May 11, 2016 Team #15: CoachJav Final Report Kwesi Asare, David Dadzie, Ofiliojo Ichaba, Landon Potts ENGR 340 Senior Design Project 2016, Calvin College © Kwesi Asare, David Dadzie, Ofiliojo Ichaba, Landon Potts
Calvin College, Calvin Engineering Dept. 2015-2016
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1. Executive Summary
Data and statistics is a common thing in most sports and events, but one sport where stats are
lacking is the javelin throw in track & field. Thus Team 15, made up of four electrical
engineering students, created CoachJav to attach to a javelin and capture data. The device
collects information about a javelin throw using a variety of sensors, and relays the stats,
including velocity of throw and angle of release, to an app on an Android device. The stats about
the throw can be seen by the coach or athlete to then improve their throwing, especially their
technique. These stats can also be displayed to the fans of the sport to make the event more
exciting. The device as a product can fill a niche in the market for javelin coaches, athletes,
researches, or fans. This makes CoachJav a feasibly marketable product for a profitable
company.
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Table of Contents
1. Executive Summary ................................................................................................................ 2 2. Introduction ............................................................................................................................. 8 3. Project Management ............................................................................................................. 10 3.1. Team #15 ........................................................................................................................ 10 3.2. Team Organization ......................................................................................................... 11 3.3. Budget ............................................................................................................................ 13 3.4. Method of Approach ...................................................................................................... 13 4. 3.4.1. Research Method .................................................................................................... 13 3.4.2. Team Communication Method ............................................................................... 14 3.4.3. Design Method ........................................................................................................ 14 Requirements ........................................................................................................................ 15 4.1. Design Schedule ............................................................................................................. 17 4.2. System Architecture ....................................................................................................... 18 4.3. Design Norms ................................................................................................................. 19 4.3.1. Trust ........................................................................................................................ 20 4.3.2. Cultural Appropriateness ........................................................................................ 20 4.3.3. Caring ...................................................................................................................... 21 4.3.4. Integrity ................................................................................................................... 21 4.4. Design Components and Alternatives ............................................................................ 21 4.4.1. Sensors .................................................................................................................... 21 4.4.2. Microcontroller ....................................................................................................... 22 4.4.3. Power Source .......................................................................................................... 24 4.4.4. Data Communication .............................................................................................. 26 4.4.5. User Interface .......................................................................................................... 27 4.5. Final Design ................................................................................................................... 29 4.5.1. Prototype Components ............................................................................................ 29 4.5.2 The CoachJav App ....................................................................................................... 32 5. Business Plan ........................................................................................................................ 35 5.1. Company Description ..................................................................................................... 35 5.1.1. Team ....................................................................................................................... 35 3
5.1.2. Board of Directors and Advisors ............................................................................ 36 5.1.3. Company Structure ................................................................................................. 36 5.2. Operations ...................................................................................................................... 37 5.3. Financial Statements ...................................................................................................... 37 5.4. SWOT Analysis.............................................................................................................. 38 5.4.1. Strengths ................................................................................................................. 38 5.4.2. Weaknesses ............................................................................................................. 38 5.4.3. Opportunities........................................................................................................... 38 5.4.4. Threats..................................................................................................................... 39 5.5. Marketing ....................................................................................................................... 39 6. 5.5.1. Target Market.......................................................................................................... 39 5.5.2. Demographic Profile ............................................................................................... 40 5.5.3. Other significant customer characteristics .............................................................. 40 5.5.4. Desired Image in Market ........................................................................................ 40 5.5.5. Market Size and Trends .......................................................................................... 40 5.5.6. Advertising and Promotion ..................................................................................... 41 5.5.7. Pricing ..................................................................................................................... 41 5.5.8. Distribution Strategy ............................................................................................... 42 Testing................................................................................................................................... 43 6.1. Apparatus ....................................................................................................................... 43 6.2. Method ........................................................................................................................... 44 6.3. Results ............................................................................................................................ 45 6.3.1. Angle of Release ..................................................................................................... 45 6.3.2. Velocity ................................................................................................................... 46 7. Future Work .......................................................................................................................... 48 8. Conclusion ............................................................................................................................ 49 9. Acknowledgements ............................................................................................................... 50 10. Appendix ............................................................................................................................ 51 10.1. Assembly Drawing of Prototype ................................................................................ 51 10.2. Obtaining Angles through Kalman Filter ................................................................... 52 10.3. Test Data ..................................................................................................................... 53 10.3.1. Testing Angle Data.............................................................................................. 53 4
10.3.2. 10.4. Testing Velocity Data.......................................................................................... 54 Financial Statements ................................................................................................... 55 10.4.1. Income Statement ................................................................................................ 55 10.4.2. Cash Flow Statement ........................................................................................... 55 10.4.3. Cost Analysis....................................................................................................... 56 5
Table of Figures
Figure 1: Team #15 Photo............................................................................................................. 10 Figure 2: Organizational Structure................................................................................................ 12 Figure 3: Work Breakdown Schedule ........................................................................................... 18 Figure 4: System Flow Diagram ................................................................................................... 19 Figure 5: Block Diagram .............................................................................................................. 19 Figure 6: Arduino Size Comparison ............................................................................................. 24 Figure 7. Battery Space within CoachJav Design ......................................................................... 25 Figure 8. Component Assembly for CoachJav ............................................................................. 30 Figure 9. 3D model of Final Prototype of CoachJav .................................................................... 31 Figure 10. CoachJav Final Prototype ............................................................................................ 31 Figure 11: Concept Design Fit to Javelin ..................................................................................... 32 Figure 12: Layout of Main Activity Android App........................................................................ 33 Figure 13: Layout of Display.xml ................................................................................................. 33 Figure 14: Speed and Angle in Android App ............................................................................... 34 Figure 15: Company Structure ...................................................................................................... 37 Figure 16: Slingshot Crossbow Javelin Launching Apparatus for Testing .................................. 43 Figure 17. CoachJav after shock-resistance testing ...................................................................... 44 Figure 18: Angle of Release Testing Results ................................................................................ 46 Figure 19: Velocity Testing Results ............................................................................................. 47 Figure 20: Assembly Drawing of Prototype ................................................................................. 51 6
Table of Tables
Table 1: Budget Breakdown ......................................................................................................... 13 Table 2. Decision Matrix for Arduino Microcontroller ................................................................ 24 Table 3. Decision Matrix For Battery Selection ........................................................................... 25 Table 4: Data Communication Decision Matrix ........................................................................... 27 Table 5: User Interface Decision Matrix ...................................................................................... 29 Table 6: Testing Angle Data ......................................................................................................... 53 Table 7: Testing Velocity Data ..................................................................................................... 54 Table 8: Income Statement ........................................................................................................... 55 Table 9: Cash Flow Statement ...................................................................................................... 55 7
2. Introduction
Competitive athletes have a constant objective of improving their performance. In order to do
this, the athletes and their coaches adopt a wide spectrum of methods to get the necessary
feedback of athlete performance. For instance, Zepp Tennis is a program that monitors the speed
of the serve and other important performance parameters of tennis players. Other sports such as
golf, sprints, and baseball have similar feedback systems in place.
One sport that does not have such a system is the javelin throw in the sport of track and field.
Digging deeper into the javelin throw, the team found out that there are certain technical factors
that affect the javelin throw. These include, but are not limited to, the athlete’s technique,
approach speed, angle of release, velocity of release, and angle of yaw. Although these factors
vary by individual, there are certain techniques that generally produce better throwing results.
However, there is no viable method of determining the optimum values that provide the best
results. The current method used involves the athlete and their coach determining the best
technique based solely off of their observation, a method which is generally unreliable and
imprecise. At a higher level, Olympic researchers have tried to establish a correlation between
the factors mentioned above to determine the optimum values for these factors. Although their
method is not as crude as the other method mentioned above, it requires expensive equipment
such as multiple high speed cameras, specialized javelins, force sensors, and a controlled
environment. Another disadvantage of this system is that, because it uses data modeling, it is not
very individualized.
Team #15 CoachJav, made up of four electrical engineering students, designed a device that
attaches to a javelin, records data from a throw, and sends it to the athlete or coach via a mobile
device application. The coach or athlete can see the velocity of the throw, the angle of release of
the javelin, and the distance thrown, all in real time. The coaches or athletes can use the
quantitative data to effectively assess the athlete’s performance, monitor their progress, and help
the athlete see what areas the athlete is executing well and where they can improve. If the coach
or athlete can get this information in fewer throws, it is extremely helpful so the athlete can have
a more focused practice, and maybe throw the javelin less. Fewer throws helps the thrower
especially because each throw forces the athlete to exert a lot a stress on their body and tires
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them out, and also can help the coach with shorter practices and more focused training on the
improvement areas.
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3. Project Management
3.1.
Team #15
The design team is made up of four senior electrical and computer engineering students, pictured
in Figure 1 below.
(left to right) - David Dadzie, Ofiliojo Ichaba, Landon Potts, Kwesi Asare
Figure 1: Team #15 Photo
Kwesi Asare
Kwesi Asare is a senior Electrical & Computer Engineering student from Tema, Ghana. He is
also a freelance photographer and digital media designer. This past summer, he worked as an
electrical engineering Intern for Herman Miller, Inc., a reputable furniture making company in
West Michigan. He programmed a microcontroller unit that was implemented in a sit-to-stand
desk as part of a project in transforming the switch mechanism to an automated sit-to-stand
mechanism. In his free time, Kwesi likes to cook exotic meals, play the piano, and edit photos.
Landon Potts
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Landon is a senior Electrical & Computer Engineering student from Caledonia, Mi. He is a fouryear member of both the Men's Varsity Cross Country Team as well as the Men's Varsity Track
& Field Team here at Calvin. The summer before his senior year, he worked for
www.hymnary.org developing an Android app which can be used to view hymnals. In his
[limited] free time, Landon stays very active. His hobbies include running, swimming,
watersports, roller skating, and ultimate Frisbee, as well as spending time with friends and
family.
Ofili Ichaba
Ofiliojo is a senior Electrical & Computer Engineering student from Lagos, Nigeria. He is
currently serving on the Calvin College Student Senate. Ofili has a strong interest in computer
science, particularly in artificial intelligence and Natural Language Recognition research. His
hobbies include singing, soccer, and reading.
David Dadzie
David is a senior Electrical & Computer Engineering student from Accra, Ghana. He is a fourth
year member as well as a team captain of the Men's Varsity Track & Field Team at Calvin
College. This summer, he worked on a research project, with Professor Yoon Kim, to design and
construct a DC-DC constant current, constant voltage solar simulator. The results of the research
project can be viewed at www.calvin.edu/academic/science/summer. David enjoys the broad
range of music genres across the world and loves playing the drums. His hobbies include
bowling, table tennis, and RPG games, as well as spending time with friends and family.
3.2.
Team Organization
The team is setup to be very collaborative, meaning tasks are distributed fairly among the team
members. However, to avoid redundant work, each member of the team was assigned a section
of the overall project. The breakdown of assigned tasks was as follows:

Kwesi Asare – Filtering Data and Business Plan

David Dadzie – Hardware PCB Design and Testing

Ofiliojo Ichaba – User Interface - Android App Development
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
Landon Potts – Coding Microcontroller and Sensor Work
Other important stakeholders involved in the project include:

Faculty Advisor, Professor Mark Michmerhuizen – The role of the faculty advisor,
among other things, was to make sure the team stayed on track to meet all the project
deadlines at the appointed times. He was also the point of contact between the team and
the senior design project administrator.

Industrial Consultant, Mr. Eric Walstra – The Industrial Consultant met with the team
once a semester. His role was to guide the team in making good design and engineering
decision. Mr. Walstra was extremely helpful in determining the main risk points of the
project, before the team ran into them.

Client, Bret Otte – Bret Otte is the Calvin College Head Track & Field Coach, and in
charge of the college's Javelin team. His role in this project was to determine the
constraints of our design.
The other senior design course instructors are Professor Nielson, Professor VanAntwerp, and
Professor Masselink. Figure 2 above shows an organizational chart of all the stakeholders for the
project.
Course Instructors
Faculty Advisor
Industrial Advisor
Team 15
Client
Figure 2: Organizational Structure
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3.3.
Budget
For the project, the team was allotted $500 by the Calvin Engineering Department. The team
procured several Arduino boards, multiple sensors including GPS modules and Inertial
Measurement Units (integrated combination of accelerometer, gyroscope, and magnetometer),
batteries, and testing equipment. The accrued amount spent on these components was $307.59,
leaving $192.41 still in the team budget. The budget breakdown can be seen in Table 1 below.
Table 1: Budget Breakdown
Component
ADXL335 - triple-axis accelerometer
Flora 9-DOF accelerometer/Gyroscope/Magnetometer
Standard LCD 16 x 2 + extras
3V Lithium Coin Battery (225 mAh) CR2032
3V Lithium Coin Battery (137 mAh) 16mm
Flora Wearable Ultimate GPS Module
Arduino Pro Mini 328 - 3.3V/3MHz
Sparkfun FTDI Basic Breakout - 3.3V
Bluetooth SMD Module - RN-41 (v6.15)
Strap Battery Econ 9V I Style 4"LD
Coin Cell Holder for 16mm Cell
Coin Cell Holder for CR2032
Passive GPS Antenna uFl - 15mm x 15mm 1 DBi Gain
Passive GPS Antenna uFl - 9mm x 9mm -2 DBi Gain
Sparkfun Bluetooth Mate Gold
Total
Quantity
1
2
1
2
2
2
2
2
1
2
2
2
1
1
1
Price
Cost
$14.95
$14.95
$19.95
$39.90
$9.95
$9.95
$1.99
$3.98
$1.95
$3.90
$39.95
$79.90
$9.95
$19.90
$14.95
$29.90
$25.95
$25.95
$0.60
$1.20
$1.39
$2.78
$0.74
$1.48
$3.95
$3.95
$4.95
$4.95
$34.95
$34.95
$307.59
3.4.
Method of Approach
3.4.1. Research Method
Research for the project was done by researching existing systems. As there were not many or
any for the sport of javelin itself, the team looked at other sports technologies, such as Zepp
Tennis, a program to measure the speed of a tennis serve, or SparTag, a device measuring the
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power of the swing of a baseball bat. More in-depth research on components and filters was done
using various online and journal sources, especially through the Hekman Library.
3.4.2. Team Communication Method
The team’s main form of communication was through email, although other forms were used as
well. As the team all uses Android smartphones, the texting app WhatsApp was used for group
chats and quick messages. Weekly meetings and class times were also used to stay up to date,
hold each member accountable to their tasks, and overcoming obstacles or other team decisions.
For collaborative work, the team used both Google Drive and Microsoft One Drive in order to
allow multiple people to edit the same file or document.
3.4.3. Design Method
First, the team completed lots of research in the area of the project, specifically complementary
and Kalman filters, Attitude and Heading Reference Systems (AHRS), and several sports
technologies. This research included looking into different types of sensors and microprocessors.
After considering different design alternatives, the team focused on getting all the individual
parts of the system working separately. This included getting the angle of release from the
sensors, getting the velocity of throw from the sensors, communicating between a phone and
Bluetooth module, hardware design and casing, and portability and power requirements.
Finally, the last step was to integrate the different aspects of the project into a single working
prototype, as well create as a concept design for a final model given more time and resources.
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4. Requirements
For the main aspects of the design, the team set design criteria to guide the process. After
conferring with Bret Otte, Head Track & Field Coach at Calvin College, a number of constraints
were added to the criteria for the design of the system. These include physical requirements,
functional requirements, and performance requirements. Physical requirements encapsulate the
constraints of the device itself and the wear and tear it must withstand. Functional requirements
encapsulate how the device operates. Performance requirements encapsulate what can be
expected of the device.
Physical Requirements

The entire device including packaging or casing shall be no larger than 6 inches in length
with a diameter not more than 0.25 inches larger than the javelin it is attached to. This is
to make sure that the device does not alter the wind resistance of the javelin.

The device shall weigh less than 1 lb. This is to ensure that the center of gravity remains
the same so that the throw is not altered in any way by the device being attached to it.
The device shall be able to withstand shocks ranging from 10,000 G to 20,000 G (vibrations).
Javelins regularly experience shock within this range, and the device shall remain safely attached
and accurate throughout the lifespan.

The casing shall be able to withstand the elements (water resistant, mud and earth
resistant, snow resistant) to protect the electronics within. Track meets are rarely
cancelled and the athletes will compete in various weather conditions. The device shall be
able to last no matter the conditions an athlete will throw in.

The casing shall be easy to attach and detach from the javelin implements, as teams may
want to use it and each thrower tends to prefer different javelins, or possibly has their
own.
Functional Requirements

The final package shall contain the least collection of sensors necessary to obtain data
and output the useful information accurately, within 5% error.
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
Accuracy shall be maintained even with a high level of noise and interference from the
javelin vibrations and spiraling.

The sensors employed in the device shall remain true to calibration throughout the
lifespan of the device, even going through the shock of over 10,000 G.

A user that has the tech savviness for basic use of a smartphone shall be able to use and
understand the interface of the Android app. The user cannot waste brain power on using
the app, but is focused on improving their throwing.

The user interface shall use plain, non-technical language. The users will [most likely]
not be engineers, and shall still be able to understand everything easily.
Performance Requirements

The range of the communication from the device to the mobile device shall reach up to
100 m. Upper level athletes are able to throw the javelin nearly 100 m (world record
98.84 m), so the communication shall support this range.

The battery life of the device shall last at least 5 hours. This will get the athlete at least
through a week of throwing practice (assuming device is off while athlete is warming up
and lifting – throw for about an hour a day, 5 days a week).

Power source shall have low current requirements, for safety as well as to extend battery
life. Thus the current shall stay below 0.5 A or 500 mA.

The device shall transmit the data to the phone within a reasonable time. The athlete will
track the throw to its landing and then want to look at the data. Therefore, the information
shall be transmitted within 20 seconds of the release.
Deliverables for Team 15 CoachJav include:

Project Proposal and Feasibility Study

Final Report

Team Website

Prototype
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4.1.
Design Schedule
The work breakdown was done according to the schedule in Figure 3 below. In addition to the
Gantt Chart of Figure 3, the team utilized sticky notes with monthly end goals and tasks. These
sticky notes could easily be moved around if the task was finished early or required more time to
complete, and helped the team stay focused and aware of what was to come next.
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Figure 3: Work Breakdown Schedule
4.2.
System Architecture
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The requirements above were analyzed and a system was designed to meet the requirements.
This was done by breaking the system down and designing the individual aspects of the project
before integrating them back together into one device. An overview of the system flow is shown
in Figure 4 below. An overall block diagram is also shown in Figure 5 below.
Figure 4: System Flow Diagram
Figure 5: Block Diagram
4.3.
Design Norms
As students, the Calvin College mission statement has been ingrained in us over the past four
years, “to think deeply, to act justly, and to live wholeheartedly as Christ’s agents of renewal in
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the world.” From an engineering standpoint, the mission statement can be seen directly in the
Design Norms from the Senior Design class. Thinking deeply translates to caring and cultural
appropriateness; acting justly translates to transparency, integrity, justice, and trust; being an
agent of renewal translates to stewardship, and being Christ-like translates to all design norms,
especially humility. Of course, the team tried to follow all the Design Norms, but chose four
main ones to keep in mind throughout the whole design process over the past year of the project:
Trust, Cultural Appropriateness, Caring, and Integrity.
4.3.1. Trust
“Design should be trustworthy, dependable, reliable, and avoid conflicts of interest”
The system as designed would serve as a tool for providing feedback to the coach and the athlete.
There will be no trust if the system does not provide the accurate measurement it promises to
provide. Therefore, without trust as a design norm, the system would be useless to the coaches
and athletes and would not sell. Furthermore, the team wants to make sure that no consumers
have misconceptions about the device. It is only meant to be a tool to assist in the development
of athletes, and makes no guarantee that using the product will make you an amazing javelin
thrower. The sport of throwing javelin is grueling. It takes hard work and dedication, as with all
sports, to reach an exceptional level, but the device may make the technical aspects of the throw
easier to improve upon.
4.3.2. Cultural Appropriateness
“Design fits in with the general human socioeconomic order, alleviates human burdens, but
preserves what is good in the culture, and is guided by love, respect, and a value of diversity”
The sport of track & field has a culture all on its own, as one can perceive if they have attended a
track meet. Also, within that culture, the sport of throwing and specifically javelin throwing has
its own rules, standards, regulations, and norms. The system is not designed to change or infringe
on the existing culture that is the sport of track & field, but to respect the standards already in
place. The device also should provide measurements in the same units as are used in the sport
(metric system – meters).
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4.3.3. Caring
“Design shows genuine love and concern in the design group and in fabrication, shows due care
for persons, takes into account the effects on individuals (physically, socially, and
psychologically), and promotes loving caring relationships in use.”
As designers of the system, the goal that was set for the development of this system was to care
for the athlete. In designing a system that provides feedback of the actions of the athlete, we are
not only providing information, but the team believes the given information could be useful in
making the athlete better at the sport. Also, the team believes that as Christians, people should
“Do the best they can on a daily basis with what God gives them on that day” – Al Hoekstra
(Calvin Track Coach). The project, hopefully, helps the users to achieve their best in the javelin,
as they continue to do the best they can not only in sport, but in all areas of their life.
4.3.4. Integrity
“Design is complete, is harmonious of form and function, promotes human values and
relationships, and is pleasing and intuitive to use.”
This design norm deals a lot with the user interface, and means a lot to the user. The user can
take comfort in the fact that the device was designed with them and their experience while using
it in mind. As laid out in the Design Norm itself as well as in the design criteria created by the
team, the system must be intuitive, pleasing, and easy to use for anyone and everyone.
4.4.
Design Components and Alternatives
4.4.1. Sensors
After conferring with the client Coach Bret Otte of the Calvin College Track & Field team, there
are two pieces of desired information that coaches and athletes do not have easy access to
already: velocity of throw and angle of release. To capture this information, the team had to
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choose sensors that would get the data and be able to process it into the desired output
information.
Initially, the team considered using only an accelerometer. There are several different types of
accelerometers, so the team chose based on several factors, including size, vibration, shock, and
motion. The accelerometer for a javelin throw would have to withstand lots of vibration and
shock while still remaining accurate without re-calibration.
After initial testing the team determined the accelerometer by itself would not have been enough
for obtaining reliable data. The accelerometer is designed to be sensitive to gravity and therefore
could be affected by forces from multiple directions, leading to error in the results (up to 8 m/s
inaccuracy). Thus, instead of just an accelerometer, an inertial measurement unit (IMU) was used
capturing nine degrees of freedom. The Inertial Measurement Unit is integrated with an
accelerometer, gyroscope, and magnetometer. The combination of the sensors proved more
efficient, as each sensor relied on another to be able to give accurate results. As an example the
accelerometer used the data from the gyroscope to determine if the force acted on it was anything
other than a rotational force. The team eventually went with a combination of the gyroscope and
accelerometer data, using a Kalman filter. This was useful for capturing the angle of release.
However, after another round of testing, the IMU alone would not yield accurate results for the
velocity of throw. To capture this information, two sensors were considered: an air flow meter or
a GPS module. The air flow meter was determined to be too large for the product the team was
creating, so the GPS module was employed and added to the device. The GPS module captures
the velocity of the throw with accuracy, especially as the javelin throw event is conducted
outside. Additionally, to cut down on the GPS fix time (searching for satellites), a backup battery
for the GPS was added to the final product as well.
4.4.2. Microcontroller
For the microcontroller, there are two main options that are easy for development such as senior
design requires. The two most common sources of development boards are Raspberry Pi and
Arduino. They come standard with several options that make developing projects easy for the
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user, and Arduino has libraries of open source code used from other projects and from the
company engineers themselves. Because the team wanted to keep the device as small as possible
and the project did not require the processing power or memory of a Raspberry Pi, the team
chose to go with Arduino. However, even within the Arduino brand, there are multiple choices
for microprocessor development boards, such as an Arduino Mega, Arduino Uno, Arduino Nano,
Arduino Pro Mini, and more.
Arduino Uno
The Arduino Uno is the biggest and most powerful of the three boards considered for the
project. The team did purchase an Arduino Uno for initial development, but the board is
bigger than was necessary for the final device. However, the board was incredibly useful
to get initial setup and coding experience, as well as for easy testing with preliminary
steps.
Arduino Pro Mini
The team also purchased an Arduino Pro Mini because of the small size and low power
requirements, only needing 3V to run the ATmega 328 microprocessor and other
hardware. This board was used in preliminary designs for its miniature space, but due to
the necessary filtering of the data to get accurate results, the board did not have enough
memory and processing space to perform the required tasks.
Arduino Nano
The Arduino Nano is basically the Goldilocks for the CoachJav, as shown in the Decision
Matrix in Table 2 below. The size is smaller than the Arduino Uno, but has more memory
space than the Arduino Pro Mini without being too much larger in actual size. This
combination makes the Arduino Nano just right for CoachJav, as shown in Figure 6
below. The Nano also has multiple necessary pins already built into the board, such as i2c
ports and serial ports, as well as easy voltage regulations for simple wiring with the
sensors, batteries, and communication module.
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Figure 6: Arduino Size Comparison
Table 2. Decision Matrix for Arduino Microcontroller
Factors Weight Memory Size Voltage
Requirements Total 8 5 2 Arduino
Uno
2
1
2
Arduino
Nano
2
2
2
Arduino
Micro 1 3 3 25
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29 4.4.3. Power Source
There are infinite options for a power source to power the device. Because the device must be
portable, this leaves only batteries, but again there are multitudes of batteries including standard
batteries such as AAA or AA, rechargeable batteries such as Lithium Polymer (LiPo), or coin
cell batteries. The power source should give the device at least 5 hours of power (about a week
of daily practice).
Standard Battery (1.5v)
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Standard batteries are the best known and cheap. However, due to their low voltage, it
would take 4 of them to power the device. Also, they are not small, and as such would
not work well for the design of CoachJav.
LiPo Battery
Rechargeable and with high milliamp hours, the LiPo battery seems like an extremely
good option for CoachJav. However, the stability and necessity of plugging the device in
to recharge the battery brings safety concerns, and the size of a LiPo is not quite as good
as other options.
Coin Cell Battery
The coin cell battery is the smallest option, which makes it the best for the final design as
shown in the Decision Matrix in Table 3 below, as well as the 3.3 v output. There are a
few different sizes that the team tested – a 16 mm and a 20mm – just to make sure that
the device lasts as long as desired. The 20mm has more milliamp hours so it will last
longer than the 16mm coin cell, thus the final design contains the 20mm CR2032 battery,
while still remaining small enough to keep the device compact as shown in Figure 7
belowFigure 7. Battery Space within CoachJav Design.
Battery Space
Figure 7. Battery Space within CoachJav Design
Table 3. Decision Matrix For Battery Selection
Factors Weight Voltage 10 Standard Battery
(1.5V)
4
LiPo
Battery 8
Coin Cell
Battery
6
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Size Current Time Total 8 6 4
4
96
5
7
162 9
6
168
4.4.4. Data Communication
Ideally we would like our communication module to cover a range of 100m. The current world
record for javelin throw is 98.48m. Realistically, the team would like the package to
communicate data at least a third of the ideal range, which is a 30m radius. Given this radius, the
package will be able to gather data and transmit the data to the connected device quickly. This
range also optimizes power consumption from the data communication module. The team plans
to inform the user of the range of communication for more effective use of the tool.
Also considered in the choice of communication was the rate of data bit transmission and power
consumption. The bit rate determines how fast the information would be transmitted between the
communication module and the user interface. It also determines the frequency at which data is
transmitted between the communication module and the user interface. The rate of data
communication would be selected to provide results as soon as possible. In terms of power, the
team would like to implement a system with as low power consumption as possible to make the
device last longer without replacing the batteries. This was a significant consideration for the
team's choice of a data standard. That being said, some modules come with "sleep modes" that
reduce their overall power consumption. The team would like to employ the module with a high
power efficiency.
Several options already exist for wireless data communication, as follows:
Bluetooth Communication
Strengths of Bluetooth communication include versatility, and integration in most
existing devices including smartphones and audio devices. However, most Bluetooth
modules consume a high amounts of power in data communication. The range of data
communication can go up to a 100 m, although most only reach up to a range of about 10
m.
26
ZigBee Communication Protocol
The ZigBee module provides a low cost, bi-directional communication. However, it
communicates data at a low bit rate (250 Kbits/s). It covers a similar range to Bluetooth,
and goes even further in a mesh network. The down-side of ZigBee is that it comes in
pairs, a transmitter and a router for receiving; and therefore needs a medium for data
transmission, other than just a phone.
Wi-Fi Communication Protocol
Wi-Fi is one of the most common standards of communication. It relies heavily on
routers and access points and therefore limits its communication to the range of the base
network. Nevertheless, it is able to transmit a standard bit rate of 54 Mbit/s and an
average of 22 Mbits/s of data. However, it is also very bulky.
With the information gathered above, the team decided to use a decision matrix as shown in
Table 4 below to determine what data communication standard to adopt to transmit data between
the user interface and the javelin.
Table 4: Data Communication Decision Matrix
Size
Range
Power Consumption
Transmission Rate
Cost
Convenience
Weight
10
9
8
7
6
9
Totals
Bluetooth
3
1
2
2
2
3
108
WiFi
1
3
1
3
1
2
90
ZigBee
2
2
3
1
3
1
96
From the decision matrix in Table 4 above, Bluetooth was determined to be the ideal standard of
data communication for the project. However, most Bluetooth modules only operate up to ~10
m. Thus, the team chose to go with a higher-power Class I module, with a range of up to ~100 m,
a distance over the world record throw.
4.4.5. User Interface
In terms of the user interface, the team had the three options listed below:
27

Windows 10 mobile operating system

Android Operating system

iPhone Operating System (IOS)
Windows 10 mobile Operating System
Windows 10 is Microsoft's latest attempt to build an operating system that is both user
and developer friendly. The advantage of Windows 10 is that it allows easy
synchronization of developed applications between the mobile operating system, desktop
operating system and their gaming console the Xbox One (Considering the future of
Internet of Things (IoT) the gaming console might be useful in viewing and analyzing
data). It also allows easy porting of application programs from Android and IOS
operating systems with minimal modifications. These features of the Windows 10
operating system make it a suitable platform for application development. However, there
are not many mobile devices currently running on the Windows 10 mobile operating
system.
Android Operating System
The Android operating system provides a customizable base that is used by a large
percentage of the mobile device market. Most smartphone producing companies
manufacture their phones with a form of Android modification, which makes the
operating system the most used operating system currently. The operating system
currently boasts 82.8% market share.
Apple iPhone Operating System
Apple’s iPhone operating system provides a base of efficient app standards that
developers are required to follow. In 2015, the programming language, Swift, was
released, which promises more hands-on, easy, safe and interactivity for app developers.
This step from Apple is a sign that they look out for developers and are trying to make
development on the platform easier.
With the information gathered above, the team used a decision matrix shown in Table 5 below to
determine what user interface platform to adopt, and created an Android application.
28
Table 5: User Interface Decision Matrix
Entry Cost
Market Available
Customization
Experience
4.5.
Weight
10
9
8
7
Totals
Android
2
3
3
3
92
Apple IOS
1
2
1
2
50
Windows 10
3
1
2
1
62
Final Design
4.5.1. Prototype Components
For our final design the following components were employed as discussed in this report.

MPU6050 – This IMU (inertial measurement unit) was used as the accelerometer,
gyroscope sensor, to measure the angle of release of the javelin.

Adafruit’s GPS flora breakout – This GPS (global positioning system) module was used
to determine the velocity of the javelin.

Arduino Nano – Served as the microcontroller hosting the algorithms, power distribution
and communication among all components present.

Sparkfun’s Bluetooth Mate Gold – Used as the Bluetooth server for communication
between the microcontroller and the app on the phone, with a range up to 100 m.

CR2032 Coin Cell Batteries – small but used to power the microcontroller, GPS,
Bluetooth, and IMU.

3D Printed Casing – houses the components, attaches them to the javelin rigidly, and
protects them from the elements and shock.
A diagram of the components used and the connections between them is shown in Figure 8
below.
29
Arduino
Nano
Bluetooth
GPS
IMU
Coin Cell
battery
Figure 8. Component Assembly for CoachJav
The CoachJav prototype was designed with a minimalist intent. It was designed with the intent to
be inconspicuous while being strong enough and big enough to contain the components to be
used for measuring the velocity and angle factors.
The weight of our final prototype was measured at 92 g or 0.20 lbs with all the components but
the battery in place. The weight of CR2032 batteries also referred to as the coin cell batteries in
this report have a varying weight of 2.8 g to 3.9 g or 0.0062 lbs to 0.0086 lbs. Altogether, the
prototype weighed from 94.8 g to 95.9 g (0.206 lbs to 0.209 lbs) depending on the battery
weight.
Figure 9 below shows the 3D model modelled with solid works and Figure 10 below shows the
outcome of the model, printed with High Impact Polystyrene (HIPS) and coated with fiberglass
resin for reinforcement. HIPS has a flexural strength of 4620 psi and an impact strength of 2.20
ft-lb/in [1]. However, a two-pound javelin has kinetic energy of 167 ft-lbs after traveling at a
velocity of 73.5 fps [2]. The fiberglass resin added an extra 20 ft-lb/in to the model thus making
an overall impact strength of 22.20 ft-lb/in. Considering the six inch length of the prototype, the
impact strength of the package was 133.2 ft-lb. The package was able to impact 5 throws of the
Javelin, flying at an average speed of 33 mph.
30
Figure 9. 3D model of Final Prototype of CoachJav
Figure 10. CoachJav Final Prototype
31
An assembly drawing of the model has been attached in the Appendix 10.1 to show further
design constraints. This assembly attaches to the javelin as shown in Figure 11 below, to keep
the center of gravity nearly the same, as well as limit wind resistance of the device.
Figure 11: Concept Design Fit to Javelin
4.5.2 The CoachJav App
Based on the results of the decision matrix, the team decided to develop the user interface and
display using the Android SDK (Android studio). The team decided that the most efficient way
to tackle this design, was in two parts. The first part, was to be able to scan for, and pairing with
Bluetooth devices (Specifically the Sparkfun’s Bluetooth Mate Gold connected to our
prototype); the second part involved opening a Bluetooth connection between the prototype and
the user’s device, transferring data across this connection and displaying this data to the user.
The Android app is divided into two pages based on the two aforementioned sections of the
application design, the main activity page (activity_main.xml) and the data display page
(display.xml).
The main activity page is the first page that the user gets to on running the app CoachJav app.
This page includes buttons to disable/enable the user devices, scan for Bluetooth devices,
pair/unpair with Bluetooth devices and navigate to the data display page. The two key libraries
that were used for the Bluetooth scanning and Pairing were android.bluetooth.BluetoothAdapter
and android.bluetooth.BluetoothDevice. Figure 12 below shows the layout of the
activity_main.xml as it was designed in Android Studio.
32
Figure 12: Layout of Main Activity Android App
The display page is accessed from the main activity page. On this page, a Bluetooth socket
connection is opened between the user's device and the Bluetooth module on the CoachJav
prototype. The values of the speed and angle are then displayed on this page. The one other
feature present on this page is the clear button, which clears the most recent data and allows new
data be retrieved. The key additional library used for this page's functionality is
android.bluetooth.socket. Figure 13 below shows the layout of the display.xml in Android
Studio.
Figure 13: Layout of Display.xml
The functionality of the application was written in the Java programming language. This activity
was divided into three files, MainActivity.java, DeviceListAdapter.java, and
33
DisplayActivity.java. The MainActivity.java creates the activity_display.xml page and controls
the functions of the buttons on this page, DeviceListAdapter.java controls the scanning and
pairing functionalities, and DisplayActivity.java creates the display.xml page and controls the
clear button function.
This app was able to retrieve speed and angle data from the sensors on the CoachJav prototype
and display them. Figure 14 below shows a sample data reading that may was received by the
android application.
Figure 14: Speed and Angle in Android App
34
5. Business Plan
5.1.
Company Description
The name of the establishment is JavTools, based on the product currently offered to clients
(CoachJav). This also leaves the possibility to expand further into javelin equipment or other
services related to javelin throwing.
5.1.1. Team
The team working at the company currently consists of the following positions:
President
Head of the company and top of the decision making chain. The president is supported by a team
of three executives, the VP of hardware development, the VP of software development and the
Chief Financial Officer. The president is in the person of HRH. Dr. Rev. John Eric Kwamena
Mugabe.
VP of Hardware Development
Leads a team of two other hardware engineers in developing hardware components and
specifications that contribute to building the product CoachJav. The VP of hardware is Mr.
David Dadzie.
VP of Software Development
Leads a team of two other software developing engineers to design a brain for all the connected
hardware and also supports the company in providing a Graphical User Interface (GUI) for the
system on a mobile phone platform. The VP of software is in the person of Mr. Landon Potts.
VP of Marketing
Leads the marketing and sales teams to get the product out to people and bring in revenue. All
the engineering in the world will not make money without people to sell it, and without people
buying it. The VP of marketing is Mr. Frank Bower.
35
Chief Financial Officer
As a key part of the management team, the CFO organizes the organization’s monetary affairs
and also leads the marketing team in product advertisement and sales. This person is also in
charge of the ergonomics of the product and how it appeals to consumers and also leads a team
of two individuals. The CFO is in the person of Mr. Ofiliojo Ichaba.
5.1.2. Board of Directors and Advisors
The company has a board with four members.
The chairman of the board is Mr. Jeremy Van Antwerp and his subsidiaries are Mr. Mark
Michmerhuizen, Mr. Ned Nielsen, and Mr. Bob Masselink.
The company also has a legal attorney in the person of Ms. Delali Zormelo and the following
advisors:




Accountant – Mr. Frederick Ankomah
Insurance Agent – Ms. Mea Zuiderveen of Adoptive Insurance Company
Banker – Mr. Sesugh Ubwa of Northwestern Bank
Consultant – Eric Walstra of Gentex, Inc.
Mentors and Key Advisors at JavTools include:



Mr. Mark Michmerhuizen
Mr. Randall Brouwer
Mr. Yoon Kim
5.1.3. Company Structure
The company currently operates under the structure shown in Figure 15 below.
36
President/CEO
John Mugabe
Hardware Software David Dadzie
Landon Potts
Sales and Marketing Ofiliojo Ichaba
Kwesi Asare
Carol Anderson
Joseph Kelley
Laura Clifton
Harry Kane
Mary Abigail "Abby" Wambach
Figure 15: Company Structure
5.2.
Operations
The company currently operates as a partnership, as it is currently a small business composed of
nine individuals. The company operates on an internal source of income and has not interacted
with the market at any level. Since the company’s products have not been released to the public
yet, we do not expect any lawsuits. Moving on, the company would be transformed into a
Limited Liability Company (LLC), as it would be receiving loans for operation. As an LLC the
company would be equipped to protect all employees present and future from any lawsuits. The
company would also be able to separate individual assets from the company’s assets as an LLC.
In case of foreclosure, the company would be sold as an LLC instead of a partnership.
5.3.
Financial Statements
To analyze the feasibility of the company, the following financial statements were analyzed,
forecasted over the next three years. They are:
Income Statement
37
The income statement table in Appendix 10.4.1 shows the Company’s statement of income. The
statement shows cost and sales revenue for a forecast of the first three years of operation. The net
income after tax is also calculated in the table. From the forecast it can be realized that the
company will make a net income of about $160,000.00. This amount could be used to pay off
some of the debt and structure expansion within the company. Subsequent years show an income
of about $560,000.00 and $855,000, which would be used to clear the debt completely and boost
marketing of the product, along with incorporating other products like CoachJav for other sports.
Cash Flow Statement
A table showing a statement of cash flow for the first three years is attached in Appendix 10.4.2.
From the table, it is shown that the company ends with a positive cash balance. The cash flow
diagram also shows the invested capital, the borrowed funds. There are no changes in assets and
liabilities other than the cash, notes payable and equipment thus reemphasizing the exclusion of a
balance sheet.
5.4.
SWOT Analysis
5.4.1. Strengths
The main strength of the company is that the product is unique and has a low cost to the
consumer. There is no product on the market currently like it, nevertheless there’s a release of a
similar system for baseball bats, but not for javelin. Other products that do similar data collection
use expensive equipment, operate in controlled situations and mostly require video technology.
The product will also be high quality and easy to use, allowing it to be recommended by the
users to new clients that would not otherwise be reached.
5.4.2. Weaknesses
The main weakness of the company is that it is a new startup and thus has no branding or public
image yet. This will lead to the company needing aggressive marketing, which takes money and
capital that the company does not have easy access to, again because it is a new startup company.
5.4.3. Opportunities
38
There are several possible opportunities for the company.
First, the company name could spread at track meets and events, especially among the coaches
and athletes. This gets the company name out quickly without too much marketing cost. With
expansion, many teams including high school, college, or even national teams would want to buy
the product and use it to improve their skills.
Second, the technology could figuratively be applied to other events in the sport, especially other
throws like hammer and shot put, but also long jump or high jump. Then the product could be
enhanced or new products developed to incorporate these events as well. Finally, the technology
could be expanded outside of the sport to other applications. This could include other launched
things, such as missiles, footballs, or other projectiles.
Utilizing the technology in all these areas, provides the opportunity for the team to aggressively
pursue a patent. This will also help subdue competition and threats from other startups that will
try to exploit the field.
5.4.4. Threats
The main threat to the company is competition. If another company with an already established
customer base designs a similar product, this creates competition in the market. Especially if that
company is much larger and more established, the competition would set the company back and
it would be hard to vie for our place in the market. The startup with the baseball bat could
expand into other sports including Javelin, which could create competition for our product.
However, the company could get protective patents and attempt to enforce them, although this
would involve serious legal fees which the company may not have sufficient budget to follow
through on.
5.5.
Marketing
5.5.1. Target Market
JavTools’ target market as mentioned before would be high school and college javelin throwers
as well as professional throwers and coaches.
39
5.5.2. Demographic Profile
JavTools’ market demographic profile includes coaches, trainers, and different levels of athletes.
Coaches and athletic trainers will experience the most gain from CoachJav since they will have
the ability to make real time adjustments during their sessions. Since CoachJav is able to display
results of javelin throwing mechanics, athletes will have direct benefit from the system.
5.5.3. Other significant customer characteristics
JavTools seeks customers who are very skilled in the art of javelin throwing and also those who
display very good potential to throw long distances. The company sees these as significant
customer characteristics because CoachJav will be well advertised if the company has these
types of customers.
5.5.4. Desired Image in Market
JavTools wants to create products and provide services that are trustworthy and reliable to create
a loyal customer base that will not only maintain a relationship with JavTools but will also
promote the company’s products.
5.5.5. Market Size and Trends
Market Size
The CoachJav product would target a niche market. Nevertheless, there is a potential for the
product to be internationally recognized, thus providing a colossal customer base for the product.
Rate of Growth
Since the introduction of CoachJav and any similar product to markets around the world would
be revolutionary, it difficult to know what the current and expected growth rate is. However,
given the increasing competitive nature of sports around the globe, JavTools is confident that
there would be a large rise in the number of customer within the first 3-5 years after initial
introduction.
40
5.5.6. Advertising and Promotion
Message
JavTools wishes to deliver a strong message, which is its vision and mission. JavTools wants to
be acknowledged for its innovation using cutting edge technology to revolutionize the sport of
javelin throwing. We want to let our customers know that they can trust our products and that
they are always reliable.
Media
JavTools look to incorporate social media ads and short video commercials geared towards
improving performance of young athletes. These media will convey enough information to make
a case to coaches and professional athletes.
Budget
JavTools will be on minimal amounts of cash in the first few years. In light of this the company
anticipated implementing most of its advertisement through its website and well-placed sports
magazines. Increase in company revenue will certainly contribute to an increase in marketing
and sales incentives.
Plans for generating Publicity
Demonstrating the products at major sports outlets and at different high schools and college will
be a major approach to increase publicity. When the company generates more revenue, using
prominent sports figures to advertise our products will be an option to be considered. JavTools
also plans on providing javelin training seminars for track and field programs across the USA
and Europe to encourage young athletes to use CoachJav in their training.
5.5.7. Pricing
*See Appendix 10.4.3 for cost of CoachJav.
To cover the costs of running the business and to still be profitable, as well as the current market
price following the market study above, CoachJav should sell for $849.
41
Comparison against competitors’ Prices
JavTools does not have any direct competitors in terms of other companies producing the same
or similar product that we have for this sport. However, since the company seek to create its
product efficiently and at a low cost our products will be more favorable to customers than that
of other companies within the market.
Discount Policy
As a small startup company, JavTools will not be offering any discounts to its customers. This
decision is subject to change and will be readdressed after a few years once the company has
experienced considerable growth.
Gross Profit Margin Per Anticipated
JavTools is anticipating a gross profit margin of 28% by the end of year three with 99% of all
debts paid off. This number is reasonable given that the company currently has no credible
competitors.
5.5.8. Distribution Strategy
Distribution could be accomplished to the general public through all-purpose sporting goods
stores such as MC Sports and Dick’s Sporting Goods in the USA. Further distribution could also
be achieved through USATF (USA Track & Field) as well as international athletic goods stores
worldwide, and through a company website capable of taking orders.
42
6. Testing
Testing was intended to verify and point out any potential shortcomings in the design in
comparison to the design specifications mentioned above. To view an explanation of the testing
procedures performed, setup, results, and analysis, please see the content herein.
6.1.
Apparatus
In order to test our prototype we needed to develop a consistent and repeatable method with
known parameters. Our testing apparatus was a slingshot. The slingshot was constructed out of
wood, a PVC plastic pipe, and spear gun rubber. The device was 10 feet long and about 4.5 feet
wide. The plastic pipe was used a guide for the shaft of the javelin and also a mounting slot when
the slingshot was cocked.
In addition, the team also built a support stand for the launching apparatus. The stand was
constructed out of wood and allows the slingshot to be placed in variable positions which alters
the angle at which we launch the javelin. The slingshot, support stand and the setup are
illustrated below in Figure 16: Slingshot Crossbow Javelin Launching Apparatus for Testing. To
perform a single test, we used a radar gun to capture the release velocity of the javelin by the
slingshot.
Figure 16: Slingshot Crossbow Javelin Launching Apparatus for Testing
43
6.2.
Method
The following parameters were tested to verify and identify the performance and potential
shortcomings of CoachJav. The following parameters were tested:
1. The ability of CoachJav to withstand shock
2. The accuracy of velocity and angle readings from CoachJav.
To test the ability of CoachJav to withstand test, CoachJav was assembled unto a cylindrical pole
and thrown across Calvin College’s throwing field repeatedly. CoachJav was recovered
structurally sound though aesthetically marred. It was then painted to restore its aesthetic
qualities. Figure 17. CoachJav after shock-resistance testing shows the setup used for this test.
Figure 17. CoachJav after shock-resistance testing
For testing the team employed the use of the javelin launcher built by the team. This allowed the
team to test the two pieces of data captured by the device, angle of release and velocity of throw.
To test for accuracy in velocity measurements, the team set up a javelin launcher to help make
the process repeatable. To aid in testing the accuracy of the velocity, the team used a speed gun
to check the speed at which the javelin was shot out of the launcher and the speed recorded by
CoachJav.
44
To test for the angle of release, the team assigned fixed angles on the side of the launcher and
checked the angle calculated by CoachJav upon release, as well as checking the results by
comparing to a video of the throw itself, and measuring the angle with a protractor.
Following the testing of the data itself, more testing was done concerning the battery life of the
device. The requirements state that the battery life shall be 5 hours to last at least a week’s worth
of practice. However, when tested, the device draws a lot of power, especially when the GPS is
searching for satellites. The device with two coin cell batteries only lasted ~90 min, much shorter
than the desired 5 hours. As laid out in Future Work, the PCB design should also make the board
last longer, but the team does not anticipate that a simple PCB with a few less components could
add 3.5 more hours to the battery life. New, different, and better power sources will need to be
looked into to bring the product to market, or lower powered sensors and microcontroller.
6.3.
Results
6.3.1. Angle of Release
After testing, it was determined that the CoachJav device works well, but not quite as well as the
team initially hoped. The angle of release is more accurate than the GPS, with a standard
deviation of 1.6° (standard error of 3.9%), as shown in Figure 18 below. The standard deviation
for the 30° throws was 1.5° (5% error), 45° throws was 2.2° (4.9% error), and 60° throws was
1.1° (1.8% error).
45
Testing Coach Jav Angles
Angles Tested at 30, 45, 60 degrees
70
60
50
40
30
20
10
0
0
5
10
15
20
25
30
Number of Tries
Measured Angle
CoachJav Angles
Figure 18: Angle of Release Testing Results
6.3.2. Velocity
The GPS is slightly worse, with a standard deviation of 1.8 m/s (standard error of 6%), as shown
in Figure 19 below. The team attributes this error to the altitude change in the flight of the javelin
not being detected by the GPS module, only the horizontal motion being able to be detected from
the satellites far above earth. (The GPS does detect altitude, but not well, and not within the
timespan of a single throw. GPS systems extend their data processing throughout a longer
duration of time, usually a long drive or run for minutes at a time, as opposed to a seven-second
throw to capture all the data.)
46
Testing Speed with Radar Gun and Velocity
45
40
Speed (mph)
35
30
25
20
15
10
5
0
‐5
0
5
10
15
20
25
30
35
Number of Trials
Measured Velocity
GPS Speed
Figure 19: Velocity Testing Results
47
7. Future Work
Obviously, as everyone always thinks at the end of the Senior Design class, the team
wishes they had more time and more budget. The team would attempt to use more time to make
improvements on the device. This includes making a full PCB (printed circuit board) design to
make the device smaller and easier to charge or replace the battery(s). Also, with more time, the
team would look into better power sources to make the device last longer, or perhaps with less
components (on the PCB) the device could last longer on the same power source currently used
(CR2032 coin cell batteries). Another thing the team would want to improve upon is the
accuracy of the velocity reading, perhaps using more or better sensors, or using trigonometry or
filters to get better data. Finally, for the casing, the team would invest a little more money into
better material (such as carbon fiber) to withstand more without breaking, and surrounding the
PCB with silicone or rubber to withstand higher shock.
48
8. Conclusion
Based on the success of the project in creating a simple first prototype, Team 15 believes that the
sport of javelin could move towards the use of more statistics. Although the javelin isn't as
popular of a sport, especially in the USA, every sport is advertising more stats. Football in the
NFL now advertises that players wear sensors and stats can be shown live about their speed,
distance, and more. As more and more sports incorporate this type of data collection, the javelin
throw can also be put into the mix. Not only do the fans of the sport want to see their stats, but
the coaches and athletes can use them to try to improve. The CoachJav device can fill the niche
in the market as the need arises for this data, especially if the Future Work in the section above
could be completed with more time, budget, and manpower. CoachJav could very conceivably be
a product and could translate into a successful business, with the opportunity of expansion into
the other sports that have this need.
49
9. Acknowledgements
Team #15 would like to thank especially Calvin Track & Field head coach Bret Otte and
engineering mentor Eric Walstra. Team 15 would also like to thank everyone else that provided
support with time, knowledge, or guidance in the design of CoachJav, especially Calvin
professors Mark Michmerhuizen and Yoon Kim. Your assistance and expertise was integral to
the success of the project. Thank you!
50
10. Appendix
10.1.
Assembly Drawing of Prototype
Figure 20: Assembly Drawing of Prototype
51
10.2.
Obtaining Angles through Kalman Filter
Steps in finding Angles from MPU6050 Using the Kalman Filter [3]
1. Predict the current state and the error covariance matrix at time k, of the system based on
the previous state and the gyro measurement.
2. Estimate the priori error covariance matrix based on the previous error covariance matrix.
The error covariance is used to determine how much you can trust the data from the
sensors.
3. Calculate the difference between your accelerometer measurement and the priori state.
Map a priori state with the measurement from the accelerometer in an observed space. If
you get a small number you can trust the data otherwise you cannot.
4. Calculate the Kalman gain.
5. Correct the estimate of the priori state (measurement between your previous state and the
gyro measurement) with the accelerometer measurement.
6. Update the Posteriori error covariance matrix.
52
10.3.
Test Data
10.3.1.
Testing Angle Data
Table 6: Testing Angle Data
Trials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Testing the Accuracy of the angles on CoachJav Measured Angle CoachJav Angle 30 31
30 28
30 28
30 28
30 29
30 30
30 31
30 31
30 30
30 32
45 45
45 44
45 44
45 43
45 44
45 47
45 39
45 45
45 46
45 46
60 60
60 60
60 60
60 61
60 63
60 62
60 61
60 60
60 60
60 60
53
10.3.2.
Testing Velocity Data
Table 7: Testing Velocity Data
Testing Velocity
Trials Measured Velocity
GPS Speed
1 33
35
2 34
31
3 39
39
4 36
35
5 32
33
6 40
40
7 35
34
8 41
42
9 28
29
10 40
37
11 32
30
12 35
32
13 39
40
14 33
36
15 33
31
16 35
34
17 34
34
18 41
40
19 39
38
20 41
40
21 38
41
22 36
38
23 40
42
24 33
31
25 32
31
26 33
30
27 35
32
28 33
30
29 36
32
30 33
35
54
10.4.
Financial Statements
10.4.1.
Income Statement
Table 8: Income Statement
JavTools
Pro-Forma Statement of Income
Year 1
10.4.2.
Year 2
Year 3
Sales revenue
4,245,000 6,367,500 8,277,750
Variable Cost of Goods Sold
2,945,591 4,418,387 5,742,500
Fixed Cost of Goods Sold
290,000
148,800
178,080
Depreciation
28,580
56,125
57,228
Gross Margin
980,829
1,744,188 2,299,942
Variable Operating Costs
39,323
58,984
76,660
Fixed Operating Costs
661,440
720,440
785,340
Operating Income
280,066
964,764
1,437,942
Interest Expense
10,000
17,500
12,250
Income Before Tax
270,066
947,264
1,425,692
Income tax (40%)
108,027
378,906
570,277
Net Income After Tax
162,040
568,359
855,415
Cash Flow Statement
Table 9: Cash Flow Statement
JavTools
Pro-Forma Statement of Cash
Flows
55
Year 1
Year 2
Year 3
Beginning Cash Balance
-
290,620
815,103
Net Income After Tax
162,040
568,359
855,415
Depreciation expense
28,580
56,125
57,228
Invested Capital (Equity)
100,000
-
-
Increase (decrease) in
borrowed funds
200,000
(50,000)
(55,000)
Equipment Purchases
(200,000)
(50,000)
(70,000)
Ending Cash Balance
290,620
815,103
1,602,746
10.4.3.
Cost Analysis
Variable Cost of Goods Sold:
Raw Material = $546.49/unit
Direct Labor = $8.15/hour (0.5 hours/unit)
Utilities (Electricity, Water & Gas) = $21/hour (0.5 hours/unit)
Total per Unit = $561.065/unit
Selling Price of Javelin = $849
56