This document provides an overview of basic electronics components used in embedded systems. It defines concepts like voltage, current, Ohm's law, and describes common electronic components such as resistors, capacitors, diodes, transistors, LEDs, LDRs, switches, relays, breadboards, crystal oscillators, and voltage regulators. These components are the basic building blocks that allow embedded systems to perform their dedicated functions through electronic circuits and interactions between hardware and software.

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Chapter 1
1 Introduction
1.1 Defining an Embedded System
An embedded system is a special-purpose computer system designed to perform one or a few
dedicated functions, often with real-time computing constraints. In contrast, a general-purpose
computer, such as a personal computer, can do many different tasks depending on
programming. Since the embedded system is dedicated to specific tasks, design engineers can
optimize it, reducing the size and cost of the product, or increasing the reliability and
performance.
According to the definition from IEEE: "an embedded computer system is a computer system
that is part of a larger system and performs some of the requirements of that system; for
example, a computer system used in an aircraft or rapid transit system".
EMBEDDED SYSTEM IN DAILY LIFE
Digital Clock Traffic Light
DVD Player Smart Phones
Fig 1.1 Examples of using Embedded Systems

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Physically, embedded systems range from portable devices such as digital watches and MP3
players to large stationary installations like traffic lights, factory controllers, or the systems
which control nuclear power plants. Complexity varies from low, with a single microcontroller
chip, to very high with multiple units, peripherals and networks mounted inside a large chassis
or enclosure.
In general, "embedded system" is not an exactly defined term, as many systems have some
element of programmability. For example, Handheld computers share some elements with
embedded systems — such as the operating systems and microprocessors which power them
— but are not truly embedded systems, because they allow different applications to be loaded
and peripherals to be connected.
Since the embedded system is dedicated to specific tasks, design engineers can optimize it to
reduce the size and cost of the product and increase the reliability and performance. Some
embedded systems are mass-produced, benefiting from economies of scale.
1.1.1 Characteristics-
 Embedded systems are designed to do some specific task, rather than be a general-
purpose computer for multiple tasks. Some also have real time performance constraints
that must be met, for reasons such as safety and usability; others may have low or no
performance requirements, allowing the system hardware to be simplified to reduce
costs.
 Embedded systems are not always standalone devices. Many embedded systems
consist of small, computerized parts within a larger device that serves a more general
purpose. For example, the Gibson Robot Guitar features an embedded system for
tuning the strings, but the overall purpose of the Robot Guitar is, of course, to play
music. Similarly, an embedded system in an automobile provides a specific function as
a subsystem of the car itself.

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1.2 Goals
An embedded system is a special-purpose computer system designed to perform one or a few
dedicated functions, often with real-time computing constraints. It is usually embedded as part
of a complete device including hardware and mechanical parts. In contrast, a general-purpose
computer, such as a personal computer, can do many different tasks depending on
programming.
Embedded systems control many of the common devices in use today. With the platform
provided by the semiconductor world in terms of Application processors and by the software
industry in terms of OS, Embedded Systems are becoming more and more powerful and cost
effective. As explained the domain of Embedded System is wide and thousands of embedded
applications do exist. But here we intend to focus on Embedded Systems which in near time
evolved more than forever and changed the way we see the world around us.
The aim of the report is to explore the field of Embedded Technology and develop systems
which fulfills three basic criteria: portability, scalability and performance.
1.3 Phases
Initially we will understand the basic electronics in Embedded Systems which is very
important. Basic components like resistor, capacitor, inductors, diode etc. will be described
here. Then we move through the controller part, i.e., Arduino.
Arduino which is a type of an embedded system runs on an 8-bit microcontroller. We
understand the basic concept behind developing the Arduino and will illustrate its features in
more detail. Its various boards and shields which are used by techies and hobbyist. We will
also see the interfacing of various electronics components and modules used with Arduino.
Later we will came to Raspberry Pi board solely called credit card size computer which runs
ARM based 32 bit processor.

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Chapter 2
2 Basic Electronics
Before getting into the world of embedded systems and its applications we need to go through
the basics of electronics which are responsible for the driving all these things. We will also see
the different components related to the embedded systems and which are mostly used in it.
2.1 Voltage
Voltage, electric potential difference, electric pressure or electric tension (denoted ∆V or ∆U)
is the difference in electric potential energy between two points per unit electric charge. The
voltage between two points is equal to the work done per unit of charge against a static
electric field to move the charge between two points, described in volts.[1]
Voltage can be caused by static electric fields, by electric current through a magnetic field,
by time-varying magnetic fields, Voltage is electric potential energy per unit charge,
measured in joules per coulomb (volts).
In general terms, we can also say that voltage is the force applied on the electrons which is
responsible for their movement inside a conducting material.
2.1 Batteries are sources of voltage in many electric circuits

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2.2 Current
An electric current is a flow of electric charge. In electric circuits this charge is often carried
by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions
and electrons such as in a plasma.
The SI unit for measuring an electric current is the ampere, which is the flow of electric
charge across a surface at the rate of one coulomb per second.
The particles that carry the charge in an electric current are called charge carriers. In metals,
one or more electrons from each atom are loosely bound to the atom, and can move freely
about within the metal. These conduction electrons are the charge carriers in metal conductors.
Fig 2.2 Flow of Electrons in a wire.
current in a wire or component can flow in either direction, when a variable I is defined to
represent that current, usually by an arrow on the circuit schematic diagram. This is called the
reference direction of current I. If the current flows in the opposite direction, the variable I has
a negative value.
2.3 Ohm’s law
Ohm's law states that the current through a conductor between two points is directly
proportional to the potential difference across the two points. Introducing the constant of
proportionality, the resistance, one arrives at the usual mathematical equation that describes
this relationship:

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where I is the current through the conductor in units of amperes, V is the potential difference
measured across the conductor in units of volts, and R is the resistance of the conductor in
units of ohms. More specifically, Ohm's law states that the R in this relation is constant,
independent of the current.
2.4 Resistor
A resistor is a two-terminal electrical or electronic component that opposes an electric current
by producing a voltage drop between its terminals in accordance with Ohm's law:
“The electrical resistance is equal to the voltage drop across the resistor divided by the current
through the resistor while the temperature remains the same. Resistors are used as part of
electrical networks and electronic circuits.”
Fig 2.3 Carbon Composition Resistors
2.5 Capacitor
A capacitor is an electrical/electronic device that can store energy in the electric field between
a pair of conductors (called "plates"). The process of storing energy in the capacitor is known
as "charging", and involves electric charges of equal magnitude, but opposite polarity, building
up on each plate.[2]

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Capacitors are often used in electric and electronic circuits as energy-storage devices. They
can also be used to differentiate between high-frequency and low-frequency signals. This
property makes them useful in electronic filters.
2.5.1 Capacitor types
Fig 2.4
Capacitors: SMD ceramic, SMD tantalum, and electrolytic at bottom right.
Fig 2.5
Various types of capacitors. From left: multilayer ceramic, ceramic disc, multilayer polyester
film, tubular ceramic, polystyrene, metallized polyester film, aluminum electrolytic. Major
scale divisions are cm.
2.6 Diode
In electronics, a diode is a two-terminal electronic component that conducts primarily in one
direction it has low (ideally zero) resistance to the flow of current in one direction, and high
(ideally infinite) resistance in the other. A semiconductor diode, the most common type today,
is a crystalline piece of semiconductor material with a p–n junction connected to two electrical

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terminals. A vacuum tube diode has two electrodes, a plate (anode) and a heated cathode.
Semiconductor diodes were the first semiconductor electronic devices.[4]
The most common function of a diode is to allow an electric current to pass in one direction
(called the diode's forward direction), while blocking current in the opposite direction (the
reverse direction). This unidirectional behavior is called rectification, and is used to convert
alternating current to direct current, including extraction of modulation from radio signals in
radio receivers—these diodes are forms of rectifiers.
Fig 2.6 Electronic symbol for Diode
2.7 Crystalline diode Fig 2.8 Diodes with different
sizes and shapes
2.7 LED
A light-emitting diode (LED) is a two-lead semiconductor light source. It is a p–n junction
diode, which emits light when activated. When a suitable voltage is applied to the leads,
electrons are able to recombine with electron holes within the device, releasing energy in the

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form of photons. This effect is called electroluminescence,[5] and the color of the light
(corresponding to the energy of the photon) is determined by the energy band gap of the
semiconductor.
Fig 2.9 Electronic symbol of LED
Fig 2.10 Internal parts of an LED
Appearing as practical electronic components in 1962, the earliest LEDs emitted low-intensity
infrared light. Infrared LEDs are still frequently used as transmitting elements in remote-
control circuits, such as those in remote controls for a wide variety of consumer electronics.
LEDs have allowed new text, video displays, and sensors to be developed, while their high
switching rates are also used in advanced communications technology.
2.8 Transistor
A transistor is a semiconductor device used to amplify or switch electronic signals and
electrical power. It is composed of semiconductor material with at least three terminals for
connection to an external circuit. A voltage or current applied to one pair of the transistor's

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terminals changes the current through another pair of terminals. Because the controlled
(output) power can be higher than the controlling (input) power, a transistor can amplify a
signal. Today, some transistors are packaged individually, but many more are found embedded
in integrated circuits.
Fig 2.11 Transistors in different sizing.
The transistor is the fundamental building block of modern electronic devices. It was founded
in 1947 by American physicists John Bardeen, Walter Brattain, and William Shockley, the
transistor revolutionized the field of electronics, and paved the way for smaller and cheaper
radios, calculators, and computers, among other things. The transistor is on the list of IEEE
milestones in electronics. The transistor's low cost, flexibility, and reliability have made it a
ubiquitous device. Transistorized mechatronic circuits have replaced electromechanical
devices in controlling appliances and machinery.
Fig 2.12 Transistor terminals(C,B,E)

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It is often easier and cheaper to use a standard microcontroller and write a computer program
to carry out a control function than to design an equivalent mechanical control function.
2.9 LDR
A Photoresistor or light-dependent resistor (LDR) or photocell is a light-controlled variable
resistor. The resistance of a Photoresistor decreases with increasing incident light intensity; in
other words, it exhibits photoconductivity. A Photoresistor can be applied in light-sensitive
detector circuits, and light- and dark-activated switching circuits.
Fig 2.13 LDR
Fig 2.14 Electronic symbol for LDR
A Photoresistor is made of a high resistance semiconductor. In the dark, a Photoresistor can
have a resistance as high as several megohms (MΩ), while in the light, a Photoresistor can
have a resistance as low as a few hundred ohms. If incident light on a Photoresistor exceeds a
certain frequency, photons absorbed by the semiconductor give bound electrons enough energy

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to jump into the conduction band. The resulting free electrons (and their hole partners) conduct
electricity, thereby lowering resistance.
2.10 Switch
A switch is an electrical component that can break an electrical circuit, interrupting the current
or diverting it from one conductor to another. The mechanism of a switch may be operated
directly by a human operator to control a circuit (for example, a light switch or a keyboard
button), may be operated by a moving object such as a door-operated switch, or may be
operated by some sensing element for pressure, temperature or flow. Switches are made to
handle a wide range of voltages and currents; very large switches may be used to isolate high-
voltage circuits in electrical substations.
An electrical switch is any device used to interrupt the flow of electrons in a circuit. Switches
are essentially binary devices: they are either completely ON or completely OFF.
Fig 2.15 Switch Symbol
Fig 2.16 Electrical and Push Button Switches

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2.11 Relay
A relay is simply a switch that is activated by an electromagnet. You apply power to the coil
of the electromagnet and the movement of a part called the armature is made to close or open
one or more sets of contacts. They are often used to isolate two circuits electrically in a circuit.
Relay is an electromagnetic device which is used to isolate two circuits electrically and connect
them magnetically. They are very useful devices and allow one circuit to switch another one
while they are completely separate. They are often used to interface an electronic circuit
(working at a low voltage) to an electrical circuit which works at very high voltage. For
example, a relay can make a 5V DC battery circuit to switch a 230V AC mains circuit.
Fig 2.17 A 5-Pin Relay and its Internal structure.
Fig 2.18 Relay with its contacts

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In a basic relay there are three contactors: normally open (NO), normally closed (NC) and
common (COM). At no input state, the COM is connected to NC. When the operating voltage
is applied the relay coil gets energized and the COM changes contact to NO.
The Relay we are using here is called 5-pin Relay. This can also be seen from the images
uploaded, as when no voltage is applied COM is connected to NC. But when supply is applied
then due to magnetic field produced by the coil COM gets connected to NO.
2.12 Breadboard
A breadboard is a construction base for prototyping of electronics. Originally it was literally a
bread board, a polished piece of wood used for slicing bread. In the 1970s the solderless
breadboard (AKA plugboard, a terminal array board) became available and nowadays the term
"breadboard" is commonly used to refer to these. "Breadboard" is also a synonym for
"prototype".
A breadboard is a solderless device for temporary prototype with electronics and test circuit
designs. Most electronic components in electronic circuits can be interconnected by inserting
their leads or terminals into the holes and then making connections through wires.
Fig 2.19
Solderless breadboard with 400 connection points and its hole pattern.
The breadboard most commonly used today is usually made of white plastic and is a pluggable
(solderless) breadboard. It was designed by Ronald J. Portugal of EI Instruments Inc. in 1971

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2.13 Crystal Oscillator
A miniature 4 MHz quartz crystal enclosed in a hermetically sealed HC-49/US package, used
as the resonator in a crystal oscillator.
A crystal oscillator is an electronic circuit that uses the mechanical resonance of a vibrating
crystal of piezoelectric material to create an electrical signal with a very precise frequency.
This frequency is commonly used to keep track of time (as in quartz wristwatches), to provide
a stable clock signal for digital integrated circuits, and to stabilize frequencies
Fig 2.20 C-49 package quartz crystal
2.14 Voltage Regulator
A voltage regulator is an electrical regulator designed to automatically maintain a constant
voltage level. It may use an electromechanical mechanism, or passive or active electronic
components. Depending on the design, it may be used to regulate one or more AC or DC
voltages.
A 5V voltage regulator (7805) is used to ensure that no more than 5V is delivered in the output
load regardless of the voltage present at the input terminal (provided that voltage is less than
12VDC). The regulator functions by using a diode to clamp the output voltage at 5VDC
regardless of the input voltage - excess voltage is converted to heat and dissipated through the
body of the regulator. If a DC supply of greater than 12V is used, excessive heat will be

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generated, and the system may be damaged. If a DC supply of less than 5V is used, insufficient
voltage will be present at the regulators output.
Fig 2.21 7805 IC
If a power supply provides a voltage higher than 7 or 8 volts, the regulator must dissipate
significant heat. The "fin" on the regulator body (the side that protrudes upward beyond the
main body of the part) helps to dissipate excess heat more efficiently. If the board requires
higher currents, then the regulator may need to dissipate more heat. In this case, the regulator
can be secured to the circuit board by fastening it with a screw and nut (see below). By securing
the regulator tightly to the circuit board, excess heat can be passed to the board and then
radiated away.
Fig 2.22 Heat Sink
2.15 Printed circuit board

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A Printed Circuit Board, or PCB, is used to mechanically support and electrically connect
electronic components using conductive pathways, or traces, etched from copper sheets
laminated onto a non-conductive substrate. Alternative names are printed wiring board (PWB),
and etched wiring board.
Fig 2.23
A populated PCB, showing the conductive trace and mounted electrical components.
A PCB populated with electronic components is a printed circuit assembly (PCA), also known
as a printed circuit board assembly (PCBA).
PCBs are rugged, inexpensive, and can be highly reliable. They require much more layout
effort and higher initial cost than either wire-wrapped or point-to-point constructed circuits,
but are much cheaper and faster for high-volume production.
2.16 Microcontrollers & Microprocessors
2.16.1 Microcontroller- A microcontroller is a small computer on a single integrated
circuit containing a processor core, memory, and programmable input/output peripherals.
Program memory in the form of Ferroelectric RAM, NOR flash or OTP ROM is also often
included on chip, as well as a typically small amount of RAM. Microcontrollers are designed
for embedded applications, in contrast to the microprocessors used in personal computers or
other general purpose applications.
Microcontrollers are used in automatically controlled products and devices, such as automobile
engine control systems.

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2.16.2 Microprocessor- A microprocessor is a computer processor that incorporates the
functions of a computer central processing unit (CPU) on a single integrated circuit (IC), or at
most a few integrated circuits. The microprocessor is a multipurpose, programmable device
that accepts digital data as input, processes it according to instructions stored in its memory,
and provides results as output. It is an example of sequential digital logic, as it has internal
memory. Microprocessors operate on numbers and symbols represented in the binary numeral
system.
2.16.3 Microcontroller VS Microprocessor
A microcontroller differs from a microprocessor in many ways. The first and most important
difference is its functionality. In order the microprocessor may be used, other components such
as memory or components for data transfer must be added to it. Even though the
microprocessor is considered to be a powerful computer machine, the weak point is that it is
not adjusted to communication to peripheral environment.
Fig 2.24 Microcontroller VS Microprocessor

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Chapter 3
3 Arduino
Arduino is an Open-Source computer hardware and software company, project and user
community that designs and manufactures microcontroller-based kits for building digital
devices and interactive objects that can sense and control objects in the physical world.[10]
The project is based on microcontroller board designs, manufactured by several vendors, using
various microcontrollers. These systems provide sets of digital and analog I/O pins that can be
interfaced to various expansion boards ("shields") and other circuits. The boards feature serial
communications interfaces, including USB on some models, for loading programs from
personal computers. For programming the microcontrollers, the Arduino project provides an
integrated development environment (IDE) based on the Processing project, which includes
support for the C and C++ programming languages.
The first Arduino was introduced in 2005, aiming to provide an inexpensive and easy way for
novices and professionals to create devices that interact with their environment using sensors
and actuators. Common examples of such devices intended for beginner hobbyists include
simple robots, thermostats, and motion detectors.
Arduino boards are available commercially in preassembled form, or as do-it-yourself kits.
The hardware design specifications are openly available, allowing the Arduino boards to be
manufactured by anyone. Adafruit Industries estimated in mid-2011 that over 300,000 official
Arduinos had been commercially produced,[11] and in 2013 that 700,000 official boards were
in users' hands.[12]
Arduino started in 2005 as a project for students at the Interaction Design Institute Ivrea in
Ivrea, Italy. At that time program students used a "BASIC Stamp" at a cost of $100, considered

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expensive for students. Massimo Banzi, one of the founders, taught at Ivrea.[13] The name
"Arduino" comes from a bar in Ivrea, where some of the founders of the project used to meet.
The bar, in turn, has been named after Arduin of Ivrea, who was the margrave of Ivrea and
King of Italy from 1002 to 1014.[14]
Fig 3.1 Single board microcontroller ARDUINO-UNO
FIG 3.2 an formerly produced Arduino board
Colombian student Hernando Barragan created the Wiring development platform which served
as the basis for Arduino. Following the completion of the Wiring platform, its lighter, less
expensive versions[15] were created and made available to the open-source community;

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associated researchers, including David Cuartielles, promoted the idea. The Arduino's initial
core team consisted of Massimo Banzi, David Cuartielles, Tom Igoe, Gianluca Martino, and
David Mellis.
3.1 Official boards from Arduino
The original Arduino hardware was manufactured by the Italian company Smart Projects.[16]
Some Arduino-branded boards have been designed by the American companies SparkFun
Electronics and Adafruit Industries.[17] Sixteen versions of the Arduino hardware have been
commercially produced to date. Among them ten boards are being described below:
 Arduino Uno
 Arduino Leonardo
 Arduino LilyPad
 Arduino Mega
 Arduino Nano
 Arduino Mini
 Arduino Mini Pro
 Cortino (ARM)
 Xduino (ARM)
 Arduino due
Fig 3.3 Some Popular Arduino boards

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3.2 Shields
Arduino and Arduino-compatible boards use printed circuit expansion boards called "shields",
which plug into the normally supplied Arduino pin headers. Shields can provide motor
controls, GPS, Ethernet, LCD, or breadboarding (prototyping). A number of shields can also
be made DIY.
 Example Arduino shields

Multiple shields can be stacked. In this example the top shield contains a solderless
breadboard.

Screw-terminal breakout shield in a wing-type format

Adafruit Motor Shield with screw terminals for connection to motors

Adafruit Datalogging Shield with a Secure Digital (SD) card slot and real-time clock
(RTC) chip

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
HackARobot Fabric Shield – designed for Arduino Nano to hook up motors and
sensors such as gyroscope or GPS, and other breakout boards such as WiFi,
Bluetooth, RF, etc.
3.3 HARDWARE
An Arduino board historically consists of an Atmel 8-,16- or 32-bit AVR microcontroller with
complementary components that facilitate programming and incorporation into other circuits.
An important aspect of the Arduino is its standard connectors, which lets users connect the
CPU board to a variety of interchangeable add-on modules known as shields. [18]
Fig 3.4 Hardware connections for Arduino UNO

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Some shields communicate with the Arduino board directly over various pins, but many shields
are individually addressable via an I²C serial bus—so many shields can be stacked and used in
parallel.
Prior to 2015 Official Arduinos had used the Atmel megaAVR series of chips, specifically the
ATmega8, ATmega168, ATmega328, ATmega1280, and ATmega2560 and in 2015 units by
other manufacturers were added. An Arduino's microcontroller is also pre-programmed with a
boot loader that simplifies uploading of programs to the on-chip flash memory, compared with
other devices that typically need an external programmer.
Current Arduino boards are programmed via Universal Serial Bus (USB), implemented using
USB-to-serial adapter chips such as the FTDI FT232.[19]
The Arduino board exposes most of the microcontroller's I/O pins for use by other circuits.
The Current Uno provide 14 digital I/O pins, six of which can produce pulse-width modulated
signals, and six analog inputs, which can also be used as six digital I/O pins.
3.3 SOFTWARE
Arduino programs may be written in any programming language with a compiler that produces
binary machine code. The Arduino project provides the Arduino integrated development
environment (IDE), which is a cross-platform application written in Java. It originated from
the IDE for the Processing programming language project and the Wiring project. It includes
a code editor and provides simple one-click mechanism for compiling and loading programs
to an Arduino board. A program written with the IDE for Arduino is called a "sketch". [20]
A typical Arduino C/C++ sketch consist of two functions that are compiled and linked with a
program stub main() into an executable cyclic executive program:
setup(): a function that runs once at the start of a program and that can initialize settings.
loop(): a function called repeatedly until the board powers off.

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Fig 3.5 Home screen for arduino
After compilation and linking with the GNU toolchain, also including with the IDE
distribution, the Arduino IDE employs the program avrdude to convert the executable code
into a text file in hexadecimal coding that is loaded into the Arduino board by a loader program
in the board's firmware.
3.4 Development
Arduino is an open-source hardware: the Arduino hardware reference designs are distributed
under a Creative Commons Attribution Share-Alike 2.5 license and are available on the
Arduino Web site. Layout and production files for some versions of the Arduino hardware are
also available. The source code for the IDE is available and released under the GNU General
Public License, version 2.
3.5 Setting up the Arduino Environment
In this section we have some steps to follow such that we can configure the IDE environment
and load the program into the board.

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1.) For starting with programming Arduino we have to first download the software from
Arduino website: http://arduino.cc/en/Main/Software
Now according to the operating system you have there is a software available to you, look
up for your OS and download the respective software. Now you can either download the
installer file or the zip file as per your requirement.
Now after downloading the software now you need to run the Arduino software. Before
running Arduino, plug in your board using USB cable. If USB device is not recognized, select
the appopriate driver from the installation directory. After driver installation we can finally run
our program and set up the environment for Arduino board.
2.) Next, Start the Arduino software from the installed setup and run the application file.
Fig 3.6 Arduino IDE
3.) Select the type of hardware or board you have from tools.

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Fig 3.7 Selecting Arduino Board
4.) Select serial port
Fig 3.8 Selecting the serial port
Selection of serial port is very important as without this port selection Arduino hardware would
not going to be detected by software.

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3.6 Programming an Arduino
Now let’s move on to the programming basics of Arduino.
Arduino programming starts with defining two blocks where we define and manipulate the data or use
them accordingly as per the need. These are described below.
void setup()
–Will be executed
only when the
program begins
(or reset button
is pressed)
void loop()
–Will be executed
repeatedly
So it is clear from above that our program will revolve around these two code blocks.
In the first block, i.e. , void setup() we define our input and output ports. Formally it
includes all the parameters for the program. It is similar to the initialization.
Next we have void loop(). This includes the body of the program, it is similar to an infinite
loop, which unconditionally move through the body of the program.
void setup() {
// put your setup code here, to run once:
}
void loop() {
// put your main code here, to run repeatedly:
}
Text that follows// is a comment
(ignored by compiler)
Useful IDE Shortcut: PressCtrl‐/
to comment (or uncomment) a
selected portion of your program.

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Chapter 4
4 Arduino interfacing
4.1 LED
To build the circuit, connect one end of the resistor to Arduino pin 13. Connect the long leg
of the LED to the other end of the resistor. Connect the short leg of the LED to the Arduino
GND. Most Arduino boards already have an LED attached to pin 13 on the board itself. The
value of the resistor should be 220 ohm; the LED will lit up also with values up to 1K ohm.
Fig 4.1 Led with Arduino
4.2 Switch
Switch as described used to provide a break between a circuit. Here it is connected in pull
down mode with a 10k ohm resistor. One part of switch is connected to the controller while
the other is connected to GND through the resistor.
Fig 4.2 Switch connected to Arduino

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4.3 Seven Segment Display Interfacing
• A seven-segment display can be used to display the decimal numbers 0-9 and some
alpha characters.
• Each Segment is labeled (a) to (g).
• Common Cathode (all LED cathodes are connected)
• Common Anode (all LED anodes are connected)
Fig 4.3 Seven segment display and it interfacing with Arduino
4.4 LCD interfacing
• LCD’s are all around us so liquid crystal displays are very useful in these days.
• It is a kind of display that is made up of a special matter state formed using liquid
and crystal both , it’s a forth state of matter
• The most popular one is 16x2 LCD module. It has 2 rows & 16 columns. The
intelligent displays are two types:
 Text Display
 Graphics Display
 8 data pins D7:D0 - Bi-directional data/command pins.
 RS: Register Select
RS = 0 -> Command Register is selected
RS = 1 -> Data Register is selected
 R/W: Read or Write - 0 -> Write, 1 -> Read

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Fig 4.4 LCD Pin Description Fig 4.5 LCD with Arduino.
 E: Enable (Latch data) - Used to latch the data.
 VEE: contrast control.
 VDD & VSS: Power supply
VDD= +5V
VSS=GND
4.5 DC Motor Interfacing
• The simplest DC rotating machine consists of a single loop of wire rotating about a
fixed axis. The magnetic field is supplied by the North and South poles of the magnet.
• Rotor is the rotating part.Stator is the stationary part.
• We can reverse the motor direction the simply by reversing the power supply
connection of motor. It means motor is bipolar device.
Necessary Medium to Operate
• We are working on microcontroller and the maximum output current that it can
provide is 20mA.
• But our motor works on 1Amp current so to remove this problem we will have to

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connect motor driver IC L293D in between the microcontroller and motor.
Fig 4.6 IC L293D and Its interfacing with motor
4.6 IR Sensor interfacing
 There are two part of the sensors:
1. Emitter
2. Receiver
 Emitter converts the electrical current in the Infra-Red Radiation.
 Receiver receive the IR radiation when the radiation reflect back after the
collision from the obstacle.
Operating Modes:
Our IR sensor can work in two modes:
 Analog Mode and Digital Mode
How to use?
• Digital Mode:-In this mode you can directly connect the sensor to any pin
of the controller.
• Analog Mode:-In this mode sensor will give analog value so you have to
use ADC

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Fig 4.7 IR sensor
4.7 LM35 Interfacing
• LM35 is a precision IC temperature sensor with its output proportional to the
temperature (in o C). The sensor circuitry is sealed and therefore it is not subjected to
oxidation and other processes.
• The operating temperature range is from -55°C to 150°C. The output voltage varies
by 10mV in response to every o C rise/fall in ambient temperature, i.e., its scale factor
is 0.01V/ o C.
Pin Diagram
Fig 4.8 LM35 and its Interfacing
4.8 Relay Interfacing
• Relays are used where it is necessary to control a circuit by a low-power signal (with
complete electrical isolation between control and controlled circuits), or where
several circuits must be controlled by one signal

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• Provide a sufficient amount of current to this relay, an extra circuit is also require
because microcontroller is not capable of providing such current, that’s why
ULN2803 IC is used for this purpose.
Fig 4.9 Relay with Arduino
4.9 LDR
LDR is connected to Arduino in pull down manner. One terminal of LDR is
connected to GND and other terminal is connected the analog input A0.
Also 10K ohm resistor is to LDR terminal which is going into the GNd.
Fig 4.10 LDR with Arduino

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4.10 Accelerometer interfacing
 An accelerometer measures acceleration (change in speed) of anything that
it's mounted on.
 Inside an accelerator MEMS device are tiny micro-structures that bend due
to momentum and gravity. When it experiences any form of acceleration,
these tiny structures bend by an equivalent amount which can be electrically
detected
 It detects the motion in X, Y and Z directions. Accelerometer can be
interfaced with the controller with ADC PORT because it will also give
analog output. These analog form values can be obtained by connecting X,
Y and Z pins of the sensor to the controller’s ADC pins.
 Similar to the analog sensors it will also give the different values whenever
any motion will be there in X, Y, Z direction.
Fig 4.11 Accelerometer with Arduino

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Chapter 5
5. Home Automation
The Home Automation is a wireless home automation system that is supposed to be
implemented in existing home environments, without any changes in the existing
infrastructure. Home Automation lets the user to control his home from his or her computer.
In the computer program the user can create actions what should happen with electrical devices
in the network depending on the sensors sensing surrounding environment.
The concept here is that there will be a box connected to the mains and controls the power
outlet of the electrical device that is plugged into it. Each box contains a circuitry to control
the appliances connected to the box. This circuit is controlled by the signal sent by the user
which further checked upon by the controller to take corresponding action.
People can control power supply of electrical devices in order to create an interactive home
environment to facilitate the control without changing any home appliance. People can enjoy
the high technology and simplicity modern life style. Each device will be with standard setup
and while adding it into network; it can be given an address and tasks to do. All the setting will
be easily resettable to default value, so people can move the devices between different
electrical devices and networks.Home Automation boxes will be put into different rooms at
home, depending on the needed functionality. Various different sensors could be attached to
the boxes. The sensors are used as triggers for actions, that user can set up in the User Interface
of application.
In the development of this project there are two important part, they are:
1.) ANDROID
2.) ARDUINO

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These both topics are later covered in this report in more detail as how to program for your
system and how to configure them.
The project started off with a brainstorming session. All ideas about how the Home Automation
should work and what functions it should have were written on a whiteboard. We discussed all
possible solutions and ideas that we had come up with and removed things that were not
possible to implement within this project scope. All that was left on the whiteboard in the end
was divided up into following task areas:
• Network
Create a wireless connection between embedded Arduino boards and the Android application.
• Software
Computer software has to be able to control the communication, send tasks for Home
Automation embedded devices and be provided with the GUI where end users can set up
actions.
• Electronics
This area covers in detail the hardware solutions chosen and how that affected the final
prototype. The hardware could be described as three different work areas: arduino,
dimmer/switching circuit and wireless modules.
• Prototyping and construction
The last focusing area is prototyping the final product. We need to build the product and put it
into aesthetic form. The presentation of the project should be done so the visitors understand
how the final product is supposed to be used. Therefore we have to come up the suitable
scenarios to present. Some furniture is needed to get a home environment feeling for the
presentation.

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5.1 Software
In parallel with the Arduino code being programmed, the software for the computer was
created. The software is to be installed on the end user's computer in order to set up and run
the Home Automation network at home. The program is written in Java, a language chosen
because of the existing knowledge about the language in the group and the in-built cross-
platform support.
4.2.1 User Interface
The main user interface is divided in two parts, the main panel with all connected devices and
their status and a table of all currently configured actions and their priority.
4.2.2 Device Panel
The device panel is a horizontally scrollable list of all connected devices, which can be
described by a custom name. For each device you can see all connected sensors and their status.
You can also in real time control each device, for example set a lamps intensity to medium
intensity or slowly fade another from off to fully lit and query the current status of the device’s
controllable outlet.
4.2.3 Actions
One of the main features of the program is the ability for the user to configure actions. An
action is a kind of “if-then” clause. For example: “If the night lamp lights up at night then set
all hallway lamps to half lit”. The user can also assign a custom name to each action to make
it easy to associate the action with what is performed.
Below the list of devices there is a list of all currently configured actions and their priority.
The action’s priority can be changed and the actions themselves can be edited and deleted. If
the “Edit” button or then “Add new action” is clicked, a new dialog is opened where the user
can create or edit new actions to produce the kind of if-then clauses described above. Actions
can have an arbitrary number of input triggers and output actions.

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4.2.4 Other Functions
Apart from the two abovementioned core functions of the user interface, there are also a few
assorted functions to be able to setup the network properties and to monitor the network
activity and the messages getting transferred.
In Figure below, there is a description of how data is being sent out to from a smart phone to
the Bluetooth Module connected to the Arduino. Commands are being send in form of ASCII
value and compare with instructions written in the program.
Here we can see the five relays connected with Arduino. These relays are operated as per the
commands send by the user.
Fig 5.1 A shorthand view of Home Automation system
The Android application we are using here is being developed in Eclipse using Android SDK
tools. These applications are also downloaded from Google Play store. There are also some
Open-Source projects we can use provided on GITHUB. So we have a lot of options in
developing these Android Apps and we can use any one of them.

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Now concerning Bluetooth Connectivity we need to connect the smartphone with the
Bluetooth module named like HC-05 and HC-06. A connection authentication is necessary
here since without this we cannot connect out sytem to outer modules.
`
Fig 5.2 Connecting to Bluetooth Module HC-06
Moreover there are two basic softwares which we are going to use in this project, they are
described below:
1. Arduino IDE: Arduino.
2. Eclipse for android programming (optional, not required).
These both software can easily be downloaded from their respective websites.
For Operating these Bluetooth devices we are using the Bluetooth terminal called
Blue Term version 1.1 stable release.

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5.2 Hardware
The heart and soul of this project is the Arduino. It is responsible for controlling as which
appliance should operate at any particular time. Here we are using Arduino UNO as controller.
Its IC Atmega328PU, which is also called the Arduino IC, is going to be use in this project
and will be referred to as Arduino controller. In this text we will be using ATmega328PU as
Arduino controller. ATmega328 is a microcontroller from Atmel.
All the components required for the development of Home Automation are stated below:
1. Arduino / Arduino Clone or make your own custom Arduino board with this tutorial.
2. A 5v TTL -UART Bluetooth module
3. Four 5V SPDT Relays
4. Prototype board or breadboard.
5. Connecting wires.
6. PCB
7. Motor driver IC L23D
Further with Arduino is the Bluetooth Module HC-05. This will be used to communicate with
the Bluetooth module of Android phone.
Next is a schematic for Arduino connected with relays. Relay provide the isolation between
high signal AC to low signal DC. Now for connecting a controller with relays we need one
more thing i.e. transistor. It is used to turn on the relay and also helpful in providing safety to
the controller IC.
Bluetooth module is connected at the Rx-Tx pin. Rx of Bluetooth is connected to Tx of
microcontroller, and similarly Tx pin of Bluetooth is connected to Rx of microcontroller.

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These two pins are responsible for serial communication in Arduino and also data through the
Bluetooth module is also go serially to the IC. Data is interpreted here in ASCII value for
comparison as what is being sent by the user.
Fig 5.3 Home Automation Schematic
There is a motor driver IC L293D which is used to drive DC motors. Since motors drive high
current, they could damage the controller IC for that purpose this IC is used.
A detailed schematic of home automation is provided below where the hard connections to
microcontroller is shown. Here relay connection through a transistor is shown.

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Fig 5.4 Circuit Diagram of Home Automation
Also a diode is connected in between the supply mode of relay, to eliminate the chances of
reverse current to relay since diode allows current in only one direction and there will be no
current flowing from ground to supply.
Further this diagram demonstrate a development circuit not only for Home Automation but
also for Arduino board not as efficient as the actual board but it can quiet nicely.

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5.3 PCB Design for Home Automation
PCB designing for Home Automation is done on any layout designer. Here we use Dip Trace
for designing the component and layout design. They both are shown below.
Fig 5.5 Component Design
Fig 5.6 Layout Design

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5.4 Design Specification
The system is designed keeping in mind the following key requirements:
 Clients should be able to quickly and seamlessly connect to and disconnect from
the system.
 Connections from all kinds of clients must be handled simultaneously; i.e.
Bluetooth.
 Change in the status of an appliance should be propagated to all clients in real-
time.
 Customizable time-based profiles to automatically activate and deactivate
appliances based on the time of day.
 Hardware should be widely compatible with different smart phone
configurations.
 Provide a simple and user-friendly interface on the client side.
Fig 5.7 A screenshot of BT terminal

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5.4.1 Data Flow Diagram
Fig 5.8 Data Flow Diagram
Server
Wi-Fi / Bluetooth
Mobile Device
USB-to-Serial
Bridge
Microcontroller
Relay System

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The mobile device connects to the Microcontroller through Bluetooth or Wi-Fi. The user sends
commands to the server from the mobile device. The microcontroller is connected to the server
via USB. On receiving commands from the mobile device, the server sends commands to the
microcontroller over the USB connection, also this data is send serially via Rx-Tx pin. The
microcontroller is directly connected to the relays and it can enable or disable them. The relays
are connected to the electrical system of the building so that they can control the plug points.
Fig 5.7 Bluetooth module
HC-05 module is an easy to use Bluetooth SPP (Serial Port Protocol) module, designed for
transparent wireless serial connection setup.
Serial port Bluetooth module is fully qualified Bluetooth V2.0+EDR (Enhanced Data Rate)
3Mbps Modulation with complete 2.4GHz radio transceiver and baseband. It uses CSR
Bluecore 04-External single chip Bluetooth system with CMOS technology and with
AFH(Adaptive Frequency Hopping Feature). It has the footprint as small as 12.7mmx27mm.
Hope it will simplify your overall design/development cycle.

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5.5 Programming code for microcontroller.
int rel1=12; // relay 1
int rel2=11; // relay 2
int mtr=10; // motor 1
int mtr1=9; // motor 2
int val; // taking a variable
void setup()
{
pinMode(rel1,OUTPUT); // set relay 1 as ouput for bub 1
pinMode(rel2,OUTPUT); // set relay 2 as ouput for bub 2
pinMode(mtr,OUTPUT); // set motor pin 1 as ouput
pinMode(mtr1,OUTPUT); // set motor pin 2 as ouput
Serial.begin(9600); // setting the baud rate for serial communication
}
void loop()
{
while(Serial.available()==0); // setting default value of “val” equal to Zero ( 0 )
val = Serial.read(); // saving the input value coming from the BT terminal

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if(val=='1') // if val is equal to 1, checking the condition
{
digitalWrite(rel1,HIGH); // then turn the bulb 1 or relay 1 ON.
}
else if(val=='2') // if val is equal to 2
{
digitalWrite(rel1,HIGH); // turn ON the relay no 2 or bulb no 2
}
else if(val=='3') // if val is equal to 2
{
digitalWrite(rel,LOW); // setting the relay 1 or bulb 1 OFF
digitalWrite(rel1,LOW); // setting the relay 2 or bulb 2 OFF
}
else if(val== '4') // if val is equal to 4
{
digitalWrite(mtr,HIGH); // motor moving in clockwise direction using both statement
digitalWrite(mtr1,LOW);
delay(5000);
}
else if(val == '5') // if val is equal to 5
{
digitalWrite(mtr,LOW); // motor moving in anti-clockwise direction using both statement
digitalWrite(mtr1,HIGH);
delay(5000);

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}
else if(val == '6') // if val is equal to 6
{
digitalWrite(mtr,LOW); // motor moving in anti-clockwise direction using both statement
digitalWrite(mtr1,LOW);
delay(5000);
}
} // end of the prigram
Fig 5.8 Garage Operating Up nad Down
Fig 5.9 Bulb 1 and bulb 2 Glowing Alternately

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References
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2. “Principles of Electrical Engineering.” Books.google.com. Retrieved 2012-10-29.
3. Anthony J. Pansini “Electrical Distribution Engineering”, The Fairmont Press Inc., 2006
4. Erik Barnouw “A Tower in Babel”, p. 28, Oxford University Press US, 1966
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6. Charles A. Harper “High Performance Printed Circuit Boards”, McGraw-Hill, 2000
7. Rakesh K. Garg/Ashish Dixit/Pavan Yadav “Basic Electronics”, p. 1, Firewall Media,
2008
8. Sachin S. Sharma “Power Electronics”, Firewall Media, 2008
9. Edward J. Rothwell/Michael J. “Cloud Electromagnetics”, CRC Press, 2001
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13. David Kushner (26 Oct 2011). "The Making of Arduino". IEEE Spectrum.
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15. "Rhizome - Interview with Casey Reas and Ben Fry". 2009-09-23.
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