LED Hourglass Moves Like The Real Thing

If you want to waste time in a meaningful way, get yourself an hourglass. It’s simultaneously mesmerizing and terrifying to sit there and watch the seconds slip through the threshold that separates possibility from missed opportunity.

[Ty and Gig]’s LED hourglass is equally beautiful to watch. It doesn’t actually tell time, but that’s perfectly fine by us. What it does do is animate the LEDs to approximate grains of sand in gravity, no matter how the hourglass is tilted.

In either vertical orientation, the sand falls as long as there is some in the top. When the hourglass is horizontal, the LEDs settle just like real sand does. [Ty and Gig] achieved this with a whole lot of code that breaks the animation frames into structure arrays.

By contrast, the hardware part of this build is fairly simple: all that’s needed to replicate this build is some RGB LEDs a beefy power supply to drive them, an accelerometer, and a microcontroller.

[Ty and Gig] were planning to use an ESP8266, but misplaced it and went with an Arduino Mega instead. (You know what they say — buy a replacement and the one you lost will turn up almost immediately.) The beautiful frame is made from leftover purpleheart, a hardwood that turns purple with exposure to air. Check out the build video after the break.

Too lazy to reset your hourglass every hour? Here’s one that flips itself.

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Improved Hourglass Entropy

improved-hour-glass-entropy

[Wardy] built himself a high quality entropy source with parts he had lying around. It’s based on the hourglass entropy project we saw in a links post earlier this month. Just like that project, he is bouncing a laser off of the falling sand and reading the result. But he brings a few innovations to the party, and has test results to back up his work.

The first change is an obvious one; motorize the hourglass so that you don’t need to flip it by hand. We thought this might mess with the laser alignment but the clip after the break proved us wrong. He changed up the sensor, using an LED connected to the base of an NPN transistor. The next change was to mount the light sensor at an angle to the laser rather than straight on. This picks up reflections of the laser and not the direct beam itself, resulting in a wider range of readings.

He used an Ethernet shield to get the system on the network. It’s pushing 420k random numbers per second and was tested with the DieHarder suite. It didn’t get a very high score, but it did pass the test.

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