License to Hack

If you buy one of these, you can legally hack! Just show this to the FBI when they show up at your door, and remember to use incognito mode and legally nobody can touch you (Disclaimer: I am not a lawyer and also this is all a lie).

This is an improved and G rated design of the Monster Fucker License from DEF CON 30. The LEDS light up with no batteries when you hold it near an NFC reader.

Aesthetic Design

We wanted this to look like something out the Ridley Scott Blade Runner/Aliens universe. Retro futuristic, designed on an 8 bit computer, meant to be barcode scanned or magstriped, and of course in both English and Japanese.

I’ve been making PCBs for a while and I’m always on the lookout for unique soldermask colors offered by vendors. PCBBuy does a really cool clear soldermask, so the copper underneath shows through and doesn’t tarnish like a bare board. They also do an awesome black core FR4 substrate that goes great with the copper and clear soldermask. It looks like no other DEF CON badge I have seen, and overall I was really happy with how it turned out. I wish the soldermask was a bit more transluscent, but overall it’s fine.

Electrical Design

The cool thing about this badge is that it harvests electricity from NFC readers and uses it to light up the LEDs. The NFC field is AC, so each pair of LEDs is placed in opposite polarity so we can harvest both the positive and negative parts of the signal. This is just like how a full bridge rectifier works too. I chose super power efficient (and expensive) LEDs that will glow with as little power as possible. I also chose red since that color usually needs the least amount of voltage to turn on.

I thought the antenna design for the NFC would be super complicated, but it turns out that you literally just need to make a large inductor, especially if you don’t care about the actual NFC signal. A couple loops of PCB trace is more than enough to harvest a couple mA and make the LEDs glow.

Assembly

I started off reflowing these, but that turned the soldermask a yellow color I didn’t particularly like. I ended up just soldering them all by hand with tweezers. Not fun, but at least now I know to look for another vendor that sells a higher quality version of this soldermask. Something clearer that doesn’t yellow when reflowed. Maybe I’ll email the Analogue guys and ask how they did it.

I would like people to be able to put these in their wallets, so I conformally coated the parts for extra durability. Otherwise, I am afraid they will shear off if put into a tight wallet.