CFLs and flicker rate

Discussion in 'Environmental' started by warthog1984, Jan 13, 2008.

  1. warthog1984

    warthog1984 Well-Known Member

    Does anyone know of a CFL that has a different flicker rate than the Sam's Club/GE ones? I stopped using CFLs due to headaches.

    I was concerned about this, and after some research, it seems that some people prone to epilepsy have reported migraines after sustained CFL exposure. The flicker rate seems to be the prime cause.

    As I'm borderline epileptic, this is a concern, especially if incands are banned after 2012.

    Any help would be appreciated.

    Bonus points if a non-flickering CFL that has a UV component (SAD/winter blahs) is suggested.
  2. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    I can't help with the flicker rate question but I do expect you'll be able to buy good LED bulb replacements before long -- and those don't have any flicker at all.
  3. -mr. bill

    -mr. bill Senior Member

    LEDs flicker. But they flicker at a *very* high refresh. (Follow an Escalade at night, and quickly avert your gaze, you'll see the refresh.)

    Incandescents and fluorescents flicker at 60Hz. It's just the magnitude of the flicker on fluorescents is larger. And these days, completely inconsistent lot to lot.

    You have blue eyes? Ways to help are to keep the fluorescents out of your peripheral vision, and it also helps to go indirect.

    For green task lighting, these are my favorite LED lights right now. The new ones have a warmer color as well, and can be dimmed.

    -mr. bill
  4. desdemona

    desdemona Well-Known Member

    I am very sensitive to flicker (though working under totally florescents for a long time has desensitized me a bit). I don't notice it. I think the quality comes into play here. The fish tank lights are pricey CFLs (they are tube florescents btw (so not sure what is compact about them), and I have never noticed flicker. But put a regular tube and I can see the flicker.

    Yeah the flicker is associated with epilepsy. I have controlled epilepsy, and feel it sensitizes me maybe. But I should point out that very few people with epilepsy are actually light sensitive to the point of actually having seizures. Reading by them is more of an issue.

    I use pretty good quality ones where I read, and actually will replace all the florescents with good ones (maybe except in the garage).

    I had a light go off today (not sure if it is a CFL, but if it is, it hasn't been in there so long, I think).

  5. warthog1984

    warthog1984 Well-Known Member


    I should elaborate. I do a LOT of reading, both paper and electronic, at home. While I haven't had a seizure, strobe lights make me very light-headed and walking straight is difficult, let alone staying in the same room without vertigo.

    I think the lesser strobing from CFLs means I can work, but the effort brings on a headache.

    What brand of CFLs do you use?
    Last edited: Jan 13, 2008
  6. GrendelKhan

    GrendelKhan Well-Known Member

    Just something to be aware of people: Seizures don't have to be grand-mal (or whatever the spelling). It's possible to have a mild-seizure disorder, and strobes are a trigger for seizures. Lack of sleep and alcohol are also at the top of the list. Coke trumps them all, but anyone stupid enough to do that isn't worth the time. Anyway, it's possible to not have epilepsy, or to have been diagnosed with it, but to be able to trigger mild seizures.

    If you think the strobing is affecting you, it likely is. Headaches are obvious. But watch out also, for mood shifts, and other brain related things.

    I've seen somewhere that fluorescents can be phase shifted, so that some fraction of lights in a room are bright, while others are darkening, and viseversa. I don't know where to find this, but it might be a solution.

  7. brick

    brick Answers to "that guy."

    My recollection is that fluorescent bulbs flicker with the frequency of the A/C electricity they run on: 60Hz for us North Americans.
  8. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    Just be glad you're not in the part of the world that uses 50Hz power! That's flicker that everyone can plainly see!
  9. desdemona

    desdemona Well-Known Member

    I don't get how to do a couple quotes here, so here goes. I am just such an old fashioned gal. :)


    >I should elaborate. I do a LOT of reading, both paper and electronic, at home. While I haven't had a seizure, strobe lights make me very light-headed and walking straight is difficult, let alone staying in the same room without vertigo.

    >I think the lesser strobing from CFLs means I can work, but the effort brings on a headache.

    >What brand of CFLs do you use?

    I have Panasonics I think. Anyway I got them at Lowes and they were a little higher price. I do a lot of reading as well, but don't usually get headaches anymore. I frequently got them when younger so I think maybe a outgrew them. Maybe you might??
    (They weren't due to lighting, maybe?) I think but there was a lot of the old style fluorescents-- actually still have these at work. I hate them, but I don't get headaches from them.

    Actually most seizures aren't grand mal. That's a myth that I think people believe. My seizures were partial complex which is the most likely to be light sensitive (from what I understand). I wouldn't call them "mild" in the usual sense, but they don't cause loss of consciousness. It is also possible to have light sensitive partial seizures (jerking of limbs usually) or also what they used to call petit mal or absense seizures(Brief staring spell).
    Partial complex have such an array of characteristics it is impossible to list them.

    Yeah it is possible to have non-diagnosed seizures. Esp without loss of consciousness.
    I would say if it is just headaches then it is just headaches. Many people have them and they are probably very common in adults under say age 35.


  10. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Desdemona, that sounds scary!

    For future reference, the way I do multiple quotes is to follow this sequence:

    1. Hit the quote button, then copy the text in the entry box
    2. Hit the back button in the browser and select the quote button of the next post you want to include.
    3. Paste in the contents of the last quote before or after the contents of the new quote.
    4. If you want to add more quotes, copy the entire contents of the entry box and return to step #2. Repeat as necessary until all quotes are included.

    Hopefully that helps!
  11. kwj

    kwj I hypermiled this

    In my anatomy studies, we were taught that the "flicker response" threshhold of the human eye was 45 cps (cycles per second). Our power grid in America is 60 cps. So, the "average" human in America cannot perceive the flicker caused by alternating current.

    Over the course of time I've grown to understand that there is often a wide spread, high and low, in averages (besides there are a number of "averages," being "mean," "mode" and "median").

    So, I expect that some rare individual may perceive a light pulsating at 60 CPS. All the bulbs will flicker at the same rate because of the power grid. So, more or less expensive bulbs should not influence the headaches of this poor individual, either way. What influences my headaches the most, is not updating the perscription of my glasses every two years like I'm supposed to.

    So, what about the expense of different brands of these bulbs? We expect the more expensive bulb to last longer (alas that is not necessarily true - we don't have a lot of experience with them yet).

    What the new bulbs do, is lower your energy use. So do diodes. Around these parts, they now replace traffic signals with LEDs. Man, these are bright enough to hurt.
  12. seftonm

    seftonm Veteran Staff Member

    I think the flicker rate for CFL's will be twice the AC frequency of the power. Power at 60Hz will hit the zero threshold twice per cycle, or at a rate of 120Hz. I can easily see the flicker from a CRT monitor at 60Hz and sometimes even see it at 85 Hz. I no not notice any flickering from my CFL's, so that is part of why I think they are at 120Hz and not 60Hz. I do see some older tubes that seem to flicker at 60Hz though, usually when they are near the end of their life.
  13. desdemona

    desdemona Well-Known Member

    What's scary, what I actually said about flicker or that I didn't know how to quote from two different posts!?

    (BTW, I think I coulda figured out the cut/paste thing. Sounds like work!!)

  14. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Desdemona, I was referring to your descriptions of seizure issues...

    I'm sure you could have figured out the multiple quotes mechanism. I was just offering my experience to give you a shortcut in the process. :eek:

    I can't help you with the work part. ;)
  15. kwj

    kwj I hypermiled this

    Hi seftonm,
    Realize that a CRT is distinctly different than a bulb, in that the alternation of current does not reverse the flow of electrons towards the screen. However, you should try taking a video of your TV, and its refresh rate is very noticeable (do I have this right?). Please correct mej if necessary, I'm technologically challenged.

    45 Hz "supply" is the threshhold below which the eye supposedly perceives the 'flicker.' Don't confuse yourself with what the bulb is doing, concentrate on the supply, that is what the "flicker response" threshhold is based on. We use 60 Hz, Europe uses 50. They must have more headaches than we do, since they are only 5 Hz away from the limit of 45.

    Now, what does that do to their TV and CRTs? Nothing that involves flicker response (I don't think). While you can't set your TVs refresh, you can adjust your CRTs (or go to Plasma or LCD displays). Heck, now I'm going to have to google this whole subject!!!
  16. seftonm

    seftonm Veteran Staff Member

    Hi kwj, I was talking about a CRT monitor with the refresh rate set at 60Hz. The image on it is drawn 60 times a second and I can tell right away if the refresh rate is below 75Hz. Perhaps because the monitor is so big compared to a bulb? I'm not sure.

    Taking a video of the TV greatly magnifies the flickering effect. I don't know why, but I don't notice a TV's flickering anywhere near the same amount as a monitor. When recording, the TV's scanning will not be perfectly synchronized with the camera doing the recording, so each frame recorded ends up showing a partially refreshed screen. When played back, all the frames with partially refreshed screens will lead to very visible flickering.

    I think what the bulb is doing is key to what people see. If I feed a bulb with 60Hz power but have a complex ballast, the power going into the bulb will be different from what the ballast receives, so the light generated may not be flickering at 60Hz. I just finished reading about flicker and it mentions fluorescent bulbs. It says that bulbs with magnetic ballasts will flicker at twice the supply frequency and bulbs with electronic ballasts do not flicker at all.
  17. desdemona

    desdemona Well-Known Member

    Well it was perhaps my statement that partial complex seizures vary so much that it is impossible to list. This can be pretty variable. I don't know what percentage are effected by light, but it can be such that a seizure can be caused by the light filtering thru trees along the highway (really scary!). I think some percentage of unknown accidents might be caused by this. Anyway the other part of the variable can be things as tasting sound or, as my neurologist told me, a case where a person had hallucinations of 7 UP bottles, but only when showering. For a great read on many odd things like this I refer you to Oliver Sacks, who writes with wit and humanity.

    Kwj, perhaps the perceived human limit is more of an average. My nephew can hear a dog whistle. True he is autistic, but he can hear it. He'd plug his ears when one would go off. It's a little out of the ordinary, I admit.

  18. kwj

    kwj I hypermiled this

    Hi desdemona,
    First, I separate normal from average. While we can mathematically determine an average (mean, mode or median), "ordinary" seems more subjective to our observations which can be limited.
  19. Elixer

    Elixer Well-Known Member

    Yep, they flicker at 120Hz, because they flash on both the up and down of each of the AC cycles. However as they get old this balance can get off and they'll start flashing brighter on one of the cycles, making them start to get annoying. They also have lots of other weird flash patterns as they age. My suggestion would be to try out different bulbs if you can and find a CFL that you like. Some have longer flashes than others, which shouldn't make them trigger epileptic like symptoms in those sensitive.
  20. shifty35

    shifty35 Well-Known Member

    I've got the GE energy smart bulbs everywhere in my home, and they light fast with no flicker. Best bulbs I've found so far.

    Computers and TVs flicker due to frequency aliasing because the sampling rate of the camera doesn't meet the Nyquist criterion - the sampling rate has to be double the highest recorded frequency. Thus, the higher frequency monitor refresh appear so be a slower, rolling refresh. TV cameras would have to sample at least 120-180 Hz to avoid aliasing.

    Incandescent bulbs flicker, but it is generally imperceptible. The frequency is also 120 Hz, due to the zero crossings of AC power. However, the filament has thermal inertia, and does not cool below incandescence during zero crossings. Therefore, no flickering is observed.

    Older incandescent ballasts were much worse - in fact, you generally do not use fluorescent bulbs any time power tools or rotating equipment is present. A saw blade spinning at a multiple of the flicker rate would appear to be moving very slowly or even not moving, a serious safety hazard! Again, frequency aliasing - the "sample" rate is the flicker rate of the bulb.

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