# Light Design



## jazzy323f (Jan 22, 2015)

Hi All,

I'm trying to build a light source that has features that make it flexible so that I can use it in various scenarios




Vary Colour Temperature from 1,900K to 10,000K
Dim-able
Full Spectrum to provide high CRI for more natural lighting
High Efficiency
Colour spectrum control (i.e. multichannel)

My thinking is a 3 channel design with Blue, Cool White and Red LEDs. Any other suggestions?

White will give me the efficiency. Blue will bump up colour temperature. Red will get me low colour temperature.

Hi All,

I'm trying to build a light source that has features that make it flexible so that I can use it in various scenarios





Vary Colour Temperature from 1,900K to 10,000K
Dim-able
Full Spectrum to provide high CRI for more natural lighting
High Efficiency
Colour spectrum control (i.e. multichannel)


My thinking is a 3 channel design with Blue, Cool White and Red LEDs. Any other suggestions?

White will give me the efficiency. Blue will bump up colour temperature. Red will get me low colour temperature.


----------



## jazzy323f (Jan 23, 2015)

Lots of views but no thoughts? 

Am I in the wrong forum perhaps?


----------



## more_vampires (Jan 23, 2015)

I'm nowhere the RGB/RGBW expert that others here are.

http://www.candlepowerforums.com/vb...ose-sexy-quot-color-ring-quot-RGB-controllers

Perhaps your thread title isn't catching the eyes of the experts? Perhaps a thread title rename is in order? "Light Design for variable color temperature" Perhaps?


----------



## AnAppleSnail (Jan 23, 2015)

I can bump you in the right direction: Aquarium Sunrise/Sunset controller But you'll want different channels than Red, Blue, and white LEDs, and very good understanding of how to program the controller. Now, between the ranges of 3000K and 6000K it's very simple: Get 3 CCTs of white Hi-CRI LEDs on 3 channels - 3000K, 4000K, and 5000K. This will take some interesting topology - Nichia creates the only high-CRI 5000K CCT LED, so you'll need to carefully balance your relative outputs. With 3 channels you'll get a good blend in this medium range. Going higher than 6000K IS pretty simple - You'll want to add a channel of Royal Blue LEDs. Going lower is tricky - You'll want some real deep orange-red and deep reds. I don't know if you can cram them all on one channel. So you're looking for a 4+ channel controller and a high-power LED array. I hope you like floody output! Matching optics on so many LEDs will be nearly impossible - And if they aren't VERY close together you'll have problems with colorful shadows. The Aquarium Lighting guys know what they're doing, describe what they build, and often post videos to show what it looks like. Good luck!


----------



## jazzy323f (Jan 23, 2015)

more_vampires said:


> I'm nowhere the RGB/RGBW expert that others here are.
> 
> http://www.candlepowerforums.com/vb...ose-sexy-quot-color-ring-quot-RGB-controllers
> 
> Perhaps your thread title isn't catching the eyes of the experts? Perhaps a thread title rename is in order? "Light Design for variable color temperature" Perhaps?




Good suggestion I'll do just that!


----------



## Anders Hoveland (Jan 23, 2015)

jazzy323f said:


> Vary Colour Temperature from 1,900K to 10,000K, Full Spectrum to provide high CRI for more natural lighting


That is a difficult thing to design yourself, if you want really high CRI, to be able to vary the color temperature over such a wide range.


----------



## more_vampires (Jan 25, 2015)

I keep wondering what could be done with a 4-up star in a handheld.

Is this for fixed lighting or portable?


----------



## AnAppleSnail (Jan 25, 2015)

more_vampires said:


> I keep wondering what could be done with a 4-up star in a handheld.
> 
> Is this for fixed lighting or portable?



If I were made to do this with only 4 LEDs, I would choose a deep red, a warm-white, a cool-white, and royal-blue. The controller is key - You'd need exact control over each channel. A 1-button interface wouldn't do - Maybe a touchscreen?


----------



## more_vampires (Jan 25, 2015)

Agree, programming's the curse. It'll vary by build!!! No two builds will be alike.

Still, sounds really cool though! :twothumbs


----------



## jazzy323f (Feb 3, 2015)

Hi Guys,
Yes I agree that multiple channels with blue, white(s) and deep red sounds like the best approach with the technologies that we have.
In addition yes a touch screen is the plan with brightness and colour temperature on 2 different axis; need to make it user friendly 

Yes layout of those LEDs and optics is going to be key to get the colour mixing and beam pattern right. I just need an optics expert!


----------



## jazzy323f (Feb 3, 2015)

What's the best way to find the most efficient LED for a given colour? Is there a list out there or maybe someone/retailer that can help?


----------



## foxtrot824 (Feb 3, 2015)

jazzy323f said:


> What's the best way to find the most efficient LED for a given colour? Is there a list out there or maybe someone/retailer that can help?



That will just come down to LED research. While I like the track you are on I think it is worth mentioning that it is a very complicated challenge. Some companies offer a "dim to warm" solution such as Cree. There is a tremendous amount of work that goes into designing dimming curves especially when you are mixing in red for CRI. 

If you just stick to LEDs that come in the CRI you are looking for it will be more easy to mix the CCT you want and have it dim along the black body.


----------



## jazzy323f (Feb 4, 2015)

Having high CRI (90+) at full power with all channels on would be ideal. Having the right number and combination of LED colours will by key it seems.

The reduction in CRI as the colour temperature goes down is not too much of a concern.....1900k is sunset/candlelight after so the expectation will be that colours will appear different though I think white blended with red will give decent CRI.

Interestingly it appears that sunset has a CRI of about 60% but candlelight has 100%. Not sure how reliable the source is:

http://www.eaglelight.com/category/lighting_tutorials.color_rendering_index/


Excerpt below:

If you have ever watched a sunset you will notice how the colors change from a purer white to more yellow and red. This color change is typical of the changes in color temperature from higher numbers to lower numbers. If the reference light source used for CRI is at noon day sun a 100% CRI will result in a whiter light, if the reference source used is at sun set, at 100%CRI wil result in a light with more yellow and red. If you were to measure the light of sunset to a reference of noon day sun, the sunset light would only produce a CRI of 60% or less: less than 60% of the light spectrum of noon day light is present in the light of a sunset, hence the shift to more yellows and reds.



Candle 1700k - 100 CRI 
High Pressure Sodium 2100k - 25 CRI 
Incandescent 2700k - 100 CRI 
Tungsten Halogen 3200k - 95 CRI 
Cool White 4200k - 62 CRI 
Metal Halide 5500k - 60 CRI 
Natural Sunlight 5000-6000k - 100 CRI 
Daylight Bulb 6400k - 80 CRI


----------



## AnAppleSnail (Feb 4, 2015)

You're mixing up "Color Rendering Index" with accurate color rendering. The short version is:

Scientists and engineers describe things. While a spectral power distribution tells you everything you'd want to know about the mechanics of a light source, it doesn't tell you important things:






✓ Exact output at all wavelengths
x How done the steak is
x If the vegetables are OK in the fridge
x If the light is relaxing to read by
x If the light is good for color-exact work

So we have made a few ways to simmer down a Spectral Power Distribution to a smaller set of numbers. CRI is one - And it's not much good. "CRI" is exactly "How statistically close is that SPD to a black-body radiation SPD, at that color temperature?" A brick-red LED is a pretty good match to a CCT of 1000K - And terrible at really seeing color.

A candle's flame (High-temperature carbon particles) is nearly a black-body radiator - So it's got a high CRI and poor color rendering. To test this, look at navy pants under candle-light: They are black instead of blue! High CRI does not mean good color perception.

There are some psychology studies delving into exactly what an ideal light source is for seeing things. My experience is that getting a fistfull of LEDs, some at 4000K, some at 6000K, and selecting output of each channel to dial in a CCT somewhere between 4000 and 6000K, with a pretty good color rendering capability.

You'll want that test with the perception cards - In other words, do what looks right. How can we do this? That behavior is complicated to program, but in the end you'll be simulating the Spectral Power Distributions of your ideal light sources (Sunset, cloudy days) with discrete LEDs.


----------



## jazzy323f (Feb 5, 2015)

Excellent, Thank you AppleSnail that makes things clearer; CRI is not the same as colour rendition which I was not aware of.

Funny you mention sunset and cloudy days etc.; That is exactly what I'm trying to replicate in my light source. The change in natural SPD throughout the day drives the Circadian Rhythm in the body which leads to many health benefits as well as getting a light that looks 'right'. Win win!

So If I can replicate the following then I should be able to achieve what I want.








It seems with the current technology we have LEDs can most closely reflect these SPD profiles with highest efficiencies.

Had a play with an SPD calculator (http://www.1023world.net/diy/spectra/) and one possible configuration is 3 channels of lumileds with 1 white

4 x 5000k (CRI 85)
1 x Cyan (490nm - 510nm) [to cater for the dip at this wavelength]
1 x Red (620nm - 645nm) [to get low ~2000K CCT]

OR a 4 channel approach with 2 whites
3 x 5000k (CRI 85)
3 x 2700k (CRI 85)
1 x Cyan (490nm - 510nm) [to cater for the dip at this wavelength]
1 x Red (620nm - 645nm) [to get low ~2000K CCT]


Regarding the RGBA approach I feel the solution will become overly complex (and expensive!) once I've plugged all the dips in wavelengths to achieve a good level of color rendition and then efficiency goes out the door!


----------



## AnAppleSnail (Feb 5, 2015)

How much output are you planning on? If we figure about 60 lumens per watt, then it'd be easy to make a room very bright (10000 lumens = 170W), but above 200W you'll have extra planning.

And you don't have to take anybody's word for how "sun-like" a circadian manipulation system needs to be: I have experienced nice benefits from just having higher-CCT light in the morning. A lot of commercial systems are just high-intensity light.

One "simple" way to manage a 3-channel system would be to cut up an RGB LED strip controller. These typically handle 12V / 1A on 3 channels. The simple solution then is to replace the RGB LED strip with your 3 channels of power LEDs, set up for nearly 12v.




> 4 x 5000k (CRI 85)
> 1 x Cyan (490nm - 510nm) [to cater for the dip at this wavelength]
> 1 x Red (620nm - 645nm) [to get low ~2000K CCT]



This looks like some of the Coral Reef setups I've read about - Although they use a few dozen times as many Royal-Blues to get a high (10000K) CCT, and have these channels:

Deep red
Amber
Warm white
Cool White
Royal Blue
Violet (Sometimes)
UV (Sometimes)



If you don't like to cut and rewire an RGB controller, there are some other options:

LEDGroupBuy has some nice 'plug and play' light control setups. The MakersLED Driver and controllers are probably capable of what you want. The microcontroller to do this will take some fiddling - That'll run about $50 in LEDs and about $100 in controllers+power, plus whatever the microcontroller costs.


----------



## jazzy323f (Feb 5, 2015)

I think 100W which should be enough for a light source; It will be a table lamp in design. That will give approximately 6000 lumens which spread over 0.6m^2 will give 10,000 lux which is the 'required' level to relieve SAD but you're right in saying there are now studies that prove shorter wavelength light has higher efficacy.

That's an interesting solution regarding RGB strip. That is certainly a simpler and cheaper way. I'm thinking to go all out and have it MCU controlled for timed changes in CCT and intensity.

Regarding the number of Royal blues in those lights from what I gather it is to simulate light a depths of water where long wavelengths have already been filtered out.

I'm leaning towards 3 channels at the moment as I think it will be a good compromise between meeting the objectives and cost.

Are lumileds still the most efficient LEDs out there? How about CREE?


----------



## SemiMan (Feb 6, 2015)

jazzy323f said:


> I think 100W which should be enough for a light source; It will be a table lamp in design. That will give approximately 6000 lumens which spread over 0.6m^2 will give 10,000 lux which is the 'required' level to relieve SAD but you're right in saying there are now studies that prove shorter wavelength light has higher efficacy.
> 
> That's an interesting solution regarding RGB strip. That is certainly a simpler and cheaper way. I'm thinking to go all out and have it MCU controlled for timed changes in CCT and intensity.
> 
> ...




450-520nm is pretty much the only wavelengths that impact melatonin suppression and sticking in the 470-500nm has the best efficiency. 

Keep in mind this does nothing for Vitamin D production.


----------



## jazzy323f (Feb 6, 2015)

Agreed. Hence I want to include Cyan LED which I think is key as there seems to be a dip there in most white LEDs. There generally is a healthy spike around 450nm wavelength.

4 x 5000k (CRI 85)
1 x Cyan (490nm - 510nm) [to cater for the dip at this wavelength]
1 x Red (620nm - 645nm) [to get low ~2000K CCT]

I believe the Vitamin D production is down to UV. Unfortunately that's an area I don't want to get into at the moment as there's a lot of associated risks (cancer etc.).


----------



## more_vampires (Feb 6, 2015)

jazzy323f said:


> I believe the Vitamin D production is down to UV. Unfortunately that's an area I don't want to get into at the moment as there's a lot of associated risks (cancer etc.).



IIRC, 15 min of sunlight a day hitting as much of your skin as possible will do. For an easily-burned vampire (like me,) you can easily max Vitamin D on most mushrooms (grocery store.)

Sorry if this is slightly OT.


----------



## SemiMan (Feb 8, 2015)

Do mushrooms provide D2 or D3? You may be better off with cod-liver oil which provides D3.


----------



## more_vampires (Feb 8, 2015)

SemiMan said:


> Do mushrooms provide D2 or D3? You may be better off with cod-liver oil which provides D3.


I've got no definitive info offhand, but mushroom Vitamin D varies wildly. 3 iu - 973 iu, based on 84 grams.
http://mushroominfo.com/all-about-vitamin-d/ 

In my opinion, I feel mushrooms are superior to sunlight and artificial lighting. Plus, I love mushrooms. Cod liver oil, not so much. 

I just use light to see.


----------



## SemiMan (Feb 8, 2015)

Still off topic, but the right vitamin D is important, and sunlight may reduce carcinoma at the risk of melanoma. Try Carlson's cod liver oil. It does not taste bad.


----------

