./backlog: Charlie's blog

meanderings through tidbits of mathsy computery stuff

Building a Weasley Clock


I gutted an old clock, re-painted it, replaced the clock face, and replaced the insides with a some techy stuff that moves the clock's hand to show my location. For those of you who don't want to read this entire post, I've included a video.

Check out the source on GitHub!

What is a Weasley clock, and why make one?

As a child, I really enjoyed reading the Harry Potter books, and I always thought that the Weasley family's clock sounded like a really interesting device. For those who don't know about this clock - it's essentially a magical clock that has a hand for each member of the family, and a number of "locations" around the clock face. The hands point to each family member's location, thus telling you where they all are.

The one that the Weasley family has in the film looks like this:

The Weasley
family's clock

How does it work?

There are several parts that make up the clock;

  • To control the servo that moves the hand, I used a Spark Core - a small, wireless-enabled embedded computing device that's compatible with Arduino code.
  • To track my location, I used the OpenPaths location API - which I linked with my mobile phone.
  • To tie it all togetherI wrote some Python code to sit on my web server that regularly fetches my OpenPaths data, checks proximity using a Great Circle Distance function, and sends cloud commands to the Spark Core to update the position of the clock hand.

Building the Clock

Small embedded computing systems have got massively cheaper in the last few years, and I have a bit of free time on my hands every so often - so I hit upon the idea of building one a couple of years ago.

It took me a while to get the parts together and they've been sitting around in my spare room for... well, probably about a year. Until last weekend, that is - when I decided to break out the chalk paints, buy a Spark Core, and finally put it all together.

Writing the code was actually the quickest and easiest part! The longest part of the process was actually getting the clock, sanding it down, painting it and putting it all together. I thought it might be interesting to include some photos of the build, so I've included some below.

Deciding on the locations was hard - cutting out the stencils was a nightmare because there were so many potential mistakes, so I decided on only three locations to put on the clock face:

  • Home
  • Travelling
  • Work

I might add more later on if I feel like destroying any more stencils...


Clock Pre-Sanding


Clock after Painting the Body

Stencilling the Clock Face

Clock Part-Way through Stencilling

The Finished Body

The Finished Clock Body


Wiring the Servo Up

Sticking it all Together

Putting the Motor in the Clock

The Finished Product

I've included a short YouTube video of the clock cycling through locations at the top of this post!

Enjoy :-)