Headlamp modification

[KrisP]

Hi,

I have a cheap 40 LED headlamp sitting around that i'd like to put a Seoul P4 into. The headlamp takes 3AA and has a soft button switch that turns the middle 5 LED's, then another press turns on the next ring and another press turns on the rest of the LED's. If possible, i'd like to keep that function for the replacement Seoul so I can extend the runtime if needed and not blind fellow campers. I'd like to make the first setting 100-200mA, 2nd setting 500mA, and the final setting 1A.

Firstly, if I was just going to run at one setting, say 500mA, and used a current reg to limit that, would I have any issues with the 3 fresh NiMH that might be at 4.5v rather than 3.6v? Or would I need a voltage reg as well?

Secondly, is there any pre-made boards I could just buy and fit to make sure it's going to work OK?

I'm only after flood, so does the Seoul need a reflector? Can I just mount it in place of the old LED's and let it spread it's light everywhere and still have usable light?


Thanks in advance

 

[yellow]

I also have some of these headlamps here, but am not sure on how the switch works.

Maybe its possible to set it up the following:
instead of the three Led "clusters", each "level" goes to one of these drivers:
http://www.dealextreme.com/details.dx/sku.1885
with each next step, another driver is added and adds his power into the already working ones.
Might be possible

Of course each driver is too strong, so has to be modified. Looking at the specs, a single of the black parts there is good for some 350 mAh. And the drivers are cheap. Desoldering 2 of that black parts on each circuit and then mounting three of them, there would be levels: 350, 700, 1040.

If anyone knows what exactly the black things do and know one that would give less current, please tell.

PS: without focusing any led is wasted, try to get some flood part (maybe an optic with some 15-20 deg)

 

[TorchBoy]

I'd basically do it yellow's way, except one 1050mA board will do it all, since the extra two regulators are brought in by shorting out certain points on the board. Very clever. Just put the right switching across those points.

If using no reflector or collimator I'd use a Cree rather than a Seoul because of the uncorrected beam angle - it's tighter with the Cree so (I figure) better for a headlamp flood. Unless you really do want light in all directions; unusual for a headlamp.

 

[TorchBoy]

BTW, I've used an uncorrected (if that's the right term) Cree at about 700mA for caving, and very nice it was.

 

[yellow]

one 1050mA board will do it all, since the extra two regulators are brought in by shorting out certain points on the board. Very clever. Just put the right switching across those points.

great idea

smaller, better, less work needed

 

[KrisP]

Thanks for the replies. Ideally I want an even amount of light in all directions, no focal point at all. I just want to see what it's like then if I don't like it, i'll get a reflector I have already ordered the Seoul too, so if it doesn't suit I will order a Cree.

I've just ordered the 1050mA regulated circuit board, so i'll see how i go with that and modifying it for lower outputs.

Regarding the input voltage being 4.5v on a fresh charge, is this likely to cause any issues with the emitter?

 

[TorchBoy]

Regarding the input voltage being 4.5v on a fresh charge, is this likely to cause any issues with the emitter?

Not if you're running it with a current controlled supply. The regulator will drop the extra 0.9 volts (or whatever it might be).

 

[KrisP]

Looks like i'm good to go when the parts arrive then. Thanks for everyone's help