100Hz flicker in lighting is a problem?

Hello,
Please can we de-nonsense the “100Hz flicker problem” in lighting?

The web is full of conflicting stories about whether or not 100Hz flicker is actually harmful to humans.

I believe that 100Hz flicker in lighting is no problem whatsoever…..i lived under the old magnetic ballast fluorescent lighting for decades…and had no problem with its 100Hz flicker. Also, driving down motorways with sodium vapour lamp streetlighting which flickers at 100Hz, caused me no problem whatsoever…..and no problem to other drivers either.

Headaches in today’s world are more likely to be caused by Hangovers, too much caffeine, too much sugar, too little exercise, too little sleep due to watching Netflix all night, etc etc…..

The 100Hz flicker problem in lighting is simply a nonsense story pervaded by large electronics corporations so that they can sell their integrated circuits and lamps which get rid of this 100Hz flicker.
Also, most of the large electronics corporations have decided to volume manufacture LED power supplies with large-ish electrolytic capacitor banks, (eg after the PFC stage) which makes them cheaper and easier to design……..and means the 100Hz flicker is easily avoided…….having committed their resources to this in vast quantity, they then are looking to create nonsense stories about smaller manufacturers who make lamps which do flicker at 100Hz….in other words, yet again, all we are seeing, is the large globalist corporations lobbying Governments so as to increase their profits and destroy their smaller rivals.

I mean, they are looking to make greedy mega bucks by replacing all the old 100Hz flickering sodium streetlamps with their flicker free LED offerings....but first, they have to pervade their nonsnese health hazard stories about 100Hz flicker.

Surely you agree?

There is not one single piece of conclusive evidence to state that 100Hz lighting flicker is actually a problem……..nonsense?

**broken link removed**

3:43 to 4:43 of this video shows how the global corporations lobby governments to favour their own profit making rackets, eg in the case of 100Hz flicker stories....
http://www.youtube.com/watch?v=wG--OxNKCt8

Hi,

I don't hink that 100Hz flicker is harmful.

Many people even don't recognize it.
I might be sensible in this, but we have a 240Hz with sharp edges.
I don't reconize it when everything is still and I don't move my eyes.
But I see some "stroboscopic" effect pictures when I move my eyes...and ther are relatively small pieces with high contrast.
It's not that annoying to become hysteric, but it's clearly recognizable.

What makes it more recognizable:
* low flicker frequency
* square wave with sharp edges with 0%/100% brightness
* low duty cycle
* fast moving eyes or objects
* small objects with high contrast to background

Klaus

Klaus is right, it isn't the power to the lamp pulsing at 100Hz that is the issue, it's the light leaving it.
Pulsing (including square waves) to an LED can indeed be visible because for practical purposes the light is turning completely on or completely off. Whether it is harmful or just irritating is subjective but the very real issue of the strobing making moving objects appear stationary is a serious problem. This is why in large factories, the lighting is fed from more than one phase to 'spread' the time each light reaches peak output. Given that machinery is often synchronous to the mains AC, you wouldn't want it to appear stopped when it was actually in motion.

Incandescent lamps obviously have a long decay time, fluorescents have a short but >10mS decay time but LEDs can be nS. PWM dimmed lighting here runs at 1024Hz and still causes strobing effects.

Brian.

Thanks, i wonder if the orange sodium streetlights are flickering at 100hz...because if they are then the british motorway system would be having issues i think..drivers getting headaches and even having accidents?....but i am not sure if the light actually goes to zero every 10ms, or just down say 50%?

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a-haaa..
https://en.wikipedia.org/wiki/Sodium-vapor_lamp

wiki says that sodium streetlights do actually go to zero current every 10ms..........and i have never heard one single complaint in uk of people saying that the streetlights on roads affected them when they drive down the motorway.

The current goes to zero but next time you see a sodium lamp turn off (as at daybreak) you will notice an afterglow of several seconds.

Brian.

Thanks, i am trying to find the light output over 20ms for a sodium lamp, but cant find it....from what you say i now suspect that the light doesnt dip down that much at all over a 20ms interval?

Headaches in today’s world are more likely to be caused by Hangovers, too much caffeine, too much sugar, too little exercise, too little sleep due to watching Netflix all night, etc etc…..

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How true!

But you forget the stress. The omnipotent and omnipresent...

When you talk about the fluorescent lights and the sodium vapour street lamps, you forget that they providing a DC light level with some AC ripple riding on that...

Unfortunately for LED lamps, they turn off practically completely and create a very high level "ripple" light. You know how annoying a flickering lamp can be and just imagine a 100Hz flicker!

Yes, the 100W filament lamps flicker too but it is practically undetectable- lots of thermal inertial. The ballast for fluorescent lamps (and HPSV too) reduce some effect.

You can do a double blind test: 10 subjects in sample (show them one LED with flicker and then another without flicker) and ask them to select (one over the other).

Flickering at 50Hz is not visible but annoying but it may be less at 100Hz.

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small objects with high contrast to background...

Click to expand...

I know this effect; when I try to thread a needle I cannot do that under a regular fluorescent light.

I can do that easily under regular daylight...

Hello,
Regarding LED streetlighting flickering at 100Hz…..this would only affect night-time security cameras and traffic cameras, and police dash-cams, including number plate recognition cameras, if the shutter speed was slower than 1/100th of a second (10ms).
So do you know what is the shutter speed of these type of security cameras? The www doesn’t tell.
Obviously, a Frame Rate of 25 per second, and a shutter speed of 1ms could potentially record for a long time in the prescence of 100Hz flickering LED streetlighting and show nothing at all (total blackness).
However, if all such security cameras automatically increase shutter speed to take in enough light, then this could be overcome…because going up to 10ms shutter speed would solve the problem…however, if this shutter speed is too long for a fast moving object, then there would be movement blur. A man running at 10m/s travels 10cm in 10ms….that could cause unacceptable movement blur…and it would be even worse for a vehicle which moves faster.
Maybe all such security cameras automatically shift the phase of the “shutter openings” in order to accommodate the effect of 100Hz flickering streetlighting with fast shutter speeds? (ie time it so each shutter opening corresponds to the mains peak point, where the flickering light is most bright)

Most cameras work under auto mode; that is they have a fixed aperture and they adjust the speed depending on the available light.

About the movement blur (you are right but if you want to stop the movement, you need a fast shutter and use a flash) much can be done with software so that registration numbers can be read.

But do you remember that in old movies, suddenly the car wheels appear to move in the other directions? That is the strobing effect!