How far can you overdrive a small LED?

I know that people routinely overdrive high-amperage LED lights. I could probably figure out what levels and heatsinks are appropiate for those easily.

What about smaller lights? Specifically, I'm looking at a 3.3-3.4 volt, 20ma reccomended, 26ma maximum light. (8mm)

I'm running it at about 25ma right about now, and I'd REALLY like to increase its power levels.

what's the likely relationship between lifespan and overdrive? between overdrive and brightness? how big does the heatsink need to be?

I ran a quick search on the forums, but that all seemed focused on larger lights,

also posting this in custom and modified.

Your question is difficult to answer without knowing more about your specific led.
Depending on the manufacturer, overdrive could range from none to several times the nominal rating.

Here is a link to a thread that has some great overdrive versus lifespan info on a number of different leds from different manufacturers.

teany bit over spec, anything more than that, and it starts going downhill fast.
a 8MM does have more capacity for heat dissipation.
Cheap leds die quicker than well built ones. brands count.

5mm already have what i concider a short life, compared to high powered leds.

Get the heat off the LEGs to improve things.

if your using 8mm leds, that are single gate leds, check out the parellel gate 8mm leds, they have 4x20ma gates, 4 times the output. while they will certannly burn out over spec faster, and need thier little legs heat synced, putting 50-100ma carefully into them, would be a vast improvement over what you got.

if you have a high power 8mm led some are SPECed for 100ma, or improperly speced, so if it is a higher powered 8mm, you could probably crank it up a bit.

in all science that i use your heat sync should be as big as whatever takes the heat off what your trying to get the heat off of
basically that means you need a few extras, so you can put a sinc on it, overheat it and see if it works. if the first few are still alive after a torture test, then it must work for an 8mm 4x die 100ma, a penny would be nice.

its a bit like your cpu, your cpu will fail miserably at 60-70*c , but psycos get the thing to be at 32*c , so how big is NESSISARY? none when driven at spec. none if the temps comming down the legs arent hot to a touch. none if you cant dissipate that heat, TO somewhere.
but if your like a computer geek that wants 50* below 0, then it the better it is , the better it will be

very usefull, thank you.

The specific LED is a superbrightled rl8-w110-360

11 lumen white light (blue with outer coating to emit white) it emits in 360 degrees

http://www.superbrightleds.com/specs/w110-360_specs.htm

i don't BELIEVE they build their own lights, but I can't confirm or deny that based on their site, and there's no word on who their producer might be,

I would be a little suspicious of those specs.

They are claiming 11 lumens at 20mA drive current with a Vf of 3.2V.

That's 11 lumens at 64mW. This figure would translate to an unrealistic efficiency figure of about 172 lumens/Watt. You may want to question them on their units.

Paul

if you got the space for a 8mm.
here is the 4 die thing
http://www.quickar.com/8m150.pdf
like i said before even at 100 these things got very warm.
the legs are much fater and stiffer than you average 5mm type.
and because of that you can also crack the epoxy when bending the legs.

in other words they are a PITA compared to a simple 5mm led, but if your controlling the power completly, and underdrive them, and have the space, this is what i would recommend.
they are very bright for a sigle package in epoxy like that.

yeah, I don't know a whole lot about them, either but after making solitaire mod's and learning the resistoring for them, i don't have a lot of faith in even good (nichia) 5mm LED's. I put up a post not long ago about a infinity ultra
I had been using to light my computer keyboard hanging overhead, it's on sometimes 24/7 since i run it on a nimh, and after a few mth's it is really noticeably dimmer then my three other ultra's.
I also noticed that my ARC AAA-P i used real heavy for a summer tour is now dimmer then one that was left home. the one i took was brighter, and now it's dimmer. I think this behavior is something i have been
reading on CPF more often. so I guess the promises of the 10.000 to 100.000 Hr life of LED's was a little off base.

As better brighter ones come out, I wouldn't mind seeing FL maker's having light's that could have the LED's mounted for easy changing
instead of boiling/baking/heating and then picking epoxy away to get to it.
But having that sealed is what make's them great small light's so...... VDG

voodoogreg said:

yeah, I don't know a whole lot about them, either but after making solitaire mod's and learning the resistoring for them, i don't have a lot of faith in even good (nichia) 5mm LED's. I put up a post not long ago about a infinity ultra
I had been using to light my computer keyboard hanging overhead, it's on sometimes 24/7 since i run it on a nimh, and after a few mth's it is really noticeably dimmer then my three other ultra's.
I also noticed that my ARC AAA-P i used real heavy for a summer tour is now dimmer then one that was left home. the one i took was brighter, and now it's dimmer. I think this behavior is something i have been
reading on CPF more often. so I guess the promises of the 10.000 to 100.000 Hr life of LED's was a little off base.

As better brighter ones come out, I wouldn't mind seeing FL maker's having light's that could have the LED's mounted for easy changing
instead of boiling/baking/heating and then picking epoxy away to get to it.
But having that sealed is what make's them great small light's so...... VDG

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Nobody from Nichia ever claimed their 5mm LEDs had 10,000 to 100,000 hours of life. More like 1,000 to 2,000 when kept cool and driven to spec.

When you drive them above 20mA, you see an exponential drop in life. As I recall, ARC Flashlights was abusing them severly at 60-80mA. That easily explains the incredibly short life span, and rapid dimming you saw in yours.

NewBie said:

Nobody from Nichia ever claimed their 5mm LEDs had 10,000 to 100,000 hours of life. More like 1,000 to 2,000 when kept cool and driven to spec.

When you drive them above 20mA, you see an exponential drop in life. As I recall, ARC Flashlights was abusing them severly at 60-80mA. That easily explains the incredibly short life span, and rapid dimming you saw in yours.

Click to expand...

Edit: I have typed about 5 different long post's and they locked up, if this goes through I will re-type my original post. This is just to address this incorrect statment.


I am sorry but must disagree. i am a bit of a pack rat and have kept most of my FL incert's all most all with a few excepton's state from the manufactor
"100,000 or lifetime" on nichia LED's. Not that i care but it's a matter of record
at least to consumer's. VDG

Quick off topic suggestion for long posts. I often highlight the text and copy to clipboard if it's taken a while to write. That way if the page goes west I just paste the text back in.

Anyway back on topic. Interesting reading of LED lifetime vrs overdriving. I guess there's no overdrive data on the cheap asian LEDs?

Learjet said:

Quick off topic suggestion for long posts. I often highlight the text and copy to clipboard if it's taken a while to write. That way if the page goes west I just paste the text back in.

Anyway back on topic. Interesting reading of LED lifetime vrs overdriving. I guess there's no overdrive data on the cheap asian LEDs?

Click to expand...

I did that this time, so i have it, but still mighty frustrating when you can't post more then 4 paragraph's.

Anyone know why this happens? I know there were posts about it
Mainly when responding to an E-mail notification locking up but i have had
it happen one before this time. VDG

Hi, I'm new to the forums here and new to LED Flashlights. I'm interested in getting more power of these things too if possible. I've briefly looked at some of the links provided here but how do you even overdrive these things...with more powerful batteries or something?

I just bough two LED flashlights...the Inova X5T: http://flashlightreviews.com/reviews/inova_x5t.htm and the Litepro Teknolite: http://flashlightreviews.com/reviews/litepro_teknolite.htm

Most impressive overdrive I have done with a LED, was 120 volts.

Far more impressive than any normal LED operation. Very nice POP/flash/smell. It doesn't last long, but you can cheaply reproduce the fun by picking up a "grab-bag" of cheapo leds.

Bowen said:

Hi, I'm new to the forums here and new to LED Flashlights. I'm interested in getting more power of these things too if possible. I've briefly looked at some of the links provided here but how do you even overdrive these things...with more powerful batteries or something?

I just bough two LED flashlights...the Inova X5T: http://flashlightreviews.com/reviews/inova_x5t.htm and the Litepro Teknolite: http://flashlightreviews.com/reviews/litepro_teknolite.htm

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those are nice light, but like said, you cant overdrive them. whats the statement "the light that burns brighter . . . ."
but if i was to try, there is a 5mm 4x parellel die white out there also, and i would try putting them in, not to overdrive, but to purposfully under drive.
with a 5mm 100ma led, running at 20-40mabey 60ma, it might have a longer life.

i was surprised to see that they finnaly have a 4die style of 5mm led, and am getting some to test.

also the newest nichitas, are pretty nice, while it take a LOT more power to get more light to a human eye, i think they are stronger longer life leds, they look good, and the tests of them (as shown in that other thread) show they are also pretty good compared to the Ebay special

Thanx VidPro, I'm sure I'll like them when I get them. Since I'm so new to this, I'm sure I'll just stick to the default LED's and/or batteries with this flashlights. I'll be a little more daring with some cheaper lights in the future though. It's tough though when you're !

About two years ago, I read on a Nichia's document that: at 50 mA (comparing to normal current at 20 mA), the luminous flux of a 5 mm white led becomes 50% after ... 100 hours!! (yes, half of initial outpout after only one hundred of hours).

(And as I meseared, this current is frequent with new batteries on many "cheap" and even "less cheap" flashlights. Many (most of?) manufacturers boost leds in order to decrease production cost; it shines very well at the shop, but that's not honest with respect to the consumers who know nothing about that.)

And don't forget that an overdriven led is less efficient than a lowdriven led.
4 leds at 10 mA each are more luminous than one single led at 40 mA.

So, I would advice: stay at 20 mA per led, or maybe 30 mA with good quality leds (Nichia,...) but no more.

Cavannus said:

About two years ago, I read on a Nichia's document that: at 50 mA (comparing to normal current at 20 mA), the luminous flux of a 5 mm white led becomes 50% after ... 100 hours!! (yes, half of initial outpout after only one hundred of hours).

(And as I meseared, this current is frequent with new batteries on many "cheap" and even "less cheap" flashlights. Many (most of?) manufacturers boost leds in order to decrease production cost; it shines very well at the shop, but that's not honest with respect to the consumers who know nothing about that.)

And don't forget that an overdriven led is less efficient than a lowdriven led.
4 leds at 10 mA each are more luminous than one single led at 40 mA.

So, I would advice: stay at 20 mA per led, or maybe 30 mA with good quality leds (Nichia,...) but no more.

Click to expand...

So does the Inova X5T have good LED's or not? According to the Pocketlights site, the Teknolite has four quality Nichia LED's. I don't see anywhere about the X5T having Nichia LED's. The Teknolite isn't better than the X5T is it? Well save the battery life of course.

Bowen said:

So does the Inova X5T have good LED's or not? According to the Pocketlights site, the Teknolite has four quality Nichia LED's. [...]

Click to expand...

I would trust Pocketlights, or I would write an email to Inova to be sure.

Otherwise, a visual comparaison may help: most of "clone" leds don't have exactly the same shape of exposy body base, their die phosphor is less yellow than Nichia one, die cup and leads look different, etc.

But a "clone" led lowdriven may be a better choice than a Nichia led overdriven... Mesure yourself the amperage!