Strobing LED car lights - Page 1
Forum section: electronics / general

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: June 02, 2018, 11:09:29 pm
content: OK, not the weird ones underneath the car that make the road glow an eerie green but the tail/rear lights and side/running lights the use LEDs and are becoming more and more prevalent.I have a problem with them. I mean a real problem. The thing is that I can see them strobing. I can even discern the duty factor. To me, they are an "attractive nuisance". I'm drawn to them like a moth. I'll tell my wife, "that car five cars ahead has strobing tail lights". I keep looking at them. At night, on-coming traffic with strobing side/running lights are worse. They play tricks with my eyes - the closer the car gets it seems that it is erratically moving. Very dangerous. Now, I know some cars have LED lights that are continuous and I understand that there could be a minor cost saving but it's inexcusable for Jaguar, Cadillac, Lexus etc to use strobing LEDs.Why don't the manufactures rectify them?Do you know if your lights are LEDs and, if so, strobe (and the duty factor)?Do you care?Am I the only person who sees the strobing?[I have the same issue with the aviation warning lights on top of transmitter towers etc, too]

author: jmelson
author_rank: Super Contributor
timestamp: June 03, 2018, 12:13:35 am
content: Quote from: JohnnyMalaria on June 02, 2018, 11:09:29 pmI am generally aware of lights that strobe, but it isn't a real problem for me. (I am aware of the flicker on old movie projectors, too.)When there isn't complicated traffic to deal with, I often "play" with them by flicking my vision across them and seeing a string of dots.Jon

author: tooki
author_rank: Super Contributor
timestamp: June 03, 2018, 01:57:46 am
content: Quote from: JohnnyMalaria on June 02, 2018, 11:09:29 pmIt is not just you. I notice it, and find it incredibly distracting.For further reading on the issue, the key term is the “flicker fusion threshold”.

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: June 03, 2018, 02:08:42 am
content: Quote from: tooki on June 03, 2018, 01:57:46 amThank you - I'll waste the next hour or two reading up on itI can also "shake" my eyes rapidly from side to side. I first noticed it when I was about 10. It's pretty cool if I'm bored walking down the street at night - the streetlamps make streaks all over the place. Same with LEDs on electronics in a dark room, stage lights at a concert and watching a CRT TV (which is what I have) This "ability" became my tell that I'd had too much to drink since I couldn't wiggle them.No idea what the evolutionary benefit of this genetic mutation is, though.

author: james_s
author_rank: Super Contributor
timestamp: June 03, 2018, 04:06:59 am
content: I notice it too and it's extremely annoying. The same is true of many LCD monitors that use PWM dimming on the backlights. I've had people tell me I'm full of crap and the human eye can't perceive flicker beyond a few tens of Hz which is frustrating since I clearly can. It's not me trying to be superior, in fact I wish I couldn't see the flicker because it's annoying.

author: Halcyon
author_rank: Unknown
timestamp: June 03, 2018, 04:07:45 am
content: I don't know of any definitive sources and this is purely my opinion, but I would suggest that some strobing is actually desirable, especially in the peripheries of your vision. It makes the light much more noticeable than it would be if it were just static.

author: Brumby
author_rank: Unknown
timestamp: June 03, 2018, 04:22:49 am
content: There's "noticeable" and there's "distracting".Having said that, though, there is certainly a case for lights that aren't completely static. I know I have checked a blind spot just at the moment a traffic light changed from green to amber and when I looked forward again, I lost the traffic lights. When you have sodium vapour street lighting the amber traffic lights completely disappear into the scene until you re-scan to find the traffic lights you know are there. I haven't had any traffic issues because of this, but it can be unsettling.What this does illustrate is that we, as humans, tend to notice changing elements more readily than static elements in any given scene.However, when something is so attention-getting that it distracts from the road - something is wrong.

author: glarsson
author_rank: Frequent Contributor
timestamp: June 03, 2018, 08:54:06 am
content: Quote from: JohnnyMalaria on June 03, 2018, 02:08:42 amMy eyes also have this feature. Before this post I have never met, or known about anyone, that could do this.It is easy to freak people out by looking them straight into their eyes and start shaking my eyes at them.Btw, I also find pulse width modulated (strobed) lights in traffic to be highly distracting.

author: babysitter
author_rank: Frequent Contributor
timestamp: June 03, 2018, 09:17:04 am
content: Quote from: glarsson on June 03, 2018, 08:54:06 amThis! ^ My dad even called colleagues to see it when he realised I can do it...Also, I find it distracting, too - but it was already in my teenage time to play "Is this LED multiplexed or not" by moving my eyes and see if there is a continous or shortdash line.

author: Benta
author_rank: Super Contributor
timestamp: June 03, 2018, 03:20:22 pm
content: A thing to keep in mind about the human eye is, that the peripheral vision is much more sensitive to flicker than the central vision. If, for instance, you see a flourescent tube out of the corner of your eye, you'll see the flicker, although it's 100 or 120 Hz. If you look at it directly, you normally won't notice it.I can't say whether the car lights flicker is made that way on purpose, or if it's just bad design.

author: Yansi
author_rank: Super Contributor
timestamp: June 03, 2018, 03:32:59 pm
content: It certainly is a cheap design. Slow automotive protected switches for the LED strips, that can't handle higher PWM frequency, without heating up excessively and blowing up.Just like I was pissed atVND7020AJ, as it is completely uncapable of doing any reasonable dimming for lights, not mentioning using it for an inductive load (motors, actuators) which is just not possible.Y.

author: amyk
author_rank: Super Contributor
timestamp: June 03, 2018, 04:36:03 pm
content: I can also see a similar distracting phenomenon with sequential-colour projectors: moving my eyes across the image results in distinct bands of colour.

author: james_s
author_rank: Super Contributor
timestamp: June 03, 2018, 05:13:18 pm
content: Quote from: Brumby on June 03, 2018, 04:22:49 amThis reminds me of another related item, the modern generation of police car light bars are LED based and *extremely* bright. I drove uncomfortably close to a police officer who was standing near his patrol car one night because I simply couldn't see him next to the blinding glare of the flashing light bar. I was only crawling along and squinting into the darkness trying to see where I was going and suddenly he happened to stand between the light bar and my eyes. I can see the high brightness having benefits in strong sunlight but I cannot figure out why they don't have a night dimming mode. There is certainly such thing as too bright.

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: June 03, 2018, 05:16:16 pm
content: Quote from: Benta on June 03, 2018, 03:20:22 pmBut I'm not normalI see this in my central vision. I only have to move my eyes a couple of degrees in any direction. An equivalent would be scanning a 5cm object about 50cm away - pretty much like reading a forum on a laptop display.Designing things to flicking purposely in the peripherial vision is very sensible - it certainly does get your attention but not in a distracting way.I think it's just cheap/crap design.

author: Benta
author_rank: Super Contributor
timestamp: June 03, 2018, 06:40:53 pm
content: Quote from: JohnnyMalaria on June 03, 2018, 05:16:16 pmI'm inclined to agree with you.

author: Brumby
author_rank: Unknown
timestamp: June 04, 2018, 09:05:14 am
content: Quote from: james_s on June 03, 2018, 05:13:18 pmI had exactly the same experience with a roadside assistance vehicle on a moonless night. I used a bridge underpass and when I came up the other side, here was this vehicle with it's amber light roof bar in full blinding mode. What made this worse was the fact that (at the time) the underpass had no lighting, so you were just driving on car lights. When I came upon the assistance vehicle I couldn't seeanythingelse other than these lights. There could have been a Mack truck in the middle of the road and I would not have seen it. I was very glad I knew the road.

author: Halcyon
author_rank: Unknown
timestamp: June 04, 2018, 09:11:01 am
content: Quote from: james_s on June 03, 2018, 05:13:18 pmThis is on purpose. You would not believe how many people don't notice emergency vehicles, even at night. "Takedown" lights are also deliberately bright so a potential bad guy can't see the Police officers and take a well aimed shot while they are sitting in the car.

author: Red Squirrel
author_rank: Super Contributor
timestamp: June 04, 2018, 11:24:35 am
content: I hate this too. I've even seen strobing headlights! Why can't they use voltage/current regulation instead of pwm?My real pet peeve though is those ridiculously bright blue headlights. They seem to come out in droves more and more each winter. There really needs to be regulations on colour temperature and lumens for head lights. Maybe also specify they need to be constant lit and not strobing.

author: Halcyon
author_rank: Unknown
timestamp: June 04, 2018, 12:38:21 pm
content: Quote from: Red Squirrel on June 04, 2018, 11:24:35 amThere are (in Australia). It is known asAustralian Design Rule (ADR) 46/00it goes into a lot of technical detail. Most aspects of motor vehicle design here has an associated ADR.I'd be surprised if most countries don't have something similar.

author: Whales
author_rank: Super Contributor
timestamp: June 04, 2018, 12:46:21 pm
content: Flickering LCD backlights are evil. My pwm'd torch is bad enough, I'm glad I have not noticed this on cars yet.FWIW: it's actuallyless efficient to run LEDs with PWM than it is to run them with PWM + diode + L + C (a buck converter). LEDs provide more lumens per watt (higher efficiency) at lower power levels, PWMing avoids this and runs them at 100% during the high part of the cycle.

author: Benta
author_rank: Super Contributor
timestamp: June 04, 2018, 05:03:29 pm
content: Quote from: Red Squirrel on June 04, 2018, 11:24:35 amI suppose you are referring to Xenon headlights. Those are running with an arc at appr. 600 V and are definitely not flickering.Xenon headlights give excellent light due to superior optics, provided they are OEM. In the EU, this means that they MUST be equipped with automatic level adjustment and washing mechanism and adhere to color and lumens regulations.The problem is, that there is so much aftermarket crap out there without these functions and inferior optics that it's annoying other drivers.

author: tszaboo
author_rank: Super Contributor
timestamp: June 04, 2018, 05:13:49 pm
content: Future historians will describe the 21 century like this: "They already had air conditioning, but it wasn't designed well, and nobody could set it to the correct temperature."The same with LED lights. We have them, they are mostly bad. To much glare, to low PWM frequency, not enough dispersion. Blinking LED bicycle lights should be outright banned. I see it from a kilometer, that something is there, but when I am at 30 m, I cannot determine the direction, the speed or anything how the cyclist is moving. Or how far away is he.

author: Red Squirrel
author_rank: Super Contributor
timestamp: June 04, 2018, 05:41:37 pm
content: Quote from: Benta on June 04, 2018, 05:03:29 pmYeah some are Xenon/HID and don't flicker, they're just way too bright and the blue colour makes them hard on the eyes. I have seen some similar bright blue lights that flicker but they are most likely LED. I see some that are OEM now, but they're just as bad.Worse is when you don't see it coming and get flashed by it from an oncoming car that was behind another car, it's like when an airline pilot gets lasered.

author: james_s
author_rank: Super Contributor
timestamp: June 04, 2018, 06:18:41 pm
content: Quote from: Halcyon on June 04, 2018, 09:11:01 amWell then it's stupid, because if you're going to have the lights so bright that it blinds people driving by then you should close the road. What good does it do for me to notice the emergency vehicle if I can't see the police officer standing in the road next to it? The takedown light is another matter, it isn't aimed at oncoming traffic.

author: capt bullshot
author_rank: Super Contributor
timestamp: June 04, 2018, 07:00:20 pm
content: Quote from: JohnnyMalaria on June 03, 2018, 02:08:42 amYes, I can see the strobing too. I'm used to it, yes it's very noticable, but don't feel distracted by those lights. Others complain more than me, so I think these lights should be banned.And I can also do the "eye shaking" - it's quite interesting to watch multiplexed LED displays while shaking the eyes and trying to figure the multiplex arrangement? Is this an early sign that one is born as an EE?I never thought of this being a special feature that others don't have, most people just appear to be not interested in figuring out multiplexing schemesUsing my glasses (I'm rather badly shortsighted), I can also do spectral analysis of light sources - it's easy to tell a RGB LED from a "white" one by looking at through my glasses at an angle, not straight. This can be quite distracting if you don't know and not used to it, an yellow light that is made up by mixing a red and green LED seen as a red and a green one slightly moved apart.

author: Red Squirrel
author_rank: Super Contributor
timestamp: June 04, 2018, 08:26:36 pm
content: On similar subject I can actually make up the RGB colours on certain projectors (DLP I think?) if I move my head fast. It's kind of trippy.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: June 04, 2018, 09:23:39 pm
content: Quote from: Halcyon on June 04, 2018, 09:11:01 amThese things are a major nuisance in residential areas, where they can make sleep impossible for houses hundreds of yards around the police car. Even with window blinds the flashing still gets in to bedrooms. Thing is, if a few hundred people have to drive to work and operate machinery dog-tired the next day, what does that do for the overall accident risk? An example of statistical skew, since such accidents are unlikely to be attributed to the actual cause.In Scotland the forces have been under pressure to stop using these over-bright lights because of public nuisance.I think most have.

author: tooki
author_rank: Super Contributor
timestamp: June 07, 2018, 08:02:09 pm
content: Quote from: james_s on June 03, 2018, 05:13:18 pmNot only are they hella bright, they are a) point light sources, rather than the much more diffused ones of old bulbs with lenses, and above all b) the LEDs’ light is essentially monochromatic, making it far more noticeable, but also much harder on the eyes, since red and blue do not focus the same. There’s no green and yellow light leaking through the color filters that we could focus on. So our eyes struggle to focus on the red and blue because it’s physically impossible to focus on them simultaneously. Additionally, in people like me who wear thick eyeglasses, at the periphery, the prism effect of the lenses causes the red and blue to shift apart, which is highly distracting.I’ve wondered how many accidents are caused by the excessively bright LED police lights, honestly...