Apptronics Review Volume1 - Rajagiri School of Engineering

Apptronics Review Volume1 - Rajagiri School of Engineering
Volume 1, Issue 5, 2008 December 30
Annual Issue
Introducing science journals
From the HoD’s desk
Academic Bulimia
Academic bulimia as the name implies is an ‘intake
disorder’ in academic matters. Reading without thinking
and reproducing it without understanding is characteristics
of this disorder. This happens to be manifest among
persons of all walks of life in doing their tasks. It is of great
concern when the student community is habituated to this
Why is this happening? It is mainly due to poor time
management, difficulty in concentrating and negative
attitude towards that task. Every time you put off something
you dislike, you strengthen the habit of not doing it. You
may be uncertain about your priorities, goals and
objectives. If you observe the work habits of people who
have achieved outstanding success they invariably show
a well designed pattern of schedule.
How can we outgrow this? First of all identify the
goals, strengths and weaknesses. Start organizing your
books, materials, study table and room. Fix your schedule;
calculate your hours of study, coaching and relaxation time.
Devise a study / work time table. Always set realistic goals
and discipline to use time wisely. Goals should be specific
and measurable as possible. Frequently revise and update
your goals. As a growing person, your needs will change
over a period of time.
A new year is a good time to dig out all things undone
and begin to tackle them right now. I wish you all an
organised, structured and effective 2009.
It is another new year! It is time to look back and
check for the errors, mistakes, the pitfalls and the
wrong doings. It is time to see what can be done
not to repeat those.
Journal of Geophysical Research (JGR)
Journal of the American Geophysical Union(AGU).
Founded in 1896 by the AGU’s then president Louis A.
Publishes original scientific research on physical,
chemical, and biological processes.
Contributes to the understanding of the Earth, Sun and
solar system, and all of their environments and
Was entitled Terrestrial Magnetism at its founding.
Was entitled Terrestrial Magnetism and Atmospheric
Electricity from 1899-1948.
In 1980, JGR was split into 3 sections- JGR—Space
Physics, JGR—Solid Earth, and JGR—Oceans. Four
more sections were added subsequently- JGR—
Atmospheres in 1984, JGR—Planets in 1991, JGR—Earth
Surface in 2003, and JGR—Biogeosciences in 2005.
Scope of each section
JGR—Oceans covers physical, biological, and chemical
JGR—Solid Earth focuses on the physics and chemistry
of the solid Earth and the liquid core of the Earth,
geomagnetism, paleomagnetism, , seismology, geodesy,
gravity, and tectonophysics.
JGR—Space Physics covers aeronomy and
magnetospheric physics, cosmic rays, and heliospheric
JGR—Planets covers the geology, geophysics,
geochemistry, satellites, asteroids, rings, comets, and
meteorites; planetary origins; and planetary detection.
Let your efforts turn successful.
Published by HOD, AEI, Rajagiri School of Engineering and Technology, Kochi- 682039.
For internal circulation only
Observations/Comments PRM
Advanced audio coding Meena V
Smartquill Rahul Mohan S7 AEI
Under graduate enginering
project PRM
Hart protocol Anu George S7 AEI
Bio instrumentation
Bio metrics and fingerscan
Jasna K A
Shalini Varma S7 AEI
Human motion regeneration
using sensors Mary Hexy
CMRR enhancement techniques Kiran Stanley S7 AEI
ZigBee Jino
Satellite telephones Nixon Varghese S3 AEI
Index for volume 1
Renewable source
... A column by PRM.
I have always been of the view that laboratory work
and project work have a major role in undergraduate
engineering courses. Not that theory papers do not have
any role. Definitely, theory papers, like the one on reliability,
can also help to induce engineering way of thinking and
behaviour in students. Of course, it all depends on how the
course is delivered. Importance of method of handling the
course has much more significance in the case of laboratory
work and project activities. In this issue I would like to invite
your attention to a specific observation on the way in which
we have been handling one experiment.
It is about an experiment for S3 as part of Circuits Lab.
Objective of the experiment is determining the CE
characteristics of a BJT.
I found all students giving the transistor type number
as BC 547instead of BC547B. I went through records of senior
students also. This has been the case always. There are three
varieties of BC547: BC547A, BC547B, BC547C. Limiting values
of collector current, collector-base voltage, collector-emitter
voltage, etc. are the same for all BC547. As you know it is a
proelectron numbering scheme where the first letter stands for
the material (A for germanium, B for silicon, C for gallium
arsenide, and D for other compound material), and the second
letter specifies the type of device (A for low power diode, B for
varactor, C for audio frequency low power transistor, etc.). The
last letter A, B or C (There are some other types with the last
letter from A to E.) shows the range of beta values. Values of
beta for BC547B range from 200 to 450, and the typical value is
given to be 290. This differentiation of beta range is not being
noted at all, and the students are found to use typical value of
beta as 100. You may guess the consequence!
While doing the same experiment I made another
observation, a much more serious one. See the circuit given
below. This is the part of the circuit on the input side normally
Ammeter A measures the base current, and voltmeter V measures the base-emitter voltage. Relation between the base
current and the base-emitter voltage is the input characteristics. [Circuit part for the output characteristics is not shown.]
For a beta value of 250, fixing collector current not to exceed
50 mA [keeping it sufficiently less than the specified maximum
of 100mA] we go for a maximum base current of 200 µA.
For base currents up to 200 µA, what could be the maximum
drop across base-emitter? Remember, it is a low current device.
You must agree that it cannot be more than about 0.75 V; it
cannot have values like 1V or 1.2V. But you verify our students
records[neatly certified!]. You can see values recorded upto
1.5V or more. Can you guess what has gone wrong? Is it that
every student is simply cooking up the values? No, it cannot
be so. Cooked values are generally more accurate than
experimentally observed values. To see what has really
happened, you may first verify the circuit part itself. In actual
experiment, a small change is made in the positioning of
voltmeter, as shown below.
The difference is that the voltmeter now measures not the
voltage across the base-emitter junction, but the sum of the
base-emitter voltage and the drop across the ammeter. In
practice there is a drop across the ammeter. We must make
sure that this drop is much less than the one responsible for
the current. The drop partly decides the accuracy. The reason
for such a change was quite interesting. Ammeter and volt
meter were connected first as shown in the earlier diagram.
But then, the microammeter had to be replaced by a
milliammeter! Base current was so high!! So what is the
solution? Try other combinations of connections, and get
satisfied when the current is in microampere range! [Is it not
very much analogous to that old sarcastic case of searching
for the lost article under a street light when it was actually
lost somewhere else where there is no light!] And, what about
the voltmeter reading? That seemed to be of no concern as
we are using a voltmeter of sufficient range!
The real problem here is that the voltmeter is
drawing large current, and initially when the circuit was wired
as it should be, the ammeter was reading the sum of the
base-emitter current and the current drawn by the voltmeter.
It so happened that the voltmeter current was in mA! In the
revised circuit the voltmeter current is not being monitored,
and so it goes unnoticed. But another fault crept in about
which nobody was bothered, neither the ones in charge nor
even our bright students. Of course, we find pleasure in
making it a habit to practice things entirely different from
what we preach. We are not accustomed to inquire about or
challenge things which we observe to be totally different
from what we have learned. We are not ashamed to draw,
certify, characteristics with diode drops of more than one
volt at low currents.
It is high time that we change our attitude.
Advanced Audio Coding
We have already discussed MP3 and MPEG2 video coding
standards. We have also seen that, at least theoretically, AAC
(Advanced Audio Coding) provides 50% better compression
than MP3. In practice, AAC gives, on an average, the same
quality as MP3 at about 70 % of the bit-rate. Let us get into
details of AAC coding and understand how it provides better
AAC coding technique is a generic standard for coding stereo
and multichannel audio signals. It is specified as part 7 of
MPEG2 standard, and as part 3 of MPEG4 standard. MPEG4AAC is more common, due to its quality, compared to MPEG2
AAC. Advantages offered by AAC over MP3 include support
for more channels, higher sampling frequencies (8-96kHz),
arbitrary bit rate (1-48 kbps), variable frame length (1024 or 128
samples), simpler filter bank (MDCT with higher frequency
resolution of 1024 filters instead of hybrid filter bank), more
flexible and improved joint stereo coding, TNS (temporal noise
shaping), backward prediction and PNS (perceptual noise
substitution). As in MP3, it does non-uniform quantization
and Huffman coding.
The encoder first converts signal in time domain to
frequency domain using MDCT (modified discrete cosine
transform). The transform coefficients are quantized based on
psycho acoustic model and encoded. For error resilience,
internal error correction codes, such as RVLC (reversible
variable length codes), are used. AAC allows block lengths of
128 and 1024 based on signal characteristics. If a transient
occurs, shorter block length is chosen for better temporal
resolution. Longer block length gives better frequency
resolution and is the default block length for better coding
Perceptual coders with high frequency resolution usually
exhibit time varying error at certain frequencies. Signal could
sound distorted due to time variant nature of error and noise
at specific frequencies.
There are 4 AAC profiles.[ Profiles are sets of tools supported
by encoder and decoder.] Low complexity (LC) profile is
the simplest and is most widely used. Main profile (MAIN)
uses backward prediction. MPEG4 AAC has SRS (sampling
rate scalable), LTP (long term prediction) and PNS
(perceptual noise substitution). PNS improves coding
quality of signals, such as speech, with significant amount
of noise. But, noise like signals result in flat spectrum and
coding gain is limited. It also results in inefficient generation
of noise at the decoder side using transmitted spectral lines.
Efficient generation of noise is required for good quality
AAC with SBR (spectral band replication) is known as HEAAC or aacPlus v1 and if PS (parametric stereo) technology
is also included, it becomes HE-AAC v2 (high efficiency
AAC v2) or aacPlus v2.
Modified discrete cosine transform is calculated as
X MDCT (k) = 5 x(n)cos[2Ï/N.(k+1/2)(n+1/2+N/4)]
MPEG4 AAC with MPEG4 video is used commonly in
multimedia applications. The popularity of MPEG4 video
is due to its rich error resilience feature set and
computationally efficient algorithms compared to MPEG4
part 10 or H.264 coding. But H264 can give better
(theoretically 50%) video compression compared to
Note - Based on spectral resolution of time or frequency
mapping, audio coders differ. Coders may be filter bank
coder, transform coder or hybrid coder. Filter banks are
used for low frequency resolution and transform coding
for higher resolution. Uniform or non uniform quantization
technique may be used. Coding scheme may be
companding or Huffman coding.
You get an idea while on the road. You note it on your
(Provided you have a pen with you.)! Forget about such
old and obsolete practices. Buy smartQuill, write in air,
and have it recorded!
“Make devices as small as possible” is present
trend. Computers are getting smaller than handheld. But then,
there is an associated issue. Keyboards become so tiny that
one requires needle-like fingers to operate them. Screens need
constant cursor controls to read even a simple text. The
introduction of SmartQuill has solved some of these problems.
SmartQuill was invented by Lyndsay Williams
in 1997. It is a pen slightly larger than ordinary fountain pen,
with a screen on the barrel. The sleek and stylish pen is
different from other electronic pens in the market today. It
contains an ink cartridge so that users can see what they
write down on paper. It remembers the words written using it.
The SmartQuill contains sensors that record movement by
using the Earth’s gravity. User can enter information by
pushing a button. Users do not have to write on any special
pad in order to record what they write. Information can be
entered using one’s own handwriting. Any platform, like paper,
screen, tablet or even air can be used for writing. The pen
records the information inserted by the user. There is also a
small three-line screen to read the information stored in the
pen. Users can scroll down the screen by tilting the pen. The
pen is then plugged in to an electronic docking station, text
data are transmitted to a desktop computer, printer, modem or
to a mobile telephone to send files electronically.
Technology used in SmartQuill for display is Kopin Corp’s
cyber display technology. Cyber display is a ¼ inch diagonal
LCD that uses circuitry built on a silicon wafer, then removed
and mounted on glass. The displays are integrated to
miniature monitors using their own backlighting, optics, ICS
and packaging. Pen has accelerometers to measure hand
movement in 2 or 3 planes and an on board DSP to convert
hand movements to ASCII characters for pen applications. It
does single character recognition and records cursive letters
It is an interesting idea, and it even comes with a security
attribute. SmartQuill can be trained to recognize only the
owner’s handwriting. If someone else picks your SmartQuill
and tries to write with it, it will refuse to record the information.
It has a computer housed within the pen which permits all
which can be downloaded to PC for decoding. SmartQuill
works by measuring the pen’s movements and matching them
to the movements that produce letters and words programmed
into its memory. Consistency of handwriting, rather than
neatness, is the only condition for accuracy.
The pen can align text irrespective of whether it
is held in left hand or right hand. This is made possible by
using Micro electromechanical systems (MEMS) tilt sensors
to measure tilt angle with respect to earth’s gravity. The
SmartQuill microcontroller reads the angle and then maps the
large screen display onto the small four line display. SmartQuill
can also scroll through pages of display, by tilting it in the
Of course a number of limitations are yet to be
overcome. Only a proto has been developed and tested. The
choice of words is limited presently to what characters the
LCD display driver can show while upside down – only 14 of
the 26 letters of the alphabet are usable in the proto. These 14
characters were processed by anagram software to produce
900 words that used these characters. The proto SmartQuill
has 4MB EEPROM memory. At a time, up to 10 pages of notes
can be stored on this. The data is stored in the memory on the
features of a normal personal organizer.
pen until it is uploaded to the personal computer.
Lyndsay Williams is managing director of Girton Labs Ltd in Cambridge,
UK, responsible for design of new
imaging devices and computers to
aid Alzheimers. She was previously
with Microsoft.
Rahul Mohan S7 AEI
Undergraduate Engineering Project:
HOW? and WHY?
A few days back I got an interesting mail from an X-colleague
of mine. Like me, he also worked in a leading research
organisation for quite a long period, and then took up
teaching. Now he is a professor in a reputed engineering
college. I said that his mail was interesting. It was about
plagiarism. To him every one of his senior students is a
He says that he has not even one student who does any
original work for the project. Every one steals off something
from somewhere. My friend was expressing his helplessness.
I think that I have helped him come out of his real problem.
My long reply should have achieved that.
The issue is not one of his concern alone. I have heard many
a discussion on the same topic. There are eminent teachers
who are committed to the cause of good education who argue
that all projects taken up as part of the course work in
undergraduate level must be original, that sufficient literature
‘search’ must be done to ensure that nobody else has ever
done such a work any time earlier.
I do not agree with these views.
Our university syllabus prescribes project work in two
semesters: the sixth and the eighth.
No period is allotted during the fifth or seventh semester,
though some of us insist that project work be started by the
beginning of the fifth semester itself. We have tried to extend
the project activities to the fifth and seventh semesters in
In the sixth semester the students get hardly 40 class hours
to do the so called mini project. You may insist that another
60 hours are spent outside of class. What original work do
you expect them to do in a total of 100 hours? What do you
expect them to gain from such an ‘original’ work? Where are
you going to place them? What do the industries which are
going to offer them jobs demand from them? Let us be realistic.
We are concerned with engineering education. We are
concerned with imparting knowledge, skill and attitude in the
students which could help them to become efficient
professionals, professional engineers. It must be possible to
define the objectives of the undergraduate engineering
projects with this broad objective. We may define the
objectives as follows.
Our students, when they join an industry or research
organisation, must be able to take up any assignment given
to them with confidence, and work systematically to achieve
the target in scheduled time. Project work in undergraduate
level must be defined to meet this objective. Various steps
Main Steps in a Project Work
1. Identifying a task which can be defined as a project.
It must be simple enough to be realised in the given
time. It must be sufficient enough for the team to be
engaged through out he allotted time.
2. Understanding the essence of the task. Noting
down/identifying the requirement in proper technical
3. Generating the requirement specifications which
will form the input specifications for the design and
4. Evolving a conceptual approach. There could be
more than one conceptual approach.
5. Evolving the respective conceptual designs.
Working out the relative merits and demerits of these
options, and selecting one to proceed. Preparing a
conceptual design report.
6. Preparing for review of the conceptual design.
7. Presenting for review.
8. Making improvements/modifications to the
conceptual design incorporating the review outcomes.
9. Dividing the total work into a number of modules
so that the work can be divided among the group
10. Preparing realisable schedule for the total project.
11. Preparing detailed design report, presenting it for
12. Doing the FMECA (failure mode evaluation and
criticality analysis), incorporating measures to
prevent/minimise the identified failure modes.
13. Identifying components and procuring them.
14. Testing the bought out items before they are put
to use.
15. Developing the project deliverables, both H/W
and S/W.
16. Doing T&E of each subsystem being developed.
17. Integrating the subsystems into the total system.
18. Doing T&E on the total system.
19. Packaging the system.
20. Documenting each stage of activity in a properly
maintained work diary, preparing necessary
documents for specific stages of activities like T&E,
involved in doing a project with such an objective are given
in box.
In addition to meeting the above said objectives we may aim
at making the students learn some new topics like a new
statistics, a programming language and a hardware or software
tool, which we think could be of help to them in future.
May be, I have missed out a few points. It doesn’t matter. It is
all about doing a project with all its minute details. It is all
about getting trained in such activities. It is all about learning
how to do an engineering task. It is all about learning project
Do you see any stage where plagiarism is a serious issue?
Yes, it is an issue if one identifies an already existing work for
his project without acknowledging that. Whenever an idea,
an existing concept , or anything of that sort, is taken from
somewhere or from somebody it must be recorded in the work
diary, and brought properly into the final report.
A few function generators are available in our lab. But you
might have felt that it would be better to have one or two more.
You can go through the specifications of the available ones,
and define somewhat better specifications for your work. No
matter whether such an equipment exists or not. Do not worry
about plagiarism. It does not turn out to be real issues when
the objectives and scope are clearly identified (For sure it is
not claimed to be an original work.).
Understand that the project work is a part of training to mould
the students as engineers. It should be seen with all
Guides may always remain alert to identify some original work
which could be assigned to a student team as a project work.
Of course, nobody need ban any original work; in fact such
work must be encouraged.
Having said all these, let us try our best to take up at least a
few good original developmental work as part of the
undergraduate project. But let us not argue that we will not
permit students to do something which is already there.
Before I conclude, let me remind you that to meet the said
objectives, it is essential that students are made to work on
their own. It is essential that they are monitored and guided
properly. It is to be appreciated that guides have a very
important role to play in imparting proper training to the
students through project work.
Setting an example is not the main
means of influencing another, it is the
only means.
- Albert Einstein
Failure is simply the oppurtunity to
begin again, this time more intelligently.
- Henry Ford
HART Protocol
The HART (Highway Addressable Remote Transducer) was
developed by Rosemount Inc. as a proprietary digital
communication protocol for their smart field instruments. In
1986, it was made an open protocol. The HART protocol
provides backward compatible solution for smart instrument
communication as both 4- 20 mA analogue and digital
communication signals are transmitted simultaneously on the
same cable. This feature made it the most widely used standard
in modern instruments. HART products available now include
process receivers (valves), local (field) controllers, calibrators,
Overview:HART is intended to allow easy calibration, range
setting, damping adjustment, error control, etc. in
microprocessor based systems. It uses FSK modulation to
transmit digital signals between the devices. Logical 1’s are
represented by a frequency of 1.2 kHz and 0’s by a frequency
of 2.2 kHz. These signals are then superimposed on to the 420mA control signals of the device. This feature helps in
adjusting the operating point of the instrument without
affecting its working (on-line calibration) and reduces
operation related risk.
Fig: FSK signals on 4-20mA analogue control signals
The HART communication signals have a frequency range
well above the device control signal (about 10 Hz). So simple
filters can be used to separate control signals and HART
signals. In peer to peer mode only one device is attached to a
device loop and both analogue and digital signals are used
for communication, while in multi drop mode up to 15 devices
are connected to a device loop keeping the analogue signal
at 4mA.
HART protocol follows a master-slave configuration and
allows up to 2 masters (controlling devices like DCS, PLC’s,
handheld HART calibrators, etc.) and many slave devices
like temperature and pressure transmitters.
Anu George S7 AEI
Biometrics and Fingerscan
Read This Paper
presented by : K Motoi,
in : Conference of the IEEE EMBS, August 2007
It’s about
Bio Instrumentation
For several decades considerable amount of research
activity has been directed towards advances and developments
of biomedical instrumentation. These researches lead to new
concepts for measurements such as breath monitoring by
thermal film, heart beat monitoring by electro mechanical film,
bio impedance measurement using spot electrode array, and
electrophysiological measurement using dry electrodes.
Currently available breath monitoring system operates
by inserting a thermistor into patient’s nostril. A new method
that is less intrusive and more useful is being introduced
based on a versicolour thermal film in conjunction with image
processing techniques. Ex-inhalation is displayed as 2D colour
pattern on the film placed under the nose.
Conventional method of heart beat monitoring is by using
microphones as in phonocardiogram (PCG). By using electro
mechanical film type transducer, composed of thin, elastic, three
layered polypropylene films, PCG can be recorded more easily.
Like an ECG electrode this film transducer can be directly
attached to the chest to detect vibrations from heart.
Applications of bio impedance measurement include evaluation
of cardiac output, stroke volume as well as cardiac function. In
earlier days, for clinical purpose, we made use of tetra polar
band electrode system. This method could not be used for
continuous monitoring purpose. Thus we go for another method
called spot –electrode array. The impedance changes measured
with this electrode array showed a good correlation with those
using 3D finite element methods (FEM).
Electro physiological signals such as ECG, EEG and
EMG are monitored by attaching electrodes to the skin through
gel which may cause skin reddening and irritation. Why not
monitor it with high stability, high signal to noise ratio and
without any skin irritation using capacitive type electrodes,
flexible dry surface electrode or carbon nano tube array based
dry electrode? All these dry electrodes are under development.
Monitoring of health at home is very important.
Researches in the field of biomedical instrumentation have
lead to the development of a system called fully automated
network system for long term health care monitoring. This
system provides continuous monitoring of a bedridden patient
without needles or sensor attachments, let the patient be in
bath tub or bed!
The system is really interesting. The author discusses
threadbare the proposal with attractive figures and illustrations.
Jasna K.A
With the increased use of computers as vehicles of information
technology, it has become necessary to restrict access to
sensitive data. Biometric security and authentication is the
most preferred one for this; traditional methods involving
passwords and PIN numbers are not so reliable. Biometric
methods require the person to be identified to be physically
present at the point-of-identification but eliminate the need
to remember a password or carry a token. By replacing PINs,
biometric techniques can potentially prevent unauthorized
access to or fraudulent use of ATMs, cellular phones, smart
cards, desktop PCs, workstations, and computer networks.
An important issue in designing a practical system is to decide
how an individual is to be identified. Depending on the context,
a biometric system can be either a verification system or an
identification system. This article briefs about finger scan
method with emphasis on the scanners used in this
technology. Bio’ signifies life or living organisms; ‘metrics’
signifies measurement. Biometrics refers to the automatic
identification of a person based on measurement of his
physiological or behavioural characteristics such as finger,
retina, iris, voice and signature. A biometric system is
essentially a pattern recognition system, which makes a
personal identification by determining the authenticity of a
specific physiological, or behavioural characteristics
possessed by the user. Finger print recognition, a popular
biometric identification method, is available in present day
Finger prints are unique to each individual and two
fingerprints are not alike. Local ridge characteristics, occurring
at either the ridge bifurcation or a ridge ending form minutiae.
Finger scan is a biometrics product which provides some
unique characteristic or physical property of the fingerprint
of the individual. It helps to verify the identity of a person
unambiguously. The imaging process is based on digital
holography, using an electro-optical scanner about the size
of a thumb print. The scanner reads three-dimensional data
from the finger such as skin undulations, to create a unique
pattern that is composed into a template file and recorded in
the finger scan database. It stores characteristics of the finger,
and not the fingerprint itself. The fingerprint cannot in any
way be created from the template. A template can only be
compared with a newly presented live finger image and not
with other templates. One reason for this is that the data
capture process used to create a template is random. If two
templates were created one after another for the same finger,
each template would be different. This eliminates the
possibility of database matching, and enhances privacy of
Shalini Varma S7 AEI
Read This Paper
by : Senanayaka,
in : Robotics, Automation and Mechatronics,
IEEE conference, April 2008
It’s about
Human Motion Regeneration using Sensors
Human motion analysis is receiving increasing
attention from computer vision researchers. This interest is
motivated by a wide spectrum of applications, such as athletic
performance analysis, surveillance, man-machine interface,
content-based image storage and retrieval, and video
conferencing. Three major areas related to interpreting human
motion are motion analysis involving human body parts,
tracking of human motion using single or multiple cameras,
and recognizing human activities from image sequences.
Motion analysis of human body parts involves the low level
segmentation of the human body into segments connected
by joints, and regeneration of the 3D structure of the human
body using its 2D projections over a sequence of images.
Tracking human motion using a single camera or multiple
cameras focuses on higher-level processing, in which moving
humans are tracked without identifying specific parts of the
body structure. Understanding the human movements or
activities based on the moving human image naturally comes
after successfully matching the moving human image from
one frame to another in image sequences. We will look at
athletic performance analysis and regeneration technique in
this write up.
The process of analyzing the gait or motion of subject
is often referred to as motion analysis. Motion analysis, in
this context, is the detailed study of human motion, in a certain
task or within a certain area. Motion analysis methods are
mostly dependent on vision systems. Vision system methods
may not adjust and accommodate easily to major changes
made in the environment or lighting condition of the area.
These methods are time consuming and as such do not suit
sports performance analysis. Therefore, this approach is often
not practical in a sports monitoring/training situation. For such
situations, sensor based motion analysis is used. This is very
much useful to coaches as they obtain required results fast.
Thus sensor based motion analysis helps sports performance
enhancement and prevention of injury.
Accelerometers play an important role in short term supervised
monitoring and long term unsupervised monitoring.Tri-axial
accelerometers provide information on the acceleration in three
directions, namely the vertical (Z-axis), anterior and posterior
(Y-axis)directions and lateral direction(X-axis).
The accelerometers are placed on the test subject’s body at
points of interest, to measure the acceleration at those points.
These are then strapped down to the test subject’s body
using elastic body straps. The accelerometers have to be
securely strapped down to the test subject’s body to ensure
that the measurement obtained is purely due to the movement
of the test subject and not due to the movement of the
accelerometers within the body straps.
Placement of accelerometers on the test subject’s body
Sensors establish communication with a PC via a
USB base station, using very high frequency part of em
spectrum of the order of 900 MHz as its communication
medium. The USB base station attached to a computer enables
end user to issue various commands to the accelerometers.
Data got from accelerometers is then conditioned and
converted into appropriate kinematical information, which
then gets displayed in numerical or graphical form. An
important feature of the system is that initial processes, data
acquisition and data interpretation run on a single
programming platform.
In order to display the results acquired from the
accelerometer in terms of a regenerated motion, a stick figure
is designed to function with the accelerometer control
system. A stick figure is a simple type of drawing to depict
the general form of humans, for displaying results of motion
regeneration. All calculations for positions start from the tip
of the right foot. Most drawings of the human body take the
length of the head as the reference for calculating lengths of
different parts of the body. The calculation for the stick figure
involves simple trigonometric functions.
The initial point of reference is taken to be at node
14(the right foot) and moved upwards from that point to
node 20, node 92, node 86, node 91, node 15 and node 13.
Continued on next page.............
Read This Paper:
by :
Kimmo Koli and Kari A.I.Halonen, CMRR enhancement techniques for current-mode instrumentation
in : IEEE transactions on circuits and systems: fundamental theory and applications, vol. 47, no. 5, May 2000
Common mode rejection ratio (CMRR), is an
important performance parameter of any difference amplifier.
It is the ratio of the differential gain to the common-mode
gain, generally expressed in dB. It signifies the ability of an
opamp to reject common mode signal, the signal which
appears simultaneously at both its input terminals. The CMRR
is of great importance when it comes to noise rejection.
For applications involving high CMRR,
instrumentation amplifiers consisting of three opamps are
generally used. It has a major disadvantage that the value of
CMRR depends on the level of matching of some resistors.
Matching can be achieved to a limited extent only. Currentmode instrumentation amplifiers can be used to overcome
this problem. The method makes use of second generation
current conveyors (CCII), which convert differential input
voltage to equivalent current. This current is then converted
back to voltage by a current to voltage converter. This
configuration prevents the necessity of matching resistors
for high common mode rejection. Current-mode
instrumentation amplifier provides high CMRR even at low
differential gains, and so can be used over a wide frequency
range (note that, the gain-bandwidth product is a constant).
But still, this configuration too, is not perfect. This is due to
the transistor level mismatch in the CCII. The performance of
the current-mode instrumentation amplifier can be improved
by some modifications. This is described in the IEEE paper,
CMRR enhancement techniques for current-mode
instrumentation amplifiers, by Kimmo Koli and Kari
A.I.Halonen. (IEEE transactions on circuits and systems-:
fundamental theory and applications, vol. 47, no. 5, May
The contents of this paper include a small
introduction on the classical voltage-mode instrumentation
amplifier and its improved version working on current-mode,
its common-mode rejection and three techniques to improve
the CMRR. The methods mentioned here are, common-mode
bootstrapping, output current subtraction and use of
composite conveyors. The article also discusses the effect
of forward transconductance on some of the CCII based
The first method of CMRR enhancement, commonmode bootstrapping, exploits the relation between
common-mode rejection and power supply rejection. In this
method the CCII supply voltage is forced to follow the
common-mode voltage. This method has a limitation that, it
cannot be used for low voltage applications. In the second
method, the output current of one CCII is subtracted from
the other. The current subtraction can be done either using
opamps or by inverting the current using CCII. In the third
method, the performance of the CCII is improved by
constructing a composite current conveyor using two or more
The IEEE paper also presents experimental and
mathematical proofs for the suggested methods.
Kiran Stanly S7 AEI
The men who try to do something
and fail are infinitely better than
those who try to do nothing and
-Lloyd Jones
... Continuation from page - 9
This covers the calculation for the lower extremity of the
human body. The next stage would be to propagate the
calculation upward, using the node located near the hip
(node86).With reference to the readings got from the node at
the hip, the positions of the two arms are estimated using
nodes 90 and 87 for the right arm, and nodes 89 and 88 for the
left arm. The motion is regenerated and plotted in LabVIEW
programming platform using graphical output option.
The motion of each joint on the stick figure is got from the
acceleration-time profile. The acceleration-time profile is
converted first to velocity-time profile. The displacementtime profile is also got by numerical integration. Number of
sensors is minimized, and easy-to-wear sensors are used to
minimize the set up time. The complete motion data of this
system gets downloaded to a desktop PC via wireless USB
base station. The proposed system demonstrates the use of
accelerometers for motion analysis.
Mary Hexy
Over the last few years, we have witnessed a great expansion
of remote control devices in our day-to-day life. Five years
ago, infrared (IR) remotes for the television were the only
such devices in our homes. And now? We run out of fingers
to count the devices and appliances in our house which can
be controlled remotely.
Operation of all these remotely controlled devices, can be
made much smoother, easier and safe by putting them under
a single standardized control interface that can interconnect
them into a network, specifically a home-area network (HAN).
One of the most promising HAN protocols is ZigBee, a
software layer based on the IEEE 802.15.4 standard. This
article is an attempt to introduce ZigBee and its applications
to you .
What is ZigBee
It is an emerging standardised protocol for Ultra Low Power
Wireless Personal Area Networks (WPANs). Based on the
IEEE 802.15.4 standard, the term ZigBee is used to describe a
standardised wireless protocol for personal area networking,
or ‘WPAN’. The protocol is the work and property of the
ZigBee Alliance, a consortium of more than 70 companies
who have joined together to create and promote the new
ZigBee is different from other wireless standards in that it has
been designed to serve a diverse market of applications that
require low cost, low power wireless connectivity with more
sophistication than was previously available at the target
price. The standard focuses on low data rate, low duty cycle
connectivity, a market segment not serviced well by existing
standards. The reason for promoting a new protocol as a
standard is to afford interoperability among devices manufactured by different companies.
ZigBee alliance promoters include Honeywell, Phillips,
There are many wireless options available to
designers. Let’s compare ZigBee with some of the more
popular standards which share the unlicensed 2.4 GHz band.
The parameters listed in the chart include the governing MAC
standard, maximum over the air data rate, typical transmit and
standby currents, memory requirements for a typical device,
target applications and networking options. Bluetooth is a
popular standard applied to wire replacement applications. It
too is based on an IEEE PAN standard, 802.15.1. Bluetooth
operates with a 1 Mbps data rate. Note that Bluetooth and
ZigBee have similar transmit currents, but ZigBee has a
significantly lower standby current. This is because devices
in Bluetooth networks must frequently report into the network
to maintain synchronization, so they cannot easily drop into
a ‘sleep’ mode. Wi-Fi is a wireless LAN standard, so it requires
almost continuous activity by devices in the network. The
advantage of this standard is the tremendous amount of data
that can be moved from point to multi-point. Note the transmit
and standby currents. Wi-Fi hardware is designed to operate
off a significant power source. Of the three wireless standards,
only ZigBee offers the flexibility of mesh networking. Also
note the reduced memory requirements of ZigBee. ZigBee
applications are typically simple. The power is in the
networking, and ZigBee end devices can ‘sleep’ while still
maintaining network association
The advantages of Zigbee include unrestricted geographic
use, RF penetration through walls and ceilings, automatic or
semi-automatic installation, ability to add or remove devices,
and lower cost.
Jino M Pattery
Satellite telephones
There are confirmed reports that terrorists involved in
Mumbai blast used sat phones for communication.
Most of us are not familiar with satellite telephones. It
comes to daily use for those who work in ship, military,
disaster management, etc.
Most mobile telephone networks operate close to
capacity during normal times, and during emergency
situations due to large call volumes, the telephone systems
get overloaded. Satellite telephones are of use when we need
congestion free, portable means of communication.
A satellite phone, or sat phone, uses a network different
from that of normal mobile phones. These do not use
transmitting towers, but makes use of satellites directly. A
number of technical challenges are involved in devising a
satellite phone system. Path length between earth and
satellite introduces significant losses due to divergence. To
minimise this, most of the systems use low earth orbiting
satellites. But then, a number of satellites are to be used;
each satellite will be in view only for a certain amount of time.
It is therefore necessary even for a stationary phone to be
able to change over from one satellite to another. There are
service providers who make use of geostationary satellites
as well like Aces, Inmarsat , Thuraya and MSAT.
Phones used for satellite communication are often larger
in size. The antenna is often larger to ensure the required
level of power. Any mobile phone requires speedy
communication with the network to enable calls to be set up,
controlled and finished. The round trip delay from the mobile
to satellite and back to the earth is significantly long, and
affects speed of communication and protocol exchanges. As
a result, much of intelligence of the system has to be placed
within the satellite so that the required protocol exchanges
can take place fast.
A satellite phone doesn’t rely on local telephone
infrastructure to function. Because of this, they are used
widely in regions which are disaster prone. Satellite phones
are used widely in ships for communication. They are also
used widely for communication in remote area where there
are no mobile networks available.
There are many disadvantages; high cost of both the
handset and call, and bulky handset are some. Satellite phone
networks themselves are prone to congestion as satellites
cover a very large area with relatively less number of voice
channels. Sat phones are built for one particular network
and cannot be switched to other networks.
For dedicated and critical channels, satellite phones are very
effective. While popularizing more efficient and strategic
technologies, government and people must make sure that
they don’t reach wrong hands. There are confirmed reports
that terrorists involved in Mumbai blast used sat phones for
Nixon Varghese S3 AEI
Power rating of a standard T V set is 60W. Thus
current rating is 260 mA. But the fuse rating of
different manufacturers is in the order of 2 A. Why
First correct answer will win a small prize
Answer to the question in the previous issue
A googolplex is the number 10googol, which means
it’s a 1 followed by a googol of zeros (i.e. 10100
1 googolplex = 10googol
How big is a googolplex?
Carl Sagan estimated that writing a googolplex in numerals
(i.e., “10,000,000,000...”) would be physically impractical,
since doing so would require more space than the size of the
observable universe.
The time it would take
to write such a number
also renders the task
implausible. If a person
can write two digits
per second, it would
take around 1.1 × 1082
times the age of the
universe (about 1.37 ×
1010 years) to write a
Apptronics Review Crew: PRM, Meena, Jino, Sreejith K R, Anuj, Sreejith Ravi
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