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Let us start with this episode of StarTalk Youtube channel. Here Neil deGrasse Tyson explains the reason why all mechanical clocks (almost) have hands moving in the same (clockwise) direction.
This episode only fifteen minutes long, but in case you are too busy to watch it I'll provide short brief.
2. Shadow of sundial moves clockwise only in Northern Hemisphere. In Southern Hemisphere shadow of sundial moves counter-clockwise. If mechanical clock would be invented in some place to the south of the equator clock scale and clock hand movement would be opposite of what we have now. This picture of a backward clock shows us how southern invented timepiece may look. You can buy such clocks on Amazon and after some time even get used to it.
3. Apart of clockwise and counter-clockwise movement Neil in this episode discusses how invention of digital clock changed human perception of the time. Mechanical clock makes human think about time from geometrical perspective. Angle between axis and clock hand corresponds to the time which already passed or left. Recent invention of digital clock creates illusion of precision but deprives us from geometric association.
LED clock presented here is a hybrid. It works partially as a regular (like invented in Northern Hemisphere) clock and partially as backward (invented in Southern Hemisphere) clock. And I want to think that it is a hybrid in other aspect: while be digital it still gives some geometry perspective. To understand this timepiece interface I invite you to play with the web model: Half-Dial-Clock-Model Link
Model has four clocks, which all synchronized and show the same time.
1. First clock at the left is the regular analogous clock. Nothing to comment here.
2. Second clock works similarly to the first, apart of the fact that in place of clock hands there are circular arcs. Normally clock shows time by angles between vertical axis and hands . This arc clock shows time by angles occupied by arcs (outer arc for minutes, inner arc for hours ). Arcs start at twelve mark and grows clockwise.
3. Third model is a half-dial version of ark clock. For hours less than six and minutes less than thirty reading the time is not different of the previous clock. Arcs start at twelve mark and grows clockwise. But when hours are in the range 6..12 or minutes are in the range 30..60 there is the change. Hands of the regular clock under these conditions are positioned at the left side of dial. But for this arc clock there is no left side. Arcs here occupy the same right side but there are change of starting points and direction where arcs grow. Under these conditions arcs start not at the twelve mark but at the six mark and they grow counter-clockwise. That way clock show hours from 6 till 12 and minutes from 30 till 60. In other words this clock works closer to normal clock for hours from 12 till 6 and minutes from 0 till 30. Otherwise this clock works closer to backward (Southern Hemisphere) clock.
4. Fourth clock is similar to the previous model but arcs are dotted not solid. This clock does not need dial marks: dots itself are marks. White dots of inner half-dial shows hours, green dots of outer half-dial show time with five minutes precision. Additional one minute precision achieved by a color of the last dot of minute arc. Just add color reading to the time provided by green dots (for cyan add +1, for purple add +2, for red add +3, and for blue add +4 ). This last clock model is very close to the real LED based clock (just substitute dots with LEDs).
Model allows to play with clocks dynamically. Three time modes exist:
1. Manual mode. Top slider allows to change clock time.
2. Real time mode. Clock shows current local time on the machine where browser is running.
3. Simulated mode. Time change is simulated (bottom slider allows to increase or decrease simulation speed).
Real LED clock is different of dot half-dial model by having two more lighting elements.
1. Central LEDs changes color each fifteen seconds (cyan, purple, red, and blue). When clock is in set mode this LED is dark.
2. LED on the left part of the clock is AM/PM flag. This LED is OFF during AM half of the day and ON during PM half.
Clock is built around Atmega328p microchip. Circuit diagram, C program and Microchip Studio project you can find in the Git repository: https://github.com/jumbleview/Clock16
And one last thing to say about the project. The clock has seven LEDs on the hours scale and seven LEDs on the minute scale. There is known psychology phenomenon: "Magic Number Seven, Plus or Minus Two". Invented by psychologist George A. Miller, it argues that seven is number of items human can keep in short-term memory to operate. Anything significantly more is out of cognitive capabilities of average person. In this regard clock presented here looks just right. I believe it is easy enough to get used to its interface.
