Re: (ET) Ralph's LEDs

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

On 23 Nov 2003 at 17:20, William Korthof wrote:

> Where did you
> get the information that a pulsed power supply is common?

>From an online friend of mine who's an electrical engineering prof at 
>Duke 
University.  Here's what he wrote:  

"What appeared to be red LED taillights, turn-signal lights, and brake 
lights on buses in Phoenix and Tucson were a sign of the time and of good 
application. Red units on traffic signals seem like a great idea also.  

"Be aware that the psychological appearance of a bright light is achieved 
by 
rapidly pulsing the LED with high current and a low duty cycle.  A 
brighter 
light is gotten with 10 X maximum current at a duty cycle of 10% or less. 
The average current is no greater than supplying the rated max current for 
100% of the time."

If this information is incorrect, I apologize - though the method 
certainly 
sounds valid and could probably be used to good effect should one wish to 
replace some or all of the ET lamps with LEDs.


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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