Jan. 9-19 Jan. 20-23 Jan. 24-27
There were always random LEGO pieces floating around and it is so time consuming to sort all the pieces, so we thought it would be great if we could build a LEGO sorter for our final project that could put all the pieces back into the proper tubs.
Considering the age group of the audience, we thought it would be
tons of fun if we could do something involving water and catapults
for our final project. Perhaps we can reenact a sea battle and have
2 remote control cars and arm them with catapults that can launch
Or we can build a water obstacle course and have 2 remote control boats race each other. It would be like slalom, except in water.
After talking to Lyn about our water obstacle idea, he told us that
maneuvering a vehicle in water would be really difficult and we
should perhaps make an easier game. Using the same components we
originally had (catapults and water vehicles) we can make a game
similar to water polo.
The vehicles can be rubber ducks with propellers and the catapults
can be mounted on top of the ducks. We would also need a ball scooping
mechanism to load the catapults (poppers that we built from a previous
challenge). The goal would have a switch that is connected to a
HandyBoard that can register the number of “hits”. Perhaps whoever
gets 15 goals first win? Lights and music could go off when someone
We wanted to use rubber ducks to keep for the water vehicle because
they would be good floatation devices for the motors and they are
really cute. A propeller or waterwheel could be mounted to the back
side of the rubber duck to move it. Rebecca Shapiro (an alum of the
course) pointed out that if the rubber ducks were not stable enough
we could add small wheels (like the SciBorg wheel) under the ducks
for balance. If we use waterwheels it would make more sense to put
them on either side of the ducks. This would also mean that we would
need to use 2 motors so that the waterwheels can operate independently
of one another (like the SciBorg).
Since the catapults (a.k.a. poppers) are rather large we would need
to have a pretty large rubber duck. It might be a better idea to have
the catapults on land, that way we can build smaller water vehicles.
The rubber ducks can come equip with a net that could scoop up the
ping pong balls out of the water and reload the catapult. The net
can scoop up the balls with an up down motion.
Since the catapults are on land a reloading mechanism from the water
is necessary to deposit the balls into the catapult. At first we came
up with the idea of using a conveyor belt that would run parallel
to the catapult and drop the balls down into the catapult. Then we
realized that there would be a timing issue since the catapults would
be running continuously. Also it would be very likely that the balls
would pop out of the catapult. Instead of the conveyor belt we could
use a trough to deliver the ping pong balls to a see-saw. The ball
would wait at the bottom of the see-saw until the arm of the catapult
comes down and tips the ball forward, making it roll onto the catapult.
Each duck will have its own goal and catapult. The ducks will have
a net in the back to gather the ping pong balls and deposit them into
a trough which will lead to the catapult. The ducks will also have
a chance to defend their goals with a stop sign on their backs which
the duck can raise to deflect an incoming goal. The catapults will
be in line with the opponents’ goal. The first one to make 15 goals
Robbie thought the scooping mechanism may be too difficult and suggested that we used a plow-like mechanism instead. This way we would only need 3 motors instead of 4 motors. If we use the plow-like mechanism we will put the ball collecting mechanism in front of the duck.
We decided to leave the stop sign up instead of having it move up and down. Now we are down to 2 motors from the previous 3! This will also leave us with 2 extra ports.
Instead of having a HandyBoard to display the score we wanted to use
the display boards that come with the Crickets. Unfortunately, the
Crickets and HandyBoard cannot communicate with each other. Robbie
suggested that we use a LOGO chip instead and have LEDs light turn
on whenever a goal is made. We can also have a song play whenever
(a.k.a. popper - from http://www.pienetwork.org/a2z/m/modules/ only changed sides for one of the teams)
It turns out the popper that we built from Challenge #7 doesn't throw
that far (a foot a most). So we experimented with the popper and changed
the arm length, rubber bands, and the release angle.
Increasing the arm length didn't increase the range all that much.
It turns out the release angle is too small and the ball was being
released too soon, making the ball shoot really high instead of far.
We figured the optimal release angle would be 45º, the change of the
release angle dramatically increased the range of the catapult. After
we got the catapult to launch far enough, we tested its consistency.
We found that our catapult was pretty precise and launched ping pong
balls about 78cm horizontally (distance meaured from the front of
Since we were planning to use 4 crickets (2 on the ducks for the motors,
and 2 for the remotes) we used the Blue Dot Crickets (older model).
Now that we had the crickets, we had to figure out a way for the Crickets
to communicate with each other via remote controls. We originally
wanted to use IR signals, but then there would be the issue of miscommunication
(i.e. one remote could potentially control two ducks). Also the IR
signal seems to have a pretty short range, so there is the issue of
unintentionally blocking a ping pong ball. Robbie suggested we use
light sensors for eyes and had the ducks follow the flashlight. This
way it would be more interactive and look less like a video game.
However, after testing out the range of the Blue Dot Crickets we found out that they had pretty good IR range (much better than the new version)! We decided to use a remote system because it would be easier to control the ducks. Robbie then suggested that we could make our own remote using different resistors because the Blue Dot Crickets only have 2 motor ports and 2 sensor ports. We don't really know how this hooks up to the Crickets . . . we shall ask later.
Robbie drew us a picture of the circuit for the breadboard and we had to figure out how to hook up all the wires, resistors, and switches to make our remote. This proved to be a lot more difficult than we originally anticipated. After several tries we finally got the connections right. The current arrangement of the switches makes it so the remote buttons are all lined up vertically. This remote will only take up one of the sensor ports on the Cricket! The four different resistors will make it so the Cricket sends out four different IR values.
For our pool we are considering using an under bed storage container. However we think it may be too long and not wide enough. But we’ll have to wait until we build our ducks.
- Rubber ducks (2) . . . turned out to be a lot harder to find, after multiple visits to various toy stores and Linen and Things we gave up and decided to make our own boats and decorate them to look like ducks.
- Ping Pong balls.
- Balsa wood (for the waterwheels) . . . ended up getting bass wood instead because it is slightly sturdier.
- Wood glue
- Modeling clay (for the trough)
We didn't know how to go about building our water wheels, so we looked up some picture of waterwheels on Google to get some ideas. After looking at several pictures we decided to use a 40-tooth gear and glue the spokes in between the teeth and then these teeth will be reinforced by strips of wood on both sides.
After going to the store to get our materials, we started to build the waterwheels. The wood glue doesn't seem like such a good idea now because it takes a very long time to dry and you have to hold it in place until it dries enough to stand on its own. This is extremely tedious, so we decided to use hot glue instead. It dries almost instantaneously and it is much more forgiving (i.e. if you mess up you can peel off the glue and try again) =) We will build the rest of the waterwheels tomorrow.