Wednesday, October 7, 2009

Physical Computing Lab: Creating Sound and Movement

The focus of last week's Physical Computing lab was to learn how to use more complex analog  actuators that can produce sound and motion. This four-part lab included: (1) set-up and testing of two different configurations for working with a servo motor (one using the servo library, the other sans the library); (2) set-up and testing of two different sound generating sketches.

All of these activities (except for the first servo lab) required the use of special libraries, namely the servo and a tones libraries. Here is a link to the detailed lab descriptions (servo | sound). Below you will a video of the fruits of my labor, followed by a brief overview of the issues that I encountered.

For the most part this lab was straightforward. I did not encounter issues with either of the servo labs. That said, I found it interesting to be able to understand how the servo motor works without an analog output and the library. Its position is determined by the length of time of the signals it receives. Unfortunately, there is no standard pulse-length to turn-ration relationship that holds true across different types of servo motors. To translate pulse length to turn ratio one must test different types of servo motors individually.

Another important consideration is that since servo motors rely on pulses, we must set a short interval between the "pulses" so that the motor can differentiate when one pulse begins and another ends (this sounds pretty obvious but I'm sure I will forget). To simplify our lives,  if you use the servo library you can avoid having to deal with all of the considerations that I listed above.

Moving on to the sound lab, here I did encountered one issue. When I first set-up the lab I was not able to get any sound to come out of my speaker - actually sound was coming out but it was not loud enough to be heard among the ruckus of the physical computing lab. Luckily, some other students had previously encountered the same issues. They pointed out to me that they resolved similar problems with their speakers by changing the resistor. Once this change was made the sound came out loud and clear.

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