# LED Comparison for Planted Bowls



## Robotguy (Jan 24, 2010)

Newman's Shrimp Bowl was so awesome, I had to give it a try, so I started digging through my small lights. I'm a big fan of LEDs and I'm a major pack rat, so I had a few laying around. The engineer in me decided to take some measurements to compare the different types I had.

Now, I don't have a PAR meter handy, but I do have access to a Tektronix J17 Photometer with a J1811 Cosine Corrected Illuminance head, so I took some readings in lux with various lamps 2", 4", 8" and 16" from the head and at 2"-10" side offset. Unfortunately, vBulletin doesn't support tables, so I made a spreadsheet (see bottom of post for a chart if you don't want to open the spreadsheet):

https://docs.google.com/spreadsheet/ccc?key=0AvbgU50_SSCadGJQc2s0TENyYXEzakxzbEktRDdlaXc&usp=sharing

These are the lights I measured:

Ikea Solar LED lamp (Full charge stock, and with 5V power supply, lens removed)



Ikea Clamp LED










Ikea Halogen Shelf Light (only one was on):



Target 4W LED Desk Lamp:



Standard 13W Spiral CFL in a task lamp:




For those who don't want to open the spreadsheet, here's the comparison at 8" from the light:











I'll try to test some actual aquarium lights (like my Odyssea 4x T5, or my Archea 14" LED) for comparison later this week.


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## Kai808 (Jul 19, 2011)

Cool! How long do those solar lights keep up those readings?


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## OrangeAugust (Jul 26, 2012)

I'm still trying to understand the whole lighting thing. So what is the vertical scale? 
So are the ones higher on the scale better for growing plants? Would that be considered high light? I have an LED desk lamp from target that is similar to the one in your test and I find that it seems to work well for my plants. I'm using two of them over a 10 gallon. But the second one I bought, the light isn't as white. I'm not sure why.


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## Robotguy (Jan 24, 2010)

Kai808 said:


> Cool! How long do those solar lights keep up those readings?


My plan is to use the solar battery pack and LEDs separately, but it looks like the pack uses 3x NiMH AA batteries in series, probably about 2000 mAH each, and the LED driver draws about 110 mA, so a rough guess would be somewhat less than 18 hours on a very full charge. I haven't measured the output of the solar panel so I couldn't say how long they take to charge. I just left mine sitting in the sun all day and crossed my fingers....




OrangeAugust said:


> So what is the vertical scale?


Lux, "a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface.....equal to one lumen per square metre."



OrangeAugust said:


> So are the ones higher on the scale better for growing plants?


The lamps with higher numbers put out more light. I didn't take into account color spectrum (I also have the colorimeter head, so I may play with that later). My guess is most of the LEDs will have approximately equivalent spectra so brighter=more growth. I couldn't really say how the LEDs would compare to the CFL and Halogen though.



OrangeAugust said:


> Would that be considered high light?


Good question. I'm not sure how to convert yet. I may try to get some PAR readings also to compare. Until then I found this (no idea how accurate it is):


medicineman said:


> Some simple data that I collected from a source:
> 
> 500 lux : Cryptocoryne nevii, wendtii, afinis, java moss
> 500-1000 lux : anubias nana, aponogeton madagascariensis, echinodorus sp, sagittaria sp
> ...





OrangeAugust said:


> But the second one I bought, the light isn't as white. I'm not sure why.


LED efficiency and color are notoriously dependent on manufacturing tolerances. More expensive brands/models (e.g. Cree) actually measure the output of each individual LED and separate them into "bins" so you can get the same output from a set of LEDs for a given input. This is very important in architectural lighting to keep a bunch of LEDs, all driven with a similar input, from looking wildly different.

I doubt Ikea uses expensive binned LEDs in these cheapo lights, so they will vary in color and intensity from one lamp to the next.

UPDATE:

Given Hoppy's 61:1 Lux to PAR conversion (plus X1.1 for water correction), here's the chart for PAR at 8":


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