Enormous sound responsive LED wall made of an array of intelligent autonomous modules!
This kickstarter project is intended to let us build a sound responsive wall for Burning Man 2012, a 10x10 module monster which will have over 25,000 lumens of light output. This is going to be an art project at Camp KAOS in the Boston Hive, so we want to make sure we really step up to the plate and bring some awesome interactive art!
Any donations we receive past what we need to make 100 lights will go towards making more lights to expand our own array, do installations, and (of course) to provide you awesome people with lights to make your own arrays, so please don't hesitate to donate beyond the target goal! We want to see these everywhere!
I've loved sound responsive light shows since I was a freshman at MIT, living in a room where an elaborate software program running on a computer would analyze music in order to turn on and off circuits in the room. Light shows are really fun, and add a lot to a music performance. However, they are usually very complicated and hard to set up.
To make this easier, instead of using a computer to analyze music, we put all of the music analysis functionality in hardware on our lights. Instead of having a complex communications system with wires running everywhere, we made it so that each light has its own microphone.
The result is a simple, modular, autonomous system based on the color organs of the past except using digital electronics and ultra bright LEDs, easily expandable into arrays of arbitrary size and shape. With an array like this, you could visualize sound moving across the wall, or in a music venue it could be a visualizer that would respond to a band or DJ completely automatically!
How does it work?
Even kids love it :-D
The design is essentially completed, and I have quotes in hand for manufacturing. My expectation is that this will result in a delivery date near the end of 2012, obviously with the first batch done in time for the display at Burning Man 2012 in September. However, my goal is to finish this process sooner if possible, and I more commonly finish projects ahead of schedule than behind.
We will either send you a light used on the playa, or send you a new one depending on how many we are able to end up making.
We've built a prototype that worked extremely well in our test installation, and are confident that the next version will work even better. And to make that happen, we need your help! Without your support, we simply can't make this project happen!
Thank you for your support!
Note: If you are not in the US, please add $10 to your donation to account for shipping. Thanks!
How hackable will the finished products be? Will an experienced electronics tinkerer be able to easily modify them? Will you provide schematics?
An experienced tinkerer will be able to modify the behavior of the audio analysis chip between the two default modes through the use of a 0 ohm SMT resistor jumper that connects the mode pin to either GND or V+. The audio analysis chip is the LP3950 from TI/National, and from their datasheet (page 20):
"Audio Synchronization has two modes. Amplitude mode synchronizes LEDs based on the peak amplitude of the input signal. In the amplitude mode the user can select one of three amplitude mapping options. The frequency mode synchronizes the LEDs based on bass, middle and treble amplitudes (= low pass, band pass and high pass filters). The user can select between two different responses of frequency for best audio-visual user experience."
In our experience with the chip, the frequency mode makes more sense visually, since it naturally makes low frequencies red, mid frequencies green, and high frequencies blue. Amplitude mode, instead, adds more colors as the amplitude goes up, low volumes are red, mid volumes add green, and high volumes add blue. We don't feel this makes much sense in this context.
We are also going to add a way to bypass the microphone and amplifier and instead provide a line level source signal to the audio analysis chip, so that if you have a higher quality microphone or audio input that you prefer to use you can do that.
Schematics will be provided.
Each light has a surface mount electrolet microphone that goes through an amplifier for some preamplification, and then through a capacitor into the mono input of a LP3950. The capacitor acts as a high pass filter so that only sounds above 25-30Hz are seen, and also allows the LP3950 to re-reference the sound signal to be centered around the circuitry inside.
Internally, the LP3950 uses a variable gain amplifier with the gain set by the peak amplitude seen recently so that the light is more responsive in quiet environments than loud ones, followed by digitization of the signal. The signal is then split into high, medium, and low frequencies, and the LP3950 outputs PWM signals (inverted, they are open drain) intended to drive low power LEDs with a few tens of milliamps. In our system, we are driving higher power LEDs than that (700mA), so instead we use an inverter to get a positive active version of the PWM signal, and then use that to control a transistor system that activates each LED.
A schematic of the prototype shown in the video is available here:
There were some minor issues in that version, namely that every time the LEDs turned on the noise from the high current switching would appear on the reference voltage to the initial input opamp between the microphone and the LP3950. Amusingly, this would cause the LP3950 to enter a feedback loop where the PWM signal would appear to be an audio signal which would then cause more PWM signal. In the prototype we fixed this by adding a feedback capacitor to filter out high frequency noise on the audio input as well as increasing the overall gain -- this has the effect unfortunately of reducing the sensitivity to high frequency actual signals.
In the final version, we are addressing this by putting in a high CMRR regulator to provide a stable reference voltage for the preamp. We felt a little silly for not realizing this would be a problem sooner, but the next version should perform substantially better because of this.
Additionally, the newer iteration will use an actual current source for each LED set to 700mA instead of the simplistic transistor and resistor current limiting setup shown in this schematic. The transistor and resistor work fine, but mean that each LED is actually seeing something between 500mA and 900mA due to variations in forward voltage. To do this, we will be using a pretty cool chip, the STCS1. It's still a linear regulator because switchers are just too difficult to fit into the small footprint, and are a bit too expensive to add, but it should be a significant (although mostly not noticeable) improvement to the high power LED subsystem of the design.
The last thing we are adding is a line in with a jumper that allows you to reconfigure the moonlight to accept audio signals from a higher quality single microphone source at line levels and send them directly into the LP3950. This will be done with a header on the back of the board accessible behind the case.
Power wires plug into the board from a header on the back of the board that similarly sticks through the case.
Cases will most likely be pretty similar to what is seen in the videos. If the quantities get high enough it might make sense to use an extruded aluminum case, but my guess is that we will continue using bent sheet metal parts due to the small quantities. Each case has mounting holes on the side for angle mounting as well as in the back for directly placing onto a wall or scaffold. In the case of a scaffold, the combination of mounting holes and power plugs on the back mean that it can be entirely assembled into an array with no visible wires (wire runs inside of the scaffolding).
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