Moon Phase Display

Made on a Glowforge
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Here’s a device I made, just because. It’s an electromehanical display showing the current phase of the moon. Overall, it’s about 13" x 15" in size.

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The terminator that divides the lit portion of the moon photo from the portion that’s in shadow is the strap part of a stainless steel “zip tie.” It runs between two pivots, one at the top of the moon photo and one at the bottom. The strap begins in the top pivot, crosses the photo of the moon, and passes through the pivot at the bottom. How much of the strap’s length is exposed as it crosses the moon photo and the angle it makes as it emerges from the pivot at the bottom are controlled by two geared down stepper motors. Because the strap is springy, it’s possible to approximate the shape of the terminator on the real moon by adjusting the strap’s exposed length and angle of emergence. In the photo above, for instance, the strap is forced to emerge pointing to the left and enough of it is shoved out to force it to curve appropriately (more or less) for today’s moon phase…

To light the moon photo there are two white LED “cobs,” one hidden under the front panel on the left, and the other on the right. Which is lit and how brightly depends on the phase of the moon and how bright the ambient light is in the room. When the lights are off at night, for instance, the display’s lights go out.

Here’s what the device looks like from the back.

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The shiny thing in the middle is a stepper-motor pulley driving a toothed belt that adjusts the angle of the lower pivot, the blue circle just below it. Attached to the pivot is a leadscrew assembly driven by another stepper motor that controls how much of the strap is shoved out. You can see the leadscrew assembly sticking out at about the 8 o’clock position

Here’s a better view of the leadscrew assembly and the lower pivot drive.

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To make it all go, I used a Raspberry Pi Pico W microcontroller, a custom PCB and a bunch of custom code. The microcontroller connects to the Internet to get the time and date which it needs to calculate what the current moon phase is.

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I have no real use for a Luna phase clock but how you approached this is awe inspiring.

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I don’t actually understand your descriptions of the workings, but that’s so cool!

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So cool. Love it.

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I love the constant symbolism of the moon. Very nicely done.

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Wow, most impressive!

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If one is living on the coast, the tidal timing can be very useful, particularly if involved in boating. Reminding me of Bahamian saying “If you don’t go out with the Tide, the Tide don"t care. The Tide goes out anyway.” this has many non-tidal implications.

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That’s amazing. And here, I have been pondering for about 2 years now, whether or not I want to even put in the work to make a normal wall clock. Great job.

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That took a lot of work to figure all that out (and waaayyyy beyond my ability and comprehension). That looks amazing! Thanks for showing us!

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I’m glad people found the display interesting. I had a great time designing it – figuring out how to divide the lit side from the shadowed side with something I could actually make.

For anyone interested, the physical parts are in onShape, here.

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This is really cool. Am I understanding correctly that it lights up? Any chance we could see a photo in the dark?

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That’s amazing!

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I too would love to see a better photo of it in use if you are so inclined.

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Here’s one I took about a half hour ago – it just got dark where I live.

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Not a whole lot of the moon is lit since we’re near the end of the lunar cycle. But you can see the final little waning crescent. (There are still low room lights on where it is because if I turn them out, the display goes dark so as to not be obnoxious at night)

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That’s awesome! I’m an astronomy professor, so I teach lunar phases a lot. This is a fabulous visualization. :grinning: (Apparently, I’m logged in on my husband’s account…oops).
—Katie Berryhill

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That is really slick.

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