A Light Meter for Less Than $10

Pyrosteve · Jun 17, 2019

Any updates/tests? Just ordered one (went to my Lowes - out of stock).

Gino · Jun 21, 2019

Really great read up and DIY project to try. But my main concern besides water proofing it could be, how I get the approx measurements knowing that PUR is more important for us than PAR. Par as I understand it's intensity of visible light, that if it's to much it's detrimental for the corals something that corals don't really need it at all, basically for the visual and photo period exposure. How should I take this measure? Crank the blue's and Violet and measure and then add white, red and green colors just for visual aesthetic?

@Dana Riddle thank's for your contributions as always, your knowledge always is a go through guideline. And this experiment it's a buck saving for all of us that want to be able to get the best out of our lights.

@bigcheese that is a good idea for water proof, so far any thought about it or anything else that could be done to make it better? Thanks you also.

bigcheese · Jun 22, 2019

@Gino:

@bigcheese that is a good idea for water proof, so far any thought about it or anything else that could be done to make it better? Thanks you also.

I could get more practice with my spray can skills. That stuff doesn't come out like Rustoleum [emoji23] .

I hear ya on the PUR.
I think I mentioned before about using some color fiters on top of the PV cell itself to build an optical 'notch' filter and isolate those colors we care about, but it would have been both a PITA to use and a PITA for me to build tiny little square plastic sandwiches with my fat sausage fingers. In the end, it would have cost about the same as buying a quantum meter, so I got bored with that experiment.
I did find a $9 (cheap and pretty accurate) RGBW sensor chip used in a few scientific projects I want to try. Spectral response for each of the color sensors seems to be right in line with each peak for Chlorophyll a/b, Anthocyanins and Xanthophylls.

The key here is that it's a chip, not a turnkey device. Besides the chip itself, I'd be looking at building a waterproof housing (3d printed) and a module to power it, collect the data, do some math things, and output it in human-readable format. That's definitely going to cost more than $10, but hopefully way less than a Seneye, Li-Cor or Apogee. I'll call $75 a success.
We'll see after summer... work's got me absolutely crushed until then.

Gino · Jun 22, 2019

bigcheese said:
@Gino:

I could get more practice with my spray can skills. That stuff doesn't come out like Rustoleum [emoji23] .

I hear ya on the PUR.
I think I mentioned before about using some color fiters on top of the PV cell itself to build an optical 'notch' filter and isolate those colors we care about, but it would have been both a PITA to use and a PITA for me to build tiny little square plastic sandwiches with my fat sausage fingers. In the end, it would have cost about the same as buying a quantum meter, so I got bored with that experiment.
I did find a $9 (cheap and pretty accurate) RGBW sensor chip used in a few scientific projects I want to try. Spectral response for each of the color sensors seems to be right in line with each peak for Chlorophyll a/b, Anthocyanins and Xanthophylls.

The key here is that it's a chip, not a turnkey device. Besides the chip itself, I'd be looking at building a waterproof housing (3d printed) and a module to power it, collect the data, do some math things, and output it in human-readable format. That's definitely going to cost more than $10, but hopefully way less than a Seneye, Li-Cor or Apogee. I'll call $75 a success.
We'll see after summer... work's got me absolutely crushed until then.

Definitely that project will be a must follow tread. And by far a well spend $75 versus $250+ to just use it ones or twice every other year or so. If you manage to make it work.
Take care and KoR

JohnMzreef · Feb 11, 2020

Hi, could you provide the mathematical formula used to generate the depth coefficients? I skimmed the thread and didn't spot any other discussion of this..