Transcript Frequency Beats: October Program Review

Team Couch Street
Alex Arlint
Jake Nylund
Kevin Ratuiste
Robert Rodriguez
Academic Advisor:
Joseph Hoffbeck
Industry Representative:
John Turner – Impinj, Inc.
Client:
William Taylor - Student
Introduction
 What Is it?
 Control Circuit
 Electromagnets
 Display
 Software
 Demonstration
 Conclusion


Frequency Beats
◦ Audio Visualizer
 Low, Mid, High frequencies
◦ Utilizes Ferrofluid
Electromagnet
(Low-Range)
BAT42
Electromagnet
(Mid-Range)
BAT42
BAT42
Electromagnet
(High-Range)
3.3k
12V
3.3V
2.7k
2
LPF
100
33uF
1
2
10k
3
2N3904
4.7k
IRF3205
1
10k
NC
3
NC
Audio
Source
Audio Input
100uF
1k
Vcc
3.3V
Arduino
11 Low-Range Out
Mid-Range Out
12
13 High-Range Out
2
LPF
100
33uF
1k
1
3
2N3904
4.7k
2
10k
10k
IRF3205
1
3
NC
Powered Speaker
2
LPF
100
33uF
1
4.7k
2
10k
3
2N3904
10k
IRF3205
1
3
12V
3.3V
(From Arduino)
3.3k
BAT42
2.7k
Electromagnet
OFF
ON
NC
From Arduino
LPF
100
33uF
HIGH
LOW
Ve > Vb
2
1
3
2N3904
4.7k
Ve < Vb
10k
10k
Pulled
Up 1
Pulled
Down
2
IRF3205
3

Initial Design Plan
◦ 110 feet of 22 gauge magnet wire around .5”
diameter metal core 5” in length.
◦ Would provide internal resistance of 1.77Ω.
◦ Hand wrapped

Final Design
◦ Approx. 270 feet of 26 gauge magnet wire around
0.25” diameter iron core 5” in length.
◦ Provided internal resistance of ~13Ω.
◦ Wrapped using a Lathe.
 Kept coils tight and close together.
 Slow process (2+ hours per magnet)

Reasons for Design Change
◦ Increased length necessary to attain stronger
magnetic field.
◦ Diameter of core change selected based on
availability.
◦ Lathe vs. Hand-Wrapping Magnets
 Lathe was a vastly slower process, but ultimately
yielded a superior product (as seen on the next slide)
Hand-Wrapped
Lathe

Initial Design Plan
◦ Plexiglass cylinders with 2” diameter and 5” height.
◦ Filled with “homemade” ferrofluid.
 Toner mixed with vegetable oil.

Final Design
◦ Glass cylinders with 1” diameter and 2.5” height.
◦ Filled with ferrofluid (Ordered online) and encased
in water for better reactivity.

Reasons for Design Change
◦ Homemade ferrofluid was unforeseeably difficult to
manufacture
 Consistency not correct.
 Not reactive enough to magnetic field.
◦ Plexiglass seemed to allow the ferrofluid to stick to
the sides, thus “mucking” up the display.
Homemade
Ferrofluid
Purchased
Ferrofluid in
Plexiglass
Purchased
Ferrofluid
in Glass
Container

Initial Design Plan:
◦ Fast Fourier Transform algorithm
◦ Quickly sample audio signal
◦ Compute amplitude of each frequency in audio signal

Problems with the Arduino Due

Contingency Plan:
◦ MSGEQ7 IC – does frequency analysis of audio signal
and outputs 7 bands
◦ Arduino combines bands and scales values

Final Design
◦ Same as initial design plan
◦ Took weeks to troubleshoot
◦ Adapted customized library to be compatible with
IDE instead of using premade libraries
 Used sample implementations of FFT and other source
codes as a model for custom library


Init()
sampleLoop()
◦ Continuously sample the analog audio input
◦ Perform FFT, producing real and imaginary parts for
each frequency bin
◦ Take magnitude of each frequency bin
◦ Combine magnitudes into three frequency bands
 80Hz-255Hz, 255Hz-6kHz, 6kHz-12.5kHz
◦ Select highest magnitude from each band
◦ Output to LPF as a PWM signal to smoothed into a
DC signal for control circuit
◦ Repeat


Fourier Transform: transform signals between
time and frequency.
Measure amplitude & frequency of audio input
http://en.wikipedia.org/wiki/Fast_Fourier_transform




Audio Input
- Input signal
- Samples
The samples are
gathered by measuring
the voltage on the
Arduino.
We take 512 samples

Output array of 256 samples or bins
◦ The FFT gives half of the input

Each bin is approximately an 85Hz sample
range
◦ Bin 1 would be 85-170Hz roughly

Bin 0 is a reference bin and causes some
noise for our calculations

Each value initially calculated by the FFT is
scaled to a value between 0 and 255

63->

127->

191->
http://arduino.cc/en/Tutorial/PWM



Switches
Individual frequencies
Music








Introduction
What Is It?
Control Circuit
Electromagnets
Display
Software
Demonstration
Conclusion