why multiple LEDs?

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wle
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why multiple LEDs?

I don’t remember this being asked, so I will:

What is the advantage to multiple LEDs in a light?

I have an FW3A and, to me, it doesn’t seem like it would need 3 LEDs.

Why do you think the designer decided on 3?

Is it more efficient somehow, lumens per watt?

Is it a matter of heat?

IE, it runs longer before getting too hot?

Or maybe the LEDs stay cooler so they last longer?

Does that solve some problem with the driver – like maybe 3 separate ones are cheaper than 1 that can handle the max current of an 18650?
I could see it if the battery could produce 25-30 amps, but this one can’t.

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Edited by: wle on 07/29/2021 - 16:46
alpg88
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yes there are advantages, more could be packed in smaller space, leds do run cooler at lower current as well as more efficiently,

zoulas
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Good question. Part marketing, part engineering. Mostly marketing.

It’s the quest for more lumens. Lumens sells lights. Like megapixels sells cameras.

wle
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zoulas wrote:
Good question. Part marketing, part engineering. Mostly marketing.

It’s the quest for more lumens. Lumens sells lights. Like megapixels sells cameras.

that;s one of my questions, do they really make more lumens?

with just one 18650, wouldn;t 1 led handle all the battery current and make all the lumens possible?

"You never have the wind with you - it's either against you, or you're having a good day."
    Daniel Behrman, "The Man Who Loved Bicycles".
It never gets easy, you just go faster.   
-Greg Lemond.
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thefreeman
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One at 3A = 720lm at 73lm/W

Three at 1A = 921lm at 105lm/W

So yes, it’s significantly more efficient (and here it’s just at 3A), more output, less heat, takes longer time to heat, probably last longer too though I don’t know if with flashlight usage it really matters.

BTW an XHP50 or 70 (and others) is 4 LEDs in one package, higher max output and higher efficiency.

Firelight2
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Why multiple LEDs:

  • More Efficient – the general rule is the more light emitting surface area you have, the more lumens you get. LEDs are more efficient when run at lower intensity.

As a general rule, large emitters produce more overall light (lumens), even though the intensity (light produced per square mm) might be a lot lower than smaller emitters. A large emitter like XHP 70 produces more light than a small emitter like Oslon White 1. This is also why multiple emitters produce more light than single emitters.

On the other hand, for throw (lux), intensity is what counts. The more intense a light source the easier it is to focus with an optic or reflector and the more throw you get.

The result is that high-lumen lights or close-range flood lights tend to have multiple emitters for maximum lumens. But long-range throwers tend only to have a single emitter and a large optic or reflector.

On a fresh VTC6 18650 cell, a flashlight with a single XPL HI emitter might output 1600 lumens. Put the same cell in a light with 3 emitters and it now outputs around 3000 lumens. And in a light with 8 emitters like the Emisar DT8 you might get over 5000 lumens.

The extra light from multiple emitters creates a broader hotspot than a single-emitter thrower. This makes multiple emitter lights especially good for close and medium range use when you want to see a large area. For long-distance use a thrower with a concetrated hotspot works much better.

  • Marketing – Lumens sell. A purchaser is much more likely to buy a light that can output 3000 lumens rather than the one that outputs just 1000 lumens. After all, the 3000 lumen light is more powerful.
  • Compactness – Using multiple emitters can result in a shorter, more compact light than a single-emitter. This is because single-emitter optics tend to be longer than the same diameter optic designed for multiple emitters. This may be one reason why multiple emitters were chosen for lights like the FW3A and FWAA.
wle
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thefreeman wrote:

One at 3A = 720lm at 73lm/W

Three at 1A = 921lm at 105lm/W

So yes, it’s significantly more efficient (and here it’s just at 3A), more output, less heat, takes longer time to heat, probably last longer too though I don’t know if with flashlight usage it really matters.

BTW an XHP50 or 70 (and others) is 4 LEDs in one package, higher max output and higher efficiency.

ok thanks, that sounds like the main reason!

wle

"You never have the wind with you - it's either against you, or you're having a good day."
    Daniel Behrman, "The Man Who Loved Bicycles".
It never gets easy, you just go faster.   
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Multiple emitters allow higher turbo in a 3V LED with compact drivers. I think that would be the main advantage in the FW3A. It will be more efficient but a good buck driver would be a more cost effective way of increasing the efficiency (with a low Vf LED), but maybe it wouldn’t be as compact and off-the-shelf firmware availability may be lower. Multiple emitters result in a floody patten but you can do the same with a single emitter.

puglife2
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So 3x SBT90.2 will be more efficient than one?

CollectEverything
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This actually ties in well with a question I had.

The Emisar DT8 has 8 emitters, double that of the D4V2. The D4V2 can theoretically hit 1200 lumens with E21A emitters (probably the 5000k ones) but the DT8 only claims to output 1800 lumens maximum. Why would 4 extra emitters only increase the output by 600 lumens?

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thefreeman
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7.5A driver instead of 5A. Their numbers are probably just estimated and not measured.

CollectEverything
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thefreeman wrote:
7.5A driver instead of 5A. Their numbers are probably just estimated and not measured.
Oh right I guess they aren’t using double the current. The DT8 page claims 9A though where does the 7.5A come from?

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BurningPlayd0h
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CollectEverything wrote:
thefreeman wrote:
7.5A driver instead of 5A. Their numbers are probably just estimated and not measured.
Oh right I guess they aren’t using double the current. The DT8 page claims 9A though where does the 7.5A come from?

AFAIK the DT8 is using the 9A CC driver. With the E21As specifically though, there is limited room for more output with the amperage they’re being run at in both lights – you’re already in “diminishing returns” territory.

Emisar-Noctigon previously only had 5A and 7.5A versions of the CC driver, I think the 9A version came out with the K9.3.

richbuff
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More lumens.

 

But less throw per head diameter. One 90.2 in an MF05 is great, but four 90.2 in BLF GT94 yields more lumens.

Rev 22:15

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…quad – triple led in series and boost driver ….

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Multiple LEDs also provide more flood lighting at a greater distance. Using the Convoy S12 with 3x LEDs you get less throw and more flood, and using the S16 (S12’s single LED version) you get less flood and much more throw.

It’s not just about efficiency and more lumens

Texas Ace Lumen Tube calibrated with maukka lights

New Zealand store – https://www.piercingthedarkness.co.nz (NZ customers only)

YouTube channel – https://www.youtube.com/channel/UCIUWi2vYp4CWrRkOJM70t_w/videos (Demos for my customers, and reviews)

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Back in the day when I built my first triple for a single cell light I didn’t have any single 3V LEDs that could handle around 12 amps. If I applied direct drive to them they fried. They would fry at a bit over 5 amps. The triple I built pulled about 12 amps, roughly 4 amps per emitter. Those emitters are still alive… So, if you wanted more light, what would you have chosen? A single emitter at 4 amps, or 3 emitters at 4 amps each?

Maybe now there are many 3V LEDs that can handle +12 amps to choose from, but historically I would say that triples and quads came around because the common LEDs simply could not handle much current.

thefreeman
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CollectEverything wrote:
thefreeman wrote:
7.5A driver instead of 5A. Their numbers are probably just estimated and not measured.
Oh right I guess they aren’t using double the current. The DT8 page claims 9A though where does the 7.5A come from?

Yes you’re right, no idea how they come up with 1800 then.

Dalamar
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ggf31416 wrote:
Multiple emitters allow higher turbo in a 3V LED with compact drivers. I think that would be the main advantage in the FW3A. It will be more efficient but a good buck driver would be a more cost effective way of increasing the efficiency (with a low Vf LED), but maybe it wouldn’t be as compact and off-the-shelf firmware availability may be lower. Multiple emitters result in a floody patten but you can do the same with a single emitter.

nothing stopping you from buck driver and multi-led doubling up on efficiency, it’s why I only buy Fireflies now.
Not many other lights can put out constant high cri 1000 lumens til the battery dies, and if these had more surface area it would be higher yet

I only like high CRI. Collection:

Fireflies NOV-MU 21 4500k E21A

Fireflies ROT66 219B SW45 D220

Fireflies E07 Copper 219B SW45k? (odd/higher lumen bin with lower r9 and higher cct?)

Fireflies E07 219B SW45k

Fireflies E07x Pro sst20 FA4 4000k 

 

Varmint removal:

Convoy M21A C8 ver SST20 4000k (5a)

Convoy S2+ SST20 4000k  FB4 (3200ma)

Memes:

BLF GT94

Emisar D18 660nm SST20 

 

 

CRI test dump https://drive.google.com/drive/folders/1kcl_uOhgfpR4RSsa8F4b-UUVP9mkL6Cr...

Funtastic
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Dalamar wrote:
it’s why I only buy Fireflies now. Not many other lights can put out constant high cri 1000 lumens til the battery dies, and if these had more surface area it would be higher yet

Fireflies are great when you get a working one. Is their QC still bad?

I used to be a dealer for them until I had enough of the many issues over every single model.

Texas Ace Lumen Tube calibrated with maukka lights

New Zealand store – https://www.piercingthedarkness.co.nz (NZ customers only)

YouTube channel – https://www.youtube.com/channel/UCIUWi2vYp4CWrRkOJM70t_w/videos (Demos for my customers, and reviews)

Dalamar
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Funtastic wrote:
Dalamar wrote:
it’s why I only buy Fireflies now. Not many other lights can put out constant high cri 1000 lumens til the battery dies, and if these had more surface area it would be higher yet

Fireflies are great when you get a working one. Is their QC still bad?

I used to be a dealer for them until I had enough of the many issues over every single model.


Sounds like it, but I personally haven’t had a problem that wasn’t cosmetic.
Worst problem I had was actually with Emisar (threads), but that was still cosmetic.

Both brands end up needing sanding to soften edges, and again, Emisar was worse in that regard (ridges in d18 were way worse than a rot66, scuffing up battery sleeves something awful).

I only like high CRI. Collection:

Fireflies NOV-MU 21 4500k E21A

Fireflies ROT66 219B SW45 D220

Fireflies E07 Copper 219B SW45k? (odd/higher lumen bin with lower r9 and higher cct?)

Fireflies E07 219B SW45k

Fireflies E07x Pro sst20 FA4 4000k 

 

Varmint removal:

Convoy M21A C8 ver SST20 4000k (5a)

Convoy S2+ SST20 4000k  FB4 (3200ma)

Memes:

BLF GT94

Emisar D18 660nm SST20 

 

 

CRI test dump https://drive.google.com/drive/folders/1kcl_uOhgfpR4RSsa8F4b-UUVP9mkL6Cr...