I was driving this evening and the vehicle behind me had LED headlights.
The flicker of those lights made me wonder if they trigger migraine headaches in those who are susceptible to that malady.
I know there were workers who could not work in the shop where there was welding because the sudden flashes of bright light lit-off migraines.
I THINK the flicker of the lights is a way of modifying their intensity in an RMS kind of way. It seems to me that a capacitor would smooth that out or perhaps there is some rate of on-off that is faster than our eyes can perceive.
What do you think? Do you get migraines? Have you ever heard of anybody complaining about the flicker?
Yes, flashes of strong light cause migraines. It's a known association in the Fall of the year with the sun's position. LED's ??
ReplyDeleteGiven that vehicle electrics are DC, and the battery acts as a massive capacitor to smooth out any ripple from the alternator, not sure where any headlight flicker would come from. Some LED headlight systems have multiple LED sources to manipulate the beam directional characteristics, but I wouldn't have expected that to generate flicker?
ReplyDeleteA lot of DC circuits need to change voltage levels and regulate current.
ReplyDeleteThis is especially true in automotive electronics where the battery "voltage" can range from below 10 to 18 and above.
These are most efficiently done with boost or buck converters.
LEDs can certainly flash at very high frequencies although for most converter circuits, we are looking on the order of 10KHz to 1+MHz
Lots of info here:
https://grokipedia.com/page/Buck%E2%80%93boost_converter
Thanks for that update, I hadn't realised that such circuitry was so common.
DeleteI get silent migraines and they are usually triggered by bright flashy lights. Silent migraines have the symptoms of migraines without the headache. Occasionally they turn into full blown migraines, but not often. Annoying but usually not debilitating. If I can, a brief time in a quiet darkened room is enough to make it fade to barely perceptible. Could be worse, my adult daughter gets the real migraines and is sometimes laid low for a period of time.
ReplyDeleteDepends on the intensity of the light for me. Somebody welding behind me so i only get the shadows/reflection off the wall, not so bad. Welding with the arc in line of sight, problem.
ReplyDeleteSome LEDs modulate with PWM drivers too, makes a flicker that can't usually be seen with the unaided eye but can still give troubles if the intensity is great enough.
As an aside, a friend refused to have fluorescent tube lights in his workshop, as the flicker from them made using power tools dangerous - strobe effects could make moving/rotating objects appear stationary. If LED lights have similar flicker, they could be equally dangerous?
DeleteI knew a woman at work, years ago, who had similar trouble with the fluorescent tube lights that were in most offices back then. She said the lights had a subtle flickering which gave her headaches.
ReplyDeleteSouthern NH
Flickering lights can cause epileptic fits. It was sometimes called "TV epilepsy" back in the days when a TV screen would sometimes flicker.
ReplyDeleteThe flickering is caused by overdriving the LED and then letting it cool via the downtime of the duty cycle....making it appear significantly brighter to the human eye without using too much power. If they didn't "flicker" the LED's they'd burn out quickly or have to be run at lower intensity.
ReplyDeleteThe speed and duty cycle are generally fast enough such that humans cannot see the flicker though.
I have a hard time with fluorescent lights flickering. The strobing of the lights on police cars makes me sick.
ReplyDeleteI'd bet there is an interaction between relative motions. That car is doing it's dance, and you were doing yours. Add in the comment by B and now you have 3 frequencies playing with each other. The eye is the unbalanced mixer throwing out a disco ball of info to the brain. If they sync up just right, you see flicker.
ReplyDelete50 Hz systems were pretty easy to see for me, 60 Hz weren't as bad.
Incandescent bulbs have thermal time lag that prevents any flickering even when driven by 60Hz AC power. LEDs are controlled by cheapest circuitry which often fails. Bring back our real light bulbs - a simple piece of heated wire.
ReplyDeleteSome of those newer outdoor “white” Christmas lights make me feel dizzy when I look at them.
ReplyDeleteLast summer (y'all remember not-winter, right?), I decided to cook supper on the back deck SHTF-style without electric lighting. The kerosene lamp light was rather soothing.
ReplyDeleteI'm on the Texas gulf coast. Its amazing, the spike in birth rates after a week-long power outage. Candle light, kerosene lamps...
DeletePut more salt in your diet if you get migraines.
ReplyDelete