Let’s be honest: most keychains are pretty useless. Yes, they are often witty, perhaps even somewhat fascinating, but ultimately they’re about as purposeful as bumper stickers on your car.
Don’t get me wrong, I have plenty of keychains myself, but if I had the option, I’d choose something that has real value if it’s going to be gracing my keyring and stabbing me in the leg while it’s in my pocket. Say hello to this PCB keychain that has the potential to become a basic ATmega328P dev board or a handy reminder of PCB design practices.
One side of the key ring has a routing design based on real components and schematics, while the other side has PCB design rules like “width vs current,” and “clearance vs voltage.” While it doesn’t come with a metal ring for attaching it to your keys, there’s a convenient hole in the corner for it to dangle from.
On the other side, you’ll find everything you need to solder components to the board to use it as a minimal ATmega328 development board. Soldering components like the LEDs, the ATmega328, LDO, and crystal are all fairly simple as well.
If you decide to go this route, use AVRStudio IDE to write and compile the code, along with a programmer like — you could use an Arduino, a µISP, an AVRDragon, etc. — to program the microcontroller with an ICSP header. At the very least, you’ll have a handy little keychain.
