After using my Mark I wind controller for about 10 years, I started to get a little paranoid about its reliability. The key switches were getting a little old, the wiring was getting old – it was built using lots of point-to-point wiring. Plus, what I learned from working with PICs on the walking robot let me design a new controller with just 4 chips instead of the 21 integrated circuits used in the Mark I. Power for the wind controller comes from an interface box, which contains a conditioning circuit to generate a stable +5V from two AA batteries. It has an interface jack for a foot switch, which is useful for special effects like sustaining or droning notes, selecting interval mode, and other programmed features. Below are some photos of the finished unit and its interface box (the small blue box). A note of explanation – the wind controller doesn’t generate sound in itself, it just creates and outputs MIDI data. I use a Korg 05R/W synthesizer to generate the sound. The Korg is the black box in the third picture below. The Korg is like a keyboard sound source without the keys, and the wind controller is what’s taking the place of the keys. Of course, with the pressure transducers and all the MIDI data they generate, there is lots more expression available to control acoustic wind sounds.
Samples below are me playing the wind controller connected to the Korg 05R/W synth. No sequencing or other multitrack recording was used for any of the samples, and all are recorded live from the synth.
The round flat pad in the pictures is a force sensing resistor (FSR) from Interlink Electronics. It measures lip pressure to detect how hard the mouthpiece is being squeezed. This signal is useful to generate MIDI pitch bend commands, allowing you to bend notes just like on a real acoustic wind instrument.
Circuit Boards and Body
There are three circuit board assemblies, the main board that has the processor and other active circuitry, an upper switch assembly for the fingering buttons, and a lower switch and LED assembly. The lower assembly connects to the main board before being inserted into the case. The upper switch assembly is mounted to the top half of the case and connects to the bottom half sandwich with a small ribbon cable. The circuit boards are housed in a case made from cherry and walnut with some decorative inlays on the bottom part. The main body of the case was assembled as an octagonal assembly, but was rounded on the outside for that traditional instrument look and shape. Just like the Wind Controller Mark I, the new wind controller has at its heart a wind pressure sensor to detect how hard you’re blowing. A Fujikura XFPN-050-KPGT1 is used as the sensor. The brass tubing coming from the mouthpiece has a small tap tube connected inline that the pressure sensor’s port slips into when the circuit board is put into the case. The brass tube goes all the way to the bottom of the wind controller to drain away the inevitable moisture that gets blown through the instrument.
Below are all the schematics for the Mark II. The first photo is the main PIC16F877 processor along with the LED multiplexer. There are plenty of inputs in this PIC to handle all the key switch inputs. The PIC also has a built-in multi channel analog-to-digital converter that’s used to read the breath and lip pressure sensors. The PIC’s Universal Asynchronous Receiver-Transmitter (UART) is used to drive the MIDI output. All the PIC software to process the fingering switch and sensor inputs to generate a MIDI output is written in assembly language. The second photo shows the analog buffering circuitry. A Maxim MAX479 micro power precision quad op-amp buffers the sensor inputs for the PIC. The third photo shows the interface box that holds a circuit to generate 5V from two AA batteries.