Electric Air Ukulele Ivan Setiawan (setiawa2) Satyo Iswara (iswara2) ECE 445 Senior Design Spring 2012 Team #32 TA: Jane Tu

Objective Implement a musical instrument that has a ukulele-like sound Simple, lightweight, and portable music instrument Pre-calibrated strings that do not need adjustments Inexpensive music instrument

Features Distance detection to determine hand positions Sensitive sensor system A wireless data transfer from the left to the right hands Finger bending sensor simulating string picking motion

Original Design and Final Design Original Design –LED indicator to show if the distance is within the boundary –Build-in speaker with operational amplifier Final Design –LED indicator is not implemented due to limited spaces of the box –Using commercial speaker provided in the lab

Project Picture Left Hand Design Right Hand Design

Block Diagram Power Micro- controller A Fret Pressure Sensor Fret Indicator RF Transmitter Proximity Sensor Power Speaker Flex Sensor Micro- controller B RF Receiver Left hand Right hand

Device Overview Left Hand 4 potentiometers Proximity sensor Arduino Uno Microcontroller RF Transmitter Power Regulator

Device Overview cont. Right Hand 4 flex sensors Arduino Uno microcontroller RF Receiver Speaker

Fret Potentiometers Variable resistance Varies linearly from 1 kΏ to 10 kΏ [1] Source:

Proximity Sensor Narrow beam angle Measure distance using ultrasonic pulse Accurate within the range of 2cm to 3m Has a blink LED indicator to indicate measurement

RF Transceiver 434 MHz frequency range Able to transfer data of 4800 bps Robust wireless data link transmission Using VirtualWire library in Arduino platform

Flex sensor Variable resistor based on degree of bending Use as voltage divider V out [3] source : [2] source :

Audio Output Arduino output PWM digital signal D/A conversion through low pass filter The V out DC offset then removed by blocking capacitor [4] source :

Waveform Result RF Transceiver Channel 1: Data transmitted Channel 2: Data received Generate a bit error at higher frequency value

Waveform Result cont. Analog output to speaker digital PWM output D/A conversion Remove DC offset Attenuating over time

Software Implementation Left Hand Idle Get Distance Within boundary Determine fret location Interpret chords Transmit data OFF ON NO YES

Software Implementation cont. Get data from RX String pick? Enable interrupt subroutine Output to speaker Sound decay? Right Hand

Challenge and Accomplishment o Challenge  Wireless connection between both hands  Output an ukulele-like sound through synthesizer o Accomplishment  Ability to send fret information via trans- receiver module  Successfully generate ukulele-like sound

Improvement Less delay in the system More accurate distance sensing RF transceiver with higher bps rate Remove Arduino Uno platform to reduce cost

Ethics The device is designed to be safe; no hazard posed to user

Acknowledgment Prof. Scott Carney Our TA : Jane Tu and Alex Suchko All staff of ECE Electronic Service Shop Thank You