Banana Synthesizer

Fully featured silly synthesizer.

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Final project for CS 325 Inside the Box: How Computers Work.

To use, simply put on the wrist strap and touch the bananas. You can press multiple bananas simultaneously to play chords. A central control module provides the ability to shift octaves up/down and apply effects.

One effect is a pulse width modulator, which turns the boring chiptune square wave into a more energetic 80’s sound:

Another effect is a modulated low pass filter, which gives a nice “wub wub” effect:

The control module provides toggle switches and dials for adjusting the frequency of each effect’s modulation.

The main board is an ARM LPC1768, which runs the synthesizer simulation. Three Microbit boards each run a simple program to forward their touch inputs to the LPC1768, providing 9 effective touch inputs. The touch inputs use weak (10M) pull-ups, which is enough so that completing a circuit through the hand/banana still pulls the voltage down.

On demo day for this project, I caught the attention of assistant professor Ivan Lee, who offered me a research position on batteryless sensing as a result of my efforts.


I wish I got a longer video to properly demonstrate all the effects, but you can get an idea of the tone:

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