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Proximity Controlled MIDI

Controller

By:

Randall Fassbinder

ECE 395 – ADSL

Final Report

Fall 2008

Abstract

The Proximity Controlled MIDI Controller is based on the same principles as a Theremin. It uses a

single antenna to control the modulation of different parameters on an audio signal via MIDI. The

depth of modulation depends on the capacitance of the medium surrounding the antenna. This

capacitance changes the frequency of an oscillating square wave and compares that to a reference

frequency. This signal is then read into a PIC microcontroller to output a MIDI signal based on the

capacitance. As an object becomes closer to the antenna (capacitance increases) the MIDI status byte

increases.

1. Oveview and Goals

This MIDI controller uses part of the University of Glasgow’s Digital Theremin to produce the

pulsing signals read. The idea is to read this into a microcontroller and instead of just modulating pitch

and volume, more parameters could be affected by using additional hardware. The goal was to output

a MIDI signal based on a frequency read by a microcontroller.

Ideally the controller should have a high resolution based on the capacitance surrounding the

antenna. The antenna should also have a large range of distance in which it is affected by capacitance

change. The MIDI signal should stay stable if the capacitance is not changing.

2. Hardware

4. Problems and Future Recommendations

The antenna doesn’t read a change in capacitance until an object a few inches away (about 5

inches). This makes using it very difficult. At the moment a long wire is where the antenna goes and

aluminum foil is wrapped around it to increase the range.

It would be very useful if a foot switch were added with an LED display to change and show the

channel and controller number. This would be relatively simple and the first change I would make if I

had more time. Another foot switch could be added to set a static status byte value.

5. Conclusion

Other than the problem with the range, I was very pleased with the way the project turned out.

Looking back on the semester, the hardest part was working with the PIC and figuring out small

problems with broken hardware. The basic concepts of how I wanted the programing to work was

the easiest part. This project has opened up my eyes to microcontrollers and I look forward to working

with a SHARC next semester.

6. Code: