Posted on Oct 23, 2011

Carto Re: Long Beach, CA

My friends at aphidoidea were contracted to build an interactive art installation for Long Beach City and designed an amazing store front sculpture. They asked if I could add some interaction and lighting effects to the 9 towers and after some brainstorming we came up with a simple solution that could easily scale. As you can see from the video above, I think it came out really well!

The first challenge was the store front interaction. We needed to detect three user states: 1. No users with a default light sequence 2. User standing in front with a high impact light sequence 3. User touching the glass with an intimate light sequence. After some research, the final solution was to use photocells that measures the amount of light. Using photocells would allow me to basically set ranges for each user state. Generally speaking, above 600 is default, between 600 and 400 is a shadow, and below 400 is touch. Ladyada’s post on photocells was an amazing resource.

The next challenge was lighting up the individual 30 ft towers. I knew I wanted to control each LED individually to achieve certain effects and with only a week build time, I had to find a prebuilt module so I could focus more on the code. At first I considered the BlinkM LED modules, but the I2C interface would prove to be difficult over the long distances. I decided to go with the ShiftBrite RGB LED modules since on the forums others had success with them and I liked their shift register behavior. I ordered all the 2ft six-conductor cables I could and began the build.

Putting it all together is always the most fun part for me. Using an arduino pro mini, I built a custom protoshield that would provide the necessary power and connections. The final design was simple, the photocell would be embedded in the glass then secretly run up to the ceiling and dropped to the tip of the tower. Inside would be the arduino connected to the 26ft chain of leds. After some iterations in code, I wrote the final version to calibrate itself when powered on since the street light was not very consistent. I’m skipping a lot of tweaking detail (as projects like this are always a learning process), but as you can see from the video it’s all worked out in the end!

One more thing…

The SMS interface! With some extensions in our timeline, I was able to work on a SMS interaction to allow users to SMS keywords directly to the sculpture. The keywords would then activate more light sequences from a separate light controller. Using Twilio is pretty straight forward and the challenge was getting it to control an arduino. If you are not familiar with Twilio, I highly recommended it for simple SMS and Voice interactions.

I wrote a simple web app on protodojo that would receive the calls from the Twilio api whenever someone texted the sculpture. This web app parses the text and then responds with a customized message before saving the text to a local txt file. Then onsite, we ran another application which polls the text file for the content on the text. If any keywords were found, it would send a value between 1-9 to active a special light sequence via a usb connection to the arduino. Since we only had access to a mifi for internet, polling was limited to every 5 seconds to minimize bandwidth.

More Info:
Carto Re Facebook


ShiftBrite RGB LED Module

6×1 F-F 24″ Cable for ShiftBrite

Ladyada Photocell Tutorial

Twilio SMS and Voice API

Orvac Electronics