100Hz flicker in lighting

[mzzj]

I was running around the house with battery powered oscilloscope and small solar cell loaded with 1k resistor (BW tested to be sufficient for 1khz square wave)
Classic iron ballast 2x36W  T8 fluorescent:


T5 2x54W electric ballast fluorescent:


Cheapo 10W E27 led bulb in kitchen:


T8 36W countertop fluorescent:


230v GU10 led spotlights in bedroom:



None of the lights flicker in my eyes but GU10 spots in bedroom are downright nasty otherwise. Any movement is really jerky. Even when reading a book and turning pages the movement jerks.
Bathroom GU10 led spotlights were bit worse than typical iron ballast 36W tube, motion in there is slightly jerky but not to the point of dizziness.
All of the E27 led bulbs currently in use had very low ripple.

Conclusion based on comprehensive one subject objective study: Keep the ripple amplitude below 30% and it should be "good enough"   

[tooki]

Nice measurements!

That strobe effect is exactly a manifestation of the “phantom array” effect I mentioned earlier. I know exactly what you mean about it being nasty.

[SiliconWizard]

Some flicker from lighting can also make some displays annoying to look at when the refresh frequency is not in sync (typically a 30Hz/60Hz display when you have 50Hz mains...)
It's particularly noticeable on some LCD displays (not talking about modern LCD panels for monitors, but rather the small LCD modules with no active matrix). I have a calculator for instance which display you can see flicker under such lighthing. A bit annoying.

[StillTrying]

T5 2x54W electric ballast fluorescent:

I had trouble viewing the small amount of light ripple from an electronic fluorescent in among all the EMI, it was a case of using the scope trigger on AC LINE and using ~32 X waveform averaging to extract the 100Hz light ripple from the noise. It was the same for the dim light from an indicator neon.

230v GU10 led spotlights in bedroom:

That looks like worse ripple than my 3W LED GU10 in Reply #7. Which doesn't give me a headache during the small amount of time I work under it, it just annoys me when I notice large movements are done in steps.

[bap2703]

Back from the graveyard.

I just bought an LED based light to replace a defunct florescent tube.

That's a 1/25 s exposure photo on 50 Hz line.


I am sensitive to flicker so I immediately noticed it.
I expected that in 2021 buying from a reputable brand would prevent that issue to show up, but no :/

[Marco]

I expected that in 2021 buying from a reputable brand would prevent that issue to show up, but no :/

An AC-DC converter is expensive and inside a lamp unreliable, this is as true in 2021 as it was before. A CYT3000A or similar remains attractive, especially if it has to be dimmable.

I wish the EU would just create a new standard for low voltage DC LED lights and kicked off the market for it (with a standardized way to encode a logic signal on the power rail for addressable dimming while they are at it). GU5.3 has to deal with all the 12V AC legacy bullshit. Should have been done a decade ago, but better late than never.

[DeanA]

There is a standard that covers this stuff:
IEEE 1789-2015 - IEEE Recommended Practices for Modulating Current in High-Brightness LEDs for Mitigating Health Risks to Viewers
https://standards.ieee.org/standard/1789-2015.html

[Marco]

That doesn't remove the problem of AC-DC converters inside lamps.

We need a 48V DC consumer standard (industrial and railed LED lighting already seem to be settling on 48V DC too). Hell, you could even reuse existing AC mains lamp bases and just block the mains voltage and refuse to operate in when not powered by 48V DC (though it would still make sense to make some pure 48V DC sockets). Exchange the mains switch/dimmer with a 48VDC lamp switch with integrated AC-DC converter and you can use the 48V DC lamps.

[james_s]

It seems to be an already solved problem, I have lots of LED lamps that don't flicker and have been lasting well. I see little reason to switch to using a separate converter for most applications.

[Marco]

Then you buy the next one and it's bad again,  because no led manufacturer advertises with some guarantueed level of "stroboscopic" effect. Philips Eye comfort for instance only advertise low "flicker" as measured by pstlm but they don't consider 100Hz flicker.

With DC power, true near zero flicker is cheap. No more need for them to lie with semantic bullshit. It would make doing the right thing cheap.

[richard.cs]

Solar cells are HUGE though compared to photodiodes, as far as I know, it's the large capacitance that limits their bandwidth.

Given a photodiode is just a smaller area of the same, you should be able to achieve the same bandwidth with a solar cell, but the load impedance would have to be scaled down in proportion to the area increase. That may or may not be low enough to be difficult in practice.

For me, I find 100 Hz flicker slightly annoying because of noticeable strobing with moving objects, but it doesn't give me headaches, etc.

[wraper]

This is related to the old question of whether watching TV (on a black-and-white CRT, 1950s-style) is harmful to the eyes.  There used to be a lot of concern... CRTs in those days flickered.  Color CRTs later on had longer persistence, and as I understand it, digital flat screens do not flicker.

A test instrument to measure the flicker of lighting would be handy to have.  Anybody care to create one?

Yes they do but not all and not always. Backlight is more often than not PWMed to adjust brightness, sometimes only in lower brightness range. Frequency can be as low as 200Hz. Some gaming monitors have special mode where backlight turns off during image transition time between frames, thus reducing image smearing.

[Tomorokoshi]

I ran across this when looking for LED replacements for fluorescent bulbs:

https://www.visosystems.com/tutorials/

Find the "Flicker and stroboscopic effects (23:29)" video. A PDF is here:

https://www.visosystems.com/media/TLA%20Tutorial%20EU.pdf

[tooki]

Solar cells are HUGE though compared to photodiodes, as far as I know, it's the large capacitance that limits their bandwidth.

Given a photodiode is just a smaller area of the same, you should be able to achieve the same bandwidth with a solar cell, but the load impedance would have to be scaled down in proportion to the area increase. That may or may not be low enough to be difficult in practice.

I have used a small solar cell (perhaps 3x6cm) to measure PWM frequencies, and it had no trouble clearly showing the 4+kHz of the LEDs being tested.

[rsjsouza]

Flickering annoys the heck out of me as well, even if it is imperceptible - headaches and trouble focusing on the task at hand (due to the ghosting effects) are my worst enemies.

One aspect that used to compound to this problem was the intermodulation product of the close frequency between fluorescent lights and a monitor's refresh rate - we used to tweak the frequency to 59 or 61Hz to get a clearer image than at 60Hz. 

[james_s]

Lately I mostly notice it with LED Christmas lights. They're everywhere, and most of them are dim and flicker, the handful of houses still using incandescent holiday lights always look so warm and cheery in comparison. It's a shame the LED strings are such crap still, LED lights for general illumination have gotten really good. Some of them are still crap and flicker but at least you can easily buy good ones that don't.