Date: Thu Nov 30 16:44:39 2006 Back to Contents

Author: Gerald Zani

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

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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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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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From tap-l-owner@lists.ncsu.edu Thu Nov 30 16:44:39 2006

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