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Solar Arduino tracker (Quelltext anzeigen)
Version vom 2. März 2011, 14:16 Uhr
, 14:16, 2. Mär. 2011keine Bearbeitungszusammenfassung
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German version [[Sonnenstandsberechner (für sun tracker devices)]]
German version [[Sonnenstandsberechner (für sun tracker devices)]]
+=General considerations=
+To calculate the solar position with a microcontroller (on a fixed geographic place)
+you have to solve two problems:
+The controller needs a time device (typically a battery buffered chip like in a PC)
+and it needs a reasonably simple algorithm to calculate solar azimuth and
+elevation from date, time and geographic position (longitude and latitude).
+An algorithm which works on a PC might have problems on a microcontroller.
+For instance, on Arduino you must take into account that
+''double'' data type has the same precision as float (IEEE 23 bit mantissa)
+
+==Get the Time==
To get Greenwich Time (aka UT) I use a DS1307 chip.
To get Greenwich Time (aka UT) I use a DS1307 chip.
Following the description of http://www.glacialwanderer.com/hobbyrobotics/?p=12
Following the description of http://www.glacialwanderer.com/hobbyrobotics/?p=12
−it worked immediately. Did not find any 2.2K resistors, it worked with
+it worked immediately. Did not find any 2.2K resistors,
−4.7K as well.
+4.7K ones are just as fine.
I have taken the code from this site and tucked the complexity
I have taken the code from this site and tucked the complexity
into an Arduino libary (DS1307.h)
into an Arduino libary (DS1307.h)
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The formulas for calculating the [http://en.wikipedia.org/wiki/Julian_day Juliand Day]
The formulas for calculating the [http://en.wikipedia.org/wiki/Julian_day Juliand Day]
are not working properly on Arduino due to reduced double precision.
are not working properly on Arduino due to reduced double precision.
−(doubles have the same precision as floats on Arduino)
+(Therefore, I have adapted them (expecting only Julians dates from 1.Jan. 2000).
−Therefore, I have adapted them (expecting Julians dates from 1.Jan. 2000).
These calculations I have put into another library (Helios.h)
These calculations I have put into another library (Helios.h)