# I Cracked And Modded the DNC Bracelet
Matt Hodges
2024-08-28

**Heads up:** This post has some videos that contain flashing lights.

![](00-dnc-teardown.jpeg)

If you managed to get a seat on the final night of the 2024 Democratic
National Convention (I got there at 2:30 pm and still had to rely on
seat-saving friends!) you probably also found an LED bracelet wrapped
around your arm rest. I’m bad at remembering to take photos of things in
the moment, so here’s mine over my kitchen counter:

![A photo of my LED DNC bracelet that I took later](01-wristband.jpeg)

If you’ve been to a large concert in recent years, you may have seen
this before. It’s designed to give the audience an “immersive”
experience with the entertainment,[^1] usually by activating the lights
at key moments. At the 2024 DNC, that key moment of audience activation
was when Vice President Kamala Harris walked out to deliver her speech.
I didn’t take a photo of the crowd during that time, but everyone lit up
in twinkling red, white, and blue lights. It was fun.

I used to work on [immersive audience engagement
tech](https://lisnr.com/) (that has since pivoted to retail payment
tech), so I was curious how this worked. Luckily, I took the bracelet
home so I could find out!

The first thing that caught my eye was **PIXMOB** engraved onto the back
of the plastic case.

![PIXMOB engraved on the back of the DNC bracelet case](02-pixmob.jpeg)

I had never heard of PIXMOB, but their
[website](https://pixmob.com/products/led-wristbands) gives some
immediate answers. Apparently they offer three different wristband
products. All of them look identical so I wasn’t sure which one I had.
My first thought — as is often the case when I’m trying to learn
something election-related — was to dig through some FEC filings. I
spotted in the PIXMOB [Terms and
Conditions](https://pixmob.com/terms-and-conditions) that the company is
actually called **ESKI Inc.** I spent only a few minutes clicking
through the [Democratic National Convention Committee’s
expenditures](https://projects.propublica.org/itemizer/committee/C00827022/2024)
without finding any mention of PIXMOB or ESKI. I suspect that the
Convention Committee retained an events vendor that was a middleman to
this hardware.

So I grabbed my [Jimmy](https://www.adafruit.com/product/2414) and
cracked the thing open.

![Opened DNC bracelet](03-open.jpeg)

Like most consumer electronics, the thing is mostly battery! I actually
wasn’t expecting AAAs, but it’s helpful to know we’re working with 3
volts and I can easily swap some in if they die.

At this point, I also had the [PixMob Wikipedia page
open](https://en.wikipedia.org/wiki/PixMob) (is it PIXMOB or PixMob?).
It features [another cracked PixMob
wristband](https://en.wikipedia.org/wiki/PixMob#/media/File:PixMob_PCB_and_case,_used_in_Zurich_2024.jpg)
that was apparently used at Taylor Swift shows. That one also sported a
white PCB, but used button cell batteries.

Besides the batteries, I also noticed that the Taylor Swift wristband
listed a `Palm` (like palm tree) version number, while mine has a
`Diamond` (like shiny carbon) version number:

![Opened DNC bracelet showing the Diamond version](04-diamond.jpeg)

They both have a copyright on them, too, and at some point I want to ask
an IP attorney whether you can actually copyright a PCB or if you can
only copyright their [Gerber
files](https://en.wikipedia.org/wiki/Gerber_format). I would have
guessed the appropriate protection would be a patent. I also just
learned about the [Semiconductor Chip Protection Act of
1984](https://en.wikipedia.org/wiki/Semiconductor_Chip_Protection_Act_of_1984).
But that’s a topic for another time.

I tried searching [ESKI’s FCC filings](https://fccid.io/2ADS4) for some
more hints about the `Diamond` board, but didn’t find anything specific.
But I did find some [very interesting documents about an accompanying
infrared transmitter](https://fccid.io/2ADS4WASH). I bet those, or
something like those, were all over the the arena.

Moving on, the next thing I noticed about my wristband is that it has
four LEDs:

![Opened DNC bracelet showing four LEDs](05-four-LEDs.jpeg)

This means I probably have the [PixMob
X4](https://pixmob.com/products/led-wristbands/x4), dubbed “our
brightest wristband”.

Now that I knew what I was working with, I turned back to web search to
see what prior work has happened with cracking and modding these things.
Turns out, I’m not the first person to break one of these things open.
[There](https://www.youtube.com/watch?v=ziNF0seaw1k)
[are](https://www.youtube.com/watch?v=50LL-n7xZp8)
[so](https://www.youtube.com/watch?v=TuQImukbnRg)
[many](https://www.youtube.com/watch?v=TlK1jrO30PA) videos of people
getting these things to obey. And there are some [really cool GitHub
repos](https://github.com/danielweidman/pixmob-ir-reverse-engineering?tab=readme-ov-file)
demonstrating how to use [Arduinos](https://www.arduino.cc/) or [Flipper
Zeros](https://flipperzero.one/) to replay actual IR instructions to the
device.

At this point, I realized I wasn’t about to break any news with my
teardown. But I wasn’t doing this to break news. I was doing this to
break into the device. Also, I didn’t find anyone doing this with a
`Diamond` board device. I wasn’t invested enough to turn this into SBC
or microcontroller project. I just wanted to do a minimal mod. So I
pushed forward. And by that I mean I started poking around.

That small, bulbous, semiconductor in the middle of the board is the
Infrared Receiver. It can detect infrared signal, like those emitted
from TV remotes. The PixMob website says that this wristband is,
“infrared activated” so this seemed like a great entrypoint. I have no
idea what kind of IR receiver it is, so I looked up [the first one I
could find on Sparkfun](https://www.sparkfun.com/products/10266) and
consulted the
[datasheet](https://www.sparkfun.com/datasheets/Sensors/Infrared/tsop382.pdf).
I learned a couple things:

- the three pins are $V_{out}$, $GND$, and $V_{cc}$
- the $V_{out}$ pin is active low, which means its voltage drops when
  activated

There was no guarantee that my IR receiver also operated this way, but
spoiler alert: it did!

I grabbed a jumper cable and touched one end to the IR’s $GND$ pin and
ran the other side across one of the LED’s cathodes:

![](06-led-cathode.mp4)

Great. So the batteries still have some juice (a lot of posts suggested
this thing would be dead by the time I got it home) and I know the
polarity and pinouts of the LEDs. And all the LEDs are in series, so
that’s nice. I also learned that the LEDs are interrupted in their path
to ground, not their path to positive voltage, which is extra nice since
the IR $V_{out}$ is active low. That means I can create a voltage drop
from the LED’s anode to cathode by tying the cathode to $V_{out}$, so
when the IR receiver gets a signal and pulls $V_{out}$ low, the LED
should light up. And so I did! I grabbed the first remote I could find
in my living room, and pointed it at the receiver:

![](07-led-ir.mp4)

It blinks! You’ll notice that the LEDs aren’t as bright as when they had
a direct jump to ground. That’s because $V_{out}$ is still higher than
$GND$ so the voltage difference is a lot smaller. Which means the light
doesn’t get as bright.

That’s okay! This is a cheap crack and mod, so onward. After a bit more
poking on the board, I found a surface-mounted resistor in series with
the blue pinout from the LEDs. I soldered the IR signal jumper to that
resistor, because we’re Team Blue.

![My crude soldering from the IR signal pin to the blue LED
resistor](08-soldered.jpeg)

Not my best work. I’m better at through-hole soldering. But it works!

![](09-soldered-ir.mp4)

I closed the case back up, shut myself in a windowless bathroom, turned
off the lights,[^2] and clicked my remote:

![](10-dark-ir.mp4)

Now all I need to do is blast Beyoncé’s *“Freedom”* and I can relive the
2024 Democratic National Convention whenever I want.

I learned a lot!

[^1]: Neil Postman, I have forsaken thee.

[^2]: Said, “Bloody Mary” three times