# DIY K2 Helmet Lights



## p97z (Dec 19, 2006)

Here is a picture of my DIY helmet lights They are Luxeon K2's running at 1000ma. Together they put out a couple hundred lumens. I run them off AA's sitting in my back jersey pocket.


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## Low_Rider (Jan 15, 2004)

Nice work *p97z*! :thumbsup:

Are you direct driving them, or running some kind of driver? I assume they're cut down Mag Lite bodies, are you running the standard reflector?

Dave.


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## p97z (Dec 19, 2006)

Actually they are cut down Brinkman lights. The Brinkman head allowed me to just drop in an IMS 20 without any filing or sanding. I only needed to file the stars to get them to drop in the head. Each light has a downboy regulated at 1000ma.

I used mag light caps on the end because they looked cool and gave a little better water tight seal.

I can also pull out the reflector and drop in different degree optics if I want. By turning the head you can snug up shorter relectors.


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## p97z (Dec 19, 2006)

Here are some pictures of the heat sink and the light in pieces. I filed the tabs off the 20mm optic lens. The heat sink is glued into the tube using Arctic Alumina.


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## Lev (Oct 12, 2004)

sweet setup. what would you say is the estimated weight of the system?


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## msxtr (Dec 10, 2006)

Hi, good job!!!!!!!! what batteries you use with this lights?

Greetings - Saljudos

msxtr


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## wake_100 (Aug 21, 2006)

need more info, its really a sweet setup


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## p97z (Dec 19, 2006)

They weigh about 60-70 g each. I'm using 8 AA's in my jersey pocket. The battery pack is made using two 4AA battery packs from radio shack. When I run 1 light I use a 4AA battery pack from radio shack.

I can change the reflector from an IMS 20 to a flood and put it on my bars. There is a notch in the back shown in the first photo. The notch is used to keep the O-ring from slipping when it's mounted on my bars. The O-Ring is attached like a DiNotte light.


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## wake_100 (Aug 21, 2006)

so how much did it cost for the overall project and where did you get the stuff for it?


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## p97z (Dec 19, 2006)

Downboy from here. http://theledguy.chainreactionweb.com/product_info.php?products_id=478

20mm Reflector from here
http://theledguy.chainreactionweb.com/product_info.php?cPath=48_50_64&products_id=400

Battery holder from radio shack... with a switch...
http://www.radioshack.com/product/index.jsp?productId=2062254

I have used a AA mag light but it's a lot of work to get the reflector to fit. I bought a brinkman from here.
http://www.brinkmann.net/Hot Deals/...lashlights+&+Spotlights&sku=804-1040-0&id=673

I think you could use one of these flashlights and use the switch from the tail.
http://www.brinkmann.net/Hot Deals/...lashlights+&+Spotlights&sku=800-1040-5&id=652

Arctic Alumina from here
http://theledguy.chainreactionweb.com/product_info.php?cPath=48_39&products_id=171

K2 LED from here
http://www.ledsupply.com/05027-pw14.php

Instead of Arctic Alumina i have used JB Weld.

Downboy 16.50+shipping
20MM IMS 5.00+shipping
AA 6.80+shipping
JB Weld 6.00
Flashlight 6.99+shipping
Wire and Connectors ~6.00 radio shack
LED 8.99+shipping

Total with shipping was less then $60.00

I had the 4AA batteries and charger.


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## p97z (Dec 19, 2006)

If you don't want to spend the money on a downboy, you can use a 1ohm resistor. I have a mag light as a backup that uses a resistor. You are not as flexible though using different battery packs with different voltages.


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## wake_100 (Aug 21, 2006)

wow, any beam shots of them?


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## p97z (Dec 19, 2006)

Here is a shot up my stairway. I was standing 13 stairs back. I don't have any outside... yet.
Shutter speed 1/8 sec
Aperture F/2.8
ISO 160


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## wake_100 (Aug 21, 2006)

is the stairway with all lights off? both lights, or just one? also is the heat sink a solid piece of aluminum stock? With time you will be asked all these questions, I am proud to be the first, I love how small the lights themselves are, its really neat.


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## p97z (Dec 19, 2006)

All house lights are off. Both helmet lights are on. The heat sink is a solid piece of aluminum a little over an inch long (Home Depot). It is epoxied (Arctic Alumina) to the case and there is just enough room for the wires to run through (one side). The length of the lights are 3 1/4 inches but could be a little longer or shorter depending on the optics (the head is free to turn in or out). 

I used two downboys so I can run one on the helmet and one on the bars if I want. When I run one on the bars I use different optics so it's flood and not a spot (like in the picture).


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## achesalot (Nov 8, 2005)

p97z said:


> Here is a shot up my stairway. I was standing 13 stairs back. I don't have any outside... yet.
> Shutter speed 1/8 sec
> Aperture F/2.8
> ISO 160


p97z. I'm sorry that you don't have an outside. It must be rough riding your bike up and down those stairs 

It looks a little on the spotlighty side, and that is a typical problem with the Luxeons and IMS 20 reflectors. Flashlight guys just love that throw. On the trail we need a combo of the throw and some side fill. I think my first LED bikelight was a flashlight mod as well. It really eases the problem of building a housing, which turns out to be most of the work.

Nice work and thanks for sharing. It's certainly a good lighting solution for $60.


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## p97z (Dec 19, 2006)

achesalot,

Your design inspired my first (and second) LED bike light. I like your triple square tube design, it’s simply brilliant. Reading your how-to got me interested. The only problem I had with my implementation was the water resistance. I put a piece of plexiglass in the front and put a thin layer of caulk around it. I got caught in the rain twice and both times I had to take it apart to dry it out. My cuts weren’t that straight so some water must have leaked in.

With the flashlight design I can spread them apart and get a little wider beam but your right with 20mm IMS reflectors, it’s on the spotty side. I have tried it with some 6 degree optics also. It's not as spotty.

I’m working on a triple CREE driven by a bFlex now…


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## achesalot (Nov 8, 2005)

p97z said:


> achesalot,
> 
> Your design inspired my first (and second) LED bike light. I like your triple square tube design, it's simply brilliant. Reading your how-to got me interested. The only problem I had with my implementation was the water resistance. I put a piece of plexiglass in the front and put a thin layer of caulk around it. I got caught in the rain twice and both times I had to take it apart to dry it out. My cuts weren't that straight so some water must have leaked in.
> 
> ...


Glad I was able to inspire you 
Yes the waterproofing thing has always been a challenge. I've not had mine leak, but I've only ridden in a light sprinkle or two. The power connector and switch I use are not really weather-rated either.

Good luck with your Triple Cree/bFlex... can't go wrong there. What lenses are you using?


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## p97z (Dec 19, 2006)

I'm not sure about optics... I've got some CREE and Seoul P4s on the way. I have some L2 optics now. I have one Carclo 6deg now. The Carclo is awesome! I'm waiting to see what works with the Seoul then i'm going to mount them in a cigarette lighter adapter. 

If the lighter adapter doesn't work... I'm going for the square tubing idea.


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## achesalot (Nov 8, 2005)

p97z said:


> I'm not sure about optics... I've got some CREE and Seoul P4s on the way. I have some L2 optics now. I have one Carclo 6deg now. The Carclo is awesome! I'm waiting to see what works with the Seoul then i'm going to mount them in a cigarette lighter adapter.
> 
> If the lighter adapter doesn't work... I'm going for the square tubing idea.


Same here... waiting on some Q2-bin XR-Es and some U-bin Seoul P4s that just shipped out today. I don't know what to use with the SSC P4, we'll just have to see what works best.


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## p97z (Dec 19, 2006)

I love the group buys at candle power forums. The nice thing about these brinkman mini mag lights is that I can drop in any 20mm optic and test them. Let me know what you find.


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## twelve_volt_man (Feb 27, 2005)

*Do all 20mm optics fit in the brinkmans*

-I saw you had to file the reflector down, can you just pop in other optics or do you need to file, etc?
Thanks


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## p97z (Dec 19, 2006)

I didn't need to file the reflectors. I used an IMS 20 and IMS 17 and no sanding or filing was required. What you see in the picture is a 5 degree L2 lens.



There are tabs on the lens that I needed to file. The spot lens isn't as bright as an IMS 20. It does however have more flood/ side spill.


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## twelve_volt_man (Feb 27, 2005)

*Thanks for clearing that up for me*

I think I am going to throw together something similar when Cutter gets better LED bins back in. I am thinking 2xhelmet like yours and 2xhandlebars-I am excited to see how it turns out

Thanks


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## greenLED (Jan 9, 2007)

p97z, that's a really neat setup! I used to have a NexGen 500 sammie with an IMS20 reflector and it was a kick-A light to have on my helmet. I can hardly imagine how much brighter your 2xK2's @1000mA are!! Very nice.

Could you please post pics of how you're attaching the cables to the back of the lights? I'm curious to see how you waterproofed that end.

You could probably make those heatsinks much smaller and still have no thermal concerns. You linked to Ledean's CPF thread on my taillight thread; check out his finned minimag heads - they do help with cooling. He can also bore minimag bezels so 20mm reflectors and optics fit.

Speaking of flood vs. spot, have you seen Carclo's wide angle optics? IIRC, they're something like 12x50º and would make a killer combo for a 5º optic.


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## p97z (Dec 19, 2006)

Thanks..

One of the problems with the downboy running at 1000ma is that it can sometimes be TO bright. I would like a way to step it down a notch. When i'm talking to somebody it's TO bright...

I just removed the square connector today and went with an audio style connector. The square connector from radio shack would pull out easily. It wasn't holding up well. 

You are right, the heat sink doesn't need to be that big. I made one with the star epoxied to the tube with arctic alumina and it works fine. It has been cold here 30 degrees and 40 degrees so there is no chance of them overheating.

The picture of the tail end has got black RTV in the hole. The hole is drilled just big enough to let the cable slide through and then I used RTV to seal both ends. I put some on the cable before it went in the hole then pulled it through. You can't tell from the photo. To keep the tail cap on I used JB Weld. I made a little gap between the tube and tail cap to keep the O-ring from sliding off. I use a rubber O-ring when I mount it on the bars.

Is there another place to get Carclo’s optics besides cutter?


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## Low_Rider (Jan 15, 2004)

What have you done! 

Sorry, but using audio connectors in a power related system is one of those little things that irk me. They were never designed to cope with large currents, are easy to accidentally short, and still pull out easily. It would be well worth investigating other options IMO!


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## p97z (Dec 19, 2006)

I'm not crazy about audio connectors either… I figure at 2.5 amps they should be safe. At least I can’t accidentally plug them in reverse polarity. After all wikipedia said they are used as power connectors.  

If I see something better I’ll probably use it instead. Any suggestions?


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## super-fast (Sep 28, 2006)

I always use 2.1mm DC plugs, maybe they are not completely waterproof, but they are cheap, easy to get, they hold very well.

There was a topic about connectors last week:
http://forums.mtbr.com/showthread.php?t=260607


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## Low_Rider (Jan 15, 2004)

I never had any luck with the standard barrel stye DC connectors. They were forever falling apart or vibrating loose.

To be honest I haven’t actually looked in to connectors too much. I came across the type I posted about in the linked thread above, and they did the job and were a marked improvement to other solutions that I had tried. I haven’t really bothered looking at anything else until now.

Now you pricks have me thinking about other possibilities… Thanks a lot!! 

Dave.


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## twelve_volt_man (Feb 27, 2005)

*Question about the alum. rod for heat sink*

I know its primary purpose is heatsink, but does it also provide support for keeping the LED and optic against the front of flashlight---ie what is the support for keeping the led in place

Thanks


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## p97z (Dec 19, 2006)

The head screws onto the body so that's what keeps the LED and lens/reflector in place. With a 20mm reflector, the head is further away from the front lens. I can then twist the head to tighten or loosen different optics or reflectors.

I used to piece of aluminum for more surface area against the back of the LED star. You don’t really need it I just thought a K2 would run hotter then my previous lux 3. I also wanted to be able to remove the LED incase of an upgrade so the heat sink sticks out above the top of the tube. The closer the LED star gets to the bottom of the tube the more filing and work need to be done.

Below are two pictures with two different lights. The first is the LED in the head of the Brinkman and the second is an LED in the head of a MAG. It takes more work to put the LED in a MAG because a MAG head tapers the closer you get to the tail of the head. This is why I choose the Brinkman. I just sanded the star round and dropped it into the head. You can see the thermal grease squirted out a little when I tightened the head. The heat sink sticks above the cut off flash light tube (to the blue line in the previous picture) so the star can sit with just a little thermal grease.

The whole procedure takes under an hour to make one light.


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## wake_100 (Aug 21, 2006)

where do you guys get your optics information at, its the only part that I am baffled by


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## Low_Rider (Jan 15, 2004)

There are plenty of links within posts here in the GPS and Lightning forum. The flashlight orientated *Candle Power Forums* is a great resource too.

Searching the internet with search terms along the lines of your "emitter manufacturer choice" + "optic" or "reflector" should bring up a few results. For many of us it's a process of reading the datasheets to get a rough idea, and trying these various optic and reflectors out to see how they behave in real world applications.

Everyone's ideas of a good beam varies, as does their physical light setup, so there is no real right or wrong choice as such. 

Dave.


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## greenLED (Jan 9, 2007)

p97z, thanks for the extra pics. Waterproofing the wiring is always something I'm concerned with. That's why I prefer self-contained enclosures, but that leads to other limitations...

I've never bought from them, but you can get optics directly from Carclo:
http://www.carclo-optics.co.uk/V2/OnlineStore.asp

Once in a while somebody will organize a group-buy on CPF too.

Wake_100, I'm a CPF junkie, so I get most of my info from there, or directly from the manufacurer's (pdf, website, e-mail CS, etc.). Like Low_Rider mentioned, there are many, many choices and opinions on what is "best". My advise is to disregard everybody's opinions and go with what specs are right for your application.


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## wake_100 (Aug 21, 2006)

I found some options, but I am going to use the Cree option, and I ordered some stuff, we'll see what happens and how good it is. I figure it will make a good start. 

p97z, thanks for the pics as well.


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## HomeGrownSS (Jan 18, 2006)

heres my version using the luxeon lumileds... im also running a 1000mA driver and 8AAs. incorporated 2 switches giving 4 power settings.


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## msxtr (Dec 10, 2006)

HomeGrownSS said:


> heres my version using the luxeon lumileds... im also running a 1000mA driver and 8AAs. incorporated 2 switches giving 4 power settings.


You use only 8 aa batteries for 4 leds?? it's very little, not? 9,6v/4=2,4v for led. What leds use you? luxeon 3? and the optics??

Greetings - Saludos


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## Low_Rider (Jan 15, 2004)

I’m guessing that he’s running a boost puck or similar boost regulator, with a switched array or resistors across the reference and control pins to provide dimming?


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## HomeGrownSS (Jan 18, 2006)

you are correct. im actually overdriving the resistors at max power little bit, using a buck puck and some switches and resistors between the ctl and ref pins. its pretty nice because less than full power is enough light and gives me great battery life, but i still have max power for supreme light! using luxeon 1W bc they have a nice metal backing which makes them a bit easier to work with than the 3W fro heat sinking.


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## Low_Rider (Jan 15, 2004)

That’s a huge overdrive! I can’t imagine lumen maintenance would be very good, even with aggressive heat sinking. I’m a bit confused when you mention that the Luxeon III emitters are harder to work with?

In terms of efficiency and light output, I would have thought that under driven Luxeon III emitters would be a much better setup?

Dave.


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## HomeGrownSS (Jan 18, 2006)

i pretty much copied this light setup i found on the internet.
http://www.instructables.com/id/E2K9BN5EDKEUBYRD9V/?ALLSTEPS
the 1W luxeons have a nice metal backing to them making them easier to heat sink. im working on my own setup right now, i just wanted to build and test out this one just to see.
supposedly the guy who wrote up these instructions bench tested the 1W luxeons and found that they operate at 2W ok. for my own light project im still picking out which LEDs i want to use....if you have any recommendations im all ears!


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## super-fast (Sep 28, 2006)

There are a lot better lights to copy then that light. I really don't understand why he used 1 Watt luxeons and not 3 Watt luxeons. When you overdrive a led so much the life of the led will be a lot shorter and it will start to lose a lot of lumens after some on-time. 
Attaching leds in parallel is the other strange idea, the differences in forward voltage between leds from the same bunch are too big. A difference of 0,2V is not extremely big and it makes that one of the leds takes 700 mA and the other one 1000 mA. So that isn't a good design, he just should have used 2 regulators instead of 1. (So 2 leds in serie with one regulator, and the other leds also in serie with other regulator.).
I don't know how he wants to get 500 lumens out of that 4 leds. He writes it put out 85 lumens at 3 Watt, 4*85= not 500+ lumens. 
There are a lot better designs here on Mtbr and CPF. Luxeon leds are out dated since September last year, for a home build light I would pick one of the following: Cree XR-e, Seoul Semiconductor P4 or the Edison K-series.


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## HomeGrownSS (Jan 18, 2006)

super-fast said:


> Attaching leds in parallel is the other strange idea, the differences in forward voltage between leds from the same bunch are too big. A difference of 0,2V is not extremely big and it makes that one of the leds takes 700 mA and the other one 1000 mA. So that isn't a good design, he just should have used 2 regulators instead of 1. (So 2 leds in serie with one regulator, and the other leds also in serie with other regulator.)


in the datasheet for the buckpuck they give some recommended setups and there's more than one parallel setup version. they seem to think that the LEDs are close enough it doesnt matter. but, im still pleased with the turnout of this light, and im working on better second version, with better LEDs.


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## Low_Rider (Jan 15, 2004)

Running multiple emitters in parallel usually isn’t a great idea. 

As LED’s have a negative thermal coefficient, the emitter which pulls more current (due to a difference in forward voltage between emitters) will run warmer, while the other emitter will run cooler. The problem here is that the forward voltage will shift a little with temperature, and as a result the warmer emitter will experience a drop in forward voltage and continue to pull more current, while the cooler emitter will pull less. In extreme cases (when emitters are substantially overdriven or poorly managed thermally) lumen maintenance will become an issue very quickly. 

I only just noticed that you’re running green emitters too, I originally thought your camera was just being overwhelmed by the light output. I roughly understand the theory behind the eyes extra sensitivity to colour around this wavelength (hence the rubbish “500 lumen” claim), but I once tried an array similar to this, and there was no way I could ride with it. :eekster:


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## HomeGrownSS (Jan 18, 2006)

makes perfect sense. for my next one i was planning on driving three luxeonIII in series with a 1000mA driver.


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## Low_Rider (Jan 15, 2004)

Yeah for sure. That would be a nice setup, although they’re actually getting a little outdated now! 

A triple Cree XR-E light built with the Cree’s mounted on stars and driven around 500-800mA somewhere would be a great solution too. 

There are plenty of examples of similar lights like this here on MTBR. :thumbsup:

Cheers, Dave.


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## super-fast (Sep 28, 2006)

Take a look at the measurements of Newbie from CPF, the differences in 1 lot are already to big for parallel connecting leds I would say:










You can be lucky and it works out good for you, but when you're not to lucky and you get the highest light blue led you have a problem when you have connected the leds parallel.


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## FlatFender (Aug 28, 2006)

So, I just copied this, except I used a mag lite, and a resistor. Is there really any disadvantage to using the resistor?


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## Low_Rider (Jan 15, 2004)

Which light did you copy?

Generally the only disadvantage of using just a resistor is that the output will not be regulated, and as a result the light output will slowly diminish during the duration of the burn time. Obviously it would depend on your battery and emitter properties as to how the intensity vs. burn time graph would look, and how noticeable it would be.

With a regulated system, depending on your battery pack and choice of regulator you would usually see a reasonably flat output curve (constant light output) until the end of the burn time, where the output will quickly diminish as the regulator falls out of regulation.

Again, it would depend on your battery pack and regulation as to how the intensity vs. burn time graph would look like exactly, but most prefer some form of regulation as it does hold a constant light output for the majority of the burn time with most setups. 

Dave.


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## FlatFender (Aug 28, 2006)

Low_Rider said:


> Which light did you copy?.


I copied the OPs light


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## p97z (Dec 19, 2006)

I think the MAG light I made is better quality then the Brinkman light. The MAG is a little heavier because the aluminum it thicker. I used a resistor and a lux 3w in the MAG and it works fine. Running on 4 AA's it goes an hour and a half before I notice the output getting dimmer. My Brinkman with the K2 would go dim fast after 1 hr and 40 mins, on 4 AA’s.

I just put a SSC P4 in the Brinkman and it’s brighter then both K2’s! :thumbsup:


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