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SunRiseWatch

Jana Halčinová, Lukáš Haninčík, Marek Krátky

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Problem

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  • problem ⇒ application!
  • some applications need internet (location determination)
  • no internet ⇒ unusable app ⇒ problem!

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  • Example: tourism, necessity to go back before sundown
  • No internet, location determination is not possible ⇒ apps need internet connection to find it out

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Solution

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SunRiseWatch!

  • gadget for measurement of time and azimuth (angle) of sunrise and sundown by mechanical setting of latitude, longitude, date and time zone
  • usage: tourism, apocalypse (global internet outage)

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How does it actually work?

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Mathematical explanation

L -> latitude

x -> day of the year, expressed in angles, beginning with the autumn equinox

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The length of the day during the year can be expressed by the following equation:

arccos( tan(L)* tan(0.4092 sin(x))) (1)

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The azimuth of the sunrise can be expressed by the following equation:

arcsin(sin(0.4092 * sin(x))/cos(L)) (2)

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We have approximated these functions using the following equations:

Day length: arccos(tan(L)*0.4339*sin(x)) (3)

Azimuth: arcsin(0.398/cos(L)*sin(x)) (4)

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Mathematical explanation

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For mechanical calculation, we are creating a device that can mechanically calculate the following function:

arccos(A*sin(x)) (5)

x is set by rotating the circle

A is set by the length of the inner arm axis

the result is determined by the two outer arms

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The length of arm A for the length of day is determined by the function derived from (3):

tan (L) * 0.4339

The length of the arm A is determined for the azimuth by a function derived from (4):

0.398 / cos (L)

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Models needed for milling

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Algoritmus

Sunrise and sunset

  1. Set the latitude of the destination (on the left axis)
  2. Set the date
  3. Set the month
  4. Set longitude
  5. Set the time zone
  6. Read sunrise and sunset time (from rotating arms)

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Sunrise and sunset position

  1. Set latitude of destination (right axis)
  2. Set the date
  3. Subtraction of sunrise and sunset time

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Testing

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Location

Sunrise

Sunrise calculation

Sunset

Sunset calculation

Bratislava

7:38

7:41

16:22

16:15

Ponta Delgada

7:58

8:00

17:45

17:30

New York

7:19

7:12

16:51

16:40

  • comparison of sunrise and sunset information obtained from Google and information measured using SunRiseWatch

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  • average error rate (in minutes)
  • Sunrise: 4
  • Sunset: 11

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Advantages

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Disadvantages

  • Size
  • Necessity of adding multiple parameters
  • Necessity of stability during the setup
  • Necessity of “sharp eye”

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HOWEVER...

  • The problem we solved is not trivial at all ⇒ non-trivial problem requires a non-trivial solution!
  • Although the user has to take multiple actions, their effort has been reduced to the necessary minimum
  • We have managed to determine sunrise and sunset with very high accuracy using only:
  • equations
  • cutters
  • Plexiglass
  • a few screws (so that the gatget won´t fall apart)
  • a piece of rubber

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Potential upgrades

  • Product labels with better visibility
  • Smaller size of the product
  • Enhance precision by adding more specific labels
  • Other precision enhancements
  • Improved sliding arm sliding
  • Replacement of the elastic band insulating the sliding mechanism with another mechanism in order to provide easier sliding of the whole mechanism

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Finally, few more pictures

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