Hour glasses have long been a way to indicate time with sand, but the one-hour resolution isn’t the best. [Erich] decided he would be do better and made a clock that actually wrote the time in the sand. We’ve seen this before with writing time on a dry erase board with an arm that first erases the previous time and then uses a dry erase marker to write the next time. [Erich]’s also uses an arm to write the time, using the tip of a sea shell, but he erases the time by vibrating the sandbox, something that took much experimentation to get right.
To do the actual vibrating he used a Seeed Studio vibration motor which has a permanent magnet coreless DC motor. Interestingly he first tried with a rectangular sandbox but that resulted in hills and valleys, so he switched to a round one instead. Different frequencies shifted the sand around in different ways, some moving it to the sides and even out of the sandbox, but trial and error uncovered the right frequency, duration, and granular medium. He experimented with different sands, including litter for small animals, and found that a powder sand with small, round grains works best.
Four white LEDs not only add to the nice ambience but make the writing more visible by creating shadows. The shells also cleverly serve double duty, both for appearance and for hiding things. Shells cause the arms to be practically invisible until they move (well worth viewing the video below), but the power switch and two hooks for lifting the clock out of the box are also covered by shells. And best of all, the tip that writes in the sand is a shell. There’s plenty more to admire about the cleverness and workmanship of this one.
We also have to wonder at what other dioramas are possible with this setup. How about a Halloween setting with a skeleton emerging from the sand? Perhaps white sand would make good snow for a Christmas setting?
Here’s the sandclock at an earlier testing stage but where you can better see the workings in action.
[via Adafruit]
“Perhaps white sand would make good snow for a Christmas setting?”
I hope HAD has considered the endless bad jokes and photoshopped pictures regarding which medium one would be using as ink.
A penguin stylus would be pretty cool (and a lot more presentable): http://www.star28.net/snow.html SFW
He should write the time backwards
Now make one that also works while hanging on a wall.
I was thinking that also. How about same exact design but 45° mirror with everything backwards to reflect forwards?
Hmm. I’ve been looking for a nice application for the graviton diodes. They are tricky. I lost the first batch outside. Went straight up.
The arm is impressive in the way it is decorated. I was looking at the project and was wandering how he was going to write the time… Nice job.
Me too it is camouflaged very well.
Same here. Even when it retracts I quickly forget that it’s there and have to look hard for it. He did a really nice job.
maybe a rake instead of the vibrator? that noise would get irritating once a minute. neat though!
This is very clever. And yes, the vibration noise is probably the big drawback; cool nonetheless.
It looks great. One change I would make is to have the arm erase the numbers itself so you wouldn’t hear vibrations, and maybe even look into brushless motor control so the unit would be completely silent.
Then I would build it into a glass topped coffee table. Man, I’m full of great ideas I’ll never do.
Oh, and also make the arms look like a crab.
Sorry, but the arms are some weird, because they are hiding like a predator waiting to eat a fish.
Maybe if the arms were a claws of crab, they will be looked less weird.
But, seriously the clock is awesome.