LED wristbands are now a common feature of large arena concerts and events, with a variety of capabilities and technical implementations. In the video after the break, Wall Street Journal does a fascinating deep dive into these wearable light shows.
The three main control technologies are IR light, RF radios, and Bluetooth. The IR-controlled ones are the simplest, and we’ve covered a teardown, a reverse engineering effort and reflash of the Pixmob IR armbands.
Finally, we get a good behind-the-scenes look at how they are controlled. Using pan-tilt IR emitters mounted on lighting towers, the operators can sweep across the audience controlling color and light levels or activating pre-programmed sequences.
RF armbands have the simplest control setup, only requiring a single portable transmitter connected to a computer running the control software. It does however require some pre-planning for more complex light displays, to ensure each section of the audience is individually addressable.
The most advanced and expensive versions are handheld light sticks controlled via Bluetooth from an app on the users smartphone, and are popular at K-Pop concerts. Each device is linked to the users seat number, making them individually addressable and allowing the lighting operators to produce complex patterns, and even text, in the crowd.
While each of these devices is simple and underwhelming on its own, tens of thousands working together produce impressive effects and probably hide some hard-earned engineering experience.
More fallout for SpaceX this week after their Starship launch attempt, but of the legal kind rather than concrete and rebar. A handful of environmental groups filed the suit, alleging that the launch generated “intense heat, noise, and light that adversely affects surrounding habitat areas and communities, which included designated critical habitat for federally protected species as well as National Wildlife Refuge and State Park lands,” in addition to “scatter[ing] debris and ash over a large area.”
Specifics of this energetic launch aside, we always wondered about the choice of Boca Chica for a launch facility. Yes, it has all the obvious advantages, like a large body of water directly to the east and being at a relatively low latitude. But the whole area is a wildlife sanctuary, and from what we understand there are still people living pretty close to the launch facility. Then again, you could pretty much say the same thing about the Cape Canaveral and Cape Kennedy complex, which probably couldn’t be built today. Amazing how a Space Race will grease the wheels of progress.
There’s something magical about a laser light show. Watching that intense beam of light flit back and forth to make shapes and patterns, some of them even animated, is pretty neat. It leaves those of us with a technical bent wondering just exactly how the beam is manipulated that fast.
Wonder no more as [Zenodilodon], a working concert laser tech with a deep junk bin, dives into the innards of closed-loop galvanometers, which lie at the heart of laser light shows. Galvos are closely related to moving-coil analog meters, which use the magnetic field of a coil to deflect a needle against spring force to measure current. Laser galvos, on the other hand, are optimized to move a lightweight mirror back and forth, by tiny amounts but very rapidly, to achieve the deflection needed to trace out shapes.
As [Zeno] explains in his teardown of some galvos that have seen better days, this means using a very low-mass permanent magnet armature surrounded by coils. The armature is connected to the mirror on one end, and a sensor on the other to provide positional feedback. We found this part fascinating; it hadn’t occurred to us that laser galvos would benefit from closed-loop control. And the fact that a tiny wiggling vane can modulate light from an IR LED enough to generate a control signal is pretty cool too.
The video below may be a bit long, but it’s an interesting glimpse into the day-to-day life of a lighting tech. It puts a little perspective on some of the laser projection projects we’ve seen, like this giant Asteroids game.
A few summers of my misspent youth found me working at an outdoor concert venue on the local crew. The local crew helps the show’s technicians — don’t call them roadies; they hate that — put up the show. You unpack the trucks, put up the lights, fly the sound system, help run the show, and put it all back in the trucks at the end. It was grueling work, but a lot of fun, and I got to meet people with names like “Mister Dog Vomit.”
One of the things I most remember about the load-in process was running the snakes. The snakes are fat bundles of cables, one for audio and one for lighting, that run from the stage to the consoles out in the house. The bigger the snakes, the bigger the show. It always impressed me that the audio snake, something like 50 yards long, was able to carry all those low-level signals without picking up interference from the AC thrumming through the lighting snake running right alongside it, while my stereo at home would pick up hum from the three-foot long RCA cable between the turntable and the preamp.
I asked one of the audio techs about that during one show, and he held up the end of the snake where all the cables break out into separate connectors. The chunky silver plugs clinked together as he gave his two-word answer before going back to patching in the console: “Balanced audio.”
Musical Tesla coils are nothing new around here, but we have yet to see someone allow the general public to play music on their coils. That’s what makes this event unique – anyone is encouraged to submit their to the Tesla Orchestra team, which will then be played back via a live video stream next month. Their web site offers up all of the technical details as well as the file format requirements for submitting music for the event, so get started on your entry today!
If a passive approach is more your style, stick around for a quick video demonstrating their coils’ abilities. Sure it’s Lady Gaga, but we won’t tell anyone you watched it. Plus, it’s totally legit when the song is being played using 20,000 volts.
[jay] reminded us of this old video of solenoids banging rhythms on furniture and household objects. There’s no schematic, but in the video it looks like an Arduino drives a bunch of solenoids through relays. The PC interface is run on Pure Data, an open source programming environment for audio, video, and graphic processing. Thanks [Jay].