Help designing a compact 26650 light

I've been thinking about making a dive light for a few years now but always had to much on the go, now my work has slowed down and the major reno's to the house are done so I figure I will take the next several months to configure and design several underwater ONLY compact 26650 wide angle video lights for my Go Pro camera. I have so many questions with only assumptions for answers So any help would be muchly appreciated.

With that in mind I have a questionnaire for all if you don't mind.

Buy all parts separately from different manufactures then assemble it myself?
Buy all parts from the same company and assemble it myself?
Buy all parts from the same place and have them assemble it? or Have them partially assemble it?


In your opinion what would be the best driver for a single XM-L2 U2 1X 26650 underwater ONLY light?


What modes should it have? Start at 100% then 65% then off.


Regulated output? ....Yes


What degree would be best for an Hero Cam underwater video light..... Mule



XM-L ....XM-L2 U2


Color temperature of the LED?....5000K


Double O-ring on the tail.....Correct and this would be the only way to get in.


Actually I'm thinking of only having the tail cap screw off, bonus would be the spring from the tail cap will hold the battery and LED module in place, if ever dropped the spring could dampen the blow.
It would also be easier to replace the "Drop In" and there is a much less chance of water entering the body. Sounds too good.... whats wrong with this idea?


What are some features you would like to see on a compact 26650 underwater video light?

What about 4X AA instead of 26650?...No, 26650

It's possible to run an XML with a single cell, I built a light that does that. It's a 26650 as well, and has only the tail cap screw off. Anything smaller than an XML is just not worth the trouble, and anything bigger is going to suck down your battery in nothing flat.

Definitely you want regulated output. Without it the light level will be constantly dropping as the battery discharges.

The 4xAA (NiMH, i assume) will give you better overhead (battery voltage greater than LED voltage). Any driver you are going to find to run one LED off one LiIon or 4xAA will need some overhead in order to operate. Some need more than others. When the LiIon is near the end of charge, your overhead will dop below the minimum and the driver will no longer have the ability to push full power to the LED. AA's will also have less capacity.

If you are talking 4xAA LiIon, they would more likely be referred to as 14500 than AA, but that would be a simpler solution. Set them up as 2S2P, and there are scads of cheap drivers to choose from. You'll still get less capacity though.

For a video light, I think you want to be careful of what driver you choose. Some drivers control brightness by switching the LED on and off very rapidly. This is referred to as PWM dimming. Your eyes can't detect this if it's over 120 Hz or so, but it can interact with the video camera scanning sequence to produce bars and other artifacts in the image. There's been some discussion of this on the forum, but I don't recall exactly where.

As far as brightness steps, for human eyes, I prefer each step to be a factor of 3 or so. That means a geometric progression (1,3,9,27...) instead of an arithmetic one (1,2,3,4...). For daylight diving, I find that 100% and 30% are the only modes I'd ever want, unless 100% is SERIOUSLY more light than I've ever used, i.e. several thousand lumens in a tight beam. I haven't been night diving in years; maybe I'd want a 10% mode for that, but probably not - just widen the beam.

In photography, most things (well, shutter speeds definitely, and apertures too, I think) are done in factors of 2. So you might want 100, 50, 25. Your light is going to be kind of underpowered, so I wouldn't think you'd even need modes unless you're worried about runtime. Just run full blast and adjust the camera. That certainly would make operating the light easier.

I doubt very much that you are going to be able to buy all the parts and just assemble them, whether from one vendor or several. You're sure to have to do some machining or other mods to get things to work. And the only way I know of to get someone else to do assembly is to contact one of the custom builders on this forum. The lights that are easy to mod aren't dive lights, and turning a non-dive light into a dive light is not a trivial task. MAG lights seem to be the only ones suitable for this. There's lots of discussion of them here. A C-cell light would fit your 26650 nicely.

The reason for double o-rings is not to overcome improper design. If the first one leaks because of bad design, the second one will leak for the same reason. The reason I built double o-rings into my light is that a tiny bit of damage or bit of debris on one o-ring can flood a light, but it's unlikely to be duplicated on the second ring. Proper design and proper maintenance are a must if you don't want to flood your light, whether you have single or double rings.

I prefer neutral white (4000K) or slightly warm (3000K) when diving; otherwise everything looks blue. Keep in mind that most LEDs have poor CRI, meaning that they don't reproduce all colors very well. This is because of how white LEDs are made. They are all actually blue LEDs, with phosphor coatings that turn some of the blue light into other colors. Something that's cyan or orange may appear much less bright than it would in halogen light because the LED has much less output at those points in the color spectrum. Since you are using a GoPro, I'm guessing you aren't too hung up on fine details like this, but you might find that something like a Cree MCE EasyWhite that has 4 separate LEDs with different phosphors may produce more 'natural' colors. It might complicate (or simplify) your design though.

By the way, your avatar is seriously distracting while I'm trying to type this reply .

D

DIWdiver thank you for your reply.

26650 fits into a C mag with out any slvs needed? does it rattle at all?
What Driver should I use for right now?
What is a good optic to use that gives me soft edges and an 80° 90° or 100° beam?
As for machining.... Machining costs around here are really really expensive so that leaves someone on this board or far far away.

Possible you could post some pics of your light that you made?

I would not go for one of those modern action cams with anything less than 120º. All this kind of cameras have ultrawide lenses, so unless you want a "tunnel effect" I would use no optics at all (bare LED).

Fortunately its capability on low light conditions has improved greatly, but the more light, the better quality image. So, in this case, you should be more interested on output than on runtime. A video light -which is not and should be not your primary diving light- with 40 minutes, would give you more than enough footage to edit the most boring documentary ever.... unless for technical reasons (repairs and inspections) you should record the whole dive, but that is another story.

So, my two cents for a simple, usefull, and quality UW video-photography light. just level (just máximum); no secondary optics, easy one hand operated switch; 30 minutes or even less.

Javier

Hey Javier,

Wouldn't no optics create to much backscatter in the video?

Backscatter is higher when the distance of the camera lense and the lighting device is shorter, that is the reason we use arms, to get some distance. Ideally one of the team members is the camera while other (others) is the illuminator.

This is my setup I made at work last year.... before my trustfire lights corroded into nothingness :fail: due to saltwater.... and the lights shorting out...
The camera is about 12" away from the lights. I'm thinking on my new lights the LED will be 3/4 to 1" away from the front of the light... with no optics.
I will be cutting off the saddles these lights are sitting in and making 2 smaller ones extending out from each arm like the last picture shows.
4 lights putting out 1000 lumens each with no optics should do the trick yes?
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I do preffer flexible arms, as you can bend them depending on the conditions, anyway, 4000 lm should be more than enough, but there is not a fixed rule, as it will be related to:

1. Camera, lens, low light sensitivity.
2. Particles in suspension. From cristaline water to fluid mud.
3. What quality of footage do you expect and what for. (Scientific, broadcast, private, educational...)
4. Distance of the object to be recorded.

Time ago I prepared a lighting system for a ROV with two 505 nm lights, focused beams, for submarine big tube surveillancs... The light was awfull for anything else but inspecting the surface of the tubes, but for example on this case was the perfect setting. Tektite used to have a UV light for epoxi curing, and leakage detection of cooling systems.... What I want to mean is that down there the conditions and what you want to get can be very different, thus the lighting system you need.

regards,

javier

Well i would like to reach out to 30' so I think I will need more then 4000 lumens or use an optic. After looking at alot of video lights it seems most are between 60º and 90º. Underwater kinetics Aqualite 90 (90º) has made their light in mind for people that use wide angle cameras...so they say.

"The Aqualite light has a small dome port, just a small bubble really, sitting just in front of the LED bulb. This dome port actually keeps the angle of the light exactly the same underwater as in air. The Inon light beam (and the beam of all the other lights in the world that have a flat glass port) will scientifically narrow down when underwater. Once the Inon is in water the light beam narrows down to about 50 degrees from 65."

So I be thinkin I should find a 100º optic with this dome port in front so the beam stays the same....

Edit: Took me an hour but I think the optic is called a TIR (Total internal reflection) So I'm trying to find a 100 degree TIR... with no luck lol