Lux III Direct Drive?

robk

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I'm rather conservative and always use some resistance in the lights I put together, or use a DC-DC converter with some type of voltage or current regulation. My question is has anyone had catastrophic failures when direct driving a Lux III from 3 NiMH C or D cells (especially when "hot" off the charger)? I normally use 0.5 ohms just to limit the initial current draw to less than 1.2A or so, then it drops as the cells discharge. It seems to be common practice to direct drive the LIII's, but I was just wondering if anyone has run into problems.
Thanks- Rob
 

bucken

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I burnt one up trying to direct-drive one with 9V. It (SV1K) actually ran for about a minute, but the next time I tried to turn it on... it wouldn't. I'm currently running a Blaster Jr. (SV0K) with 6V (2 X 123), but I'm using a 1 ohm resistor to soften the blow. It's run for up to 10 minutes at a time, and the output is spectacular!

Before boosting voltages, I used to run a few Lux III's (SV0K & SV1K) direct-drive from 3 D's, or 3 lithium AA's (Blaster II's & Blaster Jr, with excellent heatsinking). Never had any concerns. When you boost the voltage, however, they become an entirely different light. Try it and you'll never go back.
 

robk

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I've got a FT-3C coming, which I believe is DD off 3 NiMH C cells, but I don't know what bin LIII Wayne is using in these. I have a few SV1J that I'd like to use in DD, but I really don't want to burn them up, or I should say I don't want to hear from the people I sell them to that they burned up. Maybe I should DD my own lights and put a little resistance in the ones I sell!
Rob
 

RussH

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I should be able to get my direct drive 3D mag together this weekend. All that is left is to solder the leads to the Lux3 (a TVOK, iirc) emitter. I plan to use 3 NiMH D cells or 4 NiMH C cells (resistored?) & test for current with various resistances ( .47, 1 ohm on hand). I'd love to see 1 amp or slightly over DD, no resistor. I'd like to find a (3-way?) switch to go from about 700ma to 1100-1200ma. Does anyone know of a small switch that might fit in the MagD, in place of the existing switch? There should be a corresponding SPDT pushbutton switch that I could adapt that would not look clunky. -RussH
 

milkyspit

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I've been direct driving a TV1K emitter in my Blaster Jr. using 2x123 cells. The fresh cells pump about 2A through the thing! That's scary, but I've never seen the angry blue color at all, and so far the light's been working great. I would definitely recommend that you measure your current flow with a DMM before permanently gluing things in place (just for a second so you don't burnout the emitter) to see what kind of current is flowing through your particular emitter. If you're running at more than 1.6A with hot-off-the-charger cells, I'd consider getting an emitter with higher Vf.
 

unnerv

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just wondering if anyone is DD'ing off of 3 alkaline AA's and how badly the light dims due to the alky discharge curve...I am debating whether to use 3AA's DD, or to use 4 and a downboy 1000 for regulation.
 

harebawl

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unnerv,
I am direct driving a TWAK off of 3 AA's and it is just as bright to my eyes as my DD TWAK running off of 3 D's. Run time seems to be quite good as well.
 

milkyspit

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unnerv, I'm not using alkalines for DD at all. However, I'd suggest the 4AA with DB1000 approach. Here's why. AA alkaline cells are considered "dead" when their output drops to roughly 0.8V. With 4AA you'll be able to run your light almost to that point (based on Vf of the emitter), but with 3AA your light will stop working before the batteries are dead. In other words, you won't be able to use the full capacity of the AA cells.
 

unnerv

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hmm, I really like how bright direct drive lights are, but I think that if the drop off is fast, it might not be brighter than a db 1000 for long anyway. Run time is not a huge concern as this is more of a project light that will probably not see much real world use (like most of my lights...we have not had a power outage at home durning the night, and work has backup deisel generators.) I mostly only get to play around with them. Maybe I'll try some lithium AA's since they have a flatter discharge. The reason I keep pursuing the 3 cell is that I have one of those EL 3 to D converters begging to be used.

Thanks for the input guys.
 

harebawl

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Unnerv,
I'm no expert and do not have any regulated lights, but I have used my DD 3AA on and off for about a month now, I'd say guessing 2 to 4 hours runtime on it and it's still brighter than heck! I love these Luxeons! My 3D DD has had the same batteries in it now for atleast 3 months now and same thing nice and bright and always white! My resistored lights always got over 10-15 hrs. run time before I finally changed batteries and they weren't even dead and still pretty bright! I know you might be able to do a little better with a regulator, but, with this kind of high output runtime for a light that won't get tons of real world use go DD! I use mine all the time and regardless of what I am getting for run time it is many times better than incandescent and best of all always white!

All this fun off three little AA's....You can't beat it!
 
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