Tips for Building Direct Drive?

I have never tried a DD light before. For 3x123 and a 5w emitter (say a U3U, since those are pretty commonly available), do I need a resistor? If so, is it really "direct" drive at that point? How much overdrive can a 5w take? Do I need to test the emitter before hooking it up? Anythng else I should look out for?

Thank.

#1 . . . . .HEATSINK!!!!!!

#2 . . . . .If you have resistance, it's not DD. /ubbthreads/images/graemlins/smile.gif

Direct Driving an LS can be a tricky and/or damaging process. If you have proper heatsinking, then running at 9V should be no problem unless your LS has an unusually low Vf. My suggestion to you, is that you use a 5 Watt .5 Ohm resistor. Believe me when I say that 9 volts plus a .5 ohm resistor is still freakishly bright.

Ditto re per above posts... heatsinking for DD is most crucial! Other than that, you should have no problems /ubbthreads/images/graemlins/smile.gif

Same as above,,, heatsink!!!
If you have a nive heatsink,, similar to the hotlips, you shouldn't have a problem with DD with 9V.
Just pick yourself a nice 5W'er. /ubbthreads/images/graemlins/smile.gif

I'm wondering if the McLux head is enough of a heatsink... my PM6 gets hot *really* fast and it seems like it has even more mass to sink heat with.

From experience, I can tell you NOT to use a Makita 9volt (actual 10.6v) drill battery, that is, unless you are attempting "flash photography"

I have heard of others using mclux's for 5w.
I plan to alittle later.
As long as the light stabelizes itself, and doesnt go above the led's operating temp.
Those "flutes" ? on the mclux should help.

The biggest tip: Heatsink...

The better your heat dispersion, the better overall, period. I have a McLux head that houses a 5Wer with a McFlood, and it gets HOT HOT HOT! It's awesome as an intermediate floodlight, but I wouldn't use it continuously for long periods of time. The PM6 does an excellent job of housing a 5Wer and dispersing the heat in a great manner, but so far, it's the only pocketable size light I've seen that is acceptable in housing a 5W mod...

Use a resistor like 0.5 ohms, or wire it with #32 wire to put some resistance in the circuit. The *tiny* bit of brightness you'll lose will be turned into extended runtime and extended LED life. Just my opinion, I am totally against DD, it stresses the device beyond design parameters. I really prefer some type of voltage or current regulation for constant brightness for a predictable amount of time.
Rob

Heatsinking is the obvious #1 answer, so I'll add something else - Check your current flow with a good quality DVOM, that so KNOW how much hard that Luxeon is being driven..

And there's no shame in using a resistor if you have an emitter that wants to "run away". Save your "runaways" for direct drive UNDERdriven mods since those will usually make good light.

I know that anything above 700ma when driving a 1W produces no more brightness and is just wasted as heat. Is this the same value for a 5W?

Curious,

Eric

Eric,

from what I understand, a 5w is actually four 1w emitters wired together as two parallel sets of two emitters in series. In that case, given your 700ma "cut-off", you should be able to go to 1400ma on a 5w before seeing the same thing. That's kinda scary, we're talking over 10 watts at that point. Someone here will correct me if I'm off base, I'm sure.

So, for a 3 - CR123, 9 volt 5W LED mod you'd need a 1.43 ohm, 2.8 watt resistor to limit the current at 1400 ma.

Thanks Tyler,

Eric

Does Mr. Bulks SNII have a resistor?
If so, what is it?

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jtice said:
Does Mr. Bulks SNII have a resistor?
If so, what is it?

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I'm fairly sure Mr. Bulk's SNII's don't use any resistance at all; they are literally direct drive.

By contrast, the Elektrolumens Blaster VI uses a half-ohm (0.5 ohms) resistor. I own both, and the SNII is clearly brighter than the Blaster VI, though I think a good part of the difference is due to Mr. Bulk's light using a higher-end 5-watter; in fact, he's developed a reputation around here for consistently getting his hands on some excellent emitters for his creations.

That and the light focusing methods are different. Blaster V/VI is a broad beam, SNII is tight spot. I'd definatly test your current your pulling through your 5w. I'd keep it around 1.5amps with fresh batts.

I currently run my low Vf V2T DD PM6 module conservatively with one 1400 mAh Li-Ion plus one 1400 mAh 123. These drive it at about or somewhat above 700 mA. It runs much cooler than with 3 @ 123's or 2 @ Li-Ions.

My HyperLux V is a DD light with a W4W. This high vF light runs bright and cool with 3 * 123.

My reconfigured NexNeedle with a V2T will probably also be run with one CR123 plus one Li-Ion.

My SpaceNeedle II 2D is aparently a higher Vf Luxeon, but it probably isn't as high as the W of the HyperLux V. Its brightness increase when moving from 1 li-Ion plus 1 123 to 3 * 123 seems to be more pronounced than that of the V2T. I will shortly have 3AA to D adapters from Elektrolumens to go along with the 4AA to D adapters I just received from Chief Wiggum.

Tonight I'll try various chemistries of 5 or 6 AA's in the Space Needle.

My other 5 Watters are regulated so I don't have to worry..

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IsaacHayes said:
That and the light focusing methods are different. Blaster V/VI is a broad beam, SNII is tight spot. I'd definatly test your current your pulling through your 5w. I'd keep it around 1.5amps with fresh batts.

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Hey Chef, /ubbthreads/images/graemlins/smile.gif funny you should mention the focus thing. Last night we had some seriously thick fog outside, and I took a bunch of lights with me on the back porch to compare their beams. In the fog you could literally see the entire beam as if drawn into a comic strip! /ubbthreads/images/graemlins/cool.gif

The Blaster VI was the classical flashlight beam, straight lines gradually extending from the head of the flashlight, except that it was the biggest, fattest beam I've ever seen! Not a flood, mind you; more like a classic flashlight beam that had done way too many steroids. /ubbthreads/images/graemlins/grinser2.gif The Space Needle II was a combination of a straight "light saber" beam with lots of spill around it.

As for brightness, I compare my lights by going into a totally dark room in my home with a light in either hand, aiming both generally at the far corner of the room, and doing a simple A-B test. Even with the beam differences, it's clear that the Space Needle II is the brighter light. I believe that's partially due to the resistor in the Blaster VI (and lack of one in the SNII) and partially due to a terrific emitter in the SNII. Mind you, I love both lights, perhaps the Blaster VI even more than the SNII due to a well-balanced, overall great package.

Recently, my SNII with fresh but not just-out-of-the-box batteries measured 1.1A.

[ QUOTE ]
lemlux said:
I currently run my low Vf V2T DD PM6 module conservatively with one 1400 mAh Li-Ion plus one 1400 mAh 123. These drive it at about or somewhat above 700 mA. It runs much cooler than with 3 @ 123's or 2 @ Li-Ions.

(snip)


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lemlux: With all the cautionary tales about not mixing battery chemistries, is it advisable to combine a Li-Ion cell with a CR123A, and what are the potential risks, if any, of such a combination? I'm interested in your thoughts and experiences, because it does sound like a reasonable option.