ARDUINO CONTROLLED LED PLAY TABLE PROJECT

Overview

CONTEXT

Over the fall 2019 semester, I took the class INFO 4320: Introduction to Rapid Prototyping. The class provides hardware and software design thinking skills and an introduction to modern rapid prototyping techniques such as laser cutting, 3D printing and microcontroller programming (such as the Arduino system). This was a semester long project that I and three other students worked on.

SUMMARY

The Play Table aims to provide entertainment and functionality to the user. The goal of this project is to apply the concepts and principles learned in INFO4320 to build an interactive and immersive environment facilitated through the Play Table. The hope was to create not just a piece of furniture, but an entertaining environment for our prospective users.

SOLUTION

This Play Table can be used alone with its Demo Mode functionality. It can also be used in a group setting with immersive LED lights shows for parties and an interactive Tic-Tac-Toe game. We hope the created environment will encourage socialization and provide an outlet for stress.

Research

To the best of our knowledge, various portions of this project had been done before. There are already interactive tables and hardware that exist for building such projects. The main aim of this phase of the project was therefore to do an in-depth analysis of existing projects to provide us with a basis of usable software and functions to be used as building blocks for the implementation of the Play Table.

The main components of our research were:

• Light displays - history of light as a spectacle and similar LED displays

• Techniques used to build key components - hardware and software

• Interactivity - exploration of various forms of interactivity

The research provided us with a roadmap of best practices and materials to use in terms of hardware and software, that will aided the implementation of the Play Table.

Design

LED Panels

The LED Panels were first implemented in the demo version of our prototype through a 2 x 2 table that spanned 3 LEDS for each panel. The panels were suited with conductive glass for touch functionality and wooden borders. As the design process moved forward, we pivoted to panels that spanned 2 LEDS and responded to conductive plastic instead of conductive glass due to budgeting restrictions. The LED Panels were constructed using a ⅛’ inch thick clear acrylic sheet over 7 strips of led lights that spanned the length of 14 LED pixels. The panels were frosted with frosted spray paint to diffuse the lights. Dividers were set in place to create a pixelation effect. 

The main challenge of the LED lights was soldering. A loose connection to either 5V, Ground, or the Digital Input pins would not allow the LED strip to function in anyway. It was also nearly impossible to test which pin was not soldered onto the strip correctly, if it was faulty, the whole strip would be rendered defective or had to be unsoldered. This was an incredibly time consuming and lengthy process. The final performance of the LED panels was surprisingly polished. The LED lights were able to produce a beautiful light show through the acrylic and dozens of patterns were able to be constructed and compiled. The LED lights give off amore visualizing appeal in a dark

Touch Functionality

In our first implementation we used four pieces of 10 cm x 10 cm ITO coated glass connected to one MPR121 sensor. ITO glass is a clear glass that has one of its sides coated with ITO, which makes glass conductive while the other side is completely insulated.  For the touch functionality, we used a MPR121 12 Key capacitive touch sensor. The sensor has 12 individual pins, and we connected 4 sensor pins to the conducive side of four pieces of ITO glass using hot glue. We connected this sensor to an Arduino microcontroller. This sensor uses the I2C to communicate and it requires at least two pins in order to interface. The IRQ channel in the sensor was very useful for debugging as it lights up an LED every time touch is detected.

Moving forward, we evaluated the performance of our first prototype with a couple of metrics. We evaluated cost, touch responsiveness/sensitivity, feasibility of scale, and consistency. For the final touch screen surface, we used forty eight pieces of 6.6 cm x 6.6 cm  ITO (Indium Tin Oxide) coated plastic adhered to a 24’’x24’’ acrylic sheet and connected to a four MPR121 capacitive touch sensors.

We faced a couple of integration problems mostly related to scaling up. Integration process involved three main steps:

1. Placing all copper, ITO and wire combination on the glass

2. Placing them all in the container

3. Attaching all squares to pins in the capacitive touch sensors

The touch functionality worked as we expected with the sensors responding to touch and LEDs performing specific actions. Some of the squares were very finicky due to the unstable nature of the wires.

Container and Table

The container component is a shallow box that holds the LED component, hardware, wiring and touch component. The container for the first prototype was made out of chipboard. The first prototype was designed to hold 4 touch tiles in a 2 by 2 pattern. Because of this the prototype was created to be 20cm by 20cm in order to allow for the 10 cm touch tiles to be placed on top. The prototype was made to be 5cm in height allowing it to be shallow. Holes were made in the back side of the prototype to allow for wiring to enter the box. Dividing walls were created so that 4 separate boxes could be made out of the larger box. The dividing walls were also made out of chipboard and laser cut. The insides of the box and both sides of the dividing walls were painted black. This was done to allow the LED lights to appear brighter.

To reach our performance goal for the final prototype instead of painting the inside of the container black we painted it white. Through research and suggestions we discovered that white paint would allow the light inside the container to appear brighter. We also decided to create extra room on the sides of the container to allow all of the hardware to be placed inside of the container unlike in the first prototype where our breadboard was outside. Furthermore, we removed the gridding from the lid and instead just made a lid that secures the clear acrylic to the top of the container.

Overall, we were satisfied with the performance of the final container. It allowed our design to look polished and professional. Our final container was 24” by 24” by 4”. The section inside with the lights was about 18.3”. We extended half of the walls to be full length of the container and the other half to only to the length of where the lights were. This created the gap for hardware. There ended up being 16 walls, forming a 7 by 7 grid. We painted the container completely white to give it a uniform look.

FINAL DESIGN

Conclusion

KEY IMPROVEMENTS

Key improvements in our design would be using solid wire. This would create a more consistent connection between the ITO plastic and MPR121 sensor. Another improvement would be soldering the wires to the sensor for a more secure connection. In terms of the box and grid, we could create more space within the grid panels to thread the wires through. Giving them added space would allow for less cross sensing between the touch squares.  If we had more time, we would love to integrate different games such as snake, or tetris. We believe this would increase the interactivity of our table.

REFLECTION

I learned the value of prototyping early and often. We appreciate creating the first prototype and learned a lot about touch sensors and controlling LEDs. I learned a variety of different skills, from 3D modeling to Arduino hardware, that allowed us to fully implement an electronic interactive display. 

I also learned how important team morale and good team dynamics are in a group project. Because we communicated effectively together and divided up tasks based on strengths, we ultimately had a successful project. Overall, I learned about the value of prototyping, the technical skills, and the value of a good team.

At the end of the project, we got a chance to share our work in a project presentation event at the Science Center and had the privilege to share our work, illustrated in the poster below, with professors, students and other clients that were not part of our project.