1. 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

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

3.  Frequency Beats ◦ Audio Visualizer  Low, Mid, High frequencies ◦ Utilizes Ferrofluid

5. HIGH ON Pulled Up LOW Pulled Down OFF V e > V b V e < V b

6.  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)

7.  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)

9. LatheHand-Wrapped

10.  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.

11.  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.

12. Homemade Ferrofluid Purchased Ferrofluid in Plexiglass Purchased Ferrofluid in Glass Container

14.  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

15.  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

16.  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

17.  Fourier Transform: transform signals between time and frequency.  Measure amplitude & frequency of audio input http://en.wikipedia.org/wiki/Fast_Fourier_transform

18. Audio Input  - Input signal  - Samples  The samples are gathered by measuring the voltage on the Arduino.  We take 512 samples

19.  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

20.  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

21.  Switches  Individual frequencies  Music

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