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The Electronics

A project log for Multiwind

A modular system for multimodal hands-free music control, wind instrument development and general human computer interaction.

Chris GrahamChris Graham 08/18/2018 at 16:571 Comment

Here are some images of the current schematics and PCB layouts.

Overall, the prototype is working exceptionally well.  

I wrote a simple program for the Teensy that reads all sensors: the lower lip and oral cavity optical sensors, the upper lip capacitive sensor and the pressure sensor.  All are amazingly controllable as viewed in form of raw ADC values printed to the serial monitor. 

The dynamic range and controllability of every sensor is exceptional.  Based on past experience they should convert to an outstanding user experience of midi controllability.  I'm pretty sure this will be able to provide an entirely different and superior user experience vs the mouthpiece of any commercially available wind controller that ever existed.  Over years of research I've tried almost every one.

I have not yet assembled and tested the display, IMU or external connector but all that should be pretty straightforward now that the mouthpiece itself is working so well.

The next step will be to design and make another version of the 3D model and main PCB adding some more features and correcting a few minor problems:

- It was difficult to solder the surface mount version of the serial port connector so change to the through hole version.

- Correct a minor error where a PCB trace was omitted where it appeared to be connected in the schematic but was really not connected.

- There should be enough room in the housing for up to a 250 mAh Li-Po battery so look into whether the circuit can include this and the ability to charge it over the USB connection.

- Add the ability to power the board either from USB, from a battery, or from power from the finger unit coming up the power line of the serial connector.  Powering from the finger unit, when present, would allow a larger battery capable of powering the mouthpiece for longer.

- Look into adding a connector for old style MIDI output.  I reserved the second TX line on the Teensy for this purpose and all that's needed is two resistors and a small connector.  A full size midi connector would not fit in the housing.  I need to look for a small enough three or four pin connector to carry the MIDI signal to an adapter cable.

- Look into including a vibrator motor to provide tactile vibratory user feedback.  The electronics only require a PWM output, a transistor and a button sized vibrator motor.  I reserved a PWM pin on the Teensy for this purpose.  I've wanted to try vibratory feedback for a long time as it could be a way of communicating to the user states of the mouthpiece such as that they are at a zero level of pitch bend, or that they are on a resonance sweet spot when planing a physically modeled instrument such as a trumpet.  It may also be used in hands free human computer interaction.

- The other unpopulated daughterboard next to the IMU (in the 3D models of an earlier log update) could be used for various purposes but most importantly might be used to add wireless midi.  This won't necessarily be a feature in the short run but I need to look into it to the extent that there would be the capacity to fit it among the other existing components.

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