The Planted Tank Forum - View Single Post - DIY PAR meter, Yeah you heard me
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post #15 of (permalink) Old 11-09-2010, 11:04 PM Thread Starter
No more Bow ties
mistergreen's Avatar
Join Date: Dec 2006
Location: Cincinnati
Posts: 15,538
I received the photodiode yesterday. Got to play with it a little. In this picture, I'm trying to find the right resistor for this set up.

A 4.6K resistor seems to work. I'm calibrating the max output to sunlight.. 1024 (5V) is the max reading and sunlight through a window gives a reading of ~900. So I think I got it.

Mounted the photodiode on a electrical cap

Assembled the jar... This nub in the jar is a problem. It casts a shadow on the photodiode.

I moved the diode to the side and gave the plastic a little frost with fine grit sandpaper to scatter the light a little.

Next step is to calibrate these numbers to the PAR readings.

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