Senior Design Expo 2019

Chaotic DJ
Ryan Arteaga, Jinglei Guo, Ishraq
Khandaker, Hongyi Li
Advisor: Professor David Vallancourt
The Chua’s Circuit, as shown in Figure 1, is
a circuit that is capable of producing chaotic
oscillation behavior. It consists of five
elements: a resistor, two capacitors, an
inductor, and a Chua’s diode (a negative
resistor). The Chua’s diode can be
implemented with two operational amplifiers
with positive feedback and six resistors,
connected in the system shown in Figure 2.
The inductor in the circuit can replaced with
a gyrator to obtain a “simulated inductor” as
shown in Figure 3. The Chua’s Circuit has
many applications. It can be used as a
physical source of pseudo random signals
and use synchronization studies regarding
communications systems [1].
The purpose of this Senior Design Project is
to explore the Chua’s Circuit design and its
effects on musical signals. Since the Chua’s
Circuit has a chaotic oscillating output
(Figure 6), it can be used to create a random
effect on musical input source. To achieve
this musical effect, the chaotic output of the
Chua’s Circuit is sent into an Arduino Uno
microcontroller. The microcontroller
controls a stepper motor in response to the
chaos from the Chua’s Circuit and changes
the potentiometer of a Dunlop Cry Baby Wah
Pedal. A music source is plugged into the
pedal and a random effect is added by the
motor-controlled potentiometer to produce
an output with a random wah effect.
Chua’s circuit is sent through a bypass
capacitor and a bias resistor, to create a DC
offset of oscillation signal.
The microcontroller processes the analog
input from the Chua’s Circuit and records the
number of zero crossings. For every 1000
counts, it will trigger the step motor for 200
steps and thus control the potentiometer of
the wah pedal. The motor will then reset the
potentiometer back to the original position
and restart the count for the zero crossings.
In conclusion, after careful analysis and
extensive simulations, the chaotic behavior
of Chua’s Circuit is successfully achieved
and applied into a musical system to produce
audible results with random wah effects.
References
[1]L. O. Chua, “Chua circuit,”
Scholarpedia . [Online]. Available:
http://www.scholarpedia.org/article/Chua_ci
rcuit. [Accessed: 4-Apr-2019].
[2]“Components for building Chua's
circuit,” www.chuacircuits.com . [Online].
Available:
http://www.chuacircuits.com/howtobuild2.p
hp. [Accessed: 4-Apr-2019].
[3]“How to build Chua's circuit,”
www.chuacircuits.com . [Online]. Available:
http://www.chuacircuits.com/howtobuild1.p
hp. [Accessed: 4-Apr-2019].
The Chua’s Circuit designed for this project
produced an output voltage of 5 Vp-p with a
dominant frequency around 300 Hz. The
microcontroller for this design, however, can
only take positive voltages through the
analog input channels. Thus, the output of the
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