Minimum size (diameter) of a high power flashlight (e.g. Cree T6, etc.)

simon hanson

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Hi

I appreciate your help soooo much!

I am about to built a flashlight with a diameter that must not be more than 17mm. I haven't found any hight power (>1000Lux) LED flashlight on the market as thin. Is there any problem in principle with thin high power flashlights?

I guess it's a question of the lenses... but I see no reason why.

Thank you so much!!!

Simon
 

AnAppleSnail

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Concentrated beams usually require a large optic to source size ratio. That is, for a given source size (1mm square power LED), you need an optic that is X times bigger to get Y lux. This is a rough rule. See if Peak advertises anything appropriate.
 

TEEJ

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Hi

I appreciate your help soooo much!

I am about to built a flashlight with a diameter that must not be more than 17mm. I haven't found any hight power (>1000Lux) LED flashlight on the market as thin. Is there any problem in principle with thin high power flashlights?

I guess it's a question of the lenses... but I see no reason why.

Thank you so much!!!

Simon

By "high power" do you just mean lumens, or, did you also want the beam to reach any particular maximum range? You refer to 1,000 lux, which would NOT be powerful as far as range, it would be weak.

I ask, because you say high power, but use lux in the spec, which refers to range not the lumens.


So, is there a minimum range you want the light to be able to illuminate for you?

How brightly lit do you want it at that point, bright enough to read from 6' away, just a candle worth, etc?
 
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simon hanson

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Thank you so much to both of you!

I have not been specific enough.

First: You are absolutley rigth, I mean Lumen (It was 3am when I wrote this;)

The intended purpose is a far reaching parallel beam. Since I will run it (due to the limitations that come with my 17,5mm aluminium pipe (inner diameter), I will probably stick to AA. (Or do you have any suggestions for a cheap rechargeable solution that would be a better alternative to the 18650/17670, etc.)

I am not yet into the elctronic / energy challenge, since I am still not feeling confident in finding a system of lenses that help me creating a parallel beam out of a e.g. Cree T6 or other high power LED (high lumen:) within this little pipe. I thought about fresnel lenses... I guess that could work.

I am sure if I am putting in a lot of effort, I will find a solution, I just wanted to know if anyone sees a difficulty withing my approach.

I guess the difficulty with the ratio of the LED and the lenses could be compensated by simply more lenses?

Has anyone of you ever seen an LED Flashlight using fresnel lenses (they would have the same optical effect as the big lenses commonly used, needing less space)

I hope I opened a discussion that is also of interest for others. I will post my results as soon as I succeed : )
 

gravelmonkey

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"Low" lumen numbers from 2*AA lights compared to those that take 1*18650 are usually due to the limited power 2*AA's can supply.

Running 2*14500's you could build something impressive like this. Getting the throw you want will be the real challenge.
 
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Fireclaw18

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Sounds like you want 1,000 lumens combined with a lot of throw in a 17mm package.

I don't think that can be done with currently available LEDs and optics. To get 1,000 lumens out of such a small light, you'd probably be using an XM-L2 U2 emitter powered by an IMR 14500 cell at maybe 4 amps. With decent optics or reflector this might give you 1,000 lumens out the front... but be advised that battery life will be VERY short... just 9 minutes on max power and the light will heat up incredibly fast.

XM-L and XM-L2 emitters use relatively large dies that have relatively low surface brightness. They don't throw well in small lights. for such a large emitter you really need a large reflector or lens if you want to get a lot of parallel throw. If you want a lot of throw in a small light you should use a smaller emitter with a higher surface brightness. That will get you more throw for seeing something in the distance, but you'll lose lumens. Instead of 1,000 lumens, you might only get 200.

Your best bet is probably to use an aspheric lens. I think going to a fresnel lens only saves you the thickness of the lens and won't really help in the width of the lens.

The longer the focal length on the aspheric lens, the smaller the image of the die will be and the more focused the beam will be. However, the LED emits its light in a wide arc. If you use a very small aspheric lens with long focal length, most of the light will be emitted into the sides of the bezel and be wasted instead of into the lens. You might get a nice small die image, but it will be dim. If you use a short focal length aspheric lens, then more light is captured by the lens and goes out the front... but the die image will be huge and may not project very far.
 

TEEJ

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1,000 lumens is a lot for that sized power source.

Typically, you are trying to see something with the light, and, there is certain amount of LUX required to illuminate the target adequately for your purpose.

You say you want a parallel beam, but that's a laser...and you can't SEE with a laser or get 1,000 lumens, etc.

A simple loupe type lens over any LED will focus the beam in the shape of the LED, with a very small beam angle (As close as you can get to "parallel").

Any aspheric lens (Makes it work like a projector lens) will do this, and they make those very small, mm range sizes if you need them.

If you don't KNOW the lux you need, at least describe what the light is FOR. IE: The same as might be needed for reading, examining small circuits, etc. (1,000 lumens is a LOT of light at close range when concentrated into a small spot...)




So, again, the question you need to answer is:

What sized spot of light do you need at what range, and, how many LUX do you need it to be illuminated at?
 
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