LED roadway markers causing seizures?

IsaacHayes

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Maybe they'll do something about it. I hate the PWM Cadillac led taillights too.
 

EngrPaul

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Photosensitive Epilepsy

"Flashing lights or rapidly changing or alternating images (as in discotheques, around emergency vehicles, in action movies or television programs, etc.) are an example of patterns in time that can trigger seizures..."
 

Stereodude

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All they have to do it turn up the PWM frequency to something like 180Hz or so and it goes away. And, I agree the Cadillacs are very annoying.
 

Veto

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I despise the Cadillacs as well. I -think- there is another PWM tailed vehicle on the road as well. I've always been very sensitive to flashing, caused no end of tension headaches as a teen with both fluorescents and CRT's until it was diagnosed. I still can't stand a 60Hz monitor, it makes me uncomfortable watching them blink.

Mini-Hijack: Any of you able to see the LEDs on vehicles that have both incan and LED light up earlier than the incan?
 

Stereodude

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There are several other PWM tail light equipped vehicles out there. The Caddy's are just the worst of the batch for flicker.
 

Chargeit

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There is a Volkswagen (Passat?) I follow to work on a regular basis... makes for an annoying 10 minute drive!
 

EngrPaul

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I hate the 99 year old driving the caddy with the brake lights always on. :lolsign:
 

BBL

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someone explain the problem with led-brakelights to me? I thought those were common today, and i never noticed anything anoying.
 

Veto

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BBL said:
someone explain the problem with led-brakelights to me? I thought those were common today, and i never noticed anything anoying.

It's not LED brakelights themselves, it's the PWM controlled ones. PWM dims them from full power not by reducing power, but by blinking them at a rate that isn't supposed to be noticed, but will reduce the apparent brightness.
 

EngrPaul

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Persistence of vision is the basis for running LED's since the beginning of LED displays. Each digit is briefly displayed in a rotating sequence. This reduces the number of wires needed to run from the driver to the display.

It's acceptable when both the display and viewer's eye focus are not moving relative to each other. Try jiggling you eyes (or chewing ice) when looking at a LED alarm clock to demonstrate what happens when this is not the case.

In a vehicle, there will hardly ever be a situation where the viewer's focus and the car's motion in front of you will be in sync.

As far as I'm concerned, these lights should be recalled and fitted with direct dimming. The only vehicles allowed to have pulsating lights (other than turn signals) are emergency vehicles.
 

cdosrun

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PWM = Pulse Width Modulation. It relates to the adjustment of the space/time of the flashes, contrasted with Pulse Frequency Modulation where the width of the pulse is the same, they just change the number per second. I'm sure someone else will put it much better (correct my mistakes).

I find the flickering really distracting on the motorway, a long time ago, the first car I saw with LED tail lights was a Maserati, and it is still the worst I have ever seen for flickering, they are more like a strobe. Although, I haven't really seen many cars where it is brilliant, even some BMWs seem to flicker (I'm quite sensitive to it though).

Andrew
 

raythompson

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Nov 14, 2005
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Dadof6 said:
What do the letters PWM mean?
Pulse Width Modulation.

Basically the width of the electrical current applied to the device is changed from 0% to 100% to control the brightness. Basically a pulse width of 50% should produce half brightness of 100% pulse width. But the effect is not entirely linear. A high pulse width rate is better than a slow pulse width rate. It is also more difficult/expensive to implement due to tighter electronic requirements.
 
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