# 3D PAR/PUR-calculator



## defdac (Dec 28, 2003)

Hi folks, long time no see.

I'm making progress with my 3D light calculator. It will be a Java-based calculator that can be launched from a browser.

The current state is that the really complex and difficult math is done. It's a complete physically based renderer that uses something called "Stochastic Progressive Photon Mapping" which is a new cool and unbiased way of calculating spectrally based and physically correct global illumination.

It shoots photons from the light sources and let them bounce around in the scene until it hits a diffuse material (the walls in my picture) and deposits them. With the help of these photons the light intensity is calculated in each pixel of the picture and continues until you're satisfied with the visual result.

The GUI is not finished yet, but you will be able to specify tank size, number of bulbs and also draw you own reflector profile and select what material it should be made of etc. The reflector profiles is currently saved in Google AppEngine, and the spectral/bulb data will be taken from my database of my PUR-calculator http://www.defblog.se/LightCalculator/

Now that the pure visual/spectral-code is in place I used it to render a tank with different water depths. I have noticed that the intensity at the bottom of a tank is getting higher with the depth of the water column, measured with an Apogee PAR-meter. See pictures below. You can clearly see that much more light is esacping onto the back wall with shallower depths.

Next thing in the pipeline will be creating a virtual light probe that will count photons and see if I can correlate the readings of my PAR-meter with the output of this probe.

In the end I hope it will be a nice tool to decide bulb and reflector setup of a new tank. I also hope it will shed some light on how the intensity attenuates with depth etc.


----------



## RickRS (Dec 31, 2010)

I like what you're doing here.

Trying out the calculator, the results show as a narrow bar that I have to scroll up and down to see the units and the results. Can't see the two (units/column heading and results) together. But, as you stated, not finished yet. I'm looking forward to the complete version.


----------



## HD Blazingwolf (May 12, 2011)

That is a lot of work! As someone who took a beginner class in programming I have a slight knowledge of the task you are undertaking. This will definitely be a nice tool when done! I havea massive amount of respect for you!


----------



## plantbrain (Dec 15, 2003)

defdac said:


> Hi folks, long time no see.
> 
> I'm making progress with my 3D light calculator. It will be a Java-based calculator that can be launched from a browser.
> 
> ...


This looks good, has the LED's, has the marine environment and is still fairly simple for the user to do.

A different set of equations will be needed for the LEd vs the linear tube FL's bulbs, but this can be accomplished without too much work and verified using the PAR meter.

The "new bulb" additions is useful for calculator updating for the new brands and lighting types as they come out.

This is by far the most effective calculator I've seen to date.


Good work.


----------



## plantbrain (Dec 15, 2003)

I ran a GE bulb on a ADA 120cm tank with 2x54 watt and it was 105 micromol with the Apogee. I am not sure of the spacing with the bulbs or the evenness of the spread of light.

Is there anyway to give a bottom area picture of the intensity spread? 
Like if it was a HQI light source, then it's be a bit like a target with the higher PAR in the central region and bands of progressively lower PAR emanating outward.

This would require adding a function for the bulb distance spacing.
Same deal for point source like LED's. I'm not sure how well this can be applied for all cases, but simply getting most folks' spacings etc...should be enough to make this model work well.

More work for you though.

PUR..........this really is done *at the plant (or alga) species level*.
Each plant species has a *different* PUR and light use ability. I'm not aware of any published PUR data for submersed aquatic macrophytes. There are a few discussing it and acclimation to different wavelengths with marine seagrasses.

http://scholar.google.com/scholar?s...ytes&hl=en&as_sdt=0,5&as_ylo=2000&as_yhi=2010

Cumming's paper 2003 and Troels from Tropica are on this list.

http://www.bio-web.dk/ole_pedersen/pdf/Hydrobiologia_2202_477_163.pdf


Where does the PUR data come from?


----------



## defdac (Dec 28, 2003)

> I ran a GE bulb on a ADA 120cm tank with 2x54 watt and it was 105 micromol with the Apogee. I am not sure of the spacing with the bulbs or the evenness of the spread of light.
> 
> Is there anyway to give a bottom area picture of the intensity spread?
> Like if it was a HQI light source, then it's be a bit like a target with the higher PAR in the central region and bands of progressively lower PAR emanating outward.


Yes. The old calculator you are testing out will be phased out or mostly/only be used to add new bulb data.

The next calculator will render the result as seen in the three pictures above. This way reflector efficiency will not be a parameter, but a result of simulating the complete light equation in three dimensions.

With a reflector profile editor + placing, bulb selection + placing and tank size I will then calculate how much light is reaching a 1x1 dm rectangluar "probe" that you can place anywhere inside or outside the tank.

If you are asking for a better measure in 2D, like a heat map with colors depicting PAR at different regions on the bottom I guess that would be relatively easy to calculate. For example bright red = 100 PAR all the way down to dark blue = 0 PAR?



> PUR..........this really is done at the plant (or alga) species level.
> Each plant species has a different PUR and light use ability. I'm not aware of any published PUR data for submersed aquatic macrophytes. There are a few discussing it and acclimation to different wavelengths with marine seagrasses.
> 
> http://scholar.google.com/scholar?st...00&as_yhi=2010
> ...


You can select or upload action spectra for the species you have data for. The general one I use is measured from Elodea.

And I agree it can be quite misleading for many species so I have digressed and mostly talk about PAR nowadays. It's fairly easy to calculate PUR if you have the action spectrum so I keep it for those that really want to optimize for a plant they have action spectrum for. I don't take the values dead serious either, and mostly see a bulb with high PUR as a bulb with relatively much blue+red compared to green - which is not all that bad.

Another aspect of this is that it is very easy to see that green light doesn't grow plants as good as blue/red lamps - despite they have the same PAR, and most action spectrum have a big dip in green. If this dip is slightly different for different species it's still less efficient to feed these species green light in favour for blue or red.

It's not good, but it ain't that bad either..


----------



## defdac (Dec 28, 2003)

> There are a few discussing it and acclimation to different wavelengths with marine seagrasses.


That is interesting and makes a point that no species will have one "definite" action spectrum. They can acclimatize to more "exotic blends" of light, perhaps with more yellow and green.

Does this acclimatization cost energy/time? *shrug* Can they acclimatize themeselves for blue and green light optimized for Elodea? *shrug* Is chlorphyll green? Yes. Does plants grown under artifical green light grow slower than those under blue/red? Yes.

The one seriously bad thing with PUR is that it is sometimes counter intuitive when you have bought into all this blue+red stuff. For example like the seriosly high PUR of the very yellow light Philips 840. It has alot of green, but the kicker is that it also has alot of blue+red. This is confusing because you can't just look at a spectral distribution of a bulb and directly say if it will be slightly better/worse than any other bulb. Or even worse use the Kelvin measure which is the most useless piece of light information there is due to metamerism. Hence my calculator.


----------



## defdac (Dec 28, 2003)

Some results. I have made a white hood with white diffuse paint with 90% reflectance and a light probe counting photons and a Lux-value. The lamp is of the same dimensions as a HO T5 24 watt lamp with 1750 lumen.

The Lux I'm getting in the middle of the tank, apx 1 cm above the bottom of the tank with the tank full of water is 6400 Lux.









http://www.flickr.com/photos/defdac/5725649433/

A couple of years ago I measured a similar setup with a bit smaller tank with a really cheap Lux-meter beneath a clean tank almost full of water and got an average of 6050 Lux. 

I'm happy I'm getting in the right ballpark and I was prepared for a higher value in my virtual tank since it's completely ideal and mathematically correct, whereas the measured tank was not 100% filled with water, the hood was styrefoam-pieces and the probe was beneath the tank - not inside.

I think I have reached some kind of proof of concept here. Time to make the thing useful for others..


----------



## beviking (Aug 2, 2005)

Wow defdac! I have to agree with Mr. Barr that this is THE most effective calculator to date! Kudos to you! You should get some kind of golden plant award!roud:

Bill


----------



## Shad0w (Sep 26, 2007)

Thanks for the Calculator roud:

I try the calculator for CREE XR-E, CREE XR-5 Q5 cool white 3.7V 1A giving me 38 umol/s/m2 and CREE XR-5 Q5 cool white 3.3V 350mA giving me 55 umol/s/m2.

How come lower current give better PAR? is that expected?


----------



## defdac (Dec 28, 2003)

Yes I think that is in order. It depends how hard you drive the LED:s and their efficiency. If you drive the LEDs really hard to maximize the intensity from each LED you will get terrible efficiency.


----------



## Shad0w (Sep 26, 2007)

OK thanks for confirming. I thought it was a bug. That mean for LED I need to play around the drive current to get maximum PAR. That would be tough without PAR meter.


----------



## defdac (Dec 28, 2003)

Yes, exactly. But you don't need a PAR-meter for that. If it is the PAR you want to maximize then just go with the maximum drive current. 

This is not efficient though if you look at the problem from a more environmental friendly view.

The data sheets for Cree is very good with easy to read diagram where the sweetspot efficiency vs intensity is easy to see - or even spelled out directly. This will not maximize your PAR though, only the PAR-efficiency: PAR/watt.


----------



## tentacles (Nov 28, 2011)

So then how is the calculated PAR related to watts (input)? Obviously the LED driven at 1A (~3W) is going to have more light and PAR output than the one at 350mA, but in the calculator it reports a lower PAR value.. I think this is what he was trying to figure out? 

Is the reported PAR a PAR/W calculation or something? 

One more thing, do you know of a way to get a spectrum readout for a light, is there some sensor or device that is economically owned? I'd really like to play around with this, as LEDs color shift when you pump more power into them, there's a rather dramatic shift from 350ma to 1A current, and also a shift due to temperature.

By the way, the calculator and this 3d program are incredible!


----------



## Shad0w (Sep 26, 2007)

yes, that what I'm trying to say. Same LED driven with higher current but the PAR and Lux value is lower. I attached 2 picture below 350mA and 1000mA, hopefully make thing easier. Look like it is a typo on the lamp selection drop down menu.


----------



## defdac (Dec 28, 2003)

Ok. I understand the confusion.

It's the same as when comparing the miles per gallon between a BMW M3 and a Toyota Prius running the same (high) speed around a track. To keep the speed with the Prius you need to "put the pedal to the metal" and force the engine of thatcar to work in RPM:s it's not designed for and thusly get's less mpg than the BMW M3 that more or less "cruise" around the track.

The LED with less PAR is the Prius. I've added it in a state where it is driven higher than the other (1 amp instead of 0,350 amp). Then you get less light per watt. It's efficiency is terrible when driven hard. It might shine really bright when you do so, but it would be much more efficient to use some more LED:s "at cruising speed" to get the same amount of light...


----------



## defdac (Dec 28, 2003)

> Is the reported PAR a PAR/W calculation or something?


It the total PAR on the bottom of the tank for the selected amount of wattage/size of aquarium/reflector efficiency etc. 

That means that you can either reach the wanted wattage by using less but overdriven LED:s (less PAR) or using more of them in a more economical outputstate (more PAR since you get better PAR per watt).


----------



## WingoAgency (Jan 10, 2006)

Very interesting and hard work there. What would it take to include more brands of LED, do you need a physical diode(if so how many) or just spec sheets is enough?

For LED, would you consider adding the parameter of lens angles and even spacing between diodes?

Question:
1)what would we use for the reflective index assuming the LEDs are mounted on a flat heat sink plate?


----------



## defdac (Dec 28, 2003)

> do you need a physical diode(if so how many) or just spec sheets is enough?


The specsheets is all I use. LED:s are a bit tiresome to add since it involves alot of reading and decide what current is interesting for hobbyists. Some like to invest less in diodes and overdrive the LEDs and consume more watt to reach the PAR they want.

(I think RGB-setups are the most interesting since you can use alot of cheap LED:s and not overdrive them - and trim in the color exactly as you like. Requires lots of tinkering though..)



> For LED, would you consider adding the parameter of lens angles and even spacing between diodes?


For the 3D-version absolutely. I will probably simulate them with a simple directed point/spotlight where the angle is a natural parameter to the spot. You can place them however you want.

A 1,5 year old daughter is slowing the work down a bit though =)



> 1)what would we use for the reflective index assuming the LEDs are mounted on a flat heat sink plate?


Very tough question. I would actually consider 100-90% reflector efficiency for LED:s since almost all output from them will be directed downwards. The geometry approximation I use in the simple calculator discussed here is somewhat crude.


----------



## defdac (Dec 28, 2003)

*3D light calculator is finished after 3 years in development*

It's finished, albeit only a couple of lamps added and one reflector:
http://lightcalculator-hrd.appspot.com/

More lamps will be added by users and me. I will transfer some of the lamps from the old calculator to this one.

Feedback/bugreports/feature requests much appreciated.


----------



## ybendek (Oct 30, 2013)

defdac said:


> It's finished, albeit only a couple of lamps added and one reflector:
> http://lightcalculator-hrd.appspot.com/
> 
> More lamps will be added by users and me. I will transfer some of the lamps from the old calculator to this one.
> ...


Hi Awesome job...I'm very interested to try this app but ... when I'm trying to execute its requesting a user and password O_O what data is supposed to use??


----------

