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What Happened to the 100000 Hour LED Bulbs?

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Re: What Happened to the 100000 Hour LED Bulbs?

#491

Post by yeutterg »

pistachiopro wrote: post #473
yeutterg wrote: post #428

Earlier quoted context omitted.

I've tested a bunch of bulbs for flicker with a handheld flicker meter and with a photodiode connected to an oscilloscope. It's funny that some of the bulbs out there claiming to be "healthy" have terrible flicker. One product from Soraa was flickering at over 50%, almost as bad as the cheapest/worst LED bulbs you can buy. I don't have a database, but I can say that most (but not all) filament designs are terrible fo…

Thanks to GP for the links, I completely missed that previous thread! And, yeah, I tried that Soraa healthy bulb, and it was shockingly bad, given how it was advertised. Even the regular Soraa bulbs were disappointingly flickery, though less so. Also, just looking at the pattern it makes on my phone's rolling shutter, the wave is quite saw-toothed, and I wonder if that makes it worse? I have some Ikea candelabra bulb…

The Soraa bulb looked pretty sinusoidal on my scope when I tested it briefly. But it's a lot of flicker regardless.

What's interesting is that the bulb seems to have a nice build quality (from the outside, I didn't open it) and is quite heavy. I suspect they are putting a BIG heatsink in there, as violet pump phosphors tend to degrade quickly.

The other thing that irks me about this product is the "zero blue" messaging. Yes, I can confirm the spectrum looks like what they are advertising, with a peak around 415nm, almost nothing between 440-490nm, and then all the rest of the colors from green to red.

But, green light is just as bad as blue for sleep! The ipRGCs are sensitive to both blue and green (up to around 600nm) This bulb has a lot of green, more than a lot of other light sources. It also has a very unpleasant greenish color (IMO) and low-ish CRI, around 78 on the bulb I tested.

Is it better than a normal 600lm bulb for sleep? Yes. Is it novel? Yes. Is it good in practice? I don't think so.

Re: What Happened to the 100000 Hour LED Bulbs?

#492

Post by yeutterg »

nitrogen wrote: post #466
yeutterg wrote: post #430

Earlier quoted context omitted.

Agreed. Most car manufacturers' LEDs flicker (just look at any slow-motion video, such as those on Top Gear or The Grand Tour), but GM's are at a much lower frequency that is visible if the vehicle is in motion, or you are in motion.

I always wondered if anyone ever tried to encode information into the flicker pattern of LED tail lights. I can think of a lot of uses, good and bad.

Some people are talking about using LiFi or high-speed IR communication for vehicle to vehicle communication. Seems like a great idea, but you can do it at a much higher frequency than what GM is doing today, so it's not distracting to humans.

Re: What Happened to the 100000 Hour LED Bulbs?

#493

Post by jandrese »

sleavey wrote: post #263
jandrese wrote: post #217

Earlier quoted context omitted.

Why do so many of the bulbs run hot? Like so hot you can't hold them in your hand if they were on when you unscrewed them. Isn't this a lot of wasted energy?

I think they might have began quoting the LED lifetime on boxes, which is still true, but in reality something else in the bulb usually breaks before the LEDs themselves. I guess manufacturers have either taken it upon themselves or have been forced to reduce the quoted lifetime since the famous 100,000 hours marketing.

Or they quote the lifetime figure for a single LED, but then wire up a dozen or more in series to make the light. Any one of them fails and the whole assembly goes dark.

Re: What Happened to the 100000 Hour LED Bulbs?

#494

Post by upofadown »

tlb wrote: post #101
vvanders wrote: post #46

Earlier quoted context omitted.

Isn't that a function of voltage and not modulation? There might be a cost argument, I'm not sure if solid state step-down DC-DC converters are cheaper than good old cheap transformers.

Yes, it's entirely a function of voltage. But the safe limit for DC voltage is lower for two reasons: - A shock from a DC supply will cause heart fibrillations at lower voltage than AC, because of the way muscles receive signals from nerves - An electrical arc from a DC line will burn continuously, while an AC arc tends to self-extinguish at each zero-crossing. So in practice, 120 VAC or 48 VDC are the limits for hou…

>A shock from a DC supply will cause heart fibrillations at lower voltage than AC, because of the way muscles receive signals from nerves

That is opposite to my understanding. The extra shock hazard of AC vs DC was an argument used against AC power distribution back in the day. The 50V limit is to prevent shock altogether.

Re: What Happened to the 100000 Hour LED Bulbs?

#495

Post by retSava »

yeutterg wrote: post #428
arm wrote: post #385

Earlier quoted context omitted.

In the huge HN thread here¹, yeutterg mentioned² their Bedtime Bulb: > “ I am on a mission to make lighting healthy. That's why I made Bedtime Bulb: https://bedtimebulb.com/ It has the lowest flicker I've ever seen in a bulb form factor—even less than those claiming to be "flicker-free." ” In addition to that, a few other database sites that test for flicker were mentioned here³. ―――――― ¹ — https://news.ycombinator.c…

I've tested a bunch of bulbs for flicker with a handheld flicker meter and with a photodiode connected to an oscilloscope. It's funny that some of the bulbs out there claiming to be "healthy" have terrible flicker. One product from Soraa was flickering at over 50%, almost as bad as the cheapest/worst LED bulbs you can buy. I don't have a database, but I can say that most (but not all) filament designs are terrible fo…

> flickering at over 50%

what does that mean? Duty cycle is 50%, frequency at something Hz? Not being snarky - curious whether there is some kind of standard that your tool compares against.

A duty cycle 50% (or any percent really) isn't bad in itself, it's the frequency that is the culprit. Too low PWM freq and you'll notice it.

Re: What Happened to the 100000 Hour LED Bulbs?

#496

Post by manmal »

dombesz wrote: post #460
manmal wrote: post #267

Earlier quoted context omitted.

I only buy Philips bulbs for this very reason, or from brands that advertise being flicker-free. With iphones, slow motion mode also makes the flicker very visible without the need to transfer to a PC. Visible light impulses influence brain wave patterns (e.g. [1]), and it might not be beneficial to look at pulsed light with a frequency that is not well researched. Same thing with screens, most LEDs are dimmed with p…

Very good points here, I would add that 99% of the monitors are also flickering when you dim their ligth. This is why i started using the iris[1] app on my laptop. Keeping the brightness at 100% in the hardware settings will eliminate the flicker, then iris dims the lights from your graphic card. I can work without eye oain thanks to this method. - [1] https://iristech.co

Oh, I had been looking for something like this for the desktop, thanks for mentioning it!

On iOS there’s a setting buried deeply in accessibility settings, I think it’s called white point correction.

Re: What Happened to the 100000 Hour LED Bulbs?

#497

Post by manmal »

pistachiopro wrote: post #287
manmal wrote: post #271

Earlier quoted context omitted.

Dimmable LEDs are not automatically flicker-free. My father had very cheap dimmable ones, and I complained at every visit about the strobe effect until he bought flicker-free ones. Most dimmers work via pulse width modulation [1], i.e. the power supply is switched on/off in a different interval (more off time means lower brightness). A true flicker-free dimmed LED has to be dimmed in an analog way (probably only feas…

I can't find the source right now, but I read that the fastest cells in the visual pathway can respond at a bit under 500Hz. Part of the reason the ieee suggests a minimum PWM frequency of 3000Hz is, for signal processing reasons I don't fully understand, that's the highest frequency the brain could likely detect, given 500Hz "sampling hardware."

You might still get strobe effects where your 500hz sensing nerves eg get a 400hz signal from a 20khz source.

Re: What Happened to the 100000 Hour LED Bulbs?

#499

Post by DoctorOetker »

AngryData wrote: post #419
jandrese wrote: post #217

Earlier quoted context omitted.

Why do so many of the bulbs run hot? Like so hot you can't hold them in your hand if they were on when you unscrewed them. Isn't this a lot of wasted energy?

Partly because they are running tiny cheap power supplies pushed near their limit, and also because many of the actual LEDs they use aren't nearly as efficient as they could be. Also available surface area, in order to fit in most standard bulb locations they need to be small leaving little room for adequately sized heat fins.

yes theres multiple kinds of inefficiencies concerning the external circuitry etc, but there is also the intrinsic inefficiency of current LEDs: some of the high energy photon are downcoverted to a low energy photons by phosphors, so there is non-radiative (heat) generation in the phosphor itself. In theory it is perfectly possible to use "quantum cutting" i.e. 1 photon -> 2 photons instead of 1 photon -> heat + photon. There is quite a lot of research on quantum cutting phosphors, both for LED's and for VUV excitation etc, so these higher efficiencies will probably come, but I don't know how far out in the future. If someone knows of commercially available quantum cutting phosphors (or products using them) I would be very happy to know about them for some physics experiments...

Re: What Happened to the 100000 Hour LED Bulbs?

#500

Post by telchar »

mrb wrote: post #270
telchar wrote: post #248

Earlier quoted context omitted.

Perhaps dimmable LED bulbs would be better in that regard? The LED dimmers on the market use a very high rate PWM (afaik) to prevent/minimize flickering at low brightness. I would guess that the dimmable bulbs are designed to work well with intermittent power and so wouldn't have the same problem. Of course it's still hit or miss, compatibility between bulbs and dimmers seems to be very hard to judge without testing…

In my experience, dimmable bulbs are no better. Most of them still suffer from the 120 Hz strobing effect. That's because even though they might PWM at 1-10 kHz to control the dimming function, when A/C voltage crosses zero, the "on" state of the PWM can still be a lot dimmer than the "on" state during the A/C voltage peak.

I would think a good LED would need something like a full wave rectifier with a good smoothing circuit to minimize flicker. I bet a lot of the bulbs on the market cheap out on the electronics though.
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