A WaterColorBot Water Clock

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We built a evaporating-hand water clock using a WaterColorBot fitted with a Buddha Board. The Buddha Board is a black board with a gray ceramic coating that becomes transparent when wet, so you can paint on it with plain water to make black marks that disappear as the water evaporates.  (And, it fits nicely in a WaterColorBot with the appropriate jig.)

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As a clock, once a minute it draws the minute hand, then the hour hand, and finally the outline of the clock face.

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As the water evaporates over the course of a few minutes, the old minute hands fade away. It’s a neat effect.

And of course, video:

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Open Make at the Exploratorium: Time

555 Footstool   IMG_5331Nixie Clock   Apha Clock Five

This Saturday, we’ll be at the Exploratorium participating in the Open Make event focused on the theme “Time.” We had a great time when we participated in the very first Open Make event, and are glad to see the program continuing with a great lineup of themes this year. This time, we’ll be bringing several clock and time related projects.

The event runs from 10 am to 2 pm, Saturday, February 18, and will feature workshops, maker displays, and Dale Dougherty interviewing several makers on their time related projects. We hope to see you there!

A Bulbdial Clock

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Last year David Friedman published on his blog Ironic Sans an interesting design concept for something that he called The Bulbdial Clock.

That’s like a sundial, but with better resolution– not just an hour hand, but a minute and second hand as well, each given as a shadow from moving artificial light sources (bulbs).
We’ve recently put together a working bulbdial clock, with an implementation somewhat different from that of the original concept.

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Rather than using three physically moving light sources at different heights, we use three rings of LEDs at different heights. Within each ring, we only turn on one LED at a time, so that we only have a single effective light source– it can light up at different places from within the ring. The three rings are located above one another so that they each project light onto the rod in the middle, making shadows of different lengths.

Additionally, for fun and clarity, we used red, green, and blue LEDs for the three rings, making each shadow hand of the clock a different color. Each ring has 12 LEDs, and the 36 LEDs are efficiently multiplexed by an AVR microcontroller that also handles the timekeeping part of the project. Continue reading

The mercury ion optical clock

From 2002-2005 I worked in the NIST Time and Frequency division on a next-generation atomic clock.

The clock is based on a single trapped mercury atom. The most significant result of my work on the clock was a dramatic improvement in its precision, and the report on this progress was finally published this week.

The NIST Press Release compares the accuracy of the mercury clock to the NIST-F1 cesium fountain standard: “The current version of NIST-F1—if it were operated continuously—would neither gain nor lose a second in about 70 million years. The latest version of the mercury clock would neither gain nor lose a second in about 400 million years.”

Read an article from Science News about the paper, or one from Seed Magazine.
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