[HN Gopher] Show HN: Belshazzar's Clock, luminous paint night clock
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Show HN: Belshazzar's Clock, luminous paint night clock
Author : mkarliner
Score : 52 points
Date : 2025-01-08 11:14 UTC (11 hours ago)
(HTM) web link (blog.karliner.net)
(TXT) w3m dump (blog.karliner.net)
| Cerium wrote:
| Sweet hack, thanks for sharing. I remember playing in the dark
| with luminous paper as a kid - If I remember correctly, I would
| take a hacked up disposable camera and put various objects in
| front of the paper before triggering the flash.
|
| I imagine that you could improve the consistency and readability
| some by modeling the state of each pixel of paper. That way when
| the drum comes around you can compensate the exposure per pixel
| based on the current state to achieve better uniformity of
| display. In this way you could do exposure compensation on each
| row of output to make the display equally bright top to bottom.
| This would be similar to how a "no-refresh" epaper display works.
| mkarliner wrote:
| Interesting, I'll have to think about that. Actually, with rare
| earth paints, the big issue is persistence, which is rather too
| long. In the current script, I only turn the drum 1/4 turn, so
| it takes roughly 4 minutes to illuminate the same patch again.
| Otherwise the lowest digit tends to be blurred because it is a
| combination of the last two values.
| thanatos519 wrote:
| Have you tried 360nm LED? The higher orbitals drop faster or
| so I've been told.
| mkarliner wrote:
| Another interesting suggestion to think about. Thanks.
| xattt wrote:
| > I would take a hacked up disposable camera
|
| Memories unlocked of extracting the flash unit from disposable
| cameras to flash on demand.
| rob74 wrote:
| Looks cool, but if the "writing on the wall" is only supposed to
| be the current time, there are enough (much more mundane-looking
| of course) alternatives, e.g. https://www.walmart.com/ip/Emlimny-
| Digital-LED-Projection-Al...
| Terretta wrote:
| Indeed. And the red most use (a) doesn't blow your night
| vision, (b) isn't visible through your eyelids. (I recommend
| one where, if it also displays the time itself, shows the time
| in red too, at least when the room's dark.)
|
| Once you've had this on the ceiling for a while, it's annoying
| to have to look for time on a nightstand or your wrist.
| gigaflop wrote:
| Not sure if you can get this where you are, but I've personally
| used some of these glow powders, and they get _very_ bright:
| https://unitednuclear.com/glowinthedark-items-c-101_45/
|
| I've had Aqua and Green, and they look gorgeous.
| mkarliner wrote:
| Thanks, I'm in the UK, and US-UK shipping is horrendous, but I
| may give them a try.
|
| Right now I'm try to find a longer persistence photochromic for
| the daylight version.
| froh wrote:
| fun :-)
|
| say, why don't you move mirrors but the whole laser?
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