[DIY PROJECT][Update: 8xCREE XM-L U3 instead] Focusing a 100W LED for a future flashlight/car powered projector/car high beam

Flashlight Modding and DIY Parts
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Hi Guys,

After playing with some flashlights that I tested here I started getting more and more into “from scratch” DIY. Recently I’ve been heating up my 50 and 100W LEDs. As it says in the description, I plan on using them wherever I can, but the big goal is to fit them into my car’s headlight(we’ll discuss morality later if the project will go that way 0:) ).

This being said, here’s a first test of running the LED (temporarily placed on a big radiator) at 12V, via a $5 Buck Converter from Ebay. It can just run the LED at ~110-120W before shutting down, although it gets quite hot. A 50mm fan on it and it will be ok. :slight_smile:

I do have another buck converter available that I payed $10 for and I used that to rush 150W into a 50W LED. It didn’t even warm up… So I’ll see what I’m going to use.

As you can probably see in the video, the light output is… tremendous. At 110W this “puppy” gets out ~10.000 lumens. Although I can light up a huge area, the distance it can cover isn’t that big. Actually, measured with my luxmeter, at 1m (3ft) the output is ~4kcd (4000lux). That’s because I only used the 44mm lens in the video above, that gets about a 90degree angle. Not what you’d call “focused”.

So my goal right now is to focus that huge area chip into a smaller spot. And I managed to do that with an extra $6:

I got a A5 (12x18cm) sized fresnel lens from UK to put it to some tests. The test is a HUGE success as you can probably see in the video. Let’s talk numbers.

From 4kcd with only the 44mm lens on the LED I got 66kcd by handhelding the lens in front of the LED. 16 times brighter, not bad, huh? 8)
That spot got to about 40cm diameter at 2.4 meters away!

And another outside video. Not very conclusive, but that’s all I can provide right now.

By only handhelding the lens at 20cm away from the lens(focal point for a 12x18, 3x magnification Fresnel) I guess I was losing quite a lot of spill. So surely, by making a reflector I could get a brighter spot, no? YES!!

After making this HIDEOUS looking think (strong, white inside cardboard, testing only) I tried getting more readings. I honestly hoped to see an increase to about 80kcd (80.000lux) with it. And excuse the mess, it’s always like that when “i get going”. :8)

A few readings later… 80-100kcd! It varied because my hand wasn’t steady above it. I used a tape ruler to go 1m away from the led and scouted for the brightest spot, that got a reading of about 1050 (x100) on my luxmeter.

100kcd with that huge spot! What if I cover the inside with neatly glued aluminum foil? :open_mouth:

Now, the biggest problem for a car’s high beam is that I don’t have 20cm worth of space to focus the light. More about 10cm. So I must make more adjustments to the optical system.

I ordered another, thicker 44mm aspheric that claims it can throw the light in a 60degree angle, and two 78mm lenses with reflectors and brackets. I honestly think that by using the 44mm 60degree lens I can focus it better in the shorter distance, but we’ll see.

The following days I hope to get some time and some help from my friends and go test it outside (along with my NASA looking reflector :D), the same place I went to test the lights in my previous thread.

I’ll keep you posted. Any feedback and suggestions on how to focus that big boy in less space will be greatly welcomed.

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You made me smile thinking about how popular you would be in you suburb and surrounding suburbs. Thanks for sharing the unique lights you are building.

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That’s more like it. :laughing: Popularity doesn’t come by blinding people… unless there was a BLF meeting somewhere. :bigsmile:

In the first clip, my friend was saying just at the end: “Now all those people will wake up and start dressing for work because they’ll think it’s 5AM in the morning”.

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Hi Boggy. Nice work. This aspheric lens might be interesting to you, but it has an even longer focal length. I'm estimating around 12 mm. It delivered 400 kcd just holding it up by hand in front of a dedomed MT-G2 by hand. Emitter was driven at about 6 amps. I'm not sure how that would translate to your large emitters though.

I've been playing with a similar idea to yours. I want to try to have a shutter to provide cut off for low beams. The shutter would be reflective and shaped on the back side to reflect the unused portion of the beam back to the emitter. Before anyone jumps on me about legality, My intended use is off road.

You have a product link for the big lens you are using above?

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Thanks for your suggestions ImA4Wheelr, great build you have there! I read your thread when searching for 100mm lenses and it came on Google.
Your numbers are insane, 4-8x the brightness of my 100W Led + Lens(albeit with a smaller spot, but that means a hell of a thrower). Can you estimate how many lumens your LED gets at 7A?

Regarding that lens, I really don’t know how it will perform with my huge area LED. I’m guessing you meant 120mm focal length(12cm, ~5inches)? At that distance I would be losing a ton of spill from my 90 degree lens that’s on the LED. I think that’s the biggest problem right now for my build.
I’m waiting for my 60 degree, thicker lens and my 78mm lenses to see how I can combine them. I also ordered 5 new 60x60mm fresnel lenses, maybe I can use those in between the led and the bigger lens.

Here’s the A5 fresnel, I like how it’s made.

My plan is to do something simillar to what these guys did here(skip to 2:25):

The difference would be the optical focusing system and the fact that I will be using 100W LEDs.

P.S. Without a second focusing lens, a car’s halogen bulb will outperform the LED’s throw by a long shot. That’s why I need to get that light neatly in a line.

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Question…could you use a cylinder of that clear acrylic encapslant with a aspheric rounded front end?

Yeah…I was thinking freshnel lens though

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Boggy wrote:

Can you estimate how many lumens your LED gets at 7A? Regarding that lens, I really don’t know how it will perform with my huge area LED.

I’m guessing you meant 120mm focal length(12cm, ~5inches)? At that distance I would be losing a ton of spill from my 90 degree lens that’s on the LED. I think that’s the biggest problem right now for my build.

I should have said 6 to 7 amps. I think I measured 6+ amps with stock DMM leads. So actual current to the emitter could have been 7 amps for all I know. Sorry for not being more specific in my post. I was running DD with 2S average laptop 18650's. So current would have been what ever they could deliver. Definitely wouldn't have been over 7 amps though.

You are absolutely right. I said it had a longer focal length than your lens, but I mistakenly wrote mm, instead of cm. You are correct at about 12 cm. You are also right that you would have no spill. At least, when it is fully focused, unless you used a reflector. I intend to use mine out of focus for both high and low beams because focus would by too small a hot spot and way too much throw for driving around. I would like to check into your lens though. It sounds interesting.

I really like how you ask "smart questions". Keep up the great work. I think this is a very good project you have embarked on.

EDIT: Here is a link to Fritz's (see next post below) thread on the lens he mentions.

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I think the Fresnel lens is the right approach, as an aspheric would be heavy and expensive, according to the Fresnel lens makers anyway. The one I have is called a stage lighting lens. It has a shorter focal length and focuses nearly all the light from an XM-L into a small spot. With your larger led, the spot might be too big for your purposes, and the price has gone up since I got it.

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Thanks for your inputs Fritz & ImA4Wheelr! Well, you made me curious. Very curious. So curious that this message appeared on my screen:

Now, where’s that fast forward button so I can get it faster? :bigsmile:

I guess 130mm with 50mm focal point will do the trick. If I have the 90degree lens on, at 5cm away from the LED there’s no way any light would go past the 130mm lens. This means all the light will be captured and focused. I’m curious on how it will focus it. If it can focus it in a spot as tight as the A5 fresnel I already got, then ladies and gents, we have a winner!

I do have a bit of doubt, because that LED is still huge (20x20mm emmiter area), so another lens might still be needed. But it’s definitely worth a try.

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hmm… this is reminded me of one of my post regarding using Fresnel lens in the flashlight.
I did experimented with magnifying glasses lens mounted on zoomable acrylic tube.
I found out, it work wonderful with any flood type kind of light, hence the mt-g2 IS perfect example.
between 6” to 12” is the perfect length for a bright hot spot, anything more it will be more intense and pencil beam throw ( pretty much useless )

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Light up the night! I love it :slight_smile:

Is that Nikon F6 with MB-40 in you avatar picture?

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Will only a hollow tube work that good instead of a “full” cylinder? I have a 6-7mm thick plexi cylinder, it’s meant to be used for closing/opening shutter curtains. I’m going to try and make a custom lens for an XML-U3. Let’s hope that dremel felt tip can polish acrylic. :smiley:

Could you please write here a link about acrylic tubes and flashlights? I couldn’t find anything using the search tool.

Now, I was thinking. To get 10.000 lumens I would need about 8 XML-U2/U3s. They can be focused really good by using cheap TIR lenses like these ones. I could just remove the mirror of my high beam completely, stick 8 of these LEDs on a radiator, put a fan and a 100degree Centigrade thermostat to shut all down if that temp is reached, and that’s that. A lot simpler IMHO.

The wiring will be direct drive, 4 LEDs wired in series at the 14.5v car-on voltage will be getting 3.65V each. At that voltage, I thing 4-5A per LED would be the correct current(please correct me if I’m wrong). So the whole assembly would be draining 18x8=144W ( 10A @ 14.5v). So I think I’ll need to upgrade my 10A fuses and possibly the relays as well. But still seems simpler than making an optical system for the “little one”. And also, at 4-5A they should output ~1500-1700lm?

@Kodachrome40, that’s my old D90 + grip, I just love how the cheap 50mm 1.8 lens looks on the camera. Got a D800 recently, but there’s no need to change the photo. They all kinda look the same.

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Nice experiments there Boggy. I just wanted to say something about Fresnel tech, I believe that a Fresnel is not that efficient compared with a traditional lens. I am not sure but IMHO its like ~70~80 of the % of an aspheric. But there are pluses too like costs and easy of use. Still take this as an opinion not an absolute and proven fact.

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Thanks Ervin! I did take into account that I’m losing some(actually a lot of) light in the lens itself, but I do have the ability of cutting it to fit my car’s reflector, and I can also buy an A4 sized one for $3 from China.
An 18cm glass aspheric… Well, I’ll need to function with only one kidney, because I sold the other one to buy the lens.

And I could only lift it in about 5 years, when some crazy bionic arms get commercially available. :smiley:

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I think Fresnel lenses can be as efficient as aspherics, depending on the design. The one I have appears to lose little light, even though its elements are narrow. There is always some scattering by the steps between elements, so efficiency may be greater for fewer segments, which also means thicker. The minimum loss at the steps is of the order of the wavelength of the light, so it can be small. But it also depends on the detailed shapes at the steps.
Like an aspheric, it works much better one way up than the other, it took me a while to figure out how to use it.
Lighthouses had lenses that wrapped around the source with the outer segments working by total internal reflection (TIR), rather than by refraction. That allowed almost half a circle of light to be used. It also meant that chromatic aberration from the dispersion in the lens material was greatly reduced.
I can think of two reasons that flashlight manufacturers have not used Fresnel lenses more. One is that they may not have considered it. The other is that they are not as pretty. They must be cheaper to produce in quantity than either aspherics or mirrors.

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I’ve abandoned the ideea of using a 100W LED for this project. Instead, I made a simple unit out of 8x XM-L U3’s. 2x4 LEDs in series. This means that at a car’s running voltage of 14.1-14.3V I will have 7-8A draw. Meaning 100-115W. Cooling is provided by an AMD CPU cooler, because it has a huge flat base. I can hold my finger on the LEDs and LED aluminum pills(to test thermal transfer) after 15-20mins of full power blasting.

It’s a LOT more focused that whan I could ever do with the 100W big boy and because of this they’re a lot more suited to be used as a car’s high beam.

More videos to come, but this is how powerful it is at 14.1V @ 7.3A :bigsmile: :

I did a comparison outside with the 100w LED withthe 78mm aspheric. It was bright and more focused than with the 44mm. Still, I could light up a whole building block with it.
100LED + 44mm aspheric + my fresnel “canon”. Hugely more focused and powerful. I put a friend in front at about 20m to see how bright it is.
Then the XM-L array. It was blasting out light. Focused really nicely in about 10-20 degree angle. A lot more range than the 100w led + anything I could put in front.

So yeah… I’m waiting to get more LEDs and see how TWO of these light up 8)

P.S. As you can see in the burning pattern, one LED has a boo-boo. When I first put the lenses on I used a stupid synthetic adhesive, and I must have touched the LED with it. In time it started burning the led capsule. I will replace it.

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And a test in daylight! I honestly did not expect it to perform like this, so I’m very very pleased by the result. :bigsmile:

The permanently lit headlights in the video are 55W HIDs for the short beam. These are ~5000 lumens / bulb, but the light is spread. I also switch on the high beam later on in the video for comparison(55w Philips Xtreme Vision). These easily outshine a 100w led with 44mm aspheric regarding range because the mirror focuses the light quite well. However, compared to the XM-L’s, they simply don’t stand a chance.

And remember, this is only one CREE unit. There will be two in the end :smiley:

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Nasol sa ne intalnim in trafic :bigsmile:
Succes

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With multiple emitters, you also have the choice of combining several different optics for a more dispersed beam. Or you can shape the beam with optics that give strange patterns rather than round spots.

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You’re totally right, however this is not the case because the goal is to achieve range. I would have liked an even tighter spot, but this is about as good as it goes with using TIR lenses*.

Once mounted inside the headlight there will be more spill because of the transparent plastic cover in the front.

*I modified a small TIR lens like the ones in the video with aluminum foil backing on the lens. It increased luminosity in the spot with about 15% if I remember correctly. I will redo the measurements.