Gadgetry Class

• Helping hard of hearing individuals tell where a sound is coming from.
• Help military personnel tell where shots are coming from. Ears system by QinetiQ does a good job (heading and distance) for ~$8,000 a unit! Based on the video, it uses the time delays between the shock wave of the bullet and the sound of the muzzle blast to tell distance and 4 microphones to tell angle. Interesting…wonder how well it deals with echos?

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• Ultrasonic Localization (eventually used Kalman Filter). Cool project from Cornell Senior Projects!

• Another Cornell project that used 4 microphones

• http://www.ian.org/HD-Clock/

1. Set up motors
   1. Get mirrors mounted on motors
   2. Attach 22-gauge? wires to motors and solder into board
   3. Get PWM output working
      1. (16-bit I think…probably little difference in motor speed between ticks, but it'd be an interesting test)
      2. Be sure to have it set at a high frequency to limit audible noise
2. Read in joystick
   1. Have a global joystick variable that gets updated on an interrupt with a change in ADC
      1. Range should be 0 to 4096 w/ 2048 being center on each x and y
   3. Calibrate
      1. Measure angles of each mirror, try to match them as close as possible
      2. Do a linear mapping of motor PWM to RPM for each motor
      3. Should be able to generate accurate images that correspond to Processing now
3. Create Processing app to demo audio too and release interactive easily-usable version

• Joystick ranges from 3300 to 230 on each side w/ about 20 ticks of noise on each side and not full range!! Middle is 1770 for each. I thought 2.2K on Vcc would remedy this, but maybe I'm wrong.

• Use PWM (with microcontroller) and 4 mirror setup. Not sure what to do about red laser or diffractors…
• Leyanda.de Project. Talks about effective PWM operation and using mosfet for laser switching.
• http://www.instructables.com/id/Four-Motor-Laser-Spirograph/4 Motor Setup! THE WAY TO GO :)
• Another option. He measured each angle of mirror using some math after the fact. Kinda cool!
• Take pictures of it on long exposure to get the full effect of the shapes (especially for higher numbers of mirrors)
• Hypotrochoid paper (CS guy)
• Plotting spirographs
• The landmark paper on this is Frank Farris' Paper, "Wheels on Wheels on Wheels"

where n is the number of engaged wheels: wheel k has its center fixed on a point of the circumference of wheel (k-1). On each wheel, a_k is related to the radius, n_k to the rotation speed, and \theta_k is an initial phase angle. Farris demonstrated that the z(t) curve has g-fold rotational symmetry if all the pairwise differences |n_k-n_j| have g as their greatest common divisor.

So, the radius here is the degree offset of the mirror (how wide of a circle it makes), and Nk is indeed the rotation speed. So, we want to have mirror angles as similar as possible to get good shapes.

https://www.dropbox.com/s/dxcw98u3o90fx0t/spirolab_application.windows32.zip?dl=0

• Holding SHIFT & CTRL follows line from center outwards. Keeps relationship between the two speeds constant

• Incorporate controlP5. Reza's supershapes is a good similar example
• Not sure how accurate the tones actually are to the shapes. The beats seem to line up though with only a little lag.
• Fix the transitions between shapes so that it doesn't create ugly line
  • Maybe use integrator to smooth it out?
• Adjust low notes so they are louder. However, Minim fails to do amplitude changes that quickly over multiple notes I'm thinking. It does it for one just fine though!