1. Automatic Frequency Control with Handmade Electronic Guitar
Chih-Chieh Chen Lin (陳林志傑) , Wei-Yi Xiao(蕭惟毅) , Pei Shin(裴心) , Yi-Chien Wang(王逸謙)
Department of Physics , National Chung Cheng University , Chia-yi , Taiwan , ROC
Abstract
Pickup system
The most important part to this circuit is a constant-volume control amplifier. With a 32 Ohm impedance mini-earphones , it can clearly get the sound signal . The system works by only 1.5 V and current drawing is 7.5mA.
We combined an Electronic ear for our hand made electronic guitar. By the Fast Fourier Transformation ,we can get the sound`s frequency. We then use the arduino nano to control the stepper motor for automatic tuning. Compared with normal human ears, our automatic tuning system can get more accurate frequency.
GUI interface
Motor automatic control
We use A4988 to precise control of stepper motor rotation . The number of steps is determined by the error number from MATLAB. After Arduino nano get the error number from MATLAB, it will calculus the error number and decide turning direction of motor.
After pick up the voice signal, we use MATLAB to do Fast Fourier Transformation (FFT) found out the main frequency. We give the target frequency then it sent the error number to arduino
Conclusion
The automatic system has much way to add functions in the future . Now we can adjust the tuner by just flick the string . If we use the microphone that have narrower range of sound getting, the signal to noise ratio (SNR) will be enhanced, and our Automatic Frequency Control System can be promote.
Reference
ftp://plasma.twbbs.org/%E5%AF%A6%E9%A9%97%E6%8A%80%E8%A1%93/%E9%80%B2%E9%9A%8E%E5%AF%A6%E9%A9%97%E6%8A%80%E8%A1% pdf