Electrical traditional Chinese Instrument - Xun ECE 445, Team 9 Hongyi Li, Chi Zhang, Yujie Zhou Dec 10, 2018

Introduction An acoustically similar wind instrument to real Xun An innovative way to learn and practice instrument playing

Objectives Play out different notes under different hand gestures Change loudness under different blowing strength Respond quickly to players’ change in hand gestures and blowing

Block Diagram

Project Design Hardware: Power supply, buttons, air pressure sensor, micro controller, SD card, low-pass filter, audio amplifier Software: Program on the microcontroller that play the right piece of music on the SD card based on player’s input

Physical Design

Power System Function: Deliver power to the rest of the circuit Three major parts: Each part is composed of a 9V DC Alkaline battery and a linear regulator. Each part outputs 5V DC voltage to the rest of the circuit.

Power System - Current Verification

Sensor System The sensor system is used to take inputs from the player. There are two main player inputs that we need to monitor and utilize. Player’s hand gestures. Player’s breath.

Sensor System - Buttons Six button-like switches to sense the player’s hand gesture. Function: Generate voltage signals of different magnitude, high or low, when the button is pressed and released.

Button Schematic Output is LOW by default. Output is HIGH when pressed. Schematic for one button

Sensor System - Air Pressure Sensor Get air pressure as input. Output voltage between 0 to 5V, 1.8V in lab condition. Steady output.

Air Pressure Sensor Verification Connect air pressure to the microcontroller and wrote code to read the air pressure sensor input. Put the air pressure at rest in the 2070 design lab and record its output voltage. Take 100 samples, and 97 of them were 1.795 V, 3 of them were 1.800 V.

Air Pressure Sensor Verification We let the player blow into the air pressure sensor and we got an output voltage range from 1.795 V to 2.060 V.

Control System Input: Signals from the sensor system. Output: Music signals stored previously in the SD card to the audio output system.

Control System - SD card The SD card stores all the music recordings of the real xun. All the music recordings should be in the following format: 8-bit resolution 16 kHz sampling rate mono channel PCM unsigned 8-bit

Control System - Microcontroller Connect to all sensors Read data stored in the SD card Select data based on sensors’ input and give it to audio output system

Microcontroller - flow chart

Control System Verification verification code: Data transfer time: The data transfer time is approximately 7ms.

Control System Verification Note Correctness: Real Xun’s Sound Our Xun’s Sound 483.31HZ 484.87HZ

Audio Output System Achieve two tasks: Filter the signal to reduce noise Amplify the output music signal so that it can be played on a speaker

Audio Output System - Filter Keep components of the signal under 16 kHz the same Attenuate the components of the signal above 16 kHz

Audio Output System - Audio Amplifier Can amplify the signal 40 times in magnitude

Audio System Verification - Filter Pass signals at 1kHz Peak-to-peak voltage: 3.44 V Attenuate signals at 55kHz Peak-to-peak voltage: 1.49 V

Audio System Verification - Amplifier Testing: Achieve 40 times of amplifications of a signal with 100mV (peak-to- peak) Output signal has peak-to- peak voltage of 3.99V

Review: Design and Verification Components that we tested and verified successfully: Alkaline batteries and linear regulators All six buttons and the air pressure sensor Microcontroller and the uploaded program RC filter for noise attenuation Audio amplifier

Video

Conclusion Our project meets all high-level requirements: Output correct sound pitch Output four different volume levels Response time is tolerable.

Future Work Obtain higher similarity with the real sound of the xun Improve sound control with respect to air pressure sensor Implement an instructive LED system

Thank you!