[sdiy] The Humble LED.

[Tim Ressel]

Batz,

I seem to recall the Philips (now osram) infrared LEDs
I use have a spec for pulsed operation. 

http://www.osram.convergy.de/scripts/product_family.asp?CLSOID=10064&FAMILYOID=20107

There is a graph showing pulse derating.

--tr

--- Batz Goodfortune <batzmanx at all-electric.com>
wrote:
> Y-ellow All.
>          I have this crazy idea. I think it's been
> done before but for 
> power saving rather than brightness. I want to get
> real light out of an 
> array of LEDs. (Yellow in this case) I've pushed the
> array to the limits of 
> reasonable reliability (IE:35mA per LED) but still
> it's not bright enough.
> 
> I would assume, rightly or wrongly, that heat is the
> killer with these 
> devices as with many other semiconductor materials.
> I remember that one of 
> the things Sinclair did when he (allegedly) invented
> the digital wrist 
> watch, was to pulse the circuit. The LEDs were not
> on 100% of the time. 
> Though I have no idea of the duty cycle. For him, it
> meant the same 
> brightness but for a fraction of the battery usage.
> I'm thinking the opposite.
> 
> In theory, should I not be able to pump
> significantly more current through 
> the LEDs so long as that current was pulsed. Like a
> LED bike tail light. 
> I'm thinking here about 50% duty cycle @ 3 or 4 Hz
> and pumped at between 60 
> & 80mA per LED.
> 
> The reason I'm putting out this general question is
> that I can find no 
> precedence for doing this. Other than some very
> expensive and specialized 
> LED technology that's now kicking round.
> 
> Does anyone have any compelling evidence or caveats
> they'd like to share? 
> I'd most appreciate it.
> 
> Strangely, this is the first time I've ever been
> able to feel any heat from 
> a LED. Or should I say, a slight warmth. It's winter
> time and I can just 
> feel a bit of a warmth in the glow. I guess I've
> been a fairly conservative 
> LED user up until now but I'm also figuring that
> with every extra mA at a 
> constant on-time, the reliability and longevity of
> the devices will be 
> reduced. The only good thing about incandescent
> bulbs VS a LED array is 
> that at least Bulbs are easy to change.
> 
> Anyway, before I go to all the trouble of building
> up a triple5 (or 
> something), I just thought I'd ask if someone has
> any experience or 
> knowledge of doing this kind of thing.
> 
> Thanks very much in advance.
> 
> Be absolutely Icebox.
> 
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