Resistor mod on LD-29 driver

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tekwyzrd
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comfychair wrote:

But not all buck controllers will do higher than ~4v output, no matter the input voltage. The LD-29 used to have that limitation. Have recent versions been changed?

I suspect this limitation would be present in the older version used in the L5. Can anyone confirm?

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Buck drivers also have overhead, meaning that a certain voltage above emitter Vf is needed to remain in regulation. Often around a volt so that 6V emitter might need 7V from the cells to maintain full output.

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Mmm…

 

Just saw this:

1st version LD-29 (?) review at lygte-info.dk

Which differs from: LD-29 at FT

Newer LD-29 review at lygte-info.dk

 

Some of you may have one of those at hand; could you measure the no-load output voltage of this newer version while powering it up with 2S li-ion voltage range? Well, just feed it with 8 or 9V for the sake of simplicity. I'd like to make sure it can drive 2S2P XHPs before breaking the bank…

 

Cheers Party

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tekwyzrd
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@Barkuti 404 error for the lygte-info pages. Tried to do the links myself and got 404 again. For some reason extra text is being inserted breaking the link. Here's the page with the "list of driver reviews":http://lygte-info.dk/info/indexLedDrivers%20UK.html

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tekwyzrd wrote:
@Barkuti 404 error for the lygte-info pages. Tried to do the links myself and got 404 again. For some reason extra text is being inserted breaking the link. Here’s the page with the list of driver reviews

Seems the Simple Post Editor chokes with those %n code character substitutions. Re-edited the thing on the advanced one (pain in the arse as it is now, everything has to be reworked). Sick

Cheers

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From what I see on the LD-29’s photographs, the shunt resistor size seems to be “1206” imperial units, or about 3’2×1’6mm according to the size tables I’ve found (should be 3’048×1’524mm).
May someone confirm?

If that is the case, I see it as a somewhat poor choice from a design standpoint because rated power for that footprint is ¼W (doesn’t it?) and that thing has to dissipate around 0’196W in a usually hot environment: no thermal derating headroom as I previously said.

Cheers fellas Crown

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Well.

Desoldering that R025 and putting there a stack of three ¼W R047’s: around 0’0156͡7Ω for a maximum of nearly 4’47A. Maybe 4A at the emitter if other losses are kept within range. Adequate thermal headroom for the resistors: ≈0’104ish watts per unit, at most.
XHP50 or XHP70? I know the XHP50 will outthrow the XHP70 at the same current but, do these handle the extra power well?
All right, enough for now. Smile

Cheers

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Will the current-version LD-29 power a ~6v LED?

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comfychair wrote:

Will the current-version LD-29 power a ~6v LED?

Hope so, let’s see if someone can make a quick test on this (HKJ?).
Bummer if not, because my host pillhole ∅ is 20mm and that driver is efficient and well priced.

Cheers Smile

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comfychair
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Like I said, unless it's now using a different buck controller, it's limited to ~4v output voltage no matter what the input V or resistor pack is. LD-29 has had that limitation since forever.

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Hello!

Mmm… six months later!

Well, I've seen some light over my duties in general. I somewhat ventured with the driver mentioned in the previous post but, I've finally come to conclude it wasn't going to work properly with a 2S emitter.

There is a new version of the LD-29 family, this LD-29S available at Kaidomain. I've been evaluating it against this FX-6 driver also (@KD too). The latter FX-6 seems better suited for a 2S high amps emitter application because of its big wire coil gauge, albeit it uses a much higher sense voltage than the LD-29S (≈0'225V vs 0'06V) which means it shall go out of regulation earlier than the LD-29S if we are to optimize the LD-29S' weak spot: the inductor. And it happens that I have such an inductor, some R050s and some R100s; what is more, please notice the good looking SS10P4 (10A) schottky onboard the LD-29S… 

 

Cheers Party

Please avoid fully quoting lenghty posts, namely with nested quotes. Trim quotes down to the essential. Helps with neatness and legibility. Thanks.

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I do not own yet. 1. How hard is it to get to the resistor, and to replace? How small are these components (and solder joints) are we talking? 2. Anyone photo or video the modification?

I haven’t done the math on paper, yet. But.. My goal would be to replace with a .2 (or so) ohm resistor, lower current to 350, then compare the lux with the same fully charged 18650, against, these (at tail cap 350): amc7135 single, 2.4 amc board pwm to 350, and simple dd resistor to 350 ma. In theory, in a 202 lpw@350ma, this buck should be brightest, followed by the resistor dd, followed by/or equalling the amc7135, followed by the led getting slammed at 2.4 amps with amc7135*6 (for a whooping 100lpw strobed pwm with a fwV of 3.2V or more).

Runtime=Usefulness

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