Unlocking a keepsake box with Duemilanov and RFID

A few years ago, Mike Buss wanted to make something special for his girlfriend’s birthday. After experimenting with an Arduino board, he decided to design a high-tech keepsake box that can be easily locked or unlocked with an RFID card.

Aside from an Atmel-powered Arduino Duemilanove (ATmega168 MCU), key project components include a Parallax RFID reader (serial), micro server, piezo electric speaker, Pololu pushbutton power switch LV, illuminated pushbutton, triple output LED RGB, metal eye hook, small copper rod and a 9V battery.

“I had read about the Reverse Geocache Puzzle by Mikal Hart and thought the idea was brilliant. I wanted to do something similar, but with a twist,” Buss explained in recent blog post.

“My girlfriend had mentioned wanting a place to keep small mementos, so I thought a personalized keepsake box would be perfect. The box is fairly simple: the outside consists of a button and an LED. The button turns the box on and the LED indicates whether it’s locked.”

So, how does it work? Well, when the box is closed, a small metal eye hook is fed through a hole in the rim of the box. To lock the box, the servo pushes the rod through the eye.

“I wanted the battery to last as long as possible, so the Arduino is only powered when it needs to be. When the user presses the button, the Pololu switch triggers power to the Arduino, which then listens for RFID tags,” Buss continued.

“When a valid tag is found, the Arduino plays a little tune and turns the servo to unlock the box. If the box doesn’t scan any tags after a certain amount of time, the box shuts off. The Pololu switch works extremely well, [as] the box has been working for 4 years with the same 9V battery.”

Interested in learning more? You can check out Arduino’s official blog write up here and Mike’s detailed project page here.

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