MiniGroupProject02 | Blog Journal

COSC 594

INTERACTIVE SWITCHES

LOW-TECH INPUT: COKE CANS

Overview

For this project we were tasked to use low-tech materials to make primary input device. We decided to make use of coke cans as touch-sensitive switches to control the blinking of LEDs. They act as capacitive sensors and sense the change in capacitance. This application of advanced capacitive sensing is used in many new touchscreens devices. Also, the paper towel rolls is wrapped in aluminum foil that is taped down. On top of that is a sheet of paper that is taped down. There is then a sleeve of aluminum foil attached to another sheet of paper. The two pieces of aluminum foil separated by the paper creates a capacitor. The more aluminum foil area that overlaps the higher the capacitance. The outer aluminum foil and paper slide to adjust the capacitance. The varying capacitance is read in through the analog pins and converted to a color value from 0-255.

Materials and parts

A table with estimated costs of your materials and parts and links to the source material at an online store such as sparkfun.com, adafruit.com, digikey.com, etc.

Schematic Diagram

Design Process

While looking for various materials during brainstroming phase that we could use for touch-based switches our top choices were:

Conductive Pencilts (Draw circuits and use touch as input)
Wooden joystick or joystick made using paper towels and aluminium foil
Aluminium foil balls used as an input.
Low tech number pad to add rgb values for different colors as input.

Reasons for choosing Cans over other materials:

Common Household Item: Coke cans are widely available in households, making them a convenient and accessible material for a quick and simple project.
Easy to Connect: They can be easily connected using the alligator clips.
Recyclable and Sustainable: Repurposing a common item like a Coke can for a new purpose adds an eco-friendly element to the project, promoting resourcefulness and reducing waste.
Visual Appeal: The recognizable branding on Coke cans can add a visually interesting and engaging element to the project.
Innovative and Intuitive: Coke cans were something new when we came across the idea of using them and it was very intuitive for first time users.

Prototyping Phase

During prototype we designed a visual of how the circuit will be connected to blink the LEDs and showed the working of the project roughly.

As we proceed towards the implementation we also decided to make this project a little more fun by adding copper plate and aluminium foil wrapped with paper towels. This is used as a roller to control the resistance in the circuit so that the brightness of LEDs is maintained by this element. Sounds complex but it was something out-of-the-box to think about for us. So in simple words, the r, g, and b are used to turn on the respective color. The paper towel roll slider on the side is used to adjust the value of the color and then the white can is used to save the color on the tri-color LED.

Challenges

Getting Various metals to read consistent values.
Introduced a copper plate to keep a common ground.
Getting the aluminium foil and paper towel capacitor to read values.
Set up the slider just like the other “capacitors”.
Used the copper plate to keep common ground.
Getting everything into the box.
Coding it in a way where the adjustment stayed on the tri-color LED.
Getting the LEDs to adjust across the whole range of 255-0.

Future work ideas

Add a screen to display the color code
Add a way to adjust brightness without having to go through each color
Create a better variable input to make adjustments easier

Thoughts on the project

Overall, we thought the project was a great way for us to think outside of the box. We hadn’t ever thought about using cans as input. This introduced us to capacitive touch as well, which is in many devices we use today. It also forced us to find not only digital inputs, but also analog inputs. The creativity we were able to express by creating the capacitor out of a paper towel roll, aluminum foil, and paper is something that we really enjoyed. We also learned about prototyping. In the beginning we had to come up with 20-30 ideas about possible directions that we could go. This forced us to think in new design spaces rather than the first thing that came to mind. This also showed up in our design process. We eventually settled on what we thought we might want to do, but this evolved as we found what was possible. We had prototyped with the paper towel roll capacitor but couldn’t find the right configuration to make it useful. Finally, we found the right combination of connection to the Arduino and use of copper plate to get it to work the way we wanted. This prototyping showed us what wouldn’t work and made us think in new ways.