Fluorescents and migraines??

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

Quoting from Wikipedia (section flicker):

"Both the annoying hum and flicker are eliminated in lamps which use a high-frequency electronic ballast, such as the increasingly popular compact fluorescent bulb."

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.

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

I guess the confusion arises from the distinction between "perceptible/non-perceptible" flicker.

If you actually "perceive" non-perceptible flicker, then I guess you belong in that special population sample, which is an exception.

I do find it highly suspicious however, that such an issue was never raised

20-30 years ago, when most of the fluorescent lamp population was powered by magnetic ballasts, which had a PERCEPTIBLE flicker.

How come nobody had headaches back then?

Or did they?

Well, if they did, _I_ never heard anything about it back then.

I'm the opposite I really don't care much about color on outdoor lighting but won't use CFL, mainly because the color of every one I've seen simply sucks. Outdoor it's all about cost.

Whatever. I just want light.

There are more important things in this world than efficiency.

I wouldn't use CFLs at all and particularly for outdoor lighting. They take forever to come up to full brightness, even at reasonable temperatures. In the winter, for get it.

I did hear about it.

Also, electronic ballasts mostly have imperfect smoothing of the DC, and have slight 10/120 Hz flicker.

However, I do suspect that a majority of the "ill effects" are psychosomatic. Given the abundance of health claims of particular spectral power distributions and lack of sellers of "healthier fluorescent fixtures" with ballasts having a DC voltage regulation stage after rectifying the incoming AC, I have a dim view of claims of ill health effects until confirmed by good double-blind trials. And by double-blind, I mean anyone involved wearing eyeglasses wearing achromatic ones. Along with fluorescent lamps being studied as well as incandescent controls being in fixtures that do a good job of hiding the lamp type - including, if necessary, filter gels (put them in all fixtures if they are detectable to maintain double-blindness) to make fluorescents and incandescent controls have the same color.

I am also suspicious of claims of flicker-related ill effects of fluorescent lighting that are not also triggered by CRT televisions and CRT computer monitors. Many people think CRTs have some bigtime phosphor persistence, and I did some high speed photography of my CRT monitor and my CRT TV to have phosphor persistence of only a millisecond or two, and my monitor to have phosphor persistence even less, about a millisecond.

My monitor sure looks fine to me at 100 Hz. I think it's 100 - that is the maximum option, and what I had was "optimal". I change it to 72 Hz and I get no perceptible flicker, but sometimes I get "sensatuion it's flickering" - maybe psychosomatic. I find this fixed almost halfway at 75 Hz. I see only minor change from 75 to 85 Hz - several seconds later it looks "pretty much OK" after all. I try 90 Hz and everything looks and feels fine and good.

I am about to try 100 Hz specifically - will followup soon if I dont blow up my $40 monitor in the next few minutes! (I have a spare monitor handy)

- Don Klipstein ( snipped-for-privacy@misty.com)

Now I have it at 100 Hz, and I "felt" some slight improvement over 90 Hz. It may be psychosomatic. But I stare into a corner of the monitor from 3 inches (75-80 mm) away when set to 85 or 90 or 100 Hz, and those all feel the same to me. OK, 85 gives me a slight "nervous feeling" when I do this, but I suspect that's psychosomatic, especially since 75 at this moment "feels only slightly worse" than 85 does. (I am currently changing vertical scan frequencies downward and spend several seconds staring into the lower left corner of the display from about 3 inches away.)

70 Hz gives me a slight visible flicker perception that 75 does not. I got only slightly worse "nervous sensation" at 70 Hz than at 75. Changing from 70 to 72 Hz removes the perceptible flicker.

Changing this to 60 Hz makes my monitor appear very flickery at this moment, though I know that in the past I have gotten used to 60 Hz monitor flicker. CRT televisions in the USA use 60 Hz vertical scan rate.

56 Hz only looks a little worse to me now than 60 does. However, I do remember times in the past when I mostly saw a monitor at 60 Hz to hardly visibly flicker or avoid visible flicker (maybe usually barely), while I almost always saw monitors to flicker at 56 Hz.

I now just changed my vertical scan rate to "optimal", which I think is

100 Hz but I can't rule out 85 or 90. I have a neon glow lamp next to the monitor and I look at both from a distance and roll my eyes up and down, and I can only say that my vertical scan rate now is less than 120 Hz but by a margin too small for it to be 75 Hz.

My TV, at 60 Hz, also has visible flicker of steady solid white areas when I view those at very close range. However, I mostly find that hidden by usually things on the TV moving, and also by details that have 30 Hz flicker if I look from only a few inches away.

In comparison, the flicker rate on non-malfunctioning fluorescent lamps is 100 Hz in Europe and 120 Hz in North America. (Excluding looking at and concentrating on the area around one end of the bulb if the ballast output is power-line-frequency AC, and that is not the case with electronic ballasts.)

I am now finding 60 Hz flicker (from a torchiere "lamp" with E-27 sockets and diode-dimmed and "full blast" settings) to be visible if I look at the luminaire, and to not be visible if I look at illuminated surfaces in the room. I find this from both incandescents and electronically-ballasted CFLs - 60 Hz flicker visible only if I look at the lamp or the luminaire, and 120 Hz having yet to be visible or giving me any noticed sensation, even psychosomatic.

- Don Klipstein ( snipped-for-privacy@misty.com)

Does the flicker show up more for you in peripheral vision?

Old monitors operating below about 75 Hz used to bother me, now I seem not to notice.

In alt.engineering.electrical I.N. Galidakis wrote: | snipped-for-privacy@ipal.net wrote: | [snip] | |> And just how is it that electronic ballasts imply there can be no |> flicker? | | Quoting from Wikipedia (section flicker): | |

| | "Both the annoying hum and flicker are eliminated in lamps which use a | high-frequency electronic ballast, such as the increasingly popular compact | fluorescent bulb."

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 to limit the current flow to prevent the negative resistance effect of the gaseous bulb from being a short circuit. Magnetic ballasts do this with an inductor in series. The inductor limits the current flow without wasting a lot of heat. A resistor could do so, too, but it would dissipate a large amount of heat and make things worse than an incandescent bulb. Actually, a capacitor could also do the job, but it would require a big one and is entirely not practical at 60 Hz.

The electronic ballast limits the current flow by turning the power on and off, usually at a very high frequency rate, with just enoug on times to prevent excessive current flow. A small capacitor can then smooth out current between those pulses. One way to do this is just to do the high frequency chopping directly on the AC. That little capacitor would not smooth across zero crossovers, so the light still gets little to no power during zero crossover, and this leaves the AC flicker there. The other way is to convert the AC to DC, smooth out the DC, and chop the DC itself at the very high frequency rate. No flicker because the smoothing of the DC removed it. The trouble is, this is more expensive. It is more practical do use this kind of ballast in a fluorescent fixture. But a CFL requires a cheaper more compact ballast, and a smooth DC type would raise the costs quite a bit.

| 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.

| 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 guess the confusion arises from the distinction between | "perceptible/non-perceptible" flicker.

That is a point of confusion, sure. People are different. I see the flicker, but I have found that the flicker is not the cause if headaches I get under such lighting. I've gotten them with battery DC powered fluorescent lights.

| If you actually "perceive" non-perceptible flicker, then I guess you belong in | that special population sample, which is an exception.

Yep.

| I do find it highly suspicious however, that such an issue was never raised | 20-30 years ago, when most of the fluorescent lamp population was powered by | magnetic ballasts, which had a PERCEPTIBLE flicker.

It was raised. It was ignored mostly because people could use incandescent lights without any government intrusion. It is raised to a higher level now because the government wants to stop the sale of the incandescent bulbs.

Don't worry, we _will_ stock up in high numbers. Bulbs will be available on EBay and the black market ... for a price.

| 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.

| Well, if they did, _I_ never heard anything about it back then.

You mean in the pre-internet days?

| I am also suspicious of claims of flicker-related ill effects of | fluorescent lighting that are not also triggered by CRT televisions and | CRT computer monitors. Many people think CRTs have some bigtime phosphor | persistence, and I did some high speed photography of my CRT monitor and | my CRT TV to have phosphor persistence of only a millisecond or two, and | my monitor to have phosphor persistence even less, about a millisecond.

One difference about the CRT is that even though the persistence is short and the flicker effect can be high, it has that effect spread out in both geometry and time. That is, the aggregate light from the screen, not a single spot on the screen, has less flicker.

I found that flicker bothered me, but did not cause a headache (rather, it was more of a distraction), with CRTs. Above about 85 Hz it did not bother me, yet I could still see it. Now I have an LCD, and it has very little flicker (I can detect a tiny bit if I work at it).

I do see a bit more color spectrum issue with the LCD than with the CRT. My LCD at work (Acer) seems to be better than the one at home (LG).

| My monitor sure looks fine to me at 100 Hz. I think it's 100 - that is | the maximum option, and what I had was "optimal". I change it to 72 Hz | and I get no perceptible flicker, but sometimes I get "sensatuion it's | flickering" - maybe psychosomatic. I find this fixed almost halfway at 75 | Hz. I see only minor change from 75 to 85 Hz - several seconds later it | looks "pretty much OK" after all. I try 90 Hz and everything looks | and feels fine and good.

Looks like about that same 85 Hz range for both of us.

| Now I have it at 100 Hz, and I "felt" some slight improvement over 90 | Hz. It may be psychosomatic. But I stare into a corner of the monitor | from 3 inches (75-80 mm) away when set to 85 or 90 or 100 Hz, and those | all feel the same to me. OK, 85 gives me a slight "nervous feeling" when | I do this, but I suspect that's psychosomatic, especially since 75 at this | moment "feels only slightly worse" than 85 does. (I am currently changing | vertical scan frequencies downward and spend several seconds staring into | the lower left corner of the display from about 3 inches away.)

I believe the perception will vary depending on how much of the screen is exposed. Cover it up so only the top 10% lets light reach you and it may seem worse. Remember that it scans, so you get continuous light down to the point where it retraces back to the top.

SNIP

SNIP

SNIP

I have used CFLs for outdoor lantern fixtures for the last 10 years, in a moderately cold climate. 10F min. and I'm on only my third set of lamps.

(Earlier poster was boasting of experience with a dozen lamps. One of my clients had 900 CFL retrofits for 5 years. That's expericence!)

They are on a timer so 30 sec to warm up is a non-event. Color is

85CRI 3000K but is slightly different than the neighbors incandescent and MH.

If it's all about cost CFL is the only way to go!

RickR

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

[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.

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.

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.

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.

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.

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 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.

[snip]

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?

I think the confusion arises because people assume that there is no modulation of high frequency output. These are people who don't understand how an electronic ballast really works. They have never thought about the fact that the high frequency oscillator is powered by an imperfect DC power supply.

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.

Of course they "produce" it.

I see the flicker more in my peripheral vision and less in my central vision. The results I reported were with my eyes so close to the monitor that I was using both peripheral and central vision.

- Don Klipstein ( snipped-for-privacy@misty.com)

Try them at -20F. No thanks.

I save even more electricity than using CFLs. I only light an area=20 where someone is. 30sec (don't believe it) warm-up is=20 unacceptable. =20

No, if it's all about cost leave the damned light off. There are=20 things in this life more important than a few cents.

--=20 Keith

Victor Roberts wrote: [snip]

and also in another post:

Let me see if I can use the above to demonstrate mathematically that there exists at least one kind of CFL which does not flicker.

Count the original oscillator in both the above cases as ONE, and the video FPS rate as TWO. Vic, above, effectively says that we always have _some_ ripple even in the best possible cases and hence some light flicker. Therefore, when we video any (even so slightly) flickering light source, we effectively have two coupled oscillators, so the effects can be analyzed mathematically.

It turns out that the slower oscillator (which in this case is the video) "captures" the behavior of the fastest one:

For those who wish to forgo with the math, the above simply means that:

"If there's light oscillation, then it shows on video. Hence, if nothing shows on video, there's no light oscillation".

If, without loss of generality we try the above analysis for some ridiculously high value of light oscillation, say 67361 Hz or 67.3 kHz, the resulting Diophantine equation gives:

k=33680+67361*n j=40+80*n.

Let's pick j, which is easier. The first "flickering" ripple on the video should occur at 2*(40+80)/80 secs = 3 secs. The second flickering ripple on the video should occur at 2*(40+80*2)/80=5 secs. This means that if the light was oscillating at 67.361kHz, the video would have shown flickering ripples with a time amplitude of 2 seconds.

Since the video of the CFL is much longer than 2-3 seconds, it follows that a high light oscillating frequency at least up to 67.361 kHz is not likely.

Adjust the equation per your preferences, adding mayo and jalapeno peppers. I suppose I could solve the problem backwards and try to find what is the maximum oscillation frequency whose video ripple amplitude is larger than a minute worth of video, but it's a little late now and I need to pass to the other dimension for some rest.

(Sorry about having the videos on QuickTime format, but that's my camera's capture mode and as I said, I am a little tired right now. For those who don't know about it, QuickTime is a free download from Apple).

Anyone who disagrees with the above conclusion, please raise your hand... ;o)

I raise my hand in objection.

Instead of your complicated arrangement I just connect an optical detector to my oscilloscope and point it at a CFL. If the trace on the oscilloscope shows modulation, then the CFL light output is modulated.

I've attached a trace of a CFL with small amount of 120 modulation of the light output. The zero level is about 1 division from the bottom of the screen, at the arrow marker.

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

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.

The attachment failed. I posted another message with a link to a BMP of the scope trace.