way, way, back in the day of CRT's, it was found that the office lighting was a
bit off phase from the CRT's. This lead to a very slight, but unaware
annoying, difference in the in the office lighting and the CRT lighting, which
caused the eyes to adjust to the change in lighting as the beat frequency of
the difference which fell in the realm of the eyes perception.
That is why the various video options for refresh showed up in the video
configurations files.
Since LED lighting today could be described as digital, on and off depending
where the AC waveform is, and the LCD, etc. displays would be using different
criteria, frequencies, there is sure to be an opportunity for some illuminating
beat frequencies to show up in the physical response range of the human eye!
How many folks do you see that are using an incandescent light on their
desk?This is too mediate the effect by providing a known stable source of light
that averages out the effect to minimize the annoyance factor.
This is old school knowledge that has been forgotten, or not passed on to the
younger generations.
From: Pete Perkins <00000061f3f32d0c-dmarc-requ...@ieee.org>
To: EMC-PSTC@LISTSERV.IEEE.ORG
Sent: Saturday, July 29, 2017 5:30 PM
Subject: Re: [PSES] Flicker from LED and CFL light bulbs
#yiv2486970431 #yiv2486970431 -- _filtered #yiv2486970431 {panose-1:2 4 5 3 5 4
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span.yiv2486970431EmailStyle19 {color:windowtext;}#yiv2486970431
.yiv2486970431MsoChpDefault {} _filtered #yiv2486970431 {margin:1.0in 1.0in
1.0in 1.0in;}#yiv2486970431 div.yiv2486970431WordSection1 {}#yiv2486970431 Ken,
et al, Hopefully someone will supply some data showing that
there isn’t (or is) some interaction between the line input and the light
output. Seems like a pretty simple test: a photodiode
looking at the output while the bulb is running. Looking at
this makes sense since we know that simple SMPS generate a lot of conducted and
radiated stuff which might affect the downstream behavior of the LED itself.
If there is no SMPS driving the LEDs then the problem becomes more complex as
far as getting out what seems to be continuous light. A teardown will
separate the design scheme out to support the results. When
you look at it, let us know what you find. :>) br, Pete Peter E
Perkins, PEPrincipal Product Safety & Regulatory Affairs ConsultantPO Box
23427Tigard, ORe 97281-3427 503/452-1201 p.perk...@ieee.org From: Adam
Dixon [mailto:lanterna.viri...@gmail.com]
Sent: Saturday, July 29, 2017 2:10 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Flicker from LED and CFL light bulbs For reading somewhat
more reliable than the particular UK media cited, try the Wikipedia article for
"flicker fusion threshold." ;-)
https://en.wikipedia.org/wiki/Flicker_fusion_threshold. Reference 11 is a good
relevant refereed journal article.In the LCD panel world, there is a factory
adjustment process to minimize 50/60Hz flicker with the backlight.There is also
human vision research pointing to visual artifact perception at 500+ Hz, but
it's focused more on visual displays vs. lighting.
https://www.nature.com/articles/srep07861 Cheers,Adam in Atlanta On Sat, Jul
29, 2017 at 3:02 PM, Ken Javor <ken.ja...@emccompliance.com> wrote:
I would generalize Mr. Woodgate’s assertion, at least for the US, as: “It is
unwise to give too much credence to anything reported in the press these days.”
That is why I turned to this august body for an interpretation. It was
interesting that Mr. Roman cited an example of a luminary sans power supply,
which would in fact cycle on and off at twice line frequency.
Ken Javor
Phone: (256) 650-5261
From: John Woodgate <jmw1...@btinternet.com>
Reply-To: John Woodgate <jmw1...@btinternet.com>
Date: Sat, 29 Jul 2017 19:42:47 +0100
To: <EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: Re: [PSES] Flicker from LED and CFL light bulbs
It is unwise to give too much credence to anything ‘scientific’ reported in
British newspapers these days.
With best wishes DESIGN IT IN! OOO – Own Opinions Only
www.jmwa.demon.co.uk <http://www.jmwa.demon.co.uk/> J M Woodgate and
Associates Rayleigh England
Sylvae in aeternum manent.
From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: 29 July 2017 16:43
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] Flicker from LED and CFL light bulbs
Just read an article here:
http://www.dailymail.co.uk/health/article-4739766/Low-energy-LED-lightbulbs-giving-HEADACHES.html#newcomment
It says that mains frequency flicker (in the light output) from subject
luminaries causes headaches. At least in the USA, I see power supplies
converting ac mains to a dc potential driving the light element. Is it
different somehow in the UK at their higher mains potential and lower mains
frequency? Is there anything to such flicker? Could it be ac ripple riding on
the dc? But that doesn’t agree with the article, which says LEDS basically
turn off when ac mains potential goes to zero.
Ken Javor
Phone: (256) 650-5261
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