# A couple of interesting LED PAR comparisons to whet your appetite.



## plantbrain (Dec 15, 2003)

You need different distances, one static light PAR reading at 440mm is not much use. Also, there's no parameter for evenness of the light spread around this region, again, a rather important thing since we are not spot lighting plants, rather, we seek a uniform spread over an area, say 18"x 48".

You need the make a light curve for each and associate this with an area of coverage. The sun is pretty even and distance from it makes less difference at the scale we use, but not with artificial lighting.

No sense it doing a lot of work then not have nearly as much use once you are done:icon_idea

Think 3D in other words.

The Apogee is not much different from the LiCOR FYI..........


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## redfishsc (Aug 29, 2010)

Tom, this was just play time, to show him how to set up the drivers as I have them, and to compare those three whites just for fun. Since all three of the LEDs we checked have nearly the same beam angle, the data is fairly useful-- at least we know that an XML cool white is twice as useful as a Satistronics "pure white" at the same drive current, and the XML is using less total wattage. The neutral white XPG sits somewhere in between them. It does not tell us how many of them we need, nor does it tell us what drive current we need. 

I understand what you're talking about, but measuring light spread and such isn't what we are specifically shooting for. These LEDs have a manufactured light angle of about 90-120 degrees, so many of us with tanks over 20" deep will end up using optics anyhow, which will totally nullify light spread data. 

There are too many variables involved with LEDs for us (at the moment) to test all these possibilities. 

Besides that, PAR data from a single LED is basically only useful for comparison of one LED to another at the same/similar wattage consumption-- essentially to see which LEDs are giving us the most use/efficiency. 

Hoppy might be able to calculate PAR numbers of a collection of LEDs based off of the numbers of one LED, and if so, fantastic. 
The two things we are testing for:

1) Spectral graphs from the radiometer, of single and combinations of LEDs. Admittedly this is of more use to reef keepers than us since plants seem much less picky about spectrum.

2) PAR numbers taken at constant distances and constant drive currents simply for comparison of one LED to the next, which admittedly has limited uses. 


Joe, in particular, is most interested in the spectral output as seen by the radiometer. That's what he was most interested in and I'm basically just enabling him to do it by supplying the LEDs and driver setup.

Checking PAR vs. light spread is something Joe may decide to do but he has a reasonable stack of work ahead of him already with the two items listed above. 

If you have any suggestions on this I'll forward the info to him or you can email Joe at [email protected]. Your input/suggestions would be welcome.


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## plantbrain (Dec 15, 2003)

The radiometer will be good info.

You might just chose a couple fo standard areas and depths.

Say 12"x 24", 18"x48", 24" x 72"
Say 10cm, 25 cm and 60cm
That's only 9 variables.
Even a little can be much more use than none.


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## redfishsc (Aug 29, 2010)

Just for perspective, here's what we are testing. 

These are the single LEDs. Joe will be testing them individually, and then making 2-5 LED combinations under the radiometer to see what the resultant spectrum is. 


Cree XPG cool white
----------neutral white
----------warm white
Cree XPE royal blue
---------blue (470nm)
----------red
----------neutral white
Rebel cyan
Bridgelux 402 cool white (10w) 
Satistronics 3w "pure white"
------------3w red
Satistronics 10w "pure white"
-------------10w 455nm blue
-------------20 watt 15,000K white


Plus, these two Rebel 3-up PCBs supplied by Dave Fason (who also supplied our buckpuck).
Neutral white, royal blue, royal blue.
Neutral white, royal blue, cyan.



Some of them, like the XPE red, are really of limited use for us. Just a single one of them is overwhelming at 700mA. But I have them, so we'll test them lol.


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## [email protected] (Jul 17, 2008)

Thank you redfishsc and your buddy Joe. 

For me, the single most valuable bit from the counter top measurement is documentation that $2.00 Staistronic LEDs are essentially half the value of Cree XMLs. That was not a known number. For those of us on budgets, who are trying to experiment, if Cree's are $4.00 they are worth the money. At $7.00, perhaps not.


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## shawnhu (Jan 23, 2009)

[email protected] said:


> Thank you redfishsc and your buddy Joe.
> 
> For me, the single most valuable bit from the counter top measurement is documentation that $2.00 Staistronic LEDs are essentially half the value of Cree XMLs. That was not a known number. For those of us on budgets, who are trying to experiment, if Cree's are $4.00 they are worth the money. At $7.00, perhaps not.


Even at $7, CREE XPG's are worth the $. The energy consulmption vs light output alone is worth the extra price tag.


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## redfishsc (Aug 29, 2010)

Don't put an enormous amount of stock in the countertop measurements quite yet--- but it certainly does look compelling. I think it is definitely indicative of the output of the LEDs. 

One thing to consider, both of the Crees have a beam angle of 120 degrees, the Satistronics LED supposedly has a 140 degree beam, which means it will show a lower PAR number anyhow even though it might be putting out more light that our single PAR reading can tell (ie, a larger footprint).


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## epicfish (Sep 11, 2006)

[email protected] said:


> Thank you redfishsc and your buddy Joe.
> 
> For me, the single most valuable bit from the counter top measurement is documentation that $2.00 Staistronic LEDs are essentially half the value of Cree XMLs. That was not a known number. For those of us on budgets, who are trying to experiment, if Cree's are $4.00 they are worth the money. At $7.00, perhaps not.


Unfortunately, without further PAR data readings with optics, these figures will give you only a ballpark idea of light output. 40*, 60*, 70*, 80*, and 90* optics will *significantly* change the spread as well as the amount of light directed into the tank.


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## Hoppy (Dec 24, 2005)

For many of us LEDs pose an economic problem as well as a light problem. When you DIY a LED light once you add optics you greatly increase the cost of the light. So, knowing what a LED will do without optics is an important consideration. (All LEDs have a lens, used to protect the junction, so they all have "optics" to that extent.)

Two approaches to a LED light are:
Minimum cost to get the lighting we want.
Maximum capability, including dimming, programing, color adjustment and mixing, etc.

For those of us short on $$$, the first approach is the key. In fact one of the primary reasons for DIY is economics. For others, there will soon be commercially available lights loaded with all of the bells and whistles, and for those who just enjoy the challenge, I agree that a lot more data, with different optics, will be valuable.


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## redfishsc (Aug 29, 2010)

epicfish said:


> Unfortunately, without further PAR data readings with optics, these figures will give you only a ballpark idea of light output. 40*, 60*, 70*, 80*, and 90* optics will *significantly* change the spread as well as the amount of light directed into the tank.



Hopefully once I get my own personal array done, I will get real world PAR numbers of them over my tank. 

Part of the reason we're not taking much PAR data using optics (except on a couple LEDs) is because they are such a pain in the butt for XPG's (just do an array with XPE/XPG optics and you'll cuss like a sailor) and there are so many combinations/iterations/variations. 


The data we are shooting to get right now is what I consider to be the most important data---- finding the resultant spectral analysis of various LED combinations (especially for reef keepers) and then, number two, comparing which LEDs (bare) will give better PAR numbers at the same drive current. 


All things kept as equal as possible, knowing which LED's produce better PAR as bare LED will give you a significant clue as to which LED will give you the most efficiency in your situation. 


As for choosing LED optics and knowing PAR info from that, we can gain significant real-world data from measuring LED arrays in action over actual tanks. 






Hoppy said:


> For many of us LEDs pose an economic problem as well as a light problem. When you DIY a LED light once you add optics you greatly increase the cost of the light. So, knowing what a LED will do without optics is an important consideration. (All LEDs have a lens, used to protect the junction, so they all have "optics" to that extent.)
> 
> Two approaches to a LED light are:
> Minimum cost to get the lighting we want.
> ...



Excellent points. For most of us that have tanks shallower than 18", non-optic LEDs will be fine and cheaper. 


I think another good comparison would be comparing the PAR values, and PAR distribution, of several LED setups against a T5HO and halide. But--- using a Killawatt or similar device to measure actual, at-the-wall watt usage.

That's beyond the scope of what we're doing at the moment though.


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## [email protected] (Jul 17, 2008)

shawnhu said:


> Even at $7, CREE XPG's are worth the $. The energy consulmption vs light output alone is worth the extra price tag.


For some, or for a finished product. 
I'm on a budget and pushed it to get 30 $2.00 LEDs to experiment with. Buying 30 $7.00 LEDs would have made this a "maybe someday" experiment.


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## Hoppy (Dec 24, 2005)

[email protected] said:


> For some, or for a finished product.
> I'm on a budget and pushed it to get 30 $2.00 LEDs to experiment with. Buying 30 $7.00 LEDs would have made this a "maybe someday" experiment.


That was my situation too, only it would have been a "probably never" experiment with $7 LEDs.


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## redfishsc (Aug 29, 2010)

It's possible to get the same PAR numbers and overall net effect by using half the number of Cree XML vs. the ebay/Satistronics LEDs....... if indeed we find a consistent pattern that the Cree XML gives twice the PAR at same drive current at PAR production.......over the same footprint. 

In other words, it might cost $7 per XML, but you'd need half as many, use less electricity (they have a lower voltage at the same current), and possibly even need half the number of drivers. If being able to skip an entire driver is possible, you just saved $30-50 based on the cost of many drivers out there.

It would simply be a matter of spacing the XML a bit tighter together and then raising the light up another couple inches for best light spread and even-lighting.


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## redfishsc (Aug 29, 2010)

By the way, if anyone has any unusual LEDS, or even a whole LED rig, you want tested, PM me and I can give you the address to ship it to. This is only practicable with smaller arrays (under 8-10 LEDs) but we can definitely do it. We'd need the driver and all, and need your trust that we won't swipe your array lol.

They would be packed and returned upon testing completion, we'll pay the shipping back to you.


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## IWANNAGOFAST (Jan 14, 2008)

I just picked up some optics to try out on my fixture, 60 degree ones, will test the PAR once these are on.


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