DIY 100w LED 9000 LUX output

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starcentral

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Over in the Lighting section there is a nice thread on the Alzo 3000 which so far seems to output about f8 at 10 feet with 640 ISO. This is pretty good as a broad light source and once combined with a light modifier (softbox, etc..) seems to still have enough output power to render it "useful".

The completed units sells for $325 and up depending on where you buy it. ie. Alzo, Amazon, ebay,... and specs say they output about 9000 LUX @ 1 meter. Users have already confirmed the output is quite high, which is great. CRI to be unconfirmed but data sheets I have been reading show very low CRI's (around 70) for 5600k lights, but much higher CRI (around 90) for 2700k LEDs.

Considering the actual parts themselves are in-expensive it got me to thinking about a DIY project using these high power output LEDs, either in single or even QUAD configuration. Perhaps mounting one or two inside an old ARRISoft 1k metal chassis I had kicking around so I could have some easy 5600k soft light at my disposal.

100w LED's need anywhere between 20-30 volts and a constant current typically around 3.5 AMPS to operate. 100w LED's can be purchased from between $12-$60 depending on quality, and a dc-to-dc convertor with minimal electronic components added can be converted from a constant voltage power supply to a constant current supply needed to drive the LEDs. Used these dc-to-dc convertors can be purchased from between $12-$30.

Anyone play around with these on their own yet? Looks like something I might try.
 
Go for it! I'm very interested in this. It would also be fun to play with remote phosphor.

Probably the big trick is properly dissipating the heat. The Arri softbank may not be suitable for this, unless you cut out the bottom and fill it with fins.

Norman can probably tell us a lot about this.
 
i can give you a head start. I was tinkering with this about a year ago and just haven't had the chance to refine it. it does indeed work:

 
Thanks will watch that video shortly.

Check out this guy who built one to light his aquarium with! Anyway, electronics are pretty simple and not much really to it. I'd love a 4x4 foot bank of these..

 
Paul F said:
Probably the big trick is properly dissipating the heat.
Click to expand...

Would be good to have some numbers how much cooling or air flow they really need.
Noise beeing the biggest challenge, maybe it's possible to use CPU water coolers or even fanless coolers like
http://www.quietpcusa.com/Nofan-CR-80EH-IcePipe-Fanless-CPU-Cooler-P1009.aspx

How about Area 48, Cineroid lm400 or even 100W floodlights on ebay, they don't seem to use fans for cooling just heat dissipating design if I'm not mistaken?
 
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Spec sheet on the Epistar chip says 80C . That's ambient.

Reading a datasheet, lifetime is predicted duration when the intensity drops 30%. This is typically 20k hours at 100C junction temperature. Lifetime drops to 8600 hours at 125C and go up to 65khours at 70C.
 
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You can buy a 100w LED on ebay for $15 (no CRI listed). So who cares about perfect heat dissipation. Even if it runs hot, let's say you get 2000 hours out of it. That's a long time. Go replace it for $15. No big deal. Well, a bigger deal than replacing a tungsten bulb.
 
I've had pretty good results with making light fixtures out of the adhesive LED strips that you can cut and resolder to configure how you like and putting them in a housing. I'm still running some tests to see how accurate their color representation is, but for what I have invested in these lights, I'm not gonna go out of my skull if they have the typical cheap LEG green spike. I can either minus green them or just white balance to a grey card.
 
Ok, here's a stupid question:
Does adding a filter gel, say CTO, change CRI for better (or worse)?
 
stip said:
Ok, here's a stupid question:
Does adding a filter gel, say CTO, change CRI for better (or worse)?
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Not a stupid question at all. The answer is that it has no real effect on CRI.

CRI means how capable is the source of defining and outputting every frequency of the color spectrum. It is not a matter of how much it puts out of the color, just how much relative to the frequencies surrounding that color. Poor CRI means that there are big spikes and/or big gaps in the output of certain color frequencies. Most commonly these are in the green part of the spectrum, which is no big surprise since it is vastly the largest part of the visible spectrum. Many manufacturers attempt to correct these green spikes with magenta dyes (minus green). But a chemical dye, just like a sheet of gel, is a broad range tool covering a wide swath of color frequencies compared to the narrow bands of spikes and gaps they are intended to correct. The result of over-correcting these green spikescan be a magenta cast to the light.
 
I see that there are some who do not mind a little off color of leds with green spike's etc.
There are leds out there presently available that have the high CRI , but even though the number is in the 90's , a led that is rated at a much lower CRI may look more "accurate" or pleasing to some eyes and cameras.
I used many different led emitters from many makers such as Nichia, Cree, Philips, Osram, Bridgelux, etc. and I have encountered leds that have a CRI in the low 80's that I find much better, in my eyes, that some and many that are rated in the low 90's. What I am saying is that a high CRI number is not a real way to judge as it varies in color appearance from one led make to another even though they may have the same color temperature binning.
I have made many prototypes of some extreme examples of 500 to 1K equivalents and battery powered. I am talking about a true 8000 to 16,000 lumen units and not overrated specs. When it comes to leds, the lumens per watt at maximum rated output is what determines the fair brightness capability. Many leds are rated at a very attractive 150 lumens per watt but that figure is derived at 1 watt or less powering up the led. When that same led is powered up to it's max power level like 60 watts, then those lumen per watt figures sink like a rock on water. Low cost and low quality leds being not efficient will dissipate a lot of waste power to heat that must be managed by active fan cooling.Wheres a very high efficasity led will produce much more lumens at less waste heat therefore may not require active cooling at all for the same lumen equivalent. I made an extreme example of this of a prototyped 16,000 lumen led unit powered by 24 lighting class leds. The leds were run at half power to take advantage of the higher lm/w at that power level, that is why 24 were needed as opposed to 12 same leds at full power giving off much more heat overall for the same brightness level. Sometimes it gets to a fine line of deciding to use more or less leds in an enclosure. More compact = less leds = more heat = Fan.......Larger heat sink= more leds= less overall heat = no fan.
Calculations are made on theoretical formulas supplied by the led maker. Not really rocket science but there is always a tradeoff in performance vs heat. And heat is the enemy of the led.
 
I often use Cree leds as they offer a variety of the most recent and high performing on the market. They are very consistent and predictable results can be obtained by using the free PCT tool (Product Characterization Tool).
You just have to register it with your eMail, easy. That tool lists all the available Cree offerings and gives comparable charts as to voltage, amperage, lumens and the lumens par watt at any current input up to the max allowable.
A very good source for them is Cutter Electronics in Australis that often includes free shipping with orders of $149 or more. It usually takes 7-10 days to arrive. Another source is LedSupply that offers thermal adhesives ( 2 part) Arctic brand that is made specifically for high temperature led operation. Optics can also be obtained there too. Also becoming a free member of CPF (Candle Power Forums) offers a wealth of die hard led fanatics that have leds in ther veins.
Ask a question and you will almost get an instant answer, 24/7.
As to which chips provide the best results ?? That is not an easy one as it all depends what you are looking for. The Cree XM-L2 is tops as far as efficacity is concerned and also the MTG-2 that is insanely bright and van be powered by either 6-9 or 36 VDC. The PCT tool includes them. Cutter also has large Cree chips too. Not cheap but great if you need something superior. Cutter answers questions rapidly especially by Mr. Mark Riley who will answer any of your questions and keeps you up to date with any new leds that come out of the Cree factory.Cree is based in Durham N. Carolina. LedSupply ships very quickly. There are many other led sources but these 2 seem to have worked out extremely well for me over the years.
 
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