This E Ink Display Tracks the Phases of the Moon

It’s virtually impossible to overstate the importance that the Moon — Earth’s moon — has had on human history and culture. Mythology and religion aside, lunar cycles are have been the basis of many calendar systems, they dictate how well we can see at night and how well we can navigate after the sun goes down, and they gave us valuable insight into astronomical mechanics. But not many of us these days bother to keep track of lunar cycles. As part of his journey to learn more about electronics, Jacob Tarr designed and built an E Ink display to track of the phase of the moon.

E Ink displays, more than pretty much any other kind of display, have extreme advantages and disadvantages. They’re slow to update, have relatively poor resolution, and tend to max out at just three colors. But they’re incredibly efficient—particularly because they only require power when the display is being updated. They’re also very readable, even in the kind of bright light that would cause a lot of glare on something like an LCD. In this case, the advantages outweigh the disadvantages. That’s because it doesn’t need to update frequently, and the low power requirements make it possible to run the device on a battery for a week or more.

In this case, the screen is a 4.2” three-color ePaper display made by Waveshare that has a resolution of 400 x 300 pixels. That’s controlled by an Adafruit ItsyBitsy M4 Express board via an Adafruit eInk Breakout Friend. Power is provided by a 2200mAh lithium-ion battery through an MCP73831T power management IC. It was prototyped on a breadboard and then Tarr designed a custom PCB to connect those components together in a compact package. All of those components were housed within a minimalist 3D-printed enclosure. Tarr programed the device using CircuitPython to pull the moon phase data from NASA. It’s setup to show the moon, as well as information about the moon’s current status.