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Instrument Basics

A project log for The Open Woodwind Project

An Electronic Aerophone with focus on usability as an instrument.

J. M. HopkinsJ. M. Hopkins 09/10/2014 at 13:560 Comments

Since this is a woodwind controller for MIDI data some things are a given: keys to change notes and a way to determine breath control over those notes. Everything else is pretty much fair game.

Fingering

I've decided to go with a fingering paradigm similar to a saxophone or flute, but also similar to Akai's EWI as well. 

The left thumb controls octaves, but dissimilar to Akai's fingering does not use rollers, but rather 4 keys giving a range of seven octaves (one for each key, and an additional 3 while the thumb is between keys).

To ease the octave break where players will practice hours and hours to rid themselves of glitching, I've added an extended fingering compliment both above and below the one octave. This is accomplished by keeping partial fingerings down while continuing into the next octave. I will publish a fingering chart later.

After playing with the new fingering system, runs that are fast around the break are readily achieved where before it would have been glitched.

Breath Control

Air is moved down the mouthpiece and to the pressure sensor which is read by the microcontrollers 12-bit AD converter and transformed into Note On/Note Off/breath controller data. The microcontroller auto senses the ambient pressure to determine the offset value for minimal breath level note activation. A max breath setting can be adjusted as well for a fine tuned responsive system.

Additional Control Sensors

There are a two other main sensors for additional CC messages. A physical pressure sensor on the mouth piece, and an IR distance sensor at the bottom of the instrument facing your body.

Two buttons at the right thumb can decide which CC is output by the sensor. Most common use would be pitch bend. The closer to the body the higher the pitch bend amount.

It makes for a very intuitive easy to control sensor for CCs.

Touch Sensitive Keys

The instrument uses touch sensitive keys with no mechanical movement. Similar to the EWI this allows for fast and accurate transitions between notes. Unlike the EWI I'm using a custom control board which actually sends a very very small signal through the body which then goes through the fingers and into the keys. The keys are then attached to a Darlington paired transistor setup which hugely amplify the signal that latches through a diode and into a shift register to the microcontroller. This allows for relatively fewer pins to be consumed and for there to be a faster response time due to there not having to be a capacitive recharge timing scheme for a true capacitive touch setup.

Wireless Transceivers

The microcontroller outputs it's data in a real-time MIDI serial connection. This data is piped into a Polulu Wixel 2.4GHz transceiver which connects to its pair attached to the computer. The computer then transfers the MIDI stream to your synth of choice (Propellerhead's Reason) and out your speakers.

Control Box

As of right now the computer side transceiver is just that, a transceiver. I will change it into having a 4 line LCD display with a 5 way button to allow changes of the instrument and monitoring of current playing and wireless signal level.

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