I am back in quirky, wonderful Manchester, New Hampshire (AKA Manch Vegas) for Constructing Modern Knowledge 2012. This is my second time attending and I have to say it is every bit as exciting, inspiring, and fun.
I decided to try to perfect my LEGO record player design at CMK this year. I started one at the last CMK I attended as an eleventh hour project. It would spin the record, but much too fast and without much amplification.
I partnered with Maryann, who I met two years ago at CMK. She wanted to learn more about using LEGO WeDo, the kit that we would use to build our turntable. I decided to use Scratch rather than the LEGO WeDo software because Scratch works with the WeDo motor and sensors and allows better control of the motor speed, in my opinion.
We started by building a simple rig to determine how many revolutions the motor would make in thirty seconds at three different motor speeds: 100, 50, and 10. At 100% the motor spun too fast for us to count. At 50% the motor spun 108 revolutions in thirty seconds. At 10% power the motor spun 16 revolutions in 30 seconds, which would get us about as close to 33 1/3 RPM as possible.
I brought a sewing needle to use as the stylus. However, it was not sharp enough. I took it outside and rubbed the point against a piece of granite curb. Before long it was sharp enough to fit into the small grooves on the record.
It took a little troubleshooting to figure out why the record seemed to be playing backwards even though it was spinning in the correct direction. It turns out that the arm needed to be opposite of where I was setting it. Here it is in the correct position on the record.
Once we had the arm in the right place we tried to figure out how to amplify the sound. We ended up poking the needle through a plastic drinking glass and using the "horn" to amplify the vibration of the needle as it passed over the grooves on the record.
We added some rubber bands to the cup thinking that our best bet for amplification might be to somehow attach a microphone using the rubber bands and pointing the microphone down the cup to amplify the vibrations. Without any amplification the sound was pretty weak.
We thought about using a microphone attached to Maryann's laptop to try to amplify the sound. It worked, but it was not elegant.
Shortly before we finished Mark wandered over and looked at the problems we were facing. He managed to track down a great design on a YouTube video and a web page. The arm, needle, and amplifier cup design would prove to be very helpful.
After we finished building for the day I walked over to the local music store to see what kinds of microphones they had, thinking a lapel microphone might work well. However, all they had was a large microphone like we already had tried. However, the salesman suggested that the key was the horn.
With a new design in mind I put down the project for the evening and prepared to pick it up again the next day.