Huge reflector LED light

knegolf

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I just had a strange but quite interesting thought.

It is not uncommon to see people building insanely big HID searchlights on the HID forums, but what about LED lights? Has any one ever attempted to build such a contraption with an LED?
I am not just thinking of the one meter wide parabolic reflector type things, but even 30cm wide and deep reflectors.

A possibility that I just started thinking of five minutes ago is to build something like a bucket of light, which would consist of... You guessed it a bucket with a great big reflector. I am thinking specifically of an old zinc bucket with a reflector matched to the inner circumference of the bucket with a tiny LED mounted on an over-sized heatsink and driven as hard as possible. It would be a cool thing to put in your garden
Just don't take this too seriously as I don't have any concrete plans of building one for the lack of tooling experience.

Anyhow. Does anyone know of any crazy projects involving great big reflectors and LED light sources?
 

Mr. Tone

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I, too, would really like to see a manufacturer make a true spotlight sized LED light. Something with a reflector of at least 6" diameter. A massive heatsink and overdriven XM-L2 and MT-G2 would be nice to see. They should also de-dome the LED for maximum throw. For example, an overdriven MT-G2 is capable of more lumens than a 100 watt halogen lamp and there is certainly no shortage of large halogen spotlights. I guess manufacturers don't think there is a big enough market for the extra cost of R&D and manufacturing to make such a beast. Who knows, maybe we will get lucky someday and see a big single emitter LED spotlight.
 

knegolf

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Maybe the world isn't ready for such a thing yet.
But how about the modding community? Has any one ever attempted to build anything even close to what has been described in this thread so far?
Would a rearward facing LED be a good option for such a light? I have a faint memory of Pelican making a small torch with a reverse mounted LED to increase the focal length to be able to throw longer distances, but it is so faint that it might as well have been a revelation.
This might of course be totally wrong since I am still learning about reflections and refractions .
 

AnAppleSnail

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The filament of a 100W halogen is about the size of this o. The apparent source size of the XM-L is about the size of this O. The apparent source size of an MT-G2 is about four times that size (Half the diameter of a US dime).

As with all non-imaging optics, there are some relatively simple rules of thumb. One is that maximum throw in a given system is related to the ratio of SOURCE to OPTIC size. Whether the source is a pea-sized blob of plasma (Short-arc), glowing-white metal (Filament), or semiconductor, this rule holds true.

There are several factors in throw, but the main two are: Surface brightness and Source to Optic ratio. To really make a splash in the throw game, you've got to change one of these - dramatically.

De-doming an LED changes the apparent source size - This directly increases surface brightness (80% of the lumens on 50% the apparent area).

A big ********** reflector changes the source to optic ratio. This directly increases 'optical control' in Cree's words.

Where do you win this game with an LED? They all have about the same surface brightness, and the big ones tend to have it lower. The big LEDs also need BIIIIIG reflectors to maintain their size ratio.

There is a nice sweet spot with a 4" reflector and an XM-L2. That gives a very portable light with decent output and range. I have not yet tried to shim an LED into a (Big, expensive) custom reflector. Can you give it a shot and share results? Ma_Sha, Ra, and Saabluster do this kind of thing as a business. They have great reasons to avoid the big LEDs.

Pelican's Recoil LED line - I never got one to try it.
 

Mr. Tone

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The rear facing LED setup is called a recoil reflector. I really don't know much about that type of configuration. We have modders on CPF that have made lights with over 500,000 candlepower with less than 4" diameter reflectors. Those are made by de-doming the LED and overdriving them. I have a K50vn by CPF member vinhnguyen54 which produces over 1500 lumens OTF and between 550K and 600K candela. It is quite nice and impressive. However, I would love to see an even larger reflector so that we can get over 1,000,000 candela with a single LED. This has already been done with aspheric lenses but not a reflector yet, at least that I am aware of. Olight makes a spotlight type light that has multiple XM-L2 in it but they need to forget that and make one large single reflector. :naughty:
 

knegolf

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AnAppleSnail:
Thank you for your eloquent explanation. I remember reading something like this on one of saablusters old threads about the original DEFT, but you summed it up quite nicely for me. The point of my question was never to try and find something to beat the short arc or incandescent lights in any way. I was simply interested in the possibilities of combining a large reflector with an LED to see what would be possible to achieve. Or at least to hear what other more knowledgeable people have to say about the subject.

Mr.Tone: I have just read up on some of the Vinh lights, and they seem very impressive to say the least. As for Olight, I own an SR-90 which really blew me away when I first got to play around with it and I have been following their product line for some time now. It seems like they have been going a bit of track with their search and rescue series since the SR-95S-UT which in my opinion should have had a direct successor by now. I think you kind of lose a bit of the point with a searchlight if it has too much spill in the immediate area in front of you due to loss of night adapted eyes. I even found this to be a problem with the original SR-90. I found that I was able to see much further by standing about 30m or so to the side while having a friend operate the light, so these multi LED searchlights are definitely not for me.

I don't really have access to all too many of the tools required to make the "Light Bucket", but I might be willing to give it a shot provided that I can acquire a reflector suitable for the job without breaking the bank. It won't be a pretty sight, but it might be enough to collect some useful information. I can't promise you any results since I know myself a bit to well when it comes to these types of projects.
 

AnAppleSnail

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Thank you for the kind words. If you want to read about some DIY projects here for ideas, here are some great links. If not, get clever with duct tape and ring stands!

List of Projects by WalterK, a DIY throw guy

Over 1 million lux LED in 2010 by WalterK, also shows how X lumens at Y lux gives a very small spot. This design is interesting. It uses a precollimating lens to increase total brightness. With long-focal-length optics, it's a good trade. The pre-optic (Aspheric near the LED) increases the apparent source size, but increases the light reaching the large optic. Without the pre-optic there would be a slightly smaller 'spear' of light, but its total brightness would be less. With most optics, maximum lux is sacrificed for a bigger spot... But it seems to work well with really big optics.

On the cheap, you can probably 'bootstrap' an LED on a good heatsink into a really large reflector. You will wind up with a 'tower' module - Most large reflectors are meant to focus on a filament about 3cm above the bottom of the reflector. You can play around with a Mini Mag Lite LED (Reflector & head removed, in 'candle' mode) and a crapbox halogen reflector to try this out and see what you get. Have fun! Some neat things can be built.
 

knegolf

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Thanks again for your input.
The WalterK light is quite impressive, I can only imagine what it would do with a freshly manufactured top bin LED of todays standards. The other links might provide some good quality readin as well.
I have tried to experiment a bit with the reflector from my SR-90 coupled with my Lumapower Incendio in candle mode for some quite impressive hotspots, and the SR-90 reflector isn't all that big.
I have been trying to find some cheap source of reflectors that will ship to Sweden or even a cheaper searchlight to strip for parts, but have not yet managed to find one. I do have an old quite large HPS light with a spot reflector that might get tampered with tomorrow, It has about a 250mm smooth parabolic reflector with a medium focal length.
 
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