Designing a focusable LED dive light.

[Packhorse]

There has been some discussion in another thread about building a focusable LED dive light.
I believe this deserves its own thread.

What I have in mind is the use of a SST-50 LED and an aspheric lens, more than likely one of Ahortons which I have had much success with in other projects.

A single SST-50 will provide enough lumen for a really bright hand held light or a not so bright cannister light respectively. In a hand held the burn time will be limited while in a can light the output will not be as great as what other LED clusters could provide.
So what to build? a hand held or a can?
Ideally both! Use the same head that can be connected to a body containing batteries or to the end of an umbilical that connects to a battery cannister.

Biggest issue is how to focus it.
I guess the easiest way is to design it along the lines of a mag light where the head is threaded and turning it moves the lens away from the LED. Since the focal length does not need to change much it only requires a small twist to change focus. This can be adjusted by the pitch of the thread.

Switch.

I think the switch should be twist on /off like the mag solitaire so the same twisting action activates the focus and switch or reed switch based.

Driver.
Driver needs to be able to supply as much current as a SST50 can handle and have at lease 2 power levels. Voltage In should be capable of at least 12v nominal.

Materials
Head should be aluminium. Body should be POM.
I have owned all aluminium dive lights and the W200 which is aluminium head and POM body and I much prefer this setup.

Thoughts anyone?

 

[Linger]

Re: Designing a focuaable LED dive light.

Switch - disagree, I suggest tail-cap twist switch (IST). We don't need to complicate focusing by including a switch as well. On a systems level, i'd like the functions to be separate and accessible separately. This can still incorporate your hand-held vs. umbilical desire
Tailcap twist is dead simple - close fully to complete circuit.
More advanced - resistor ring for a low mode when loosened, full power when fully tightened

Focus threading - Only related to adjusting the focus. For robustness, this can be over-extended a great deal. For example, if only 6mm of threading provide sufficient run to adjust the lens, 30mm can be used, book-ended with double O-rings. Simple nipple / bump can prevent over-turning and keep the lens from crushing the emitter. I imagine this more as a sleeve that covers over the front half of the light (as opposed to a p60 type light where the bezel has a few mm of threading connecting the light, I see this dive light as having a front sleeve that contains the lens, bezel ring, and a long tube that extends down a good distance, overlapping an inch or more. The front sleeve ends about inline with the emitter, so that this tube does not in-inadvertently insulate light engine and driver as we want the body near them exposed to sea water

Bezel ring - this opens to access to remove glass and access emitter.

 

[Packhorse]

Re: Designing a focuaable LED dive light.

Excellent points.

Although I believe adding another threaded section at the base for the switch adds complication to the design and another failure point.
In saying that having the switch incorporated in the focus set up can be a little complicated too.
Also the switch has to be workable with the can light set up and hand held set up.
Nothing to say the can light set up cant have the switch on the can while the hand held has it on the body section.

 

[Linger]

Re: Designing a focuaable LED dive light.

I believe adding another threaded section at the base for the switch adds complication to the design and another failure point.

Correction - no additional threaded section needed. One set of threads to screw on the tailcap, as it closes it a resistor in the tailcap contacts a ridge in the body tube to provide low mode, fully tightened the end plate of the cap contacts the body tube by-passing the resistor with a full electrical pathway.
The theory was inspired by this:
http://www.malkoffdevices.com/shop/highlow-bezel-switch-for-md2-p-58.html

*the twist switch, or two mode switch easily adapt from hand-held to can. The mechanics don't change at all. Imagine the IST switch, simply a flat surface that makes contact with the battery tube: it doesn't matter if -'ve power comes to the tailcap through the spring from a battery terminal, or to the tailcap through a gland.

 

[Packhorse]

Re: Designing a focuaable LED dive light.

Correction- It will require an extra threaded section as what I had in mind was a tail cap less design much like the W200.
This design would require removal of the LED assembly to change batteries of course.

That said I would not rule out a tail cap switch system.

 

[Linger]

Re: Designing a focuaable LED dive light.

affirmative, we are clear.

 

[whitenoise]

Re: Designing a focuaable LED dive light.

I can't comment on the more technical aspects, but I agree with Linger regarding the focusing device. I think trying to combine the on/off with focus would be too complicated, and could end up you getting annoyed with the light when it turns off whilst trying to focus/defocus! By keeping the two functions separate this helps concentrate your focus (no pun intended ) on just one particular function.

Love the idea that you get resistance, or it can't turn anymore, once it reaches full focus/defocus. This is great attention to detail, and important for numpty users like me! This means that you couldn't accidentally crush the emitter like Linger said, or I guess the other way expose the head to water.

I'd prefer a hand-held, but if you were looking to build both then this wouldn't really matter

Driver - Agree about the different power levels supplied to the hand-held. Perhaps full/half/quarter power as settings which can be selected? This would allow maximum power for short periods, as you probably wouldn't want this all the time, half power for maybe normal use, and quarter power for perhaps night dives where you don't want to light up too much? Excuse my lack of knowledge here but I know you get 18680 (sp) type batteries and the 2xxxx versions, but did read somehere used a 4xxxx type? Can't find the thread now, but wouldn't this give more juice?

Materials - Ideally to keep the cost down it would great if you could use something already existing and mod that, rather than to create something custom made. Although not sure this would be possible?

Keep the ideas coming!

 

[jspeybro]

Re: Designing a focuaable LED dive light.

not sure if a tailcap switch in case it is a handheld light is the best option, but I would also not combine it with the focussing mechanism.

The result of using a tailcap switch is that when you remove the body and batteries, and attach a cable to a canister, the switch will move to the cannister. I never used a canister light, so can't really comment on having the switch on the canister.

Johan

 

[Packhorse]

Re: Designing a focuaable LED dive light.

Having the focus and switch in the same twisting action makes it a one step action to turn it on and focus it to the setting you want. Also less moving parts and less failure points.


Also I think this will have to be a total custom build as opposed to a modded light. Cost isnt really the issue, building a focusable high powered LED light is.

As for batteries for the hand held version I am thinking 2 x 18650's. 26650's could be an option but I think this would add to the bulk of the light.

 

[wquiles]

Re: Designing a focuaable LED dive light.

Great thread Packhorse - thanks for starting this

Will

 

[Packhorse]

Re: Designing a focuaable LED dive light.

Great thread Packhorse - thanks for starting this

Will

Thought you may be along soon. :twothumbs

 

[whitenoise]

Re: Designing a focuaable LED dive light.

Having the focus and switch in the same twisting action makes it a one step action to turn it on and focus it to the setting you want. Also less moving parts and less failure points.

Sounds sensible when you think about it. So how would this work? When the light was in a an off state, would simply twisting the head turn the light on and some more twists start focusing/defocusing the head?

Also I think this will have to be a total custom build as opposed to a modded light. Cost isnt really the issue, building a focusable high powered LED light is.

I take your point, probably easier to build something from the ground up then to retrofit an existing body, especially as this is probably going to be a complicated build.

As for batteries for the hand held version I am thinking 2 x 18650's. 26650's could be an option but I think this would add to the bulk of the light.

Found that link I was referring to, although they are talking about 26500 (is that same as your 26650s?) and 4000mah which is where I was getting confused. While I don't know the dimensions, I think one or two 26650s would be better than 2 x 18650's. The hand-held light doesn't need to be really thin like Barbolights U15, and you do want something good to grip, so why not make use of the space and additional capacity and use some 26650s? It doesn't add that much extra width?

 

[wquiles]

Re: Designing a focuaable LED dive light.

...although they are talking about 26500 (is that same as your 26650s?) and 4000mah which is where I was getting confused. While I don't know the dimensions, I think one or two 26650s would be better than 2 x 18650's...

The first two digits refer to the nominal diameter, the next two are the length in mm, and the last is the shape, 0 being a cylinder:
26500 = 26 mm dia, 50mm length
26650 = 26 mm dia, 65mm length
18650 = 18mm dia, 65mm length

Note for reference:
- the "C" Mag body takes C size cells, which are 26mm in dia
- most all of the Surefire lights take the CR123 cell, which is 16mm in dia

In general, the larger overall physical size of the cell, the higher the mAh ratting/capacity. But to really compare the cells you need to know the rated mAh, which varies also depending on the chemistry used. Also remember that vendors/distributors play spec games with the cells, so they might be "optimistic" as to their actual rating

This sub forum has great reviews of actual mAh measurements (which you can make on advanced chargers like the Triton and others):
Flashlight Electronics - Batteries Included

Will

 

[Linger]

Re: Designing a focuaable LED dive light.

*cr123 is comparable in size to the rcr123, also known as the 16340 cell.

Edit - suggestion taken, Thanx wquiles

 

[wquiles]

Re: Designing a focuaable LED dive light.

Please edit: cr123 is 16mm

*cr123 is comparable to rcr123, also known as the 16340 cell. Most SF lights fit a cell with a 16mm diameter. (18mm does not fit, thus the custom boring threads in the Custom B/S/T)

Opps - my bad

Edited accordingly.

 

[Packhorse]

Re: Designing a focuaable LED dive light.

I always thought the last digit was referring to the shape. 0 being cylindrical.
You may also want top edit the length. 18650's are not 650mm long, just 65mm.

 

[wquiles]

Re: Designing a focuaable LED dive light.

I always thought the last digit was referring to the shape. 0 being cylindrical.
You may also want top edit the length. 18650's are not 650mm long, just 65mm.

Another Opps. Thanks. Post edited again - one of these days I will get it right

Will

 

[whitenoise]

Re: Designing a focuaable LED dive light.

Thanks for the useful info wquiles, Linger and Packhorse - its useful to know that those numbers actually refer to something!

Say you are using two 26650's in the light with 5A, 2.5A and 1A settings (for example) how long would the light last?

 

[wquiles]

Re: Designing a focuaable LED dive light.

Thanks for the useful info wquiles, Linger and Packhorse - its useful to know that those numbers actually refer to something!

Say you are using two 26650's in the light with 5A, 2.5A and 1A settings (for example) how long would the light last?

Nobody can answer that question exactly without knowing the capacity of the batteries in question and the vf of the LED in question. Now, if you make some assumptions, you can get an idea of what to expect.

If we assume these specific 26500 cells:
AW IMR26500 cells ... at 2300mAh

and if we assume a vf of about 3.7 volts, then:

available battery watts = 3.7 volts * 2.3 Ah * 2 cells = 17 watts

available power for LED = available battery watts * converter efficiency = 17 * 0.8 = 13.6 watts

LED power at 5A = 3.6 * 5 = 18 watts
approx. runtime at 5A = 13.6 / 18 = 45 minutes

LED power at 2.5A = 3.4 * 2.5 = 8.5 watts
approx. runtime at 2.5A = 13.6 / 8.5 = 1 hour with 36 minutes

LED power at 1A = 3.2 * 1 = 3.2 watts
approx. runtime at 5A = 13.6 / 3.2 = 4 hours with 15 minutes

(this also assumes typical vf vs. current values)


If the 26650 cells have more capacity, then the runtimes would be proportionally longer.

Will

 

[whitenoise]

Re: Designing a focuaable LED dive light.

Thanks for that Will. that's great Looking through your calculations it all makes perfect sense. If you used 26650s instead of 26500s and perhaps with a little more capacity, then I think you might be able to get an hour at full power. That's probably more than enough since you are not going to use the light constantly through the dive, and there may be occasions where you don't want to use full power. If new batteries were needed on the 2n dive, then you could simply switch over to a spare pair and then charge both sets in the evening. Replaceable batteries I think are much better than a build-in battery, as after a while if the batteries start losing their charge, simply ditch them and buy new ones!

One thing that hasn't been mentioned is how would you select the different levels on the light? Twisting the head turns it on/off, and focuses/defocuses, but how would you select say half power?

Looking forward to hearing more!