Re: (ET) Ralph's LEDs

["David Roden (Akron OH USA)" <roden ald net>]

I recently read something fascinating about LEDs.  Have you noticed how 
intense the new LED traffic signals appear?  (At night some are so bright 
that the green ones actually are almost painful to view.)  

This is how it's done.  The LEDs are driven by a pulsed waveform.  The on 
current is TEN TIMES their rating, but the duty cycle is only 10% - that 
is, 
on (for example) on 1 picosecond, off 9 picoseconds, repeat.  Thanks to 
persistence of vision, the human eye sees the peak intensity as continuous 
high intensity; but the LED "feels" the average current, which is just its 
normal rated current. 

I'm sure the same thing could be done with automotive signals (if it isn't 
already).

Clever, no?


David Roden - Akron, Ohio, USA
1991 Solectria Force 144vac
1991 Ford Escort Green/EV 128vdc
1970 GE Elec-trak E15 36vdc
1974 Avco New Idea 36vdc
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Cutting the space budget really restores my faith in humanity.  It
eliminates dreams, goals, and ideals and lets us get straight to the
business of hate, debauchery, and self-annihilation.

                               -- Johnny Hart
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