RACHEL MARTIN, HOST:

If you've read the "Harry Potter" series, then you know that the Weasley family's clock is one of those magical objects that makes you think - man, that could be really useful. It works like this. Instead of having two hands, it has a hand for every member of the family. And instead of pointing at the time, the hands swing around to indicate where each family member is at any given time, for example - home, school, traveling, prison, even mortal peril. Well, a computer science student named Trey Bagley decided that wizards shouldn't be the only ones to benefit from such a clever device. So he made his own version of the Weasley clock for his own family. Trey joins me now to talk about his invention.

Hey, Trey. Thanks for being with us.

TREY BAGLEY: Hi. Thank you.

MARTIN: Can you just tell me - where is the clock? Where's it hanging?

BAGLEY: In the wall of the kitchen, back home in Houston.

MARTIN: Describe this clock to me. How is it different from the Weasley clock? - because it is. You made some modifications.

BAGLEY: (Laughter) Yeah, I had to improvise a little without magic.

MARTIN: (Laughter).

BAGLEY: But in general, there are - we have six members of the family. And there are six hands that can be lit up under each category on the clock face. We all set up rules on our phones so that for different locations or events, it'll change which category we're lit up under.

MARTIN: So tell me what categories you put on the clock.

BAGLEY: So we have home, work, on the way, forest, holiday and mortal peril.

MARTIN: Home, work, on the way - I get all those. What does the forest look like in your family's life?

BAGLEY: That's part of the fun of the project is that everyone gets to categorize it in different ways. So for me, as a Duke student, we have the Duke Gardens just outside of campus. So I'm able to draw a radius around that on the computer and say - if my phone enters this line, then set me to forest.

MARTIN: Huh.

BAGLEY: My mom - for her running trail back at home, it just draw an area around where she runs through. So whenever she brings her phone on that run, she'll be set to forest.

MARTIN: Cool. And what about mortal peril?

BAGLEY: (Laughter) Mortal peril. I think only a couple of us have rules for that one, but we try to find humorous ways to light up that one.

MARTIN: What's your mortal peril?

BAGLEY: My mortal peril is - I'm signed to work for Microsoft next year. And if their stock drops below their three-year low, it automatically sets me to mortal peril.

MARTIN: (Laughter) That's awesome. So let's get not super far into the technical weeds, but let's just explain a little bit how this works.

BAGLEY: All the LEDs inside the clock are all wired up in a string, which is wired up to this little microcontroller chip called the Photon, which can connect to Wi-Fi and receive messages through it.

MARTIN: I understand - so you have three siblings? And you guys are in your 20s, or a couple of them are teenagers still. Was everyone so keen on this? Because when you're a teenager, do you necessarily want your parents or everyone else in the family to know exactly where you are at any given time?

BAGLEY: Right. My sisters weren't too keen, as I predicted. I had to make sure they would all agree to this before we started the project.

MARTIN: How has this worked for your family? Do people really keep tabs on one another this way?

BAGLEY: My mom will tell me that before she goes to bed, she'll check it. And if she sees everyone up at home, then she knows we're all either in bed or in a dorm, and it's a nice little comforting thing.

MARTIN: Trey Bagley, he's a designer of a real life Weasley clock.

Thanks so much for talking with us, Trey.

BAGLEY: Thank you. Transcript provided by NPR, Copyright NPR.