Player Piano

September 26, 2005 03:58 PM

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Assignment:
Hack an electronic appliance and create an alternative interface to its various switches. You are not allowed to use a computer in this project.

Solution:
Karen found this electronic keyboard on the street and I wanted to turn it into a player piano —er, keyboard. Whatever. I thought I would hook it up to a turntable which could play songs through the keyboard via special records (created by me).

I ran into two problems right away: First, it was very hard to find a reasonable priced turntable at the junk stores I visited. Second, when I finally found one I realized it was going to spin way too fast to be able to do what I wanted (the entire song would need to play in a single revolution of the record). I decided to just make my own (nonturning) turntable and spin the records by hand. Hacking a turntable to make it spin at the correct speed can be a project for another week.

Technical Info:
The switches for the keys inside the keyboard have an open circuit with the positive and ground very close together. When a key is pressed, it pushes a little metal strip to close the circuit for that note.

The key circuits: two positives and two grounds for each note

I wanted my record player to work the same way. Little metal strips on the record would pass under the exposed wires and close the circuit for a specific note.

Close up of player arm. Two leads for each of the 8 notes.

Unfortunately, I had trouble devising a method that makes good sustained contact with the wires while still allowing the record to spin through without getting snagged. I finally settled on little bumpy flaps of foil, but they’re far from ideal. To get it play a recognizable song (it plays the Star Wars theme) you have to spin the record very slowly and deliberately.

Project: Player Piano | link

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