Author Topic: 100Hz flicker in lighting is a problem?  (Read 3427 times)

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Offline james_s

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Re: 100Hz flicker in lighting is a problem?
« Reply #75 on: August 13, 2018, 02:32:24 am »
I loathe nightclubs, the lighting isn't the only reason but it makes me intensely uncomfortable. Are you really that stupid or are you just pulling everyone's leg for some reason?
 
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Offline Gyro

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Re: 100Hz flicker in lighting is a problem?
« Reply #76 on: August 13, 2018, 05:07:33 am »
I  would love to hear  your opinions on a nightclub where I  used to work

That could explain a lot - from nightclub headbanger to the world worst electrolytic-free LED luminaire designer!  |O

It could explain the deafness too.
« Last Edit: August 13, 2018, 05:13:09 am by Gyro »
Chris

"Victor Meldrew, the Crimson Avenger!"
 
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Offline treez

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Re: 100Hz flicker in lighting is a problem?
« Reply #77 on: August 13, 2018, 05:13:54 am »
It looks like we are all off course.....according to this,  all LED lighting is extremely dangerous whether or not it flickers...this is because of the Reactive Oxidative stress caused by the high blue light content of LEDs......

https://articles.mercola.com/sites/articles/archive/2016/10/23/near-infrared-led-lighting.aspx
 

Offline tooki

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Re: 100Hz flicker in lighting is a problem?
« Reply #78 on: August 13, 2018, 05:37:42 am »
It looks like we are all off course.....according to this,  all LED lighting is extremely dangerous whether or not it flickers...this is because of the Reactive Oxidative stress caused by the high blue light content of LEDs......

https://articles.mercola.com/sites/articles/archive/2016/10/23/near-infrared-led-lighting.aspx
That’s an alternative medicine crackpot. That “article” opens by saying that only 1/3 of our energy comes from food, and the balance is infrared. Apparently he believes we are ectothermic (cold-blooded) like reptiles...

Anyway, does this mean you’ve accepted that flicker is an issue, or are you stuck on “it don’t bother me, so it ain’t no thang!”??
 
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Offline helius

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Re: 100Hz flicker in lighting is a problem?
« Reply #79 on: August 14, 2018, 03:35:19 am »
CRT TVs all did flicker to some extent, but they have some phosphor persistence and also the screen is only dark during the vertical and horizontal blanking intervals which are a small portion of the total time.

CRT phosphors almost always have very short persistence times.  If you look at high speed photos of them, you will see that only a few of scanlines are actually illuminated at once.  Yes, you can have after glow for seconds or minutes, but that is a tiny fraction of the light.  Almost all of it is gone in IIRC, 100s of microseconds.

The post from ejeffrey is correct. If they used a longer persistence phosphor, motion blurring would be unacceptably great. (Much like old passive LCD displays where the mouse cursor left a long trail as it moved.)

Computer displays have sometimes used longer persistence phosphors: See the Xerox Alto Technical Report, which discusses the use of P40 phosphors with longer persistence for better ergonomics. The display was interlaced at 60 fields per second. Such a display was not designed for moving pictures (multimedia was over a decade away) so this was a good compromise when the display update speed was limited by memory technology.
 
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Offline james_s

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Re: 100Hz flicker in lighting is a problem?
« Reply #80 on: August 14, 2018, 05:10:45 am »
They don't have a lot of persistence, but like I said they have *some* persistence. When I shut off a monitor in a dark room I can see a faint glow for several seconds. Looking at a high speed video of a CRT I see persistence. At least an order of magnitude dimmer than the active scan line but it is there and helps to soften out the edges. It's not a sharp on-off like you get with LEDs.

The main thing that helps though is as he said, the average illumination level is fairly constant. Since the blanking intervals are much shorter than the average picture time, the duty cycle is quite high even though only one spot is brightly lit at any instant.
 
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Offline In Vacuo Veritas

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Re: 100Hz flicker in lighting is a problem?
« Reply #81 on: August 14, 2018, 05:13:40 am »
You aren’t the only one getting pissed off. If treez isn’t just a master troll, then he’s an idiot.

He's an idiot. How he got employment is strange, but how he kept it is a miracle.
 
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Offline tooki

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Re: 100Hz flicker in lighting is a problem?
« Reply #82 on: August 14, 2018, 10:43:50 am »
You aren’t the only one getting pissed off. If treez isn’t just a master troll, then he’s an idiot.

He's an idiot. How he got employment is strange, but how he kept it is a miracle.
Oh, the latter is easily explained, if the stories he tells about management there are accurate: they're absolute morons, too…
 
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Offline cdev

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Re: 100Hz flicker in lighting is a problem?
« Reply #83 on: August 14, 2018, 01:02:35 pm »
There is something called the critical flicker frequency and human perception of when a blinking light becomes continuous varies quite a bit due to biological parameters.

https://www.ncbi.nlm.nih.gov/pubmed/?term=%22critical+flicker+frequency%22

(Also, bright blue LED light is unhealthy to your eyes. (I say as I sit in front of a monitor)

I should turn it down at night or something.
:o
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Online John B

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Re: 100Hz flicker in lighting is a problem?
« Reply #84 on: August 14, 2018, 01:21:14 pm »
This is probably echoing what has already been said, but my own experiments have lead me to avoid PWM dimmed LED lights altogether. I have a torch which has a reduced light setting around 30% duty cycle at 100Hz. I would consider the light quality to be awful, the flicker is terrible and it's annoying even when focusing on the light. I have a cheap LED dimmer which runs at around 300Hz, which is almost acceptable when looking directly at the light, but the peripheral vision effect was very noticeable. From ones that I've built myself, all those effects were gone around 3kHz. However I ditched them all because of EMI affecting audio equipment.
 
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Offline cdev

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Re: 100Hz flicker in lighting is a problem?
« Reply #85 on: August 14, 2018, 01:54:12 pm »
Most people myself included have a critical flicker frequency - that varies- - however some drugs, specifically the dilating eye drops (probably atropine or scopalamine) my ophthalmologist gives me when I get my eyes looked at, raise that frequency substantially, making me able to see and be annoyed by, the flickering of fluorescent and other lights. Its a wild and strange experience to be able to see lights flickering you don't normally see doing that.
"What the large print giveth, the small print taketh away."
 
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Offline StillTrying

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Re: 100Hz flicker in lighting is a problem?
« Reply #86 on: August 14, 2018, 09:21:17 pm »
I've pointed my photo diode at a 6 inch BW TV.
As the photo diode is looking at 12-15 lines I had to interpret, but the persistence of lines in a bright white area seems to be only about 100us before it's back to near enough the black level. I thought the persistence would be longer than that. - it's less than 2 lines!
 
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Offline treez

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Re: 100Hz flicker in lighting is a problem?
« Reply #87 on: August 19, 2018, 02:30:02 am »
Thanks, i wish we could have photo-diode checks on these new LED filament bulbs which are now selling by the multi-millions in UK........

https://www.thelightbulb.co.uk/light-bulbs/led/filaments?gclid=EAIaIQobChMI5uKYo4L33AIVDCjTCh2pLgGGEAAYASAAEgI3CvD_BwE

...These have a very high level of severe flicker at 100Hz..but there are no complaints  about them.
 

Offline StillTrying

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Re: 100Hz flicker in lighting is a problem?
« Reply #88 on: August 19, 2018, 02:46:02 am »
Thanks, i wish we could have photo-diode checks on these new LED filament bulbs which are now selling by the multi-millions in UK........
...These have a very high level of severe flicker at 100Hz..but there are no complaints  about them.

I might buy one in the next week, unless someone else tries it, a photo diode + 2k2 resistor would do for <1kHz, or PD + any 100mA transistor will do for <50kHz, and be cheaper than the LED bulb.
« Last Edit: August 19, 2018, 02:48:13 am by StillTrying »
 
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Online Siwastaja

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Re: 100Hz flicker in lighting is a problem?
« Reply #89 on: August 19, 2018, 02:56:51 am »
...These have a very high level of severe flicker at 100Hz..but there are no complaints  about them.

There are a lot of complaints about them.

I have complained about them, and I'm not too sensitive to flicker.

Everybody complains about them all the freaking time.

Had one in a hacklab toilet and it was there only for a few days before it was replaced. No one could stand it - even if only exposed for it for short times. It was a great discussion starter really.

BTW, they are not all equal, either!

But if you decide to go "LA LA LA!! NOT LISTENING", then I guess there are no complaints about them, for you.

Yes, crap electronics is being produced and sold around the world in multi-millions. No, it's not a good excuse to design more crap. Especially if you are not targeting the $1-$2 segment!

Also, designing cheap crap is more difficult than you think. If you go too low, you'll hit problems soon. Your attitude is not going to work here. You need competency - the idea of the cheap crap is that you can spend money on R&D because they'll be sold in millions. Some $1 product may have $10000 extra engineering cost went in just to reduce the unit price by a few cents!
« Last Edit: August 19, 2018, 03:49:32 am by Siwastaja »
 
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Offline james_s

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Re: 100Hz flicker in lighting is a problem?
« Reply #90 on: August 19, 2018, 03:44:52 am »
Those LED filament bulbs do tend to flicker badly, it's a fatal flaw that has severely limited my adoption of them. I have found some that have little enough flicker to be acceptable in a few applications but even so I don't use them for task lighting that I spend a lot of time under.

The level of denial is frankly stunning. We have what, 4 or 5 people just on this thread which is a very random esoteric corner of the internet complaining about the flicker which means there are likely tens of millions of people in the general public who find it bothersome and yet that's nobody? Honestly I envy those who cannot perceive flicker.
 
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Offline NiHaoMike

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Re: 100Hz flicker in lighting is a problem?
« Reply #91 on: August 19, 2018, 07:16:06 am »
Big Clive does a lot of LED teardowns and it seems like the ones that flicker a lot do so very badly on video, but not all LEDs that flicker on video flicker to an annoying degree in real life. So I would say that it causes the most headaches for those filming videos.

Still, there's little reason for a quality LED light to flicker.
Cryptocurrency has taught me to love math and at the same time be baffled by it.

Cryptocurrency lesson 0: Altcoins and Bitcoin are not the same thing.
 
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Online BrianHG

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Re: 100Hz flicker in lighting is a problem?
« Reply #92 on: August 19, 2018, 08:32:51 am »
I've pointed my photo diode at a 6 inch BW TV.
As the photo diode is looking at 12-15 lines I had to interpret, but the persistence of lines in a bright white area seems to be only about 100us before it's back to near enough the black level. I thought the persistence would be longer than that. - it's less than 2 lines!
Careful here, that super quick charge of the phosphor actually fast charges way too bright to for your eyes to see properly if your eye could register that amount of light that quickly.  It's the initial fast discharge of the phosphor's decay process which means the actual light of the picture your eye accounts for a visual image, where the display is already down to around 5-10% of the charge brightness.  Since phosphor is a decay in brightness, not a linear drop in brightness, that last 5-10% which your photodiode is registering the light as black after the super-bright quick initial charge, after around 5 lines, is what your eye mostly sees which glows down to around 1-2% brightness at 1/60th of a second.  Remember, our eyes register light logarithmically, not linear like your photodiode.  You also need to take that into account as well.

Try amplifying your photo diode's output and ignore the initial phosphor charge during the first 4 line as the raster scans so you can see the remainder of the light.  After an initial cliff like drop in brightness, you will see a smooth curve developing over 1/60th of a second, actually it's even slower than that if you have 1 frame white, the next black, you will detect a decaying glow for 1/30th of a second (we are talking below 1%).  This is the light your eye is responding to.
« Last Edit: August 19, 2018, 11:48:26 am by BrianHG »
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Offline helius

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Re: 100Hz flicker in lighting is a problem?
« Reply #93 on: August 19, 2018, 12:33:56 pm »
[The] quick charge of the phosphor actually fast charges way too bright to for your eyes to see properly if your eye could register that amount of light that quickly

Does this make any sense at all? There is no minimum period for light to be visible to your eyes. A strobe lamp has an emission lasting some tens of microseconds, but it doesn't cease to be visible. Sonoluminescence experiments produce flashes as brief as picoseconds and are visible to the naked eye.
 
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Online BrianHG

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Re: 100Hz flicker in lighting is a problem?
« Reply #94 on: August 19, 2018, 01:02:18 pm »
[The] quick charge of the phosphor actually fast charges way too bright to for your eyes to see properly if your eye could register that amount of light that quickly

Does this make any sense at all? There is no minimum period for light to be visible to your eyes. A strobe lamp has an emission lasting some tens of microseconds, but it doesn't cease to be visible. Sonoluminescence experiments produce flashes as brief as picoseconds and are visible to the naked eye.
Careful, the strobe lamp is 10 times faster, but, 1000x stronger...  If you could keep a Xenon strobe tube on at full 50-100 amps, (approximate power of a good strong strobe during the short pulse), not only will you melt/burst the strobe tube, but, you would burn out your eyes and give you sunburn.  Just so we are clear, with a 3.5us flash, you feel heat coming from one of those Xenon tubes.  Keep it illuminated at that 50 amps continuously, the brightness will blind you in under a second.

I've done precise timing studies on monitor phosphor charge and discharge times, and even had super fast LCD shutters to block the light to the eye during the time the phosphor is being charged for around 15 lines of video.  Blocking the display during this charge time only, to the eye, the picture in that region dims only by around 15%.

The work I've done analyzing CRT phosphor was use in testing and creating my 3D stereoscopic patent here: https://patents.google.com/patent/US6532008
« Last Edit: August 19, 2018, 01:17:44 pm by BrianHG »
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Offline treez

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Re: 100Hz flicker in lighting is a problem?
« Reply #95 on: August 26, 2018, 11:05:26 pm »
Hello,
Regarding  LED streetlighting flickering at 100Hz…..this would only affect  night-time security cameras and traffic cameras, and police dash-cams,  including number plate recognition cameras,  if the shutter speed was slower than 1/100th of a second  (10ms).
So do you know what is the shutter speed of these type of  security cameras? The www  doesn’t  tell.
Obviously, a Frame Rate of  25 per second, and a shutter speed of 1ms could  potentially record for a long time in the prescence of 100Hz flickering LED  streetlighting and show nothing at all (total blackness).
However, if all such security cameras automatically increase  shutter speed to  take in enough light, then this could be overcome…because going up to 10ms shutter speed would solve the problem…however, if this shutter speed is too slow for a fast moving object, then there would be movement blur. A man running at 10m/s  travels 10cm in 10ms….that could cause unacceptable movement blur…and it would be even worse for a vehicle which moves faster.
Maybe all such security cameras automatically shift the phase of the “shutter openings” in order to accommodate the effect of 100Hz flickering streetlighting with fast shutter speeds? (ie time it so each shutter opening corresponds to the mains peak point, where the flickering light is most bright)
« Last Edit: August 27, 2018, 10:44:00 am by treez »
 


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