Toys for DEFCON 20

Like most years, DEFCON is an exhausting event. A handful of denhac members spend months planning for various events and toys. Once again we helped build 303, denhac and Skytlaks badges. The write up on the badges can be found here.

dsockwell and eaxpirate put together a bad ass donation box for Mohawk-con. If you’re unfamiliar with it, Mohawk-con is an event at DEFCON to raise money for the EFF, and hackerspaces. Hackers get a very stylish, sexy haircut on the convention floor (I may be slightly biased) and hackerspaces compete for the donations with over-the-top donation boxes.

denhac donation box

Some info about the box from dsockwell:

This year, Denhac has again fielded a donation box for defcon. We reused the old hardware, but added an awesome laser-cut enclosure with blinking lights, and a bill validator to take your money.


The donation box passed through a number of phases – Communicating with the bill validator, programming an ALIX board to run the validator and printer, and cutting and assembling the case.


Communicating with the validator:

Using a handheld oscilloscope ( ) we were able to find out that the validator sends a series of pulses over one of its interface pins. When a bill is inserted, the device sends 1 50ms pulse per dollar value of the bill. For the donation box, wewired that signal to a GPIO port on the ALIX that was being wasted on a green LED. Who needs those??


Programming the ALIX

Over the course of about 6 hours, eaxpirate and I lashed together a horrifying maze of perl and python scripts to detect the falling edge of each pulse. The alix dumped totals and details from each receipt to a sqlite database, which we kept for our own purposes.


Assembling the enclosure

Ah, the fun part! A friend of the space offered to laser-cut whatever enclosure we designed, and another friend gave me an awesome idea to make it look good. We used clear acrylic, painted on one side with glossy black spraypaint. When the acrylic went to the cutter, we etched all of the lettering through the paint. Inside the case, we put
about 3 watts of RGB LEDs and a BlinkM MaxM to control them all. The result: Backlit letters on a shiny black panel. Very slick.

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