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A diagram of the playing field is shown below. Two robots race around
side-by-side tracks, each following a black line. Between the two tracks
are three balloons. There is a small light opposite each balloon. Your
objective is to go around the track and pop more balloons than your competitor.
If both robots pop the same number of balloons, the robot that circles
the track first wins.
Figure 1. Diagram of the Balloon Bust playing field
Rules
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Before the race begins, the robot will be inspected to ensure it
meets the construction rules. The driver may make changes if necessary.
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Each robot may circle the track in either direction, clockwise or
counterclockwise, at the choice of the driver.
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Before the match there will be a coin toss between players. The loser
of the coin toss chooses which direction his or her robot will circle
the track and places the robot on the track facing that direction.
The winner of the coin toss then chooses his or her direction and
places the robot on the track. The robots may go in the same or opposite
directions. The robot is placed so that no part crosses the starting
line. Once placed, the robot cannot be moved.
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When told, each robot driver will press the green “run”
button and the clock will start.
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The robot must follow the path until it fully crosses the starting
line again. The race time is the time from when the GO signal is given
until when the robot is fully across the starting line for the second
time.
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The driver cannot touch the robot once started, except to place
it back on the starting line or remove it from the playing field.
Figure 2. Robot in the starting position. Only one track
is shown.
Robot Construction
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The robot must be not more than 10 inches wide and 10 inches long
at the starting line, including any extensions. There is no height
limit. It is OK for the robot to extend itself to more than 10 inches
wide or long during the race.
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The robot must be built from pieces from the Lego Mindstorms Robotic
Invention System kit. You may also use up to 3 push pins (for popping
the balloons), tape, and paper.
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The robot may use any number of motors and light sensors.
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The robot must sense and respond to the lights in order to detect
the balloons. It may not extend an arm in a fixed position and try
to pop the balloons as it passes.
Playing field
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The track is constructed from white bookshelves, approximately 10"
x 36" x 5/8". Place 3/4" wide black electrical tape
on each track section to create the patterns shown in Figure 1.
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The lights are made from a flashlight blub, socket, and wires connected
to a 9-volt battery. The bulb is 4 inches above the track and directly
opposite the balloon. You can make a holder for the light bulb using
Lego pieces. Hint: The flashlight bulb socket from Radio Shack has
a tab that just fits into the gray or brown pully with 6 holes in
the Lego kit.
Figure 3. A light holder made from Lego bricks.
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The balloons are about 8 inches in diameter when inflated. They are
taped to bookends on both sides about 7 inches high to hold them in
place. The bookends are taped to the playing field.
Figure 4. A balloon held in place with two bookends.
Single Balloon Race Practice Field
To practice for this event you may set up just one track during your
club meetings. This reduces the amount of supplies you need and setup
time.
Figure 5. A track set up for a single balloon race.
Hints and Tips
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Your robot will need at least two light sensors for this game - one
to sense the black line and one to detect the lights.
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There are at least two ways to pop the balloon - by turningthe robot
and running into the balloon with a pin in front, or by using a robot
arm mounted on top. A robot arm will require a third motor.
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You can develop the programming skills you need for this event by
working through these Lego Robot tutorials: Light
Sensors for Robot Games and Follow
a Line.
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Write and test your robot program one step at a time. For starters,
just make it follow the line around the track. The you might make
it detect the first light and stop there. Then pop the first balloon,
etc.
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How do you program a robot to read and respond to two light sensors
at once? Here is a simple program that uses two light sensors. You
can use it as an example and starting point. The robot will go forward
when light sensor on port 1 sees white (brightness > 40), and backwards
when light sensor 1 sees black. It will play a sound when the light
sensor on port 2 sees a light (brightness level > 80). Enter this
program in RoboLab, download it to your robot, and test it.
Figure 6. A sample program that uses two light sensors.
Strategy
A few thoughts on strategy for this contest:
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If you can pop 2 balloons and complete the circuit, you win, since
you will be guaranteed to pop more balloons than your opponent. So
you might think about ways to get to two balloons before the other
guy.
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If you win the coin toss, you get to decide whether to circle the
track the same direction or the opposite direction from your opponent.
This can be a strategic advantage. To use this advantage you will
need two robot programs ready and loaded into the robot - one program
for clockwise and one for counterclockwise. Then after you opponent
sets down his/her robot, you can select the correct program with the
Pgrm button. You may also need to make a quick change in the direction
the second light sensor is pointing.
Materials for Single Balloon Race
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5 or 6 white bookshelves, approximately 10”x36”x 5/8”.
(Meijer's)
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Black electrical tape, approximately 3/4” wide
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3 flashlight blubs, 3 flashlight bulb sockets, 3 9-volt battery clips
and wires, 3 9-volt batteries(Radio Shack). The wires must be soldered
to the socket terminals.
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A bag of 7" - 9" diameter round party balloons
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Six 7" high bookends (office supply store)
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Scotch tape or equivalent
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3 push pins per robot
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