Hi Neil,

One month of solid operation is more than your brakes will be applied for 
the lifetime of the vehicle.

LED's DO NOT  violently self destruct (generally), they become dimmer over 
time.

I've used LED's in place of lasers for data transmitters and have pulsed 
them at ma 100 (50 percent duty cycle) for months and months (while doing 
long term remote receiving several miles away). I've never had one blow up 
and have never had one get soft.

The ratings for most LED's is number of hours at maximum ratings before the 
intensity is reduced by 10 percent. There was a nice article some months 
back about this in EDN.

It's possible you might be right, but I think worrying about higher than 
rated current for brief periods of time is not warranted.

I fired up my LED's last night and determined they can be run at 3 ma at 
night and 8 ma in the daytime to give adequate brightness........probably 
because I have so many of them in series.

I was thinking about a photocell to determine night time and daytime 
operation and set he current accordingly.

GL to all.

Art




At 12:13 PM 8/9/2005, you wrote:
>On Friday 05 August 2005 07:51 pm, KY1K scribbled:
> > Mine are rated for 30 ma max as well, so with the running lights only, they
> > are well within ratings. With the running and brake lights on together,
> > they are running over their max ratings.
> >
> > I powered up a few on the bench here and ran them at 60 ma for a month. At
> > the end of the month, it had the same apparent intensity as a brand new
> > diode did (compared them side by side).
>
>One month may be too short to determine even a significant decrease in their
>lifespan.  To each their own.  Where the ones I'm building will be mounted,
>it will be a nightmare to pull out and replace LED's when they are blown.  I
>won't be convinced into running more continuous current than recommended.


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