David Burgess

Houshold LED lights than don't strobe? Does anybody know of any?

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For those who don't already know, a basic LED powered by alternating current in the US will turn on and off 60 times per second. There some household bulbs which use circuitry to raise it to 120 times per second.

The reason I'm asking is that some people have reactions to flashing lights, including epileptic seizures, migraine headaches, and something that is called “flicker vertigo” in the aviation industry. While most people are not supposed to be able to notice flash rates higher than 30-per-second, some people can, and others can be affected by it neurologically even if they can't notice it.

Fluorescent bulbs:

These also can strobe strongly 120 times per second. In fixtures with modern electronic ballasts, the strobe rate is likely to be more like thousands-per-second (and I haven't heard of anyone being triggered by those frequencies), but every compact fluorescent bulb I have tested so far exhibited the strong 120 hz strobe rate.

So does anyone happen to know of any worklamp-sized fluorescent or LED bulbs which do not?

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sorry . not that I know of, the led and fluorescents have solid state circuitry, I would think that would take care of the pulsing,  I have all led lights in the house and have not noticed it . sometimes the dimmer will do a strobe and I have to turn it off and then on again to get it working properly. 

    A few years ago canada gave everyone led bulbs , they came to my sisters house and took all the incandescents and replaced them , but I have not heard of it being a problem? But people are certainly different.  

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14 minutes ago, saintjohnbarleycorn said:

sorry . not that I know of, the led and fluorescents have solid state circuitry, I would think that would take care of the pulsing,

Me too, and I know it can be done, because my computer monitor doesn't do it, or at least it doesn't do it at a rate I can measure (20 kilohertz  or less).

Maybe computer manufacturers have figured out that it's not a good thing to stare at flashing lights all day. :)

While household lighting manufacturers just don't want to spend the extra money?

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4 minutes ago, Jim Bress said:

I have one incandescent bulb in my entire house.  It's in my work-lamp.

Those are what I am using too. But one thing which surprised me is that they strobe too. The reason I was surprised is that most sources say that the filament doesn't heat up and cool down fast enough between electrical impulses for the light output to vary. But it does. However, the change in light output is more gradual, rather than going full-on to full-off instantly. More of a sine-shaped wave than a square wave.

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The vertical scan rate on many computer monitors is 60 to 80Hz, which can still develop flicker, even though the horizontal scan rate is very fast.

To eliminate flicker from LED's and fluorescents, they need to be run on filtered DC power. LEDs are a DC device, so I'm guessing they have a high frequency switching supply built into the base that shouldn't create any flicker. The other brute force method would be to rectify the AC power and use a large dropping resistor to limit the current, but this would waste considerable power as heat.

Fluorescent tubes can be run on DC, but I have yet to see any manufacturer produce a DC supply to run them.

Higher power incandescent bulbs shouldn't exhibit much in the way of flicker, because the filament can't cool off fast enough for the light output to drop noticeably. Smaller power filaments are more prone to this because they have less thermal mass.

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28 minutes ago, saintjohnbarleycorn said:

...A few years ago canada gave everyone led bulbs , they came to my sisters house and took all the incandescents and replaced them ...

Really? Where? When?

I remember the push to get compact fluorescent, but nothing much regarding LEDs.

FWIW - I hate CFL. I much prefer LED.

We still have quite a few incandescent bulbs in use - but I'm phasing them out in favour of the LED. 

I will also gleefully phase out the CFL we felt obligated to use when the pressure began  - hopefully they don't last all that long. :angry:

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To de-flicker LED's, you need some kind of energy storage to power the light when the line voltage goes thru zero.  That I would think might be a bulky/costly addition for the manufacturer, and not included if the market didn't demand it.  I haven't tried it, but maybe commercial LED bulbs can be run on DC (?).  You could put together a bridge and capacitor to run it.

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17 minutes ago, Bill Yacey said:

The vertical scan rate on many computer monitors is 60 to 80Hz, which can still develop flicker, even though the horizontal scan rate is very fast.

To eliminate flicker from LED's and fluorescents, they need to be run on filtered DC power. LEDs are a DC device, so I'm guessing they have a high frequency switching supply built into the base that shouldn't create any flicker. The other brute force method would be to rectify the AC power and use a large dropping resistor to limit the current, but this would waste considerable power as heat.

Fluorescent tubes can be run on DC, but I have yet to see any manufacturer produce a DC supply to run them.

Higher power incandescent bulbs shouldn't exhibit much in the way of flicker, because the filament can't cool off fast enough for the light output to drop noticeably. Smaller power filaments are more prone to this because they have less thermal mass.

Thanks Bill. I don't want to build or purchase a steady DC power supply for every lamp fixture in my daughters house, and I wouldn't be able to do that at her workplace.

A couple of photography-nerd sites I visited said that the pulsing output from an incandescent bulb ceases up around 5000 watts. The worklamp bulb I use (40 watts)  had it quite severely. I suppose the higher wattage you go, the less pulsing you have.

(And thanks, Don)

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I know that your question is about household LEDs.  However, what about battery operated LEDs or those that can operate either from batteries or from a wall wart?  Like a music stand light.  I don't understand why an LED operating from DC should strobe.  (I used to notice the flickering from the old computer monitors unless the refresh rate was increased to over about 60 times per second, but my problem with LEDs is primarily due to their brightness.)  Oops! I see that someone else has made a similar reply. 

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23 minutes ago, phutatorius said:

I know that your question is about household LEDs.  However, what about battery operated LEDs or those that can operate either from batteries or from a wall wart?  Like a music stand light.  I don't understand why an LED operating from DC should strobe.  (I used to notice the flickering from the old computer monitors unless the refresh rate was increased to over about 60 times per second, but my problem with LEDs is primarily due to their brightness.)  Oops! I see that someone else has made a similar reply. 

Battery powered LEDs are generally fine, with notable exceptions:

The apparent brightness of LED lighting on cars these days is mostly controlled with Pulse Width Modulation.This means that they turn on and off very quickly,  but the percentage of time "on" versus "off" is varied, depending on the level of perceived brightness desired. On my newer car, the tail lights turn on and off about 90 times per second. On my older car, with incandescent bulbs and a Direct Current power supply, no  strobing was noticeable.

One of the LED flashlights I checked had a strobe rate of  95 times per second. Since the flashlight is battery powered (the power source is not alternating current, and it has no dimming provision), I have no idea why it does that.

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To get maximum life out of a set of batteries, led fladhlights have a switching dc to dc pwm converter. As the cells drop in voltage, the converter pulses on longer to provide the same power output.

Cel phones use the same technology.

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4 hours ago, David Burgess said:

Those are what I am using too. But one thing which surprised me is that they strobe too. The reason I was surprised is that most sources say that the filament doesn't heat up and cool down fast enough between electrical impulses for the light output to vary. But it does. However, the change in light output is more gradual, rather than going full-on to full-off instantly. More of a sine-shaped wave than a square wave.

I'm curious, is this creating a health problem for you? is the flickering making it so you can't work under these lights? 

Furthermore if that's the case I wonder how it is that some people, such as yourself, are able to "catch" the frame rate as if shutter speed on a camera.

I bought a white scale  led grow light as an experiment, it draws about 130 watts but puts out huge amounts of light, when raised high up towards the ceiling it cast a massive amount of light, it;s a little noisy because of the fan, but boy it pumps out the daylight, not sure if they are different, probably not.

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2 hours ago, Bill Yacey said:

To get maximum life out of a set of batteries, led fladhlights have a switching dc to dc pwm converter. As the cells drop in voltage, the converter pulses on longer to provide the same power output.

Cel phones use the same technology.

Thanks, Bill. One reason I posted the question here was in the hope that various electrical engineers could flesh thing out.

So far, it's looking like strobing lights are pretty hard to get away from entirely, in today's world.

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Oh also, if you are running the power off a dimmer switch it can make it worse, many dimmers are not compatible with led.

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Are you sure you're seeing strobing?  I've seen it in the past with some lighting, but I just checked all the lights in our house, and I couldn't see any strobing at all with a moving pencil.  I checked a bunch of LEDs of different types, a big fluorescent tube, and a couple of incandescents.  I've seen it in the past with some lights, but not with these lights.

I checked one LED with a camera, by waving a lit pencil in front of a dark background.  Strobing is somewhat visible in the picture, but it's only a few percent of total illumination.  The camera can see it, but the eye can't.

I'm not saying that you don't have it, but I wonder if pronounced strobing is all that common any more.  I suppose a dimmer switch with pulsed width modulation could make it worse, but I still can't see it visually with any of my dimmers.

Screenshot from 2019-01-07 12-00-05.png

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5 minutes ago, jezzupe said:

I'm curious, is this creating a health problem for you? is the flickering making it so you can't work under these lights? 

 

Much less for me, than for one of my daughters. She can go into epileptic seizure mode, whereas I only seem to go as far as an "opthalmic migraine" state, which doesn't involve any pain, only disorientation and what might be described as mild hallucinations.

Sure, I'm up for jokes like, “I always knew you had a brain wiring defect”. :lol:

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51 minutes ago, La Folia said:

Are you sure you're seeing strobing?  I've seen it in the past with some lighting, but I just checked all the lights in our house, and I couldn't see any strobing at all with a moving pencil.  I checked a bunch of LEDs of different types, a big fluorescent tube, and a couple of incandescents.  I've seen it in the past with some lights, but not with these lights.

I am not consciously noticing strobing,  except when it is at a frequency lower than 30 times per second, or when there are fast-moving objects in a light source which strobes up to 120 times per second.

All of the strobing rates I have offered here have come from actual measurements, not from my perceptions.

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41 minutes ago, David Burgess said:

Much less for me, than for one of my daughters. She can go into epileptic seizure mode, whereas I only seem to go as far as an "opthalmic migraine" state, which doesn't involve any pain, only disorientation and what might be described as mild hallucinations.

Sure, I'm up for jokes like, “I always knew you had a brain wiring defect”. :lol:

We always knew you were special! :lol:....I find it interesting as it pertains to visual perceptions as that pertains to the field of quantum conscious fundamentalism, like it's some type of glitch in the matrix that only certain people can perceive....epilepsy itself perhaps could be perceived as a glitch I suppose....

but whatever the case it sounds pretty serious as a seizure is no walk in the park and could be dangerous...let alone a headache

I hope you find something that works and please let up know if you do.   

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34 minutes ago, jezzupe said:

We always knew you were special! :lol:....I find it interesting as it pertains to visual perceptions as that pertains to the field of quantum conscious fundamentalism, like it's some type of glitch in the matrix that only certain people can perceive....epilepsy itself perhaps could be perceived as a glitch I suppose....

but whatever the case it sounds pretty serious as a seizure is no walk in the park and could be dangerous...let alone a headache

I hope you find something that works and please let up know if you do.   

Thanks. My youngest daughter in now in her mid 30's, and has never had a driver's license, due to the seizure thing. That wasn't much more than a minor inconvenience at one time, but now she is commuting approximately 1.5 hours per workday by Uber or Lyft, and that's gettin' kinda pricey, stacked on top of daycare expenses for her son. We'd all rather there were not any periods when when she is at home, but unavailable to her two-year-old, too.

Just a Dad, trying to help out in my geek sort of way.

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Since this is Maestronet, maybe we can go off on some tangents about whether superior or excessive light perception crosses over to superior, inferior, or excessive sound perception? :lol:

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11 hours ago, David Burgess said:

I am not consciously noticing strobing,  except when it is at a frequency lower than 30 times per second, or when there are fast-moving objects in a light source which strobes up to 120 times per second.

All of the strobing rates I have offered here have come from actual measurements, not from my perceptions.

I don't doubt the frequencies you measured.  I also wonder whether you have trouble with normal lighting, since I can't detect any hint of flickering with any lighting that I have at home.  Like you, I also use fast-moving objects (e.g., a finger) to detect flickering.

I did find this:

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&ved=2ahUKEwibtuWBu9zfAhVrwYMKHRZxCVkQFjAGegQIAxAQ&url=https%3A%2F%2Fwww.ece.neu.edu%2Fgroups%2Fpower%2Flehman%2FPublications%2FPub2010%2F2010_9_Wilkins.pdf

which claims that a peak-to-trough amplitude of about 35% is necessary to induce headaches at 100 Hz.  What I measured is much less than 35%.

Normal lighting will give a very slight flickering at 120 Hz, or possibly 60 Hz.  The latter is barely within the problem area.  Lower frequencies would be due to dimmers or to defects.

I don't see why fairly ordinary LED bulbs would not be adequate.  In any case a DC lamp would completely eliminate the problem.  Unfortunately, small DC power supplies for lighting may not be designed for the purpose and are likely to give a large AC component.

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LEDs can switch on and off into the KHz region, which is a good thing for data applications, but in this case, not good for lighting. An LED however,  is a DC device, so if operated on a well filtered (regulated) DC power supply, there would be zero flicker. Apparently LEDs for photo applications meet this criteria, it may not fit in with a typical home decor scheme.

Is your daughter so sensitive to this that even incandescents trigger seizures? What is the typical upper limit frequency that causes this? Perhaps converters that run into the Khz switching region could be used without harm?

I know some of the new fluorescent fixtures with electronic ballasts switch at very high frequencies; faster than the persistence / decay time of the phosphors used in the tubes.

Perhaps you could inquire with an electrician working in a hospital setting? They would probably have some specific products for lighting in areas where they deal with epilepsy.

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The problem with photosensitive epilepsy is that it is mainly caused by specific, unpredictable changes towards synchronization of flickering frequencies. Also transformed DC can cause flickering. 

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