and more bulky than we would have liked, but my primary
concern was making sure the system would function as
designed, and I'd just brace for any negative comments (of
which there were very few). I spent hours on the phone
with the DEFCON organizers discussing battery chemistry
and the pros and cons of each battery type. They chose to
move forward with three AAA batteries, which would
provide 4.5V at 1,250 mAh that I could bring down to a 3V
system voltage with a low-cost linear regulator. But, when I
started to look around to purchase 25,500 surface-mount
AAA battery holders, there was not enough stock worldwide and the manufacturer's leadtime was past the date of
DEFCON, which killed this approach on the spot.
We settled on using the CR123A, which I now know is
a better, simpler solution. The battery has built-in PTC
(Positive Temperature Coefficient) protection to limit current
flow in a short circuit or battery failure condition, and doesn't require any external voltage regulation circuitry in order
to be used in our system (thanks to the stiff voltage output
the battery has until it's close to end-of-life). The above
current measurements show that with a single 3V CR123A
rated at 1,400 mAh, the badge can last for hundreds of
hours of normal use, satisfying our requirement that the
badge remains operational for the length of DEFCON.
what pushes me to try PCB design and layout techniques
that I wouldn't normally consider in order to meet their
proposal. There were a number of major elements to the
badge's circuit board design: the physical board outline's
subtle curves; the complicated text cut-outs for the
conference attendee type; masking certain areas of soldermask to bring out graphics on the copper layer; and parts
placement, such as the arc of LEDs along the bottom edge
and locating the IR transmitter in the ninja's left eye. I made
a conscious decision to leave all parts designators off of
the badge. This lends itself to a much cleaner look at the
expense of easy parts identification. The assembly
drawings were available to people curious about hacking or
modifying the badge to make their job easier.
I had added in a few surprise graphical elements, such
as a two-dimensional Data Matrix barcode
( http://en.wikipedia.org/wiki/Datamatrix) and a secret
message used for the Mystery Challenge — a popular
hardware hacking/puzzle contest at DEFCON.
Until Next Year ...
Creating the badge electronics was only one part of the
battle, as aesthetics of the badge was also a fundamental
design goal. Each year when the folks at DEFCON say "Let's
try to make a badge that looks like this," they're saying it
purely from an artistic point of view. They're not concerned
with any electrical characteristics, manufacturing methods,
or PCB related limitations or constraints. That naivety is
All told, the DEFCON 16 badge project took about
220 hours, including the firefighting of supply chain and
manufacturing problems after development was completed.
The majority of engineering was done on nights and
weekends, much to the chagrin of my very pregnant wife,
Keely, as I was then spending my days as a co-host of
Prototype This ( www.discovery.com/prototypethis).
Thankfully, most of my time was spent doing what I love to
do — engineering.
We've already started to think about designs and
features for the DEFCON 17 badge and have had a lot of
great input from attendees and badge hacking contest
participants. Next year's design will be
even simpler and more accessible to
electronics hobbyists and beginner
hardware hackers, but will also contain
some "so new it doesn't even exist yet"
technology to impress even the most
hardened gadget geek. Even though I'll
be keeping the lessons of previous
years' badges in the back of my mind,
I can all but guarantee there will be
unexpected problems this time
around. Who ever said engineering
Complete source code,
schematics, audio, video, and other
documentation for the DEFCON 16
badge is available at
3 Amp Adjustable
www.dimensionengineering.com Switching Regulator
Dimension Engineering, 899 Moe Drive #21, Akron OH 44310, (330) 634-1430
Due to space limitations, the article
presented here is a condensed version of
the original. To read the complete article,
go to www.nutsvolts.com.