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From: commgrp@silver.ucs.indiana.edu (BACS Data Communications Group)
Newsgroups: sci.electronics
Subject: Re: pulsing LEDs
Message-ID: <53169@iuvax.cs.indiana.edu>
Date: 3 Aug 90 19:04:57 GMT
Sender: daemon@iuvax.cs.indiana.edu
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murray@src.dec.com (Hal Murray) writes:

>Years ago, somebody told me that the eye responds more if the 
>available energy is clumped into bursts.  This was during a 
>discussion of multiplexing LEDs (or LED decoders).  The idea was that 
>multiplexing LEDs actually increased the apparent brightness for a 
>given average current.

>...Has anybody seen any charts eye response vs duty cycle?  Any 
>suggestions as to where I should look?

See _Modern Electronics_ magazine, June and July 1990, (Forrest Mims' 
monthly "Electronics Notebook" columns) for nice reference articles 
about LEDs, including the new high-output types. It doesn't have the 
specific info that Hal is looking for, but does discuss driving LEDs 
with high-current pulses:

"...diode can be driven by current pulses having a peak amplitude of 
300 mA, as long as the pulse diration does not exceed 1 millisecond 
and duty cycle remains below 5 percent.  At 300 mA, the diode emits 
more than 10 times the optical power it emits at 20 mA..."

--

Frank Reid     W9MKV     reid@ucs.indiana.edu