4 NiMh, 1 Luxeon, and 4 ohms = POP???

I want to power a LS from 4 NiMh AAs. I found a bunch of 2ohm 10 watt resistors to use. At 6 ohms, I get 3.17 volts and 300ma draw. Am I going to get an unfortunate POP if I try 4 ohms? I want to overdrive a little...

1w's are rated at 350mA. So... should be no problems using 4R

Ok...that gives me 400ma @ 3.2 volts. Dare I try 2 ohms?

Make sure it's on a good heat sink. Bet you it works but don't run it too long.

Yeah, it's on a chunk of aluminum. I'll measure the current and decide if I want to keep it that way, but you don't think it will pop @ 2 ohms?

Part of the fun is in the experimentation /ubbthreads/images/graemlins/smile.gif
Report what you find and we can all benefit from your experience.
Remember those Physics practicals at school? Aim, procedure, result and recommendation /ubbthreads/images/graemlins/smile.gif /ubbthreads/images/graemlins/smile.gif

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hotbeam said:
Part of the fun is in the experimentation /ubbthreads/images/graemlins/smile.gif
Report what you find and we can all benefit from your experience.
Remember those Physics practicals at school? Aim, procedure, result and recommendation /ubbthreads/images/graemlins/smile.gif /ubbthreads/images/graemlins/smile.gif

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But what if I smoke my precious luxeon!!!?!??? /ubbthreads/images/graemlins/ooo.gif /ubbthreads/images/graemlins/crazy.gif

Eh it's only a 1 watter. I, as well as many others, have damaged some much pricier 5W's, including some V and W binned ones. /ubbthreads/images/graemlins/help.gif

Alright...I couldn't resist. /ubbthreads/images/graemlins/naughty.gif 700ma and now I feel like I've been welding without a mask. /ubbthreads/images/graemlins/crazy.gif I think I'll go back to 4 ohm... /ubbthreads/images/graemlins/smirk.gif

zmoz,
Just run 6 of the resistors in series-parallel (three of them in series for each string, then connect the strings in parallel) That will give you three ohms. Figure somewhere around 550mA which is fine (BB500 regulator boards sell quite well) Another trick is to take a file to the 2ohm resistors and keep grinding them down until they hit 3 ohms (or 3.2 or...) One resistor that is "adjustable"...it is a 10 ohm resistor so go for it! /ubbthreads/images/graemlins/thumbsup.gif /ubbthreads/images/graemlins/grin.gif

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BentHeadTX said:
zmoz,
Just run 6 of the resistors in series-parallel (three of them in series for each string, then connect the strings in parallel) That will give you three ohms. Figure somewhere around 550mA which is fine (BB500 regulator boards sell quite well) Another trick is to take a file to the 2ohm resistors and keep grinding them down until they hit 3 ohms (or 3.2 or...) One resistor that is "adjustable"...it is a 10 ohm resistor so go for it! /ubbthreads/images/graemlins/thumbsup.gif /ubbthreads/images/graemlins/grin.gif

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Problem is I've only got 4 resistors...and they are big 10 watt'ers inside a big chunk of ceramic. I coulda swore I've got some 1 ohm's around here somewhere...

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zmoz said:
Ok...that gives me 400ma @ 3.2 volts. Dare I try 2 ohms?

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I run 1000ma all the time in my Mr. Bulk LGI /ubbthreads/images/graemlins/grin.gif The LGI uses 3 AA's (I use NiMH.) I added about 0.3 ohms of resistance to drop the current down to 1000ma! I've been using this light well over 6 months with no ill effects (to the LS - I still keep seeing spots after looking at it /ubbthreads/images/graemlins/ooo.gif )

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trailstoride said:
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zmoz said:
Ok...that gives me 400ma @ 3.2 volts. Dare I try 2 ohms?

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I run 1000ma all the time in my Mr. Bulk LGI /ubbthreads/images/graemlins/grin.gif The LGI uses 3 AA's (I use NiMH.) I added about 0.3 ohms of resistance to drop the current down to 1000ma! I've been using this light well over 6 months with no ill effects (to the LS - I still keep seeing spots after looking at it /ubbthreads/images/graemlins/ooo.gif )

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It runs at 1amp from 3 AAs with resistance? I could only get 600 direct driving from 3 NiMh...

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zmoz said:
It runs at 1amp from 3 AAs with resistance? I could only get 600 direct driving from 3 NiMh...

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Yes, 1Amp with resistance! Mr. Bulk was not sure the LGI could take NiMH with direct drive - so I measured first and was shocked at the 1500ma reading /ubbthreads/images/graemlins/crazy.gif I was afraid the LS would go *POOF* at any time! I've used this light to walk the dogs a dusk/night. I would guess I've put over 75 hours on this LGI so far.

zmoz,

Remember to take forward voltage into account. That can make a world of difference. That's why a *proper* way to drive a Luxeon is with constant current which removes Vf from the variability. That particular LGI LED probably has a Vf much less than the one you got.

Check out Wayne Y.'s sandwiches. The MadMax+ will put well over 1A throught the LS with new batteries. /ubbthreads/images/graemlins/huh.gif I haven't heard of any reports of problems. The MM+ with a Q3L is quite brite and white, but I hear the new R2H with the MM+ is incredible! /ubbthreads/images/graemlins/drool.gif I can't wait to put the R2H into mine... /ubbthreads/images/graemlins/popcorn.gif