1. Lucas Dias and Fabio Mantelli
Air Piano

2. 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

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

4. Arduino Micro

5. 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

6. Photoresistor
Resistance decreases with increasing incident light intensity.

7. 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

8. 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

9. 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

10. 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 are reserved as "Channel Mode Messages" (below). (ccccccc) is the controller number (0-119). (vvvvvvv) is the controller value (0-127).

11. 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

12. Photos

13. 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

14. References
Pictures and information taken from: