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| TimFox:
Interesting (about Christmas LED flicker). With cheap LED strings from Home Depot (one multi-colored and one white), operating from 60 Hz, I do not perceive any noticeable flicker. On the white string (pre-installed on a fake tree), I do see a spatial effect due to the small luminous surface inside a glass envelope, but it is time-stationary. |
| tom66:
The last set of Xmas lights I bought came with an SMPS that outputs very smooth 24VDC and even on the PWM setting the flicker is barely noticeable. (I can generally see flicker up to a few hundred Hz by scanning my eyes across something, but much more than that is imperceptible.) I would guess a DC SMPS is probably cheaper than an AC transformer nowadays, plus it automatically makes the lights safe for outdoor usage (though in my experience, unless you get higher quality ones, they won't last long due to corrosion at the base of the LEDs.) |
| james_s:
--- Quote from: TimFox on December 06, 2022, 09:11:22 pm ---Interesting (about Christmas LED flicker). With cheap LED strings from Home Depot (one multi-colored and one white), operating from 60 Hz, I do not perceive any noticeable flicker. On the white string (pre-installed on a fake tree), I do see a spatial effect due to the small luminous surface inside a glass envelope, but it is time-stationary. --- End quote --- My mom has some LED lights on a tree outside, she says she can't see the flicker, but it's very obvious to me. I took a picture with my phone while rapidly panning the phone and it clearly showed the trail of dots effect. I have always been sensitive to flicker, especially in my peripheral vision and even more so when I'm tired. Even when it's high enough frequency that it is not readily visible when starting at it, flicker still shows up when I rapidly scan my eyes past something. I'm hopeful that LED lights with proper power supplies will become common at some point, and ideally some different colors, I really don't like the lime green, saturated blue and orangish red. |
| james_s:
--- Quote from: tom66 on December 06, 2022, 09:21:28 pm ---I would guess a DC SMPS is probably cheaper than an AC transformer nowadays, plus it automatically makes the lights safe for outdoor usage (though in my experience, unless you get higher quality ones, they won't last long due to corrosion at the base of the LEDs.) --- End quote --- It probably is, but transformer powered Christmas lights were never a thing here, the first time I ever saw such an arrangement was when I met a friend in the UK that shares my interest in lighting. Ours are mostly just series strings of LEDs that are half wave self rectifying, some try to mitigate the flicker by having the LEDs staggered across two wires in opposite directions. On top of their other deficiencies, my experience is they don't even last as long as incandescent. Probably because they're run hard to make them bright enough and they have no protection from spikes. |
| tom66:
I don't think I've seen a purely mains powered set of LED fairy lights in a long time - and possibly never. Incandescent ones were nearly exclusively mains powered, even the outdoor ones usually using ruggedised cables and bulbs. I wonder if there was a regulation prohibiting them when they were introduced or at least once they became popular, grandfathering in the old design which remained for sale up until a few years ago. Not sure how it varied across the world, but the old incandescent sets in the UK used things like "fuse bulbs" (designed to blow at a lower voltage once too many 'self-shorting' filament bulbs had failed) and were notorious for leading to house fires especially on real trees; the fire brigades around here asking people to switch off their lights at night & watch pets and children around them. I have fond (and not so fond) memories of finding the dead bulbs in a set with my father. He had a little tester which contained a 9V PP3 battery, which was enough to light up the bulb (I think they were 12V/1W rated, so a common arrangement was 20-24 bulbs in series plus one fuse bulb for each 'run'.) In earlier days the flasher function was provided by another thermal bulb, like older car indicators, but it went electronic before the switch to LEDs, I would guess using triac dimmers. Nowadays, I am sure that 24V/3W SMPS costs around a dollar to make, so likely much cheaper than better insulation etc. |
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