The Potterverse is chock full of interesting magic technology and one of the coolest examples is the “clock” that the Weasleys have in their home. Instead of indicating the time, the hands on the Weasley clock point towards each family member’s current location. Similar technology does exist in the real world in the form of apps like Find My Friends for the iPhone. That app lets you see the location of any person who chooses to share that information with you. But it is way more engaging to see those locations on a Weasley clock and lmjd14’s Instructables tutorial will walk you through how to build your own.
The fictional Weasley clock relies on magic and can therefore find the location of each family member’s body. That’s impossible with today’s technology, but we can achieve similar results by tracking phones. That is almost as good as magic, because most of us keep our smartphones within arm’s reach at all times. The idea here is to track each family member’s phone’s location, use geofencing to determine which predetermined place they’re at, and then indicate that place on a clock-like device. You can make that happen yourself using the smartphones you already own, a free service from Adafruit, and a handful of affordable electronic components.
This Weasley clock is controlled by a Wemos D1 Mini, but you can use any other ESP8266-based development board. This version has indicators for two people and requires a SG90 micro servo motor for each. If you have more people you want to track, you just need more servos. There are instructions for how to replicate the plywood “clock” you see here using a laser cutter and 3D printer, or you can use whatever tools are available to you to build something similar. Each person’s phone will need to be setup with geofenced areas for each location within the Tasker app. The app will then send the current location to the Adafruit IO service via an MQTT message. The ESP8266 is programmed to periodically retrieve that data from the Adafruit IO service and will move the appropriate servo motor arm to the corresponding point on the clock face. If you’ve always wanted your own Weasley clock, this an inexpensive way to get one.