Analog I/O and Enclosure

In this lab, there was an emphasis on analog input and “pseudo” output. In essence we took a sensor and used it as an input and then produced an output of light, speaker, or motor to produce an output. To begin the process of figuring out what I wanted to design for a final product I messed around with as many different sensors as I could to see which would best work for my final project. I started with a simple potentiometer that was in a circuit with an LED light. The input from the turn nob of the potentiometer controlled the brightness of the light based off of using ADC. Then I used a photo-resistor to control the brightness of another LED based off of how much or little light was being detected by the photo-resistor. I then also worked with another potentiometer, a pressure sensor, and used that to control the brightness of a light. Finally, I used another potentiometer that was a turn nob as well to control which direction a motor was turned in I ended up having a very chaotic layout but it helped me to decide which variable resistors I wanted to work with and which I didn’t.

I then narrowed down the selection of variable resistors that I wanted to work with to a potentiometer, a pressure sensor (potentiometer), and a photo-resistor. I used the potentiometer to control the brightness of an LED, just as I had done as the first step to this lab. I then made the pressure sensor control the pitch of different sounds the were emitted from a speaker. Initially the pitch of the sound was controlled by how much pressure was taken onto the pressure sensor, however, I noticed that this noise really irritated my ears as it did many others ears that sat near me. I then decided that I wanted to research how to make more pleasant noises emerge from a speaker. So instead of having the noise be a weird alien type sound, I made it go up the C major scale starting at C4 (middle C) all the way up to C5 (an octave higher). I made each of the different pressure jumps go up by 80 as I found what the maximum amount of pressure that I could emit was about 640, and dividing that by the amount of notes in the scale (8), gave me 80. From there I got a really fun pressure sensor that could control what note was played through the speakers and it definitely made for a challenge to try to go up and down the scale based off of how much pressure I applied. The final piece that I added to this breadboard was a photo-resistor that controlled what colors were emitted from a neopixel strip. If it was very dark, the color would be red; if it wasn’t very dark it would be blue; if it was about room lighting it was green, and anything brighter than that was yellow. The end product ended up looking like shown in the video.

After completing the rough draft, I realized that I didn’t really see a use for the potentiometer controlling the LED in the final product as it didn’t fit in with what I was trying to design. I decided to create a portable or non-portable desk accessory that was small and compact but interactive and fun. So, the first initial sketches for the final design are shown below:

The code for this project wasn’t incredibly difficult, however, it did require some looking up of how to get the specific notes to play through the speaker. Each of the individual notes needed to be defined before the set-up program was ran. Each of the notes had a different frequency they played at and that is the number associated with the defined notes. I then created a global array of each of the notes to use to cycle through later in the code. I plugged the neopixel strip into pin 3 on the Arduino board on the side of Digital where there is an ~ in front of the number indicating that it can be of a “pseudo” analog output. I then declare a variable to hold the neopixel information as well as other variables to hold what the status is for each of the variable resistors. Inside the set-up, I establish where the outputs are (3 and 5) as well as tell the neopixel strip to begin. In order to ensure that everything is being printed out correctly, I printed what the value being read in by the sensor was to the Serial console. I then used a sequence of if/else statements to produce the tone output to the speaker based off of the amount of pressure applied to the pressure sensor. Finally, I used a for-loop to cycle over all of the pixels on the neopixel strip to change the color of the strip based off of how much light was produced onto the photo-resistor. The map function was then used to turn this into a number between 0 and 255 and then that color was projected with the neopixel strip based off of the brightness. The code is shown below:

However, I didn’t see much of a place to fit the breadboard. So I then decided to use a collection of smaller prototyping boards to use as a connecting tool to get each of the pieces connected into the Arduino.

Once each of the prototyping boards were made I also had to make a prototype board to connect all of the powers for each of the different prototyping boards to power and each of the grounds to ground. After developing and connecting all of these pieces it was time to see how I wanted each of them to be assembled and into what kind of container.

After much contemplation about the creative ways I could make some sort of enclosure, I decided to keep it simple and elegant yet still maintain the compact nature. A simple box seemed the most logical to me. Initially I thought that the speaker would be shown through the side or the top of the box as shown in the sketch below. However, I decided that the aesthetic of the speaker didn’t really fit in with the elegant nature of the rest of my box. So instead, I decided to design small holes in the top where the speaker will go beneath to allow sound out of the box. I then decided to have an etched circle where the pressure sensor will sit and an etched circle around where the hole for the photo-resistor will be. I also had to consider where I wanted to put the neopixel strip. I thought that on the side so they could shine onto the table would be best.

I started out with using the MakerCase simple formatting program for developing the dimensions of my box. I then had to measure a hole for the power supply, a strip to allow the pressure sensor through to attach to the etched circle, a hole big enough for the photo-resistor, and little squares on the side for the neopixel lights to shine through. The first initial laser cutting sketch is shown below:

As you can see I made a few mistakes. The first mistake was the fact that I thought of the slit for putting the pressure sensor through to be the size of the actual strip that is attached to the pressure sensor and not the actual size of it (I forgot about the fact that it was soldered to the prototyping board – whoops!). The second mistake was that the power supply hole was on the wrong side of the box and it was way off from where the actual connection needed to be. To fix these errors I made the size of the slit to be the size of the largest part of the pressure sensor so it was able to fit through it, and made the power connector hole be on the other side and measure approximately where I wanted the hole to lay on the side of the box. The next laser cut on the cardboard is shown below. It was almost there.

I then decided to take a risk and start working with a slightly matte finish acrylic (which I got from Colorado Plastics), however, I didn’t realize that you didn’t want to take all the sticky paper on the outside off before doing the laser cutting so it ended up having a very smoky and dirty vibe as shown in the images of the box below. The positive of this box was that it finally had all of the elements in the right spot and it looked great aside from the smoke from the laser ruining the aesthetic.

The final cut I made ended up turning out perfect. I kept the sticky paper on the bottom side of the frosted acrylic and took it off the top to allow for the etching. The final design was ready. I cleaned up all the sides and added some of the acrylic glue to hold all the sides together except for the top to allow that to be removed to fix anything inside that may get shifted. I also got some sturdy double sided tape to hold down the pressure sensor onto the etched part of the box. I am really happy with the final design. It is compact and if need be, a battery can fit inside the box if they want it to be portable but as of right now I made it so that it is an external addition to the product.

I learned a lot from this project, there were a lot of things that I had begun to develop the basic knowledge on, but, I really feel like the concept of how to build a circuit came very quickly to me and I could visualize it in my mind, as well as the ability to understand the analog input and “pseudo” output. I was glad that I built so many at the beginning because it made for an easier time when I was actually putting together to product I wanted to have as the finished device. I also learned that it is crucial to have the correct size for the thickness of the material being cut when designing the boxes or you could end up with something that doesn’t work at all. Overall, I had a lot of fun building this project.