Slashdot Mirror
Digital Clock Without Electricity or Moving Parts
NerdMachine writes "Throw away those slide rules and embrace the digital age. The Digital Sundial is a 10 year old invention on display in Sundial Park (Genk, Belgium), Deutsches Museum (Munich Germany), Kölnisches Stadtmuseum (Cologne, Germany), and Martha's Vineyard, USA. You need to pivot it to adjust daylight savings time. If you can't visit one of these, Digital Sundials International can sell you one for US$12,000+, or you can buy a pocket version for under US$100 for that special nerd in your life."
Or New York City. Wasn't there something recently about how the buildings are so tall they're blocking out the sun?
Keep your eyes to the sky.
RTFA. From the product info:
Sunlight is cast through two cleverly designed masks in the shape of numbers that show the current time of day
Its a cool idea.
No, it doesn't. It consists of two plates with lines, which either transmit or block light depending on the specific location of the sun (the viewer needs to be at a specific position).
The visible lines then align in such a way that you can read off the time in digits. Hence 'digital'.
Although the clock is set to read in 5 or 10 minute intervals, depending on the time of year it could still be up to 16 minutes fast or slow compared to your watch or clock because of the Equation of time. Our sense of time is so conditioned by our dependence on the mechanical/digital that solar time is now percieved to be "wrong".
from the companues website
That's not a digital clock in any sense of the word.
It shows the time with discrete digits, so it is digital.
From Wikipedia: [Digital] comes from the same source as the word digit: the Latin word for finger (counting on the fingers) as these are used for discrete counting.
If you follow the manufacturers link and then get the instructions, it explains how it works. But here it is in a nusthell (as I understand it).
1) Make holograms of the digits of the time in question (lots of holograms).
2) Take the holograms and cut them into strips.
3) Take some of the strips and glue them back to make one hologram
4) Put a mask with slits in it over the hologram. At a certain time the light will only illuminate the hologram strips that coorespond to the current time.
Pretty neat, if you ask me (too bad you didn't).
"-1 Troll" is the apparently the same as "-1 I disagree with you."
I can't quite figure out how to use your list of objects to make one of these. The best I can figure out is that it involves taking all the objects except the laser printer and dumping them in the trash. Then you just look at the display on the laser printer and read the time. Am I missing something?
Assuming you wern't just trying to be funny.
The core of each digit of the "digital sundial" is a sandwich composed of:
- A grating with vertical black/clear bars.
- A layer of glass. (Thickness varies depending on how fast the digit should cycle - the thicker the faster.)
- A second grating with a more complex set of bars that I'll describe later.
- A frosted glass "screen" to diffuse the light for viewing from all angles.
The thickness of the bars on the first grating is such that, if the digit goes through N changes, the clear band is significantly less than 1/Nth the width of the clear band plus the dark band. (To get the appearance of the various digits to match, all of the upper gratings have the same light/dark band width ratio, determined by the digit with the most states.)
Stacking the first grating on the glass produces a band of light stripes on the bottom of the glass that slides sideways as the sun moves. The spacing of the bands and the thickness of the glass are such that the bands move by one band-spacing in one cycle-time for the digit. The glass both holds the spacing between the gratings constant and reduces the angle through which the light moves, so the clock produces a readable image for nearly 12 hours, rather than being really dim near sunrise and sunset.
For every light/dark band pair in the upper grating there are N bands in the lower grating. Each band is a stripe through the image of one of the digits, cycling through the N digits. As the sun moves, the bands move across this pattern, sequentially being "stenciled" by a different digit.
The light coming out of the lower grating strikes the frosted glass "screen" and is diffused sideways, so the clock can be read from many angles.
You use the laser printer to make the gratings, by computing their appearance and printing them on overhead-projector foils.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way