EM emissions from auto taillights.
 

Slightly off topic - I've seen a couple of new automobiles with
time-multiplexed LED taillights. What would be the advantage of such a
design in an automobile?
--
73, Cecil, W5DXP

"Cecil Moore" wrote in message
ups.com...
Slightly off topic - I've seen a couple of new automobiles with
time-multiplexed LED taillights. What would be the advantage of such a
design in an automobile?
--
73, Cecil, W5DXP


longer mean time between failure?

TimPerry wrote:
"Cecil Moore" wrote:
Slightly off topic - I've seen a couple of new automobiles with
time-multiplexed LED taillights. What would be the advantage of
such a design in an automobile?

longer mean time between failure?

Does a time-multiplexed LED have a longer MTBF than a constant current
LED?
--
73, Cecil, W5DXP

"Cecil Moore" wrote in message
ups.com...
TimPerry wrote:
"Cecil Moore" wrote:
Slightly off topic - I've seen a couple of new automobiles with
time-multiplexed LED taillights. What would be the advantage of
such a design in an automobile?

longer mean time between failure?

Does a time-multiplexed LED have a longer MTBF than a constant current
LED?
--
73, Cecil, W5DXP


longer then an incadecent lamp at any rate

Bill Turner wrote:
Multiplexed at what rate? Faster or slower than human eye
perception?

The rate is hard to estimate - maybe 60-200 Hz? You know how - if one
sweeps one's eyes from side to side when looking at a time multiplexed
light source, it looks like a dotted line? Well, on two occasions at
night, I was shifting my eyes when I noticed the taillights on certain
new models of automobiles are time multiplexed. I'm just wondering if
anyone knows anything about them - like what is the advantage over
constant current LEDs? Am I the only person in the world who notices
such trivia? :-)
--
73, Cecil http://www.qsl.net/w5dxp

On 6 Jan 2005 06:18:08 -0800, "Cecil Moore" wrote:
like what is the advantage over constant current LEDs?
Am I the only person in the world who notices such trivia?
It's been known for quite a long time: pulsed light looks brighter.
Being imperceptible flicker has to do with the Stroud Moment.

Richard Clark wrote:

"Cecil Moore" wrote:
like what is the advantage over constant current LEDs?
Am I the only person in the world who notices such trivia?

It's been known for quite a long time: pulsed light looks brighter.

I know that but am I the only person in the world who has
noticed that it is now being used on automobiles.
--
73, Cecil http://www.qsl.net/w5dxp


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On Thu, 06 Jan 2005 11:03:10 -0600, Cecil Moore
wrote:
It's been known for quite a long time: pulsed light looks brighter.
I know that but am I the only person in the world who has
noticed that it is now being used on automobiles.
Just as I figured.... another sucker ball.

On Thu, 06 Jan 2005 08:25:29 -0800, Bill Turner
wrote:
What other reason could there be?

Hi Bill,

The usual reasons: Brighter; Lower Power; Longer Life; Lower Loss - as
long as the added complexity is offset by the economic gain. If they
were dual diodes connected parallel and reverse polarity driven by AC,
then the advantage would be reduced cathodic reduction of contacts
exposed to water (for years I noted how the poorly built US cars went
through tail lights that burnt out due to corrosion). AC systems also
extend lifetime to conventional filament lights.

Now, by Brighter, this is not due to higher peak currents. LEDs don't
really peak as well as other devices. Their overdrive capacity is
somewhat limited. Rather, the Brighter is a physiological response.
It is actually the same brightness, except we perceive it as brighter
(although, if the period exceeds the Stroud Moment this may no longer
hold). Light can be frustrating to compare to measurements, because
impartial measurements will reveal little difference to what we
perceive to be dramatic change. One of those tricks of the brain.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
Cecil Moore wrote:
I know that but am I the only person in the world who has
noticed that it is now being used on automobiles?

Just as I figured.... another sucker ball.

Zero probability that you simply misunderstood my original
question? Did you know it is now being used on automobiles?
--
73, Cecil http://www.qsl.net/w5dxp


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