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Log 1: Maths, Points & Splines

A project log for Solar Analemma Chandelier

A chandelier of LEDs, WiFi and CNC'd MDF.

doigaldoigal 04/21/2018 at 20:470 Comments

The first issue that needed to be solved was to calculate the accurate solar positions.

The position of the sun at any time and location can be calculated thanks to whats known as the Equation of Time.

Thankfully, NOAA have an Excel sheet which takes location, timezone, dates and local time as inputs, and gives the Solar Analemma (amongst other outputs)  for the entire year.  Whilst this is great, I don't have the room for 365 LEDs, so I have to scale this down a little. Eventually I settled on 96 LEDs, which worked out to 1 LED per 3.8 days.

A problem that comes up here is that the true shape of the resulting spline is extremely narrow and long (An aspect ratio of 7:1), which isn't the most practical of shapes to use as a light. A little artistic licence was taken to bring it down to slightly more square ~3:1.

Now that the LED points are defined, and wanting to avoid any extra work in Fusion 360, its easy from here to mathmatically offset the line generated from the LEDs to generate the lines for the wood cuts, the perspex inset and construction lines to wrap the text onto.

These point files are then imported to Fusion 360 as splines for the 3D part of the modelling.

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