Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!ncar!gatech!emcard!stiatl!john
From: john@stiatl.UUCP (John DeArmond)
Newsgroups: sci.electronics
Subject: Re: Light Duration Meter
Message-ID: <4175@stiatl.UUCP>
Date: 9 Apr 89 02:43:39 GMT
References: <102@raider.MFEE.TN.US>
Reply-To: john@stiatl.UUCP (John DeArmond)
Organization: Sales Technologies Inc., a Dun & Bradstreet Company
Lines: 34

In article <102@raider.MFEE.TN.US> root@raider.MFEE.TN.US (Bob Reineri) writes:
>I've recently planted our first garden, and being the computer nut that I am,
>love to keep records. The rainfall and temperature are easy enough to get. The
>other item I would like to track is the amount of sunlight the garden gets on
>a daily basis. I am entering all this into a database so I'll have something
>to ponder over the next winter.
>
>Does anyone have any ideas on what might be a suitable circuit for this applic-
>ation ? Many moons ago, I was a bench tech, but am now in the software end of 
>it, and the hardware is somewhat foggy. 

What you are interested in is called an integrated solar flux measurement.
NASA spent many  thousands of tax dollars perfecting this measurement
under the guise of solar energy research (had something to do with
Shuttle detonations or something space-related like that :-).  I remember
several articles in the NASA Tech Briefs on this subject.  You should 
hit the library and look thru the indexs.

All the devices I remember output a voltage proportional to the instantaneous
solar flux.  You will therefore need to get a data acquition card (A/D)
for your PC.  Most of these come with some sort of driver software.  
What you would do is sample the device output at suitable intervals and
average it over the interval of interest.   I'd probably sample once
a minute and store the hourly averages in a database.  You could then
calculate a longer average or do other nifty tricks.

I can almost hear the next question.  "How do I digitize plant growthrate?"
:-)


-- 
John De Armond, WD4OQC                     | Manual? ... What manual ?!? 
Sales Technologies, Inc.    Atlanta, GA    | This is Unix, My son, You 
...!gatech!stiatl!john                     | just GOTTA Know!!!