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University of Portland
School of Engineering
5000 N. Willamette Blvd.
Portland, OR 97203-5798
Design Document
Frequency Response Audio Visualizer
Team Members:
Jake Nylund (Fall Team Lead)
Kevin Ratuiste (Spring Team Lead)
Alex Arlint (Treasurer)
Robert Rodriguez (Secretary)
Industry Representatives:
John Turner – Impinj, Inc.
Faculty Advisors:
Dr. Joseph Hoffbeck
Clients:
Will Taylor – Student
Phone 503 943 7314
Fax 503 943 7316
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REVISION HISTORY
Rev.
Date
Author
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1 Nov 2013
Team
First draft submitted to advisor
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8 Nov 2013
Team
Second draft submitted to advisor
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Table of Contents
REVISION HISTORY ........................................................................................................................................ 2
INTRODUCTION ............................................................................................................................................. 5
Figure 1: Front View Concept Sketches ................................................................................................ 5
HIGH LEVEL ARCHITECTURE .......................................................................................................................... 6
Figure 2: High Level Architecture .......................................................................................................... 6
HARDWARE AND SOFTWARE DESIGN .......................................................................................................... 7
Figure 3: Overall Circuit Schematic ....................................................................................................... 7
User Interface ........................................................................................................................................... 8
Figure 4: User Interface Component Diagram ...................................................................................... 8
Biasing Circuit............................................................................................................................................ 8
Figure 5: Biasing Circuit ......................................................................................................................... 9
Figure 6: Input/Output Signal Plot ........................................................................................................ 9
Arduino Due Microcontroller .................................................................................................................. 10
Figure 7: Arduino Due ......................................................................................................................... 10
Software Component .............................................................................................................................. 11
Figure 8: General Signal Process ......................................................................................................... 11
Electromagnet ......................................................................................................................................... 13
Figure 9: Electromagnet Control Circuit ............................................................................................. 13
Mechanical Components ........................................................................................................................ 14
SYSTEM TEST PLAN ..................................................................................................................................... 14
Microcontroller ....................................................................................................................................... 14
Electromagnet/Ferro Fluid Display ......................................................................................................... 15
Figure 10: Electromagnet Test Switch ................................................................................................ 15
DEVELOPMENT PLAN, MILESTONES, ASSUMPTIONS, RISKS, AND FACILITIES ............................................ 16
Development Plan................................................................................................................................... 16
Figure 11: Overall Design Process Diagram ........................................................................................ 16
Milestones............................................................................................................................................... 18
Assumptions............................................................................................................................................ 18
Risks ........................................................................................................................................................ 18
Facilities .................................................................................................................................................. 19
FINAL BUDGET............................................................................................................................................. 20
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Table 1: Budget Breakdown ................................................................................................................ 20
CONCLUSION............................................................................................................................................... 20
GLOSSARY.................................................................................................................................................... 21
REFERENCES ................................................................................................................................................ 21
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INTRODUCTION
Frequency Beats, the name given to this project, is a frequency response audio
visualizer. The overall goal of the device is to visualize the spectrum of an audio signal. The
input will be an analog line level audio signal connected via a standard 3.5mm headphone jack.
This signal will enter the microcontroller where it will be processed and filtered to separate the
various frequencies in the audio signal. Implementing the filters digitally allows more flexibility
in how the microprocessor will process the signal as well as the resulting action or response.
Once the frequencies of the audio signal are separated, they will be output to the
electromagnets, which, in turn, will manipulate the ferromagnetic fluid creating a visual
representation of the audio signal.
The final result should resemble the concept sketches provided in Figure 1, below. The
front view, shown in the second quadrant, illustrates the front side of the apparatus; this
consists of three plexiglass chambers partially filled with ferrofluid and an electromagnet
suspended above each chamber. The first quadrant shows an enhanced view of one of the
plexiglass chambers and the electromagnet above it; this gives a closer look at how each
chamber will be positioned. In the fourth quadrant, the view is enhanced further, zooming into
just the plexiglass chamber and the ferrofluid, undisturbed. The third quadrant shows the same
chamber with the type of actuation expected when the electromagnet receives current.
Figure 1: Front View Concept Sketches
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The following sections of this document will include which specific tools and
technologies the team will utilize in the production of the project as well as detailed
descriptions of how the project will physically be laid out, how the project will be wired, and
how each component will interact with the other components. Additionally, within each
section, there will be some recurring words that the team assumes the reader understands; as a
precaution, those words are defined in the Glossary at the end of the document. These
electronic components will be utilized in the construction of the Frequency Beats project.
HIGH LEVEL ARCHITECTURE
Figure 2 below shows the high level architecture of Frequency Beats. The key
component of this project is the Arduino Due, which takes the audio signal at its input, splits it
into three different frequencies using Fast Fourier Transform (FFT), and then outputs the three
frequencies. The three frequencies are low-range, mid-range, and high-range. The outputs of
the Arduino are smoothed out by a low pass filter and then used to control the electromagnets
by a Darlington Pair. FreqBeat utilizes two power supplies, a 6.5A 12V for the electromagnets
and Arduino, and a 3.3V for the biasing circuit
12V Power
Supply
Electromagnet
(Low-Range)
3.3V Power
Supply
LPF
Audio Input
Electromagnet
(Low-Range)
Electromagnet
(Low-Range)
TIP102
Darlington Pair
Low-Range Out
Biasing
Circuit
Arduino
Mid-Range Out
LPF
High-Range Out
TIP102
Darlington Pair
LPF
Powered
Speaker
TIP102
Darlington Pair
Figure 2: High Level Architecture
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HARDWARE AND SOFTWARE DESIGN
This section will go into the multiple components that make up the project. Both
hardware and software designs will be discussed. Figure 3 below shows the overall schematic of
Frequency Beats.
12V
Electromagnet
(Low-Range)
3.3V
Electromagnet
(Mid-Range)
Electromagnet
(High-Range)
GPB554B05BB
TIP102
2
LPF
1
GPB554B05BB
5K
150
Biasing Circuit
Audio Input
1K
2
100uF
1K
Arduino
22 Low-Range Out
Mid-Range Out
23
High-Range
Out
24
3
2
TIP102
LPF
1
GPB554B05BB
5K
150
3
TIP102
2
LPF
1
Powered Speaker
5K
150
3
Figure 3: Overall Circuit Schematic
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User Interface
The user will plug in their audio signal via a 3.5mm standard line level audio cable on the
back side of the project device. Once connected, the user presses play and watches the audio
visualization of his or her music choice on the front side of the device. Alternatively, the user
may press one of the three buttons present on the front of the device to activate the respective
electromagnet in order to manipulate the ferromagnetic fluid without audio. Additionally, the
user will have the option of plugging in powered speakers to hear the music while viewing the
ferrofluid displays. This will be accomplished by using a 3.5mm headphone splitter at the
output of the IPhone The following figure shows the three buttons and audio cable that the
user will be able to interact with.
Figure 4: User Interface Component Diagram
Biasing Circuit
The output signal from a team member’s Iphone will be used as the input for the Arduino Due,
whose analog input pins measure from ground to a maximum value of 3.3V. Since the Iphone’s signal is
observed via oscilloscope to be between -1.1V and 1.1V the signal must first be DC offset so that it ranges
from 0V to +3.3V. To accomplish this, the team will make use of a simple biasing circuit, which uses the
voltage divider principle.
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This was simulated using PSpice to verify its correct operation.
Figure 5: Biasing Circuit
Below is the plot of the sinusoidal input (red) and the output (green), which is offset by 3.3/2 or
1.65V so that it is a purely positive signal.
Figure 6: Input/Output Signal Plot
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Arduino Due Microcontroller
The primary digital component that will be utilized in our design is the Arduino Due,
which is a microcontroller board based on the Atmel SAM3X8E ARM Cortex-M3 CPU. It is the
first Arduino bard based on a 32-bit ARM core microcontroller. It has 54 digital input/output
pins, 12 analog inputs with 12 bits of resolution each, and 12 PWM output pins.
This component will be used to digitally filter the input audio file, separating it into lowrange, mid-range, and high-range, then output those 3 signals to individual audio amplifiers.
Figure 7: Arduino Due
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Software Component
Figure 8: General Signal Process
Figure 8 shows the general process that the signal will undergo as it is sampled by the Arduino.
Simply stated the Arduino will continually sample the input on one of the Digital Input pins
using a Loop. From there using Fast Fourier Transform (FFT) the signal will be separated as Low
pass, Band pass, and High pass filters. Each signal will be output to three different digital output
pins.
The following is a list of the functions the Arudino will be performing.
init()
Initialize I/O pins to being the sampling and output process
sampleLoop()
This loop will continually sample the audio input in Analog format. Using FFT it will split
the signal and output onto three separate pins for High, Low , and Band pass frequencies.
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Sample code for the FFT algorithm can be found here: http://www.drdobbs.com/cpp/a-simple-andefficient-fft-implementatio/199500857
FFT will output several complex numbers, or rather a real and complex part of each
number in the form of doubles. Each of the outputs will be sent to each of their corresponding
output pins as a combine value, putting the real and complex portions into one value. The
values will be continually recalculated in the loop to continually send to their respective pins,
for example pins 22, 23, and 24 on the Arduino. The signal will then pass throw a low pass filter
in order to create the proper DC current output for the circuit.
delay()
In order to achieve real time audio output that produces a response in the
ferromagnetic fluid in time with the music there will need to be a precisely tuned delay. The
specific delay will be modified to produce the best time output. This buffer will allow the
calculations to be done and put as smoothly as possible.
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Electromagnet
Power Supply
The signal from the Arduino is not strong enough to drive the electromagnet.
Thus, the electromagnets will be powered by a 6.5A, 12V power supply.
Control
The signal from the Arduino will be used to determine when the electromagnet
is on or off. A TIP102 Darlington Pair, which acts as the “on/off” switch for the
electromagnet, will be controlled by the signal from the Arduino. Since the maximum
current from the Arduino is 40mA and current from the electromagnet will be at most
6.5A, a Darlington Pair had to be used in order to achieve a transistor with large enough
current gain. When there is current seen at the base of the TIP102, current from the 12V
power supply is able to flow through the electromagnet, thus turning the electromagnet
on.
12V
Electromagnet
(Low-Range)
2
TIP102
From Arduino
1
5K
150
3
Figure 9: Electromagnet Control Circuit
Build
The electromagnet will be made with of at least 50 feet of 22 gauge magnet wire
and wrapped around a 1/2” diameter metal core that is 5 inches in length. At 50 feet the
internal resistance of the wire is 0.65Ω. More than 50 feet of wire maybe used in the
case that more turns are needed to produce a strong enough electromagnet. The
electromagnet will be mounted above the ferrofluid display.
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Mechanical Components
Our project will incorporate several simple mechanical devices. One of which will be the
casing that houses the Ferro fluid. For this, we plan to use plexiglass cylinders, each with a
diameter of approximately 2 inches and height of 5 inches. The electromagnetic will be
mounted above the cylinder. Additionally, we will construct a wood base to mount the three
Ferro-fluid displays as well as the Arduino and support circuitry. The base will be approximately
18 inches long and 6 inches wide.
SYSTEM TEST PLAN
Microcontroller
In order to adequately test the Arduino Due microcontroller to verify that the digital
filters are functioning as desired, the following steps will be executed:
1.) Set up a breadboard with 3 different LEDs, one for indicating low
frequencies (20Hz – 400Hz), one for mid-range frequencies (400Hz – 5.2KHz),
and one for high frequencies (5.2KHz – 20KHz).
2.) Manufacture a test signal comprised of 5 seconds of low frequency data
(20Hz – 400Hz), 5 seconds of mid-range frequency data (400Hz – 5.2KHz),
and 5 seconds of high frequency data (5.2KHz – 20 KHz).
3.) Use the manufactured signal as an input to the Arduino.
4.) If the LEDs corresponding to the expected frequencies, the Arduino is
functioning properly.
5.) Otherwise, re-examine the Arduino code for potential errors and then redo
the steps above until the desired result is achieved.
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Electromagnet/Ferro Fluid Display
Testing of the electromagnets on each of the three displays will be done as follows:
1.) Each electromagnet will have a pushbutton switch that will force it to turn
on. The circuitry is show below in figure
12V
Electromagnet
(Low-Range)
GPB554B05BB
From Arduino
TIP102
Figure 10: Electromagnet Test Switch
2.) When the button is not depressed, the electromagnet operates as dictated
by the Arduino.
3.) When the button is depressed, the electromagnet is shorted to ground, thus
allowing current to flow and the electromagnet to turn on.
4.) If the electromagnet does not work when the button is depressed, check the
following:
a. Is the power supply on and working correctly?
b. Are there any shorts in the system?
c. Check each individual component for failures.
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DEVELOPMENT PLAN, MILESTONES, ASSUMPTIONS, RISKS, AND FACILITIES
Development Plan
Figure 11: Overall Design Process Diagram
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Below are explanations of each step in the design process show above.
Project Proposal
Team Couch Street developed the idea for a ferrofluid audio visualizer by combining two
different project ideas; one to work with ferrofluid, and the other to work with software to
digital process audio input. The appeal of this project is the combination of skills required to
successfully design and build a prototype.
Function Specifications
This is the document that details the conceptual design of the ferrofluid visualizer. This
includes primarily the goals, conceptual sketches, and plan for production.
Design Document
This document should allow any reader to reproduce the results of our prototype simply
from this document.
Testing Ferrofluid and Electromagnets
In order to determine the specific calculations for voltage and current requirements, the
team tested multiple electromagnets and ferrofluid with different viscosities. These tests lead
to changes and finalized decisions in the Design Document.
Software Development
To meet the required deadline, team members Robert Rodriguez and Jake Nylund will
being the software aspect of the project over Christmas break. To best get a handle on the
language and chip architecture it is necessary to start as early as possible.
Construct Housing for Ferrofluid and Base
As discussed in the Assumptions portion of this document, the team assumes we will
have the assistance of Alan Hansen in the construction of our ferrofluid containers and base for
our prototype. This will be constructed of Plexiglas and plywood respectively.
Construct Electromagnets
This has its own section as the construction of an efficient and powerful electromagnet
takes significant time and focus, and the team requires three of them.
Test FFT with Board and LED’s
After finishing the software development stage, it will be necessary to test the Fast
Fourier Transform (FFT) algorithm to ensure that it properly splits the signals into High, Band,
and Low pass frequencies. The team will use LED’s and specific High frequencies, Midband, and
Low frequencies individual to test the Arduino’s DSP program.
Assemble and Test First Ferrofluid Display
At this point in the design process everything should be ready to assemble into one unit.
The Arduino will pass a signal through the OP Amp which, with the increase in voltage, will
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power the Electromagnet, which will in turn cause the ferrofluid to respond in time to the audio
signal.
Test Second and Third Ferrofluid Displays
With one fully functional Ferrofluid Display the team anticipates a much quicker
turnaround time in production of the second and third ferrofluid displays. The bugs should be
fewer and worked out faster.
Test and Debug
By this point everything will be assembled. Final Testing stages will ensure that all
portions of the visualizer are working together as expected.
Founder’s Day Presentation
The team will present the project to faculty and students at the University of Portland.
Milestones
The milestones for the project have been stated previously in the Functional
Specifications Document. Please refer to that as there have been no changes in the milestones.
Documentation can be found at: http://wordpress.up.edu/egr13couchstreet/visualizer-status/
Assumptions
There are several assumptions that the team is making about the construction phase of
the project.
 Alan Hansen will be available to help with the construction of the base and
container for the ferrofluid
 The Arduino Due will function as stated in the specifications sheet listed on the
Arduino website.
 All hardware will be available and function properly
 Some hardware components, such as those necessary in the construction of the
OP Amp circuit, will be available from the University and not necessary to
purchase.
Risks
The risks for the project have been stated previously in the Functional Specifications
Document. Please refer to that as there have been no changes in the risks. Documentation can
be found at: http://wordpress.up.edu/egr13couchstreet/visualizer-status/
Below is a comprehensive list of the anticipated design challenges the project could face
as well as how the challenges could be overcome:
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Challenge 1: It could be difficult to find a power supply that produces enough for each
electromagnet and then also have the microcontroller coordinate where the current goes. If a
single, suitable power supply cannot be found, then it would also be possible to use smaller,
separate power supplies that would each be easier to control and locate individually.
Challenge 2: There is a possibility that the synthesized ferrofluid reacts differently or
more inconsistently than expected. In this situation, it would be best to simply buy ferrofluid
from a chemical supplier so that the team’s focus is not on the chemistry of ferrofluid; the main
focus should be on the hardware/software design and construction of the visualizer.
Challenge 3: The team may run into issues constructing certain hardware components,
such as the Plexiglas containers for the ferrofluid or the electromagnets themselves. In such a
situation, there are multiple resources available, including the faculty at the University of
Portland, the design project technicians, or at worst, the library and online sources to help
direct the team in the right direction.
Facilities
Throughout the experimentation, design, and construction process of our project will
make use of the bench space and equipment in Shiley 306. As far as software requirements,
there are open source microcontroller environments and/or MATLAB on any Engineering build
computer. The equipment used will likely be limited to a soldering iron, ICs, and various hand
tools for construction.
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FINAL BUDGET
After determining what circuits and components would be necessary to construct the project,
the team decided on a comprehensive parts list and the associated costs. This breakdown can be seen in
the table below.
Table 1: Budget Breakdown
Material
2-1/4" OD x 2" ID x 36”
Plexiglass tube
2.5” Plexiglass disk
Arduino Due
½” x 6” metal core
250ml ferrofluid
3.5mm female adapter
TIP102
12V power supply
3.3V power supply
Display base parts (Plywood)
Magnet wire 16AWG spool
(500’ each)
Price
12.50
Quantity
1
Total Cost
12.50
12.50
40.00
10
58.25
5
0.95
< 50.00
<25.00
20.00
20.00
1
1
3
1
1
3
1
1
1
1
12.50
40.00
30.00
58.25
5.00
2.85
<50.00
<25.00
20.00
40.00
TOTAL 296.10
CONCLUSION
The ferromagnetic fluid audio visualizer is a different way of seeing different frequencies
used in different types of music. It will show the low, middle and high frequencies ranges by
processing the sound form a standard 3.5mm headphone jack, used by almost all music players
and splitting the signal accordingly.
In order to succeed on this project the team will need to continuously work to stay on
schedule. The schedule that we have laid out is reasonable so long as time is used efficiently.
The real key is to effective testing and debugging. In terms of software it is important to ensure
the signal is processed correctly and then output to the proper pin. For hardware the key part is
the construction of the OP Amp circuit and Electromagnet. Teamwork will keep the project on
track.
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GLOSSARY
IC: (Integrated Circuit) is a microelectronic circuit manufactured on a thin substrate of a
semiconductor material such as silicon.
Microcontroller: is a small computer on a single integrated circuit containing a processor core,
memory, and programmable input/output peripherals.
Arduino: is a single-board microcontroller to make using electronics in multidisciplinary
projects more accessible.
Electromagnet: is a type of magnet in which the magnetic field is produced by electric current.
Ferrofluid: is a liquid which becomes strongly magnetized in the presence of a magnetic field.
LED: (Light Emitting Diode) A semiconductor diode that emits light when a voltage is applied to
it and that is used especially in electronic devices (as for an indicator light).
REFERENCES
http://elm-chan.org/works/akilcd/report_e.html - audio specturm monitor
http://forum.arduino.cc/index.php/topic,37689.0.html
http://playground.arduino.cc/Main/ArduinoSynth
http://arduino.cc/en/Main/arduinoBoardDue
https://www.youtube.com/watch?v=a_flWeIdoBg
http://abhishekjainnsit.blogspot.com/2012/10/digital-filters-on-arduino.html - Digital Filters
http://forum.arduino.cc/index.php?topic=42510.0 – Arduino Digital Filter
http://www.paulodowd.com/2013/06/arduino-38khz-bandpass-software-digital.html - 38kHz
Ban Pass Filter
http://forum.arduino.cc/index.php/topic,42635.0.html – Low Pass Filter Design
http://www.drdobbs.com/cpp/a-simple-and-efficient-fft-implementatio/199500857 - FFT
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