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I'm doing a project on control Automation, where the purpose is to control blinds automatically based on current weather conditions. I plan on doing this by taking into account whether it is Sunny or Cloudy at the current time. My question is the following:

How do I determine a break point of solar radiation at a certain time. The break point will determine whether it is Sunny or Cloudy.

I believe there exist an ASHRAE Table that describes this data. I'm just not sure where to find it.    


You might want to consider applying a radiant temperature sensor or a light level sensor, in conjunction with a normal room temp sensor.

TMY data files are available online for most areas and will list the hourly variation of direct solar radiation.  Also google the instructions that explain how to parse the data from the file.   

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