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Re:Mathematicians Tame Rogue Waves, Illuminating Future of L... by wlesieutre on Wednesday August 23, 2017 @09:47AM (#15081480)
I work at an architectural lighting manufacturer, and yes, they definitely are.

It killed incandescent/halogen first, then CFL. Metal halide (especially high wattage) and linear fluorescent are still hanging on by a thread, but everybody in the industry acknowledges that they're on the way out.

When I was in college (class of 2012) LED lighting was on the rise but the industry imagined they would take over much more slowly than what actually happened. We were still taking about CFLs as something that might come up more than once after we graduated.

Re:Mathematicians Tame Rogue Waves, Illuminating Future of L... by criddell on Wednesday August 23, 2017 @12:15PM (#15082729)
Maybe you can explain something for me. I installed an IOT dimmer to control my bathroom lights which are dimmable LED bulbs. It works, except for one super annoying thing: when I turn them on, it flashes first at full brightness before going to the correct setting. It's so bright, it almost feels like a camera flash.

The dimmer is a Lutron Caseta dimmer and it works nicely with the Echo and Apple Home.

Re:Mathematicians Tame Rogue Waves, Illuminating Future of L... by wlesieutre on Wednesday August 23, 2017 @01:18PM (#15083307)
LED dimming is a compatibility mess. Most commercial buildings don't use 2-wire dimming where you're messing with the sine wave on the hot wire for dimming, instead they give you a clean 120V circuit and tell you the dimming level over some other channel (whether it's wireless, 0-10V analog, or some digital bus), and these tend to perform a lot more consistently. But most residential equipment doesn't work that way because houses don't have the additional wiring for it, so we're stuck with 2-wire.

When you get into 2-wire dimmers where it's chopping up the sine wave to reduce power, everything gets sloppier. The only 100% reliable strategy to avoid problems is buying LED bulbs that have been tested on your specific dimmer system.

Consumer products are especially frustrating because a lot of time the technical specifications are missing important information like whether it's for forward phase or reverse phase dimming. That relates to which end of the sine wave gets chopped off for dimming, and they don't play nicely with each other. Reverse phase is the more common these days, but it doesn't hurt to confirm.

Lutron does a fair bit of compatibility testing and lists their recommended products here: http://www.lutron.com/en-US/Service-Support/Pages/Technical/...

EDIT: I should note that if you're looking at screw-in LED light bulbs you want to search "A Lamp". Bit of industry jargon, we measure things in 1/8 inches (because reasons), so what normal people consider a standard lightbulb is an "A19 lamp" meaning A-series with 19/8" (2.375") diameter.

Re:Mathematicians Tame Rogue Waves, Illuminating Future of L... by ChuckMcM on Wednesday August 23, 2017 @01:54PM (#15083596)
This is spot on.

To put it more simply still; AC light dimmers work by 'turning off' the sine wave part way through the cycle. This works on purely resistive loads (light bulbs) and blows up motors (ceiling fans).

LEDs are direct current devices that run on less than 2V. So they convert the electricity coming in to DC, then regulate it down to their voltage. No amount of 'sine wave chopping' is going to dim them.'

As a result they try to cheat, they try to both convert AC to DC and to measure the incoming sine wave and guess that it is being dimmed by an old style dimmer.

In the GP comment, the engineer chose perhaps poorly. Clearly as soon as power is available the light comes on full, then after the 'dim' setting is measured it adjusts the light level to the 'dim' setting.

What the light might do when it receives power is first do the measuring to look at the sine wave. then after it knows what brightness it is being commanded to show, then enable the LEDs. Now how long does it wait? If it waits 16mS (or 20mS for 50hz) then it can see a 'full' cycle. But since it could start anywhere it really needs to wait 24mS/30mS because that way it is sure to have at least one full cycle in its memory. However, if there is a 'smart' dimmer (think X-10) involved it may just pass through unclipped sine waves as it powers up because "the incandescent light takes many milliseconds to warm regardless." If the LED waits longer before it turns on you cross 100mS which is where pretty much everyone would note a 'lag' between turning on the light and actually having it come on.

All of that just to that a 20 year old dimmer based on TRIACs still works as 'expected' by the user.

Re:Mathematicians Tame Rogue Waves, Illuminating Future of L... by wlesieutre on Wednesday August 23, 2017 @02:18PM (#15083800)
Another lingo note, the old-school TRIAC dimmers are the forward phase ones. Being mostly on the commercial side I don't see much of this, but maybe on residential products that's what's implied when something calls itself "dimmable".

When we get 2-wire dimming it's usually reverse phase (AKA Electronic Low Voltage (AAKA ELV)).

Re:Mathematicians Tame Rogue Waves, Illuminating Future of L... by akx on Wednesday August 23, 2017 @12:58PM (#15083122)
I have LED lighting in my bathroom, controlled by a non-IOT but remote-controllable dimmer, and it does not exhibit that behavior, so I'd say it's just a buggy dimmer.
Re:Mathematicians Tame Rogue Waves, Illuminating Future of L... by hammock on Wednesday August 23, 2017 @11:23AM (#15082201)
And at the same time, lots of (anec?)data coming out that LEDs have adverse health effects
Re:Mathematicians Tame Rogue Waves, Illuminating Future of L... by danmaz74 on Wednesday August 23, 2017 @11:31AM (#15082282)
Example?
Re:Mathematicians Tame Rogue Waves, Illuminating Future of L... by hammock on Wednesday August 23, 2017 @11:38AM (#15082346)
Re:Mathematicians Tame Rogue Waves, Illuminating Future of L... by Retric on Wednesday August 23, 2017 @12:40PM (#15082959)
That has little to do with LED's just a subset of cheap LED's.
Re:Mathematicians Tame Rogue Waves, Illuminating Future of L... by wlesieutre on Wednesday August 23, 2017 @01:38PM (#15083467)
Pretty much all white LEDs are going to have high blue content. It goes back to how they work, these are actually phosphor converted blue LEDs where they pump out a ton of blue light and then use a phosphor layer to absorb and re-emit some of it at other wavelengths.

See spectral distributions here: http://cdn2.goughlui.com/wp-content/uploads/2013/06/spectral...

Even down at 2700K (blue line, "warm white") there's a substantial blue spike over on the left.

The LEDs being used in most streetlights are cool white, probably 4000K+, definitely a lot of blue in that.

There are high CRI LEDs available (Color Rendering Index - at warm colors it basically means "how similar do colors look under this vs under incandescent"), but they're much less efficient in terms of how much light you get per watt, and they tend to be a pretty niche product for lighting stuff where reds are important (brick walls, fruit, art, etc). Still some blue in that, but much less.

https://www.yujiintl.com/img/graphics/warm-white-high-cri.pn...

As to health effects, from what I've heard the jury is still out, but there's a definite push toward "tunable white" in the industry. Whether anyone actually wants to pay for that when it comes time to choose between that or the cheaper fixed color temperature that we've been doing forever, things are less certain...

Re:Mathematicians Tame Rogue Waves, Illuminating Future of L... by Retric on Wednesday August 23, 2017 @06:17PM (#15085690)
I don't disagree with what your saying, but...

LED's don't produce light from heat so they don't really correspond color temperature. They can fake it, but the current approach produces blue at higher efficiency than yellow. Thus upping the yellow content results in lower brightness and lower 'efficiency' for the same device or identical brightness and higher costs.

However, producing a lot of blue light is often sub optimal so you need a consumer willing to make that trade-off instead of just seeing white/cost/brightness and assuming that's the whole story. Thus, cheap really does mean more blue.

Re:Mathematicians Tame Rogue Waves, Illuminating Future of L... by wlesieutre on Thursday August 24, 2017 @12:19AM (#15087566)
You're correct that LEDs aren't actually producing light like a hot black body radiator, but we still measure their shade of white using that scale as a reference. This is called the "correlated color temperature," which you'll almost always see abbreviated to CCT. It's not "this light was produced by a black body radiator at 5000K", it's "this light is perceived by the human eye as the same color as a 5000K black body radiator. Where does the human-perceived color fall on the Plankian locus?

https://en.wikipedia.org/wiki/Planckian_locus

As far as cheapness, yes and no. The swimming pools that I've designed tend toward the more blueish whites and low CRI because they have a light level target to hit and that's the cheapest way to do it. With the exception of some small residential pools, they aren't trying to make a warm cozy feeling, they just want it to be bright enough to meet the requirements for safety / code / IES recommendations / NCAA requirements, etc.

But a lot of lighting isn't done that way where you're determining the layout and quantity of lights to hit a target level at lowest cost. It's much more common that you pick the color temperature that you want it to look like and you buy that regardless of the exact light output.

LED bulbs at the store have a Lighting Facts label that tells you the color temperature and how bright it is, and the different CCTs of a given brand bulb will cost the same. Yes, you get more light out of the more blue one, but when you're getting bulbs for you're house you'd never say "Get the 4000K version. It's an extra 100 lumens, so we can light the house with 17 of them instead 18 and save a few bucks."

Interestingly there are cultural conventions to this too. In the US it's much more common to see the warmer color temperatures in homes and even in offices. In Asia and India you'll encounter a lot more blue.

Re:Mathematicians Tame Rogue Waves, Illuminating Future of L... by wlesieutre on Thursday August 24, 2017 @12:24AM (#15087583)
Beyond that wall of text, a quick note on units. It's interesting (and correct!) that you put "efficiency" in quotes because (at least from an engineering perspective) efficiency is pretty strictly defined to things with equivalent units. You can divide one by the other and measure it as a percentage.

Amount of light you get per watt doesn't quite fit the bill, so we have a closely related measurement called "luminous efficacy."

Units for that are lumens per watt, where lumens are a measure of amount of light (basically watts of EM radiation weighted by the human eye's sensitivity at each wavelength), and watts are the electrical energy consumed per second.

Probably more than you wanted to know, but you never know when that piece of trivia might come in handy.