Lucas Dias and Fabio Mantelli Air Piano

Objectives Create an “air piano”, with keys triggered by swiping fingers on top of several holes Communicate with a PC via MIDI Build a control module with sensors which change volume and sound effects

Components Microcontroller Keyboard Control module Arduino Micro Photoresistors 1 kΩ resistors Cardboard structure Control module Ultrasonic sensor (velocity control) Accelerometer (effects control) Breadboard structure

Arduino Micro

Arduino Micro Microcontroller ATmega32u4 Operating Voltage 5V Input Voltage (recommended) 7-12V Input Voltage (limits) 6-20V Digital I/O Pins 20 PWM Channels 7 Analog Input Channels 12 DC Current per I/O Pin 40 mA DC Current for 3.3V Pin 50 mA Flash Memory 32 KB (ATmega32u4) of which 4 KB used by bootloader SRAM 2.5 KB (ATmega32u4) EEPROM 1 KB (ATmega32u4) Clock Speed 16 MHz

Photoresistor Resistance decreases with increasing incident light intensity.

Ultrasonic Sensor Provides precise, non-contact distance measurements within a 2 cm to 3 m range Ultrasonic measurements work in any lighting condition, making this a good choice to supplement infrared object detectors Simple pulse in/pulse out communication requires just one I/O pin

Accelerometer Measures ±3 g on each axis, enough for data for a wide variety of applications Simple pulse output of g-force for each axis is easy to read for most any microcontroller Analog output of temperature (Tout pin) allows for fine-tuning of advanced applications Low current at 3.3 or 5 V operation (less than 4 mA at 5 VDC) puts low demand on the system

MIDI Protocol Musical Instrument Digital Interface Created in 1983 Analog to music notation Does not include “sound” information Open-Source Small messages Simple communication protocol Status bytes and data bytes

MIDI Messages Status D7----D0 Data Byte(s) D7----D0 Description 1001nnnn 0kkkkkkk  0vvvvvvv  Note On event.  This message is sent when a note is depressed (start). (kkkkkkk) is the key (note) number. (vvvvvvv) is the velocity. 1011nnnn 0ccccccc  0vvvvvvv Control Change.  This message is sent when a controller value changes. Controllers include devices such as pedals and levers. Controller numbers 120-127 are reserved as "Channel Mode Messages" (below). (ccccccc) is the controller number (0-119). (vvvvvvv) is the controller value (0-127).

Device Features There is an automated calibration routine for the photoresistors, since they are highly influenced by ambient light When a photoresistor senses a shade, the correspondent note is triggered and sent to the PC The values read by the ultrasonic sensor and accelerometer are translated to MIDI commands

Photos

Conclusion This project has several applications since inexpensive gesture sensing is important nowadays Socially assistive robots and devices Remote controllers Alternative computer interfaces DJ equipment Toys and video games

References Pictures and information taken from: www.arduino.cc www.parallax.com www.midi.org