Abella, enclosed

Although Abella used to live in a shoebox, now the electronic musical instrument has been fully soldered and packaged in a project box.  The prototype is complete!

abella_annotated

Note indicator: provides a color-based indication of the current note selected.

Key selector: multi-switch input to set the key.  The first 7 switches correspond to C major through B major, and the last switch changes the key to major pentatonic.  With no switches activated the key is chromatic.

Note selector: covers 2 octaves of notes in the selected key

Volume control: Turn clockwise to increase the audio output

Mute: comprised of an IR light source and an IR phototransistor.  Block the path to mute the sound.

Clutch: with the clutch depressed, move the note selector and the note indicator will show next note.  Release the clutch to begin playing the note.

 

How does it work?

Abella uses an ATMega328 microcontroller to generate sound by direct digital synthesis (DDS).  The waveform is not a sine wave, but a combination of the root frequency overlaid with the higher two octaves and perfect fifths.  The root frequency is set by a linear potentiometer, and the key is set by a DIP switch.  An internal accelerometer produces a +/- Z signal that is used for frequency modulation when Abella is rocked up and down.  The 0-5 V output is filtered and attenuated for compatibility with audio amplifiers.

 

 

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