Say Friend And Have This Box Open For You

The octagonal wooden box described in the project. On the left, outer surface of the box is shown, with "Say Friend And Come In" inscription, as well as a few draings (presumably from Lord of The Rings) and two metallic color stars that happen to serve as capacitative sensor electrodes. On the right, underside of the lid is shown, with all the electronics involved glued into CNC-machined channels.

Handcrafted gifts are special, and this one’s no exception. [pender] made a Tolkien-inspired box for his son and shared the details with us on Hackaday.io. This one-of-a-kind handcrafted box fulfills one role and does it perfectly – just like with the Doors of Durin, you have to say ‘friend’ in Elvish, and the box shall unlock for you.

This box, carefully engraved and with attention paid to its surface finish, stands on its own as a gift. However, with the voice recognition function, it’s a project complicated enough to cover quite a few fields at once – woodworking, electronics, and software. The electronics are laid out in CNC-machined channels, and LED strips illuminate the “Say Friend And Come In” inscriptions once the box is ready to listen. If you’re wondering how the unlocking process works, the video embedded below shows it all.

Two solenoids keep the lid locked, and in its center is a Pi Zero, the brains of the operation. With small batteries and a power-hungry board, power management is a bit intricate. Two capacitive sensors and a small power management device are always powered up. When both of the sensors are touched, a power switch module from Pololu wakes the Pi up. It, in turn, takes its sweet time, as fully-fledged Linux boards do, and lights up the LED strip once it’s listening.

[Pender] didn’t want to go for any cloud-based voice recognition service – such a gift requiring a pre-established WiFi connection would be no fun at all. Instead, he set up and used PocketSphinx for offline voice recognition. The box is a surprise for his son, thus, [pender] couldn’t quite ask for voice samples. Thankfully, PocketSphinx recognizes phrases without pre-training. There’s also a contingency mechanism – the electronics aren’t accessible until you open the box. The secret is to apply voltage to two pads, which will unlock the solenoids directly, just in case the battery dies or the Pi glitches out.

We don’t quite know what awaits when the box is opened, but we can only hope that the son’s name isn’t Balin. We thank [pender] for documenting the details, as a reminder that our hacker skills let us build unique and beautiful things for the people we value. Hacker-built gifts are great – we’ve seen guestbooks for weddings, couple’s proximity sensing LED badges, ESP32-based CTFs, and even meteorite turntable display stands.