Fluorescents and migraines??

On Thu, 17 Jan 2008 03:18:19 +0200, "I.N. Galidakis"


OK - I'll raise my hand.
Instead of using your approach I just connect an optical detector with sufficiently short response time to my oscilloscope and point it at the CFL. If the trace is nor flat then the light output is modulated.
See http://www.robertsresearchinc.com/Papers/CFL_Modulation.BMP for an oscilloscope trace of the light output of a CFL with a small amount of modulation.
The zero level is a bit below the first division on the screen, where the small arrow pointer is positioned. The average output is about 40 mV and the peak-to-peak ripple is about 7 to 8 mV.
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Victor Roberts wrote: [snip]

I see your objection and evidence, but I disagree that this modulation is "visible flickering".
If the zero on your oscilloscope screen (as you say) is close to the lower arrow, then I count a modulation amplitude of something like 5, max 10%. If the zero is lower, the amplitude is less than 5%.
Are you kidding me Vic? That's a practically flat signal.
Obviously there is a certain minimum modulation of the first oscillator in order for the video to display a /visible/ flickering effect on the coupled oscillator, but we could then argue ad nauseam what should this minimum modulation be, in order for the flicker to qualify as "visible".
I mean, if the CFL displayed a 2% amplitude modulation, does the corresponding flicker qualify as "visible"? What about 0.00006%?
Let me then correct the conclusion, by adding the word "visible", which I did not include in my previous post (but had it on my web page regardless):
"If the CFL pictured above displayed any _visible_ flicker, then the video above should also have displayed flicker, as per the analysis above. But it does not. Hence this particular CFL does not display _visible_ flicker".
In my eyes a modulation of 5-10% certainly does not qualify as "visible flicker" and is a huge improvement over magnetic ballast flickering on old fluoescent lamps where there is an actual shutoff of the light.
With your permission, may I add your oscilloscope pic on my web page along with your objection citing your name?
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"I.N. Galidakis" wrote:

Would you listen to music with 5% distortion?
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Michael A. Terrell wrote: [snip]

Would you ever listen to an .mp3 file?
Have you seen the waveform of an 128 kbit compressed .mp3 file compared to the waveform of the original .wav or .aiff file?
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| Victor Roberts wrote: | [snip] | |>> Anyone who disagrees with the above conclusion, please raise your |>> hand... ;o) |> |> OK - I'll raise my hand. |> |> Instead of using your approach I just connect an optical |> detector with sufficiently short response time to my |> oscilloscope and point it at the CFL. If the trace is nor |> flat then the light output is modulated. |> |> See |> http://www.robertsresearchinc.com/Papers/CFL_Modulation.BMP |> for an oscilloscope trace of the light output of a CFL with |> a small amount of modulation. |> |> The zero level is a bit below the first division on the |> screen, where the small arrow pointer is positioned. The |> average output is about 40 mV and the peak-to-peak ripple is |> about 7 to 8 mV. | | I see your objection and evidence, but I disagree that this modulation is | "visible flickering". | | If the zero on your oscilloscope screen (as you say) is close to the lower | arrow, then I count a modulation amplitude of something like 5, max 10%. If the | zero is lower, the amplitude is less than 5%. | | Are you kidding me Vic? That's a practically flat signal.
Doesn't look flat to me. But maybe it is beyond your ability to sense any flickering. Only you can tell us whether that is the case or not.
| Obviously there is a certain minimum modulation of the first oscillator in order | for the video to display a /visible/ flickering effect on the coupled | oscillator, but we could then argue ad nauseam what should this minimum | modulation be, in order for the flicker to qualify as "visible".
I hope you understand that the level of light changes that gets sensed as flicker is different for different people.
| I mean, if the CFL displayed a 2% amplitude modulation, does the corresponding | flicker qualify as "visible"? What about 0.00006%?
The lower the percentage, the fewer people would see it. I don't know if the effect would be linear, or just what point is needed to eliminate all people seeing it. And the effect within a person could vary as people might not see different levels the same way.
| Let me then correct the conclusion, by adding the word "visible", which I did | not include in my previous post (but had it on my web page regardless): | | "If the CFL pictured above displayed any _visible_ flicker, then the video above | should also have displayed flicker, as per the analysis above. But it does not. | Hence this particular CFL does not display _visible_ flicker".
I put more trust in the optical sensor than I do in a video camera, especially if the camera has CCD technology and/or artifacts processing.
| In my eyes a modulation of 5-10% certainly does not qualify as "visible flicker" | and is a huge improvement over magnetic ballast flickering on old fluoescent | lamps where there is an actual shutoff of the light.
Although I have not used the kind of setup Vic did to measure the actual light levels and changes, I do suspect I can sense flicker in a lot lower level than you can. I do sense some degree of difference: some lights do have more or less than others. I reference a neon night light I have as a case with extreme flicker. CFLs are not as bad at that.
I am gradually using more and more CFLs and am putting them in places I do not already have fluorescent lights, with the exception of long term task lighting areas (work bench, kitchen, etc) which will stay with incandescent until some better spectrums come out.
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On Thu, 17 Jan 2008 12:48:15 +0200, "I.N. Galidakis"

I don't remember ever using the word "visible" to describe this flicker.

That is about right for this example.

But it's not constant, and other samples have more modulation.

I don't understand the "first oscillator" statement. CFL ballasts normally use a single self-oscillating power stage. If run from a DC power supply with a constant voltage output and no ripple, the high frequency envelope they produce will have no significant low frequency modulation.

I really don't have to worry whether or not 2% would qualify as flicker since I'm measuring more than that amount.

I still think that even for your experiment you need to use an instrument other than your eye to make the measurement. Some people are more sensitive to periodic variations in light intensity than others.

I'll have to post some photos of CFLs with higher modulation levels and also a the modulation generated by a linear lamp operating from a 60 Hz ballast for comparison.

Yes. But make sure you state it is only one example and other lamps may have more or less of the 120 Hz modulation.
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Victor Roberts wrote:

[cut]
You didn't. But you raised your hand in disagreement for the conslusive statement of my analysis, which was:
"If the CFL pictured above displayed any visible flicker, then the video above should also have displayed flicker, as per the analysis above. But it does not. Hence this particular CFL does not display visible flicker."
[snip]

By "first oscillator" I mean the light oscillation.
[cut]

Ok. If you disagree with my wording, please check it and tell me so I can change it.
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| Victor Roberts wrote: |> On Thu, 17 Jan 2008 12:48:15 +0200, "I.N. Galidakis"
| [cut] |>> I see your objection and evidence, but I disagree that this |>> modulation is "visible flickering". |> |> I don't remember ever using the word "visible" to describe |> this flicker. | | You didn't. But you raised your hand in disagreement for the conslusive | statement of my analysis, which was: | | "If the CFL pictured above displayed any visible flicker, then the video above | should also have displayed flicker, as per the analysis above. But it does not. | Hence this particular CFL does not display visible flicker."
Append: ... that this video system is able to pick up.
Video systems vary, too. But, just because a video system does not pick it up, that does not mean it is not there. I'm sure I can find people that can say they do not see any flicker in my neon night light (that goes 100% off at 120 zero crossings per second). Would such testaments mean no flicker is there? Of course not. It would just mean I have found someone that is unable to see the flicker or lies about it.
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snipped-for-privacy@ipal.net wrote: [snip]

If I want to play an arm-chair engineer on the internet, eh?
I am sorry, in view of the above I have no interest in your opinions. And like you said:

I say:
I trust my mathematics more than your nonsense.

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| Instead of using your approach I just connect an optical | detector with sufficiently short response time to my | oscilloscope and point it at the CFL. If the trace is nor | flat then the light output is modulated. | | See | http://www.robertsresearchinc.com/Papers/CFL_Modulation.BMP | for an oscilloscope trace of the light output of a CFL with | a small amount of modulation. | | The zero level is a bit below the first division on the | screen, where the small arrow pointer is positioned. The | average output is about 40 mV and the peak-to-peak ripple is | about 7 to 8 mV.
I believe that is still enough flicker for some to perceive the flicker as being present. Maybe a lot fewer people than if it were 39 mV peak-to peak. It could all be a matter of degree, and a matter of marketing. They won't want to double the size of the capacitor just to satisfy 0.5% of the market. So some people will have to depend on their stockpile of incandescent lamps or use the black market (it will be there).
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But, as we've said here before, inandescent lamps on either 50 or 60 Hz do flicker. Some people can see it and there's even enough flicker with incandescent sources that we calibrate such things as turntable speed with strobe meters. I've done it myself. So, while continuing to use incandescent lamps may be a satisfactory answer, it doesn't seem like flicker is the cause -- or at least the whole cause -- of the problem.
How about some new theories?
Terry McGowan
It would seem we really don't understand what it affecting the people, like PH who
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| But, as we've said here before, inandescent lamps on either 50 or 60 Hz do | flicker. Some people can see it and there's even enough flicker with | incandescent sources that we calibrate such things as turntable speed with | strobe meters. I've done it myself. So, while continuing to use | incandescent lamps may be a satisfactory answer, it doesn't seem like | flicker is the cause -- or at least the whole cause -- of the problem. | | How about some new theories?
Or old ones?
I used to think it was flicker that bothered me. But a few years ago I came to the conclusion the problem is the spectrum of the light (and I do not mean color balance).
I did a test just a couple days ago looking at some lights to see what I could sense as flicker and compared that to viewing the same light in a cylindrical mirror in motion that would spread the light in time across my field of view where I can see the flicker as a row of dots (in the extreme case ... fuzzy in non-extreme cases). What I found is that my sense of flickering is not as strong with incandescent even though the flicker is clearly there with the mirror test. But what I see in that test is that the flicker in fluorescent lights changes color (it is more reddish in the off cycles). Flicker in incandescent is more consistent in color. So maybe my sense of flicker that works better with fluorecent is really a sense of rapid color change.
Flicker at the 120 Hz level is not causing me headaches. What apparently does cause them is a discontinuous spectrum where there emissions are at specific wavelengths, and there is a gap between them. I've also used a (near) monochromatic light source and found it works quite well. What I think is the mechanism is that the eye jumps between the focus on one wavelength and then the other, when sharp edges are present, such as the black text on a white page. With a continuous spectrum, it is fuzzy, and the eye settles in to the middle of the range.
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Better still is "Quicktime alternative" - google for it.
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     snipped-for-privacy@ipal.net writes:

This is standard in the SMPSUs used in enterprise grade computers nowadays (or you can't sell them in various parts of the world, such as Europe).

It doesn't really. You can read the strobe on the side of a record turntable under a 240V 40W 50Hz lamp.
I'm not convinced there's any problem at all with the amount of 100Hz flicker that you'll get from a CFL. You can't actually perceive flicker at 100Hz though -- the human brain is far too large to process the information fast enough. A fly can see flicker at 1000Hz though, due to a much smaller brain. This whole issue was raised by someone in an organisation who didn't understand the difference between old magnetic ballasted fluorescent tubes and modern CFLs.
There are also a number of people who complain about fluorescent lighting, but I have found this to be psychosomatic in the cases I know. If they think the lighting is fluorescent, it causes them a headache or whatever. This doesn't correlate with whether it really is fluorescent though.
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| It doesn't really. You can read the strobe on the side of a | record turntable under a 240V 40W 50Hz lamp.
I've seen that. It's every so slight.
| I'm not convinced there's any problem at all with the amount | of 100Hz flicker that you'll get from a CFL. You can't actually | perceive flicker at 100Hz though -- the human brain is far | too large to process the information fast enough. A fly can | see flicker at 1000Hz though, due to a much smaller brain. | This whole issue was raised by someone in an organisation | who didn't understand the difference between old magnetic | ballasted fluorescent tubes and modern CFLs.
Nice try ... to make people who admit to seeing the flicker be perceived as having a small brain. Just keep in mind that the whole brain does not get involved in the sensation of light and flicker. Possibly, different people perceive the flicker in very different ways. I know I do see the flicker. I used to think it was the cause of my headaches from such light sources. But it's not. The cause of the headaches for me turns out to be the dis-continuous spectrum. But I still see the flicker when it is there. I see the flicker is HPS lamps, but those don't give me a headache.
| There are also a number of people who complain about fluorescent | lighting, but I have found this to be psychosomatic in the | cases I know. If they think the lighting is fluorescent, | it causes them a headache or whatever. This doesn't correlate | with whether it really is fluorescent though.
Some LEDs give me the headaches. Some CRT screens do, too. But some don't. Almost all fluorescent lights do, whether they flickered or not. I have seen some incandescents that flickered. One recently was a bathroom night light that had actually burned out and in so doing, recontacted the filament in an unsupported way. It was physically/mechanically vibrating while it was also running brighter than usual due to the now shorter filament.
Again, I do see the flicker in a great many lights. I don't see any in many others, but I don't know if that is because the light is smooth or just flickering at a higher frequency. BTW, I see the flicker in _some_ car tail lights, and not in most others. I'm guessing they are regulating the current on the LEDs by a rather low frequency PWM.
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On 13 Jan 2008 18:49:38 GMT, snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

With respect to 100Hz or 120 Hz modulation of the light produced by fluorescent lamps, there is far less difference between "old" magnetic ballasts and many "modern" high frequency electronic ballasts - especially those built into CFLs.

I fully agree. When I do a blind test with friends and family who say that fluorescent lamps are terrible, they have no problems with the quality of light produced.
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alt.engineering.electrical, snipped-for-privacy@lighting-research.com says...

Of course not. If they're blind how would they see flicker. ;-)
I can see perceptible flicker with most fluorescents. Depending on the circumstances I can ignore it or it can be quite bad. Under most lighting conditions, 85Hhz is where things stop diving me right up the wall. Just because *you* don't see it doesn't mean no one can. I know people who have their monitors set for 60Hz too. They can't see the difference.
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I would beg to differ. I find a major difference between electronically-ballasted CFLs and magnetically ballasted ones in terms of flicker.
I look at a CFL and roll my eyes up and down, and I can usually tell what kind of ballast it has. I look at the streaks that I see as a result of rolling my eyes up and down, and I see a flicker pattern with magnetically ballasted ones. I see lack of such with CFLs with electronic ballasts (though I have not tried this with any known to have electronic ballasts with high power factor).

That I agree with! I get people to look at a lamp, and I tell them, "Can you believe it's a fluorescent"? They say, "What makes you think it is fluorescent"? I have large polycarbonate eyeglass lenses and my left one has +3.5 diopter, and the upper left corner is prismatic enough for me to see enough spectral characteristics of most lamps for me to identify what basic kind of lamp it is.
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wrote:

Well, you obviously have to store SOME energy since you can't take energy from the power line when the voltage is near a zero crossing. However, using sophisticated techniques you can significantly decrease the size of the energy storage capacitor.
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| wrote: |
wrote:
|>> |> |
|>> |> |> |>> |> |>| Does the spectrum cause migranies and "skin eruptions"? I thought |>> |> |>| migraines were flicker rate which should be a non-issue with CFLs. |>> |> |> |>> |> |>I see CFLs that flicker. Probably very cheap ones. But they exist. |>> |> |> |>> |> |>BTW, I bought an LED flashlight the other day that has a white spectrum |>> |> |>that does not bother me like other LEDs and all fluorescents and metal |>> |> |>halides do. And it's a rather bright and well built one. LEDs are now |>> |> |>looking more like they could be my future efficient lighting method. |>> |> | |>> |> | Line-powered LEDs can also flicker if the DC link is not |>> |> | properly filtered. |>> |> |>> |> No doubt. Maybe one day the lighting industry will figure out how to |>> |> properly smooth out the DC? Hint: it can be done without those big |>> |> capacitors that power supplies of days gone by had. One idea that |>> |> comes to mind is to chop the current with a pulse width varied to |>> |> compensate for the lower frequency component(s) of the ripple. |>> | |>> | The same energy has to be stored. |>> |>> Stored? What do you mean stored? That's not the only way to do it. |> |>I see what VR is talking about but that's going to play hell with |>the PF. The EU isn't going to like that much and I'd imagine the |>US won't wait forever, particularly if every light bulb on the |>planet plays these games. There are two zeros per cycle to "smooth |>over". | | Well, you obviously have to store SOME energy since you | can't take energy from the power line when the voltage is | near a zero crossing. However, using sophisticated | techniques you can significantly decrease the size of the | energy storage capacitor.
My idea was to boost the flicker frequency to evade the issue. But, alas, it has the problems of bad PF and missing the peak voltage when at 2x Hz.
Back to DC.
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