After I coached the "Robot Ramble" team for Mount Carmel High School's 2008 Science Olympiad team, I suppose there was no chance I'd get out of coaching an event for 2009.
The Science Olympiad folks served up a new event for this year, "Junkyard Challenge". The event consists of students partially pre-building an autonomous device to complete a pre-defined task, but the students must incorporate one or more "Mystery Materials" into the final build that takes place on-site at the start of competition. Its a great way for the competitors to demonstrate the ability to improvise, and potentially exposes them to a lot of different concepts.
The task for the regional-level competition was "Tipping the Scale", in-which the students must build a device to determine the mass of a challenge object provided during the test.
There were a number of ways to build a simple mechanical device based strictly on Hooke's law or a balance scale, but I asked my team if they wanted to try something more advanced, and they said "Yes!".
I'm proud to say that my team of High Schoolers built themselves an electronic scale, complete with a hand-built 5-stage ring oscillator biased by parallel plate capacitor acting as a transducer to measure the compression of the scale as mass was added. Besides my usual safety lecture and introduction to various machining operations for the mechanical part of the build, I had to introduce the team to some of the basics of electronics, including RC-circuits and the basic concept of an ideal parallel plate capacitor.
The concept for the capacitive transducer is based on something I was exposed to during an internship back in college. Obviously there are better (cheaper, easier, more accurate) ways to detect mass, such as using a strain-gauge load cell, but the competition rules were very explicit in disallowing any components harvested from commercial scales. To avoid any possible problems, I helped them build the whole device from absolute scratch.
I couldn't be more proud, as my guys took 4th place in their event, and MCHS took 2nd place overall, meaning a select portion of the team is headed to the State Competition in Long Beach on April 18th.
See more pictures of the build process in my web album.