
Mathematicians Tame Rogue Waves, Illuminating Future of LED Lighting - digital55
https://www.quantamagazine.org/mathematicians-tame-rogue-waves-illuminating-future-of-led-lighting-20170822/
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danmaz74
> Engineers need to build LEDs that more efficiently convert electrons into
> light, if the devices are to become the future of artificial lighting, as
> many expect they will.

I was under the impression that LEDs were already the present of artificial
lighting...

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wlesieutre
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.

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criddell
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.

~~~
wlesieutre
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/...](http://www.lutron.com/en-US/Service-
Support/Pages/Technical/Design-SelectionTools/LEDDimmerMatrix.aspx)

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.

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ChuckMcM
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.

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wlesieutre
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)).

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c517402
LEDs and photovoltaics are both PN junctions. I wonder why they don't mention
making better photovoltaics, or why their landscape function can't be used to
improve photovoltaics.

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lightedman
Most likely because this research seems to deal with materials that emit, and
not absorb.

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Sniffnoy
The title here is confusing; as best I can tell, this article doesn't relate
to what's usually meant by the term "rogue waves" (see:
[https://en.wikipedia.org/wiki/Rogue_wave](https://en.wikipedia.org/wiki/Rogue_wave)
).

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cameronfr
I do think there might be some relation -- rogue (ocean) waves are the result
of many waves interfering such that an (ocean) wave of exceptional amplitude
is formed, just as localized regions are the result of many waves interfering
such that a standing wave is formed at said regions.

Then the idea of a rogue wave can be understood to mean a region of
interference in which a wave of strange properties is formed -- such as a
standing wave or a wave of exceptional amplitude.

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jessaustin
Since just discovering the problem got Anderson a Nobel, actually solving it
should get Mayboroda and Filoche one, shouldn't it?

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tankenmate
Reading this article I struck me that you could use the same analysis to
design FinFET junctions to have the localisations coincide with the dielectric
boundary to reduce gate leak, and hence power consumption and heat.

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24gttghh
Also briefly mentioned in the article: [http://www.ipam.ucla.edu/research-
articles/fractal-acoustic-...](http://www.ipam.ucla.edu/research-
articles/fractal-acoustic-barrier/)

This look's very promising. Imagine the public health benefits we could reap
from eliminating 98% of highway noise! And that's from _2009_.

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FreakyT
In the photo, that watch looks like a Pebble Time Round! Such a well-designed
smartwatch, it's too bad they went out of business.

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lathiat
Truth in this most unrelated comment.

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adrianN
Finally we can design open plan offices where the noise stays localized at its
producer :)

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have_faith
If only materials existed with the power to block electromagnetic waves and
sounds waves from propagating... one day perhaps.

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coldcode
A lot of math takes decades to become something practical, it must be
gratifying to discover something that has immediate and widespread
applicability.

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skybrian
It would be interesting to know more about how this affects the design of
current and future LED's.

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lightedman
Not very much. The real problem LEDs face is the Auger Effect.

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jonssons
tl;dr: you'll have to buy new led lights over 5 years.

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Zak
I suspect the difference in performance will be very incremental, not
revolutionary. Sure, efficiency will improve, but the big story will probably
be higher production yields and more consistency.

LEDs are already efficient enough that I'd focus on color quality above all
else when selecting them.

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mdf
Does anyone with a background in electrical engineering, material physics or
something related know, if the same techniques described here could have any
applications on mitigating electromagnetic side-channel attacks (and possibly
lower the power consumption) of electric circuits?

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lightedman
Lower consumption, possibly. Mitigate EM attacks? No.

