Subject: Re: What is maximum current for LED?
Date: Thu, 3 Oct 2002 17:06:47 +0100
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"markp" wrote in message
> "John Woodgate" wrote in message
> > I read in sci.electronics.design that Nelson Win
> > wrote (in > .google.com>) about 'What is maximum current for LED?', on Wed, 2 Oct
> > 2002:
> > >I bought a few high brightness 3mm LEDs (various colors: R,G,B,W) and
> > >the specs mention a forward current (If) of 20mA and peak current (If
> > >(peak)) of 100mA (160mA for red). The specs don't say anything about
> > >the current beyond that, nor what the recommended maximum current
> > >should be. There's not even a brand name on the LEDs so I can
> > >approach the manufacturer. I want to squeeze the brightest light I
> > >can from the LEDs without prematurely burning them out. Does anyone
> > >have any experience here to recommend a maximum current? The LEDs will
> > >flash on and off at a frequency of a few hertz, 50% DC, for a duration
> > >of a couple or hours at a time. Any advice appreciated.
> > >
> > Beyond 20 mA continuous you won't get significantly more light. But at
> > 50 % duty-cycle, you need to go to 40 mA to produce the same visible AND
> > (more important) no excessive heating effect.
> > --
> > Regards, John Woodgate, OOO - Own Opinions Only.
> > you need to go to 40 mA to produce the same visible
> Not strictly true John, the eye has significant persistence (or rather the
> brain has) and tends to 'remember' the peak light output. You may find
> or even less at 50% duty cycle of a few hundred Hertz will give a
> brightness equal to the 20mA continuous. Generally PWMing can decrease
> overall power dissipation for this reason.
Forget that, made a mistake!