Hacker News Reader

Comment by manmal | Hacker News Reader

I don't like the light given off by LEDs. It looks unreal/surreal to me, and makes me uneasy if it's the only light source. Especially the blueish ones. Before installing them I was very enthusiastic about all the benefits of low power lighting, but now I want to switch back to halogen bulbs, or at least very warmly colored LEDs.

I'm oversensitive though. E.g. slightly flickering energy saving lamps make me dizzy, exacerbated by ACs making my eyes dry (hello, Ikea).

I hope those nano-coated regular light bulbs will become a thing.

View on HN

The light from good quality LEDs should be indistinguishable from halogens, and better than any CFL. I've replaced my entire household with Philips 2700k LEDs of various types and they are excellent.

Poor quality LEDs are awful - the 50/60Hz flicker/strobe effect that many produce is very annoying and fatiguing and it doesn't surprise me that they're considered a health hazard.

Try quality LEDs and you won't regret them.

Nice, thanks for the tip. The "Choose your LED color" on the Philips site is pretty good for showing the difference between color temperature: http://www.usa.philips.com/c-m-li/led-lights/warm-led-light

2700K CCT means that the light from the diode is being mostly absorbed and re-emitted by the yellow phosphor. The lamps people have trouble with are those with a CCT of 4000+K, which emit several times more short-wavelength light for the same perceived brightness.

Incandescent lamps are typically ~2500K CCT

Try quality LEDs suggests that there are reputable manufacturers of LED products. Last time I tried Philips Greenpower, they said "40W!" yet the Kill-a-watt showed ~30w and it was nowhere near as bright as an 18w unit some cheapo Chinese maker had. General Electric markets a 7w UV LED - there's one 1W UV LED, and four 1.5W white LEDs, behind a fake woods glass. Yet neither the bulb nor packaging makes note of the white LEDs. It instead says directly on the bulb "395nm UV Light" as if that were all it emitted.

Quality certainly doesn't mean Brand-name in this day and age of unscrupulous law-buying companies.

watt is a poor measurement for measuering the quantity of visible light. Well I mean just knowing the lumina of a bulb doesn't help since it's a subjective measurement and can change depending on the kelvin of the light. For myself I usualy look for 600-800 lm and around 2600K well for the bath I go lower and only take a look at 400lm. As said measuring the light is extremly subjective for different kinds of people

"watt is a poor measurement for measuering the quantity of visible light"

Actually, it's a great measurement if you only work with the monochromatic ones. Knowing the LEDs efficiency at bin testing conditions will tell you what to expect - E.G. high-bin 3w 460n LED with 50% efficiency at 3w drive and typical operating temperatures (~70C junction temperature) means you can expect 1.5W of light. We toss in Avogadro's constant and a couple other formulas, do some multiplication, and suddenly we know roughly how many photons are being put out.

This gets harder with white LEDs as one must figure out the relative percentage of each wavelength comprising the light, basically forcing you to do the math a few hundred times over, but it's still rather reliable. I just do rough calculations in my head for White LEDs.

Not only that but about 5 years ago we replaced most of the house with Philips LED lights, most of them failed/are failing by now (they start by getting a darker patch in the bottom of one of the tubes and then it slowly spreads out and the light shuts off completely).

5 years for a product that is advertised as lasting for decades as this usage rate.

"they start by getting a darker patch in the bottom of one of the tubes"

Tubes? Presumably you're talking about CFLs, not LEDs? 5 years ago, household LED lamps were still in their infancy and were really expensive.

My experience with CFLs was pretty similar to yours. They didn't last, and dimmable ones especially would often fail within months. And the quality of light from fluorescents was never all that good anyway.

But out of around 25 Philips LEDs I've installed, most of them dimmables, not a single one has failed or had any problems so far. The oldest ones were installed around a year ago now.

The Philips A19-style bulbs kinda look like futuristic tube-ish light bulbs. It's just a circular ring of LEDs inside. One section goes out, then the next, in a cascading failure.

And yet, here I hold some cheap (literally $0.99 each) 9w Chinese LED bulbs, several of which have been operating 24/7 for a couple of years, and still working just fine.

So much of a crapshoot.

I'd recommend you look for high-CRI LED bulbs – I've had similar reactions to yours but I'm satisfied with some of the better/higher CRI bulbs(color rendering index https://en.wikipedia.org/wiki/Color_rendering_index). They tend to be harder to find, but they're out there. GE Reveal bulbs are higher CRI, for example and I've found other brands through some specialty LED dealers that almost match halogen bulbs.

Parent is correct, high CRI[1] is what you want to look for. I'm embarrassed to reveal how much time and money I've spent down this rabbit hole and ultimately went back to halogen.

As you research, you'll discovered that there is in fact more to the single CRI value. It is actually an average measurement of a range of different colors.[2] R9 in particular is the one that is hardest for LEDs to reproduce. Some manufactures goose their CRI value by getting high scores for the other values even though their R9 or R13 (skin tone) is poor.

[1] https://en.wikipedia.org/wiki/Color_rendering_index [2] http://www.lightology.com/img/howto/cri/cri_2.jpg

Be careful, though. Soraa, for example, makes fancy LEDs with CRI 95, and they use violet LEDs behind the phosphor. The problem is that the phosphor lets a decent fraction of the source light through. Soraa even has a nice graph on their spec sheet, and it has a violet peak.

Also, a neat fact: all CEC qualified LEDs are high CRI.

(P.S. I bought a GE Reveal once and it had the worst color fidelity I've ever seen. Some normally bluish surfaces were distinctly green. I don't understand how it has a high CRI.)

GE has been busted by myself falsely advertising their UV LED bulbs. In fact, I'm currently looking for more people that bought these A19-style UV Black Light bulbs from GE so we can start a class-action suit for false advertising and unfair competition.

In short, I wouldn't trust GE for LEDs. In fact, I'm so disillusioned with almost every company out there (Cree, Philips, GE, Sylvania) that I've simply gone back to building my own lights for my specific purposes. I can't trust any of these companies to be accurate or truthful in their marketing.

> that I've simply gone back to building my own lights for my specific purposes.

Is this what your username references?

Yup. I design my own LED units, have a company called SinkPAD (I think it's Adura, now) make the boards, then I populate the boards myself.

Maybe you could point me in the right direction. I'm looking to construct a panel that can make it look like day, but has infinite dimming.

Making daylight is easy enough. The Nichia 219B LED in 5000K R9050 (CRI 90+, R9 50+) is beautiful. 12-18 of them will comfortably make over 5000 lumens without having to be driven especially hard. It's not terribly hard to come up with options to wire them up and heatsink them properly either.

What I haven't been able to find is a suitable power supply and driver. I want to plug it in to 100-240V and have a dimmer knob giving me 5-5000+ lumens via current regulation, not PWM, though very fast (> 10kHz) PWM might be acceptable. Yes, I'm aware the tint will shift a bit through the brightness range without PWM. I'm OK with that.

"I'm looking to construct a panel that can make it look like day, but has infinite dimming."

Infinite? Not happening, but if you want to get CLOSE, your best bet is in a simple benchtop voltage and current regulator. I use four Nichia 219B LEDs to light my 55-gallon aquarium, are you SURE you really need 5,000 lumens? You could probably get away with just four of those, a fixed 12V power supply with adjustable current, and be done with it, they're ungodly bright and a quad of those can match up with the Cree MK-R.

It need not be truly infinite or stepless as long as it has hundreds of steps. I want to dial in the ideal level, rather than pick from say... 10 options.

I'm sure I want over 5000 lumens. When I want my room well-lit to promote a sense of alertness and compensate for shorter days in winter, my best current option is a flashlight that produces about 4200 lumens bounced off the ceiling. No, that's not one of those BS marketing numbers: the light is a Jetbeam T6, which in stock form uses four Cree XP-Ls powered from four 18650 Li-ion batteries. Independent tests, including my own have found its claimed performance to be accurate. I swapped the XP-Ls for Nichia 219Cs (5000K, CRI 80+, R9 unspecified) and measured about a 2% loss of output, but increased intensity. This works as a room light, but requires an external cooling fan to run on high for longer than about 10 minutes (it has a thermal sensor and stepdown), and the batteries can only keep up with that output for a bit over an hour. 219Cs are more efficient than 219Bs and can be driven much harder, but aren't as pretty. Even the recently-released R9050 (CRI: 90+, R9: 50+) version just doesn't look as nice to me.

Four 219Bs definitely can't produce 5000 lumens. The 90+ CRI versions peak at about 600[0], but I don't want to run them at peak output; the harder they're driven, the stronger the spectral peak of the underlying blue LED. I want to run them at about 300lm/ea. 12 of them will get me that, but I'd actually rather have more than 5000 lumens.

Thanks for responding. I was hoping for an off the shelf driver, but it looks like I'm going to be improvising a bit more.

[0] http://budgetlightforum.com/node/27652

Here's an idea. Get a single 50w COB LED that can match or get close to the Nichia (they exist, I'm sure of it.) Actually, Nichia has some of their own that do match - http://www.nichia.co.jp/en/product/led_product_data.html?typ... and http://www.nichia.co.jp/en/product/led_product_data.html?typ.... Then you just need a simple heat sink, and fixed voltage power supply with adjustable current. Those aren't too expensive, but you're still looking at roughly ~$80 in total BOM.

I thought about getting one of those bigger arrays, but I'm concerned that the light they produce may not be as pretty as the 219B even if they have the same color temperature and CRI on paper. The 219C, for example is not, though it's still very nice and capable of quite a bit more output. Output per emitter and overall efficiency aren't major concerns for me: we're talking about around 90W for 6300lm driving 18 219Bs at 1500mA each.

It's also difficult to find the 048Z available in single quantities. I didn't find the R9050 version on Octopart, Other versions cost $50-60, while 219Bs in several tints are readily available from suppliers of DIY flashlight parts for $3/pc. Getting 219Bs and triple or quad copper MCPCBs is easy, and they can be configured for any multiple of about 3 volts, while the 048Z requires a 50 volt power supply.

I was expecting to spend over $100 when all is said and done.

"It's also difficult to find the 048Z available in single quantities"

Just ask Nichia for an engineering sample. :) Boom, free sample if they've got one for you to utilize. I don't know how many Cree, KingBright, Nichia, Osram, and Epistar LEDs I've got just because I ask to test them.

As for the 50V power supply, it'll run on a 48V 1.25A driver. You'll be fine and those are about $20 each.

I have hundreds of dollars worth of flashlights I got by offering to write reviews, but asking for an engineering sample never crossed my mind. I may have to try that.

If you point out to them reviews you've written (some of them mentioning their LEDs favorably) you'll get the engineering sample no problem, I imagine. They like people that promote their products and bend over backwards to get them tiny things that cost them far less than what they're going to get in potential advertising.

LEDBenchmark [1] does a good job with their own spectrum and flicker graphs. So far, the LED bulbs I have gotten based on their results have been good.

[1] http://www.ledbenchmark.com/

The cheap bulbs I found at Costco are high CRI. I think it was these in a smaller package: http://www.costco.com/Feit-LED-A-Lamp-60W-Replacement-Soft-W...

That's a great price point for high CRI bulbs – but the reviews on the page you linked to make them sound massively unreliable!

They might be unreliable, I've had some bad luck with Feit bulbs myself in the past. But if the price is right it might be worth the gamble, it was in my case. My bigger fear is that they're stretching the truth with their CRI number, I don't think there's any independent verification of their claims. There might also be some degradation over time as the phosphors wear out.

Strange. CFLs feel surreal to me but I find LEDs very... Stable feeling?

With CFLs, for me, it depends. The cheap or worn out ones tend to flicker ever so slightly (at 50hz where I live), and that's unnerving.

Reply on news.ycombinator.com