What’s the coolest thing you could build for a Harry Potter fan, aside from a working magic wand or Quidditch broomstick? We would have to say a Weasley clock that shows the whereabouts of everyone in the family is pretty high on the list, especially if that fan is a wife and mother.
Here’s how it works: they’ve set up geofences to define the boundaries of home, each person’s school or workplace, and so on. The family’s locations are tracked through their phones’ GPS using Home Assistant, which is hosted on a Raspberry Pi. Whenever someone’s location changes, the Pi alerts the clock over MQTT, and it moves the 3D-printed hands with servos.
The clock has some interesting granularity to it as well. As someone gets closer to home, their pointer’s distance reflects that in its proximity to the Home slice. And Home itself is divided into the main house and the shop and reflected by the pointer’s position.
We particularly like the attention to detail here, like the art poster used for the clock’s face that includes all the Weasley’s whereabouts in the background. It’s built into a thrift store grandmother clock, which is smaller than a grandfather clock but no less majestic. In the future there are plans to implement the clock’s chimes to announce that someone is back home.
No matter what you’re into, the whereabouts clock idea can probably fit that universe. For instance, here’s one that uses LEGO mini-fig heads to locate roommates.