Inspiration
We wanted to create a project that utilized polarized filters. As a team composed of a mechanical engineer and an electrical engineer, we decided that bringing in some Arduino/circuit elements would be a good way to do this.
Our plan for the hack was to utilize thermal sensor technology that would measure the temperature of the room and display a 2-digit temperature on an array of polarized filters. The filters allow for differing opacity levels depending on the angle at which two filters are held with respect to each other--hold them so their polarization is parallel, and you can see through the filters. Turn one filter 90 degrees, and most light is blocked out. The device would be mostly decorative in nature, and would be mounted on a window to allow natural light to come through the filters.
What it does
Our device takes a reading of the surrounding environment's temperature every second. For now, the device displays only the 1's digit of the temperature on a 7-segment display (the temperature in the room we were testing in was usually somewhere in the 70's, unless we were touching the sensor to warm it up). When the temperature read by the sensor hits or surpasses 75 degrees, a servo motor turns one of the polarized slides so that less light passes through the slides, making them appear darker. When the temperature drops back below 75 degrees, the slide turns back to its original position, giving the slides a brighter color in appearance.
How we built it
We went through many different iterations to construct our device: First, we built the circuit for the temperature sensor and printed its output on the computer screen. We then experimented with a 7-segment display to learn how it functions. We wrote code to display the digits 0 through 9 on the display, which would later be adjusted to other display types. Next we tried to mimic the 7-segment display pattern on an LED array. The array allows you to select individual pixels around the array, so we initially thought this would be the best way to test our concept before constructing a more complex model. We put the servo to work shortly after this, first making it complete a simple sweeping motion to learn how different code inputs influenced the motor's real-world behavior. Finally, we put everything we learned together. The temperature sensor currently reads the temperature of the room, displays the full temperature on the computer screen as well as the 1's place digit on the 7-segment display, and induces motion in the motor whenever the 75 degree mark is passed.
Challenges we ran into
There were three main challenges we ran into during our hack: 1) The LED array did not function as we thought it would. We thought that it would be possible to alter the state of every pixel regardless of the state of surrounding pixels. Unfortunately, because of the circuitry within the display, if one LED is activated within the row or column of a particular LED, then it is sometimes impossible to turn off this LED which meant we were unable to simulate most numbers on the display.
2) We took a long time to decide on the most practical approach for rotating the pixels Upon coming up with this idea, we played with concepts like electrophoresis and induction to rotate the pixels. We quickly realized that this would not be possible with our equipment and experience, so we decided to turn to motors instead. This is not quite practical if we were to scale our design up because of the high cost of servo motors.
3) An unknown complication with our circuit caused the temperature sensor to produce incorrect data. For a reason that we were never able to clearly figure out, our temperature sensor would not register the correct temperature of the room. This was quite a setback for us as it took us a long time to get our circuit functional again.
What's next for Thermally Induced Polarization: Electromagnetic Waves
Should we come across the resources to do so, we would like to scale our design up to include two digits of 14 pixels each. The full design would likely be greater than a square foot in area, and would require at least 14 motors.
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