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Old 11-11-2010, 02:13 AM   #31
aaronbrown
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this might help you all out at least to make the sensor http://www.colorado.edu/eeb/facultys...e_Daniel03.pdf
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Old 11-11-2010, 02:42 AM   #32
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this might help you all out at least to make the sensor http://www.colorado.edu/eeb/facultys...e_Daniel03.pdf
Thank you! That is a very good report. It almost makes me want to justify buying a milivoltmeter.....but, not quite.
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Old 11-11-2010, 03:00 AM   #33
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well i thought this would help alot of ppl out and so i thought i would do a lil research to help further this along and if it can be built cheaper than buying one thats great cause we all know how expensive the world of fish keeping is wether it be freshwater or saltwater
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Old 11-11-2010, 03:40 PM   #34
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Hey, guys, I think I found a better photodiode.
http://www.alliedelec.com/search/pro...0079#tab=Specs
Cost: $3.19

It's basically, the photodiode I have but it has a IR filter in it and the resulting spectrals are:


But the problem is minimum order is 25... that's like $70+.....
hmmmm. Maybe I can look for a IR filter instead or just call up hamamatsu.
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Old 11-11-2010, 03:48 PM   #35
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mistergreen,
what data does the ardiuno gave you as an output and how do you translate that to PAR reading? I am new to electronics but would like to learn and prehaps provide some input to help out.
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Old 11-11-2010, 03:52 PM   #36
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the $3 photodiode data you provided does looks better and somewhat matches the $17 photodiode. good find.

I am very interested to find out how everything turns out. I have been reading this thread every day since it started. With Hoppy providing useful input, I have a strong feeling it will turn out good.
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Old 11-11-2010, 04:06 PM   #37
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this might help you all out at least to make the sensor http://www.colorado.edu/eeb/facultys...e_Daniel03.pdf
I looked around for the photodiode used here... I don't think they make it anymore or anything like it. The maker got bought up or something.
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Old 11-11-2010, 04:15 PM   #38
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mistergreen,
what data does the ardiuno gave you as an output and how do you translate that to PAR reading? I am new to electronics but would like to learn and prehaps provide some input to help out.
All photodiode will output a small voltage when excited by light but the voltage alone is not not good enough in terms of resolution.
So what you do is apply 5Volts through it and gather the output signal from the diode (0V-5V).
Here's a typical setup (photoresistor/photodiode)



Quote:
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the $3 photodiode data you provided does looks better and somewhat matches the $17 photodiode. good find.

I am very interested to find out how everything turns out. I have been reading this thread every day since it started. With Hoppy providing useful input, I have a strong feeling it will turn out good.
Yeah, I think it'll turn out well. I'll go ahead and get the hamamatsu diodes. I think I'll get 5 diodes for that $17. I can sell off the rest to you guys.
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Old 11-11-2010, 04:19 PM   #39
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ah... now I see how its done! thanks for the quick answer. I will follow closely on the developement of the DIY PAR meter.
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Old 11-11-2010, 05:55 PM   #40
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I called up Hamamatsu, wow what a hassle. I think they'll do a background check hah...

And I had to order at least $50 worth. I think I might wind up with 15 diodes so I'll have plenty to share.
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Old 11-12-2010, 01:49 PM   #41
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I called up Hamamatsu, wow what a hassle. I think they'll do a background check hah...

And I had to order at least $50 worth. I think I might wind up with 15 diodes so I'll have plenty to share.
hmm......... first they did a 'background check' on you and then asked you to make a minimum of $50 purchase? That is outrageous!
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Old 11-12-2010, 02:11 PM   #42
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HEh, They needed me to fill out a form on the intent of my purchase... I think it's regular policy these days to make a safer world.
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Old 11-12-2010, 02:15 PM   #43
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HEh, They needed me to fill out a form on the intent of my purchase... I think it's regular policy these days to make a safer world.
For photodiodes??... maybe its more of a marketing strategy to look into new avenues they can market their products.......... just my 2 cents. Anyways, how is the design and calibration coming along? Any new developements?
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Old 11-12-2010, 05:33 PM   #44
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Aha! A good photodiode and and some oxidized hydrogen, and you have the makings of a powerful thermonuclear device! (Let me double check my old college physics book to confirm that.)
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Old 11-12-2010, 06:55 PM   #45
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Hah, I have no idea what kind of weapons you can make but I know photodiodes are used regularly to detect lasers.. I have heard news stories of people buying cheap components from the States and shipping them to NATO embargoed countries which is a big no-no.

In my research, I found out that a green LED, can read PAR visible light pretty darn well. The spectrum matches up but the resolution is so low I'd need an expensive millivolt meter.


Well, the conclusion on this so far is that the current photodiode is not reliable because it reads Infra Red as well. Different bulbs will have different IR output and will skew the readings. Since a photodiode is the key foundation for this, I'll wait for the correct diode to arrive and restart the calibrations.

I can worry about the cosine corrections and such later. I wouldn't even know where to get a cosine correction filter ... But from looking at the charts & graphs, I can leave it out and call it 'goodnuff'.
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