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
HIGH ON Pulled Up LOW Pulled Down OFF V e > V b V e < V b
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)
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.
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
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 Hz 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->
Switches Individual frequencies Music
Introduction What Is It? Control Circuit Electromagnets Display Software Demonstration Conclusion