ductwork. For

insulation purposes, metal ducts are typically lined with faced fiberglassblankets (duct liner) or

wrapped externally with fiberglass blankets (duct wrap). When called for, a double walled duct is

used. This will usually have an inner perforated liner, then a 1–2" layer of fiberglass insulation

contained inside an outer solid pipe.

Rectangular ductwork commonly is fabricated to suit by specialized metal shops. For ease of

handling, it most often comes in 4' sections (or joints). Round duct is made using a continuous

spiral forming machine which can make round duct in nearly any diameter when using the right

forming die and to any length to suite, but the most common stock sizes range evenly from 4" to

24" with 6"-12" being most commonly used. Stock pipe is usually sold in 10' joints. There are also

5' joints of non-spiral type pipe available, which is commonly used in residential applications.

These are snapped together with a pipe-lock seam and uses a crimped and beaded small end (the

outlet of the direction of airflow) for connections.

Aluminium

Aluminium ductwork is lightweight and quick to install. Also, custom or special shapes of ducts

can be easily fabricated in the shop or on site.

The ductwork construction starts with the tracing of the duct outline onto the aluminium

preinsulated panel. The parts are then typically cut at 45°, bent if required to obtain the different

31

fittings (i.e. elbows, tapers) and finally assembled with glue. Aluminium tape is applied to all

seams where the external surface of the aluminium foil has been cut. A variety of flanges are

available to suit various installation requirements. All internal joints are sealed with sealant.

Aluminum is also used to make round spiral duct, but it is much less common than galvanized

steel.

Polyurethane and phenolic insulation panels (pre-insulated air ducts)

Traditionally, air ductwork is made of sheet metal which was installed first and then lagged with

insulation. Today, a sheet metal fabrication shop would commonly fabricate the galvanized steel

duct and insulate with duct wrap prior to installation. However, ductwork manufactured from rigid

insulation panels does not need any further insulation and can be installed in a single step.

Both polyurethane and phenolic foam panels are manufactured with factory applied aluminium

facings on both sides. The thickness of the aluminium foil can vary from 25 micrometres for

indoor use to 200 micrometres for external use or for higher mechanical characteristics. There are

various types of rigid polyurethane foam panels available, including a water formulated panel for

which the foaming process is obtained through the use of water and CO2 instead

of CFC, HCFC, HFC and HC gasses. Most manufacturers of rigid polyurethane or phenolic foam

panels use pentane as foaming agent instead of the aforementioned gasses.

A rigid phenolic insulation ductwork system is listed as a class 1 air duct to UL 181 Standard for

Safety.

Fiberglass duct board (preinsulated non-metallic ductwork)

Fiberglass duct board panels provide built-in thermal insulation and the interior surface

absorbs sound, helping to provide quiet operation of the HVAC system.

The duct board is formed by sliding a specially-designed knife along the board using a straightedge

as a guide. The knife automatically trims out a groove with 45° sides which does not quite

penetrate the entire depth of the duct board, thus providing a thin section acting as a hinge. The

duct board can then be folded along the groove to produce 90° folds, making the rectangular duct

shape in the fabricator's desired size. The duct is then closed with outward-clinching staples and

special aluminum or similar metal-backed tape.

Flexible ducting

Flexible ducts (also known as flex) are typically made of flexible plastic over a metal wire coil to

shape a tube. They have a variety of configurations. In the United States, the insulation is

32

usually glass wool, but other markets such as Australia, use both polyester fibre and glass wool for

thermal insulation. A protective layer surrounds the insulation, and is usually composed

of polyethylene or metalised PET. It is commonly sold boxes containing 25' of duct compressed

into a 5' length. It is available in diameters ranging from as small as 4" to as big as 18", but the

most commonly used are even sizes ranging from 6" to 12".

Flexible duct is very convenient for attaching supply air outlets to the rigid ductwork. It is

commonly attached with long zip ties or metal band claps. However, the pressure loss is higher

than for most other types of ducts. As such, designers and installers attempt to keep their installed

lengths (runs) short, e.g. less than 15 feet or so, and try to minimize turns. Kinks in flexible ducting

must be avoided. Some flexible duct markets prefer to avoid using flexible duct on the return air

portions of HVAC systems, however flexible duct can tolerate moderate negative pressures. The

UL181 test requires a negative pressure of 200 Pa.

Fabric ducting

This is actually an air distribution device and is not intended as a conduit for conditioned air. The

term fabric duct is therefore somehow misleading; fabric air dispersion systemwould be the more

definitive name. However, as it often replaces hard ductwork, it is easy to perceive it simply as a

duct. Usually made of polyester material, fabric ducts can provide a more even distribution and

blending of the conditioned air in a given space than a conventional duct system. They may also be

manufactured with vents or orifices.

Fabric ducts are available in various colours, with options for silk screening or other forms of

decoration, or in porous (air-permeable) and non-porous fabric. The determination which fabric is

appropriate (i.e. air-permeable or not) can be made by considering if the application would require

an insulated metal duct. If so, an air-permeable fabric is recommended because it will not

commonly create condensation on its surface and can therefore be used where air is supplied below

the dew point. Material that eliminates moisture may be healthier for the occupants. It can also be

treated with an anti-microbial agent to inhibit bacterial growth. Porous material also tends to

require less maintenance as it repels dust and other airborne contaminants.

Fabric made of more than 50% recycled material is also available, allowing it to be certified as

green product. The material can also be fire retardant, which means that the fabric can still burn,

but will extinguish when the heat source is removed.

33

Fabric ducts are not rated for use in ceilings or concealed attic spaces. However, products for use

in raised floor applications are available. Fabric ducting usually weighs less than other

conventional ducting and will therefore put less stress on the building's structure. The lower weight

allows for easier installation.

Waterproofing

The finish for external ductwork exposed to the weather can be sheet steel coated with aluminium

or an aluminium/zinc alloy, a multilayer laminate, a fibre reinforced polymer or other waterproof

coating.

4.3 ResistorIn an electronic circuit, the basic function of a resistor is to limit the current to a safe value so

that the associated sophisticated parts can function properly. Resistors come under passive

electronic components and are extensively used in electronic circuits. So important are these

components that it may be virtually impossible to build an electronic circuit without involving

resistors. Basically the function of a resistor is always to oppose the flow of current through it

and the strength of this opposition is termed as its resistance. German physicist, Sir G.S.

Ohms was able to discover a definite relationship between voltage, current and resistance.

According to him a potential difference or a voltage (V) across a resistor (R) is proportional to

the instantaneous current (I) flowing through it and is given as:

V = IR

Here R is the constant of proportionality and is known as the resistance of the resistor.

Function of Resistors in Electronics

In electronic circuits, resistors play an important role to limit the current and provide only the

required biasing to the vital active parts like the transistors and the ICs.

34

Transistor Biasing:

A transistor basically needs a small base voltage (>0.6) to make a large voltage flow through its

collector/ emitter terminals. But the base of a transistor is quite vulnerable to high currents, so a

resistor is incorporated here to limit the current and provide a safe biasing voltage.

The value of the base resistor of a transistor may be calculated through the below given formula:

R = (V – 0.6).Hfe / I,

Here V = source voltage to the base resistor, I = the collector load current, Hfe = forward gain of a

transistor (150 nominal) and 0.6 = minimum transistor biasing voltage.

LED Current Limit:

Just like transistors, LEDs too are very sensitive to high currents. A resistor when placed in series

with the LEDs regulates a proper flow of current through them. To calculate the value of a series

LED resistor, the following formula may be used:

R = V –( N.VLED)/ I

35

Here R = Series LED resistor, V = supply voltage, N = number of LEDs in series, V(LED)=

forward voltage of the LED used, and I = current through the LEDs (10mA optimum).

In Timing Circuits:

The timing components used in timer and oscillator circuits always incorporate a resistor and a

capacitor. Here the time taken to charge or discharge a capacitor constitutes the basic time pulse or

trigger for the circuit. A resistor is effectively used to control this charging and discharging process

and its value is varied to obtain different time intervals.

Surge Protection:

The initial switch ON of a power supply may at times inflict a dangerous voltage surge into an

electronic circuit, damaging its critical components. A resistor when introduced in series with the

supply terminals of the circuit helps in checking the sudden rise in voltage and averting a possible

harm. These resistors are generally of low values so that the over all performance of the circuit is

not affected.

4.4 Solar PanelPhotovoltaics is the direct conversion of light into electricity at the atomic level. Some materials

exhibit a property known as the photoelectric effect that causes them to absorb photons of light and

release electrons. When these free electrons are captured, an electric current results that can be

used as electricity.

36

The photoelectric effect was first noted by a French physicist, Edmund Bequerel, in 1839, who

found that certain materials would produce small amounts of electric current when exposed to

light. In 1905, Albert Einstein described the nature of light and the photoelectric effect on which

photovoltaic technology is based, for which he later won a Nobel prize in physics. The first

photovoltaic module was built by Bell Laboratories in 1954. It was billed as a solar battery and was

mostly just a curiosity as it was too expensive to gain widespread use. In the 1960s, the space

industry began to make the first serious use of the technology to provide power aboard spacecraft.

Through the space programs, the technology advanced, its reliability was established, and the cost

began to decline. During the energy crisis in the 1970s, photovoltaic technology gained recognition

as a source of power for non-space applications.

The selection of the PV panel took into consideration the input/output power requirements of the

system as well as the available budget. In order to provide 4 hours of run time at a 50 watt draw,

the panel would have to replenish the lost energy using 8 hours of daylight. Taking into

consideration cloud shadowing, panel positioning, and inherent conversion losses, a 20 watt panel

will optimally provide ~14 watts for 8 hours leading to a deficiency of 88 watts. The reserve

capacity of the main battery is 325 watts however after a few days it would have to be taken from

the field to a charging station. This is unsatisfactory and violates the requirement that the system be

self-sustaining.

The diagram above illustrates the operation of a basic photovoltaic cell, also called a solar cell.

Solar cells are made of the same kinds of semiconductor materials, such as silicon, used in the

microelectronics industry. For solar cells, a thin semiconductor wafer is specially treated to form

an electric field, positive on one side and negative on the other. When light energy strikes the solar

37

cell, electrons are knocked loose from the atoms in the semiconductor material. If electrical

conductors are attached to the positive and negative sides, forming an electrical circuit, the

electrons can be captured in the form of an electric current -- that is, electricity. This electricity can

then be used to power a load, such as a light or a tool.

A number of solar cells electrically connected to each other and mounted in a support structure or

frame is called a photovoltaic module. Modules are designed to supply electricity at a certain

voltage, such as a common 12 volts system. The current produced is directly dependent on how

much light strikes the module.

The PV panel is a simple electrical device and given any two of three variables, the

third variable. The three variables are panel temperature, panel voltage, and output current. The

peak power current varies with solar isolation and thus using the panel output current in a maximal

power point tracking (MPPT) algorithm would require sensing solar irradiance. This can be done,

but would require mounting multiple sensors on the panel to accurately measure the irradiance

onto the panel and would unnecessarily complicate the feedback controller.

Multiple modules can be wired together to form an array. In general, the larger the area of a

module or array, the more electricity that will be produced. Photovoltaic modules and arrays

38

produce direct-current (dc) electricity. They can be connected in both series and parallel electrical

arrangements to produce any required voltage and current combination.

Today's most common PV devices use a single junction, or interface, to create an electric field

within a semiconductor such as a PV cell. In a single-junction PV cell, only photons whose energy

is equal to or greater than the band gap of the cell material can free an electron for an electric

circuit. In other words, the photovoltaic

response of single-junction cells is limited to the portion of the sun's

spectrum whose energy is above the band gap of the absorbing

material, and lower-energy photons are not used.

One way to get around this limitation is to use two (or more) different cells, with more than one

band gap and more than one junction, to generate a voltage. These are referred to as

"multijunction" cells (also called "cascade" or "tandem" cells). Multijunction devices can achieve a

higher totalconversion efficiency because they can convert more of the energy spectrum of light to

electricity.

As shown below, a multijunction device is a stack of individual single-junction cells in descending

order of band gap (Eg). The top cell captures the high-energy photons and passes the rest of the

photons on to be absorbed by lower-band-gap cells.

39

4.5 Gear DC motorA gear motor is a specific type of electrical motor that is designed to produce high torque while

maintaining a low horsepower, or low speed, motor output. Gear motors can be found in many

different applications, and are probably used in many devices in our home.

Gear motors are commonly used in devices such as can openers, garage door openers, washing

machine time control knobs and even electric alarm clocks. Common commercial applications of

a gear motor include hospital beds, commercial jacks, cranes and many other applications that

are too many to list.

Basic Principles of Operation

A gear motor can be either an AC (alternating current) or a DC (direct current) electric motor.

Most gear motors have an output of between about 1,200 to 3,600 revolutions per minute

(RPMs). These types of motors also have two different speed specifications: normal speed and

the stall-speed torque specifications.

Gear motors are primarily used to reduce speed in a series of gears, which in turn creates more

torque. This is accomplished by an integrated series of gears or a gear box being attached to the

main motor rotor and shaft via a second reduction shaft. The second shaft is then connected to

the series of gears or gearbox to create what is known as a series of reduction gears. Generally

speaking, the longer the train of reduction gears, the lower the output of the end, or final, gear

will be.

An excellent example of this principle would be an electric time clock (the type that uses hour,

minute and second hands). The synchronous AC motor that is used to power the time clock will

usually spin the rotor at around 1500 revolutions per minute. However, a series of reduction

gears is used to slow the movement of the hands on the clock.

40

For example, while the rotor spins at about 1500 revolutions per minute, the reduction gears

allow the final secondhand gear to spin at only one revolution per minute. This is what allows the

secondhand to make one complete revolution per minute on the face of the clock.

Gear Motors and Increased Force

Gear motors are commonly used in commercial applications where a piece of equipment needs to

be able to exert a high amount of force in order to move a very heavy object. Examples of these

types of equipment would include a crane or lift Jack.

If you've ever seen a crane in action, you've seen a great example of how a gear motor works. As

you have probably noticed, a crane can be used to lift and move very heavy objects. The electric

motor used in most cranes is a type of gear motor that uses the basic principles of speed

reduction to increase torque or force.

Gear motors used in cranes are usually specialty types that use a very low rotational output speed

to create incredible amounts of torque. However, the principles of the gear motor used in a crane

are exactly the same as those used in the example electric time clock. The output speed of the

rotor is reduced through a series of large gears until the rotating, RPM speed, of the final gear is

very low. The low RPM speed helps to create a high amount of force which can be used to lift

and move the heavy objects.

4.6 LM35

The LM35 - An Integrated Circuit Temperature Sensor. The LM35 series are precision

integrated-circuit temperature devices with an output voltage linearly-proportional to the

Centigrade temperature. The LM35 device has an advantage over linear temperature sensors

calibrated in Kelvin, as the user is not required to subtract a large constant voltage from the

output to obtain convenient Centigrade scaling. The LM35 device does not require any external

calibration or trimming to provide typical accuracies of ±¼°C at room temperature and ±¾°C

over a full −55°C to 150°C temperature range. Lower cost is assured by trimming and calibration

at the wafer level. The low-output impedance, linear output, and precise inherent calibration of

the LM35 device makes interfacing to readout or control circuitry especially easy. The device is

used with single power supplies, or with plus and minus supplies. As the LM35 device draws

only 60 μA from the supply, it has very low self-heating of less than 0.1°C in still air. The LM35

41

device is rated to operate over a −55°C to 150°C temperature range, while the LM35C device is

rated for a −40°C to 110°C range (−10° with improved accuracy). The LM35-series devices are

available packaged in hermetic TO transistor packages, while the LM35C, LM35CA, and

LM35D devices are available in the plastic TO-92 transistor package. The LM35D device is

available in an 8-lead surface-mount small-outline package and a plastic TO-220 package.

Uses LM35s To Measure Temperature

You can measure temperature more accurately than a using a thermistor.

The sensor circuitry is sealed and not subject to oxidation, etc.

The LM35 generates a higher output voltage than thermocouples and may not require that

the output voltage be amplified.

Working of LM35

It has an output voltage that is proportional to the Celsius temperature.

The scale factor is .01V/oC

The LM35 does not require any external calibration or trimming and maintains an

accuracy of  +/-0.4 oC at room temperature and +/- 0.8 oC over a range of 0 oC to

+100 oC.

Another important characteristic of the LM35DZ is that it draws only 60 micro amps

from its supply and possesses a low self-heating capability. The sensor self-heating

causes less than 0.1 oC temperature rise in still air.

   The LM35 comes in many different packages, including the following.

TO-92 plastic transistor-like package,

T0-46 metal can transistor-like package

42

8-lead surface mount SO-8 small outline package

TO-202 package. (Shown in the picture above)

In this circuit, parameter values commonly used are:

Vc = 4 to 30v

5v or 12 v are typical values used.

Ra = Vc /10-6

Actually, it can range from 80 K to 600 K , but most just use 80 K.

Here is a photo of the LM 35 wired on a circuit board.

The white wire in the photo goes to the power supply.

Both the resistor and the black wire go to ground.

The output voltage is measured from the middle pin to ground.l

Features

Calibrated Directly in Celsius (Centigrade)

Linear + 10-mV/°C Scale Factor

43

0.5°C Ensured Accuracy (at 25°C)

Rated for Full −55°C to 150°C Range

Suitable for Remote Applications

Low-Cost Due to Wafer-Level Trimming

Operates from 4 V to 30 V

Less than 60-μA Current Drain

Low Self-Heating, 0.08°C in Still Air

Non-Linearity Only ±¼°C Typical

Low-Impedance Output, 0.1 Ω for 1-mA Load

4.7 7805 IC

The 7805 ic is three terminal positive voltage regulators is available with fixed output

voltages making them useful in a wide range of applications. This regulator is inexpensive, vise-

to-use devices suitable for a multitude of applications that require a regulated supply of up to

800 mA.It includes feature of internal current limiting and thermal shutdown making them

remarkably rugged. No external components are required with the 7805 devices in many

applications.These devices offer a substantial performance advantage over the traditional

zener diode-resistor combination, as output impedance and quiescent current are

substantionally reduced.The 7805 is available in 3-Pin plastic package SOT54 (Z),offers superior

quality and performance at low cost.

4.8 78L12 IC

44

This 7812 is fixed-voltage integrated-circuit voltage regulators is designed for a wide range of

applications. These applications include on-card regulation for elimination of noise and distribution

problems associated with single-point regulation. In addition, they can be used with power-pass

elements to make high-current voltage regulators. It can deliver up to 100 mA of output current.

7812 has built in over heat and short circuit protection which makes it a good choice for making

power supplies.If we hold the ic upside down (pins up) and the IC number is facing you then the left

pin will be the voltage regulator output, the center pin will be ground and the right pin will be the

voltage input pin. Under my experience, the maximum safe current you can get from one 7812 IC is

1A.

4.9 Capacitor

A capacitor (originally known as a condenser) is a passive two-terminal electrical

component used to store electrical energytemporarily in an electric field. The forms of practical

capacitors vary widely, but all contain at least two electrical conductors (plates) separated by

a dielectric (i.e. an insulator that can store energy by becoming polarized). The conductors can be

thin films, foils or sintered beads of metal or conductive electrolyte, etc. The nonconducting

dielectric acts to increase the capacitor's charge capacity. Materials commonly used as dielectrics

include glass, ceramic, plastic film, air, vacuum, paper, mica, and oxide layers. Capacitors are

widely used as parts of electrical circuits in many common electrical devices. Unlike a resistor,

an ideal capacitor does not dissipate energy. Instead, a capacitor stores energy in the form of

an electrostatic field between its plates.

45

When there is a potential difference across the conductors (e.g., when a capacitor is attached

across a battery), an electric fielddevelops across the dielectric, causing positive charge +Q to

collect on one plate and negative charge −Q to collect on the other plate. If a battery has been

attached to a capacitor for a sufficient amount of time, no current can flow through the capacitor.

However, if a time-varying voltage is applied across the leads of the capacitor, a displacement

current can flow.

4.10 Mosfet

When utilizing N-Channel MOSFETs to switch a DC voltage across a load, the drain terminals

of the high side MOSFETs are often connected to the highest voltage in the system. This creates

a difficulty, as the gate terminal must be approximately 10V higher than the drain terminal for

the MOSFET to conduct. Often, integrated circuit devices known as MOSFET drivers are

utilized to achieve this difference through charge pumps or bootstrapping techniques. These

chips are capable of quickly charging the input capacitance of the MOSFET (Cgiss) quickly

before the potential difference is reached, causing the gate to source voltage to be the highest

46

system voltage plus the capacitor voltage, allowing it to conduct. A diagram of an N- channel

MOSFET with gate, drain, and source terminals is shown in Figure 5

There are many MOSFET drivers available to power N-Channel MOSFETs through level

translation of low voltage control signals into voltages capable of supplying sufficient gate

voltage. Advanced drivers contain circuitry for powering high and low side devices as well as N

and P-Channel MOSFETs. In this design, all MOSFETs are N-Channel due to their increased

current handling capabilities. To overcome the difficulties of driving high side N-Channel

MOSFETs, the driver devices use an external source to charge a bootstrapping capacitor

connected between Vcc and source terminals. The bootstrap capacitor provides gate charge to the

high side MOSFET. As the switch begins to conduct, the capacitor maintains a potential

difference, rapidly causing the MOSFET to further conduct, until it is fully on. The name

bootstrap component refers to this process and how the MOSFET acts as if it is “pulling itself up

by its own boot strap”.

47

Chapter 5

CONCLUSION

There are several acoustical characteristics that occupants typically notice when entering a space.

The first is often background noise, that is how loud or quiet a space is. Another is how

reverberant a space is. When there are surrounding occupied spaces, the noise isolation (or lack

thereof) provided by building assemblies can become apparent. In this project make a dc

operated room cooler prototype model. We provide the voltage from the solar panel. Then a

special filter was be designed to minimize the electrical noise due to the involvement of other

frequencies and will be used with a specially designed mechanical ducting. And a temperature

control system will be developed to keep the temperature constant. So this project is succefully

completed.

48

REFERNCEShttp://www.learningaboutelectronics.com/Articles/LM741-op-amp-comparator.php

https://en.wikipedia.org/wiki/Acoustics

https://en.wikibooks.org/wiki/Engineering_Acoustics/

Sound_Absorbing_Structures_and_Materials

https://en.wikibooks.org/wiki/Acoustics/Filter_Design_and_Implementation

https://en.wikipedia.org/wiki/Duct_(flow)

49