Hacker News Reader

Comment by remcob | Hacker News Reader

> 1. Lots of LEDs flicker. Shitty ones with twice the frequency of the main current (so 100/120 Hz) While you might not notice this it causes eye strain and can lead to eye fatigue, headaches, migraines.

That's with a full rectifier. It's even cheaper to go half-rectifier and end up with 50/60Hz flicker. Being cheaper, this happens a lot.

I'm super sensitive to this flickering and will get nausea after sitting in some cheap LED lighting while other people hardly seem to notice.

I jokingly say that with cheap 50Hz LED lighting and 60fps screens, virtual reality now has a higher frame rate than real reality.

View on HN

This use of half-rectified lighting is especially true of LED Christmas lights. I haven't yet dug in on how to change them to at least full-rectified, which look much better to my eyes.

Is it just a matter of adding a bridge rectifier? I guess I'd need to add some resistors in there also to dim the emitters since they'll be on twice as often (to prevent premature burn-out).

Has anybody looked into this? I'll admit to being a bit eccentric.

How does this effect compare to old fluorescent tubes? Where I live we still got a lot of those around (specially in government offices, which is as cheap as you could imagine, and then some), so LEDs seem like a win, even when horrendous.

Fluorescent tubes flicker at 100/120 Hz, but the flicker is less pronounced because the phosphor keeps giving off light for some time after the electrical current stops flowing.

White tubes are made of a mixture of phosphors, and each of them has a different time constant, meaning the flickering is noticeable as repeated changing of colors. Take a photograph (with a rolling shutter phone for example) of a fast moving object under fluorescent light and you'll see blue and yellow shadows from the changing light[1].

[1]: https://photo.stackexchange.com/questions/60701/why-do-i-get...

LEDs also use phosphors -- in that way an LED is like a miniature fluorescent tube. Just like fluorescents, LEDs (at least those used for illumination) have an undesirable emission spectrum that's converted to "white" with a phosphor coated enclosure. (LEDs generally have a very narrow spectrum, and the GaN system used for lighting can produce blue and shorter wavelengths, depending on doping.)

They are 100Hz, as I found out while trying to do an optics experiment, but they never bothered me directly. I think it has to do with LEDs going completely dark, where fluorescent just has slight fluctuations. Or maybe it is a 50Hz vs 100Hz flicker thing.

Reply on news.ycombinator.com