High frequency blinking rear lights?

[Piwoslaw]

When a new car (1-2 yo) passes me I sometimes think that its rear lights are blinking at a high frequency. Almost too fast to notice, I usually only see it with the corner of my eye as the car whooooshes past.

Is it me, or do they really blink? I'll add that often they don't look like LEDs. It has crossed my mind that maybe the blinking reduces electrical load, but what for? The savings would not be noticible, much simpler things could give much bigger FC savings.

[Uncle Dave]

It could be that to reduce the 12 v to 2 v or so for the LED that they use an oscolator then covert back to DC with a diode. More efficent than dropping the voltage with a Resistor.

[scivicblu83]

yes the led tailights are infact blinking. leds are flashed faster than you can see as a means of dimming them without using resistors because this consumes less electricity and produces less heat since resistors resist and produce heat. if you ever watch the show top gear, when theyre driving cars with led tails or led driving lights like audis have the frame rate of the camera shows the lights blinking very obviously.

[jamesqf]

I sometimes see a similar effect from any red LEDs when driving at night: gas station signs, traffic signals, and so on that you wouldn't think would be dimmed. It's like a momentary trail of copies of the light, seen in peripheral vision. I've never noticed it with any other color, just red.

[Uncle Dave]

Might be your eye. You are in a red light (smoking Lamp) while waiting to go out on deck, you had better have good night vision. It is the way the eye works.

The electronics of the LED is basically the same it is not?

[some_other_dave]

The LED lights are indeed blinking. Definitely when they use the same lights for taillights and brake lights; those are practically all done by blinking the LEDs at a lower rate until the brake lights are supposed to come on, then putting them on solid. Or at least putting them on a higher duty cycle while the brake lights are on.

My wife seems to have a lower persistence of vision than most of us; the LED taillights drive her crazy. I can see them in my peripheral vision, or when I'm very tired.

Cadillacs seem to be the worst for blinking to me.

-soD

[3-Wheeler]

Originally Posted by some_other_dave

The LED lights are indeed blinking. Definitely when they use the same lights for taillights and brake lights; those are practically all done by blinking the LEDs at a lower rate until the brake lights are supposed to come on, then putting them on solid. Or at least putting them on a higher duty cycle while the brake lights are on.

My wife seems to have a lower persistence of vision than most of us; the LED taillights drive her crazy. I can see them in my peripheral vision, or when I'm very tired.

Cadillacs seem to be the worst for blinking to me.

-soD

Yes, I have noticed the Cadillac's as well.

I read an article about light perception of the "eye-brain" connection several years ago, and it went on to say that quickly blinking lights are perceived more quickly by the brain than solid lights.

They actually did studies to determine that a on/off frequency of around 100 to 200 Hz makes this effect more noticeable.

I have no idea what frequency the Cadillac lights are run at, but they certainly grab your attention.

The article did not mention it, but I suppose one could get an energy savings by reducing the duty-cycle of the lights while pulsing them.

Jim.

[Piwoslaw]

A few days ago I happened to be watching the news when they were talkng about a YT video with a record number of views. It just so happened that they aired the few seconds with blinking rear lights. Check out 1:48-1:51, the frequency of the blinking lights of the red car and the video's fps rate are slightly out of sync.

http://www.youtube.com/watch?v=9bZkp7q19f0