Fluorescents and migraines??

Better still is "Quicktime alternative" - google for it.

Reply to
Stuart
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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?

Reply to
I.N. Galidakis

In alt.engineering.electrical I.N. Galidakis wrote: | snipped-for-privacy@ipal.net wrote: | [snip] | |> Don't believe what you read in Wikipedia, unless they get lucky and |> have something correct (it happens often, but not in this case). |>

|> The purpose of the ballast is... | | [snip ballast explanation for brevity] | | Do I look to you like I need a tutorial on what is a ballast? If that's the | impression I gave you, either my exposition powers are weak or your | comprehension abilities are not up to par.

I've looked at lots of people, and I've never found any real easy means to determine from their appearance, mannerisms, hygiene, or other aspects, whether then need a tutorial on what a ballast is, or not. That, and I didn't even look at you at all, since this is the Internet. So it's just a crapshoot. But you were looking in Wikipedia for information. That is enough to make me worry.

|>> and later down: |>>

|>> "Electronic ballasts do not produce light flicker, since the phosphor |>> persistence is longer than a half cycle of the higher operation |>> frequency. |>

|> They do not _produce_ it. They may let it pass through by not |> storing any energy to "cover" the zero-crossover time period. |>

|> Magnetic ballasts do not _produce_ flicker either. | | Wikipedia is not an engineering manual. For the lay person their explanation is | correct. There is no point in arguing insignificant minutae with me (or with | Wikipedia). /Of course/ ballasts do not "produce" flicker (literally), since | they are not the main power supply which drives the lamp. But from a | non-technical standpoint, it's the inductive resistance of the ballast which | allows the AC cycle to propagate FROM the AC source to the lamp almost | unchanged, making it seem as "flicker", for whatever reason, whether it be | insufficient attenuation of the AC signal, bad power factor, "flattening" of the | AC signal, lack of capacitors or whatever have you.

The resistance in the inductor has nothing to do with it. Maybe you meant to say "impedance" instead of "resistance".

Using the correct terms can, in quite many cases, be very crucial. If you want to be an engineer (even if you just want to play an arm-chair engineer on the Internet), learn to use the correct terms. I had to.

If you want to simplify things, or even over-simplify things, that's one thing. But when things just get wrong, that gives me cause for concern. I've had to deal with (in my field, computer software) people who too often take something that was a simplification as being something of detail and ended up with an entirely wrong understanding. I not saying you have misunderstood these technical things; I'm concerned more about what others might read from Wikipedia or your quotations.

| What really matters here is what Wiki says later, which you conveniently did not | address: | | "Electronic ballasts do not produce light flicker, since the phosphor | persistence is longer than a half cycle of the higher operation frequency." | | As far as I am concerned, THAT's the crucial point which proves there's no | flicker.

Still, that is incorrect.

That statement from Wikipedia suggests that it is the persistence of the phosphor that makes the electronic ballast not produce flicker. That is not just wrong, it's even silly.

Phosphor persistence can help reduce flicker. In very extreme cases it could even eliminate it, in theory (but expect the light to continue to glow for a very long time after you turn it off). This effect would be the same whether the lamp current was being limited by an inductive ballast, capacitive ballast, resistive ballast (no one would use such a beast, but one could be made), or an electronic solid-state ballast.

Try this statement on for size:

"Magnetic ballasts do not produce light flicker, since the phosphor persistence is longer than a half cycle of the higher operation frequency."

Is that any more or less "correct" in the context of Wikipedian engineering than what you quoted from there?

| Of course, if you say that you see flicker, there's no way for me to convince | you otherwise. If I claim that yesterday I saw a grand pink elephant nest with | green eggs and ham sitting at the center of a primordial black hole, there's no | way for you to prove me wrong either.

There are a lot of things I see in a lot of aspects of the world that a lot of people try to convince me is not really there. THEY don't see it, so as far as they are concerned, it really isn't there. I hope you are not slipping into that category.

I wouldn't even try to prove you wrong on your sighting, even though I am quite certain that black holes have no center.

|>> The non-visible 100?120 Hz flicker from fluorescent tubes powered by |>> magnetic ballasts is associated with headaches and eyestrain." |>

|> Some people _can_ see it. Some people need to roll their eyes to see |> that it is there. Some people can just see it directly. It seems |> most people cannot see it either way. | | I am not talking about whether one can see it by rolling one's eyes back and | forth. I can see flickering even on incandescent sources if I roll my eyes back | and forth. The question is whether a lay person can perceive consciously

100-120 | Hz flicker without doing a circus act with one's eyeballs. THAT's the question.

And I can see the flicker directly. I just can't see very accurately how MUCH there is, or how much of it is compensated by the phosphors. When I do scan my eyes across, I can see things that give me more information. If the light is literally on and off that tells me one thing. If the light descends into a different color, that tells me another (phosphor persistence is usually variant in color in fluorescent lighting ... the totally color you get is the average over time).

| It's a question of whether the perceptual system "eye-brain" has the capacity to | perceive this flicker on standing mode ON A CONSCIOUS LEVEL and whether this | flicker can cause headaches.

I can see the flicker from most fluorescent lights even when only viewing the reflection of it from broad surfaces.

However, I have found that this does NOT cause headaches for me. I cannot say if it does or does not cause it for others. I used to THINK that the flicker was the cause, basically because it had been suggested for decades.

| I am ready to agree that although the flicker itself may not be /visible/ on a | CONSCIOUS (PERCEPTUAL) LEVEL, the brain may be able to pick it up | subconsciously. That's a contention I am ready to argue about, as a potential | source of migranes. The rest is irrelevant.

I certainly cannot just count the 120 pulses per second. I can see that it is flickering, but I cannot see individual pulses happening. I do not see it as going on and off. I see the sense of flicker. I see it in some LEDs but not in others. The ones that are battery powered don't have the flicker. Yet they can cause the headaches.

|>> How come nobody had headaches back then? |>>

|>> Or did they? |>

|> I did! I just misunderstood exactly why. Back then I thought it was |> _because_ of the flicker. Now I understand it is because of the |> spectrum. | | Huh? How can you be sure without knowing the EXACT cause of what bothers you in | the spectrum? | | Or if you DO know the exact cause, what is it that bothers you in the spectrum?

The spectrum is not continuous. It has a large gap or two large gaps in it. My eyes do not focus all colors at an equal distance. Glasses exacerbate that problem (more so at the edges of the glass). As a result, the edges where light is different, such as the edge of black text on a white page, is not in perfect focus. With a smooth continuous spectrum, it will appear to be slightly fuzzy, but tolerable. With a broken spectrum, there will appear to be 2 or more distinct edges. In the latter case, my eyes are constantly jumping back and forth trying to focus in one color or the other. That constant refocusing creates stress, and eventually a headache. This is what appears to be going on for me. I do not know if others have the this kind of issue or not. I do not know if they can get headaches from other things that don't affect me. I've learned that people are sufficiently different to never make such assumptions (although I've met many people that have not learned that for themselves).

Reply to
phil-news-nospam

Would you listen to music with 5% distortion?

Reply to
Michael A. Terrell

| You are assuming an ALL or NOTHING situation. All CFL | ballasts I have seen have a DC storage capacitor and | therefore smooth the DC link voltage to some extent. They | just do not have a large enough capacitor to completely | eliminate the 120 Hz ripple. In fact, many CFL ballasts | have about 50% ripple on the DC link.

That must be what I am seeing, then. | | |>| and later down: |>| |>| "Electronic ballasts do not produce light flicker, since the phosphor |>| persistence is longer than a half cycle of the higher operation frequency. |>

|>They do not _produce_ it. They may let it pass through by not storing any |>energy to "cover" the zero-crossover time period. | | Of course they "produce" it.

How is it that ballasts of any kind "produce" flicker?

Actually, I think I might have an example. I have seen many cars with rear tail lights, red in color, that are flickering. If they are powered via the battery, why would that be? I presume they are LED, so there is no reason for a voltage boost that might involve an AC circuit or at least some kind of pulsing DC. I am suspecting the pulses come from either a current limiter meant to reduce energy loss through dissipation (e.g. not using a resistor), or an intensity modulation (in some of the cards, the flickering stops when the break lights come on, bringing the same LEDs up to full intensity). So that may well be a case of a "ballast" producing the flicker. In the case of an AC powered fluorescent light, maybe it is "producing" a 30 kHz flicker?

That flicker on the highway is somewhat annoying _because_ I have to move my eyes around a lot to constantly check many vehicles. It does NOT cause headaches (although some of the drivers out there do).

Reply to
phil-news-nospam

| 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 |

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| 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).

Reply to
phil-news-nospam

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?

Reply to
I.N. Galidakis

In alt.engineering.electrical I.N. Galidakis wrote: | 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 |>

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|> 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.

Reply to
phil-news-nospam

Yes I've noticed that effect to, I find it really strange.

It seems Ok if I look full at them but if they are moving across my line of vision or my eyes are scanning round then I see it.

Most certainly.

Possibly

I have mentioned this to others on occasions but they seem not to have seen the phenomena

Reply to
Stuart

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.

Reply to
Victor Roberts

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.

Reply to
I.N. Galidakis

In alt.engineering.electrical I.N. Galidakis wrote: | Victor Roberts wrote: |> On Thu, 17 Jan 2008 12:48:15 +0200, "I.N. Galidakis" |> wrote: | [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.

Reply to
phil-news-nospam

snipped-for-privacy@ipal.net wrote: [snip]

If I want to play an arm-chair eng> I put more trust in the optical sensor than I do in a video camera,

I say:

I trust my mathematics more than your nonsense.

Reply to
I.N. Galidakis

Well, maybe if you hang the fixtures too low. ;-)

Reply to
Paul Hovnanian P.E.

The problem with that is that they get into cold water when on the toilet. Shrinkage deals with that but the transient is painful.

wishfully thinking :),

Reply to
Don Kelly

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

Reply to
TKM

Man, that water is cold.

And deep, too.

Reply to
Paul Hovnanian P.E.

| 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.

Reply to
phil-news-nospam

Edison's generators were rather clever: they had a bus bar equilizer so each shared the load equally (varied the field coil?). If the generators were intentionally out of phase, that would smooth out the combined output.

and a related story: many NYC buildings still depended on DC power for elevators and ancient parts:

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November 14, 2007 Off Goes the Power Current Started by Thomas Edison

By Jennifer 8. Lee Con Edison's original power plant on Pearl Street.

Today, Con Edison will end 125 years of direct current electricity service that began when Thomas Edison opened his Pearl Street power station on Sept. 4, 1882. Con Ed will now only provide alternating current, in a final, vestigial triumph by Nikola Tesla and George Westinghouse, Mr. Edison's rivals who were the main proponents of alternating current in the AC/DC debates of the turn of the 20th century.

The last snip of Con Ed's direct current system will take place at

10 East 40th Street, near the Mid-Manhattan Library. That building, like the thousands of other direct current users that have been transitioned over the last several years, now has a converter installed on the premises that can take alternating electricity from the Con Ed power grid and adapt it on premises. Until now, Con Edison had been converting alternating to direct current for the customers who needed it ... old buildings on the Upper East Side and Upper West Side that used direct current for their elevators for example. ...
Reply to
Jeff Jonas

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Just like the newer cars, there could well be both AC and DC circuits in houses and other buildings. In fact, that's already happening. Why the old debate about which is "best"? Use what works most efficiently and economically for the application.

Terry McGowan

Reply to
TKM

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