wardnica / solarlib

Arduino solar position calculator

Currently this library only compiles under the Teeny 3.0 modified version of Arduino 1.0.2 provided by PJRC.com, and relies on the modified Time library that is packaged with the PJRC version of the Arduino software. See the PJRC forum for downloads: http://forum.pjrc.com/forums/6-Announcements

To install this library, place the folder containing all of the Solarlib files into the libraries directory in your Arduino folder (Mac) or under the libraries folder inside arduino-1.0.2 (Windows).

/* Solarlib Luke Miller December 2012

• Released into the public domain (originally based on U.S. Govt. products)
• No warranty given or implied.
• A library of functions for Arduino to calculate aspects of solar position
• in the sky using a time value, latitude, longitude, and time zone.
• Output includes estimates of current sun elevation and azimuth (position in
• the sky), sunrise, solar noon, and sunset times for the current day, and
• various other statistics for the sun at the given time. Results should be
• accurate for the years 1901 to 2099, for locations between +/- 72 latitude.
• Calculations are based on spreadsheet and information found at:
• http://www.esrl.noaa.gov/gmd/grad/solcalc/calcdetails.html
• Initialize the solar calculator using the initSolarCalc() function, which
• lets you specify:
• tzOffset - time zone Offset from Greenwich Mean Time (UTC). Time zones

•  		west of GMT should be given negative values. 
  

•  		For example, Pacific Standard Time is -8 
  

• lat - Latitude of the location you want to use. Values north of the

•  		equator are positive, given in decimal degrees.
  

• lon - Longitude of the location you want to use. Values in the

•  		western hemisphere have negative values (0 to -180), given in 
  

•  		decimal degrees. 
  

•  		For example: Monterey, California has lat/lon (36.62, -121.904)
  

• After running initSolarCalc() in the setup loop, you can call any of the
• extractor functions to get the position of the sun and sunrise/sunset times.
• Each extractor function requires a Time value as input, from the Time
• library. The Time is given as seconds since 1970-1-1 00:00 (unix epoch).
• Useful functions, supplied with a time value t as the sole argument:

•  getSAA(t)		- Solar Azimuth (degrees clockwise from North)
  

•  getSEC_Corr(t)	- Solar Elevation, corrected for diffraction (degrees)
  

•  getSZA(t)		- Solar Zenith angle (degrees below straight up)
  

•  getSunriseTime(t)	- Sunrise Time for the current day 	(Time object)
  

•  getSunsetTime(t)	- Sunset Time for the current day	(Time object)
  

•  getSolarNoonTime(t)	- Solar Noon for the current day	(Time object)
  

•  getSunDuration(t)	- Minutes of Sunlight for the current day	
  

•  Many more found below...			 			
  

• WARNING
• Only tested on 32-bit ARM Teensy 3.0. This library will probably fail
• horribly on 8-bit AVR products due to limits in precision of double/float
• values. You can check your results against the NOAA calculator:
• http://www.esrl.noaa.gov/gmd/grad/solcalc/