Digital Competitive Precision Projectile Table Support Structure

Digital Competitive Precision
Projectile Table Support
Structure
Christian Braun, Rashon Hogan, Jelani Jackson,
Donald Thomson
University of Central Florida, College of
Engineering and Computer Science, Orlando,
Florida, 32816, U.S.A.
Abstract — The mixture of a college student’s past time
and technology brings the Digital Competitive Precision
Projectile Table Support Structure (DCPPTSS). Beer pong
has been seen popping up around college campuses in the
United States sometime around the 1950s and 1960s. The
game of beer pong has received a technological upgrade
which allows for players to continue enjoying the game while
possibly being slightly inebriated. These upgrades range from
ball detection, current player indicator, score keeping, game
correction in case foul play is involved, and a ball washer to
handle possible bacteria.
Index Terms — Beer pong, capacitive touch, digital
integrated circuit, diode lasers, inter-integrated circuit,
microcontroller.
I. INTRODUCTION
From the time of its inception, beer pong has become
the college student’s game of choice. A break from the
rigors of studying, term papers, and exams, beer pong has
become a way where people get together in a social
environment have fun playing a game. It is a little more
active than playing a game of cards, but much skill is not
required. The only skill one needs to play beer pong is the
skill of precision. Beer pong is usually played with two
teams with two players per team. Each team begins the
game by standing at the ends of the table behind their cup
setup called a rack. A rack is the number of cups, which in
the beginning ranges from 6 to 12 cups, in a geometric
shape, and each team throws ping pong balls into the
opponent’s cups until none are remaining. The initial
layout of the table and its components at the beginning of a
game are illustrated in Fig. 1.
There are many rules for the game of beer pong, but
for the purpose of the Digital Competitive Precision
Projectile Table Support Structure (DCPPTSS), the rules
have been limited to each team having two throws
maximum until a team no longer has cups remaining. The
Digital Competitive Precision Projectile Table Support
Structure (DCPPTSS) consists of sub-systems that will
automate tasks of beer pong such that the user need not do
anything but simply play.
Fig. 1: Layout and dimensions of the Digital Competitive
Precision Projectile Table Support Structure. Red circles indicate
cups in the Rack. Blue circles indicate wash cups.
The game starts with teams selecting a color which is
controlled by the capacitive touch sensor. The first team to
select a color will start the game first. The color selection
is then received by the central control unit and transmitted
to the user interface. Information is also transmitted to the
LEDs to indicate the current team’s turn. Each team is then
allowed to throw two balls per turn. Once a ball is thrown
in the field of play, the discretizing laser array sends data
to the central control unit that there was a make or a miss.
The central control then receives data from the capacitive

touch sensor that confirms or denies the reading from the
discretizing laser array, based on whether or not a cup is
removed from the table. If a ball is thrown, and misses the
table, the user inputs a miss via the user interface. Once all
the cups on one side of the table have been removed from
play, the opposing team is determined to be the winner of
the game.
II. SYSTEM COMPONENTS
The Digital Competitive Precision Projectile Table
Support Structure (DCPPTSS) is comprised of various
components which allow the user to focus less on
remembering the specifics of the game and more on
playing the game itself.
A. Central Control
The system that will control majority of the systems
used in the Digital Competitive Precision Projectile Table
Support Structure is a MSP430G2553 microcontroller. As
the central control unit, the MSP430G2553
microcontroller is responsible handling data that is sent to
and received by the surrounding sub-systems. The subsystems
the MSP430G2553 microcontroller communicates
with that have a direct connection to the functions of the
gameplay are the discretizing laser array, user interface
and the capacitive touch sub-systems. The MSP430G2553
microcontroller is also be responsible for the reduction in
power consumption, keeping score of the game, keeping
track of the number of throws remaining per turn,
changing LED location once player turn is over, as well as
the number of cups remaining on the table for each player.
MSP430G2553 microcontroller needs a way to
communicate that data, both input and output. When
communicating that data between a sub-system such as the
discretizing laser array and the capacitive touch subsystems
it is best to have a communication method where
there is an order in terms of priority. The priority being the
MSP430G2553 microcontroller has the highest priority
while the sub-systems follow. This method of
communication is necessary due to the fact that the
MSP430G2553 microcontroller is the central control unit.
If a sub-system were to have higher priority over the
MSP430G2553 microcontroller then the MSP430G2553
would in fact not be the center of control. The
MSP430G2553 microcontroller will need full control over
the sub-systems. The central control will implement a
master-slave communication system in which Inter-
Integrated Circuit (I 2 C) provides. Another part of the
Digital Competitive Precision Projectile Table Support
Structure is the communication between the
MSP430G2553 microcontroller and the discretizing laser
array sub-system. The discretizing laser array system,
when not in sleep mode, will buffer to wait for a projectile,
the ball, to enter its laser field. Once the projectile enters
the field the MSP430G2553 microcontroller will be
interrupted by the discretizing laser array sub-system. If a
projectile enters the discretizing laser array field and it is
not over one of the cups, a miss is generated. This
generated miss will be sent to the MSP430G2553
microcontroller which will in turn be sent to the user
interface module for display on the LCD. If a projectile
enters the discretizing laser array field over the opening of
one of the cups, a hit will be generated. This generated hit
will be sent to the MSP430G2553 microcontroller which
in turn will be sent to the user interface module for display
on the LCD.
Communication between the MSP430G2553
microcontroller and the capacitive touch sub-system are
another part of the Digital Competitive Precision
Projectile Table Support Structure. The capacitive touch
sub-system, when not in sleep mode, will buffer to wait for
a change in capacitance. This change in capacitance will
not occur from a projectile entering a cup, but from the
removal of a cup from the DCPPTSS surface. The
MSP430G2553 microcontroller will then receive an
interrupt from the capacitive touch sensor when there has
been a change in capacitance from the reference which is
taken at the beginning of the game. Once the
MSP430G2553 microcontroller receives the information
from the capacitive touch system, the MSP430G2553
microcontroller will send a request to the corresponding
capacitive touch sensor to turn off the LEDs for the
duration of the game. The results of the remaining
capacitive touch sensors will then be sent to the user
interface as the cups remaining.
When it comes to keeping score of the game the
MSP430G2553 microcontroller will not use an external
system for this task, however, another system will display
all the information. The MSP430G2553 microcontroller
itself will keep track of the score. The functions of the
table will be programmed onto the MSP430G2553
microcontroller in the C programming language. The score
for each player will be stored in the variables ScoreA and
ScoreB for the player(s) of player side A and player side
B, respectively. Both of these variables will be initialized
to zero at the beginning of each game. A player’s score
increases by one with each ball that is made. This
increment in score occurs only when the capacitive touch
system senses a change in capacitance for the
corresponding cup. The score variables will be contained
within a scoring function. The scoring function will be
contained within an if statement and called only if the
discretizing laser array system has detected a ball and the

capacitive touch system has received the reading of the
ball’s location.
Keeping track of the number of throws per turn per
player is also an important aspect of the MSP430G2553
microcontroller. This function also will not use an external
system to handle its processes. The function that keeps
track of the number of throws each player(s) has during
their turn will be programmed onto the MSP430G2553
microcontroller in the C programming language. The
variables num_of_throwsA and num_of_throwsB will be
used to store the number of throws remaining for player
side A and player side B, respectively. Both of these
variables will be placed in the game program that will be
used to run the beer pong functions from the
MSP430G2553 microcontroller. Each variable will be
used within separate for loops. The for loop will initialize
the number of throws to two and will decrement by 1 for
each iteration, throw. As long as the number of throws is
greater than zero, the player(s) will continue to throw a
ball. The for loop will buffer until the discretizing laser
array system gets a reading on a ball that was thrown. In
the event that a player completely misses the infrared
detection area a menu option will be available for a user to
manually decrement the number of throws for a particular
player (the MISS function in the user interface).
An added feature to the Digital Competitive Precision
Projectile Table Support Structure is LEDs moving in a
snake pattern. The snake motion begins as soon as the
Digital Competitive Precision Projectile Table Support
Structure is turned on. The initial route of the snake
motion is around the entire table. This snake motion will
continue until a user selects which player will start first.
Once the user selects which player will start first, the snake
motion of the LEDs will then move to the area of that
player and continue to perform the snake motion in that
area during the duration of their turn. When the number of
throws for that particular player reaches zero, the LEDs
will then move to the opposition’s side and perform the
snake motion in that area during the duration of that
player’s turn. The snake motion will continue back and
forth until the number of cups for a given player area has
reached zero. At that time the LEDs will continuously
pulse on the player side of the victor.
The task of keeping track of the cups remaining on the
table for both players will not be handed by a sub-system.
The MSP430G2553 microcontroller will be in charge of
keeping track of the number of cups remaining on the table
for both players. The number of cups remaining for each
player will be stored in the variables cups_remainingA and
cups_remainingB which are used for the player(s) on
player side A and player side B, respectively. These
variables will be initialized to six at the beginning of the
game. The game of beer pong will continue as long as the
cups remaining on both player side A and player side B
are greater than zero. The variables cups_remainingA and
cups_remainingB will be used within the remove cup
function. The remove cup function will be called when the
capacitive touch system senses a change in capacitance
from one of the cups. Once the capacitance has been read
from the corresponding cup the appropriate
cups_remaining variable will be decreased by one.
B. User Interface
The User Interface of the DCPPTSS refers to the digital
components with which the players of a game of Beer
Pong will directly interact. The user interface consists of a
single module containing a standalone MSP430G2553, a
16 line by 2 character LCD display (NHD-0216K3Z-FL-
GBW with built-in PIC16F690 to handle the display of
ASCII characters on the screen)[2], and three lighted
buttons used to navigate the user interface. The
components that make up the user interface are laid out as
shown in Fig. 2, and mounted to a wooden face plate. The
16x2 LCD runs off of a 5v power source, while the
MSP430G2553 runs off a 3.3v power source. The
MSP430G2553 sets the output of the display using the
RS232 protocol. Each time players interact with the table
using the user interface, they will affect the flow of the
game. They do this by using the three given buttons to
navigate a menu shown on the display.
i. Menu
Menus will be displayed on the 16x2 LCD. When the
table is first powered on (or at the beginning of a new
game), players will be able to choose which team goes first
by pushing either the left or the right button. The left
button corresponds to the team on the left side of the table
relative to the position of the user interface module. This is
also referred to as player side A by the central control unit.
Once one team is chosen, the LCD then changes to show
the information for the chosen team. The information
displayed includes the game status (Team Number, Cups
Left, and Reracks Left) for the current team. When the
middle button is pressed, the LCD then changes again to
display the four functions that the table will not be able to
handle automatically (i.e. by the other systems). These
functions include Miss, Skip Turn, Forfeit, and Rerack.
These functions are selected by the left and right buttons,
and selected with the middle button. When selected, the
display asks for confirmation from the players by either
pressing the left (for NO) or right (for YES) button. Once
confirmed, the function activates for the current team of
players. The results of these functions are read by the

central control unit through the I2C bus. The display then
returns to display the game status for the current team.
When the turn changes to the other team (when the
current team is out of Throws), the display will then switch
to display the game status for new current team. When a
game ends, the display will once again ask for the team
which goes first, and the Team Number (of the losing
team) will be increased appropriately to allow the winning
team to continue playing on their side of the table and
keep their specific team number. Also, when the central
control unit sends a full reset signal via the I2C bus, the
user interface will be overridden, resetting the cups left,
reracks left, throws left, and even the team numbers.
Fig. 2: This is the layout of the User Interface module. This
module has three arcade game-style light-up buttons and a backlit
16x2 LCD. It is located in the middle of the table, attached to
the side.
ii. Hardware
The three navigation buttons each have a 3.3v white
LED running at 15mA (using a 220 Ohm resistor),
connected to the same power line as the MSP430G2553
such that the LEDs will designate that the MSP430G2553
has power. The buttons each have a single switch
connected to ground as part of their own RC circuit (with a
time constant of 0.033ms: R=33kOhms, C=1uF) to
provide debouncing for the switches. The output of the RC
switch circuits are attached to the MSP430G2553 at pins
1.3, 1.4, and 1.5, which are all inputs with Schmitt-
Triggering[1] to provide a clean digital signal when the
buttons are depressed. Each time a button is pressed, it
triggers an interrupt on the dedicated MSP430G2553. This
allows the players to press a button at any time, regardless
of what output is being displayed. However, this is limited
to handling only one button press at a given time. Players
that press more than one button near-simultaneously see
behavior based on when the signal is actually interpreted
by the MSP430G2553. The advantage of using interrupt-
based buttons is that the MSP430G2553 can be placed in a
low power state while no buttons are pressed. This will
save power in the long-run versus the MSP430G2553
constantly polling the pins to which the buttons are
attached to detect a change in state.
The LCD display runs on a 5v power source, different
from the MSP430G2553, however, the display is back-lit
to be seen in the dark and will let the players know that the
LCD has power. The LCD display is connected to the
MSP430G2553 at the TXD pin (numbered 1.1). The
MSP430G2553 uses the built-in TimerA module to output
to the LCD via the RS232 standard at 9600 baud.
C. Aesthetic LED Array
The lighting system is designed with the ability to cover:
minimum 4 different animation patterns, exclusive control
of minimum 30 separate lights, and only 2 lines of input
for control. Additionally, the game table is referred to in 3
regions. The areas in which the lasers and capacitive
sensors are located are Regions 1 and 2. The area in
between these two regions will be known as Region 0.
Region 1 and Region 2 will both have LED diodes running
around the perimeter of the regions. Region 0 will consist
of two separate strips of LEDs running the sides of the
Region. The main patterns covered are meant to
distinguish which team is on the offensive, victories, or
pauses in game play. The layout of the Regions is shown
in Fig. 3.
The entire array of LEDs is controlled by a system
containing an MSP430G2553 microcontroller, decoders,
and transistors. The microcontroller takes in a 2 line input
and decides which animation sequence to execute. These
input lines utilize I2C, a common serial communication
interface to allow for virtually unlimited pattern selection.
The outputs of microcontroller will go into a matrix of
decoders built to drive various outputs for the animation.
Although the design lacks the ability to choose to power
more than one light at a time, the microcontroller takes no
extra hardware and wiring to create the effect of multiple
lights on at a time. The flicker fusion threshold is
described as the frequency of at which periodic light
pulses appear to be a complete and continuous light source
to the observer. This phenomenon is caused by the
stimulus effect of the photo lasting longer than the period
of time in between light pulses. Generally humans cannot
detect flicker above about 50Hz. For the light intensity of
LEDs, it is more effective to run in the range of kilohertz.
The chosen MSP430G2553 microprocessor uses 5 of its
digital outputs as control lines for the decoders to decide
which LEDs to turn on. Five CD74HC238 active high 3 to
8 decoders are wired to create a 5 to 32 decoder by using 1

decoder to toggle the enable line of the following 4 (see
Fig. 4).
Fig. 3: This represents the layout of the animation Regions on
the table. The LED patterns are controlled by a single
MSP430G2553 outputting to a series of decoders.
Fig. 4: This shows the setup of the smaller decoders to create
the much larger 5 to 32 decoder. One decoder is used to enable
the other four decoders to allow for a greater number of light
patterns.
The entire Aesthetic LED array system exists on 2
printed circuit boards. One printed circuit board contains
the decoders and the microcontroller and the second
containing the transistors and appropriate resistors.
There is a total of 360 LEDs being driven throughout
the entire system. The LEDs are embedded inside of the
table’s wooden frame and shine though the acrylic top
surface (see Fig. 5). Each transistor is responsible for
driving 12 LEDs. The anodes of the LED (positive leads)
all are connected to provide even power to all LEDs on the
table by a power rail. The cathodes of the LEDs are
connected in groups of 12. Each of these groups are wired
in series to their respective collector nodes of the 2N4401
NPN switching transistors. The output of the active high
decoders is connected to the base node, essentially a
switch, of the transistor. All of the emitter nodes are
grounded to the power supply’s ground. The LEDs,
microprocessor, and decoders all operate on 3.3v.
Fig. 5: This shows a cross-sectional view of the edge of the
table surface and aesthetic LEDs. Each of the anodes of the
LEDs are connected together, and each of the cathodes are
connected to a corresponding transistor.
D. Cup Sensors
Each team’s side of the table contains an array of six
“cup sensors”. These cup sensors act to detect the presence
of liquids contained within plastic party cups, which are
placed above the sensor during game play. Each cup
sensor unit consists of a Texas Instruments capacitive
touch module, used to detect the presence of liquid, five
RGB LEDs and a Texas Instruments TLC5940 LED
driver, for aesthetics. Six of these cup sensor units are tied
together and connected to a MSP430G2553
microcontroller, which communicates information about
the presence of liquids above the sensors to the central
controller.
Capacitance sensing is done via the capacitive touch
units and the MSP430G2553 which the cup sensors are
connected to, using what is known as the “Relaxed
Oscillator” sensing method. In this method, a single pin of

a capacitive touch unit is fed into the MSP430’s
comparator, as the tuning element[3]. The physical
properties of the system, such as effective resistance and
capacitance, create an oscillation at a certain frequency.
The output from the comparator is then fed into the Timer
A module of the MSP430 as the module’s clock source.
The Timer A module is basically a counter which
increments a register whenever the clock source goes high.
By driving the clock using the output from the comparator,
a change in capacitance from a capacitive touch sensor
effectively creates a change in the clock’s frequency, as a
change in capacitance will change the RC time constant of
the system. Fig. 6 illustrates this system.
Fig. 6: Driving Timer_A clock using Relaxed Oscillator
method. Capacitive touch unit varies clock frequency[3].
In order to actually measure a change in capacitance, the
value of the Timer A counter (TAR) is checked for a small
window of time. To do this, the Watchdog Timer Interrupt
is used as a measurement window gate. When the interrupt
is triggered, the value of TAR is checked, and the WDT is
set to trigger again in a certain amount of time. When this
second interrupt occurs, the value of TAR is checked
again, and the difference in the values is determined. A
change in this difference is of interest, as the change is
caused by a change in capacitance. Fig. 7 illustrates this
process.
Fig. 7: Using WDT as measurement gate for capacitive touch
measurement[3].
E. Discretizing Laser Array
The discretizing laser array was easily the biggest design
challenge of the Digital Competitive Precision Projectile
Table Support Structure. The purpose of the array itself is
to address the issue of distinguishing a missed throw from
a throw whereby the ball landed in a cup. Originally, a
multitude of designs were postulated, in an attempt to
solve the problem with minimal cost, effort, time and
complexity. The laser array proved to be the most feasible.
The discretizing laser array is just what one would
imagine based solely upon the name. In the array, forty
five laser emitters and detectors are situated five and three
eighths inches above the surface of the table, around the
perimeter, with one inch between each emitter/detector
pair. This spacing ensures that at least one laser beam is
broken whenever a ball passes through the laser plane.
These laser emitter/detector pairs are situated in two
axes, one spanning the width of the table, and the other
consisting of two separate regions, each spanning the area
where cups are placed on the table. This orientation
effectively creates a Cartesian plane over the table,
illustrated in Fig. 8.
Fig. 8: Illustration of Cartesian plane created by discretizing
laser array.

Creating a Cartesian plane above the table enables the
system to pin point the spot where a ball passed through
the laser plane, with good accuracy.
All forty five photodiode detectors of the array are
multiplexed to a single MSP430G2553. In order to
actually detect breaks in the array, the MSP430 scans
through the array many times per second, measuring the
voltage across a resistor, generated by the current output
of the photodiode, using the MSP430’s onboard
comparator. When the laser is not blocked by any object,
the voltage across the resistor is equal to the input voltage,
and the comparator outputs a one. On the other hand, when
a ball or hand breaks the laser plane, the voltage across the
resistor is effectively zero, and the comparator outputs a
zero. The difference between a ball and a hand is
determined by counting the number of times a single
emitter/detector pair’s output is zero before it goes high
again.
F. Ball Washer
The system consists of low maintenance cleaning system
to keep acceptable levels of hygiene throughout the
players’ experience. The overall layout of the water
sanitation system and pipe routing is shown in Fig. 9. The
water circulating system contains a water reservoir
containing the majority of the water supply in the system,
two cleaning basins for user and ball access, a cleaning
unit to disinfect the water system, a pump supplying
recirculation of collected fluids, and interconnecting
piping to move the water between systems. The water
system specifications are as follows:
• Nonreactive with alcohols or phenols
• Can withstand temperatures ranging between
40F-120F
• Water Tight
• Retain structural integrity over extreme
temperature change through conduction
1degree/second OR sudden contact temperature
change over 30 degrees Fahrenheit
• Able to maintain operational integrity with
extended exposure to UV radiation
The reservoir and ball washing units are made of PVC
and connected with nylon adapters with vinyl tubing for
flexibility of routing. The water is sanitized using a 345nm
ultraviolet light for killing germs and bacteria.
The pump is housed inside of the reservoir system and
runs at 180gph. The water is pumped from the reservoir
through the UV sterilizer for sanitizing. The sterilizer is
rated for 99.9% effectiveness with a maximum flow rate of
1800gph. The water is then discharged into the separate
ball wash cups. As shown in Fig. 10, the water then exits
the ball wash cups and flows back into the reservoir. The
sanitation system runs on 120VAC power also provided by
the power supply system.
Fig. 9: Illustration of oritentation of water system
supply/return lines. The pump and filter system is abstracted as
the square in the middle of the image.
Fig. 10: Illustration of wash cup design. Water feeds in from
the top, and drains from the bottom, creating a wirlpool effect
which will wash dirt away.

G. Power
The power for the DCPPTSS is provided via an ATX
computer power supply. The computer power supply
provides stable, surge protected, voltages and current at
the required value. 4 large 18 AWG lines run the perimeter
of the table each color coded to denote its potential. Black,
white, red, and yellow all denote 0, 3.3, 5, and 12
respectively. The power supply unit takes in 120 VAC at
60Hz and supplies the needed voltages to each system.
III. CONCLUSION
The Digital Competitive Table Support Structure seeks
to increase the enjoyment and fun legal-aged players of the
game of Beer Pong can have when playing. It allows
players to concentrate on actually playing the game,
instead of the tedium of the rules. The discretizing laser
array determines a hit or miss when a player throws a ball,
and the aesthetic LED array responds accordingly. If a ball
is thrown and does not land anywhere near the table or the
discretizing laser array, the user interface is used. It also
handles those unique situations that the table is unable to
handle automatically.
The DCPPTSS has been tested in limited groups and
does increase the enjoyment and fun factors when players
play the game. The user interface is easy to use, and the
components do not get in the way of playing the game. If
the table were to lose power, a normal, low-tech game of
beer pong can be played with no modification of the table
whatsoever.
ACKNOWLEDGEMENT
The authors wish to acknowledge the assistance and
support of Dr. Samuel Richie, Dr. Parveen Wahid, Dr.
Chung Yong Chan and Dr. Elena Flitsiyan; as well as the
rest of the professors which have taught them so much
over the past four years.
BIOGRAPHY
Christian Braun is currently a senior
at University of Central Florida,
majoring in Computer Engineering,
with a minor in Mathematics. He is
currently working in an internship
at Lockheed Martin Missiles and
Fire Control. He hopes to obtain a
position as a design or test engineer
at a large microelectronics manufacturer.
Rashon Hogan is a native
Central Florida student at the
University of Central Florida
pursing a Bachelors of Science
in Electrical Engineering. He
currently is a team lead for
modularization research and
development at Siemens
Energy. Rashon plans to
concentrate his career in
embedded processor and
electronics integration into
“smart” devices.
Jelani Jackson is a 25 year-old
Computer Engineering student
who is currently working at
Innovative Data Solutions Inc.
as a junior software developer.
He hopes that upon graduation
he will obtain full-time
employment at Innovative
Data Solutions Inc.
Donald Thomson is a senior in
the Department of Electrical
Engineering and Computer
Science at UCF. He will be
graduating with a BS CpE in
Spring 2012. He plans to
become a full-time employee at
Symantec Corp. where he is
currently an intern, and will
later seek a master degree in
Computer Engineering.
REFERENCES
[1] Texas Instruments, "MSP430g2x53, MSP430g2x13 Mixed
Signal Microcontroller (Rev. E)," January 2012.
[2] Newhaven Display International, Inc, “NHD-0216K3Z-FL-
GBW Serial Liquid Crystal Display Module,” November
2011
[3] Albus, Zack. "PCB-Based Capacitive Touch Sensing With
MSP430." MSP430 WW Applications. (2007): n. page.
Web. 9 Apr. 2012.