Lux V...What resistor values for regulated control

I have all the parts ordered to make my first mod.. I was gonna use 3x123 and direct drive a LuxV but I have heard conflicting reports about this... Some say it works fine.. other say it needs regulation..
So.. what value resistors would help me to limit the drive current to a mod like this and still get WOW BRIGHTNESS? I didn't want to buy a regulator board (I'm getting on the wife's bad side with the empting of checking account) I can attach the resistor(s) to the heatsink for temp control...

Please advise

Skillet here.... and thanks CPF for opening my eyes... /ubbthreads/images/graemlins/help.gif

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skillet said:

Please advise



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This is easy, *avoid DD*. For a lot of reasons. For sure what you suggest is a very likely route to a dead LED. Bright for sure, but short.

Something like 2.5 ohms (two watts) should be a good starting point. Try it, and *measure* the current and adjust accordingly.

IMO, you should at least invest in a DMM ($3 for the cheap ones) and use it. It's mighty cheap insurance.

Doug Owen

Re: Lux V...What resistor values for regulated con

Thanks Owen...
What amount of current draw should I be trying to achieve for optimal output and what amount of voltage drop?
. I have a fluke meter and know how to use it.


Thanks... Skillet /ubbthreads/images/graemlins/crazy.gif

Re: Lux V...What resistor values for regulated con

It should read about 800-1000 milliamps on fresh batteries.
600-700 on partly used ones.
Good luck on that. /ubbthreads/images/graemlins/wink.gif

Re: Lux V...What resistor values for regulated con

As 3rd Shift suggests, 700 mA is spec., a good target. I would not, however, expect that much drop with Li cells, a 10% drop maybe but not 30%. It'll be interesting to 'see' what you get.

Voltage drop at that (or any other current) is a function of bins, but 7.2 Volts is probably a good estimate.

Those are the numbers I used when suggesting 2.5 Ohms at two (or more) Watts as a starting point. BTW, you might use four ten Ohm, half Watt resistors in parallel. Easier to find and fit than a 2.5.....

Doug Owen

Hi - I have some 2 ohm, 1206 size (3mm x 1.6 mm wide) resistors with plenty of power range to spare. I had these custom made specifically to meet this kind of requirement, as well as the other common setup - 2 x 123 with a Lux III.

They definitely need to be heat sinked to work. These are surface mount style, about the size of the end lead of your Luxeon V. It requires a bit of skill to solder something this small, as others will attest. I personnally do not have this skill, and drink way to much coffee, so I use silver filled epoxy instead.

If you are interested, send me a pm.