05903
Design of Engineering Related Teaching
Aids for Middle and High School Students
May12,2005
Mentor: Dr. DeBartolo
Coordinator: Dr. Mozrall
Team Manager: L Jeffrey Kelly
Team Members:
Lisa Bonanno
Ryan Carr
Joel Lomnick
Kate Gleason College of Engineering
James E Gleason Building
Rochester Institute of Technology
Rochester, NY 14623-5604
Website: www.rit.edu/~ljk9697/05903
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TABLE OF CONTENTS
1
RECOGNIZE AND QUANTIFY NEED ...........................................................................................................5
1.1
1.2
1.3
1.4
1.5
1.6
1.7
2
PROJECT MISSION STATEMENT .......................................................................................................................5
PROJECT DESCRIPTION ...................................................................................................................................5
PROJECT SCOPE ..............................................................................................................................................6
PROJECT BENEFICIARIES .................................................................................................................................6
NEEDS ............................................................................................................................................................7
FINANCIAL PARAMETERS ................................................................................................................................7
FORMAL STATEMENT OF WORK .....................................................................................................................8
CONCEPT DEVELOPMENT ............................................................................................................................8
2.1
BRAINSTORMING ............................................................................................................................................8
2.2
SELECTION PROCESS: NARROW ......................................................................................................................9
2.3
CONCEPTUAL DESIGN DRAWINGS ...................................................................................................................9
2.4
SELECTION OF SEVEN DEFINITIVE CONCEPTS ............................................................................................... 10
2.5
DETAILED DESCRIPTION OF CHOSEN CONCEPTS ...........................................................................................10
2.5.1
Alternative Energy ............................................................................................................................... 10
2.5.2
Electrocardiograph..............................................................................................................................12
2.5.3
Factory Simulation ..............................................................................................................................13
2.5.4
Human Wire .........................................................................................................................................14
2.5.5
Mechanical Engineering Workstation .................................................................................................15
2.5.6
Solar Powered Car ..............................................................................................................................17
2.5.7
The Theremin .......................................................................................................................................17
3
FEASIBILITY ANALYSIS............................................................................................................................... 18
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
4
FEASIBILITY APPROACH ................................................................................................................................ 18
WEIGHTED CONCEPT EVALUATION ..............................................................................................................20
PUGH’S METHOD ..........................................................................................................................................21
WEIGHTED CONCEPT EVALUATION RESULTS ............................................................................................... 22
PUGH’S METHOD RESULTS ...........................................................................................................................23
FINAL RESULTS OF WEIGHTED CONCEPT EVALUATION .................................................................................24
FINAL RESULTS OF PUGH’S METHOD ............................................................................................................25
FEASIBILITY ANALYSIS CONCLUSION............................................................................................................26
OBJECTIVES & SPECIFICATIONS .............................................................................................................27
4.1
DESIGN OBJECTIVES .....................................................................................................................................27
4.1.1
Alternative Energy ............................................................................................................................... 27
4.1.2
Electrocardiograph..............................................................................................................................28
4.1.3
Factory Simulation ..............................................................................................................................28
4.1.4
Mechanical Workstation ......................................................................................................................29
4.1.5
The Theremin .......................................................................................................................................29
4.2
PERFORMANCE SPECIFICATIONS ...................................................................................................................29
4.2.1
Alternative Energy ............................................................................................................................... 29
4.2.2
Electrocardiograph..............................................................................................................................30
4.2.3
Factory Simulation ..............................................................................................................................31
4.2.4
Mechanical Workstation ......................................................................................................................33
4.2.5
The Theremin .......................................................................................................................................33
5
ANALYSIS & SYNTHESIS..............................................................................................................................34
5.1
ALTERNATIVE ENERGY .................................................................................................................................34
5.2
ELECTROCARDIOGRAPH ................................................................................................................................ 36
5.2.1
Recovering ECG Waveform from Patient ............................................................................................37
5.2.2
Preparing the ECG Waveform for Data Acquisition Stage .................................................................45
5.2.3
Analog to Digital Conversion & Data Acquisition ..............................................................................62
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5.3
FACTORY SIMULATION .................................................................................................................................63
5.4
MECHANICAL WORKSTATION .......................................................................................................................66
5.4.1
Vibration Absorption ...........................................................................................................................66
5.4.2
Vibration Dampening ..........................................................................................................................68
5.4.3
Motion of a Pendulum .........................................................................................................................69
5.5
THE THEREMIN .............................................................................................................................................70
5.5.1
Problem Statement ............................................................................................................................... 70
5.5.2
Summary of Known Information ..........................................................................................................71
5.5.3
Assumptions .........................................................................................................................................71
5.5.4
Schematics ...........................................................................................................................................72
5.5.5
Analysis ................................................................................................................................................73
6
PRELIMINARY DESIGN ................................................................................................................................ 73
6.1
6.2
6.3
6.4
6.5
7
ALTERNATIVE ENERGY .................................................................................................................................73
ELECTROCARDIOGRAPH ................................................................................................................................ 74
FACTORY SIMULATION .................................................................................................................................76
MECHANICAL WORKSTATION .......................................................................................................................77
THE THEREMIN .............................................................................................................................................79
FINAL DESIGN.................................................................................................................................................81
7.1
ELECTROCARDIOGRAPH ................................................................................................................................ 81
7.2
FACTORY SIMULATION .................................................................................................................................87
7.3
MECHANICAL WORKSTATION .......................................................................................................................92
7.4
THE THEREMIN .............................................................................................................................................94
[1] Webster, John G., Medical Instrumentation – Application and Design. USA, 1998. ...................................96
List of Tables
TABLE 1-1: LIST OF THE CUSTOMER NEEDS AND REQUIREMENTS ......................................................... 7
TABLE 2-1: LIST OF TWENTY THOUGHTS AND IDEAS ACHIEVED IN A BRAINSTORMING SESSION ............... 8
TABLE 2-2: LIST OF SEVEN DEFINITIVE CONCEPTS ....................................................................... 10
TABLE 3-1: ATTRIBUTES BY WHICH A FEASIBILITY ANALYSIS IS BASED ....................................... 19
TABLE 3-2: LIST OF SEVEN CONCEPTS FROM WHICH A FEASIBILITY ANALYSIS WAS CONDUCTED.......... 21
TABLE 5-1: MOOG THEREMIN COMPONENTS ................................................................................... 72
TABLE 6-1: BILL OF MATERIALS FOR THE ELECTROCARDIOGRAPH .................................................... 75
TABLE 6-2: BILL OF MATERIALS FOR THE VIBRATION ABSORBING BEAM ...................................... 77
TABLE 6-3: BILL OF MATERIALS FOR THE PENDULUM .................................................................... 78
List of Figures
FIGURE 1: GRAPHIC OF THE FIRST GENERATION WATER WHEEL......................................................... 35
FIGURE 2: PICTURE OF THE APPARATUS USED TO SIMULATE A WATER WHEEL .................................... 36
FIGURE 3: CARDIAC CONDUCTION SYSTEM .................................................................................. 38
FIGURE 4: PQRST WAVEFORM OF HEART .................................................................................. 39
FIGURE 5: SCHEMATIC OF PROTECTION CIRCUIT ............................................................................. 41
FIGURE 6: LIMITING OUTPUT OF PROTECTION CIRCUIT WITH A DC SWEEP FROM 0V TO 10V ............ 41
FIGURE 7: INTERNAL STRUCTURE OF INSTRUMENTATION AMPLIFIER INA114 ................................... 43
FIGURE 8: SCHEMATIC OF RIGHT-LEG DRIVEN SYSTEM ................................................................... 45
FIGURE 9: OVERVIEW SCHEMATIC OF ANALOG FILTER& ISOLATION CIRCUITRY................................ 46
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FIGURE 10: TEST PQRST WAVEFORM FOR SIMULATION .................................................................. 47
FIGURE 11: SCHEMATIC OF BANDPASS FILTER WITH GAIN OF 30 ...................................................... 49
FIGURE 12: FREQUENCY RESPONSE OF BANDPASS FILTER WITH GAIN OF 30 .................................... 50
FIGURE 13: SIGNAL AT OUTPUT OF BANDPASS FILTER ..................................................................... 51
FIGURE 14: UAF42 CONFIGURED AS A 60HZ NOTCH FILTER ........................................................... 53
FIGURE 15: FREQUENCY RESPONSE OF 60HZ NOTCH FILTER .......................................................... 53
FIGURE 16: OUTPUT WAVEFORM OF 60HZ NOTCH FILTER .............................................................. 57
FIGURE 17: INTERNAL CIRCUITRY OF ISOLATION AMPLIFIER ISO120 ............................................... 58
FIGURE 18: SCHEMATIC OF SECOND ORDER ACTIVE LOW PASS FILTER ............................................ 59
FIGURE 19: FREQUENCY RESPONSE OF SECOND ORDER ACTIVE LPF .............................................. 60
FIGURE 20: CIRCUITRY USED TO BIAS OUTPUT AROUND 2V ............................................................ 61
FIGURE 21: FINAL ANALOG OUTPUT OF ECG WAVEFORM ............................................................... 62
FIGURE 22: GRAPHIC OF THE SYSTEM OF BEAMS .............................................................................. 67
FIGURE 23: PICTURE OF THE PRELIMINARY PROTOTYPE VIBRATING BEAM SETUP ............................... 68
FIGURE 24: GRAPHIC OF THE PENDULUM EXHIBIT ........................................................................... 70
FIGURE 25: BLOCK DIAGRAM OF MOOG THEREMIN ......................................................................... 72
FIGURE 26: ACTUAL ANTENNA CIRCUIT AND THE EQUIVALENT ELECTRICAL CIRCUIT ....................... 73
FIGURE 27: BLOCK DIAGRAM OF ECG ............................................................................................ 74
FIGURE 28: FLOWCHART OF THE PROPOSED FACTORY SIMULATION: THE MANUFACTURING OF
HERSHEY’S CHOCOLATE ........................................................................................................... 76
FIGURE 29: PICTURE OF VIBRATION ABSORBING BEAM .................................................................... 77
FIGURE 30: PRELIMINARY PENDULUM DESIGN ............................................................................... 78
FIGURE 31: FINAL SCHEMATIC OF ECG IN ORCAD CAPTURE ..................................................... 82
FIGURE 32: SCHEMATIC OF BATTERY MONITOR CIRCUIT ............................................................ 83
FIGURE 33: AMPLIFIER STAGE WITH VARYING GAIN................................................................... 83
FIGURE 34: PCB DESIGN OF ECG IN CAD ................................................................................. 84
FIGURE 35: ILLUSTRATION OF LABVIEW INTERFACE FOR ECG MONITORING ........................... 86
FIGURE 36: DEPICTION OF FINAL ECG DESIGN ......................................................................... 87
FIGURE 37: ARENA SIMULATION SCREEN SHOT ........................................................................ 92
FIGURE 38: FINAL VIBRATING BEAM DESIGN ............................................................................. 93
FIGURE 39: FINAL PENDULUM DESIGN ....................................................................................... 94
FIGURE 40: FINAL PENDULUM DESIGN ....................................................................................... 95
FIGURE 41: COMPLETE SCHEMATIC OF ECG ................................................................................ 104
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1 Recognize and Quantify Need
1.1
Project Mission Statement
The mission of this project is to promote an interest in engineering of middle and high
school students with the help of several engineering related teaching aids.
1.2
Project Description
Design and build a Traveling Engineering Mobile Exhibit – Develop a series of
engineering and science related experiments and training aids aimed at middle school
students to raise their interest and awareness of different fields of engineering. It is
important that the team be composed of students from a variety of disciplines so that
the presentation to K-12 students emphasizes the multidisciplinary opportunities in
engineering. At least five different set-ups will be developed which will represent a
variety of engineering concepts and disciplines. The series of experiments will include,
at a minimum, one activity each related to bioengineering and energy/environment. The
students will work closely with a group of local science and math teachers as well as the
local Girl Scout Council. All engineering educational set-ups will be easily transportable
for in-class demonstrations at local schools. Detailed and clear instructional manuals
will be developed for each set-up. Recommended classroom activities, which may
include pre and post experiment activities, for a range of ages will be developed by the
capstone designers. The experiments will also be used in future RIT outreach efforts
including the Science Mall created as part of this project will be documented by the
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student team with faculty involvement and presented by team member(s) as a national
engineering educational conference in the summer of 2005.
1.3
Project Scope
The overall need for this project is to interest middle and high school students, women
in particular, in pursuing studies, and even careers in engineering and related
technology fields. The projects are designed to meet the interest level of the target
audience consisting of members from the local Genesee Valley Girl Scouts as well as
local high school and middle school students. The projects cover concepts found in
electrical engineering, mechanical engineering, industrial engineering, bioengineering,
and a variety of other engineering areas. All projects are designed for demonstration by
the senior design team or an instructor providing students with a fully interactive
experience. The purpose is for the students to gain awareness, and brief understanding
of opportunities in engineering and technology, while at the same time enjoying the
presentation.
1.4
Project Beneficiaries
This Senior Design project is part of a greater cause, which is to encourage and recruit
students to enroll at the Rochester Institute of Technology specifically the Kate Gleason
college of Engineering. The members of the Genesee Valley Girl Scouts would receive
an opportunity to earn badges as a result from th`eir participation in the experiments.
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Middle and High School students may reference their participation in the experiments to
aid in their pursuit of higher education, in a field of engineering or technology.
1.5
Needs
A list of customer requirements was developed to help guide the design team in the
design process. This list can be found in Table 1-1.
*
*
*
*
*
*
*
*
*
*
*
*
*
2-3 demos per package
At least one project in Bioengineering and Energy/Environment Engineering
Coherent instructions and explanations of concepts
Dimensions of carrying case: 3’ x 2’ x 1’ (max)
Estimated number of participants for each project
Less than 50lbs. total weight for all setups
Minimum of 5 project setups
Mobility: Carrying case(s) with handles and wheels
Must be hands on, interactive projects
Parts must be easily replaceable
Projects must be easily maintainable
Setup time less than 15 minutes per project
Total Project Budget is approximately $3,000
Table 1-1: List of the customer needs and requirements
1.6
Financial Parameters
Both the Mechanical Engineering Department and the Industrial and Systems
Engineering Department have donated $1000 towards this Senior Design Project. An
additional $1000 is anticipated from the Kate Gleason College of Engineering. Currently
a budget has been put into place sighting only the $2000 that the team is assured.
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1.7
Formal Statement of Work
2 Concept Development
2.1
Brainstorming
Project ideas were discussed in a group setting for the first time by brainstorming many
ideas ranging in topics and complexity. No idea was discouraged and all proposals
were written down. A list of concepts that may be displayed by the teaching aids was
brainstormed. Listing possible interesting concepts allowed new project ideas to form
resulting in a list of 20 proposals and concepts. Table 2-1 shows a list of the 20
concepts.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Electrocardiogram
Light Bulb generator
Solar Powered Car
House using Solar Power
Engineering Board Games
ARENA Factory Simulation
Design a Kite
Musical Instrument
Girl Scout Kit Design
Stress/Strain Demo
Natural Resources/Water Energy to Power a Radio
Mechanics of Body/Movement of Joints
Mechanical Engineering Demo Board - Pendulum
Bike - Energy Generation to power
Communications
Bioengineering
Power Generation
Stress/Strain/Mechanics
Process Optimization
Alternate Forms of Energy
Table 2-1: List of twenty thoughts and ideas achieved in a brainstorming session
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2.2
Selection Process: Narrow
The ideas thought of during brainstorming were discussed in greater detail. The needs
of our customers were re-evaluated. This included reviewing the curriculum from high
school physics and pre-engineering classes as well as reviewing the badge books from
Girl Scouts.
Projects were selected to meet the constraints defined by the needs
assessment. All projects chosen needed to be interesting and interactive for students
and teach an aspect of engineering. Ultimately the list found in Table 2-1 was narrowed
down by Eliminating those concepts that did not fit our needs or were deems infeasible.
2.3
Conceptual Design Drawings
Eight ideas were chosen from the list of brainstorming through the selection process
described in Section 2.2. Each group member prepared a description, with drawings of
these eight ideas. The drawings provided an illustration of what each concept involved,
giving the team as a whole a better idea of whether the project could be completed
successfully and meet all the requirements.
When completed, the drawings were
reviewed and discussed in a group environment where each team member provided
their input for each of the eight concepts, clarifying any question and/or concerns along
the way.
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2.4
Selection of Seven Definitive Concepts
A meeting was held with the Project Mentors and Coordinator. All prior project ideas
were discussed as well as new ideas. Seven definitive projects were chosen based on
the customers’ needs and the areas of interest of the group members. The seven
teaching aids included concepts within the following fields: electrical, biomedical,
mechanical, materials, and industrial engineering. In Table 2.2 is a list of the seven
definitive concepts chosen.
1
2
3
4
5
6
7
Electrocardiogram
Human Wire
Solar Powered Toy Car
Mechanical Engineering Workstation
ARENA Factory Simulation
Theremin – Musical Instrument
Alternative Forms of Energy
Table 2-2: List of seven definitive concepts
2.5
Detailed Description of Chosen Concepts
In order to complete a successful feasibility assessment of the concepts chosen, it was
necessary to define in detail each of the seven concepts.
2.5.1 Alternative Energy
Alternative Energy is a very important topic because it deals with conserving energy
and finding new ways to produce energy. The project itself will also show students ways
that the energy itself is actually converted. This can be done in a number of different
ways and the form of energy that we are going to begin with is water. Water is a widely
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used form of energy and relaying this idea and the actual mechanics behind is a very
important concept.
The demo will display a water wheel that is continuously turned by water that is recycled
with a water pump. This turning water wheel will be attached to a belt drive system
converting the potential energy of the water to mechanical energy. The belt drive
system will turn a DC Motor, converting a rotating mechanical energy into electrical
energy. The electricity will be used to light LED’s, power an AM/FM radio, or both.
Included will be an analogue voltmeter for students to read the amount of energy being
created. The experiment will convey the idea behind utilizing natural resources such as
water to create mechanical energy, which is then converted to electrical energy to
power the lights in your house.
The setup will include a small amount of water that will be continually recycled by a
pump. This pump will be setup to allow the water to be continually poured over a water
wheel to create rotation about the axis of the water wheel. The water wheel with either
be purchased as part of a kit or easily manufactured by the senior project team. The
demo will also require two pulleys and a belt to translate the mechanical energy to the
DC Generator. A couple of LED’s along with an AM/FM radio to show the energy being
created by the water wheel. An electrical switch will be required to turn the LED’s on.
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2.5.2 Electrocardiograph
A lecture will be given on the heart and how the electrical potentials excite the heart and
actually make it pulse or push blood throughout the body. The waveform of the heart
can be discussed and a detailed explanation of what each part of the waveform is
representing in respect to what is going on in the heart. A discussion of what ECG’s tell
doctors about the heart and how many diseases can be characterized by the ECG
signal with examples can be given. Next the ECG circuitry can be introduced and it’s
functioning explained.
The student can then connect two electrodes across their heart (by placing one on each
wrist or on each side of chest) and connect the third electrode to their right or left ankle.
The third electrode is a safety precaution for drainage currents to flow through the body
and not hurt the person. They must be instructed as to why they must use the abrasive
and conductive gels on the skin under the electrodes (to match impedance of skin to
that of the circuit as well as increase conductance).
Their own waveform can be
analyzed on the computer and they can dissect their own waveform to find the PQRST
complex of the theoretical waveform already discussed. A brief exercise can be done
to see if they can get their heart rate to go up (i.e. Performing 25 consecutive jumping
jacks) and then looking at their ECG reading.
The ECG will convey the following Engineering and Educational Concepts, Design of
Electrical Circuits, Measurement of Electrical Potentials Produced by Human Body,
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How the body creates electrical potentials, ECG readings and heart functionality,
Diseases diagnosed from ECG, Analysis of Waveform Data in LABVIEW.
2.5.3 Factory Simulation
Factory simulation is very common practice among those who are Industrial & Systems
Engineers. A program by the name of ARENA will be used to simulate a manufacturing
environment. In simulating a manufacturing environment, goals are set to minimize
floor space, production time, process time, and most importantly cost; all while
maximizing output. The program will contain a series of assembly lines that may be
modified to obtain a desired output. Students will witness the ways in which lines can be
optimized to obtain maximum output based on changing a number of different
variables.
A program will be constructed containing one assembly line showing the affects of
changing the given variables. The class will be divided into a couple of groups and
given the chance to try and optimize the assembly line by changing a defined amount of
variables. Each group will have an allowed number of changes that they can make to
the assembly line setups to achieve the largest output possible. A few examples of the
types of variables that can be changed are the number of assembly workers at a line,
the speed in which each part can be completed within a specified range, the length of
each assembly line, the distance between the lines and the storage areas, the use of
fork lifts or conveyors, and the speed of the assembly lines. The results of the changes
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made by the students will then be discussed to effectively relate the changes to realworld issues and concepts. The goal for students is to effectively maximize production
output by carefully changing the production line and it’s inherent variables.
The demo will be very simple due to the fact that it only requires the use of the Arena
software program. In order to run the program an up to date computer is required. The
main Engineering concept that is being conveyed in this teaching aid is the amount of
complexity involved with designing an assembly line and even the rest of a
manufacturing facility.
2.5.4 Human Wire
This tabletop exhibit demonstrates the phenomenon that is the ‘Human Wire’. Atoms
hold on to their outermost electrons with varying strengths. When metals with differing
strengths come in contact with a conductive medium, the metal with less hold on its
electrons looses charge to the metal with the greater hold on its electrons. Depending
on the metals used, varying voltages is created. The sweat from your hands when in
contact with the metal plates creates and electrochemical reaction that causes a small
current. This small current flows from one plate to the other and then through you and is
measured on an analog meter. The higher the needle moves the stronger the current. If
you place your hands both on the same metal plates, no voltage potential is created. By
changing the type of metal with your left and right hands you can achieve both a
positive and negative potential (i.e. copper with the left hand and aluminum with the
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right, or aluminum with the left hand and copper with the right). This demonstration was
designed for presentation in conjunction to the ECG.
2.5.5 Mechanical Engineering Workstation
Beginning with the pendulum, a lecture will be given with examples of a pendulum and
how it is used in everyday items such as a clock. Further more, information provided will
consist of a discussion concerning the characteristics of a pendulum and some
explanation of its motion. The teaching aid provided will entail an 18” long pendulum
pivoting on two precision roller bearings. The pendulum will be mounted to an anodized
aluminum display unit. The pendulum will have no weight added to it aside from its
inherent weight. Included with the demonstration will be a set of four or five different
weights (ex. 50g, 100g, 150g, 200g, and 250g). The pendulum will be equipped to
accept these weights at different locations along its length. Also the weights may be
added to each other at one or more locations. By changing the amount of weight and
location, the motion of the pendulum will be affected or it may not (the students will
make these observations). The students will be given an opportunity to predict how a
specific ‘weight configuration’ may affect the pendulums motion.
Following a discussion of pendulums, students will learn about the characteristics of a
vibrating beam vibrating at it’s resonate frequency. A lecture will be given with some
depth about resonate frequencies of different materials and how it plays a very
important part in the engineering of some small and some very large structures. A prime
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example of resonate frequency gone wrong can be shown in the Power Point
Presentation of the Collapse of the Tacoma Narrows Bridge.
After seeing how the resonate frequency of an object can cause such damage, the
students will get to turn on an electric motor attached to the very end of the beam. On it
will be an off center weight causing the beam to vibrate radically. Once everyone
agrees that the beam is vibrating out of control, the addition of a smaller beam on the
end of the larger beam, will demonstrate possible absorption affects. This smaller beam
will have the same resonate frequency as the larger one. The addition of the smaller
beam causes the larger beam to appear still while the smaller beam vibrates, absorbing
the vibrations. This is one of many methods of controlling the vibrations due to a
material or objects resonate frequency.
The second demo does not vibrate with a motor; it is simply an example of how to
dampen vibrations in a particular object. This demo involves the use of combining a
dampening material with the original beam material, yielding a composite material. A
brief explanation of composite materials will be given and how they allow for specific
characteristics of an object to be obtained by combining two or more chemically
different materials.
The Mechanical workstation will convey the following engineering concepts: motion of a
pendulum, how to dampen vibrations, and some basics on composite materials.
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2.5.6 Solar Powered Car
Two solar powered cars will be made with intentions of their weight and wheel diameter
to be variable. Both cars solar cells will be charged for the same length of time. A
switch will be turned on and one car at a time will race down one of the three terrains.
The speed of the car will be calculated by dividing the distance that it raced by the time
kept by students. The second car will do the same and their speeds can be compared.
This will be repeated for all three terrains. A discussion after each race can be given to
explain why the characteristics of that car may have affected it to win the race. A
discussion of materials used in building cars today can be given and why certain things
such as wheel diameter have an impact on performance. A simple circuit using a solar
cell, resistor, and voltmeter can be displayed and the solar radiation (watts/cm 2) at that
moment can be calculated.
Engineering and Educational Concepts include; Solar Power, Photovoltaic Engineering,
characteristics of various materials, and Mechanical Engineering (optimization of
vehicle design).
2.5.7 The Theremin
The Theremin is unique in that it is played like a musical instrument without being
touched. Two antennas protrude from the Theremin; one controlling pitch, and the other
controlling volume. The students will be able to experiment with the Theremin by
moving their hands over the vertical and horizontal antennas. The senior design team
will construct the Theremin from a kit.
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Girl Scout Requirements (Junior Badge book: Making Music)

(2) A New Sound – Research the Theremin instrumentation (how it’s
played, what it sounds like, what engineering category does it fall under,
what scientific properties make it work?)

(4) Compose Yourself – Compose a simple melody using the Theremin

(5) Musical Roots – What was the composer like? What pieces were
composed and when were they composed? Why was it written? Any
videos or articles on original Theremin invention? What makes the
Theremin unique?
The Theremin provides the following Engineering and Educational Concepts:
Psychoacoustics, Combining Electronics & Music, Design of Electrical Circuits, and
manipulating vibrations to create sound.
3 Feasibility Analysis
3.1
Feasibility Approach
The purpose of our feasibility assessment in this portion of our project was to compare
and contrast all of our concepts and attributes. The main goal of our assessment was to
eliminate all but five of our concepts to allow us to pursue the design of these five
chosen projects. This feasibility approach provided our group with a quantitative form of
analysis in order to determine which concepts were the most practical.
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The first step in our feasibility assessment was to compare the attributes determined
from our needs assessment, also found in Table 3-1, against each other to determine
which was the most important. A chart of the results can be found in Appendix A. Each
attribute’s level of importance was evaluated and compared to one another. A point was
assigned to an attribute if it was deemed more important than the one it was compared
to. If two attributes were considered equally important, each was awarded half a point
because no clear distinction could be made between the two. Points were represented
with arrows on the chart in Appendix A. After each attribute was compared against the
others, a total score was tallied by adding the number of points each attribute had
attained. This total for each attribute was then divided by the total number of points
assigned to all of the attributes. By doing this, we were able to assign a weighted
average to each of our attributes and acquire each of their relative importance. This
was a key step in the feasibility process by determining which elements of the overall
scope of the project are crucial to its success.
►
►
►
►
►
►
►
►
►
►
►
Mobility
Lightweight
Dimension of Project
Cost
Easy Instructions for Teachers
Set-up Time
Clear engineering concept conveyed
Interactive
Attention grabber
Maintainability / Easily Replenished
Engages a large number of students at one time
Table 3-1: Attributes by which a Feasibility Analysis is based
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3.2
Weighted Concept Evaluation
The next step in this process was to plot each of our concepts against our weighted
attributes. The first action our group took in beginning the assessment was picking one
of the conceptual projects as a reference point. This would allow us to compare the
remaining concepts to it, in determination of the most feasible. The concept chosen as
the reference point was the Electrocardiograph. Reasons for choosing the ECG include
its guaranteed student interaction, the connection with bioengineering, and most
importantly everyone on the team, including our advisor and coordinator, was most
excited about the ECG. A list of the seven concepts of which the feasibility analysis
was conducted can be found in Table 3-2. The concept chosen as the reference point
was assigned a score of 3 allowing it to be compared at the end of this analysis with the
rest of the concepts. Then, a score ranging from 1 to 5 was assigned to quantify how
well each attribute was satisfied by a particular concept. A score of 1 suggested that the
project was much worse than the reference concept. A score of 2 recommended that
the concept was a little worse than the reference concept. A score of 3 meant that the
concept was the same or comparable to the reference concept. A score of 4 said that
the particular concept was better than the reference concept. Finally, a score of 5
meant that a concept was much better than the reference concept. The third step of the
feasibility analysis was to take into account the weighted averages of the attributes
calculated in the first step of this assessment. This was done by multiplying the
weighted average for each attribute by the score of one to five assigned to each
attribute of each concept. The next step was then to add up all the products attained
across all the attributes for each concept. At this point, each concept had a sum and
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was compared to the reference concept. As stated previously in this section, the
reference concept was assigned a score of 3 so any concepts sum that was greater
than 3 meant that it performed better than the reference concept. The sums of each of
the concepts were then analyzed and the four concepts with the largest sums were
deemed the most feasible projects.
1
2
3
4
5
6
7
Alternative Energy
Electrocardiogram
ARENA Factory Simulation
Human Wire
Mechanical Engineering Workstation
Solar Powered Car
The Theremin
Table 3-2: List of seven concepts from which a Feasibility Analysis was conducted
By completing the final step of a Weighted Concept Evaluation, we had performed a
very rigorous feasibility assessment. Overall, the process was pivotal in the selection of
the five most feasible projects.
3.3
Pugh’s Method
This form of analysis provides a quick and brief feasibility assessment. Pugh’s Method
is used to give you a general idea of the performance of each of your concepts. Reason
this analysis cannot be used alone for a feasibility analysis is because it does not take
into account the relative importance of the projects attributes. This method is helpful
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however in providing a quick assessment of how your concepts, projects in this case,
match up against one another.
The first step a Pugh’s Method analysis is choosing a baseline concept As stated in the
Weighted Concept Evaluation, the baseline project that was chosen was the
Electrocardiograph and it was also used in this method. Once the baseline concept has
been established, the next step is to rate each concept by how well it satisfies each
attribute. In this analysis, the original eleven attributes were used to rate each concept.
The way in which each concept was rated was with either a +, 0, or –. The rating was
determined by how well the project performed against the ECG for that particular
attribute. If the project was considered to be better than the ECG for that certain
attribute, it was given a +. If the project was thought to be about the same as the ECG
for an attribute, it was assigned a 0. Finally, if a project was thought to be worse than
the ECG for a particular attribute, it was allocated a ‘–’.
The final step in this analysis was to add up all the +’s, 0’s, and –‘s for each concept.
This overall score was then used to analyze a projects overall performance against the
baseline project, which was the ECG.
3.4
Weighted Concept Evaluation Results
The final results we attained from this analysis were quite different than we had
expected. The top four scoring projects in this analysis were the Human Wire, The
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Theremin, the Mechanical engineering workstation, and the Solar Powered Car. The
fifth project was the ECG project since it was chosen as the reference point. The first
problem we noticed was that after the ECG, the next project that we had determined
was a finalist was the Factory Simulation, but in this analysis it finished dead last. The
team discussed the possible causes of the low scores that the project received and we
came up with a few possibilities. We believed that we had left out a couple important
attributes in our overall analysis that would have made the Factory Simulation score
much higher in the Weighted Concept Evaluation. Two attributes that we determined
should have been in the analysis were “The confidence in the project actually working”
and the second was “The amount of work/materials involved in constructing a project”.
We decided to add these two attributes to our original list of eleven and perform the
analysis over again to see if the results would change.
3.5
Pugh’s Method Results
The final results from the Pugh’s Method gave us a little insight into how well the
projects matched up against each other. The four projects that received the most +’s
were The Theremin, the Factory Simulation, the Solar Powered Car, and the Human
Wire. The fifth project that would have been deemed a finalist in this case is the
baseline project (ECG). The problem with only using these results for a feasibility
analysis was some of the top rated projects also had a large number of –‘s. The Solar
Powered Car and the Human Wire projects both also received the highest number of –
‘s out of the projects. This left us with mixed results at best and we determined that we
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could not rely fully on this analysis for our final decision. This is the reason the Pugh’s
Method needs to be used with another feasibility assessment to attain a more logical
and mathematical result.
Another aspect of this analysis that we needed to consider was the possibility affect of
the two new attributes that we developed. We decided to add the two new attributes to
the list and retry Pugh’s Method to see if we could attain more definitive results.
3.6
Final results of Weighted Concept Evaluation
The Weighted Concept Evaluation was performed for a second time with the addition of
the two new attributes. The incorporating of the two new attributes had an immediate
impact in the results Weighting of Relative Importance’s of the attributes. When the
group re-evaluated the relative importance of the now thirteen attributes, the two added
attributes were seen as being very important. The “confidence in the project working”
attribute received a relatively high level of importance because we realized as a group
that if the project didn’t actually even work we would have wasted a considerable
amount of valuable time.
The next step in the re-evaluation process was to incorporate the relative weights of
each of the thirteen attributes into the Weighted Concept Evaluation. The addition of
the two new attributes also had an impact on the results of this final part of this
analysis. The top four scoring projects were the Factory Simulation, The Theremin,
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Alternative Energy, and the Mechanical engineering workstation. The fifth finalist was
again the ECG project because it was the reference point and the project that was
originally agreed on as a finalist.
The results from this analysis gave us very valuable results in the selection of five
projects. We were able to perform a quantitative analysis that incorporated both the
importance of the projects attributes and the projects themselves. The final results from
this analysis were used to make the final selection of the five projects that we as a
group will be designing.
3.7
Final Results of Pugh’s Method
The final results that we attained from the modified Pugh’s Method were slightly more
definitive. The addition of the attributes “confidence in project working” and “amount of
work/materials involved in constructing” project caused enough of an affect for us to
make a more clear assessment of the results of the analysis. The final results conveyed
that the four projects with the most +’s were the Factory Simulation, The Theremin, the
Mechanical Engineering workstation, and the Solar Powered Car. The fifth and final
project was again the baseline project that was determined at the beginning of the
analysis (ECG). The only problem with the results we attained was the Solar Powered
Car project also had the largest number of –‘s of the projects. This lead us to believe
that perhaps this should not be one of the final five projects chosen because it did in
fact have more –‘s than +’s. We went back and analyzed the results and noticed that
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the Alternative Energy project had the largest number of 0’s out of the projects, which
meant that it had scored very comparable to the ECG project. This project also had a
fairly low number of –‘s, which meant that it performed worse than the ECG for only a
couple of attributes. Both of these reasons lead us to select the Alternative Energy
project as the last of the five projects that we would later design.
Although this analysis did not give us a definite answer as to what the five projects
should be, it gave us a valuable account of how well each project scored against what
we considered the best project (ECG). It also coincided closely with our Weighted
Concept Evaluation and made us much more confident in the selection of the top five
projects.
3.8
Feasibility Analysis Conclusion
Overall, the feasibility assessment of our attributes and projects through the Weighted
Concept Evaluation and Pugh’s Method proved essential in our selection of the final
five projects. The overlapping of the two feasibility methods gave us a very in-depth
analysis of our projects through weighing of the importance of our attributes. The
reason that this was so important in the selection of our five projects was our attributes
were established as guidelines to ensure the success of our overall project. Since each
attribute was analyzed independently against our projects, we believe we succeeded in
choosing the best five projects. In conclusion, the five projects that we have decided to
design and eventually develop as a result of these assessments are listed below.
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1
2
3
4
5
Alternative Energy
Electrocardiogram
ARENA Factory Simulation
Mechanical Engineering Workstation
The Theremin
Table 3-3: List of the final five concepts chosen for design
4
Objectives & Specifications
4.1
Design Objectives
The Senior Design Team has incorporated a few objectives into the design of all the
five projects. While each project had objectives that were shared with the entire team
each project also had objectives of their own. Those objectives that the team has set
forth for all of the five projects have been derived from the requirements and needs of
the customer. Below is a list of those objectives:

Created interactive and fun learning devices.

Convey a broad range of engineering related topics and material with emphasis
on Bioengineering and Energy and the Environment

Include competent and cohesive instruction manuals

All projects are need to be mobile, self sustaining, and relatively light.

Project will be grouped together in groups of two and three as a traveling exhibit.
4.1.1 Alternative Energy

Illustrate different forms of energy.
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
Show how natural forms of energy can be converted into a form of energy used
in everyday life, electricity.

Raise student awareness about the engineering possibilities in utilizing the
environment to create usable energy.

Utilizing natural forms of energy like sun and water is far cleaner than the
conventional forms of energy such as nuclear and combustion.
4.1.2 Electrocardiograph

Demonstrate an application of electrical engineering in the biomedical field.

Build a device capable of illustrating a human ECG wave form on a computer.

Ensure that patient, circuit, and computer are all safe from spikes in voltage.

Produce clean signal with reduction in noise.

Teaching aid must be transportable.
4.1.3 Factory Simulation

Provide students with an example of a typical application of Industrial
Engineering.

Realistic model of Hershey Chocolate production process.

Clear set of instructions for teacher to follow in order to change variables and
offer explanations as to the effects of changing each variable.

Advanced automation portraying the actual chocolate production process
including the workers moving materials and resources, machines working on the
products, and the chocolate moving along the production line.
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
A default simulation will be included containing all the data necessary to run the
simulation. The teacher will only need to change a few different variables along
the production line (workers, machines, and mean time between failures).

Produce clear, readable output that students and teachers will be able to review
to see the affects of changing certain variables along the production line.
4.1.4 Mechanical Workstation

Provide students with a taste of Mechanical Engineering.

Demonstrate a vibrating beam experiment.

Demonstrate the motion of a simple pendulum.
4.1.5 The Theremin

Several electrical concepts that can be presented based on the design of the
Theremin, but the focus is on the effects of varying capacitance to manipulate
frequency, which translates to sound.

The Moog Etherwave Theremin will be built using a purchased kit.

There will be a simulation of the Moog Etherwave Theremin antenna equivalent
circuitry using PSpice, which will measure frequency of the volume oscillator and
the frequency of the pitch oscillator as hand capacitance varies.
4.2
Performance Specifications
4.2.1 Alternative Energy
The following are performance specifications of the Alternative Energy:
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1. Demonstrate the conversion of energy in the form of falling water to mechanical
energy.
2. Convert the mechanical energy into electrical energy
3. Use Light Emitting Diodes and/or an AM/FM radio to portray the electrical energy
being created.
4. Use a solar cell to create electricity.
5. The solar circuit will be connected in parallel with the water circuit with the ability
to use the energy from one or the other or both to power the LED’s and AM/FM
Radio.
4.2.2 Electrocardiograph
The following are performance specifications of the Electrocardiograph:
1.) SAFETY:
a. Protection Circuit: for displacement of spikes in voltage to ground
b. Right-Leg Drive: keeps patient ungrounded
c. Isolation Circuit: keeps circuit and computer at separate grounds
2.) INPUT POWER:
a. 9v batteries
3.) NOISE REDUCTION:
a. Use of shielded cables
b. 60Hz Notch Filter
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c. DC and frequencies lower than 0.05Hz filtered out of output signal
d. Frequencies higher than 100Hz filtered out of output signal
4.) TRANSPORTABILITY:
a. Output signal displayable on labtop computers
b. Battery Powered
c. PCB is relatively small and light-weight
5.) DATA ACQUISTION:
a. Output signal displayable in time-series format
b. Image Quality Resolution of 5mV
c. Image Quality Accuracy better than 5%
4.2.3 Factory Simulation
1. The following are performance specifications of the Factory Simulation:
2. Arena software, version 7.01 will be used for the factory simulation
3. Microsoft Windows 98 is needed to run program
4. Internet Explorer 4.01 with Service Pack 2 or later
5. Hard drive with 85 – 255 MB free disk space required
6. 128 MB RAM
7. Pentium III processor
8. 700 Mhz processing speed
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9. A 14 inch monitor is required to properly display animation
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4.2.4 Mechanical Workstation
The following are performance specifications of the Mechanical Workstation:
1. The vibrating beam will be excited with an unbalanced weight attached to a 12
volt DC motor.
2. The beams vibration will be controlled in turn by controlling the speed of the
motor, which will be accomplished with a 12 volt DC Speed controller.
3. The addition of a secondary beam will demonstrate techniques by which
vibrations can be absorbed.
4. The pendulum will oscillate on roller bearings to reduce friction.
5. Included with the pendulum will be a set of four or five different weights (50g,
100g, 150g, 200g, 250g) that will be able to be placed at different locations on
the pendulum.
4.2.5 The Theremin
The following are performance features of the Moog Etherwave Theremin [5]:
1. POWER: Power rocker switch - switches on and off the AC power to Theremin.
2. AUDIO OUT: Standard 1/4" phone jack, which delivers line level output to your
amplifier.
3. PITCH: Pitch rotary control, for adjusting the response of the pitch antenna.
4. VOLUME: Volume rotary control, for adjusting the response of the volume
antenna.
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5. WAVEFORM: Waveform rotary control, for adjusting the waveform of the audio
output.
6. BRIGHTNESS: Brightness rotary control, for adjusting the brightness of the
audio output.
7. POWER INPUT: Receptacle for the special AC adapter that comes with the
Etherwave.
8. ANTENNA CONNECTORS - Threaded connectors which allow the antennas to
be removed for travel
5 Analysis & Synthesis
Each of the five projects required analysis in its own form. Analysis will include
everything from cohesive explanations, calculations, and diagrams to drawings and
simulations.
5.1
Alternative Energy
The alternative energy demonstration will require a crude analysis of the water wheel
and some thought about a DC Motor to be used as a generator. Analysis of such a
water wheel will involve lengthy calculations yielding less than perfect results. Research
has suggested that water wheels or Impulse Turbines are extremely inefficient for the
circumstance in which it will be used. Figure 1 is a graphic rendering of the first
generation water wheel that we will use to begin testing.
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Figure 1: Graphic of the first generation water wheel
We are not expecting to achieve higher than 20% efficiency from this water wheel.
Initially, there was concern that the water wheel would not be able to rotate a DC
Generator to create electricity. After deciding that the analysis will have to be primarily
experimental, motors were selected and purchased along with LED’s. Crude
experimental analysis resulted in confidence that the water wheel will indeed be
sufficient in turning a DC motor to generate electricity. To achieve such results a lever
arm was attached to a 12 volt DC stepper motor and a 16 oz cup was hung from the
end of the lever arm. Roughly 4 oz of water was then poured into the cup from an
approximate height of eight inches. With out any difficulty the rotation of the motor was
able to light an LED attached to its leads. A picture of the experiments set up can be
seen in Figure 2.
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Figure 2: Picture of the apparatus used to simulate a water wheel
The solar cell that will be used in parallel with the water circuit was chosen based on
the following parameters; output voltage, output current, size, and cost. For this
particular application a solar cell that is relatively small (no bigger than 5” x 5”) would be
beneficial. Output voltage is not required to be higher than 3 volts due to the fact that it
will be used to power a few LED’s and/or an AM/FM radio.
5.2
Electrocardiograph
The electrical currents generated in and transmitted through the heart spread through
the body. An electrocardiograph (ECG or EKG in Germany) is a composite of all of the
action potentials generated by nodal and contractile cardiac cells as a function of time.
The standard for diagnostic ECG has twelve recording electrodes positioned at various
sites on the body’s surface. In this design a less comprehensive but adequate system
is designed using three recording electrodes to recover the ECG signal intended for
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teaching purposes. This ECG is portable and powered by 9v batteries. The circuitry
consists of units trying to accomplish the following: (1) recovering the ECG waveform
from the patient, (2) preparing the analog signal for digital conversion, (3) converting the
analog signal to digital and displaying the digital signal on a computer. The design of
the circuitry used to accomplish these tasks is discussed in great detail in the following
sections of this paper.
This design is intended for use as a teaching aid.
ECG
standards and regulations were applied where applicable to meet safety requirements
for this design. Although no FDA approval is needed for this device as it is not intended
for sale. Refer to Appendix B[1] to view a list of standards for a diagnostic ECG. Take
into consideration when reading these standards that a diagnostic ECG is much more
complicated than this design with 12 leads as well as powered by much higher voltage
than two 9v batteries.
5.2.1 Recovering ECG Waveform from Patient
Within the human body electrical currents are created by a flow of ions through semipermeable membranes in the muscle and nerves. Electrical rhythm of the heart is set
by the sinoatrial (SA) node, also known as the heart’s pacemaker.
The electrical
impulse travels across a specific route through atrioventricular (AV) node and down into
the Purkinje fibers that line the walls of the ventricles.
The electrical signal is
propagated throughout the heart’s myocardial fibers to result in the heart pumping as a
single unit in a consistent set frequency. Refer to Figure #3 below.
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Right Atrium
Left Atrium
Left Ventricle
Right Ventricle
Figure 3: Cardiac Conduction System
The PQRST waveform depicted in Figure #4 represents a single heartbeat. There are
3 distinct waves within the heartbeat, each representing the behavior of the impulse at
different locations along its pathway through the heart. Refer to the anatomical
structure of the heart depicted in Figure #3 to observe the path of the electrical signal.
The P wave is associated with the spread of the impulse through the heart’s upper atria
(chambers). The QRS complex represents the contraction of the ventricles and the T
wave reflects the relaxation of the ventricles. This waveform is used to characterize
heart disease, arrythmias (irregular heart rhythms), Myocarditis (inflammation of the
heart muscle due to virus), and many other abnormalities. The importance of this
method of characterization is that the procedure is non-invasive to the patient and
therefore much cheaper and safer.
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Figure 4: PQRST Waveform of Heart
5.2.1.1 Electrode and Cable Design Theory
The electrodes work as transducers converting the ionic flow from the body through an
electrolytic medium into electron current.
commonly used.
Silver – Silver/Chloride electrodes are
At the electrode-electrolyte interface the ionic flow of ions,
corresponding with the ECG signal spreading, result in the metal ions solidifying to
maintain a chemical equilibrium. This results in a voltage drop across the electrodeelectrolyte interface. The cables that are used must either be well shielded or a twisted
pair to reduce noise. Due to the electromagnetism and geometry of twisted wires, they
produce noise signals of equal magnitudes but opposite polarity; therefore canceling
the noise signals.
Shielded cables isolate the signal from radio frequency and
electromagnetic interference. The effective length of the cables may also be reduced to
reduce noise.
5.2.1.2 Input noise Constraints
Human skin has a high impedance value. Abrasive gels can be used to remove any
dead skin or non-conductive substance that would impair the waveform. A conductive
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gel may also be used to promote the passing of the signal at the electrode-electrolyte
interface.
Any movement that causes muscle movement generates noise that
interferes with the signal. Measurements are best when taken on a relaxed and still
patient. Because the ECG signal is small (approximately 2mV) the amplifier circuit is
very susceptible to noise.
5.2.1.3 Input Protection Circuit
The input protection circuitry protects the circuit from any high spikes of input voltage.
When referring to an electrocardiograph, this may occur when monitoring a patient
during fibrillation. Fibrillation is the rapid, irregular, and unsynchronized contraction of
cardiac muscle fibers and is a common cause of heart attack. One NPN and one PNP
transistor is mirrored with both the collectors and emitters shorted together. The inputs
from the electrodes are sent into the collector pins of the NPN transistors Q5 and Q6.
This can be seen in Figure #5 where the input currents from the electrodes are depicted
on the left of the schematic. Any jumps in the input current on either one of the inputs
opens up the corresponding transistor (Q5 or Q6) and shorts to ground. Refer to Figure
#5 below to observe the design of the input protection circuit. The graph in Figure #6
illustrates the response of the input protection circuit to an increase in DC voltage from
0 to 10 volts in simulation in Orcad PSpice. Within Figure #6 it can be seen that the
protection circuit limits the voltage input into the remaining circuit. With even a large
input of 10 volts the input voltage was limited to under 700mV.
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Input of
Electrode 1
Output 1
Output 2
Input of
Electrode 2
Figure 5: Schematic of Protection Circuit
Figure 6: Limiting Output of Protection Circuit with a DC Sweep from 0v to 10v
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5.2.1.4 Instrumentation Amplifier
An instrumentation amplifier is a type of differential amplifier used for applications with
high-resistance sources.
A simple buffer amplifier is attached to each input of the
instrumentation amplifier internally to decrease the input resistance before attaching to
the differential amplifier.
A differential amplifier amplifies the difference in voltage
between its two inputs signals. The internal structure of the instrumentation amplifier
INA114 is illustrated below in Figure #7. The two inputs are passed through buffer
amplifiers A1 and A2 and then input into the differential amplifier A3. The ideal output
of a differential amplifier when the two inputs are identical values (common-mode) is
zero. Realistically no differential amplifier perfectly rejects the common-mode voltage.
The term common-mode rejection ratio (CMRR) is used to quantify this imperfection.
The CMRR of the INA114 is 115dB min.
A gain of 12.2 is obtained through this
instrumentation amplifier stage. At the output of the differential amplifier the (PQRST
wave) ECG signal is recovered. The remainder of the circuitry after this point is needed
for safety, to reduce noise in the signal, and convert the analog signal to digital for the
computer to recognize.
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Figure 7: Internal Structure of Instrumentation Amplifier INA114
5.2.1.5 Right-Leg Driven System
In all biomedical instrumentation applications the patient’s safety is of most importance.
One method of protecting the patient from the circuit is a right leg driven system. Refer
to Figure #8 below to view the schematic. Any displacement currents from the circuit
are fed through the right leg drive where they are inverted by the op-amp (U12B in
Figure #8) and passed through the patient’s body back into the circuit. This essentially
allows the patient to not be grounded and safe from shocks or electrocution. If large
spikes in voltage appear between the patient and ground (for any abnormal reason) the
op-amp would saturate and no longer be able to drive the right-leg drive; therefore
grounding the patient. These large voltages however would break down the transistors
inside of the op-amp and the remaining large current would flow to circuit’s ground.
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As well as protecting the patient the right-leg drive reduces the common-mode voltage
of the instrumentation amplifier. In Figure #8 the averaging resistors R27 and R28
external to the instrumentation amplifier (INA114) sense its CMRR. This voltage is
amplified and inverted by op-amp U12B in Figure #8 and fed back to the right leg drive
electrode of the right leg. The second op-amp U11B present in the right-leg drive
circuitry is a buffer amplifier with unity gain, which lowers the resistance of the input for
the following amplifier (U12B). A negative feedback loop is formed and reduces the
common-mode voltage.
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Protection Circuitry
Instrumentation Amp
Output
to filter
stages
Right-Leg Drive
Patient
Key:
Electrode
Cable
Figure 8: Schematic of Right-Leg Driven System
5.2.2 Preparing the ECG Waveform for Data Acquisition Stage
As discussed previously the output of the instrumentation amplifier (Refer to Figure #6)
gives the PQRST waveform. Although the waveform is obtained at this point, this signal
is noisy and at a very low amplitude range. The following stages of the circuitry that are
depicted in schematic form in Figure #7 will filter out noise and amplify the amplitude of
the signal so that it can be easily distinguished from any noise in the output to the
computer.
The analog circuitry is then isolated from the computer by an isolation
amplifier for safety precautions. Finally the signal is prepared for the Data Acquisition
Stage by biasing it around a reference voltage to swing within the specified “readable”
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range of the microcontroller unit. The following sections 5.2.2.1 – 5.2.2.5 will discuss
each part of the circuitry displayed in Figure in #9 in greater detail.
Bandpass Filter & Amplifier
60Hz Notch Filter
0.01u
Isolation Amplifier
Input ECG
waveform from
Instrumentation
Amplifier
Output ECG
waveform to
Digital
Converter
100Hz Low Pass Filter
Bias Output Around 2v
Figure 9: Overview Schematic of Analog Filter& Isolation Circuitry
5.2.2.1 Creating PQRST Waveform in PSpice
Within PSpice there is no way to abstract an ECG signal from a person. Therefore an
ECG waveform was drawn in Stimulus Editor of PSpice. This ECG waveform can be
viewed below in Figure #10. This ECG signal is assumed to be at the output of the
instrumentation amplifier. Therefore the signal is already amplified by a gain of 12.2.
This waveform was used as the input waveform in the following simulations.
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Figure 10: Test PQRST Waveform for Simulation
5.2.2.2 Bandpass Filter Amplification Stage
The ECG signal normally is considered to be in the range of 1mV-5mV within the
approximate frequency range of 0.05Hz to 100Hz.
A bandpass filter amplifies the
signals over a desired range and attenuates the higher and lower frequencies. Figure
#11 illustrates the schematic of the bandpass filter used to pass frequencies between
the range of 0.05Hz to 100Hz. This range was chosen to include the entire ECG signal
and block any noise in the higher and lower frequency ranges. A bandpass filter is
essential produced by a series combination of a lowpass filter and a highpass filter.
The high pass section of the bandpass filter is important in an ECG circuit by blocking
any DC voltage. The process of the patient breathing and their lungs expanding and
contracting with each breath causes a fluctuation in DC voltage in the ECG
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measurement causing noise in the signal. A lower corner frequency, f c,HPF, of 0.05Hz
was chosen for the filter. It is at this lower corner frequency that the filter begins to
amplify the signal. The low pass section of the bandpass filter gets rid of any noise that
has a higher frequency than the chosen high corner frequency, f c,LPF. A high corner
frequency, fc,LPF, of 100Hz was chosen. A The equations used to calculate the values
of the resistors and capacitors shown in Figure #11 to get the desired frequency range
and gain (Av) is shown in Equations #1 through Equation #3.
The calculations
performed in this design are displayed below the corresponding Equation. The value of
resistor, Rf was set equal to 150k before beginning the calculations[7].
Rf C f  
Cf  
Av  
1
2f c , LPF
1
= 0.01F {Determination of value of Cf using Equation #1}
2 (100 Hz )(150k)
Rf
Ri
Ri  
Ri Ci  
Equation 2: Gain of Bandpass Filter
Rf
Av

150k
 5k {Determination of value of Ri using Equation #2}
30
1
2f c, HPF
Ci  
Equation 1: Corner Frequency of Low Pass Filter
Equation 3: Corner Frequency of High Pass Filter
1
= 637F {Determination of value of Cf using Equation #3}
2 (0.05Hz )(5k)
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0.01u
Figure 11: Schematic of Bandpass Filter with Gain of 30
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Figure 12: Frequency Response of Bandpass Filter with Gain of 30
* Low Pass Corner Frequency = 100Hz
* High Pass Corner Frequency = 0.05Hz
The frequency response of the bandpass filter is shown in Figure #12. It can be seen
that the intended band of frequencies from 0.05Hz to 100Hz are amplified, while the
lower and higher frequencies are attenuated.
This filter has a gain of 30, which will amplify the signal over the desired frequency
range. At the output of the instrumentation amplifier, which has a gain of 12.2, the ECG
signal still has relatively small amplitude. A gain of 30 will step up the amplitude of the
signal so that it is readable above noise levels in the output waveform on the computer.
A consideration that must be taken is that the output waveform must be between 0 and
5 volts for the microcomputer to read it. This will later be discussed in more detail in the
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Biasing Output Waveform section. At this point in the circuit the voltage is swinging
both positive and negative. The amplification of this stage should not increase the
amplitude of the positive swing above 3 volts or the amplitude of the negative swing
above 2 volts. This is due to the fact that the output waveform will be biased around
positive 2 volts just before being sent to the Data Acquisition stage (micro-controller).
Otherwise the signal would not be recognized by the micro-controller, because it is out
of the needed range of 0-5 volts.
The output of the bandpass filter is shown in Figure #13 for the input PQRST waveform
depicted in Figure #10. It can be seen that there is a gain of 30 and that the waveform
is inverted due to the fact that the bandpass filter uses an inverting amplifier.
Figure 13: Signal at Output of Bandpass Filter
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5.2.2.3 60Hz Notch Filter
A notch filter is utilized to remove a certain frequency band from a signal. In most
electrical circuits the presence of 60Hz noise poses a problem. In the United States the
power attained from an outlet plug runs at a frequency of 60Hz. This also produces
noise in the ECG circuitry (which is not run off of a power outlet, but by battery power)
due to electromagnetic fields in the room. The 60Hz notch filter was implemented using
Burr-Brown’s Universal Active Filter UAF42 to rid the ECG of any 60Hz noise. This 2 nd
order active filter has low sensitivity to filter design parameters such as natural
frequency (fo) and Q to external component variations.
The auxiliary operational
amplifier sums the high-pass and low-pass outputs. At the desired notch frequency,
fNotch, these two outputs are equal in magnitude but out of phase by 180°. This causes
the outputs to cancel each other and give a zero output voltage at the desired f Notch. A
notch filter was designed using this IC with six external resistors. Figure #14 below
illustrates the schematic of UAF42 as a 60Hz notch filter. In Figure #15, an illustration
of the simulated frequency response of the UAF42 60Hz notch filter is given in PSpice.
The sharp dip in voltage observed at 60Hz shows that the filter is acting correctly and
blocking voltages at 60Hz.
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Figure 14: UAF42 configured as a 60Hz Notch Filter
Figure 15: Frequency Response of 60Hz Notch Filter
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The following equations and calculations were utilized to determine the values of the
external resistors (RF1, RF2, RQ) needed to adjust the filter parameters f o and Q to their
desired values.
Equations #4 - #7 describe how the value of RF1 and RF2 are
determined. For our 60Hz notch filter the value of f o is set equal to 60Hz in Equation
#4. The values of C1 and C2 are determined by Burr-Brown and are internal to the chip.
f Notch  f 0 
1
R f  C  2
C  C1  C2  1000 pF
Rf  Rf1  Rf 2
Equation 4: Determination of FNotch
Equation 5: Determination of Capacitance Values
Equation 6: Determination of Resistance Values
Combining Equations #4 through #6 together a value of RF is attained and showed
below in Equation #7.
Rf 
1
f 0  C  2
1
60 Hz  1000 pF  2
R f  2.65M
Rf 
Equation 7: Calculation of RF
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The filter Q can be determined by setting the R Q value as described in Equation #8.
The filter Q value is equal to the filter center frequency divided by its bandwidth. The
higher the value of Q, the steeper of a slope the frequency response will give at the
notch frequency. A high value of Q is desired for a filter. The UAF42 has a Q value
equal to 6.
25k
(Q  1)
25k
RQ 
(6  1)
R Q  5 k
RQ 
Equation 8: Calculation of RQ
The bandwidth (BW -3dB) of a filter is determined by the frequency at which the gain
decreases 3dB on the lower end of the notch frequency (f H) subtracted by the frequency
at which the gain is within 3dB of the maximum gain (f L) at the high end of the filtered
frequency. This is explained by Equation #9. The 3dB bandwidth of the filter can be
calculated using Equation #10.
BW 3dB  f h  f l
BW 3dB 
f Notch
Q
Equation 9: Definition of 3dB Bandwidth
Equation 10: Determination of Filter Band Width
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The pass-band gain of the notch filter is influenced by the filter Q value. The gain is
adjusted for unity by setting the summing circuit feedback and input resistor ratios such
that Equation #11 is true. RZ3 was set equal to 12.1kΩ.
Q
RZ 3 RZ 3

RZ 1 RZ 2
Q6
12.1k 12.1k

RZ 2
RZ 1
Equation 11: Determination of RZ2 & RZ1
RZ 2  2k
The output of the 60Hz Notch filter with an input of the PQRST wave is illustrated in
Figure #16. It can be seen that some ripple in the voltage has been added to the
waveform. This is common in ECG circuitry due to the fact the QRS complex frequency
component is very close to 60Hz. It is important to filter out 60Hz noise so that the little
ripple that results in the waveform at the output of the IC filter is a compromise due to
the resonance of the filter. The noise is small in comparison to the signal amplitude
and all three distinct waves (P, QRS, and T) are easily distinguished.
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Figure 16: Output Waveform of 60Hz Notch Filter
5.2.2.4 Isolation Circuitry
An isolation amplifier (ISO120) was used to isolate the ground of the circuitry from the
ground of the computer. This protects the circuit and therefore the patient from any
voltage spikes from the computer as well as the computer from the circuit. The input of
the amplifier is modulated and digitally sent across the barrier. The output section
converts the digital signal back to analog voltage and removes the ripple component
inherent in the demodulation. This creates separate grounds at the input and output of
the chip. The internal design of the Texas Instrument’s ISO120 is illustrated in Figure
#17. In the ECG design the isolation amplifier was connected to the output of the 60Hz
notch filter. It is important when building this design that two different grounding pins
are used one for all circuitry preceding the isolation amplifier and one for all circuitry
after the isolation amplifier. This will ensure safety of the patient.
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Figure 17: Internal Circuitry of Isolation Amplifier ISO120
5.2.2.5 Low Pass Filter
The ECG signal waveform is composed of relatively low frequency components under
100Hz. A low pass filter, LPF, was connected to the output of the isolation amplifier to
filter out any remaining ripple voltage created by ISO120 as well as any noise at higher
frequencies. A second order Butterworth active filter was designed to have a corner
frequency at 100Hz.
This means that any voltages above the corner frequency of
100Hz would not go through the filter. The schematic of this filter is depicted in Figure
#18[7].
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Figure 18: Schematic of Second Order Active Low Pass Filter
The resistor and capacitor values were determined by the using Equation #12. The
transfer function, H(s), is shown for a second order active low pass filter.
H(s) is
equivalent to the gain of the amplifier and in the case of this project was set to unity.
The values of R1 and R2 were set equal to 10kΩ and the value of C1 was set equal to
0.032µF. C2 was then solved for using Equation #12. The value of C 2 was found to be
equal to 0.016µF. The frequency response of this LPF is illustrated in Figure #19
below. It can be seen in this graph that voltage starts decreasing at the expected cutoff frequency of 100Hz.
This illustrates that the filter is performing correctly only
passing signals with frequencies less than 100Hz.
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



1
1


H s  

R1 R2 C1C 2    2  R1  R2 

1
s  

s



 


C
R
R
C
C
1
1 2 1 2 


Equation 12: Transfer Function of Second Order Active Low Pass Filter
Figure 19: Frequency Response of Second Order Active LPF
5.2.2.6 Biasing Output Waveform
The final stage of the analog circuitry biases the output waveform around a reference
voltage of 2 volts. This is due to the specifications of the input voltage of the Analog to
Digital converter (ADC) used.
The DrDAQ card requires positive input voltages
between 0 and 5 volts. Therefore the bias of 2 volts was chosen so that the ECG
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waveform would lie within these set boundaries. The circuitry used to accomplish this is
depicted in the PSpice schematic in Figure #20. The buffer op-amp in Figure #20 is
used to isolate the output resistance of the circuit from the high output resistance of the
low pass filter. The signal is passed through a simple RC low pass filter to again filter
out DC and summed with the 2 volts (from V24 in Figure #20) to bias it around 2v and
stay within the range needed by the DrDAQ. The 2 volts is attained from a linear 2v
regulator. The final output of the ECG analog signal is depicted in Figure #21. It can
be seen in the graph that the PQRST waveform is swinging positive and negative
around the bias voltage of 2 volts. The entire wave is occurring well within the specified
range of 0-5 volts.
100Hz LPF
Buffer Op-Amp
2 Volt Bias
Output to ADC
Input from
Isolation
Amplifier
Figure 20:
Circuitry Used to Bias Output Around 2V
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Figure 21: Final Analog Output of ECG Waveform
5.2.3 Analog to Digital Conversion & Data Acquisition
As mentioned previously the DrDAQ Data Logger, manufactured by Pico Technologies
was used to digitize the input analog voltage signal and display the data on a computer.
The DrDAQ package consists of a data acquisition card that has inputs to digitize light,
sound, temperature, and voltage signals.
computer.
It connects to the parallel port of any
Windows based software is also supplied with the DrDAQ to display
digitized data in time-series format.
The DrDAQ could also be interfaced with
LABVIEW with some necessary coding. The DrDAQ card has a 10-bit ADC and a
maximum digitizing rate of 15,000 samples per second. The resolution is 5mV with an
accuracy of 3%. illustrate
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5.3
Factory Simulation
The purpose of the Factory Simulation project is to attract students to the engineering
world and inform them of some of the tasks performed by an Industrial Engineer. The
most critical characteristic of this simulation is that it contains a realistic, real world
application that is appealing to students and will quickly grab their attention. The
simulation output will include animation to illustrate the movement of materials through
a production process and the different machines and/or workers they travel through.
This project will clearly display the effects of changing certain variables in a production
process and which variables are the most critical in the optimizing of the process. The
project will also contain a set of clear instructions on the proper way in which to run the
simulation, a default simulation containing all the inputs necessary to run the model, it
will display an output, clear instructions for changing different variables throughout the
model, and explain the effects of changing each variable in the model. At the
conclusion of this project, students will understand what factors an engineer must
consider when designing a production process or system, the key components that are
most crucial to the optimization of the process, and how the use of a simulation model
is very useful in the engineering world today.
The simulation itself will be built to model the production process of Hershey Chocolate
just as it is made in the factories today. This illustration will both grab the student’s
interest and give them a realistic model of what takes place in the manufacturing world.
The simulation model will present students with the actual process that produces
chocolate in a Hershey factory and allow them to change a few variables in order to
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optimize cost, which will be determined by output and total costs put into the system to
acquire a certain level of output. The class will be split into two or three groups in order
to allow the groups to compete against one another in the optimization of the system.
The instructions contained in this project will allow the teacher to explain the
significance and importance of each portion of the output as it relates to each variable
in the model. This is critical because if the students do not understand the data
presented by the output of the simulation, they will not understand the effects of
changing certain variables in the model in order to optimize the system.
The process that is being modeled in this simulation will contain a number of different
variables that the students can change in order to optimize the system. There will be a
total of five variables throughout the production process that they can manipulate to
optimize both cost and total output of chocolate. These variables will be number of
workers at a station in the beginning of the production process, the number of machines
at any given location, the number of workers at a station further down the production
line, and the mean time between failures for any one of the machines in the chocolate
production process. Although there are four different variables that can be changed in
the model, each group will only be allowed to change two different variables and these
changes will be limited to a certain extent. The original model will contain two workers at
two different locations along the production process, seven different machines, and 7
hours between failures for each machine. Any of these variables can be modified but
there is a limit to the extent each variable can be changed. If the students decide to
change the worker variable, they will only be able to add one worker to one of the
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locations along the production line, which will be one of their two total changes allowed.
Secondly, if the students decide to add machines at a certain location along the line,
only one machine per machining area can be added. Thirdly, if the mean time between
failures is modified, it can only be increased from 7 hours between failures to 8 hours
for only one machine. Since the object of this competition is to minimize cost, the
students will also be allowed to reduce one of the workers at either of the locations if
they think that it will not greatly affect output and significantly reduce their costs. An
arbitrary cost scale will be assigned to a number of different possible scenarios of
output. If one setup produces a certain level of output over that of the required output, a
cost penalty will be assigned. However, if this level is not reached, a cost reward will be
given for each level of output over the required output. Similarly, producing under the
required level of output will incur a cost penalty to be given. Each group will be allowed
one trial on the actual simulation model in order to try and improve upon their original
modifications. The group that produces their chocolate at the lowest overall cost will be
the winners of this exercise.
The logic and data that go into developing such a model can reach very high levels of
complexity. As a result, the main focus of this simulation will remain fairly simple and
the instructions will contain straightforward explanations as to why changing certain
variables cause greater effects to the overall outcome of the production process. The
most complex inputs of this model will already be incorporated, so the teacher only will
need to change simple variables such as number of workers or machines. Each
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variable, input, and output of the simulation will be carefully explained in the set of
directions and enable the teacher to manipulate the model as needed.
5.4
Mechanical Workstation
Consisting of three different demonstrations the Mechanical workstation will require
some analysis in a couple of different forms. The vibrating beam will require some
experimenting and testing to complete where the pendulum can be designed based on
physics equations.
5.4.1 Vibration Absorption
The Vibrating Beam experiment consists of two beams that will have the same natural
frequency. The Primary beams natural frequency will be experimentally determined
while the Secondary beam will be designed to have the same natural frequency as the
Primary beam. This is necessary for the vibrations to be properly absorbed. The natural
frequency is calculated using Equation 13.
w
k
m
k
3EI
l3
Equation 13: Natural Frequency Equation
Equation 14: Spring Stiffness
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Figure 22: Graphic of the system of beams
Figure 22 is a graphic rendering of what the system of beams will look like. The primary
beam with be excited with a 12 volt DC motor mounted at the end of the beam with an
off center brass weight attached to the shaft of the motor. This traveling exhibit will be
plugged into a 120 volt wall outlet to power the motor. In order to power a 12 volt DC
motor from a standard wall outlet an AC to DC power transformer is required. In order
to adjust the vibrations, adjustment of the speed at which the motor rotates is
necessary. In order to do so a 12 volt DC speed controller is used. A preliminary
prototype beam has been constructed to begin the experimentation process. The 12
volt DC speed controller was built from a purchased kit and a power supply is currently
being used for a power source. Figure 22 is a picture of the preliminary prototype beam
setup.
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Figure 23: Picture of the preliminary prototype vibrating beam setup
The above setup yielded an amplitude range of 1 inch to 3 inches. A strobe-a-scope will
be used to determine the frequency that the beam is vibrating at. Further investigation
will be required to complete the design of the primary beam before designing the
secondary beam.
5.4.2 Vibration Dampening
Dampening vibrations using dampening materials and creating composite materials is
very effect. Its success relies highly on the adhesion between the dampening material
and the material in which it is sandwiched between. Due to the fact that controlling the
adhesion between materials can at times be a difficult task that may in fact yield
undesirable results the Vibration Dampening experiment will be purchased from a
dampening material manufacturer.
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5.4.3 Motion of a Pendulum
The simple pendulum is a perfect example of simple harmonic motion. A pendulum
consist of a mass suspended from the end of an constant length, mass less string of
length L. Equation 15 tells us that the angular acceleration α of the pendulum is
proportional to the angular displacement θ but opposite in sign.

mgL

I
Equation 15: Angular acceleration of a pendulum
A graphics rendering of the pendulum exhibit is available in Figure 24. Complete
mechanical drawing packages for both the vibration absorbing beam and the pendulum
can be found in Appendix D.
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Figure 24: Graphic of the pendulum exhibit
5.5
The Theremin
5.5.1 Problem Statement
The Moog Theremin will be built and demonstrated. Representations of the
internal components of the Theremin will be constructed to provide a step-by-step
understanding of how the Theremin operates.
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5.5.2 Summary of Known Information
Known (typical) values in Moog Theremin [3]:

±12V Power Supply

Antenna Capacitance: 10-15pF

Pitch Antenna Resonant Frequency: 285kHz

Power Adapter: 14V AC at 200mA

Volume Antenna Resonant Frequency: 450kHz
5.5.3 Assumptions

Hand capacitance is less than 1pF.

At or near resonant frequency, a tiny change in hand capacitance results in a
larger change in the impedance of the antenna circuit.

The variable pitch oscillator, in conjunction with the pitch oscillator circuit, can
enable usage pitch ranges up to 5 octaves (two below, and three above middle
[3]
when the right hand is moved around a two feet distance.

The volume antenna circuit, in conjunction with the volume oscillator, controls the
gain of a voltage-controlled amplifier, which causes volume to decrease to silent
as the left hand approaches the volume antenna.
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5.5.4 Schematics
Figure 25
[3]
is the block diagram representation of the Moog Theremin. The
schematic of the complete Moog Etherwave Theremin circuit
[3]
can be referenced in
Appendix C. The main components of the Theremin are shown in Table 5-1.
Pitch Components
Pitch Antenna Circuit
Pitch Oscillator (Fixed)
Pitch Oscillator (Variable)
Pitch Tuning Circuit
Pitch Detector
Volume Components
Volume Antenna Circuit
Volume Oscillator
Voltage Controlled Amplifier
Volume Tuning Circuit
Table 5-1: Moog Theremin Components
Figure 25: Block Diagram of Moog Theremin
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5.5.5 Analysis
Figure 26
[4]
shows the actual antenna circuit of the Theremin, which is
representative of both the pitch and volume antenna circuitry. The antenna coil (large
inductor), antenna capacitance, and hand capacitance form a resonant circuit. The
resonant frequencies are about 285 kHz for the pitch antenna, and 450 kHz for the
volume antenna. At or near resonant frequency, a slight change in hand capacitance
results in a considerable change in the impedance of the antenna circuit as a whole.
The equivalent circuit can be created to measure changes in hand capacitance for both
pitch and volume. The equivalent circuit can be created and simulated using PSPICE
and an oscillator can measure pitch and volume output on the actual Moog Theremin.
Figure 26: Actual Antenna Circuit and the Equivalent Electrical Circuit
6 Preliminary Design
6.1
Alternative Energy
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6.2
Electrocardiograph
Protection
Circuit
Instrumentation
Amplfier
Bandpass
Filter &
Amplifier
Right Leg
Drive
60Hz
Notch
Filter
Isolation
Amplifier
100Hz Low
Pass Filter
DrDAQ
Figure 27: Block Diagram of ECG
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Bill of Materials for ECG:
Part Description
Part ID
Single Op-Amp
OPA237
Isolation Amp
ISO124
Instrumentation Amp
2.2kohm resistor
INA114
-
Single Op-Amp
TLC277
Filter
9v batteries
battery strap & connector
-12V Voltage Regulator
+12V Voltage Regulator
+5V Voltage Regulator
UAF42
MC7912
UA7812
UA7805
LM117
MLA1010
MLA2503
-
Adjustable Voltage Regulator
Electrodes
Shielded Lead Wires
DrDAQ Data Logger
Printed Circuit Board
Laptop
IC Type
Quantity
Price
Company
DIP
SOIC
DIP
SOIC
DIP
SOIC
n/a
DIP
SOIC
DIP
SOIC
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
5
5
1
1
1
1
8
4
4
1
1
12
10
2
2
1
1
100
3
1
1
1
$6.90
$6.90
$12
$12
$8.40
$8.40
$8.00
$8.00
$12.58
$12.58
$17.04
$17.04
$3.40
$1.06
$1.04
$1.04
$13.00
$60
$60
$106
$70
$1,000
Digikey
Digikey
Digikey
Digikey
Digikey
Digikey
Digikey
Digikey
Digikey
Digikey
Digikey
Digikey
Digikey
Digikey
Digikey
Digikey
Digikey
Powerlab
Powerlab
Picotechnologies
PCB Express
Unknown
Total
Cost
$1,445.38
Table 6-1: Bill of Materials for the Electrocardiograph
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6.3
Factory Simulation
Figure 28: Flowchart of the proposed Factory Simulation: The Manufacturing of Hershey’s Chocolate
The only cost included with a Factory Simulation using ARENA software would be the
cost of a laptop computer and possible a single license of the program itself.
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6.4
Mechanical Workstation
Figure 29: Picture of Vibration Absorbing Beam
Donated
Donated
Donated
Donated
Donated
Donated
Donated
Donated
20
5
1
2
TOTAL
2.798
Donated
Donated
Donated
5.78
0.072
0.3036
0.02772
11.05
20
5
1
8
51.28546
Table 6-2: Bill of Materials for the Vibration Absorbing Beam
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Figure 30: Preliminary Pendulum Design
ITEM QTY PART NUMBER
1
1
BS-001
2
1
P-001
3
1
B-002
4
1
BB-001
5
2
BKT-001
6
2
60355K62
7
13
91251A537
8
1
97431A300
9
1
94820A232
10
1
A-001
11
1
DESCRIPTION
BASE
PENDULUM
BACK
BEARING BLOCK
ANGLE BRACKET
BEARING 1/4" SHAFT
1/4"-20 x 1/2" SOCKET HEAD
E- RETAINING RING 1/4" SHAFT
LOCKNUT - STEEL 1/4"
AXEL
Weight
VENDOR
TOTAL
MASS
4.091 lbmass
0.867 lbmass
3.411 lbmass
0.138 lbmass
0.383 lbmass
0.040 lbmass
500 g
8.93 lbmass
COST/ITEM
Donated
Donated
Donated
Donated
Donated
Donated
Donated
Donated
Donated
Donated
Donated
COST
Donated
Donated
Donated
Donated
Donated
Donated
Donated
Donated
Donated
Donated
Donated
0
Table 6-3: Bill of Materials for the Pendulum
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6.5
The Theremin
Expenses
[6] Moog Etherwave Theremin Kit – $299.95, free shipping, tax free

Ordered online at http://www.zzounds.com/item--BIGETHERWAVEKIT
Bill of Materials
[3]
The Moog Etherwave Theremin kit contains the following items:













15" length of green hookup wire for panel wiring
8" length of black hookup wire for panel wiring
8" length of heavy (18AWG) solid copper bus wire
Anodized Aluminum Panel
Assembled Circuit Board
'Clara Rockmore: The Greatest Theremin Virtuosa' Videotape
Etherwave Theremin Assembly booklet
'Mastering the Theremin' Videotape
Pitch Antenna (18" straight tube)
Volume Antenna (loop tube)
Wall-mount Power Transformer
Wood Cabinet
Small Plastic Bag of Parts
o 4 - 1/2" x #6 wood screws (for mounting the panel and the microphone
stand flange, and for grounding the foil shield)
o 2 - 1/4" x 4-40 machine screws (for mounting solder lugs to the antenna
connectors)
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
o 5 - 1/4" x 6-32 machine screws (for mounting the printed circuit board)
o 4 - 7/8" x 6-32 flat head black machine screws (for mounting the cabinet
top to the base)
o 2 - #4 locking solder lugs (for providing electrical connection to the
antenna connectors)
o 1 - #6 locking solder lug (for providing electrical connection to the
aluminum foil)
o 5 - Threaded standoffs (for holding the printed circuit board)
o 4 - 5/16" inside diameter lock washers (for mounting the potentiometers)
o 1 - 3/8" inside diameter heavy lock washer (for mounting the audio output
jack)
o 1 - 3/8" diameter black plastic cap (for pitch antenna)
o 3/8" inside diameter flat washer (for mounting audio output jack)
o 3/8” nut (for mounting audio output jack)
o 8-32 x ¾” machine screws (for installing mic stand adapter)
o 8-32 Tee-nuts (for installing mic stand adapter)
Large Plastic Bag of Parts
o 2 - 5 Kilo ohm Potentiometer (numbered B5K)
o 2 - 50 Kilo ohm Potentiometer (numbered B50K)
o 1 - Microphone Stand Flange (marked Atlas AD-11)
o 4 - Black Knobs
o 1 - 1/4" Phone Jack
o 1 - Black plastic rocker switch
o 1 - Nickel-plated Elbow Pipe Connector - 3/8" Pipe to 3/8" Tube
o 2 - Nickel-plated Straight Pipe Connectors - 3/8" Pipe to 3/8" Tube
o 3 - Brass Compression Rings (shipped attached to pipe connectors)
o 3 - Nickel-plated Compression Nuts (shipped attached to pipe connectors)
o 2 - Self-adhesive Felt Strips
o 1 - Ten-wire female connector
Maintenance
[3] The Etherwave Theremin requires no routine maintenance. Many years of troublefree, reliable performance may be expected, if the following common-sense precautions
are observed:

Never expose the instrument to extremely hot, cold, or damp environments.
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
Don't allow inexperienced people to tamper with the instrument's controls or
internal mechanism.

Don't drop the instrument, or subject it to excessive vibration.
7 Final Design
At the start of Senior Design II much of the group had begun final designs. The team
initially was responsible for creating five different teaching aids. One of the five teaching
aids was completed over winter quarter, leaving the three remaining members to
complete the remaining four aids during Senior Design II. With only three team member
left, it was decided that one of the four teaching aids was not feasible to complete. It
was decided to eliminate the Alternative Energy teaching aid from the list. This was
discussed and approved by the teams mentor.
7.1
Electrocardiograph
Some improvements were made to the ECG circuitry in its final design stages. The
design was built on hardware and tested for proper operation prior to designing on the
printed circuit board (PCB). All of the basic principles of the circuit remained the same
as was laid out in the original design. Refer to Figure 31 to see the final schematic of
the ECG circuitry.
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Figure 31: Final Schematic of ECG in Orcad Capture
A small battery monitoring circuit was added to the design to alert the user when to
change the batteries. This circuit is shown in Figure 32. A Light Emitting Diode (LED)
is used as an indicator to notify the user when the batteries need to be changed. The
LED turns out when the battery voltage drops below 6.5 volts. This value was set by
the potentiometer (R33 in Figure 32) in the design.
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Figure 32: Schematic of Battery Monitor Circuit
The Bandpass Filter and Amplifier stage was altered minutely to have an adjustable
gain by inputting a potentiometer into its design (R28 in Figure 33). This allows the
value of the external resistance of the amplifier stage to vary so that the amplitude of
the ECG signal can be controlled. This makes the circuit more interactive so that the
student can physically turn the potentiometer with a screwdriver and learn about
amplification by watching the ECG signal amplitude change.
Figure 33: Amplifier Stage with Varying Gain
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A custom PCB was designed using CAD software supplied by ExpressPCB. A twolayer board was designed over an area of 42 square inches. ExpressPCB
manufactured and delivered two copies of the circuit board. All devices were soldered
into the board and electrical testing was completed within the lab facilities at RIT. An
illustration of the CAD design can be viewed in Figure 34.
Figure 34: PCB Design of ECG in CAD
Many problems occurred with the data acquisition instrument, DrDAQ, originally ordered
from Picotechnologies. The circuit was designed and tested while interfaced with a
desktop PC. When tested on a laptop 60Hz noise became prevalent and the ECG
signal could no occur.
Luckily the laptop purchased to accompany the project did
indeed have a third grounding pin.
Although the grounding issue was solved, a new issue arose between the data
acquisition device (DrDAQ) and the purchased laptop.
The DrDAQ is designed to
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communicate with a computer through a 25 pin serial cable. Laptops no longer come
standard with any serial connections; therefore a serial to USB adapter was purchased
from Picotechnologies to accommodate the available connections on the computer.
The serial to USB adapter contains a design error by Picotechnologies in which a long
delay is added to the signal. Due to the fact that the ECG is at a low frequency
(approximately 1 Hz) the signal could no longer be viewed real time on the software
supporting the DrDAQ device.longer be seen through the noise. It was determined that
this occurred due to improper grounding of the DrDAQ when taking differential
measurements as in the ECG circuit design. The power plug of the laptop did not have
a grounding pin; therefore 60Hz noise was being added to the signal through the
computer. When running on any computer with a third grounding pin on the power
plug, this issue did not
A new DAQ device was donated to the team by the Mechanical Engineering
Department at RIT. The MiniLab 1008, by Measurement Computing Company, was
utilized to perform the needed analog to digital conversion and interface with LabView.
The MiniLab 1008 is very sufficient in performing differential measurements and
communicates with the computer through a USB cable.
A Labview interface was
created to display the ECG signal in a real time fashion (with some small delay of
approximately 20ms). A depiction of the interface screen is illustrated below in Figure
35.
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Figure 35: Illustration of LabView Interface for ECG Monitoring
To protect the circuit board and soldered wire connections of the batteries and
electrodes the ECG circuit board was mounted between two pieces of acrylic. This will
allow students to see the entire PCB without being able to touch the actual parts easily.
All wires were zip tied down to the acrylic to keep them from being pulled and broken.
The MiniLab 1008 DAQ was mounted to the bottom of the acrylic holder so that each
piece is attached to a single unit. A picture of the final ECG device is shown below in
Figure 36.
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Figure 36: Depiction of Final ECG Design
7.2
Factory Simulation
The Arena program included in this project contains a representation of a real-life
assembly line. The assembly line that is modeled in this project is one that produces
chocolate candy bars. The simulation itself is fully animated and shows the actual flow
of chocolate through an assembly line, beginning with the cocoa bean and ending with
the candy bar.
The Willy Wonka Chocolate Factory allows students to visually see how materials,
workers, and machines work together to produce a product. The assembly line contains
nine different workstations that all have workers and machines working together to aid
in the chocolate production process. The only station that does not need a worker is the
Cooling Tunnel Station because it’s simply a tunnel that is used to help reduce the
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temperature of the chocolate and help it form into its solid state. The simulation also
contains a forklift area that is responsible for transporting the finished and wrapped
candy bars to the loading area. This gives students a feel for what really takes place at
the end of an assembly line in a manufacturing environment. The user has the ability to
zoom into any of the nine stations mentioned above and the forklift area by simply
pressing different keys on the keypad. These navigation keys are described in the main
menu of the program for the user in order to help them move around to different areas
of the simulation. Once the user is zoomed into a specific production area, they can see
up close the way in which workers and machines are used in the production of
chocolate.
The user has the ability to change the number of resources used along the assembly
line in order to try and optimize the system. That is, the user can try and change the
number of workers, machines, or forklifts in the system to maximize the assembly lines
throughput (output). This functionality created within the Arena program is a very
efficient way to show the user how improving the bottleneck station of the system will
get you the best results, in terms of the systems throughput. The user can change
these resources by simply selecting a worker, machine, or forklift and then increasing or
decreasing the number of these resources at any station along the assembly line. Once
the user has changed the desired resources, they can run the simulation to see the
effect of the change on the throughput of the system.
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After the simulation has completed its run sequence, Arena outputs a number of
different statistics for each of the workstations along the assembly line. These statistics
reveal a great deal about what is taking place along the assembly line and what can be
done to improve it. The user will be shown the throughput of the system, the utilization
of each station along the assembly line, and the average size of the queue at each
station waiting to be processed during the production of the candy bars. This
information will allow the user to locate the bottleneck station and improve it to increase
the throughput of the system.
The final design package will also include a few other teaching aids that will improve the
quality of the Industrial Engineering presentation to the students. Along with the factory
simulation, there is a PowerPoint presentation that gives some background on Industrial
Engineering and eventually leads into the Arena simulation program. The presentation
also contains a few anecdotes that will pique the kid’s interest in engineering and make
then rethink a few of the things that they have taken for granted up to this point in their
life. There is also an activity packet that is included in the final design package. This
activity packet will lead the girls in a competition using the Willy Wonka Chocolate
factory simulation. It will also give the students background on the machines needed to
produce chocolate in real world applications such as Hershey and Godiva Chocolate.
Finally, the final design packet contains a detailed instruction manual that will help
navigate the user through the Arena simulation program. The manual contained in this
project gives very specific actions for the user to follow to properly operate the
simulation contained in this project.
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Changes Made to Design
There were a few changes made to the final design of the Willy Wonka Chocolate
Factory from the original design developed in Senior Design 1. Most of the changes that
were made to the Arena program were as a result creating a more user-friendly
simulation that could be easily operated by any user. This came as a result of the
difficulty associated with running the simulation by users other than the designer of the
program. A few of the changes made were also necessary in order to improve the
aesthetics of the program and its future appeal to both students and teachers.
The first deviation made from the original design was the incorporation of a visual basic
user-input window used for changing the resources in the simulation. It became
apparent early on in the construction of this simulation that the user would not be able
to change the capacities of each worker, machine, or forklift by the typical methods
used in creating the program. This was simply because if the user is not familiar with
the program, making changes to a simulation can be very tedious and confusing. As a
result, an interface was designed for the user to allow the simple manipulation of
different resources in the assembly line. This can be accomplished by selecting a
resource to change and then choosing the amount of the resources that the user wants
to add to a specific workstation along the assembly line. Once the user has finished
selecting the resources they wish to change, by simply pressing the “Run Simulation”
button the Arena program will begin to run and chocolate will begin to flow through the
assembly line.
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Another aspect of the final design that was modified was the objects the user would be
able to manipulate. In the original design, the user would have the ability to change the
amount of time each machine produced chocolate before it broke down and needed to
be fixed. This was changed however because the team thought that this might be too
advanced of a concept for this project and it would be very difficult to recognize
anything definitive in the results; in terms of throughput. Instead, the final design allows
the user to add a machine to a specific workstation to try and increase throughput.
A third element of the design that was modified was the way in which the user viewed
the results from the simulation. In the original design, the user would have been taken
to Arena’s main results window. This window is very confusing however for a novice
user and can be up to 20 pages long filed with compiled data. In the modified final
design, Arena immediately outputs a results page that only displays the statistics that
are in the scope of this project. This allows the user to quickly view the throughput of
the system, the utilization of each workstation, and the average queue waiting to be
processed at each workstation. Once the user is finished viewing the results, they can
close the window and return to the main assembly line window of Arena.
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Figure 37: ARENA Simulation Screen Shot
Overall, the final design contained in this project was made as aesthetically pleasing as
possible. The main goal of this project is to grab the attention of high school and middle
school students, and this project was constructed to meet this requirement accordingly.
A screen shot from the simulation is shown in Figure 37.
7.3
Mechanical Workstation
The Mechanical Workstation underwent very few design changes from the initial
design.
One very important contribution to the cost savings of the Mechanical
Workstation was the materials obtained by the senior design team from local vendors.
All of the aluminum to build the project was donated. The vibrating beam took on a
professional look with a rich blue anodized finish to the aluminum. The beam’s base
was strengthened with two gusset supports to reduce fatigue and flexing of the base
while the beams are in motion. These gussets are not entirely necessary although add
likable strength and made it possible to house the electronics of the system.
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Figure 38: Final Vibrating Beam Design
As opposed to purchasing a dampened beam from a supplied vendor like planed, it was
decided to construct a motor driven beam with its own vibration dampening
characteristics. The beam lengths were ultimately decided at ten inches. A length of
ten inches was chosen based on safety and performance.
The Pendulum did undergo some favorable upgrades. To begin with some weight
reduction the base was divided into two feet saving one third of the base weight (2lbs).
The support gussets were not necessary and were removed and the base feet were
lengthened by two inches for added support and stability.
The final design
modifications were the two handles machined into the back plate of the pendulum. The
pendulum also shares the rich blue anodized finish to give it a professional look.
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Figure 39: Final Pendulum Design
7.4
The Theremin
There were no changes in the original Theremin design. The Moog Etherwave
Theremin kit was purchased as well as set of speakers so that sounds can be heard
from the Theremin. The Theremin was built according the directions in the kit and was
stain finished giving it a professional look. The Theremin was tuned in order for the
human ears to detect a simple range of high and low pitches. An instructional manual
was created as well as activities that may be used to further demonstrate the
engineering concepts involved with building and using the Theremin. The Theremin was
presented at the Genesee Valley Girl Scouts Workshop and several participants
demonstrated the musical capabilities of the Theremin; as see in Figure 40.
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Figure 40: Final Pendulum Design
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Works Cited
[1] Webster, John G., Medical Instrumentation – Application and Design. USA, 1998.
[2] Moog Music Inc., 2003, “Setting Up and Playing the Moog Etherwave Theremin
Manual,” <http://www.moogmusic.com/manuals/ewave_user.pdf>
[3] Moog Music Inc., 2003, “Building and Playing the Moog Etherwave Theremin
Manual,” <http://www.moogmusic.com/manuals/ASSMAN03.pdf>
[4] Moog Music Inc., 2003, “Understanding, Customizing, and Hot-Rodding Your
Etherwave Theremin Manual,”
<http://www.moogmusic.com/manuals/HotRodEtherwav.pdf>
[5]Moog Music Inc., 2003, “Etherwave Theremin,”
<http://www.moogmusic.com/detail.php?product_specs=1&modify=true&main_pr
oduct_id=14>
[6] ThereminWorld., 2003, “Moog Music Etherwave Theremin Kit,”
<http://www.thereminworld.com/shop_theremins.asp>
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Appendix A
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Appendix B: ECG Related Materials
Figure 41: Complete Schematic of ECG
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Appendix C
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Appendix D
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