From: "R. Lewis"
Subject: Re: What is maximum current for LED?
Date: Wed, 2 Oct 2002 22:26:29 +0100
Organization: Nextra UK
NNTP-Posting-Date: Wed, 2 Oct 2002 21:29:11 +0000 (UTC)
X-Newsreader: Microsoft Outlook Express 5.50.4133.2400
"Winfield Hill" wrote in message
> Boris Nogoodnik wrote...
> > ... there is one human vision factor. If you use pulses
> > instead of constant current, thy still will look as bright as on
> > constant current, but will dissipate much less power. So here
> > you can make them look much brighter by exceeding the maximum
> > current in pulses, but still keeping the average current well
> > under the specs.
> To my understanding, the effect one can obtain this way is not
> large, under 3x, at least for foveal viewing, and only occurs
> for pulsing at a repetition rate that's painfully obvious, say
> 15 to 25Hz. Alternately, if the LED's primary purpose is to
> attract attention, peripheral as opposed to foveal viewing has
> a much greater sensitivity to light variation, which means that
> a greatly reduced level of flashing light can be noticed out of
> the corner of one's eye, prompting further closeup examination.
> ............ (etc)
> - Win
Is there *any* advantageous effect of pulsing leds with a high current like
It appears that many 'tronics people believe that there is (or should be)
some perceived enhancement but never manage to give either a plausible
reason or an authoritative source for it being so.
Effective intensity (e.g. as per Blundell-Rey) surely becomes virtually
constant by the time any discrete 'pulses' become inseparable to perception.
Could someone with knowledge of such matters please comment.