But that practically singular investment in automotive optical engineering and innovation is let down by the low frequency PWM driver baling wired into the final design to cut cost by perhaps a dollar or two.
And one reseller told me - "Well, they should be shielded". Practice far from granted if even the problem is not known.
What % of people are sensitive to this? Any medical documentation? Is NHTSA aware?
If you wouldn't mind reviewing https://news.ycombinator.com/newsguidelines.html and taking the intended spirit of the site more to heart, we'd be grateful. The idea is: if you have a substantive point, make it thoughtfully; if not, please don't comment until you do.
Does it specify minimum LED refresh rate somewhere? Or is it lacking that today?
If you're old enough, you may have seen the science fiction children's show "Captain Power." The LED tail lights remind me of the target strobe meant to trigger the accompanying toys.
Of course if you're old like me, you probably only watched an episode to see what Lightwave3d was capable of, but ..
See saccade:
They are all "for offroad use only", which is the biggest scam
https://lumileds.com/austrian-drivers-can-enjoy-road-legal-p...
A few years ago the EPA clarified that when they said “off road use only”, they meant in machines that were never intended to be on a road. So, aftermarket shit designed for a lawnmower, cool. But if you’re designing for a vehicle that was originally designed for the road, you have to stick to EPA regs. This killed a lot of those “off-road use only” disclaimers, but it also panicked the amateur racing community because they tend to use modified road cars. I’m not sure how they worked it out with the EPA, but I don’t hear them complaining any more, so I assume they did.
All on the basis that “lol humans don’t notice the flicker”? Uh, okay, but animals? The 99th percentile humans? Subconscious effects on fatigue (that you mention)?
Seems penny-wise and pound-foolish.
It's more about economizing the power supply package and heatsink integrated within the bulb or lamp assembly.
That’s not how it works. When charging, the alternator will put more load on the engine and that will increase fuel input to keep rpm up enough to keep the engine from stalling.
Overall, every vehicle designer will seek to minimize any and all loads (even small ones).
Worst is when they remove the spare tire, grrrrrr.
Mass produced cars have reached the point that a $0.50 saving per vehicle is worth designing and building for. When you reduce the current draw from something that is always-on (like headlights) you increase the life of the LED, you can reduce the gauge (size) of the wires to the lights, you can reduce the size of the alternator, you can load the alternator less, which means increase the service life of the alternator belt and idlers, and (in theory, at least) decrease fuel consumption.
All of these are tiny, tiny efficiencies, but they do add up.
While it might seem penny-wise and pound-foolish, imagine following this same logic for all systems in a modern vehicle. This is why even such a "rugged offroad" vehicle as a Jeep Wrangler has a plastic clutch slave cylinder (weight and cost savings) and why the headlights will dim in virtually all vehicles if you turn on every single electrical device that draws current (the wires are not sufficient gauge for everything to draw max current at the same time).
They're saving actual money on every vehicle built, which is what they care about.
LEDs can be done similarly, but an LED matrix headlight just controls which rows of LEDs are lit up (e.g. the Samsung PixCell light that Tesla uses on the Model 3/Y). This is where we'll maybe see adaptive headlights, too, though in the case of Tesla I don't believe they've ever been used anywhere in the world, legal or not. Just to write "TESLA" on the wall when you do the Light Show.
The PWM I use at home on an ESP32 is supposed to be in the 1-10 kHz range and I don't see flicker when moving my eyes.
I associate flickering headlights with aftermarket because cars with halogen headlights use low-frequency PWM to regulate down high system voltages to 12V. So if you install aftermarket LED kits on those cars you are going to see a PWM of ~90Hz which is awful.
That can't be right. Cars are primarily 12VDC.
Here's a random video I found demonstrating the phenomenon. https://www.youtube.com/watch?v=82tFav8oGFI
Not really on headlights I guess so I might be off-topic. And although I understand how some people can find it annoying, I don't really mind them. But I can definitely see the flicker and can compare the duty cycle between different cars.
The usual ~200kHz PWM is cheaper, more reliable, smaller, and usually more powerful than anything you can build on the ~100Hz. Besides everybody sells chips for ~200kHz, but finding anything that can operate at ~100Hz is a challenge.
I can understand cheap household ones using the mains frequency to avoid an AC/DC conversion. But AFAIK, using them on a car is stupid from every conceivable point of view.
Newer construction doesn't install proper fixtures anymore. No more user-replaceable bulbs. Everything is screwed directly into the box and you have to do a minor electrical job on every unit you want to replace.
Surely someone can devise an internal circuit to disable some combination of the LEDs to do proper dimming without relying on PWM.
The luxury days of installing an incandescent bulb that lasts for ten years are gone, lucky to get six months out of "contractor grade" LED products and consumer devices usually don't make it much over a year.
Sure, burns a little less coal, but its not like LED manufacture and shipping is as environmentally friendly as beewax candle production LOL. Overall we're probably worse off as a civilization with LED lighting.
I'm always surprised to read such comments, incandescent bulbs definitely burned out regularly, and the LEDs we have now are more or less as durable in my experience.
I still have a few CFL bulbs that are more than 10 years old (that I keep because their slow warm-up is actually desirable in some cases) and my Ikea LED bulbs are all between five and three years old. One of them (out of 12 I think?) did fail last year, it was four years old.
I think I solved this in my old house. BR40 bulbs. I don't recall the specific vendor but they were very expensive.
The amount of work it takes to get up to the fixture is most of the effort, so I can lean both ways on this one.
I too strongly dislike the lack of replaceable bulbs in newer LED fixtures. It's outrageous how many things in modern construction shave a few cents here and there to get the initial cost down, and the long term costs are enormous. Once the house is sold it's someone else's problem and that mentality is disgusting.
As mentioned elsewhere in this thread, the majority of the population doesn't seem to notice this crap, at least not in a way that affects their day-to-day happiness.
Why not vote for something that sounds good at surface level if you've never perceived that annoying sound or flicker? Why would you even think about it?
Just in general, a lot of things are headed this way, almost as if hubris and bliss compels and perpetuates it.
But they can switch on and off very fast, so if 50Hz is flickery, you can use 500Hz, or 5000Hz. Most microcontrollers have circuitry for this built in, so you just literally write a different constant into the controller.
I once made an LED dashboard for use in police cars. After it was rolled out, it was discovered that the flicker frequency was interfering with the radio (the only bug ever found in my code!)
My client called me back in to fix it, so I added a zero in the relevant place, and recompiled the code.
£400 for about twenty minutes work.
This is factually incorrect.
LEDs shine at a range of brightnesses. The amount of light emitted is related to the amount of current flowing through the LED, which you are free to control however you want. The cheapest way to do this is to use something like PWM and monitor the average current flowing through the LEDs. However, you can also just use a constant current source, and adjust it to provide the amount of current that you want.
I don't know where the idea comes from that LEDs are only on or off. There's no basis in fact here, as far as I can tell.
1. I'm not sure if there's a better name, but the system where the rear view mirror is a display linked to a camera at the rear of the vehicle in higher end cars.
However, poor (or nonexistent) light source shrouding is also a common factor. Bicycle headlights make a great lower-powered example. Cheap bicycle headlights throw much less light than a car headlight but are painfully blinding due to the exposed light source point. Bicycle headlights that meet StVZO regulations shroud the light source, have decent optical design, are far more effective as headlights, and don't make anyones eyes bleed even when they're flashing.
Early composite car headlights (post sealed beam) received significant design investment involving established headlight manufacturers and worked extremely well. Auto manufacturers brought headlight design in-house by the time xenon and HID headlights showed up in general use; inexperience and cost avoidance gave those lights an undeserved reputation. A lack of regulatory outcomes rewarded that strategy, leading even established composite headlight quality to decline. Light source shrouds disappeared or became ineffective due to poor reflector design.
Headlights on new cars in the US market have declined to the point that they're effectively overpowered cheap bicycle headlights plus extra PWM induced stabbiness, while costing orders of magnitude more as a result of cost cutting. The worst have returned to sealed beam levels of utility, but at least there were aftermarket options to improve sealed beams. Modern aftermarket lights are so bad that it's normal for drivers to install them for malice against other drivers with blinding stock headlights. There really aren't any optically well designed headlights on the US market any more, except for bicycles.
PWM (Pulse Width Modulation) is a technique where the power to the output (bulb) is turned on and off at high frequencies in order to increase efficiency, power handling, and control of the output.
If this on/off switching is done fast enough, your eyes/brain will interpret it as a normal always on light source.
PWM is significantly cheaper and easier to implement vs current source LEDs, so it of course has become dominant in the industry.
When the PWM frequency drops below 120-240hz (cycles a second), some people can start to pick up a strobe like effect from the bulb. This flicker is known to cause additional eye fatigue and can trigger headaches in many.
What's worse is that many aftermarket LED headlights are now using PWM at 60hz. These cheap headlights are often bright blue in order to look modern and impressive. When a car with these installed is behind me at night I have to move my mirror away because the flicker is incredibly distracting and fatiguing.