# Irritating trend in automotive lighting - PWM taillights



## dfred (Jan 12, 2006)

Recently I've been seeing an increasing number of vehicles on the road using PWM dimming for LED taillights. I tend to keep my eyes moving a lot when I drive and at least some of these pulsed taillights produce extremely distracting ghost images in my vision. Anybody else encountered this effect?

My only positive ID so far are Cadillac STSes, but I've seen a few curvy high-end SUVes (Lexus maybe?) have them too. I haven't been close enough to get a definitive ID though... As expected the problem is worse at longer distances because the eye sweeps past more linear real estate at a given angular velocity -- thus seperating the pulses more noticably.

I'd be interested to collect more definitive info on the manufacturers implementing their dimming so poorly as to cause this strobing effect. If anybody else has good identifications of affected makes/models please post...


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## IsaacHayes (Jan 12, 2006)

I'd hate that as well. Some people can't see pulse stuff, but I can. 60hz monitors makes me sick, 75hz annoys me. I can see the frequency flicker from my Pioneer OEL cd player. And yes it makes "ghost" copies of it's self when you move your eyes across it fast.


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## PhotonWrangler (Jan 12, 2006)

I agree that it's an annoying trend and it causes undesirable "ghost" images when the eye sweeps across it laterally.


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## Galiphrey (Jan 12, 2006)

I agree completely; those tail-lights are really anoying, and distracting for other drivers. It seems to me that all they would have to do to fix it is to crank up the pulsing frequency. It's a safety issue not unlike those stupid spinning hub-caps that are specifically designed to deceive your quick speed evaluation. I think those should be outlawed.


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## dfred (Jan 13, 2006)

Well, there seems to be a consensus. :laughing: Keep an eye out for specific makes and models...


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## Galiphrey (Jan 13, 2006)

On the road, today, I happened to notice an 18-wheeler with LED taillights that showed no visible pulsing, and I got a chance to inspect both of its output levels (stuck behind it for a WHILE). So, it's obviously not necessary to pulse them so slowly that it annoys people. Those that do should stop it.

There are television sets that actually scan red, green, and blue at different moments in time (spraying light through some kind of multi-color fly-wheel, or something), and amazingly it looks fine, by combining components within the persistence of your vision, at least until such time as you MOVE your eye. For instance, if you dart your eye to the left or to the right, possibly to follow some motion in the content of the film, then something very interesting happens: The whole screen breaks up into its component colors and unintended combinations thereof, for just an instant, while your eye is darting, because the components become misaligned during the motion of your eye. It's a wierd effect.


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## Warhoggie (Jan 14, 2006)

Blah, distraction is a state of mind. Likek Galiphrey, I will see it only if I stare at it, and then shift my eyes to something else very quickly.

To me, there are other things far worst, like billboards, yapping on the cell phone while driving, staring at UFOs flying by, etc.


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## Zelandeth (Jan 15, 2006)

Positively identified culprets in the UK (These things drive me mad).

All models using LED's from Mercedes, BMW and VW/Audi that I've seen use PWM. Most, but not all Lexus (don't see many of them here though). The tail light units used by the coachbuilders Alexander and Plaxton appear to be culprets for this as well Those Optare use appear to be proper current dimmers though.

PWM is fine for dimming in general applications, but to me, using it on something that's by definition going to be on the move is a bad, bad idea. It makes them REALLY distracting if you spot it out the corner of your eye on a traffic island or something. And distractions lead to accidents.


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## Navck (Jan 15, 2006)

My monitor goes to 100hz, its more comfortable than the other settings (60, 72, 82, 85, all those weird ones)
My HDS on low levels, I can REALLY notice flicker.


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## Raccoon (Jan 19, 2006)

I've been seeing pickup trucks with the third aux brake light having a blink circuit on it, so it blinks whenever the brakes are depressed. This is absolutely annoying to me and will probably cause me to rear-end someone-- quite the opposite of its intended affect. It's so bad, I wish I carried my bb gun with me whever I go.


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## Mark2 (Jan 19, 2006)

I don't like this trend either. Why not use current regulation? To safe a couple of bucks? But not all cars are equally "bad". I recently drove behind an Audi and the flicker was there, but very fast and not as annoying as on other cars. Also, soft start for LED break lights would be a good thing.

My MPIO mp3 player has an OLED display that flickers very slowly, it's terrible.


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## Ikonomi (Jan 19, 2006)

I actually noticed PWM taillamps on a Cadillac SUV for the first time tonight, and then saw this thread. I'm sure I have looked at them before and just not noticed. I did not find the strobe effect annoying at the time I noticed it, but I can see how it might bother some people. Computer monitors with slow refresh rates give me a headache, for example.


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## dudeldam (Jan 19, 2006)

To make it worse, my otherwise excellent Toyota Avensis has a pulsed dashboard illumination, I can cover my whole field of sight with orange patterns by rolling my eyes around it. It is not so annoying when you don´t know about it, but once you have seen it, you tend to pay more and more attention to it .

A capacitor would possibly slow down the start-up time of break lights, but for tail lights and dashboard illumination, it should be an appropriate solution.

Dudeldi


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## modamag (Jan 19, 2006)

I don't get it. Why do you want to soft start your brake light? The whole purpose of LED is to gain that 1/4 sec for reaction time.


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## helios (Jan 20, 2006)

I ride a motorcycle (Honda Intercepter VFR800i) and have converted the brakelight to a pulsing LED. It gets me noticed and it sure seems like people are braking sooner (just my observation). It might be a little annoying to drivers but I'll continue to use it if it has the potential to save my life. I always pulse my highbeams when approaching intersections and other cross streets. It saved my butt at least three times this year when people stopped suddenly while pulling out in front of me. Good thing I carry a clean change of drawers when riding!


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## teenasparkle (Jun 11, 2014)

Hi - yeah - couldn't agree more. Those stroboscopic after-images can blot out people and kids in dark clothes at night! I mean do we want a disco light show on the road for amusement or do we want to concentrate on seeing what's in front of the car? So I've been wondering: what's the idea? Is it to save 0.6 Volts on the rectifying diode by running the AC straight out of the alternator? If so, we're saving greenhouse gases, yes, but like, all of about 1 cent of gas over a whole year! Is that worth having potential accidents? :naughty:


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## Conte (Jun 17, 2014)

You realize of course you unearthed an 8yrold thread. 

LED tail lights annoy me in general. They are just so much more harsh and intense then the incan equivalents. 
Anytime I'm stopped behind someone with them in traffic, I find them blinding. 
If I'm stuck waiting in a drive thru' and the guy in front of my has them and is holding the brake instead of park, it's almost painful to me. 

They are a good idea but they should really put some diffusers on them.


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## cland72 (Aug 24, 2015)

I know I'm bumping an old thread, but I didn't want to create a new one.

I've noticed the 2015 Tahoe/Yukon/Escalade SUVs have PWM in their LED taillights and it drives me NUTS. I'm shocked that they are still using technology that was available in 2006. What ever happened to incandescent bulbs? Easy to replace, cheap to buy, and they work for years if installed properly.

No wonder the sticker prices on new vehicles keep going up.


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## poiihy (Aug 24, 2015)

Just realized this is a really ole thread but the topic still applies today.


I agree with everyone here who hates those flickering taillights.
Why don't they use voltage dimming?! Or at least use a smoothing capacitor!


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## poiihy (Aug 24, 2015)

cland72 said:


> I know I'm bumping an old thread, but I didn't want to create a new one.
> 
> I've noticed the 2015 Tahoe/Yukon/Escalade SUVs have PWM in their LED taillights and it drives me NUTS. I'm shocked that they are still using technology that was available in 2006. What ever happened to incandescent bulbs? Easy to replace, cheap to buy, and they work for years if installed properly.
> 
> No wonder the sticker prices on new vehicles keep going up.




Incandescent lamps burn out and i've seen cars with burnt out brake/tail lights, and that can be dangerous. LEDs are much more reliable. And they illuminate instantly.


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## cland72 (Aug 24, 2015)

poiihy said:


> Incandescent lamps burn out and i've seen cars with burnt out brake/tail lights, and that can be dangerous. LEDs are much more reliable. And they illuminate instantly.



I get that, but how often does it happen? In my opinion, not often enough to justify increasing the cost of a vehicle by $1000 or however much to change the design to LED taillights.


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## PhotonWrangler (Aug 24, 2015)

It's not that it happens often, but when it does, you could get a ticket or cause an accident.


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