The clock project will always be a hacker staple, giving the builder a great way to build something useful and express their individual flair. [Mosivers] was undertaking a build of their own and decided to go for a twist, creating a timepiece with a photochromic display.
The clock uses an Arduino Nano to run the show, hooked up to a 4-digit, 7-segment display that is custom built on protoboard. By using ultraviolet LEDs and placing them behind a reactive screen, it’s possible to create a unique display. The clock can be used with two different screens: a photochromic display created with UV-reactive PLA filament that turns purple when excited by UV light, and a glow-in-the-dark screen for night use.
It’s a fun twist on a simple clock design, and the purple-on-white digits are sure to raise some eyebrows among curious onlookers. Photochromic materials are fun to play with, and can make eggs and glass much more visually interesting. Video after the break.
Huh, this is kind of brilliant. Nice work! I wonder if you could use a laser to raster out graphics on something like this…a slow scan line (like a clocked down CRT) would be a reeeaaall cool look.
Using the UV-reactive filament is a neat idea. I back-lit some white PLA on a project that has been running for about three years now, and the UV in the blue LEDs has actually turned the plastic yellow right in front of the LEDs. It’s visible on the outside face when the LEDs are off. I wonder if that will happen at an accelerated pace on this clock.
A neat take on this idea would be to use a glow in the dark disk that slowly rotates. At the bottom of the disk would be a row of LEDs writing the current time. This would take fewer LEDs and could be made higher resolution, along with hiding the light from the LEDs for nighttime use.
I played with this a while back at https://hackaday.io/project/28177-sort-of-e-ink-kinda. Unfortunately the color changing PLA stopped doing that after a thousand cycles or so