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Solar Arduino tracker (Quelltext anzeigen)
Version vom 9. März 2015, 15:04 Uhr
, 15:04, 9. Mär. 2015→SPA Algorithm
=General considerations=
=General considerations=
For calculation the solar position with a microcontroller (on a fixed geographic place)
For calculating the solar position with a microcontroller (on a fixed geographic place)
you have to solve two problems:
you have to solve two problems:
The controller needs a time device (typically a battery buffered chip like in a PC)
The controller needs a time device (typically a battery buffered chip like in a PC)
==Get the Time==
==Get the Time==
[[Image:Arduino_DS1307.jpg|thumb|timer chip DS1307 with Arduino]]
[[Image:Arduino_DS1307_FritzingExport.jpg|thumb|timer chip DS1307 with Arduino]]
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
4.7K ones are just as fine.
4.7K ones are just as fine.
I have taken the code from that site and tucked the complexity
I have taken the code from that site and tucked the complexity
into an Arduino libary (DS1307.h)
into an Arduino libary (DS1307H.h)
==Calculate Azimuth and Elevation==
==Calculate Azimuth and Elevation==
and you can download it [http://www.psa.es/sdg/sunpos.htm here] as C++ code.
and you can download it [http://www.psa.es/sdg/sunpos.htm here] as C++ code.
There are adaptions neccessary for Arduino, though.
There are adaptions neccessary for Arduino, though.
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 Julian Day]
are not working properly on Arduino due to reduced double precision.
are not working properly on Arduino due to reduced double precision.
Therefore, I have adapted them, expecting only Julians dates starting from 1.Jan. 2000.
Therefore, I have adapted them, expecting only Julians dates starting from 1.Jan. 2000.
These calculations I have put into another library (Helios.h)
These calculations I have put into another library (Helios.h)
Use following program plus libraries for older Arduino IDE (0023 and older):
{{zip|SolarTracker4Arduino.zip|14KB|Version from 09.03.2011}}
For newer Arduino IDE (1.0.1 and later) use instead the following package,
{{zip|SolarTracker4Arduino1.0.1.zip|17KB|Version from 16.01.2015}}
Once you got it running, verify the calculated positions, for instance with
[http://www.sunearthtools.com/dp/tools/pos_sun.php solar position calculator] from
sunearthtools. (Attention: SolarTracker4Arduino does NOT account for daylight saving time (DST),
you have to determine UT (when you set your timer chip) as if there was no DST at all. On the other hand, sunearthtools allow using DST,
and this option is selected by default.
==SPA Algorithm==
==SPA Algorithm==
In this paper methods have been worked out according to the book from
In this paper methods have been worked out according to the book from
''Jean Meeus: Astronomical Algorithms, Willmann-Bell, Richmond 2000 (2nd ed., 2nd printing)''
''Jean Meeus: Astronomical Algorithms, Willmann-Bell, Richmond 2000 (2nd ed., 2nd printing)''
a widely accepted text book for astronomic calculations.
a well known text book for astronomic calculations.
The calculations are, however, very extensive; for Arduino I chose the simpler PSA.
The calculations are, however, very extensive; for Arduino I chose the simpler PSA.
Implementations and references for both algorithms I found thanks to the code from
Implementations and references for both algorithms I found thanks to the code from
[http://klaus.e175.net/solarpositioning Klaus Brunner]. It was also a valuable help for debugging
[http://klaus.e175.net/solarpositioning Klaus Brunner]. It was also a valuable help for debugging
the Arduino implementation.
the Arduino implementation.
--[[User:Hannes.hassler|Hannes.hassler]] 13:36, 3 March 2011 (CET)
--[[User:Hannes.hassler|Hannes.hassler]] 13:36, 3 March 2011 (CET)