Pitchshifter: My experiment was creating a pitchshifter for the theremin. The way it works is while the mouse is manipulating pitch/amplitude continuously, pressing and releasing the "," and "." keys lowers and raises the pitch from the current point. An interesting aspect of this sort of interaction is that there's always a sense of "home" after releasing either pitchshifting button. This sense cannot be gained (precisely, that is) through the mouse interaction.

pitchshifter.pd relies on keyname-up.pd, a patch I created to sense the releasing of a key.

Puzzle (fourbutton.c) is a fun interaction with the four LED buttons on the AVR. Start the program, and you'll notice some led's are lit. Your goal is to light up all the buttons. This, unfortunately, is not a straightforward task; every button has random behavior that the user must ascertain and harness to her advantage.!

AVRsimon (avrsimon.c). My improvement was adding levels of play. The game starts with a pathetically simple sequence of 3, but soon progresses to a mind-numbing sequence of 20 lights and sounds!

For this lab, I modified meter.c to beep whenever any of buttons SW4-7 were pressed. SW4 corresponds to the lowest pitch, and every pitch increases up to SW7. After this, I constructed two buttons according to the first of the two given diagrams.

Compute C1

1. f = 1/(3RC)
2. Therefore, C = 1/(3Rf)
3. My desired frequency was f = 110 Hz. My measured resistance of a half-illuminated photoresistor was 180 kOhms.
4. C = 1/(3 * 110 * 180,000) = 0.168 microfarads.

Compute reasonable values for R4 & R5

I made the observation that if R4 = R5, it didn't matter what resistance was chosen; approximately 7.5 volts occur between the two resistors. Thus, I grabbed two 100 ohm resistors and was under way. Unfortunately, I didn't account for the fact that quite a bit of current was flowing through these resistors, and they heated up rather quickly! To fix this problem, I swapped in two 10 kOhm resistors. These seemed to do the job quite nicely.

Compute Pot and C2 values

As suggested by Carr I chose a 50 kOhm potentiometer. The first one was broken, which we didn't realize until we started testing with the oscilloscope. After substituting a nicer one, things moved smoothly from there.

As for calculating C2, I made the following computations:

1. RC = 1 / (2 * pi * f)
2. C = 1 / (2 * pi * f * R)
3. C = 1 / (2 * pi * 20 Hz * 50,000) = .159 microfarads

abc

1. For the best "playability," I used a 22k resistor for the FSR.

3. I used the vibraphone~ patch. First I hooked up a potentiometer to the overall frequency. This was a nice control because I could keep it at a particular frequency without having to maintain it (unlike, say, an FSR). I then connected the FSR to vibration frequency, which is fun to play around with because it dramatically affects the sound of the vibration. Finally, I connected the optical sensor to stick position.

accel

Answers within myaccel.pd.