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Fluorescents and migraines??

Discussion in 'Electrical Engineering' started by Dean Hoffman, Jan 7, 2008.

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  1. 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.

    --
    Vic Roberts
    http://www.RobertsResearchInc.com
    To reply via e-mail:
    replace xxx with vdr in the Reply to: address
    or use e-mail address listed at the Web site.

    This information is provided for educational purposes only.
    It may not be used in any publication or posted on any Web
    site without written permission.
     
  2. krw

    krw Guest

    Oh, that's great. You want people to go back to removable
    screens/storms too? There is enough crap to do around a house to
    get ready for winter every year without futzing with damned light
    fixtures. Not to mention that often outdoor lighting is only
    needed for a few minutes (otherwise MV or Na lights seem a better
    choice).
    Yeah, "you don't need no steenkin' light when there are fifteen
    hours of darkness". Just think of how great it'll be when you have
    fifteen hours of daylight. Great plan to save electricity.
     
  3. krw

    krw Guest

    That's another of the problems with CFLs. You have no idea exactly
    what you're buying. If a poor choice is made buying an
    incandescent it just doesn't last as long. If a poor choice is
    made with a CFL you're stuck with expensive (and unreliable) crappy
    light. It's like chocolate...

    <snip>
     
  4. krw

    krw Guest

    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.
     
  5. 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.

    - Don Klipstein ()
     
  6. If I buy a CFL that I don't like and it costs more than $2, I take it
    back and get a refund. And I say why I don't like it.

    The most recent time I did that was with N:Vision 3500K spirals of a
    higher wattage (I forget how many watts). Reason for return: They
    audibly buzzed. That was a little over a year ago.

    Return bad ones, and the manufacturers get feedback.

    - Don Klipstein ()
     
  7.  
  8. TKM

    TKM Guest

    The are problems with the mesopic notion. One is that there is no way to
    tell when the eye is mesopic or how far into the mesopic it has gone. Plus
    the eye/brain combination is clever enough not to adapt the whole eye ---
    just portions of it. That makes the idea very hard to apply from a lighting
    standpoint. What happens, for example, as your eye roams around at night
    and sees a lighted pathway at very low luminance and then moves to view a
    bright luminaire. If the eye, or part of it, was mesopic, it instantly
    changes.

    I can see how a stroll in an open meadow in moonlight with no electric
    lighting nearby can allow adaptation to mesopic or scotopic vision; but I
    don't see how that can happen in any setting with a continuous stream of
    bright and dark areas in your visual field such as a motorist would
    experience while driving a traffic-filled lighted street with headlights on.

    My view at this point is that the higher blue content of so-called high s/p
    ratio lighting simply excites the rods in the eye to give you the impression
    of more brightness (or glare) without actually improving vision which
    primarily uses the retinal cones. The work that the Lighting Research
    Center (and others) are doing to set up a system of mesopic photometry is
    helping to answer those questions.

    Terry McGowan
     
  9. Guest

    | wrote:
    | [snip]
    |
    |>> I am still trying to figure out what in the world you guys are
    |>> talking about.
    |>>
    |>> I either must be blind or something else is at play here.
    |>>
    |>> The flicker of, say, a PHILIPS TL-D/55/56 35W, is /colossal/
    |>> compared to the flicker of my 2700K CFLs. As far as I am concenred,
    |>> I don't perceive /any/ flicker on my CFLs.
    |>
    |> Maybe you have one of the good ones I've read about that don't
    |> flicker.
    |
    | Every single one I've owned, from the first PHILIPS SL-18W which used a magnetic
    | ballast back in 1980, to cheapo chinese ones to the modern OSRAM DULUX 27W and
    | daylight NARVA 27W, don't flicker.

    Are we talking about different people's ability to see, or not see, flicker?
     
  10. Guest

    | Victor Roberts wrote:
    |> On Sun, 13 Jan 2008 19:11:30 +0200, "I.N. Galidakis"
    | [snip]
    |
    |>> Are we talking about non-perceptible flicker?
    |>
    |> Yes - at least for me. I can measure significant 120 Hz on
    |> the light output of all the the CFLs in my house, but I
    |> don't see any flicker.
    |
    | Thanks Vic. That was a sanity check for me. I actually unpacked my PHILIPS
    | SL-18W, which is the oldest one I've got (1982 or thereabouts) and I asked an
    | array of visitors if they could see any flicker and they said no.
    |
    | Although the SL-18W uses a magnetic ballast, I believe that the triphosphor
    | phosphor persistence is so great that it drowns any visible flickering.
    |
    | One my newer types there isn't even a question as they use electronic ballasts.

    And just how is it that electronic ballasts imply there can be no flicker?
    Sure, if they completely and totally smooth out the power to pure DC, then
    there would likely be no flicker (assuming they don't chop that DC at some
    too low frequency). But merely chopping alone still leaves very little
    power at zero crossovers. I had suggested harmonic chopping such that the
    flicker rate would be 2 or 3 times as high. But that would really make
    some awful power factor.
     
  11. krw

    krw Guest

     
  12. 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 ()
     
  13. 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 ()
     
  14. Charles

    Charles Guest


    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.
     
  15. Guest

    | wrote:
    | [snip]
    |
    |> And just how is it that electronic ballasts imply there can be no
    |> flicker?
    |
    | Quoting from Wikipedia (section flicker):
    |
    | http://en.wikipedia.org/wiki/Fluorescent_lamp
    |
    | "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?
     
  16. Guest

    | 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.
     
  17. Guest

    | 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.
     
  18. 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.

    --
    Vic Roberts
    http://www.RobertsResearchInc.com
    To reply via e-mail:
    replace xxx with vdr in the Reply to: address
    or use e-mail address listed at the Web site.

    This information is provided for educational purposes only.
    It may not be used in any publication or posted on any Web
    site without written permission.
     
  19. 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.

    --
    Vic Roberts
    http://www.RobertsResearchInc.com
    To reply via e-mail:
    replace xxx with vdr in the Reply to: address
    or use e-mail address listed at the Web site.

    This information is provided for educational purposes only.
    It may not be used in any publication or posted on any Web
    site without written permission.
     
  20. 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 ()
     
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