AVR-Chat

At 08:32 AM 7/15/04 -0400, you wrote:
>I didn't read all the thread on this but somewhere I saw someone talking
>about 100%. If you only log the time when a certain amount of change is is
>make you should know ahead how many readings you will have logged.

That assumption is valid for monotonically changing systems.  Since we 
talking about daylight over a period of a week the signal is certainly not 
monotonic (well on most of the globe).


>This may give you a different approch to documenting when changes happen.
>Doing this you will probably have to log both the time and reading because,
>like the temperature above, sometimes the temperature would increase 2
>degrees.

Which leads to the other issue.  If the signal changes frequently (and if 
you include the effects of shadows it certainly can) then it takes more 
room to store delta+time than it does just to store the signal.

On the other hand I would expect the plants themselves to be rather 
effective low pass filters (There is a high school science project in that 
assumption), and recording some sort of filtered average of the light 
intensity over a longer sample period should be as illuminating as 
recording higher frequency intensity samples.

I did a quick search (via google) and the one abstract I found suggested a 
hyperbolic response to light intensity.  That would suggest an RMS filter 
would be quite appropriate.  I didn't find any references to periodic light 
variations (of periods < 24 hrs anyway) having any effect but it really was 
a rather cursory search.

>Hope I'm not being redundant,

I don't think so, this approach probably would work for the moisture 
sensors.  I suspect the soil/plant system has a low frequency response.


" 'Freedom' has no meaning of itself.  There are always restrictions,
be they legal, genetic, or physical.  If you don't believe me, try to
chew a radio signal. "

                         Kelvin Throop, III