Every year, the gifted program my son Kyle is in has an contest to make a creative box to collect Valentines for Valentines Day. The kids vote on the winners for each grade. Last year (3rd grade), Kyle designed a box that used our robot Hexbug Nanos. He got second place. The winning box last year was a beating heart (that's would be tough to beat for sure!).
I think Kyle really wanted to win this year, because he said he wanted to have a slot where the kids insert the Valentine and then a robot "hand" comes up and hands the kid a message. I thought, wow, how will I help him pull this off??
We do not have Lego Mindstorms yet (coming soon, though...) but he was experienced with FischerTechnik from the Summer Robot Building project that we did last year
http://paradiserobotics.com/forum/index.php?topic=339.0. We decided we could probably make it work with FischerTechnik and Legos, but I challenged him to think of a way to exploit the rotational nature of the motor (my kit does not have a servo motor). Whew, he realized he could build a ferris wheel-like structure out of Legos. We hoped we could use the Fischer Technik gears and somehow attach it to the Legos.
Detecting the Valentines is easy because my FischerTechnik kit has a focused light beam and a light sensor. At first he was planning to say "Happy Valentines Day" multiple ways on the wheel, but I knew he could be more creative than that. Later, he decided to put a different message on each section of the ferris wheel that would stop at an opening in the box. The fortune teller was born!
Building the wheel and mating it to the FischerTechnik motor and gears was a challenge. I'll have to say I am tremendously impressed with my son's Lego abilities. We have not sorted his massive Lego bin yet, however somehow he manages to come up with just the right piece really quickly. Trial and error got us to the point where we had to connect the Fischer Technik gear shaft to the Lego shaft of the ferris wheel-like structure. We tried a few different things and actually settled on strong drafting tape to hold it together. It worked well. The biggest challenge was finding the right-sized Lego pieces to bring the two shafts close together.
Then we did the program. It was easy, but we had a slight hiccup. We needed the motor to turn slowly, but when we tried to start the motor slowly, it would not start.
We realized we needed to kick-start the motor with a short time (0.1 seconds) at a high speed and then run it for a few seconds at the slow speed. The next challenge was figuring out how to make it show a different message each time. Luckily this turned out to be easy to do because the motor running time was not very precise and the variability in the controller timing was enough to give us semi-random results. We connected the Valentine sensors and added the programming elements for them.
The next step was cutting and decorating the box. This was not so simple because we realized we could not have Valentines falling on the robotics. Kyle had a clear idea of how to solve this and quickly drew a 3D picture of what he wanted. My husband and I did the box cutting, but unfortunately, I am not so good with a box cutter and I gave myself a deep cut in the finger (don't worry - I survived; no stitches). Kyle covered the box with construction paper, added decorations and "user instructions"
The instructions to the user are something along the lines of, "Think of a question having a yes or no answer and then put your Valentine in the slot". Kyle made 6 creative yes or no answers and put each one around the "ferris wheel". The ferris wheel showed through an opening and he positioned the viewing angle so only one message could be read no matter where the wheel stopped (that was clever; I was impressed).
Now that the decorating was complete, it was time to position the sensors. I talked Kyle into putting them on a diagonal across the slot for reliable operation, but we ran into a small problem. Kyle figured out right away that the sensors needed to be closer together because the light diffused too much when they were apart a larger distance. We did end up with a bigger gap at the bottom so I knew at times it would fail.
The final step was building more Legos around the motor & shafts to make sure the motor remained stable and did not slide itself out of the gear. We would not have had this problem if we only used FischerTechnik components. It took awhile to find the right Lego pieces but finally it as all done.
Kyle was thrilled when he won first place in the 4th grade contest!
Many kids wanted to know how it worked so he explained it a few times. I will post a link to a video soon.
I am already worried about what he will want to do next year to top this box... I told him we have to start working on it over the Summer!
