Aurora Digitalis: Lights in the North

In the fall of 2011, our student group conceived, designed, and built a light show. Tens of thousands of lights decorated an outdoor plaza, all of them fully computerized and synchronized to music.

Not only was this a great organizational and technical challenge, it was a conceptually beautiful and engaging project. A light show is a wonderful synthesis of art and science. It displays the power of science and what people consider otherwise "drab" technical fields to evoke a sense of wonder, and allow a submersion of the senses as the lights and music build an exciting and communal atmosphere. By making the technical side more visible and accessible to the public, it encourages individuals to investigate and think of the applications of the sciences in new and creative ways.

The Vision

People are drawn to lights, as we are all visual creatures. Like moths to the flame, we wished to gather people from all over the university campus and from around the local area. As the project developed, it became clear we were laying the foundations for an event that could be more than a light show and a display of science. We realized this project had the power to inspire and engage the entire community.

We quickly joined forces with the university radio station, Radio K, and asked many other technical student organizations to bring their creative elements to the show. We brought in a stage for performing student groups, and even brought in local businesses that provided free food for the opening night. It was a night of lights, music, food, and community. The show consisted of the Trans-Siberian Orchestra's Wizards in winter, and Also sprach Zarathustra, best know for its use as the opening theme in the film 2001: A Space Odyssey.

The show didn't stop there. We continued the next night, and the next again, for weeks on end. With media attention from local news stations, newspapers, and the university, people from around the Twin Cities continued to flock to this community event. Hundreds attended the shows, and we plan for an even bigger and more engaging spectacle in years to come!

Quick Facts

We used 30 dimmer boxes, for a total of 480 controllable channels.
We used over 75,000 LEDs, yet they consumed less power than a hair drier.
We assembled the entire project, including the lights and circuit boards, in only nine days.
We collaborated with a total of five other student groups.
We used over 800 meters of rope light.

The Ornaments

A light show is useless without lights! In addition to wrapping trees and lamp posts, we created several types of lighted decorations and ornaments. We made stars, snowflakes, trees, and even a heart. It was slow starting, but once we came up with a solid design, the rest was easy. We learned many things while building the ornaments, among which is how versatile zip-ties can be.

Stars

We made seven stars, and hung them on a curved wall of the plaza. Each star was made out of five sticks of bamboo. A string of rope light was affixed around the perimeter with zip-ties. The stars were held in place with a combination of wooden stakes and twine.

Snowflakes

Keeping with our winter theme, we built some snowflakes. We started with a square of chicken wire mesh, and attached a single string of rope light bent in an artistic manner. This method allowed for some creativity. Since (almost) no two snowflakes are alike, our team members tried out their favourite design styles.

Trees

We made a set of twenty trees out of bamboo using a similar technique as the stars. Each tree was wrapped in a net light, and staked into the ground.

In addition to our bamboo and zip-tie trees, we also filled the branches of the plaza's real trees with lights. We also lined the flower beds and railings with rope lights.

The Electronics

Instead of buying expensive commercial DMX light dimmers, we decided to build our own. While it turned out to be much more difficult than we expected, we gained a valuable learning experience on designing and manufacturing electronics. You can download our schematics and PCB layout, and the source code for the microcontroller.

The requirements for each dimmer was simple: use a DMX signal to control sixteen strings of LEDs.

Power

Although a modern switched mode power supply is much more efficient, we decided to stick with a simple linear power supply. The power supply has three main sections: an isolated RS-485 receiver supply, a microcontroller supply, and the LED driver supply.

The DMX input of the circuit board uses a separate supply voltage to power an RS-485 receiver chip, and is fully isolated through an optocoupler. The microcontroller has its own 3.3 V supply, but shares a common negative with the LED drivers.

We say "negative" and not "ground" because the LED drivers are powered directly by the unisoltated, rectified 115 V mains. The negative rail has an 80 V potential with respect to earth ground. This is definitely not the best design, but it eliminates the need for a bulky and expensive isolation transformer capable of powering all the lights. A bleeder resistor connected across the main capacitor safely drains any residual charge.

Data

The RS-458 receiver chip converts the differential signal to UART, which is read by the microcontroller's serial port. We used a PIC18F24 to decode the DMX protocol. DMX is an industry standard protocol for controlling theatrical lights, making our circuit fully compatible with existing equipment. Five DIP switches allows us to select which of the 512 addresses in the DMX universe the lights will respond to.

From the microcontroller, two PCA9624 LED drivers are addressed over the I2C protocol. These drivers output a PWM signal for each of the 16 channels of lights. Each channel is amplified with a FET driver, and finally a large MOSFET. The resulting output can drive a string of LEDs, and is fully dimmable with eight bits of resolution.

To actually control our lights, we used a program called Q Light Controller, and a USB to DMX interface. Our lights were painstakingly sequenced to music, choreographing a visually stimulating show. This was one of the longest processes in the entire project, but in the end the show could be started with a single keystroke.

Downloads

pcb_schematic.pdf

dmx_source_code.zip

Manufacturing

After the design was complete, we had our circuit boards professionally fabricated. Once all the materials arrived, we began the long and arduous process of soldering.

We chose to use mainly surface mount components, since through-hole designs are nearly obsolete these days. Most of our team members had never touched a soldering iron before, so our project took on a teaching phase. Fortunately a couple members were seasoned experts, and under their guidance, everyone was soon soldering away.

We built everything ourselves, right down to the DMX cables. We used a spool of outdoor rated CAT5 cable, and carefully soldered the requisite 5-pin XLR connectors on each end. While the connectors were expensive, we decided it was worth being able to reuse our electronics with any standard DMX setup.

The Code

To actually run the show, we used a program called Q Light Controller. This allowed us to program all sorts of subroutines. The scripting language was XML based, making it portable and easy to edit. It uses an external USB -> DMX converter box to drive our custom circuit boards.

The program lacked some features we wanted, such as the ability to dynamically generate a light show from a song, so we have already begun developing our own program for next time.

The Proposal

We were especially honoured when a young man saw our show as the perfect opportunity to propose marriage to his soon to be fiancée! At his request, we quickly programmed an extra song for the show: The Black Keys' Everlasting Light. We also created a heart out of rope lights in a similar fashion to our snowflakes, and timed it to glow just as he got down on one knee to ask for her hand in marriage.

In case you're wondering, she said yes.

The Group

We are the Nikola Tesla Patent Producers, a group of science students and technology enthusiasts from the University of Minnesota. Our goal is to allow members to apply their skills to real scientific projects. In the short time we have been operating, we have grown from a handful of students tinkering on Friday nights, to a full-fledged student-led organization. Our projects have included a 10,000 volt Tesla coil, a near-space balloon launch and recovery, a rail gun, and many more.

By allowing individuals to propose their own projects and providing quality resources to make them successful, we encourage students to dream, design, organize and carry out every step in the process of discovery and invention. Because our members come from a broad range of technical backgrounds, each offers a unique contribution to the depth and quality of our projects.