NEXT 75mm Zoom XML 3.1A-7x 14500 - Buildlog w pics

[Walterk]

I've been playing with leds for a few years now, and my favorite lights always have been the zoomies:

But the ones from the shops don't go that large.
I built some bigger aspheric zoomies earlier; the Huygens Ultimate, a 250mm (XR-E) 2,1 mcd led lamp, and a 75mm (SST90) with 80kcd.
Usually I get inspired by build-logs or because I want to test how ideas can be combined and applied. Actually I don’t 'need' more then one flashlight.
As you know I like postings to be illustrated, so the pictures are again here on Flickr.


This time I was aiming for a simple, compact and solid light.

Months ago I decided to go with this concept:

Principle

Moving the lens forward/batteryholder backwards, the led turns on, projecting from flood to focussed. The O-ring is to give friction, holding the position without accidentally losing the head.
When the light is stored, the O-ring should seal the inners from moist and dust.


I planned to use 8xAA Nimh and XM-L direct drive, but DrJones pointed me at the AMC7135 combined with protected Li-ion. I adopted his suggestion as he is smarter then me.
AMC7135 for size:

Soldering the AMC7135 was difficult. Luckily I found someone to help me out with that.

Two out of three of these different lenses will fit. Will choose after testing. And hey, the principle can be adopted to fit any size lens and cells.
One is 78mm DX, other is 75mm Thorlabs (preferred so far) and a 75mm Edmunds. I have another lens (from Ebay) but untill I can find it, it is probably also 78mm.

Will be using a XM-L T5 on copper star, powered at 3.1Amp by 9x AMC7135 from 7x14500 AW Protected cells.

The electronics and reed-switch will be housed in one out of 8 cell-bays.
On the front of the batteryholder a PCB will close the circuit from all batteries to the driver. On this PCB there will be a small spring with a magnet to activate the reed-switch.
That will need some testing and tuning to have it aligned properly.
Still thinking of potting the electronics or not. I like it to be durable, but do want the AMC's to be cool.
Led and reed and magnet:

The longest wait so far was in finding a workshop that was affordable. Machining is done, very close to perfect, by using a conventional lathe and a CNC-mill.
As it would act like a piston a part of the aluminium has a longitudinal groove for pressure relief. When the light is 'off' , the O-ring seals the innerds.
The light will be anodized black when all testing is done.

Have to make some adjustments to recess some wiring, enlargeing the relief groove and sand/polish the aluminium to fine-tune the pressure from the O-ring.

Assembly in off/storage position

Assembly in on/focused position (45mm BFL)

This light is now about 1/3th finished. What do you think? Could it work?

 

[nofearek9]

nice project

 

[PCC]

I was going to ask you in the original post when you were conceptualizing this if it was going to be installed in the end of a staff or some other appendage as the end opposite to the lens appears to be made to fit onto something.

Its pretty cool to see this come from concept to reality and am looking forward to seeing it completed.

 

[Walterk]

The problem with zoom lights is that you have to ad a mechanisme. I have solved this in my fanned SST90 diferently using heatpipe.

The void in the back, is to bring outside air closer to the led.
The black Delrin lensholder isolates part of the outer perimeter of the aluminium, not helping convecting heat from the lamp.
To compensate that the alu structure will absorb and transfer the heat to the aft where the alu is exposed to outside air.
I could have put more cells there, but now it is a short path from led to outside air.

This concept (void in the back) can only be one done with number and size of cells smaller then the lens diameter.
It saves weight also. Smalles sizes for this build are following from lensdiameter, focal length and length of cells.

In total it has plenty air surface exposed, but in the back there is way less air passage as it is sheltered to some degree.
The length of the heat path and the mass, might cause a delay in moving the heath away from the led.
It probably will take some minutes before the temperature at the led has stabilized. Time will tell.

 

[Helmut.G]

I like the concept.

I don't think you need to worry about heat issues, there should be plenty of surface for air contact.

Have you thought about using bigger batteries for more runtime? 18500s should fit in your design with the same external dimensions.

 

[Walterk]

Thanx Helmut,

Yes I've considered other cells as well. After many many sketches I decided this was the best configuration where form and function complement each other best. In other combinations either the zoom mechanism or the batteryholder become to dominant in volume, unless you go asymetric (more machining). I tried to keep it simple also to help keep costs down. If you would give me a free card for unlimited machining I can draft you a dream light, even with a 66mm lens. Can't understand why commercial manuafacturers don't value this niche yet. But better lets keep that discussion out of this thread.

Don't let the picture mock you, its 115mm long and 88mm in diameter. I have no small hands but easily get three fingertips inside, and don't do bouldering.
This build fits 76mm lenses with back focal length up to 50mm.

 

[The_Driver]

How is it coming along?

 

[Walterk]

It's on my to do list, but not on top. It jumped a few rows up now...
Had it anodized earlier this year, and have all parts and bits in a box.
Until last weeks it was cold in my workshop.
Want to know how it works out. I won't forget to post.

 

[bibihang]

Is it still at the bottom of your to-do list?