Head Light mod - suggestions wellcomed (pics)

Hallo.

I have bougt a cheap head light yesterday. It costed me about $9. Bought with the intention to mod it with led.
It has following specs:
- 4x AA in series
- krypton 4.8 V/0.7A bulb
- weather proof (some o-rings)
- plastic housing
- plastic lens and reflector, permanently mounted in the bezel
- focusable

here are some pics:
light:


battery compartment:



Inner size of the light is 54 mm / 2.1 inch.
Reflector hole is 13.5 mm / 0.53 inch.
Light bulb is moved by the black knob back and forth.

Picture of disassembled mechanism:




I would like to preserve the focusing ability. The first idea was to mount a kind of aluminium heatsink and 1w or 3w luxeon on the focusing mechanism. Some questions came in my mind then:
1/ If the heatsink will be locked in the light wont it lock the heat inside as well? I do not want to drill holes to spoil the watterproofnes. Does not the heat from the heatsink melt the plastic material of the housing?
2/ Is the luxeon the right emitter because of high consumption? I would like to be able to run the light for few hours (3-5) but also want bright light. Cluster of leds is not focusable and I would not be able to use the reflector.
3/ If luxeon is OK, I can rewire the battery to make 2-2 AA in paralel and use some boost circuit or let the cells in series and use some buck circuit. Which would be better for runtime/brightnes?

My intention is to use the modified light when exploring some caves.

Thanks for your ideas/suggestions.

I would suggest 6V plus a buck regulator or 4.5V (with a dummy cell) resistored DD. Get the best Luxeon III you can find (brightest, lowest Vf, but not necessarily the whitest for any practical use). For cave exploration, the driving current doesn't have to be super high, something like 200mA would be bright enough already. That will give you longer run time, which is more important for cavers. You may want to try both high dome and side emitter and see which one works better with your reflector and your needs. The typical result is a side emitter gives a tighter beam with throw, but a HD gives better balance between the side spill and the hotspot.

Thank you for your suggestion.
I have got an TVOJ from Klaus. Do not have any side emitters around. Do you think DownBoy adjusted to 200 mA will be OK? How about thermal isues inside the light?

cosco, i think you would need heatsink real bad. proper heatsink with 200 mA *might* let you get away by insulating the inside with the outside.
usually buck is more efficient than boost, so rather than wiring the battery and using BB, i think DB is a more viable solution. 200 mA maybe good enough, but i am not expert in this thing. I think the allowed time for you to run the light continously all depends on how much heatsink you can fit into the light. it is all give and take situation. more heatsink, heavier the light becomes but safer to the lux.
I agree of led ASAP to try which one suits you better, the HD or SE. If you prefer overall light output, you might want to try LD also.
I think for this kind of application, lux 1W or 3W does not even matter. get one that has the lowest Vf, because that means lower heat.

Take it back, and get one with a 2aa, or 2c/d cell and pr flashlight bulb, or a 3-4 cell design with lots of metal contacting the bulb flange and the pr bulb.
Try to find one with a stippled, or orange peel textured reflector.
Then put a white Everled in it from www.ledsupply.com
They have other colors, but the white one has had the most r&d put into it.
Check out this thread.

Thanks to everyone. I am going to tweak with this for a while. I know I can buy better headlight even with led already for more money but where would be the fun then? I am not planning some heavy caveing so my life wont depend on this light. I plan to use it also when diging out some semiprecious stones and this will be open air activity.
Do not have any luxeon with Vf better then J.
I will apreciate more input and will post my results.

The heat-sink issue is not as bad as it seems. You can use a heat sink inside to mount the LED, then use a bolt through the case to connect a radiator type heat sink from an old 486 CPU mounted outside the case.

If you are running at only 200ma, you might want to use a 1 watt led. My experiments have T binned LuxIII at 350ma is comparable to a Q binned 1 watt. If you snag an 'R' you should get more light per watt of battery power.

You should also consider using a two stage switch to conserve battery power when you need or want to. A pair of AA batteries will power a lux at 75 ma for a looooong time. You may not need full power when in close quarters. Lumileds says you do not need to use a heat sink at 100ma or less.

A two stage switch is as simple as a SPDT with a resistor connected between the battery and the electronics.


Daniel

gadget Lover, was your experience with K binned lux III's? Im thinking a TVOJ would be very bright! that LED would have super low Vf at low ma, but if your going to current regulate it, the story might change vs DD..

i have the same rayovac here.
i gutted the focusing mech and installed a copper plate with a q3 hd on it.put a charging jack in the batt pack in one of the center slots.
now it uses 3 aa nimh cells.
running 350 ma no problem.has a nx01 ca'd to the black part of the lux.
was a open package deal missing the bulb for a buck at a local store.perfect modding fodder.

Yes,Justintoxicated, I was using a TV1K. A 'J' should be more efficient than a 'K', but an R should beat either at 350ma.

Daniel