Ask Hackaday: Did You Catch The Grammys?

Although award shows aren’t necessarily our thing, [T. D.] sent in something that piqued our interest. His friends recently got back from the Grammy awards where they witnessed thousands of LED bracelets blinking in time to a performance by Coldplay. A little bit of YouTubing pulled up this video that demonstrates the effect (because that video will probably be taken down shortly, just pick something from this link).

[T.D.]’s friends brought one of these bracelets back with them and like a good Hackaday reader, he cracked it open. This is the precious board pic that [T.D.] sent in. We’re pretty confident that the IC is an ATMega48PA, but beyond that we’re not quite sure how these bracelets can, “light up and flash at precisely the right time” as [T.D.] puts it.

From what we saw on the Grammy broadcast, it’s possible these bracelets merely flashed whenever the user clapped their hands. A circuit that simple doesn’t require a microcontroller, so we’re left wondering what the heck is going on here. If you’ve got an idea of how these choreographed light display bracelets work, drop a note in the comments.

EDIT: Commentors have pointed out these wristbands are called ‘Xylobands.’ There’s a great video of these wristbands in action at the 2011 X Factor finale.

82 thoughts on “Ask Hackaday: Did You Catch The Grammys?

    1. I don’t know but it seems to me this thing is meant to be synchronized to the song and it surely would be organizational pain following a schedule for a live show that exactly. Also you would have to synchronize the RTCs in factory and I guess that’s too complex. Just put in a microcontroller and flash it with a very simple algorithm, no need for calibration or anything besides flashing the MC which pretty sure is done automaticaly. It’s a one-night-use braclet don’t need to overengeer that…

  1. After a bit of googling, apparently they’re called “xylobands” and Coldplay have used them before. The inventors seem pretty protective of their intellectual property, but in an interview he did say,

    “Basically they’re an RF-driven wristband. They’ve got a receiver in them which receives data and that data tells them how to flash and when to flash, basically.”

    There’s probably a transmitter at the FOH.

  2. X2 is definitely a crystal, and there seems to be a lot of pogo-points for programming them (to a frequency?) So I’d guess it’s some kind of radio-link system between the bracelets and sound-to-light software running on a computer backstage

  3. i also believe its radio nadef but the comment above i beleive is wrong the “wire” or wires your seeing is most likely driving the leds on the bracelet . if you do look a little closer you can see the metal cross shaped section above the board has a thick trace going to it and on my phone i cant really see all that great but it doesnt seem to be tied or grounded on the other “top” side and thus i beleive thats the antenna .

  4. 2032 is a coin cell battery – the “2032+” is one side of it – I thing the metal structure is a spring that holds the battery

    on the LHS you see a bunch of inductors (L3 L5) – I think this is the RF matching for the antenna (one or both of the wires in the band)

    it’s receive only so probably no zigbee chip hiding there – might be just a single chip RF demod, or even a half dozen transistors hiding somewhere

  5. I also think C2, L3, L5 / C3, L4, L6 are impedance matching for the wires, both used as antenna and led supply. Wavelength at the given frequency of about 860Mhz as statet in the product-page returns in a wavelength of around 35cm. So the wires can easily form lambda/4 antennas, signal being decoded unter the epoxy blob and interpreted in the avr, then flashing the leds in the received pattern. The avr runs on its internal clock, the epoxy-RX-blob needs its own acurate X2 crystal. nice design, but not very cheap, considering the price of the avr.

  6. Why not just make it ultrasonic and pipe the “tone cue” into the PA? Seems simple enough. Nobody hears the tone being transmitted over the PA except the bracelets.

    Bada-bing-bada-bang… done. And worlds cheaper than RF, etc…

    In fact, I would be surprised if that isn’t exactly how they work. If not, I want royalties for the idea from the company when they slap their forehead and switch to that system. lol

    An interesting bonus is that anyone recording the audio from the show would likely also record the tones, which would help them identify bootlegged and unauthorized recordings.

    1. Difficult to say without knowing exactly what’s under the glop-top, but a microcontroller with integrated RF transceiver (e.g. Chipcon cc11 series) only commands a roughly 25% premium over the equivalent ATMega device.

      I guess that reliable ultrasonic detection would require at least a piezo element and some custom electronics as opposed to an all-in-one IC. Also, it would be expensive to make work if the PA is not capable of ultrasonic frequencies.

      1. Good point. I am assuming most speakers are capable of reproducing frequencies beyond the 20KHz, and this is typically true, but PA systems may filter that out. I would say that most people would not be able to distinguish a tone near the upper limit anyway. Especially if it were brief. I know my hearing doesn’t go that high (but I am 38) though I can still feel the pressure on my ears of tones I can’t distinguish.

    2. “I would be surprised if that isn’t exactly how they work. If not, I want royalties”

      maybe royalties is what keeps them from doing it that way!

      and I know you’re kidding.. but the idea of getting royalties for “ideas” is getting to be a big problem for our industry. You can’t ( or shouldn’t be able to ) patent “ideas”.

    1. Yeah. I read that after I made my post. I stand by the simplicity of my concept, however. Oh well…

      Seems to be more complicated than it needs to be since it is used to sync with audio anyway.

      1. And for general seating (like, a pit) where you wouldn’t know where people are seated (standing), have the client (wristband) perform different duties based on RSSI. It wouldn’t be perfect, but over a pit of a few thousand people, it’d probably average out to look okay. Also, without triangulation you could only do spherical shapes with your ‘pixels’. But its a start. Someone get on it!

  7. You can notice that different wrist bands are sometimes flashing differently than others. Pretty unique idea.

    I wonder if they gave different “sequenced” wrist bands out, or they can actually determine what other wrist bands are around them.

  8. It’s NOT clapping. I couldn’t get much from the videos. They focused on the bands and not the wrist bands. But I could see, they didn’t blink together, I mean, not ALL of them.

    Parts of it looked kinda random, parts were synchronized, but not ALL of them were.

    At first, I was thinking maybe sound, like the old color organs we used to see. But that didn’t sound or look right either. It looked some some beat to one sound, and some to another.

    So I’m better they simply send out a simple signal telling the (wrist) band to bear a certain color at a certain time, or blink a certain pattern, based on say a pre-programmed song.

    Thinking about how *I* would do it….

    I’d maybe have a couple types of wrist bands. Then send out a single code telling it when to blink. The wrist band, blinked a pattern 9or color) depending on the type. So at any one code, one band may blink the other may not. (or different colors blink).

    That way, you can get various visual effects across the room, but still only sending out one simple code at a time.

    Similar to…
    All blink
    only blue blink
    only red blink

    The device sending the code, would be more similar to the old color organs. (assuming they actually sang and played at the time, and didn’t use a tape or lip sync)

    1. Much better video of the wrist bands
      Looks like a preset set of blink patterns triggered by wireless.
      The different colors look good – very well distributed throughout the arena with none of the clustering you’d expect with pure random patterns..

  9. Thank you so much for rick-rolling me into watching five videos filled with some of the most annoying whiney out of tune rubbish (that I kept waiting for the song to start since it seemed to be a five minute long intro) this side of the tone deaf crack who… I’ll stop there since I ended up killing the audio before I shoved red hot pokers in both ears.

    … and STILL not seeing any “blinking in tune with the music” in any of them… though the cute blonde standing behind them doing a slow clap in sync with nothing was particularly amusing.

  10. The silicon holds and image from xylo’ software that handles RF based programming.. The straps are just LED strips..

    Too bad it didn’t get into the hands of ‘hackers’ or we’d see what the code on the silicon does..

  11. One thing that’s interesting is that the crystal is so far away from the micro. Maybe it’s a timing element for something else as well? the x2 above it makes me wonder if it has two differential outputs. Without seeing the other side of the board, it’s entirely conjecture. My guess is a simple one way RF transceiver. That way they can receive simple RF signals that say “Do routine A” when they play some part of a song, and then “Do routine B” when they get to the right moment. I bet it’s really simple like that.

  12. Hi,

    our glowband started to flash for a short period yesterday night.

    We don’t know how to activate the lights, but it seems as if an reverse engineering is possible by a simple method (that we try to find out).



  13. Realize this is kinda an old thread, but with Coldplay on their new tour there will be a lot more of these. From what I understand they are frequency synced, probably to a radio controller. I was thinking it might be sweet to figure out how to adjust it so that it blinks when I get a cell message. Would also need to do some adjustments so that it fits my wrist. If anyone goes to the concert. Go back to the gates after entering and ask for a few more. It worked at my show.

  14. I put a switch in mine so I can turn it on and off at will. They are indeed radio controlled and I believe each colour is a different frequency, so they can work separately. Having each one on a separate frequency so they chase around the stadium would be great, but likely that would be WAY too hard to make sure it works right as people tend to switch seats and move around and what not… I wish they came stock with a switch on the inside so you can actually use them after the show… would be great to put it on my leg when I am riding my bike at night BUT they use enough freaking solder that I didn’t have to use any extra.. just melted what they had and stuck the switch in! Which frequency they use, I am not sure yet… I might get to talk to it later (I wish I got 2 of them)!

  15. Have one sitting in front of me. Will attempt to dissect and take pictures. Doesn’t light up when you clap your hands. All I can say is this device made an already great act better. Now I must know how it works!

  16. Coldplay’s European tour has started today, so expect more hacking in the days to come!

    Some friends of mine got it working by just pressing hard the middle of the plastic case – that ruins the RF features though.

    Anybody has more information besides the following?


  17. I got mine yesterday. During the concert, some xylobands just light with RF order. Some also light pressing it. And some stay permanently blinking! :P
    I open it today. they have 2xCR3216 (6V) batterries and 1xCR3216 (3V). CR3216 look to be for RF functionality, and CR2032 for manual actuation?!?
    CR2032 has a little gap in the contacts. If I press it, the lights turn on. If I do it without the 2xCR2016, it dosnt turn on…
    Probably I will replace it with something costumized in order activate my xyloband (and the one’s from my friends) base in some easy RF signal. Of course I will replace my friends hardware too.

    Any suggestion about what hardware to use? Space is too limited for arduino mini… :S

    1. The problem with activating them is knowing what type of signal. As in, in the offical site they say they operate with a propriatary software wich sends __ RF signal. I’m thinking there’s more to that than just sending a simple signal in X frequency – more likely, a protocol.

      If we had access to that software and the antenna the reverse engineering process would be smooth

      1. Hi mregala! I did not intend to use the original hardware, nor to decode the proprietary protocol. That’s to much above my capabilities :P

        In my previous comment, you should read “2xCR2016 (6V) batterries and 1xCR2032 (3V)” instead of “2xCR3216 (6V) batterries and 1xCR3216 (3V)”…

        I just would like to consider a small microprocessor with RF interface. Easy to program (like Arduino), and capable to operate from low capacity batteries, like CR2016.
        Maybe some PIC (DIL8)?!? I have an EasyPIC5 development board stored from 5 years ago. Maybe it could be useful!?

  18. I went to Coldplay’s concert in London last night – absolutely brilliant!

    I’ve disassembled my wristband and can confirm the radio receiver is an Si4313 from Silicon Labs, data here:

    The CPU is an C8051F717, also from Silicon Labs. Data here: (click on “Product Matrix” tab and scroll down for the F717).

  19. more info ….

    Chip companies turn out smart components that go into all sorts of products, but every once in a while, a savvy customer comes up with a new application that embodies coolness.

    That’s why Austin’s Silicon Laboratories Inc. is smiling about its work with a small British company, RB Concepts Ltd., that invented flashing wristbands called Xylobands, which have been used extensively at recent concerts by the rock music group Coldplay.

    The plastic wristbands have flashing LED lights that are controlled by Silicon Labs’ low-power radio receiver and controller chips. And thousands of wristbands in an arena are controlled by a laptop computer linked to a Silicon Labs radio transmitter.

    The Xylobands are the patented creation of inventor Jason Regler, co-owner of RB Concepts, who just happens to be a Coldplay fan. Coldplay liked Regler’s invention and has used it to light up arenas and stadiums all over the world.

    Coldplay used an early version of the Xylobands at several events late in 2011. Then Regler’s company approached Silicon Labs early this year to help it come up with an improved version to comply with various international wireless standards for North America and Europe so the band could use them in this year’s world tour.

    It offered the chip company a 1 million unit product order. The Silicon Labs team also enabled new capabilities for the wristbands, so they could be synchronized with the band’s music. The Austin company had technical workers in the United Kingdom, Hungary and Austin working on designs for the radio transmitter and on internal software code.

    The band kicked off the North American leg of the tour April 17.

    “I have been in this business for 18 years, and this is the coolest project I have ever had to work on,” said Keith Odland, microcontroller marketing director for Silicon Labs. “I have never been this close to rock ‘n’ roll.”

    “Taking the LED wristband from concept to finished product required best-in-class embedded control and wireless technology,” Regler said. “Silicon Labs was the ideal choice for wireless technology, enabling us to achieve … certification and deliver more than 30,000 Xylobands just in time for a recent Coldplay concert.”

    Phil Harvey, Coldplay’s creative director, credited Regler’s company and Silicon Labs with excellent work in enabling the delivery of “hundreds of thousands of (wristbands) whenever and wherever we’ve needed them.”

    The wristbands, Harvey said, “have broken down the invisible wall between band and audience and put the audience right at the heart of the show. The mass feeling of joy and wonder when they all light up at the top of the show is hard to put into words.”

  20. I think what needs to happen now is some savvy ham radio dude / hacker needs to go and record the radio traffic at that frequency at the next concert and decode it. Once that happens, it becomes trival to figure out how the control signals are encoded and to duplicate that process!

  21. I’m an embedded engineer and I can shed some light into this regarding technical aspect of how it works because we’ve done this on 434mhz spectrum. There’s no need to hack the frequency. If you read the datasheets for the Si ISM transmitter/receiver and the fact they are using a widely available 8051 architecture processors (or any processor for that matter), you can easily write up some code and program the 8051 to do whatever you want with the LED strip. The RF part of the design is SoC (thanks to the silabs) and requires no programming, really, just mere register changes to setup the chips to communicate over a given RF spectrum. All the information is in the si4313 datasheet. Since there’s a modulator/demodulator on the tx/rx chips, you’ll get binary data on the SPI lines, which the processor (8051 in this case) reads and controls the LED strip (most likely thru a NPN or PNP) since the MCU pin can’t provide that much current. I you want to manually turn on the LEDs, you can do it in many ways. Cut the ground wire of the LED strip (black wire), solder it to a terminal on a switch (your own switch) and the second terminal of the switch should be soldered to the positive terminal of the battery. When your switch is in on (short) position, the LEDs will light up. A more clever way to do this, is give a 1.5v or so (must be above threshold voltage) to the base of the transistor (assuming it’s an NPN in the sot23 package on my board) and this will turn on the LEDs without any soldering.

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