Building an E-Ink Joke of the Day Fridge Magnet

My 6-year-old is obsessed with jokes and often asks me for any new ones I’ve heard. I usually can’t remember many, which gave me the idea of creating a fridge magnet to display jokes in our kitchen. This is the finished product:

I wanted a highly readable and battery-efficient screen so I decided on the paperd.ink Classic. It has a 4.2-inch E-ink display, 1900MAh battery, and an Arduino ESP32 all on a slim PCB, perfect for my use case. I have no connection to paperd.ink but I was very happy with their product (even though it took a while to ship to me).

I wrote an Arduino sketch that fetches a new joke from the Official Joke API every 6 hours, updates the screen, and then immediately goes into deep sleep to preserve the battery (allowing it to last months between recharges). It also displays a rough estimate of the charge remaining in the bottom corner.

Next, I designed a custom 3d-printed enclosure using Fusion 360. This way I could embed magnets in the enclosure to attach to the fridge. I used a total of eight magnets to prevent it from sliding off.

I’m really happy with it and my son loves waking up each morning to a new joke. The full build guide is here.