Travel Assistant For Blind With Dynamic User Input For Location Based Alerts Using ARM7 And XBee (REPORT)

PROJECT REPORT
ON
“TRAVEL ASSISTANT FOR BLIND WITH
DYNAMIC USER INPUT FOR LOCATION BASED
ALERTS USING ARM7 AND ZIGBEE”

A PROJECT REPORT ON
“Travel Assistant For Blind With Dynamic User Input For Location
Based Alerts Using Arm7 And Zigbee”
Submitted in partial fulfilment of the requirements
For the award of the degree
BACHELOR OF ENGINEERING
IN
ELECTRONICS AND COMMUNICATION ENGINEERING
SUBMITTED BY
____________ ( _______ )
____________ ( _______ )
____________ ( _______ )
____________ ( _______ )
DEPARTMENT OF ______________ ENGINEERING
________ COLLEGE OF ENGINEERING
AFFILIATED TO ___________ UNIVERSITY

CERTIFICATE
This is to certify that the dissertation work entitled “Travel Assistant
For Blind With Dynamic User Input For Location Based
Alerts Using Arm7 And Zigbee” is the work done by
_________________________________________________________
submitted in partial fulfilment for the award of ‘BACHELOR OF
ENGINEERING (B.E)’ in ____________________________
Engineering from ___________ College of Engineering affiliated to
_________ University, Hyderabad .
___________________ _____________
(Head of the department, ECE/EEE) (Assistant Professor)
EXTERNAL EXAMINER

ACKNOWLEDGEMENT
The satisfaction and euphoria that accompany the successful completion of
any task would be incomplete without the mentioning of the people whose
constant guidance and encouragement made it possible. We take pleasure in
presenting before you, our project, which is result of studied blend of both
research and knowledge.
We express our earnest gratitude to our internal guide, Assistant Professor
___________, Department of ECE/EEE, our project guide, for his constant
support, encouragement and guidance. We are grateful for his cooperation
and his valuable suggestions.

DECLARATION
We, the undersigned, declare that the project entitled ‘Travel Assistant
for Blind with Dynamic User Input for Location Based Alerts
Using Arm7 and Zigbee’, being submitted in partial fulfilment for the
award of Bachelor of Engineering Degree in Electronics and
Communication Engineering, affiliated to __________ University, is the
work carried out by us.
___________ ___________ __________
___________ ___________ __________

CONTENTS
Chapter 1: Abstract
Chapter 2: Introduction
Chapter 3: Motivation
Chapter 4: Block Diagram
Chapter 5: Block Diagram Explanation
Chapter 6: Methodology
Chapter 7: Circuit Diagram & Explanation
Chapter 8: Applications & Future Enhancement
8.1: Applications
8.2: Future Enhancement
Chapter 9: Advantages & Disadvantages
9.1: Advantages
9.2: Disadvantages
Chapter 10: Result/Conclusion
Chapter 11: General Components
Chapter 12: PCB Designing & Soldering Techniques
12.1: PCB Designing
12.2: Soldering Techniques
Chapter 13: References

CHAPTER 1:
ABSTRACT
One of the major goals for blind and visually impaired people is independent mobility.
Mobility aids like walking stick and guide dogs are commonly used by the blind even
today. With the advances of modern technologies many different types of devices are
available to support the mobility of blind. These mobility aids are generally known as
electronic travel aid.
It involves a switches to detect the location of the user when he walks and a ARM
controller with synthetic speech output
.

CHAPTER 2:
INTRODUCTION
The goal of Blind Aid project is to develop navigational assistance technology for the
blind or visually impaired. Specifically, we seek to develop a portable Electronic Travel
Aid (ETA) for visually impaired users, along with the accompanying radio frequency
identification (RFID) localization infrastructure used to equip buildings.
The major problems the visually impaired experience is trouble with indoor navigation in
unfamiliar buildings. Imagine the wide open spaces in an airport concourse; even if there
are Braille signs at the counters, the blind may not be able to find them.
Blind people use moving ramps, escalators, revolving doors, and turnstiles with as much
ease as any sighted person. When encountering stairs, it simply isn't necessary to explore
each step. The cane tip is used primarily to detect the beginnings and ends of stairways.
In either case it is a good idea to hold the cane in a manner that would not trip a fellow
pedestrian.
today. With the advances of modern technologies many different types of devices are
available to support the mobility of blind. These mobility aids are generally known as
electronic travel aid.

CHAPTER 3:
MOTIVATION
The major problems the visually impaired experience is trouble with indoor navigation in
unfamiliar buildings. Imagine the wide open spaces in an airport concourse; even if there
are Braille signs at the counters, the blind may not be able to ﬁnd them. Everyday
situations present similar challenges.
today.

CHAPTER 4:
BLOCK DIAGRAM
➢ Transmitter stage
HARDWARE REQUIREMENTS: ARM 7 / Cortex M3, LCD, Relay Driver, Relays, Resistors, Capacitors, LEDs, Crystal, Diodes,
Transformer, Voltage Regulator, Push Button.
SOFTWARE REQUIREMENTS:Keil compiler uVision 4, Language: Embedded C or Assembly, WLPRO Programmer
GND
LCD DISPLAY
230 V, AC
Supply
TRANSFORM
ER
RECTIFIER FILTER REGULATOR
+12 Volts
+5 Volts
XBEE
TX
ARM PROCESSOR
KEY INPUTS

➢ Receiver stage
BUFFE
R
DRIVE
R
RELAY
LCD DISPLAY
ARM PROCESSOR
OR
OR
M
VISUAL
INDICATIO
N
VOICE
DC MOTOR
OUTPUT
DEVICES
XBEE
RX

CHAPTER 5:
BLOCK DIAGRAM EXPLANATION
➢ Power supply unit
This section needs two voltages viz., +12 V & +5 V, as working voltages. Hence
specially designed power supply is constructed to get regulated power supplies .
➢ Switches:
In electrical engineering, a switch is an electrical component that can break an electrical
circuit, interrupting the current or diverting it from one conductor to another. A switch
may be directly manipulated by a human as a control signal to a system. Automatically
operated switches can be used to control the motions of machines.
➢ ARM processor
ARM is computer processor based RISC architecture. A RISC-based computer design
approach means ARM processors require significantly fewer transistors than typical
processors in average computers. This approach reduces costs, heat and power use. The
low power consumption of ARM processors has made them very popular:
The ARM architecture (32-bit) is the most widely used architecture in mobile devices,
and most popular 32-bit one in embedded systems.
➢ Buffers
Buffers do not affect the logical state of a digital signal (i.e. a logic 1 input results in a
logic 1 output whereas logic 0 input results in a logic 0 output). Buffers are normally used
to provide extra current drive at the output but can also be used to regularize the logic
present at an interface
➢ Drivers
This section is used to drive the relay where the output is complement of input which is
applied to the drive but current will be amplified
➢ Relays

It is a electromagnetic device which is used to drive the load connected across the relay
and the o/p of relay can be connected to controller or load for further processing.
➢ Zigbee Technology
ZigBee is a specification for a suite of high level communication protocols used to
create personal area networks built from small, low-power digital radios. ZigBee is based
on an IEEE 802.15 standard. Though low-powered, ZigBee devices can transmit data
over long distances by passing data through intermediate devices to reach more distant
ones, creating a mesh network.
➢ Buzzer:
A buzzer or beeper is an audio signalling device, which may
be mechanical, electromechanical, or piezoelectric. Typical uses of buzzers and beepers
include alarm devices, timers and confirmation of user input such as a mouse click or
keystroke.
➢ DC motor:
A DC motor relies on the facts that like magnet poles repels and unlike magnetic poles
attract each other. A coil of wire with a current running through it generates
an electromagnetic field aligned with the centre of the coil. By switching the current on
or off in a coil its magnetic field can be switched on or off or by switching the direction
of the current in the coil the direction of the generated magnetic field can be switched
180°.
➢ Voice recorder:
The aPR33A series are powerful audio processor along with high performance audio
analog-to-digital converters (ADCs) and digital-to-analog converters (DACs). The
aPR33A series are a fully integrated solution offering high performance and unparalleled
integration with analog input, digital processing and analog output functionality. High
quality audio/voice systems with lower bill-of-material costs can be implemented with
the aPR33A series because of its integrated analog data converters and full suite of
quality-enhancing features such as sample-rate convertor.
In this messages must be recorded or played back sequentially, specially designed for
simple key trigger, user can record and playback the message. Meanwhile, this mode
provides the power-management system.

CHAPTER 6:
METHODOLOGY
This project is developed for the blinds to find out the location of the place where they
are. The main modules in this project are Zigbee, ARM controller unit and Voice signal
as a output.
The transmitter will be there with a blind and the receiver will be there at the location.
The transmitter module has Switches, ARM controller and Zigbee as a communication
media. The receiver has Zigbee, ARM controller and voice operated device. If a Blind
Presses a Switch to know the location, that information will be given to ARM controller,
then the ARM controller analyses the signal and sends information to receiver which is
present in the location via Zigbee. At the receiver the Zigbee receives a signal which was
transmitted from transmitter and sends that to the ARM controller. After receiving the
signal the ARM controller will activate the proper voice chip to provide a corresponding
voice signal.

CHAPTER 7:
CIRCUIT DIAGRAM & EXPLANATION
➢ POWER SUPPLY UNIT
The circuit needs two different voltages, +5V & +12V, to work. These dual voltages are
supplied by this specially designed power supply.
The power supply, unsung hero of every electronic circuit, plays very important role in
smooth running of the connected circuit. The main object of this ‘power supply’ is, as the
name itself implies, to deliver the required amount of stabilized and pure power to the
circuit. Every typical power supply contains the following sections:
1. Step-down Transformer: The conventional supply, which is generally available to the
user, is 230V AC. It is necessary to step down the mains supply to the desired level. This
is achieved by using suitably rated step-down transformer. While designing the power
supply, it is necessary to go for little higher rating transformer than the required one. The
reason for this is, for proper working of the regulator IC (say KIA 7805) it needs at least
2.5V more than the expected output voltage
2. Rectifier stage: Then the step-downed Alternating Current is converted into Direct
Current. This rectification is achieved by using passive components such as diodes. If the
power supply is designed for low voltage/current drawing loads/circuits (say +5V), it is
sufficient to employ full-wave rectifier with centre-tap transformer as a power source.
While choosing the diodes the PIV rating is taken into consideration.
3. Filter stage: But this rectified output contains some percentage of superimposed a.c.
ripples. So to filter these a.c. components filter stage is built around the rectifier stage.
The cheap, reliable, simple and effective filtering for low current drawing loads (say upto
50 mA) is done by using shunt capacitors. This electrolytic capacitor has polarities, take
care while connecting the circuit.

4. Voltage Regulation: The filtered d.c. output is not stable. It varies in accordance with
the fluctuations in mains supply or varying load current. This variation of load current is
observed due to voltage drop in transformer windings, rectifier and filter circuit. These
variations in d.c. output voltage may cause inaccurate or erratic operation or even
malfunctioning of many electronic circuits. For example, the circuit boards which are
implanted by CMOS or TTL ICs.
The stabilization of d.c. output is achieved by using the three terminal voltage regulator
IC. This regulator IC comes in two flavors: 78xx for positive voltage output and 79xx for
negative voltage output. For example 7805 gives +5V output and 7905 gives -5V
stabilized output. These regulator ICs have in-built short-circuit protection and auto-
thermal cutout provisions. If the load current is very high the IC needs ‘heat sink’ to
dissipate the internally generated power.
Circuit Description: A d.c. power supply which maintains the output voltage constant
irrespective of a.c. mains fluctuations or load variations is known as regulated d.c. power
supply. It is also referred as full-wave regulated power supply as it uses four diodes in
bridge fashion with the transformer. This laboratory power supply offers excellent line
and load regulation and output voltages of +5V & +12 V at output currents up to one
amp.
1 2 3
KIA 78xx
Series

CIRCUIT DIAGRAM OF +5V & +12V FULL WAVE REGULATED POWER SUPPLY
Parts List:
SEMICONDUCTORS
IC1
IC2
7812 Regulator IC
7805 Regulator IC
1
1
D1& D2 1N4007 Rectifier Diodes 2
CAPACITORS
C1 1000 µf/25V Electrolytic 1
C2 to C4 0.1µF Ceramic Disc type 3
MISCELLANEOUS
X1 230V AC Pri,14-0-14 1Amp Sec Transformer 1
230AC
X
1
C1
D
21
C2 C
3
IC1
7812
D
11
9V
C4
IC1
780
5
+12V
+5V

1. Step-down Transformer: The transformer rating is 230V AC at Primary and 12-0-12V,
1Ampers across secondary winding. This transformer has a capability to deliver a current
of 1Ampere, which is more than enough to drive any electronic circuit or varying load.
The 12VAC appearing across the secondary is the RMS value of the waveform and the
peak value would be 12 x 1.414 = 16.8 volts. This value limits our choice of rectifier
diode as 1N4007, which is having PIV rating more than 16Volts.
2. Rectifier Stage: The two diodes D1 & D2 are connected across the secondary winding
of the transformer as a full-wave rectifier. During the positive half-cycle of secondary
voltage, the end A of the secondary winding becomes positive and end B negative. This
makes the diode D1 forward biased and diode D2 reverse biased. Therefore diode D1
conducts while diode D2 does not. During the negative half-cycle, end A of the
secondary winding becomes negative and end B positive. Therefore diode D2 conducts
while diode D1 does not. Note that current across the centre tap terminal is in the same
direction for both half-cycles of input a.c. voltage. Therefore, pulsating d.c. is obtained at
point ‘C’ with respect to Ground.
3. Filter Stage: Here Capacitor C1 is used for filtering purpose and connected across the
rectifier output. It filters the a.c. components present in the rectified d.c. and gives steady
d.c. voltage. As the rectifier voltage increases, it charges the capacitor and also supplies
current to the load. When capacitor is charged to the peak value of the rectifier voltage,
rectifier voltage starts to decrease. As the next voltage peak immediately recharges the
capacitor, the discharge period is of very small duration. Due to this continuous charge-
discharge-recharge cycle very little ripple is observed in the filtered output. Moreover,
output voltage is higher as it remains substantially near the peak value of rectifier output
voltage. This phenomenon is also explained in other form as: the shunt capacitor offers a
low reactance path to the a.c. components of current and open circuit to d.c. component.
During positive half cycle the capacitor stores energy in the form of electrostatic field.
During negative half cycle, the filter capacitor releases stored energy to the load.
4. Voltage Regulation Stage: Across the point ‘D’ and Ground there is rectified and
filtered d.c. In the present circuit KIA 7812 three terminal voltage regulator IC is used to
get +12V and KIA 7805 voltage regulator IC is used to get +5V regulated d.c. output. In

the three terminals, pin 1 is input i.e., rectified & filtered d.c. is connected to this pin. Pin
2 is common pin and is grounded. The pin 3 gives the stabilized d.c. output to the load.
The circuit shows two more decoupling capacitors C2 & C3, which provides ground path
to the high frequency noise signals. Across the point ‘E’ and ‘F’ with respect to ground
+5V & +12V stabilized or regulated d.c output is measured, which can be connected to
the required circuit.
Note: While connecting the diodes and electrolytic capacitors the polarities must be taken
into consideration. The transformer’s primary winding deals with 230V mains, care
should be taken with it.
➢ BUFFER&DRIVER
When the user programs the schedule for the automation using GUI [Graphical User
Interface] software, it actually sends 5-bit control signals to the circuit. The present
circuit provides interfacing with the Microcontroller and the controlling circuitry. This
circuit takes the 5-bit control signal, isolates the CONTROLLER from this circuitry,
boosts control signals for required level and finally fed to the driver section to actuate
relay. These five relays in turn sends RC5 coded commands with respect to their relay
position.
First the components used in this Module are discussed and then the actual circuit is
described in detail.
HEX BUFFER / CONVERTER [NON-INVERTER] IC 4050: Buffers does not affect the
logical state of a digital signal (i.e. logic 1 input results into logic 1 output where as logic
0 input results into logic 0 output). Buffers are normally used to provide extra current
drive at the output, but can also be used to regularise the logic present at an interface.
And Inverters are used to complement the logical state (i.e. logic 1 input results into logic
0 output and vice versa). Also Inverters are used to provide extra current drive and, like
buffers, are used in interfacing applications. This 16-pin DIL packaged IC 4050 acts as
Buffer as-well-as a Converter. The input signals may be of 2.5 to 5V digital TTL
compatible or DC analogue the IC gives 5V constant signal output. The IC acts as buffer

and provides isolation to the main circuit from varying input signals. The working
voltage of IC is 4 to 16 Volts and propagation delay is 30 nanoseconds. It consumes 0.01
mill Watt power with noise immunity of 3.7 V and toggle speed of 3 Megahertz.
ULN 2003: Since the digital outputs of the some circuits cannot sink much current, they
are not capable of driving relays directly. So, high-voltage high-current Darlington arrays
are designed for interfacing low-level logic circuitry and multiple peripheral power loads.
The series ULN2000A/L ICs drive seven relays with continuous load current ratings to
600mA for each input. At an appropriate duty cycle depending on ambient temperature
and number of drivers turned ON simultaneously, typical power loads totalling over
260W [400mA x 7, 95V] can be controlled. Typical loads include relays, solenoids,
stepping motors, magnetic print hammers, multiplexed LED and incandescent displays,
and heaters. These Darlington arrays are furnished in 16-pin dual in-line plastic packages
(suffix A) and 16-lead surface-mountable SOICs (suffix L). All devices are pinned with
outputs opposite inputs to facilitate ease of circuit board layout.
1
2
6
3
16
5
15
4
14
10
11
12
13
7
V
cc
V
ss
8 9
IC4050

The input of ULN 2003 is TTL-compatible open-collector outputs. As each of these
outputs can sink a maximum collector current of 500 mA, miniature Controller relays can
be easily driven. No additional free-wheeling clamp diode is required to be connected
across the relay since each of the outputs has inbuilt free-wheeling diodes. The Series
ULN20x4A/L features series input resistors for operation directly from 6 to 15V CMOS
or PMOS logic outputs.
1N4148 signal diode: Signal diodes are used to process information (electrical signals) in
circuits, so they are only required to pass small currents of up to 100mA. General purpose
signal diodes such as the 1N4148 are made from silicon and have a forward voltage drop
of 0.7V.
Vcc
1 16
2
3
4
5
6
7
8
11
12
14
15
13
10
9
IC ULN 2003

CIRCUIT DIAGRAM OF BUFFER & DRIVER
GND
5
3
9
7
8
1
11
4
2
10
6
12
14
15
RL2 RL3 RL4 RL5
IC1
IC2
2
1
4
3
8
9
5
15
16
13
12
6 11
14
7
10
R1 TO R5
D1 TO D5
+5V
+12 V
Input
D6-D10
R6-R10
RL1
N/C
Output
N/C
Output
N/C
Output
N/C
Output
N/C
Output

Parts List:
Circuit Description:
The Hex Buffer/Inverter IC1’s working voltage of +5V is applied at pin-1 and five
control signals are applied at input pins 3, 5, 7, 9 & 11. Thus the signal supplying circuit
[i.e. CONTROLLER] is isolated from this Buffer & Driver circuit. Further the grounding
resistors R1 to R5 prevents the abnormal voltage levels passing inside the IC1. The
buffered outputs are acquired at pins 2, 4, 6, 10, & 12. Thus the varying input is further
stabilized and fed to signal diodes [D1 to D5]. As the load is inductive, there is a chance
of producing back e.m.f. So to cope with this back e.m.f, signal diodes are used. But this
signal level is not strong enough to drive the low impedance relay. So, IC2 Darlington
driver is used. Its working voltage is +12 V and only five input/output pins are used. The
output signal from the Darlington driver IC is strong enough to actuate five relays.
SEMICONDUCTORS
IC1 4050 HEX BUFFER/CONVERTER(NON-INVERTER) 1
IC2 2003 DARLINGTON ARRY 1
RESISTORS
R1 to R5 220 Ohm ¼ Watt Carbon Resistors 5
R6 to R10 2.2 K Ohm ¼ Watt Carbon Resistors 5
DIODES
D1to D5 1N4148 SIGNAL Diodes 5
D6 to D10 Red Indicator LEDs 5
MISCELLANEOUS
RL1-RL5 12 V, 700 Ohm DPDT Reed Relays 5

These relays with +12V working voltage can be used to produce five command signals
with RC5 format. The N/O [Normally Open] contact of each relay produces one
command signal with the help of RC5 Transmitter Circuit. The five relays activation with
their corresponding command signal production is tabulated as below:
RELAY COMMAND NUMBER COMMAND SIGNAL
RL1 Output-1 TURN LEFT
RL2 Output-2 TURN RIGHT
RL3 Output-3 MOVE BACKWARD
RL4 Output-4 MOVE FORWARD
RL5 Output-5
SWITCH ON/OFF THE
SUCKING DEVICE
❖ XBEE
Tarang wireless modules are low to medium-power devices and suitable for adding
wireless capability (2.4Ghz ISM band) to any product with serial data interface. The
modules require minimal power and provide reliable delivery of data between devices.
The I/O interfaces provided with the Module help to directly fit into many industrial
applications.
This module functions similar to XBee of DIGI, but of low cost.
Features and Benefits:
1. Point to point, point to multi point, Mesh and peer-to-peer topologies on proprietary stack.
2. Direct Sequence Spread Spectrum technology.
3. Each direct sequence channel has 64K unique network addresses.
4. Transmit Power: 0 dBm.
5. RF data rate: 250 kbps.
6. Acknowledgement mode communication with retries.
7. Power saving modes.
8. Source / destination addressing.
9. Unicast and broadcast communication.
10. Analog to digital conversion and digital I/O line support.
11. Default configuration for ready to use.

Specifications:
Power
Supply Voltage
3.3 to 3.6V
Transmit Current
45mA
Idle/Receive Current
50mA
Power-down Current
<10 µA
General
Rating Frequency ISM 2.4 - 2.4835 GHz
Maximu Transmit Power Output 1mW (+0 dBm)
RF Data Rate 250 kbps
Receiver Sensitivity -92 dBm
Serial Interface Data Rate Upto 115200 baud
Operating Temperature -40 to 85 °C
Antenna Options Chip Antenna, Wire Antenna
Antenna Connector MMCX
Network
Supported Network Topologies Peer-to-peer, point to multipoint & Mesh
Number Of Channels 16 direct sequence channels
Addressing Options PAN ID, Channel and addresses
Mechanical
Dimensions 37mm x 26mm.
Interface Connector 20 pin receptacles, 2.00mm pitch.

➢ DC Motor:
A DC motor relies on the fact that like magnet poles repel and unlike magnetic poles
attract each other. A coil of wire with a current running through it generates
an electromagnetic field aligned with the center of the coil. By switching the current on
or off in a coil its magnetic field can be switched on or off or by switching the direction
of the current in the coil the direction of the generated magnetic field can be switched
180°. A simple DC motor typically has a stationary set of magnets in the stator and
an armature with a series of two or more windings of wire wrapped in insulated stack
slots around iron pole pieces (called stack teeth) with the ends of the wires terminating on
a commutator. The armature includes the mounting bearings that keep it in the center of
the motor and the power shaft of the motor and the commutator connections. The winding
in the armature continues to loop all the way around the armature and uses either single
or parallel conductors (wires), and can circle several times around the stack teeth. The
total amount of current sent to the coil, the coil's size and what it's wrapped around
dictate the strength of the electromagnetic field created. The sequence of turning a
particular coil on or off dictates what direction the effective electromagnetic fields are
pointed. By turning on and off coils in sequence a rotating magnetic field can be created.
These rotating magnetic fields interact with the magnetic fields of the magnets
(permanent or electromagnets) in the stationary part of the motor (stator) to create a force
on the armature which causes it to rotate. In some DC motor designs the stator fields use
electromagnets to create their magnetic fields which allow greater control over the motor.
At high power levels, DC motors are almost always cooled using forced air.
The commutator allows each armature coil to be activated in turn. The current in the coil
is typically supplied via two brushes that make moving contact with the commutator.
Now, some brushless DC motors have electronics that switch the DC current to each coil
on and off and have no brushes to wear out or create sparks.
Different number of stator and armature fields as well as how they are connected provide
different inherent speed/torque regulation characteristics. The speed of a DC motor can
be controlled by changing the voltage applied to the armature. The introduction of
variable resistance in the armature circuit or field circuit allowed speed control. Modern
DC motors are often controlled by power electronics systems which adjust the voltage by
"chopping" the DC current into on and off cycles which have an effective lower voltage.
Since the series-wound DC motor develops its highest torque at low speed, it is often
used in traction applications such as electric locomotives, and trams. The DC motor was
the mainstay of electric traction drives on both electric and diesel-electric locomotives,

street-cars/trams and diesel electric drilling rigs for many years. The introduction of DC
motors and an electrical grid system to run machinery starting in the 1870s started a
new second Industrial Revolution. DC motors can operate directly from rechargeable
batteries, providing the motive power for the first electric vehicles and today's hybrid
cars and electric cars as well as driving a host of cordless tools. Today DC motors are still
found in applications as small as toys and disk drives, or in large sizes to operate steel
rolling mills and paper machines.
If external power is applied to a DC motor it acts as a DC generator, a dynamo. This
feature is used to slow down and recharge batteries on hybrid car and electric cars or to
return electricity back to the electric grid used on a street car or electric powered train
line when they slow down. This process is called regenerative braking on hybrid and
electric cars. In diesel electric locomotives they also use their DC motors as generators to
slow down but dissipate the energy in resistor stacks. Newer designs are adding large
battery packs to recapture some of this energy.
Motors are one of the primary mechanisms by which robots move. Some motors can be
attached to wheels that drive a robot around. Other motors might cause joints in a robot
limb to move. Yet others might move the control surfaces of a robotic airplane or
submarine. A robot might have many different kinds of effectors to perform specific
tasks, but many of these effectors are being moved around by motors.
What motors do is convert the electrical energy that powers the robot into mechanical
energy that allows the robot to do work. There are two measurements of a motor that are
important for understanding how much work it can do.
Speed is what the maximum speed of the motor is. This is usually measured
in revolutions per minute, or RPM. 1 RPM means that the axle of the motor will turn
completely around a circle once in a minute, which is very slow. Even a very cheap DC
motor will have a speed rating of at least 1000 RPM.

➢ VOICE RECORDER :
Amplifier:
A common theme in many electronic circuits is the need to increase the level of voltage,
current, or power present. This need is satisfied by some form of amplifier.
Amplifiers may be categorized under a number of general headings including such
characteristics as frequency response, class of operation, and the type of circuitry
employed. The following general categories are commonly used:
Classification according to frequency responses are: Audio frequency; Radio frequency;
Wideband Amplifiers.
Classification according to operating point is: Linear and Non-linear Amplifiers
Classification according to signal amplitude is: Small-signal; Large-signal; Pre-amplifier;
and Power Amplifiers.
Classification according to class of operations is: Class A; Class B; Class AB; Class C;
and Class D Amplifiers.
Classification according to circuitry employed is: Single-stage; Multi-stage; a.c.coupled;
d.c.coupled; Discrete; Integrated; and Hybrid Amplifiers.
The important parameters regarding the Amplifier circuit designing are Gain, Input
impedance, Output impedance, Frequency response, Bandwidth, Phase shift, and
Efficiency. Not all of the above characteristics or parameters will be important in any
given application. An essential first stage in designing an amplifier will be to select those
characteristics which are important and then specify the parameters required.
Note that the input impedance of any pre-amplifier should be high in comparison to that
of the input transducer (but not so high that excessive noise and hum is produced).
Conversely, the output impedance of the amplifier should be low in comparison to the
output transducer. Here transducer may be Microphones or Loud Speakers.
Sound Transducers: The transducer, also known as a sensor, is a device which converts
physical parameters to be measured, viz., Sound, Pressure, Temperature etc, into a
corresponding quantity. If the transducer converts physical quantity to useful electronic
signals, such as voltage and current analogous, then it is an Electrical Transducer.

Electronic measurement of sound is of popular application among hobby and application
fields.
Sound Sensors: Electronic devices such as Loud Speakers can generate electromagnetic
energy whilst other devices such as Condenser Microphones can sense audible energy.
Audible frequency range is from about 300 Hertz to 3000Hertz. Although various types
of sound sensors are available, for general purpose applications Microphones are
employed. This sound sensor is useful in listen bug or listening amplifier circuits.
➢ TRANSDUCER [ SOUND ]
➢ INTRODUCTION:
Operational Amplifier: Designed originally for analogue computer and control
applications, the operational amplifier has found its way into almost every field of
electronics. Today’s Integrated Circuit Op-Amps offer many advantages over their
discrete component predecessors. Circuit design is greatly simplified with the added
bonus that the characteristics of the latest generation of Op-Amps, far exceed those of
their predecessors.
An Op-amp is a direct coupled high gain amplifier, usually consisting of one or more
differential amplifiers and usually followed by a level translator and an output stage.
Output stage is generally a push-pull or push-pull complementary symmetry pair. An Op-
amp is available as single IC package. The maximum common mode voltage that can be
applied to an Op-amp without disturbing its proper function is of the order +13 V or –13
V.
The desirable characteristics of an Op-Amps are: the open-loop voltage gain should be
very high (ideally infinity); the input resistance should be very high (ideally infinity); the
output resistance should be very low (ideally zero); full power bandwidth should be as
wide as possible; slew rate and CMRR should be as large as possible; and input offset
should be as small as possible.
The considerable parameter of any Op-Amps is measured by it s CMRR value.
CMRR(Common Mode Rejection Ratio ):The CMRR is defined as the ratio of
differential voltage gain “ Ad” to the common voltage gain “Acm” , i.e.,
CMRR = Ad / Acm .

The higher the value of CMRR ,better is the matching between two input terminals and
smaller is the output common mode voltage .
fields.
Audible frequency range is from about 300 Hertz to 3000Hertz. Although various types
of sound sensors are available, for general purpose applications Microphones are
employed. This sound sensor is useful in listen bug or listening amplifier circuits.

CIRCUIT DIAGRAM OF SOUND TRANSDUCER
Parts List:
SEMICONDUCTORS
IC1 741 Op-Amp IC 1
RESISTORS
R1 3.3 K Ohm, ¼ Watt Carbon Type 1
R3 & R4 10 K Ohm, ¼ Watt Carbon Type 1
R5 1 M Ohm Preset 1
CAPACITIORS
C1 0.04 µF Ceramic Disc type 1
C2 10 µF/25V Electrolytic 1
MISCELLANEOUS
TR1 AC 188 PNP TRANSISTOR 1
TR2 AC 187 PNP TRANSISTOR 1
COND. CONDENSER MIKE 1
C
2
C4
C3
TR
2
TR
1
R
4
R3
R2
R1
R5
OUT
PUT
COND.
MIC
IC
1
7
4
2
3
C
1
+V
cc
Gnd

This simple Amplifier cum Comparator module is used where the main circuit needs the
transducer which catches the very low pitch sound waves and amplifies sufficiently and
fed to it. The heart of this module is an Op-Amp IC whose gain is very high. Thus the
small level of information will be easily picked and amplified to required level by it. The
gain is depended on its feedback resistor R5 value. The Sound Sensor Microphone
changes its internal resistance value according to the sound waves it receives. As this
varying resistance is converted into voltage signals [which is supplied through resistor
R1] and inputted to Op-Amp’s Inverter input pin-2 with the help of coupling capacitor
C1. Thus the corresponding voltage signals observed at output pin-6 of Op-Amp are
further amplified by two transistor pairs. This output is coupled to required stage using a
coupling capacitor C3. The preset R5 is adjusted for fine tuning of the Op-Amp and its
gain. Here the output signal varies as the input sound receives i.e., output is directly
proportional to input.
NOTE: Since the output of a microphone is very small (typically a few mill volts) there is
often significant signal loss and micro phonic noise may also be generated by the cable.
Microphones frequently have to be connected to amplification and/or recording equipment
via several meters of screened cable.
➢ PRE-AMPLIFIER
Introduction:
Amplifier: A common theme in many electronic circuits is the need to increase the level of
voltage, current, or power present. This need is satisfied by some form of amplifier.
Amplifiers may be categorised under a number of general headings including such
characteristics as frequency response, class of operation, and the type of circuitry
employed. The following general categories are commonly used:
Classification according to frequency responses are: Audio frequency; Radio frequency;
Wideband Amplifiers.
Classification according to operating point is: Linear and Non-linear Amplifiers
Classification according to signal amplitude is: Small-signal; Large-signal; Pre-amplifier;
and Power Amplifiers.

Classification according to class of operations is: Class A; Class B; Class AB; Class C; and
Class D Amplifiers.
Classification according to circuitry employed is: Single-stage; Multi-stage; a.c.coupled;
d.c.coupled; Discrete; Integrated; and Hybrid Amplifiers.
The important parameters regarding the Amplifier circuit designing are Gain, Input
impedance, Output impedance, Frequency response, Bandwidth, Phase shift, and
Efficiency. Not all of the above characteristics or parameters will be important in any given
application. An essential first stage in designing an amplifier will be to select those
characteristics which are important and then specify the parameters required.
Note that the input impedance of any pre-amplifier should be high in comparison to that of
the input transducer (but not so high that excessive noise and hum is produced).
Conversely, the output impedance of the amplifier should be low in comparison to the
output transducer. Here transducer may be Microphones or Loud Speakers.
fields.
Audible frequency range is from about 300 Hertz to 3000Hertz. Although various types of
sound sensors are available, for general purpose applications Microphones are employed.
This sound sensor is useful in listen bug or listening amplifier circuits.

Parts List:
RESISTORS
R1 15 K Ohm, ¼ Watt Carbon Type 1
R2 270 K Ohm, ¼ Watt Carbon Type 1
R3 22 M Ohm, ¼ Watt Carbon Type 1
CAPACITIORS
C1 1000F/25V Ceramic Disc type 1
C2 100 KPF Ceramic Disc type 1
MISCELLANEOUS
TR1 BC149 NPN TRANSISTOR 1
D1 1N4007 RECITFIER DIODE 1
COND. CONDENSER MIKE 1
X1 0 – 12V, 300 Ma Transformer 1
C
1
D1
1
1
X1
230AC
R1 R2
R4
C2
2
R3
COND.
MIC
output
TR1

This simple module is used where the main Amplifier circuit needs the transducer which
catches the very low pitch sound waves and pre-amplifies sufficiently and fed to it. This
pre-amplifier circuit is a simplest conceivable small-signal amplifier stage. The NPN
Transistor TR1, having current gain of 150, is connected in common-emitter mode and
operated in class A with bias current fed back from the collector, via R4.
The working principle of this circuit is straight-one: the 230 V AC is step-downed to 12
volts AC and further half-wave rectified using diode D1 and filtered by electrolytic
capacitor C1. This rectified supply is used to drive the pre-amplifier stage. The condenser
microphone which is biased through R1 changes its internal-resistance with respect to the
picked sound waves. This varying signal drives the Transistor into saturation region.
Hence the corresponding amplified output signals are observed at Transistor’s collector
terminal. The input signals from condenser microphone and output signals at collector
terminal are coupled by means of capacitors [like C2]. Since these coupling condensers
determine the low frequency response of the stage.
A collector current of approximately 1 mA is typical and hence the quiescent voltage
appearing at the collector will be approximately 4.3 V. The voltage gain provided by this
pre-amplifier is depend on the value of transistor current gain and effective load
resistance. The clarity and gain is superior to Amplifiers designed using Op-Amps.
NOTE: As this circuit deals with mains power supply, care should be taken while dealing
with it.

➢ VOICE CHIP
PRE-RECORDED VOICE CHIP:
The IC APR 33 – V2 is a 28-pin single voice recording & play back chip,
which can store the message of length 20 to 30 seconds.
FUNCTIONAL BLOCK DIAGRAM
AG
C
Anai
n
Anao
ut
Mic in
Mic
ref
Osc
R Internal
oscillato
r
Powersupplies
Switched
capacitor filter
Sample &
hold
circuit
Analog write
and read
circuits
Non-volatile
Analog storage
memory array
Automatic
gain control
(AGC)
Switched
capacitor filter
Device
control
Pre
amp
.
Am
p
Am
p
VccD VccA VssD VssA
/Rec
L
/play
E
/LED

FEATURES of V/C
Single chip, high quality voice recording and play back solution.
• No external IC is required.
• Minimum external components.
• Non volatile flash memory technology.
• No battery back up required.
• 100k record cycles[typical]
• 100 year message retention[typical].
Single message of 20 to 30 sec, with external resistor selection.
User friendly, easy to use operation.
• Programming and development systems not required.
• Level activated recrding & edge activated playback switches.
Low power consumption.
• Operating current : 25mA [ typical, no load ]
• Standby current : 1uA [ typical, no-load ]
Automatic power down feature for longer battery life .
Chip enable pin for simple message expansion.
Single 5v power supply.
➢ GENERAL DISCRIPTION
The APR 33 device offers true single chip solid state storage capability and requires no
software or microcontroller support. It provides high quality recording and playback with
a single 20 to 30 sec message. It is deal for portable voice recorders, toys, and many other
consumer and industrial applications.
Invox proprietary analog/multilevel storage technology is implemented in advanced flash
non volatile memory cells, each of which can typically store more than 256 voltage
levels. The APR 33 device stores and reproduces voice signals in their natural forms,
eliminating the distortion that is often introduced by encoding and compression. The
device combines a small size with low power consumption, non volatility, and ease of use
for cost effective solution to voice recording and playback.

CIRCUIT DESCRIPTION; When pins are connected as shown in this ex. the operating
modes are as follows:
Record mode [level activated]
The LED pin will go low during the actual recording process to provide a visual
indication if an LED light is connected to this pin. A single voice message of up to 20 sec
can be recorded. The chip is record mode as long as the / RecL pin stays low [level
activated]. If the message lasts longer than 20 sec than the recording will automatically
terminate after the last available memory cell is written. If the message is shorter than 20
sec the recording operation will stop when the RecL pin goes high. The speaker driver is
automatically tristated during the recording operation. Message of up to 30 sec can be
recorded by using different OscR resistor values [see table 1].

CIRCUIT DIAGRAM OF VOICE RECORDING CHIP
6V
BA
C2
C1
C3
C4
S
P
K
R
2
M
.PHONE
R3 R4
C5
R5
C7
C6
SWZ
R6
VC
C
6.4 KHz – 52K
5.5 KHz – 67K
4.0 KHz – 89K
SP
-
SP
+
VSS
D
NU
1
NC
NC
NC
OSC
R
/C
E
N
C
N
C
N
C
NC
NC
VSSA
VCCA
MICIN
MICREF
AGC
ANAIN
ANA
OUT
NC
/PLAY
E
NC
/LED
NU 2
/RECL
VCCD
28
27
26
25
24
23
22
21
20
19
18
16
15
17
1
2
3
4
5
6
7
8
9
10
11
13
14
12
APR 33

PARTS LIST:
Playback mode [edge activated]
Playback always starts from the beginning of the message. The chip is in playback mode
after the/play E pin pulses low [edge activated]. Playback will stop immediately when the
play E pin pulses low for the second time. If the newly recorded message is shorter than
the previously recorded will be played after the new message is played back. The i/p
preamplifier AGC, and main amp. circuits are disabled during playback.
Standby mode [ /CE = “0” ]
The chip will automatically return to the standby state after recording or playback
operation is completed.
Power down mode [ /CE = “1” ]
The chip is always in standby state. No recording or playback is allowed. Current
consumption is typically less than 1uA.
NOTES NC = No connect [ must be floating ]
NU = not used [ must be grounded ]
Pin 23 & 27 have internal pull up resistors.
The typical sampling freq is 6.4 KHz with OscR = 52KE.
Table 1 shows the typical dependence of the sampling freq and total voice duration on the
OscR resistor value.
RESISTORS CAPACITORS SEMICONDUCTORS
R1 - 56K C1 - 47/16V IC1 - APR 33 V2
R2,3 - 4K-7 C2,3,4,6 - .1/16Vdisc IC2 - 7806
R5 - 220K C5 - 22/50V 28 Pin IC socket
R4,6 - 1K C7 - 4.7/25V 5mm red LED
2 pin cond. Micswitch (2 pcs) –push to on (k8)

Table 1. typical dependence of sampling freq and total voice duration on OscR resistor
value.
(VccA – VccD – 5V; VssA – OV ; TA – 25C )
Pin OscR Typical sampling
Frequency
Typical total voice
Duration.
52 KE
67 KE
89 KE
6.4KHz
5.3KHz
4.0KHz
20 S
24 S
30 S

➢ ARM PROCESSOR:
LPC 2148 MICROCONTROLLER
ARM7 family includes the ARM7TDMI, ARM7TDMI-S, ARM720T, and ARM7EJ-
S processors. The ARM7TDMI core is the industry’s most widely used 32-bit embedded
RISC microprocessor solution. Optimized for cost and power-sensitive applications, the
ARM7TDMIsolution provides the low power consumption, small size, and high
performance needed in portable, embedded applications. The ARM7TDMI-S core is the
synthesizable version of theARM7TDMI core, available in both VERILOG and VHDL,
ready for compilation into processes supported by in-house or commercially
Available synthesis libraries. The ARM720T hard microcell contains the ARM7TDMI
core, 8kb unified cache, and a Memory Management Unit (MMU)that allows the use of
protected execution spaces and virtual memory. This macro cell is compatible with
leading operating systems including Windows CE, Linux, palm OS, and SYMBIAN OS.
ARM 7 FAMILIES
The ARM7EJ-S processor is a synthesizable core that provides all the benefits of
theARM7TDMI – low power consumption, small size, and the thumb instruction set –
while also incorporating ARM’s latest DSP extensions and Jazelle technology, enabling
acceleration of java- based applications. Compatible with the ARM9™, ARM9E™, and
ARM10™ families, and Strong-Arm® architecture software written for the ARM7TDMI
processor is 100% binary-compatible with other members of the ARM7 family and
forwards-compatible with the ARM9,ARM9E, and ARM10 families, as well as products
in Intel’s Strong ARM and x scale architectures. This gives designers a choice of
software-compatible processors with strong price-performance points. Support for the
ARM architecture today includes: Operating systems such as Windows CE,Linux, palm
OS and SYMBIAN OS. More than 40 real-time operating systems, including qnx, Wind
River’s works and mentor graphics’

Fig ARM7TDMI Core Diagram
Figure shows the ARM7TDMI Core Diagram. The ARM7TDMI core is based on
the Non Neumann architecture with a 32-bit data bus that carries both instructions and
data. Load, store, and swap instructions can access data from memory. Data can be 8-bit,
16-bit, and 32-bit.

ARM7TDMI processor core
The ARM7TDMI processor core implements the ARMv4T Instruction Set Architecture
(ISA).This is a superset of the ARMv4 ISA which adds support for the 16-bit Thumb
instruction set. Software using the Thumb instruction set is compatible with all members
of the ARM Thumb family, including ARM9, ARM9E, and ARM10families
REGISTERS
The ARM7TDMI core consists of a 32-bit data path and associated control logic. This
data path contains 31 general-purpose 32-bit registers, 7 dedicated 32-bit registers
coupled to a barrel-shifter, Arithmetic Logic Unit, and multiplier
.
MODES AND EXCEPTIONS
The ARM7TDMI supports seven modes of operation:
▪ User mode
▪ Fast Interrupt (FIQ)
▪ Interrupt (IRQ)
▪ Supervisor mode
▪ Abort mode
Undefined mode and System mode. All modes other than User are privileged modes.
These are used to service hardware interrupts, exceptions, and software interrupts. Each
privileged mode has an associated Saved Program Status Register (SPSR). This register is
use to save the state of the Current Program Status Register (CPSR) of the task
immediately before the exception occurs. In these privileged modes, mode-specific
banked registers are available. These are automatically restored to their original values on
return to the previous mode and the saved CPSR restored from the SPSR. System mode
does not have any banked registers. It uses the User mode registers. System mode runs
tasks that require a privileged processor mode and allows them to invoke all classes of
exception.

PROCESSOR STATES
The ARM7TDMI processor can be in one of two states:
ARM state:
In ARM state, 16 general registers and one or two status registers are accessible atany
one time. The ARM state register set contains 16 directly accessible registers: R0 toR15.
All of these except R15 are general-purpose, and may be used to hold either data
or address value the registers available to the programmer in each mode.
Fig Register Organization in ARM state

In figure the thumb state registers are shown. The THUMB state register set is subset of
the ARM state set. The programme has direct access to eight general registers, R0-R7,as
well as the Program Counter (PC), a stack pointer register (SP), a link register (LR), and
the CPSR. There are banked Stack Pointers, Link Registers and Saved Process Status
Registers(SPSRs) for each privileged mode. The registers available to the programmer in

each mode, in THUMB state, are illustrated in Figure.3.3 Register Organization in
THUMB state.
AMBA Bus Architecture:
The ARM7 Thumb family processors are designed for use with the Advanced
Microcontroller Bus Architecture (AMBA) multi-master on-chip bus architecture.
AMBA is an open standard that describes a strategy for the interconnection and
management of functional blocks that makes up a System-on-Chip (SoC).The AMBA
specification defines three buses:
•Advanced System Bus (ASB)
•Advanced High-performance Bus (AHB)
•Advanced Peripheral Bus (APB).ASB and AHB are used to connect high-performance
system modules. APB offers a simpler interface for low-performance peripherals.
Advantages:
•Small Dice
•Lower Power Consumption
•Simple decoding
•Higher performance
•Easy to implement an effective pipelined structure
Disadvantages
•Performance depends on compiler
•Poor code density
•RISC has a fixed size of instruction format
•Small number of instructions

Applications
Using the ARMv7 architecture, ARM can strengthen its position as a low-instruction
execution. power/performance leader while conquering new markets to carry its cores up
in high performance and down in the low-cost high-volume domain of the
microcontroller ARM designs the technology that lies at the heart of advanced digital
products, from wireless, networking and consumer entertainment solutions to imaging,
automotive, security and storage devices. ARM’s comprehensive product offering
includes 16/32-bit RISC microprocessors, data engines, 3D processors, digital libraries,
embedded memories, peripherals, software and development tools, as well as analog
functions and high-speed connectivity products
LPC2148 MICROCONTROLLER
LPC2148 microcontroller board based on a 16-bit/32-bit ARM7TDMI-S CPU with real-
time emulation and embedded trace support, that combine microcontrollers with
embedded high-speed flash memory ranging from 32 kB to 512 kB. A 128-bit wide
memory interface and unique accelerator architecture enable 32-bit code execution at the
maximum clock rate. For critical code size applications, the alternative 16-bit Thumb
mode reduces code by more than 30% with minimal performance penalty. The meaning
of LPC is Low Power Low Cost microcontroller. This is 32 bit microcontroller
manufactured by Philips semiconductors (NXP).Due to their tiny size and low power
consumption, LPC2148 is ideal for applications where miniaturization is key
requirement, such as access control and point-of-sale. The Thumb set’s 16-bit instruction
length allows it to approach twice the density of standard ARM code while retaining most
of the ARM’s performance advantage over a traditional16-bit processor using 16-bit
registers. This is possible because Thumb code operates on the same 32-bit register set as
ARM code. Thumb code is able to provide up to 65 % of the code size of ARM, and 160
% of the performance of an equivalent ARM processor connected to a 16-bitmemory
system.

Features of LPC2148 MICROCONTROLLER :
❖ 16-bit/32-bit ARM7TDMI-S microcontroller in a tiny LQFP64 package.
❖ 8 kB to 40 kB of on-chip static RAM and 32 kB to 512 kB of on-chip flash
memory;128-bit wide interface/accelerator enables high-speed 60 MHz operation.
❖ In-System Programming/In-Application Programming (ISP/IAP) via on-chip boot
loader software, single flash sector or full chip erase in 400 ms and programming
of 256 B in 1 ms Embedded ICE RT and Embedded Trace interfaces offer real-
time debugging with the on-chip Real Monitor software and high-speed tracing
of
❖ USB 2.0 Full-speed compliant device controller with 2 kB of endpoint RAM. In
addition, the LPC2148 provides 8 kB of on-chip RAM accessible to USB by
DMA.
❖ One or two (LPC2141/42 Vs, LPC2144/46/48) 10-bit ADCs provide a total of
6/14analog inputs, with conversion times as low as 2.44 ms per channel.
❖ Single 10-bit DAC provides variable analog output (LPC2148 only)
❖ Two 32-bit timers/external event counters (with four capture and four compare
channels each), PWM unit (six outputs) and watchdog.
❖ Low power Real-Time Clock (RTC) with independent power and 32kHz clock
input
❖ Multiple serial interfaces including two UARTs (16C550), two Fast I2C-bus(400
kbit/s), SPI and SSP with buffering and variable data length capabilities.
❖ Up to 45 of 5 V tolerant fast general purpose I/O pins in a tiny LQFP64Package.
❖ Up to 21 external interrupt pins available.
❖ 60 MHz maximum CPU clock available from programmable on-chipPLL with
settling time of 100 ms.
❖ On-chip integrated oscillator operates with an external crystal from 1 MHzto 25
MHz and Power saving modes include Idle and Power-down
❖ Individual enable/disable of peripheral functions as well as peripheral clock
scaling for additional power optimization.
❖ Processor wake-up from Power-down mode via external interrupt or BOD.
❖ CPU operating voltage range of 3.0 V to 3.6 V (3.3 V ± 10 %) with 5 V tolerant
I/O.
ARCHITECTURE

Inthe following figure the architecture of the LPC2148 microcontroller is shown.
Fig 2.4 LPC2148 Microcontroller Architecture

PIN DIAGRAM:
The pin diagram of the LPC2148 microcontroller is show in the below figure 2.5. The
LPC2148 microcontroller has 2 ports and each port comprises of 32 pins. So in total the
microcontroller has 64 pins.

ARCHITECTURALOVERVIEW
The ARM7TDMI-S is a general purpose 32-bit microprocessor, which offers
high performance and very low power consumption. The ARM architecture is based on
Reduced Instruction Set Computer (RISC) principles, and the instruction set and related
decode mechanism are much simpler than those of micro programmed Complex
Instruction Set Computers (CISC).This simplicity results in a high instruction throughput
and impressive real-time interrupt response from a small and cost-effective processor
core. Pipeline techniques are employed so that all parts of the processing and memory
system scan operate continuously. Typically, while one instruction is being executed, its
successor is being decoded, and a third
instruction is being fetched from memory. The ARM7TDMI-S processor also employs a
unique architectural strategy known as Thumb, which makes it ideally suited to high-
volume applications with memory restrictions, or applications where code density is an
issue. The key idea behind Thumb is that of a super-reduced instruction set. Essentially,
theARM7TDMI-S processor has two instruction sets:
❖The standard 32-bit ARM set.
❖A 16-bit Thumb set.
The Thumb set’s 16-bit instruction length allows it to approach twice the density
of standard ARM code while retaining most of the ARM’s performance advantage over a
traditional16-bit processor using 16-bit registers. This is possible because Thumb code
operates on the same32-bit register set as ARM code. Thumb code is able to provide up
to 65 % of the code size of ARM, and 160 % of the performance of an equivalent ARM
processor connected to a 16-bitmemory system. The particular flash implementation in
the LPC2141/42/44/46/48 allows for full speed execution also in ARM mode. It is
recommended to program performance critical and short code sections (such as interrupt
service routines and DSP algorithms) in ARM mode. The impact on the overall code size
will be minimal but the speed can be increased by 30% over Thumb mode.

ON- CHIP FLASH PROGRAM MEMORY
The LPC2141/42/44/46/48 incorporates a 32kB, 64kB, 128kB, 256kB and 512kB flash
memory system respectively. This memory may be used for both code and data storage.
Programming of the flash memory may be accomplished
in several ways. It may be programmed In System via the serial port. The application
program may also erase and/or program the flash while the application is running,
allowing a great degree of flexibility for data storage field firmware upgrades, etc. Due to
the architectural solution chosen for an on-chip boot loader, flash memory available for
user’s code on LPC2141/42/44/46/48 is 32 kB, 64 kB, 128 kB, 256 kB and500 kB
respectively. The LPC2141/42/44/46/48 flash memory provides a minimum of
100,000erase/write cycles and 20 years of data-retention.
ON-CHIP STATIC RAM
On-chip static RAM may be used for code and/or data storage. The SRAM may be
accessed as 8-bit, 16-bit, and 32-bit. The LPC2141, LPC2142/44 and LPC2146/48
provide 8 kB,16 kB and 32 kB of static RAM respectively. In case of LPC2146/48 only,
an 8 kB SRAM block intended to be utilized mainly by the USB can also be used as a
general purpose RAM for data storage and code storage and execution.
MEMORY MAP
The LPC2141/42/44/46/48 memory map incorporates several distinct regions, as shown
inFig 4.4 Memory map. In addition, the CPU interrupt vectors may be remapped to allow
them to reside in either flash memory (the default) or on-chip static RAM.

INTERRUPT CONTROLLER
The Vectored Interrupt Controller (VIC) accepts all of the interrupt request inputs and
categorizes them as Fast Interrupt Request (FIQ), vectored Interrupt Request (IRQ), and
non-vectored IRQ as defined by programmable settings. The programmable assignment
scheme means that priorities of interrupts from the various peripherals can be
dynamically assigned and adjusted. Fast interrupt request (FIQ) has the highest priority.
If more than one request is assigned to FIQ,the VIC combines the requests to produce the
FIQ signal to the ARM processor. The fastest possible FIQ latency is achieved when only
one request is classified as FIQ, because then the FIQ service routine does not need to
branch into the interrupt service routine but can run from the interrupt vector location. If
more than one request is assigned to the FIQ class, the FIQ service routine will read a
word from the VIC that identifies which FIQ source(s) is (are) requesting an interrupt.
Vectored IRQs have the middle priority. Sixteen of the interrupt requests can be assigned
to this category. Any of the interrupt requests can be assigned to any of the 16 vectored
IRQ slots, among which slot 0 has the highest priority and slot 15 has the lowest. Non-
vectored IRQs have the lowest priority. The VIC combines the requests from all the
vectored and non-vectored IRQs to produce the IRQ signal to the ARM processor. The
IRQ service routine can start by reading are gister from the VIC and jumping there. If any
of the vectored IRQs are pending, the VIC provides the address of the highest-priority
requesting IRQs service routine, otherwise it provides the address of a default routine that
is shared by all the non-vectored IRQs. The default routine can read another VIC register
to see what IRQs are active. Each peripheral device has one interrupt line connected to
the Vectored Interrupt Controller, but may have several internal interrupt flags. Individual
interrupt flags may also represent more than one interrupt source.

PIN CONNECT BLOCK
The pin connect block allows selected pins of the microcontroller to have more than one
function. Configuration registers control the multiplexers to allow connection between
the pin and the on chip peripherals. Peripherals should be connected to the appropriate
pins prior to being activated and prior to any related interrupt(s) being enabled. Activity
of any enabled peripheral function that is not mapped to a related pin should be
considered undefined. The Pin Control Module with its pin select registers defines the
functionality of the microcontroller in a given hardware environment. After reset all pins
of Port 0 and 1 are configured as input with the following exceptions: If debug is enabled,
the JTAG pins will assume their JTAG functionality; if trace is enabled, the Trace pins
will assume their trace functionality. The pins associated with the I2C0 and I2C1
interface are open drain.
FAST GENERAL PURPOSE PARALLEL I/O (GPIO)
Device pins that are not connected to a specific peripheral function are controlled by the
GPIO registers. Pins may be dynamically configured as inputs or outputs. Separate
registers allow setting or clearing any number of outputs simultaneously. The value of the
output register may be read back, as well as the current state of the port pins.
LPC2141/42/44/46/48 introduces accelerated GPIO functions over prior LPC2000
devices:
❖ GPIO registers are relocated to the ARM local bus for the fastest possible I/O
timing.
❖ Mask registers allow treating sets of port bits as a group, leaving other bits
unchanged.
❖ All GPIO registers are byte addressable.
❖ Entire port value can be written in one instruction.• Bit-level set and clear
registers allow a single instruction set or clear of any number of bits in one port.
❖ Direction control of individual bits.
❖ Separate control of output set and clear.
❖ All I/O default to inputs after reset.

UARTs
❖ The LPC2141/42/44/46/48 each contains two UARTs. In addition to standard
transmit and receive data lines, the LPC2144/46/48 UART1 also provide a full
modem control handshake interface. Compared to previous LPC2000
microcontrollers, UARTs in LPC2141/42/44/46/48introduce a fractional baud rate
generator for both UARTs, enabling these microcontrollers to achieve standard
baud rate such as 115200 with any crystal frequency above 2 MHz. In addition,
auto-CTS/RTS flow-control functions are fully implemented in hardware (UART1
inLPC2144/46/48 only).
❖ 16 byte Receive and Transmit FIFO.
❖ Register locations conform to ‘550 industry standard.
❖ Receiver FIFO triggers points at 1, 4, 8, and 14 bytes
❖ Built-in fractional baud rate generator covering wide range of baud rates with out a
need for external crystals of particular values.
❖ Transmission FIFO control enables implementation of software (XON/XOFF)Flow
control on both UARTs.
❖ LPC2144/46/48 UART1 equipped with standard modem interface signals. This
Modulealsoprovidesfullsupportforhardwareflowcontrol(auto-CTS/RTS).
I2C-BUS SERIAL I/O CONTROLLER
The LPC2141/42/44/46/48 each contains two I2C-bus controllers. The I2C-bus is
bidirectional, for inter-IC control using only two wires: a serial clock line (SCL),and a
serial data line (SDA). Each device is recognized by a unique address and can operate as
either a receiver-only device (e.g., an LCD driver or a transmitter with the capability to
both receive and send information (such as memory)).Transmitters and/or receivers can
operate in either master or slave mode, depending on whether the chip has to initiate a
data transfer or is only addressed. The I2C-bus is a multi-master bus; it can be controlled
by more than one bus master connected to it. The I2C-bus implemented
inLPC2141/42/44/46/48 supports bit rates up to 400 k bit/s (Fast I2C-bus)

❖ Compliant with standard I2C-bus interface.
❖ Easy to configure as master, slave, or master/slave.
❖ Programmable clocks allow versatile rate control.
❖ Bidirectional data transfer between masters and slaves Multi-master bus (no central
master).
❖ Arbitration between simultaneously transmitting masters without corruption of serial
data on the bus.
❖ Serial clock synchronization allows devices with different bit rates to communicate
via one serial bus.
❖ Serial clock synchronization can be used as a handshake mechanism to suspend and
resume serial transfer.
❖ The I2C-bus can be used for test and diagnostic purposes.
SPIserialI/Ocontroller
The LPC2141/42/44/46/48 each contains one SPI controller. The SPI is a full duplex
serial interface, designed to handle multiple masters and slaves connected to a given bus.
Only a single master and a single slave can communicate on the interface during a given
data transfer. During a data transfer the master always sends a byte of data to the slave,
and the slave always sends a bye of data to the master.
❖Compliant with Serial Peripheral Interface (SPI) specification.
❖Synchronous, Serial, Full Duplex, Communication.
❖Combined SPI master and slave.
❖Maximum data bit rate of one eighth of the input clock rate.

SSP SERIAL I/O CONTROLLERs
The LPC2141/42/44/46/48 each contains one SSP. The SSP controller is capable
of operation on a SPI, 4-wire SSI, or Micro wire bus. It can interact with multiple masters
and slaves on the bus. However, only a single master and a single slave can communicate
on the bus during a given data transfer. The SSP supports full duplex transfers, with data
frames of 4 bits to 16 bits of data flowing from the master to the slave and from the slave
to the master. Often only one of these data flows carries meaningful data.
Compatible with Motorola’s SPI, TI’s 4-wire SSI and National Semiconductor’s Micro
wire buses.
Synchronous serial communication.
Master or slave operation.
8-frame FIFOs for both transmit and receive.
Four bits to 16 bits per frame.
GENERAL PURPOSE TIMERS EXTERNAL EVENT COUNTERS
The Timer/Counter is designed to count cycles of the peripheral clock (PCLK) or an
externally supplied clock and optionally generate interrupts or perform other actions at
specified timer values, based on four match registers. It also includes four capture inputs
to trap the timer value when an input signals transitions, optionally generating an
interrupt. Multiple pins can be selected to perform a single capture or match function,
providing an application with ‘or’ and‘ and’, as well as ‘broadcast’ functions among
them. The LPC2141/42/44/46/48 can count external events on one of the capture inputs if
the minimum external pulse is equal or longer than a period of the PCLK. In this
configuration, unused capture lines can be selected as regular timer capture inputs, or
used as external interrupts.
❖ A 32-bit timer/counter with a programmable 32-bit pre scalar.
❖ External event counter or timer operation.
❖ Four 32-bit capture channels per timer/counter that can take a snapshot of the
timer value when an input signals transitions. A capture event may also optionally
generate an interrupt.

SERIAL COMMUNICATION
RS232 (serial port)
RS-232 (Recommended Standard - 232) is a telecommunications standard for binary
serial communications between devices. It supplies the roadmap for the way devices
speak to each other using serial ports. The devices are commonly referred to as a DTE
(data terminal equipment) and DCE (data communications equipment); for example, a
computer and modem, respectively.RS232is the most known serial port used in
transmitting the data in communication and interface. Even though serial port is harder to
program than the parallel port, this is the most effective method in which the data
transmission requires less wires that yields to the less cost. The RS232 is the
communication line which enables the data transmission by only using three wire links.
The three links provides ‘transmit’, ‘receive’ and common ground .The ‘transmit’ and
‘receive’ line on this connecter send and receive data between the computers. As the
name indicates, the data is transmitted serially. The two pins are TXD & RXD. There are
other lines on this port as RTS, CTS, DSR, DTR, and RTS, RI. The ‘1’ and ‘0’ are the
data which defines a voltage level of 3V to 25V and -3V to -25V respectively.
TTL Logic Levels
When communicating with various micro processors one needs to convert the RS232
levels down to lower levels, typically 3.3 or 5.0 Volts
Here is a cheap and simple way to do that. SerialRS-232 (V.24) communication works
with voltages -15V to +15V for high and low. On the other hand, TTL logic operates
between 0V and +5V. Modern low power consumption logic operates in the range of 0V
and +3.3V or even lower

Table 4.1 TTL Logic Levels
RS-232 TTL LOGIC
-15V….-3V +2V….+5V HIGH
+3V…..+15V 0V…..+0.8V LOW
Thus the RS-232 signal levels are far too high TTL electronics, and the negative RS-232
voltage for high can’t be handled at all by computer logic. To receive serial data from an
RS-232 interface the voltage has to be reduced. Also the low and high voltage level has to
be inverted. This level converter uses a Max232 and five capacitors. The MAX232 from
Maxim was the first IC which in one package contains the necessary drivers and receivers
to adapt the RS-232 signal voltage levels to TTL logic.
Successive-Approximation ADCs
A successive-approximation converter is composed of a digital-to-analog converter
(DAC), a single comparator, and some control logic and registers. When the analog
voltage to be measured is present at the input to the comparator, the system control logic
initially sets all bits to zero. Then the DAC’s most significant bit (MSB) is set to 1, which
forces the DAC output to 1/2 of full scale(in the case of a 10-V full-scale system, the
DAC outputs 5.0 V). The comparator then compare the analog output of the DAC to the
input signal, and if the DAC output is lower than the input signal, (the signal is greater
than 1/2 full scale), the MSB remains set at 1. If the DAC output is higher than the input
signal, the MSB resets to zero. Next, the second MSB with a weight of 1/4 of full scale
turns on (sets to 1) and forces the output of the DAC to either 3/4 full scale (if the MSB
remained at 1) or 1/4 full scale (if the MSB reset to zero). The comparator once more
compares the DAC output to the input signal and the second bit either remains on (sets to
1) if the DAC output is lower than the input signal, or resets to zero if the DAC output is
higher than the input signal. The third MSB is then compared the same way and the
process continues in order of descending bit weight until the LSB is compared. At the end
of the process, the output register contains the digital code representing the analog input
signal.

Successive approximation ADCs are relatively slow because the comparisons run
serially, and the ADC must pause at each step to set the DAC and wait for its output to
settle. However, conversion rates easily can reach over 1 MHz. Also, 12 and 16-bit
successive-approximation ADCs are relatively inexpensive, which accounts for their
wide use in many PC- based data acquisition systems.
Successive-Approximation ADC 8-Bit, Microprocessor-Compatible, A/D Converters
The ADC080X family is CMOS 8-Bit, successive approximation A/D converters which
use amplified potentiometric ladder and are designed to operate with the 8080A control
bus via three-state outputs. These converters appear to the processor as memory locations
or I/O ports, and hence no interfacing logic is required. The differential analog voltage
input has good common mode- rejection and permits offsetting the analog zero-input
voltage value. In addition, the voltage reference input can be adjusted to allow encoding
any smaller analog voltage span to the full 8 bits of resolution.
Fig Typical Application Schematic

❖ 80C48 and 80C80/85 Bus Compatible - No Interfacing Logic Required
❖ Conversion Time . . . . . . . . . . . . . . . . . . . . . . . . . . <100μs
❖ Easy Interface to Most Microprocessors
❖ Will Operate in a “Stand Alone” Mode
❖ Differential Analog Voltage Inputs
❖ Works with Bandgap Voltage References
❖ TTL Compatible Inputs and Outputs
❖ On-Chip Clock Generator
❖ Analog Voltage Input Range (Single + 5V Supply) . . . . . . . . . . . . . . . . . . . . . . 0V
to 5V
❖ No Zero-Adjust Required

❖ Design and Realization
❖ 80C48 and 80C80/85 Bus Compatible - No Interfacing Logic Required
❖ Conversion Time . . . . . . . . . . . . . . . . . . . . . . . . . . <100μs
❖ Easy Interface to Most Microprocessors
❖ Will Operate in a “Stand Alone” Mode
❖ Differential Analog Voltage Inputs
❖ Works with Band gap Voltage References
❖ TTL Compatible Inputs and Outputs
❖ On-Chip Clock Generator
❖ Analog Voltage Input Range (Single + 5V Supply) . . . . . . . . . . . . . . . . . . . . . . 0V
to 5V
❖ No Zero-Adjust Required
LCD MODULE
LCDs can add a lot to any application in terms of providing an useful interface for the
user, debugging an application or just giving it a "professional" look. The most common
type of LCD controller is the Hitachi 44780 which provides a relatively simple interface
between a processor and an LCD. Using this interface is often not attempted by
inexperienced designers and programmers because it is difficult to find good
documentation on the interface, initializing the interface can be a problem and the
displays themselves are expensive.
The most common connector used for the 44780 based LCDs is 14 pins in a row, with pin
centres’ 0.100" apart. The pins are wired as:
DATA
R/_S
R/_W
E
450
nSec
LCD DATA WRITE WAVEFORM

Pins Description
1 Ground
2 Vcc
3 Contrast Voltage
4 "R/S" _Instruction/Register Select
5 "R/W" _Read/Write LCD Registers
6 "E" Clock
7 - 14 Data I/O Pins
The interface is a parallel bus, allowing simple and fast reading/writing of data to and
from the LCD.
The LCD Data Write Waveform will write an ASCII Byte out to the LCD's screen. The
ASCII code to be displayed is eight bits long and is sent to the LCD either four or eight
bits at a time. If four bit mode is used, two "nibbles" of data (Sent high four bits and then
low four bits with an "E" Clock pulse with each nibble) are sent to make up a full eight
bit transfer. The "E" Clock is used to initiate the data transfer within the LCD.
Sending parallel data as either four or eight bits are the two primary modes of operation.
While there are secondary considerations and modes, deciding how to send the data to the
LCD is most critical decision to be made for an LCD interface application.

The different instructions available for use with the 44780 are shown in the table below:
R/S R/W D7 D6 D5 D4 D3 D2 D1 D0 Instruction/Description
4 5 14 13 12 11 10 9 8 7 Pins
0 0 0 0 0 0 0 0 0 1 Clear Display
0 0 0 0 0 0 0 0 1 * Return Cursor and LCD to Home Position
0 0 0 0 0 0 0 1 ID S Set Cursor Move Direction
0 0 0 0 0 0 1 D C B Enable Display/Cursor
0 0 0 0 0 1 SC RL * * Move Cursor/Shift Display
0 0 0 0 1 DL N F * * Set Interface Length
0 0 0 1 A A A A A A Move Cursor into CGRAM
0 0 1 A A A A A A A Move Cursor to Display
0 1 BF * * * * * * * Poll the "Busy Flag"
1 0 D D D D D D D D Write a Character to the Display at the
Current Cursor Position
1 1 D D D D D D D D Read the Character on the Display at the
Current Cursor Position
The bit descriptions for the different commands are:
"*" - Not Used/Ignored. This bit can be either "1" or "0"
Most LCD displays have a 44780 and support chip to control the operation of the LCD.
The 44780 is responsible for the external interface and provides sufficient control lines
for sixteen characters on the LCD. The support chip enhances the I/O of the 44780 to
support up to 128 characters on an LCD. From the table above, it should be noted that the
first two entries ("8x1", "16x1") only have the 44780 and not the support chip. This is
why the ninth character in the 16x1 does not "appear" at address 8 and shows up at the
address that is common for a two line LCD.
The Character Set available in the 44780 is basically ASCII. It is "basically" because
some characters do not follow the ASCII convention fully (probably the most significant

difference is 0x05B or "" is not available). The ASCII Control Characters (0x008 to
0x01F) do not respond as control characters and may display funny (Japanese) characters.
The last aspect of the LCD to discuss is how to specify a contrast voltage to the
Display. Experts typically use a potentiometer wired as a voltage divider. This will
provide an easily variable voltage between Ground and Vcc, which will be used to
specify the contrast (or "darkness") of the characters on the LCD screen. You may find
that different LCDs work differently with lower voltages providing darker characters in
some and higher voltages do the same thing in others.
Liquid crystal panel service life 100,000 hours minimum at 25 o
C -10 o
C
3.3 definition of panel service life
❖ Contrast becomes 30% of initial value
❖ Current consumption becomes three times higher than initial value
❖ Remarkable alignment deterioration occurs in LCK cell layer
❖ Unusual operation occurs in display functions
Safety
LCD Contrast Circuit
+Vcc
Pin-3 Contrast
LCD
10K pot
Shift Register LCD Data Write
R6
D0
D1
Dn
E
LCD
E Clock
S/R
Process
or
Data
Data
Clock
0
0

❖ If the LCD panel breaks, be careful not to get the liquid crystal in your mouth. If
the liquid crystal touches your skin or clothes, wash it off immediately using soap
and plenty of water.
Handling
❖ Avoid static electricity as this can damage the CMOS LSI.
❖ The LCD panel is plate glass; do not hit or crush it.
❖ Do not remove the panel or frame from the module.
❖ The polarizing plate of the display is very fragile; handle it very carefully
❖ Mounting and Design
❖ Mount the module by using the specified mounting part and holes.
❖ To protect the module from external pressure; leave a small gap by placing
transparent plates (e.g. acrylic or glass) on the display surface, frame, and
polarizing plate
❖ Design the system so that no input signal is given unless the power-supply voltage
is applied.
❖ Keep the module dry. Avoid condensation; otherwise the transparent electrodes
may break.
❖ Storage
❖ Store the module in a dark place, where the temperature is 25 o
C - 10 o
C and the
humidity below 65% RH.
❖ Do not store the module near organic solvents or corrosive gases.

CHAPTER 8:
APPLICATIONS & FUTURE ENHANCEMENT
8.1: APPLICATIONS
1. This project can be implemented to increase the independent mobility of blind and elderly
travellers .
2. Restricted zones.
3. Wherever mobility is important there we can implement this project.
8.2: FUTURE ENHANCEMENT
There is always chance to improve any system as research & development is an endless
process. Our system is no exception to this phenomenon. The following developments
can be done in future to improve the blind users' mobility in terms of safety and speed by
these devices are: Sonic Torch,. Mowat Sensor,. Sonic Pathfinder.

CHAPTER 9:
ADVANTAGES & DISADVANTAGES
9.1: ADVANTAGES
1. Secure and reliable communication.
2. Leading edge technology that meets today's and tomorrow's needs.
3. This not only detects the obstacles but can also guide the user around them. This
combination of obstacle detection and avoidance reduces the conscious effort required
from the user.
4. Continuous scanning of the environment relieves the user from additional actions,
therefore reducing the required physical and mental effort.
5. This can provide the user with a panoramic view of the environment, covering a sector of
120 degrees.
9.2: DISADVANTAGES
1. One time investment cost.
2. It has to be planted throughout the city.

CHAPTER 10:
RESULT/CONCLUSION
As this project is based on micro-controller(ARM7LPC2148) and Zigbee
technology is used to transmit data this can be of great use for the blind or
visually impaired. and helps the blind people to detect the location of the
place when they are walking by ARM controller with synthetic speech
output.

CHAPTER 11:
GENERAL COMPONENTS
➢ RESISTORS :
In many electronic circuit applications the resistance forms the basic part of the circuit.
The reason for inserting the resistance is to reduce current or to produce the desired
voltage drop. These components which offer value of resistance are known as resistors .
Resistors may have fixed value i.e., whose value cannot be changed and are known as
fixed resistors. Such of those resistors whose value can be changed or varied are known
as variable resistors.
There are two types of resistors available. They are :
❖ Carbon resistors .
❖ Wire wound resistors .
Carbon resistors are used when the power dissipation is less than 2W because they are
smaller and cost less. Wire wound resistors are used where the power dissipation is more
than 5W . In electronic equipments carbon resistors are widely used because of their
smaller size .
All resistors have three main characteristics:
❖ Its resistance R in ohms (from 1 ohm to many mega ohms).
❖ Power rating (from several 0.1W to 10 W).
❖ Tolerance (in percentage).

➢ RESISTOR COLOR CODING:
The carbon resistors are small in size and are color coded to indicate their resistance
value in ohms. Different colors are used to indicate the numeric values. The dark colors
represent lower values and the lighter colors represent the higher values. The color code
has been standardized by the electronic industries association.
The color bands are printed at one end of the resistors and are read from the left to right.
The first color band closed to the edge indicates the first digit in the value of resistance
.The second band gives the second digit. The third band gives the number of zero’s after
two digits . The resulting number is the resistance in ohms . A fourth band indicates the
tolerance i.e., to indicate how accurate the resistance value is , the bands are shown in the
figure 1.
Fig. 1: Colour code for Resistor

➢ PRESET:
There are two general categories of variable resistors:
❖ General purpose resistors.
❖ Precision resistors.
The general purpose type can again be wire wound type and carbon type .These follows
either linear or logarithmic law. The precision type are always wire wound and follow a
linear law .The variable resistors can be broadly classified as potentiometer , rheostats ,
presets and decade resistance boxes.
The general purpose wire wound potentiometers are available in 1, 2, 3 and 4 watts. The
usual tolerances ratings 10 % and 20% are available. The widely used potentiometers are
of the standard diameters 19mm, 31mm, and 44mm. The temperature coefficient depends
on the wire used and on the resistors values. The resolution of these wire wound resistors
is proper than carbon resistors because the wiper has to move from one winding to the
other, where as in carbon potentiometers it is continuous. These resistors are highly
linear, the linearity falling with 1%.

➢ CAPACITORS:
Devices which can store electronic charge are called capacitors. Capacitance can be
understood as the ability of a dielectric to store electric charges. Its unit is Farad, named
after the Michael Faraday. The capacitors are named according to the dielectric used.
Most common ones are air, paper, and mica, ceramic and electrolytic capacitors.
Physically a capacitor has conducting plates separated by an insulator or the dielectric.
The plates of the capacitor have opposite charge, this gives rise to an electric field .In
capacitor the electric field is concentrated in the dielectric between the plates.
Like resistors, capacitors are also crucial to the correct working of nearly every
electronic circuit and provide us with a means of storing electrical energy in the form of
an electric field. Capacitors have numerous applications including storage capacitors in
power supplies, coupling of A.C. signals between the stages of an amplifier, and
decoupling power supply rails so that, As far as A.C. signal components are concerned,
the supply rails are indistinguishable from zero volts.

➢ TYPES OF CAPACITORS:
❖ DISC CAPACITORS :
In the disk form, silver is fired on to both sides of the ceramic to form the conductor
plates. The sheets are then baked and cut to the appropriate shape and size & attached by
pressure contact and soldering . These have high capacitance per unit volume and are
very economical. The disks are lacquered or encapsulated in plastic or Phenolic molding.
Round disk are used at high voltages the capacitance of values upto 0.01F can be
obtained. They have tolerance of +20% or –20%. In general these capacitors have voltage
ratings up to 750 V D.C.
❖ ELECTROLYTIC CAPACITORS :
These capacitors derive the name from electrolyte which is used as a medium to produce
high dielectric constants. These capacitors have low value for large capacitances at low
working voltages.
There are two types of Electrolytic capacitors:
❖ Aluminum Electrolytic capacitors.
❖ Tantalum electrolytic capacitors.

Electrolytic capacitors are used in circuits that have combination of D.C. voltage and
A.C. The D.C. voltage maintains the polarity . They are used as ‘ripple filter ‘ where
large capacitance are required at low cost in small space . They are also used as ‘biased
capacitors ‘ and ‘decoupling capacitors ‘ and even as ‘coupling capacitors ‘ in R- C
amplifier.
➢ COLOR CODING :
Mica and tubular ceramic capacitors are color coded to indicate a capacitance value . As
coding is necessary only for very small sizes, color coded capacitors value is also in the
pF. The colors are the same as for the resistor coding from black for ‘0’ upto white for
‘9’. Mica capacitors use ‘six dot code system’.
❖ SIX DOT CODE :
Here the top row is read from the left to right and the bottom from right to left .The dot
indicates the following:
(1) . White . (2). Digit . (3). Digit. (4) . Multiplier. (5) . Tolerance . (6) . Class.
White for the first dot indicates the coding. The capacitance value is read from the next
three dots . If the first dot is silver it indicates paper capacitor. The white colored band
indicates the left and specifies the temperature coefficient . The next three colors indicate
the value of capacitance . For example Brown, Black, Brown = 100 pF.

➢ DIODES:
To ensure unidirectional flow of liquid we use mechanical valves in its path. By properly
arranging these valves in a system we get useful devices such as pumps and locomotives.
In the field of electronics too we have a valve called semiconductor diode (a counterpart
of thermionic valve) for controlling the flow of electric current in one direction. But we
use these diodes in circuits for limited purposes like converting AC to DC, by passing
EMF etc. a diode allows current to pass through it provided it is forward biased and the
biasing voltage is more than potential barrier (forward voltage drop) of the diode.
➢ AUTOMATIC SWITCHOVER TO BATTERY:
An uninterrupted power supply (UPS) is necessary for a main operated clock. This
facility is very useful in transistors and two in ones for recording or listening to news
programs. A relay can do this job with a battery backup. But the relay takes several
milliseconds before it makes contact. Moreover, it is costly and occupies space.

The same task can be achieved with a single diode. Just connect a germanium diode
DR50 (D1) as shown in fig 1.when the power is available form the eliminator or the
external power source, the gadget will use the power from it. As points A and B are at
same potential, the external power is remove, point B will be at higher potential that point
A i.e. D1 is forward biased and current flows from the battery. In no case the voltage of
the eliminator or the external power source should be less than the voltage of the battery.
Otherwise, the current will flow from the battery during mains operation also and the
battery will be drained quickly.
Fig 1: Automatic switchover to battery
D1
DR
50
BATTER
Y
FROM
BATTERY
ELIMINAT
OR
TO REST OF
THE
CIRCUIT OF
THE GADGET
B
A
+
+

➢ TRANSISTOR:
The transistor an entirely new type of electronic device is capable of achieving
amplification of weak signals in a fashion comparable and often superior to that realized
by vacuum tubes. Transistors are far smaller than vacuum tube, have no filaments and
hence need no heating power and may be operates in any position. They are mechanically
strong, hence practically unlimited life and can do some jobs better than vacuum tubes.
Invented in 1948 by J. Bardeen and W.H.Brattain of Bell Telephone Laboratories, a
transistor has now become the heart of most electronic appliance. Though transistor is
only slightly more the 45 years old, yet it is fast replacing vacuum tubes in almost all
applications.
A transistor consists of two pn junction formed by sand witching either p-type or n-type
semiconductor between a pair of opposite type. Accordingly, there are two types of
transistors namely:
❖ n-p-n transistor
❖ p-n-p transistor

An n-p-n is composed of two n-type semiconductors separated a by thin section of p-type.
However, a p-n-p is formed by two p-section separated by a thin section of n-type.
❖These are two pn junctions. Therefore, a transistor may be regarded as a combination of
two diodes connected back to back.
❖There are 3 terminals, taken from each type of semiconductor.
❖The middle section is very thin layer. This is the most important factor in the
functioning of a transistor.
Origin of the name “transistor “: When new devices are invented, scientists often try to
device a name that will appropriately describe the device. A transistor has two pn
junctions. As the discussed later one junction is forward biased and the other is reversed
biased. The forward biased junction has low resistance path whereas the reverse biased
junction has low resistance path whereas the reverse biased junction has a high resistance
path. The weak signal is introduced in the low resistance circuit and output is taken from
the high resistance circuit. Therefore, a transistor transfers a signal from a low resistance
to high resistance. The prefix ‘tans’ means the signal transfer property of the device while
‘istor’ classifies it as a solid element in the same general family with resistors.
➢ NAMING THE TRANSISTOR TERMINALS:
A transistor (pnp or npn) has three sections of doped semiconductors. The section on one
side is the emitter and the section on the opposite side is the collector. The middle section
is called the base and forms two junctions between the emitter and collector.
❖Emitter: - The section on one side that supplies charge carriers (electrons or holes) is
called the emitter. The emitter is always forward biased w.r.t base so that it can supply
a large number of majority carriers.

❖Collector: - The section on the other side that collects the charge is called the collector.
The collector is always reversing biased. Its function is to remove charges from its
junction with the base.
❖Base: - The middle section, which forms to pn junctions between the emitter and
collector, is called base. The base emitter junction is forward biased, allowing low
resistance for the emitter circuit. The base-collector junction is reversed biased and
provides high resistance in the collector circuit.
➢ CHARACTERISTICS OF TRANSISTORS
Whenever we have to decide about the applications of a transistor certain question arises.
Some of these are – how much amplification gets from it? What is the highest frequency
upto which it can be used? How much power output could we get from it? And what
should be the values of different components used in the circuits? The answers to these
entire questions lie in the electrical properties of the transistor. These properties depend
on the size, manufacturing techniques and materials used in the manufacturer of transistor
and are know as characteristics. Transistor manufacturers give these characteristics in the
data sheets published by them.
❖ Current gain factor ‘alpha’ ()
❖ Current gain factor ‘beta’ ()
❖ Input resistance (Rin)
❖ Output resistance (Rout)
❖ Cut-off frequency (F  and F)
❖ Leakage current (I ‘co)
❖ Maximum permissible limits:
1. Maximum collector voltage (Vceo)
2. Maximum emitter current (IC Max)
3. Maximum Power dissipation (P max)

➢ RELAY:
A relay is an electrically operated switch. Many relays use an electromagnet to operate a
switching mechanism mechanically, but other operating principles are also used. 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. The first relays were used in long distance telegraph
circuits, repeating the signal coming in from one circuit and re-transmitting it to another.
Relays were used extensively in telephone exchanges and early computers to perform
logical operations.
A type of relay that can handle the high power required to directly drive an electric motor
is called a contactor. Solid-state relays control power circuits with no moving parts,
instead using a semiconductor device to perform switching. Relays with calibrated
operating characteristics and sometimes multiple operating coils are used to protect
electrical circuits from overload or faults; in modern electric power systems these
functions are performed by digital instruments still called "protective relays".

➢ BASIC DESIGN AND OPERATION:
A simple electromagnetic relay consists of a coil of wire surrounding a soft iron core, an
iron yoke which provides a low reluctance path for magnetic flux, a movable iron
armature, and one or more sets of contacts (there are two in the relay pictured). The
armature is hinged to the yoke and mechanically linked to one or more sets of moving
contacts. It is held in place by a spring so that when the relay is de-energized there is an
air gap in the magnetic circuit. In this condition, one of the two sets of contacts in the
relay pictured is closed, and the other set is open. Other relays may have more or fewer
sets of contacts depending on their function. The relay in the picture also has a wire
connecting the armature to the yoke. This ensures continuity of the circuit between the
moving contacts on the armature, and the circuit track on the printed circuit board (PCB)
via the yoke, which is soldered to the PCB.
When an electric current is passed through the coil it generates a magnetic field that
attracts the armature, and the consequent movement of the movable contact(s) either
makes or breaks (depending upon construction) a connection with a fixed contact. If the
set of contacts was closed when the relay was de-energized, then the movement opens the
contacts and breaks the connection, and vice versa if the contacts were open. When the
current to the coil is switched off, the armature is returned by a force, approximately half
as strong as the magnetic force, to its relaxed position. Usually this force is provided by a
spring, but gravity is also used commonly in industrial motor starters. Most relays are
manufactured to operate quickly. In a low-voltage application this reduces noise; in a
high voltage or current application it reduces arcing.
When the coil is energized with direct current, a diode is often placed across the coil to
dissipate the energy from the collapsing magnetic field at deactivation, which would
otherwise generate a voltage spike dangerous to semiconductor circuit components. Some
automotive relays include a diode inside the relay case. Alternatively, a contact protection
network consisting of a capacitor and resistor in series (snubber circuit) may absorb the
surge. If the coil is designed to be energized with alternating current (AC), a small copper
"shading ring" can be crimped to the end of the solenoid, creating a small out-of-phase
current which increases the minimum pull on the armature during the AC cycle.[1]
A solid-state relay uses a thyristor or other solid-state switching device, activated by the
control signal, to switch the controlled load, instead of a solenoid. An optocoupler (a

light-emitting diode (LED) coupled with a photo transistor) can be used to isolate control
and controlled circuits.
➢ DC Motor:
The direct current (DC) motor is one of the first machines devised to convert electrical
power into mechanical power. Permanent magnet (PM) direct current convert electrical
energy into mechanical energy through the interaction of two magnetic fields. One field
is produced by a permanent magnet assembly; the other field is produced by an electrical
current flowing in the motor windings. These two fields result in a torque which tends to
rotate the rotor. As the rotor turns, the current in the windings is commutated to produce a
continuous torque output Permanent magnet (PM) motors are probably the most
commonly used DC motors, but there are also some other type of DC motors (types
which use coils to make the permanent magnetic field also).
DC motors operate from a direct current power source. Movement of the magnetic field is
achieved by switching current between coils within the motor. This action is called
"commutation". Very many DC motors (brush-type) have built-in commutation, meaning
that as the motor rotates, mechanical brushes automatically commutate coils on the rotor.
Motor speed control of DC motor is nothing new. A simplest method to control the
rotation speed of a DC motor is to control it's driving voltage. The higher the voltage is,
the higher speed the motor tries to reach. In many applications a simple voltage
regulation would cause lots of power loss on control circuit, so a pulse width modulation
method (PWM) is used in many DC motor controlling applications. In the basic Pulse
Width Modulation (PWM) method, the operating power to the motors is turned on and
off to modulate the current to the motor. The ratio of "on" time to "off" time is what
determines the speed of the motor.

Sometimes the rotation direction needs to be changed. In normal permanent magnet
motors, this rotation is changed by changing the polarity of operating power (for example
by switching from negative power supply to positive or by interchanging the power
terminals going to power supply). This direction changing is typically implemented using
relay or a circuit called an H bridge.
Besides "brush-type" DC motors, there is another DC motor type: brushless DC motor.
Brushless DC motors rely on the external power drive to perform the commutation of
stationary copper winding on the stator. This changing stator field makes the permanent
manger rotor to rotate. A brushless permanent magnet motor is the highest performing
motor in terms of torque / vs. weight or efficiency. Brushless motors are usually the most
expensive type of motor. Electronically commutated, brush-less DC motor systems are
widely used as drives for blowers and fans used in electronics, telecommunications and
industrial equipment applications. There is wide variety of different brush-less motors for
various applications. Some are designed to to rotate at constant speed (those used in disk
drives) and the speed of some can be controlled by varying the voltage applid to them
(usually the motors used in fans). Some brushless DC motors have a built-in tachometer
which gives out pulses as the motor rotates (this applies to both disk drive motors and
some computer fans).
In general, users select brush-type DC motors when low system cost is a priority, and
brushless motors to fulfil other requirements (such as maintenance-free operation, high
speeds, and explosive environments where sparking could be hazardous). Brush type DC
motors are used in very many battery powered appliances. Brushless DC motors are
commonly used in applications like DC powered fans and disk drive rotation motors.

➢ Introduction To Integrated Circuits:
All modern digital systems rely on the use of integrated circuits in which hundreds of
thousands of components are fabricated on a single chip of silicon. A relative measure of
the number of individual semiconductor devices within the chip is given by referring to
its ‘scale of integration’. The following terminology is commonly applied.
Scale of integration Abbreviation Number of logic gates
Small SSI 1 to 10
Medium MSI 10 to 100
Large LSI 100 to 1000
Very large VLSI 1000 to 10,000
Super large SLSI 10,000 to 100,000

➢ Encapsulation:
The most common package used to encapsulate an integrated circuit, and that with which
most reader will be familiar, is the plastic dual-in-line (DIL) type. These are available
with a differing number of pins depending upon the complexity of the integrated circuit
in question and, in particular, the need to provide external connections to the device.
Conventional logic gates, for example, are often supplied in 14-pin or 16-pin DIL
packages, whilst microprocessors (and their more complex support devices) often require
40-pins or more.
➢ Identification:
When delving into an unfamiliar piece of equipment, one of the most common problems
is that of identifying the integrated circuit devices. To aid us in this task, manufacturers
provide some coding on the upper surface of each chip. Such a coding generally includes
the type number of the chip (including some of the generic coding), the manufacturer’s
name (usually in the form of prefix letters), and the classification of the device (in the
form of a prefix, infix or suffix).
In many cases the coding is further extended to indicate such things as encapsulation,
date of manufacture, and any special characteristics of the device. Unfortunately, all of
this potentially useful information often leads to some considerable confusion due to
inconsistencies in marking from one manufacturer to the next!
➢ Logic Families:
The integrated circuit device on which modern digital circuitry depends belongs to one or
other of several ‘logic families’. The term simply describes the type of semiconductor
technology employed in the fabrication of the integrated circuit. This technology is
instrumental in determining the characteristics of a particular device. This, however, is
quite different from its characteristics, and encompasses such important criteria as supply
voltage, power dissipation, switching speed and immunity to noise.
The most popular logic families, at least as far as the more basic general purpose devices
are concerned, are complementary metal oxide semiconductor (CMOS) and transistor
transistor logic (TTL). TTL also has a number of sub-families including the popular low
power Schottky (LS-TTL) variants.
The most common range of conventional TTL logic devices is known as the ‘74’ series.
These devices are, not surprisingly, distinguished by the prefix number 74 in their coding.
Thus devices coded with the numbers 7400, 7408, 7432 and 74121 are all members of
this family which is often referred to as ‘Standard TTL’. Low power Schottky variants of

these devices are distinguished by an LS infix. The coding would then be 74LS00,
74LS08, 74LS32 and 74LS121.
Popular CMOS devices from part of the ‘4000’ series and are coded with an initial prefix
of 4. Thus 4001, 4174, 4501 and 4574 are all CMOS devices. CMOS devices are
sometimes also given a suffix letter; A to denote the ‘original’ (now obsolete) unbuffered
series, and B to denote the improved (buffered) series. A UB suffix denotes an
unbuffered B-series device.
Infix letters Meaning
C CMOS version of a corresponding TTL device
F ‘Fast’ – a high speed version of the device
H High speed version
S Schottky (a name resulting from the input circuit Configuration)
HC High speed CMOS version (with CMOS compatible inputs)
HCT High speed CMOS version (with TTL compatible inputs)

CHAPTER 12:
PCB DESIGNING & SOLDERING TECHNIQUES
12.1: PCB DESIGNING:
1. Design your circuit board. Use PCB computer-aided design (CAD) software to draw your
circuit board. You can also use a perforated board that has pre-drilled holes in it to help
you see how your circuit board's components would be placed and work in reality.
2. Buy a plain board that is coated with a fine layer of copper on one side from a retailer.
3. Scrub the board with a scouring pad and water to make sure the copper is clean. Let the
board dry.
4. Print your circuit board's design onto the dull side of a sheet of blue transfer paper. Make
sure the design is oriented correctly for transfer.
5. Place the blue transfer paper on the board with the circuit board's printed design against
the copper.
6. Lay a sheet of ordinary white paper over the blue paper. Following the transfer paper's
instructions, iron over the white and blue paper to transfer the design onto the copper
board. Iron every design detail that appears near an edge or corner of the board with the
tip of the iron.
7. Let the board and blue paper cool. Peel the blue paper slowly away from the board to see
the transferred design.
8. Examine the transfer paper to check for any black toner from the printed design that
failed to transfer to the copper board. Make sure the board's design is oriented correctly.

9. Replace any missing toner on the board with ink from a black permanent marker. Allow
the ink to dry for a few hours.
10. Remove exposed parts of the copper from the board using ferric chloride in a process
called etching.
11. Put on old clothes, gloves and safety goggles.
12. Warm the ferric chloride stored in a non-corrosive jar and sealed with a non-corrosive lid,
in a bucket of warm water. Do not heat it above 115 F (46 C) to prevent toxic fumes from
being released.
13. Pour only enough ferric chloride to fill a plastic tray that has plastic risers in it to rest the
circuit board on. Be sure to do this in a well-ventilated space.
14. Use plastic tongs to lay the circuit board face down on the risers in the tray. Allow 5 to 20
minutes, depending on the size of your circuit board, for the exposed copper to drop off
the board as it etches away. Use the plastic tongs to agitate the board and tray to allow for
faster etching if necessary.
15. Wash all the etching equipment and the circuit board thoroughly with plenty of running
water.
16. Drill 0.03 inch (0.8 mm) lead component holes into your circuit board with high-speed
steel or carbide drill bits. Wear safety goggles and a protective mask to protect your eyes
and lungs while you drill.
17. Scrub the board clean with a scouring pad and running water. Add your board's electrical
components and solder them into place.

12.2: SOLDERING TECHNIQUES
Soldering is the only permanent way to ‘fix’ components to a circuit. However, soldering
requires a lot of practice as it is easy to ‘destroy’ many hours preparation and design
work by poor soldering. If you follow the guidelines below you have a good chance of
success
Use a soldering iron in good condition. Inspect the tip to make sure that it is not past good
operation. If it looks in bad condition it will not help you solder a good joint. The shape
of the tip may vary from one soldering iron to the next but generally they should look
clean and not burnt.
A PCB eraser is used to remove any film from the tracks. This must be done carefully
because the film will prevent good soldering of the components to the PCB. The track
can be checked using a magnified glass. If there are gaps in the tracks, sometimes they
can be repaired using wire but usually a new PCB has to be etched

The heated soldering iron should then be placed in contact with the track and the
component and allowed to heat them up. Once they are heated the solder can be applied.
The solder should flow through and around the component and the track. Having
completed soldering the circuit the extended legs on the components need to be trimmed
using wire clippers. The circuit is now ready for testing.

CHAPTER 13:
REFERENCES
1. ARM7DI Data Sheet"; Document Number ARM DDI 0027D; Issued: Dec 1994.
2. Sakr, Sharif. "ARM co-founder John Biggs". Engadget. Retrieved December 23, 2011.
"[...] the ARM7-TDMI was licensed by Texas Instruments and designed into the Nokia
6110, which was the first ARM-powered GSM phone."
3. "D-Link DSL-604+ Wireless ADSL Router - Supportforum - eXpansys
Sverige". 090506 expansys.se
4. Andrew (bunnie) Huang. "On MicroSD Problems". Bunnie Studios. "This is comparable
to the raw die cost of the controller IC, according to my models; and by making the
controllers very smart (the Samsung controller is a 32-bit ARM7TDMI with 128k of
code), you get to omit this expensive test step while delivering extra value to customers"
5. ARM Architecture Reference Manual.
6. Electronic Communication Systems – George Kennedy
7. Electronics in Industry - George M.Chute
8. Principles of Electronics - V.K.Mehta
9. www.electronicsforu.com
10. www.howstuffworks.com
11. Telecommunication Switching, Traffic and Networks – J.E.Flood
Hanjiang Luo, Kaishun Wu, Zhongwen Guo, Lin Gu, Zhong Yang and Lionel M. N “SID: Ship
Intrusion Detection with Wireless Sensor Networks” International Conference on Distributed
Computing Systems on 2011.

Travel Assistant For Blind With Dynamic User Input For Location Based Alerts Using ARM7 And XBee (REPORT)

More Related Content

Similar to Travel Assistant For Blind With Dynamic User Input For Location Based Alerts Using ARM7 And XBee (REPORT) (20)

Recently uploaded (20)

Travel Assistant For Blind With Dynamic User Input For Location Based Alerts Using ARM7 And XBee (REPORT)