We were invited to create a project using the Arduino 101 to be showcased at the Intel booth for Portland Mini Maker Faire. After an (understandable) obsession with the Netflix Series, Stranger Things, we decided to make a replica of the Alphabet Wall that the mother of a lost boy uses to communicate with her son who is lost in another dimension called "The Upside Down" (See Episode 3!).
Our design called for a 8'x8' wall that divides into two sections. Our project discipline, from the get-go, was to strive for functional accuracy as well as aesthetic accuracy. This meant replicating the worn-looking wainscoting, the dingy wall paper, real C9 bulbs; no detail was overlooked. So this 64 sq. ft, ugly wall had to carry live AC power, break in half, transport/setup/takedown easily, and stand up (and remain stood up) safely and reliably.
People can interact with the alphabet wall by writing a message or asking a question via a mobile app that uses BLE to communicate with the new Arduino 101 which powers the alphabet wall. People will then see their message in real time being spelled out with the lights. You can also select some prefabricated questions related to the show and the wall will respond with the lights. (See our Twitter feed of messages that were spelled out)
* Clarissa San Diego (Project Lead/Design/App Development/Fabrication Support)
* Micah Summers (Fabrication/Design/Electronics)
* Krunal Desai (Electronics/Software/Embedded Systems/Design)
* Dan Halpern (Software/Embedded Systems/BLE Integration)
* Katarina Wolcott (Electronics Support)
* Gabriel Bello-Diaz (Design/Fabrication Support)
HOW DOES IT WORK?
Software/Hardware: We capitalized on using the Bluetooth LE capability of the Intel powered Arduino 101 board since we knew the installation was going to be in an open area where WiFi would be unreliable. For the interface, we created a mobile app with a simple interface of an input field and several buttons that would run natively from an iPad using a Bluetooth connection.
Electrical: We use the MCP23017 I2C expander to provide the Arduino 101 with the additional I/O required to control 26 letters of the alphabet -- whose idea was it to have 26 letters! Each bulb is controlled by a 12V DPDT relay. When 12V is applied, the relays switch in AC Line and Neutral to the attached C9 bulb. To control the 12V application, we used low-side switching. Every relay has 12V applied to its coils, and then a wire is run to the drain terminal of a N-channel MOSFET. The source of the FET is tied to GND, so when gate voltage is applied, it acts as a switch to put the FET into saturation. When the Arduino commands the MCP23017 I/O expander to drive a high (logic level 3.3V), it enhances the MOSFET and as a result, current can flow from 12V through the coil of the relay, and back to GND, resulting in a specific bulb turning on.
This results in 26 individual return wires from the coils of each relay to a central board, where the MCP23017 triggers FETs to turn on, and "close the circuit" for each relay, resulting in a specific bulb turning on.
Are there versions before this that you learned from? We all had binge watched the Netflix Series in less than two days while the series was still new. Unfortunately, we couldn't find any other versions before this. But it was great to see other versions pop up after we made ours.
What should other makers know about this project before attempting it? We'd like to point out that there was definitely an easier and more scaled down version of doing this. Using a simple LED strip that is individually addressable will cut down production time immensely. We spent most of our hours making the C9 bulbs individually addressable since our goal was to replicate it as close as possible to the one in the show.
OMSI (Oregon Museum of Science and Industry) in Portland, OR
* September 10-11, 2016: Portland Mini Maker Faire
MOPOP in Seattle, WA
* September 17-18, 2016: Seattle Mini Maker Faire 2016
* October 8, 2016: Strangest Things Happy Hour Party
* November 9, 2016: Pop Culture Fest
* September 16-17, 2017: Seattle Mini Maker Faire 2017
* Arduino 101 (1)
* MCP23017 I2C expander (2)
* C9 bulb string (1 string with at least 26 bulbs because there are 26 letters in alphabet)
* KEMET 12V EC2-series relays (26)
* 1N4148 Diodes (26)
* IRLD120 Transistors (26)
* 100 ohm resistors (26)
* 10 kOhm resistors (26)
* 0.1 uF capacitors (4)
* 4' x 8' sheets of wood (2)
* Fabric (32 sq ft), acrylics paints, for wallpaper
Fun Fact We played 80s pop and synth music throughout the entire production of the project to get us in the zone.