Frequency Beats:Final Report8 April 2014

Team Couch Street Alex Arlint Jake Nylund Kevin Ratuiste Robert Rodriguez

Academic Advisor: Joseph HoffbeckIndustry Representative: John Turner – Impinj, Inc.Client: William Taylor - Student

Introduction What Is it? Control Circuit Electromagnets Display Software Demonstration Conclusion

Overview

Frequency Beats◦ Audio Visualizer

Low, Mid, High frequencies◦ Utilizes Ferrofluid

What is it?

Circuit SchematicElectromagnet(Low-Range)

Electromagnet(Mid-Range)

Electromagnet(High-Range)

Arduino

12V

100ё

33uF

Low-Range Out

100ёMid-Range Out

100ё

33uF

High-Range Out 33uF

Audio Input

Powered Speaker

LPF

LPF

LPF

11

1213

BAT42 BAT42 BAT42

2N3904IRF3205

3.3V

10kё

10kё

2N3904IRF3205

10kё

10kё

1

2

3

1

2

3

1

2

3

1

2

3

2N3904

IRF3205

10kё

10kё

1

2

3 1

2

34.7kё

4.7kё

4.7kё

3.3kё

2.7kё

100uF 1kё

1kё

Audio Source

3.3V

Vcc

NC

NC

NC

From Arduino

Electromagnet

100ё

33uF

LPF

BAT42

2N3904IRF3205

10kё

10kё

1

2

3 1

2

34.7kё

3.3kё

2.7kё

12V3.3V (From Arduino)

NC

Control Circuit

HIGH

ON

PulledUp

LOW PulledDown

OFF

Ve > Vb

Ve < Vb

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)

Electromagnets

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)

Electromagnets (Cont.)

Electromagnets (Cont.)

Electromagnets (Cont.)

LatheHand-Wrapped

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.

Display

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.

Display (Cont.)

Display (Cont.)

Homemade Ferrofluid

Purchased Ferrofluid in Plexiglass

Purchased Ferrofluid in Glass Container

Electromagnet + Display

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

Software/Arduino

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

Software – cont.

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

Arduino Programming

Fourier Transform: transform signals between time and frequency.

Measure amplitude & frequency of audio input

http://en.wikipedia.org/wiki/Fast_Fourier_transform

FFT – Cooley-Tukey

Sampling

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

Using the output

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

The PWM

Switches Individual frequencies Music

Demonstration!

Introduction What Is It? Control Circuit Electromagnets Display Software Demonstration Conclusion

Conclusion

QUESTIONS?