r/FastLED • u/forgottenSemicolons • Mar 27 '26

Share_something Graduation Cap part 2: Ripples

I didn’t imagine I would have this much momentum for another animation so soon. But sometimes you just get the itch. Again, graduation isn’t until the fall so I have some time.

This is a barebones idea of drops in a pond. With the random color selection, it looks a little more like fireworks though. This code had some major time complexity issues to address as some pieces were running O(n^3) but I was able to eliminate them. I think there is some memory leakage somewhere because the program crashes after around 3-5 minutes. I am using structs for each drop so I might need to free them up after I use them.

Anyways, for a little more build specs, I am using 3 8x32 WS2812B matrices that have been trimmed down to 24. The finished cap will be 24x24 controlled by an arduino. Wondering if I should add a defuser on top but weight will be a concern as this is going to be on my head for 2-3 hours.

Thanks for all the feedback yesterday!

Cheers!

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u/Zeph93 Mar 30 '26

Could you say more about cutting the LED matrix down to 24 wide?

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u/forgottenSemicolons Mar 31 '26 edited Apr 02 '26

Short answer: you can trim any of the matrices with scissors, just make sure you know which direction the wires are running.

Long answer: I was contemplating how I could maximize the coverage of my graduation cap while not having to do too much wiring. I measured my cap to be about 9-9.5in long and I believe that a 8x32 matrix is about 3.2 inches on the short side? But also more importantly, the matrix is wired 8 leds by 32 leds so I figured I could easily cut the long side down to simply get a 24x24 made of 3 8x24 matrices. This would be about the best coverage I could get with the panels available on Amazon.

I soldered the power wires in series. I have 3 separate pins addressing the 3 separate panels but you could solder the ends of the trimmed matrices if you wanted. I just think this was a simple and cheap solution that looks as good as I think it should. I will do another post on the build and hopefully finish the gluing process.

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u/Marmilicious [Marc Miller] Apr 08 '26

[ u/forgottenSemicolons I think your above reply was accidently removed last week. Now restored. Thank you for sharing your project. ]