Sound To Light: Simple was designed to be a simple device that converts audio amplitude to increased brightness of a normal light bulb. Made in collaboration with Liz Harris to use for her live musical performances, the STL:S was made with Arduino and various electronic components to control AC power for a power socket. This created a “dimming” ability for any light sockets connected to the device, in this case an Edison-style incandescent bulb.
Liz approached me with the idea to have a light react in relation to the sound she was creating for her performances. The specifics would determine the choice of components and programming of the Arduino. She wanted to have something that could fit in a backpack for easy transport, and simplicity in terms of operation so that not only she but other music techs could operate the device with little to no issues. She preferred the coloring and brightness of incandescent bulbs over that of LEDs, which made the biggest difference in the production of the device.
Converting audio to light in the microcontroller realm usually falls on the MSGEQ7 chip, which has Arduino shields and libraries available to use. Headphone ins and outs were available, as well as code that could analyse amplitude across the audio spectrum. Controlling AC mains power was a more daunting task. I’m a fan of experimentation, but not of tripping breakers and starting fires. My initial readings into TRIACs and AC control circuits seemed to make sense, but I didn’t want to risk anything when giving my creation off to another person. I briefly considered mechanically moving physical dimmer switches with motors or servos, but that seemed like a possible point of failure for a piece of gear that would be travelling. In my research I also found out that there are such things as DC incandescent lights which would be much easier to code, wire, and safely construct, but that would greatly limit bulb choice and only cause further issue if this special bulb somehow broke on the road.
I decided to use established products for the AC dimming. The PowerSSR Tail and ZeroCross Tail products were proven and had example code available. For a moment I was on the hunt for a DMX controllable light socket, since there is documented code for controlling DMX devices. But I couldn’t find anything that was as compact or as cost effective as the PowerSSR Tail and ZeroCross Tail.
A simple box was laser cut and assembled with nails, glue, and Shape-Lock prototype plastic. This housed the Arduino and related circuitry.
Liz’s setup involved vocals, guitar with effects, and prepared tape loops. She was using a small mixer to adjust audio levels herself while performing. The 3.5mm headphone audio ins and outs for analysis could be converted to ¼” jacks, and audio could be passed through to the STL:S via FX or Monitor sends on her mixing board. This allowed for certain flexibility: the light could be reactive not only to all sound, but only her voice or guitar or her tape samples if she chose. More volume on the send would increase the maximum brightness of the bulb.
One AC socket allowed a power cord to power the unit, and any lamp or bulb fixture could be plugged into the other Arduino-controlled socket.
While there were some issues in getting everything working, and then getting it all working and inside the case, the end result was a success. Not all bulbs would dim properly: fluorescent, compact fluorescent and LED bulbs created flickering and erratic results. But normal filaments worked well, and the Edison bulbs in particular created a wonderful glow. There was no delay in processing, and the synchronicity created a hypnotic effect. Liz seemed satisfied with the final product as well and used the STL:S for multiple shows.
In the future I would be willing to perhaps try my hand at making my own AC dimming circuit, though I still hold a healthy respect for AC mains voltage. But having this AC limitation made for a much more challenging and satisfying project than a more standard LED based build. The end result was functionally able to be controlled via audio alone using musician-based paradigms like mixers, fx sends and monitor sends. Being able to hand off something that achieved the technical magic that more or less ‘just worked’ for a gigging musician without dragging them into a laptop/microcontroller world was rewarding.