Date: Thu Nov 30 17:13:58 2006 Back to Contents

Author: Paul Nord

Subject: Re: Cars, lights, and mileage - was Re: The

Post:

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JZ,

Thanks! That's really interesting to know.

Can you let the industry know that I really hate those things in tail
lights? :)

Paul

On Nov 30, 2006, at 3:18 PM, Gerald Zani wrote:

>
> LED lights are more efficient when driven with pulsed DC rather
> than pure DC. They run cooler and brighter when driven with
> pulses. Depending on the LED color some LED lights are driven at a
> frequency somewhere between 10 and 20 kHz pulsed DC.
>
> LED lights, including flashlights, today use a programmable,
> embedded microprocessor integrated in the lamp to control the
> pulses, and to adjust the pulse frequency and the pulse duty cycle
> for changes in the battery power to better maximize the lamp
> efficiency when the battery gets low.
>
> That is why they flicker.
>
> I worked in industry making commercial LED lamp products before I
> got into education.
> -- JZ
>
> At 01:26 PM 11/30/2006, you wrote:
>> On 11/30/06, Paul Nord wrote:
>>> Has anyone noticed LED tail lights that flicker?
>>
>> I wonder why they flicker? I thought the electrical system of
>> your car was powered via the battery, and that the battery output DC.
>>
>> I also find many newer headlights bothersome, though; I have
>> attributed it to the difference in brightness compared to older
>> lights, but maybe I've been bothered but not noticed the flicker?
>>
>> --
>> regards
>> -Krishna
>>
>> Krishna Chowdary
>> Department of Physics & Astronomy
>> Bucknell University


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Thanks!=A0 That's really =
interesting to know.Can you let the industry =
know that I really hate those things in tail lights?=A0 :)Paul=
On Nov 30, 2006, at 3:18 PM, Gerald Zani wrote: LED lights are more efficient when driven with pulsed DC =
rather than pure DC.=A0 They run cooler and brighter when driven with =
pulses.=A0 Depending on the LED color some LED lights are driven at a =
frequency somewhere between 10 and 20 kHz pulsed DC. LED lights, =
including flashlights, today use a programmable, embedded microprocessor =
integrated in the lamp to control the pulses, and to adjust the pulse =
frequency and the pulse duty cycle for changes in the battery power to =
better maximize the lamp efficiency when the battery gets low. =
That is why they flicker. I worked in industry making commercial =
LED lamp products before I got into education. -- JZ At =
01:26 PM 11/30/2006, you wrote: On 11/30/06, Paul Nord =
=
wrote: Has anyone =
noticed LED tail lights that flicker? I wonder why =
they flicker?=A0 I thought the electrical system of your car was powered =
via the battery, and that the battery output DC.=A0 I also find =
many newer headlights bothersome, though; I have attributed it to the =
difference in brightness compared to older lights, but maybe I've been =
bothered but not noticed the flicker? -- regards =
-Krishna Krishna Chowdary Department of Physics & =
Astronomy Bucknell University =
=

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From tap-l-owner@lists.ncsu.edu Thu Nov 30 17:13:58 2006

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