LED (Flashlight) Durability
 

In case someone still had doubts that it was safe to use the N900's LED flash as a light source, I have a quick story.

A few days ago, my dorm's bathroom lights burned out. Maintenance hasn't fixed it yet. When using the bathroom, or showering, I have to use the N900's LED flashlight. It provides enough light that if pointed at a wall, the entire bathroom is visibly illuminated.

Better yet, today my GF and I showered together while only having the N900's LED's to illuminate the bathroom (I left it out of reach of water, obviously). For at least 15 minutes (prob'ly longer), the LEDs were constantly on using the flashlight status menu applet. They still work just fine, didn't burn out, noticeably change or heat up, etc. So while I realize hardware may have some differences, I suspect that you can file this away as yet another reason to think the flash LEDs are perfectly safe to use as a flashlight, even for longer periods of time.

Re: LED (Flashlight) Durability
 

any idea about the life in the long term?? I'd be more concerned about that.

Re: LED (Flashlight) Durability
 

We need PICTURES for further investigation. ;)

Re: LED (Flashlight) Durability
 

why wouldn't it last ? It's an LED, not a flash bulb like on the older phones. LED have a very long life expectancy.(7 years irc)

Re: LED (Flashlight) Durability
 

hahahahahaha! =))

Re: LED (Flashlight) Durability
 

i'd rather say it's a case of "video or it didn't happen". ;)

Re: LED (Flashlight) Durability
 

Doubfully what is GF?
Girlfriend? Grand Father? Grape Fruit?
:)

Re: LED (Flashlight) Durability
 

i think youre doing it wrong

Re: LED (Flashlight) Durability
 

GF = Guy friend, Gay Friend

Re: LED (Flashlight) Durability
 

LED's do not generate heat. You wire a resistor in series with them to ensure that the voltage they see never goes above a certain level, and this controls whether they heat up or not. An LED *should* have virtually limitless lifespan, and it is more likley that the other components of the circuit will give way before any LED will.

And you only managed 15 minutes? She won't be your GF long with that kinda performance. Although, if only YOUR legs were touching the ground I'd rescind that comment ;)

Re: LED (Flashlight) Durability
 

Let me update you guys on the current state of affairs. In many applications where LEDs are used as flash, the LED is driven a much higher current then it was designed for.

Also LEDs DO GENERATE HEAT if you talk about high power LEDs. The small ones that are used as indicator lights obviously not.

A lighting product we developped at our company used powerLEDs at higher current, because the spec has an average power number, and also a much higher peak power number. At some point, the software failed (wasn't me!), and the LED stayed on. For a while. Then it went dead.

So, before you start spreading your facts, read up on the matter. It may very well be that the n900 flashes its LED at its peak current, above the nominal (average) power, causing them to overheat and die.

So thanks to the OP for taking the risk and letting us know they hold out pretty good :)

Re: LED (Flashlight) Durability
 

Actually, they do. A little. Plus a generated light can heat things up.

Re: LED (Flashlight) Durability
 

LED life is shortened by excessive heat. If you drive it hard, it won't last so long.

However, the flashlight app drives the LEDs within their specs, and at a much lower level than they are driven while flashing, so durability shouldn't be an issue.

Re: LED (Flashlight) Durability
 

I think LED on the N900 will probably last you 100000hours of continuously lit 24/7. My samsung LED TV last 100000hours as well with about 7-11years usage. So I guess as long you did not overpowered the damn thing, then it will not break within the next few month.

Not sure about the LED on the iPhone4 though. Apple using the cheapy LED and no hard detail specification of it. Nokia fully documented the N900 hardware and that make it safer than not knowing the limitation :)

Re: LED (Flashlight) Durability
 

It all depends on the power level they're driven at. If they heat up to more than 60-90C or so on the die, they start burning out.

As a real world example, the maglite led bulb has extra circuitry to automatically reduce power when it gets overheated. This happens after about 2 minutes, after which brightness starts to drop. Usually not noticed by the users, as humans are terirble at perceiving relative brightness.

Re: LED (Flashlight) Durability
 

I assume within the specs for always on (t=infinity)? Because LED specs aren't as simple as they used to be, and a spec can specify a much higher current (with a time limit).

Sorry, no time to go look the n900 specs up myself ;)

Re: LED (Flashlight) Durability
 

Typical LEDs have a light efficiency of about 25 percent. Newer technology is better, but generally, that's it.

I have a lighting system at home that is custom made, featuring CREE's latest and trust me, they need large heat sinks, air flow and care. Overall, the best of them dissipate at least a quarter of pumped power in heat.

Stats vary because after a certain level the power-to-light ratio goes through the roof. Lighting systems usually are close to this limit, it's a balance between efficiency and lifetime.

I very much doubt any LED system dissipates less that 25 percent, in a lighting solution, like N900's flash. As a result, we're looking at some heat, and, not dissipated, it will heat the base and cause it to dim.

So, not only they DO heat, the first sign you are in trouble is that the light DIMS, not burns out. After 15 minutes, it could still work but only put out 80 percent the light it used to.

I usually use the backlight for the LCD for light, at least they have heat sinks, are not clumped together and have been designed to stay on for a long time.

Use a blank image of a blank browser page, crank backlight to max and enjoy.

Re: LED (Flashlight) Durability
 

just wanted to add here

one night where i was very sleepy, i forgot to turn off the flashlight (cam LEDs) and it burned for 5hours+.

it still works fine since it has been stated before that when you use flashlight function the LEDs are only driven at a low % of there full potential.

and i have also been making LED lights for home & flashlights for 6+ years, so i know what they can take.

Re: LED (Flashlight) Durability
 

On average, the N900 LED should last around 25,000 hours, and the very little heat shouldn't affect it's lifespan.

Re: LED (Flashlight) Durability
 

To all the performance/pics/videos jokes: The girlfriend and I almost always shower together. Doesn't mean all of them have to turn sexual. That time it was a regular shower.

On another note, thanks for all the informative posts on LED technology.

Re: LED (Flashlight) Durability
 

We didn't mean for you :D

Re: LED (Flashlight) Durability
 

As Petur says.The LEDs wouldn't give enough light for photography, so they are "overpowered" so to speak. More than enough power is supplied in an effort to get them flood the scene enough. But because this power is only a very short burst (milliseconds) if that, there isn't enough heat generated to burn them out. Supply that amount of power constantly over a prolonged lengh of time and it could potentially damage the LCD filaments.

Just something that I learned during an electronics course.

Re: LED (Flashlight) Durability
 

Similar story here. During pre-sleep EightyOne-sessions in dark, 1/5 is still too bright so I keep the leds on, illuminating the background to compensate for the overly-bright backlight (I'm somewhat sensitive, I have most of my devices on minimum brightness all the time and it's usually still too much, but at least I enjoy improved battery life...).
Once I fell asleep with the leds still on, and woke up about 10 hours later. I was slightly worried about durability of the leds then, but seeing how it happened months of daily usage ago I have learned to "stop worrying and love the phone".

Re: LED (Flashlight) Durability
 

You can reduce screen brightness further. Try in terminal:
Number in the command should be in range 1..255. Change is temporary -- it lasts till next brightness autoadjust or screen on/off cycle.

Re: LED (Flashlight) Durability
 

I am sure you mean:

;)

Re: LED (Flashlight) Durability
 

We are talking about the FLASH Leds at the camera right???

and side note on your screen brightness, check out my Custom Brightness for N900 - no ALS is now ready for install this will give you the brightness settings you want and disable that stupid slow reacting light sensor

Re: LED (Flashlight) Durability
 

Just read the fine source code for the flashlight app.

Re: LED (Flashlight) Durability
 

The range is 0..255, but 0 turns the backlight off, though with the N900s transreflective screen it is quite usable in bright sunlight with the backlight off.

Re: LED (Flashlight) Durability
 

since PR 1.3 i had to change my custom brigthness to only go to brightness 2, because now after PR 1.3 Value 0 and 1 turns to screen brightness/leds off

Re: LED (Flashlight) Durability
 

That is theoretically correct, but it's not how it works. A phone flash has 2 modes, flash and light. One lights up to 60 percent, continuous and the other to 120 percent for 0.4 seconds.

When shooting video in the dark, the LED stays on, with no ill effects. The power is way under what is pumped through on flash.

The flashlight app uses the continuous underpower mode, otherwise it'd be dead within minutes.

Re: LED (Flashlight) Durability
 

it depends on the cooling. and it might be that when putting leds to camera flash, cooling isn't as good as it should be when keeping leds on constantly.

but even when heating reduces 50% of life expectancy, does it really matter?

Re: LED (Flashlight) Durability
 

Thanks for clearing this up, these are the details that mattered. Case closed, move along ;)