Flicker free LED bulbs

[Mark Lloyd]

[snip]

About the frame rate of movie film. I've wondered if that has anything to do with old movies being called "flicks".

[Mark Lloyd]

[snip]

When I said I hadn't seen LED flicker, I did forget about that one. I have had a LED bulb designed to flicker, to simulate a candle flame.

[Ed P]

I've been using them for years, different brands, never noticed. Given that you have a 60hz current, it may be possible that some people would be sensitive to it. Similar to the pitch of some sounds that can drive people nuts.

I like that LED bulbs last a long time too. I did have one go bad once some years ago, but otherwise, never replaced on.

[Bob F]

I have had a few die.

[danny burstein]

well, the typical AC operated lamp (light bulb) is actually "blinking" at _twice_ that number, as it illuminates on both the (loosely speaking) "up" and "down" stroke...

So that 25CPS [a] lamp is actually usually blinking

50 times/second. (and the standard US 60hz is flashing 120 times/sec...)

sidenote: back 1975ish I was in the NYC subway station right next to Penn Station, and the incandescent lamps were... yes .. wired to the 25 CPS of the rail road supply. Who knows why?

Anyway, it was a super cold winter, about zero F, and yes, I definitely saw the flickering.

Hmmmm... I don't know about the early movie projectors, but don't the modern ones, umm, make that 1940ish?, do a double flash od each fram?

[a] ain't none of this silly "Hertz" deal back then..

[micky]

I forgot to include the link:

AFAICT, most people don't even notice when led's flicker, including some who "notice" it sublimally and can get headaches etc.

[micky]

Absolutely, but it's not because the light source flickers. It's because the image did, as it changed from frame of the movie film to the next.

Movie theatres tended to use arc-lamps,because they are bright enough, and although I read that their power was DC, I don't know where a movie theatre would get DC power.

"Carbon arc lighting left its imprint on other film projection practices. The practice of shipping and projecting motion pictures on

2,000-foot reels, and employing "changeovers" between two projectors, was due to the carbon rods used in projector lamphouses having a lifespan of roughly 22 minutes (which corresponds to the amount of film in said reels when projected at 24 frames/second). The projectionist would watch the rod burn down by eye (though a peephole like a welder's glass) and replace the carbon rod when changing film reels. The two-projector changeover setup largely disappeared in the 1970s with the advent of xenon projector lamps, being replaced with single-projector platter systems, though films would continue to be shipped to cinemas on 2,000-foot reels."

Complete with pictures:

Later, a small white rectangle was made to appear in the upper right corner on the screen when it was about time to change reels. I suspect one can still see this on old movies, even after they've been digitized and there are no reels to change. .

[hubops]

The old-timers said that they could discern the sound of the 25 Hz. from the 60 Hz. " the 25 cycle hum " .. of the big power transformers. I can't say that I could hear it - must have been the wet behind my ears .. John T.

[danny burstein]

For reasons I don't quite agree with, but 'dem's da breaks, the so-called "60 Hz hum" people hear from transformers is ususually actually 120 Hz...

[T]

Thank you!

[Ed P]

The flicker of the lights is also a dangerous thing to be aware of. The container ship Dali was entering the Baltimore Port and the lights flickered. Soon after, it hit the bridge and knocked it down.

Reliable sources say the pilot hit the light button and caused the problem and the trainee did not drop the starboard anchor.

[JRB Ware]

That has to be one of the dumbest things ever posted here.

[Bob F]

He's just trying to compete in kind with Big Thumb Wannabe Rod Speed.

[Clare Snyder]

Many decades ago it was done that way here too - back when you had no meter and you paid for power by the number of lighting devices and the number of "power points" - and you had 2 circuits - and 2 fuses. The only things that you could plug into the power points were things like toasters and irons - and mabee fans or space heaters because that's all you could buy - - - Funny how parts of Europe and possibly(parts of) the UK still do things that way

[Clare Snyder]

"best practice" back in the 70s and 80s was receptacles in one room on one circuit - along with lights in another room - so if you overloaded an outlet and tripped the breaker you were not left in the dark in that room. That was the way my dad - a licenced electrician - laid things out when wiring houses. Virtually every room was served by AT LEAST 2 circuits

[danny burstein]

[snip]

Kind of a similar situation, more or less, for "public street lighting".

The utilities in many parts of the US simply charge the Local Authority Having Jurisdiction a flattish rate based on, more or less, what the luminaires would draw on ten hours of use (at the very low.. off peak rate)...

[Clare Snyder]

I've even seen basements wired with telephone wire - the old copper coated steel "twinlead" external overhead phone wire. Looks like 300 ohm twinlead antenna cable but 14 or 16 guage solid conductor

[Clare Snyder]

any line voltage LED that uses a switch mode power supply will NOT have 60Hz flicker because they run at a much higher frequency to minimize the inductor and transformer sizes

[Clare Snyder]

Actually I do have one lighting circuit with LEDs that flickers when dimmed. Dimmable bulbs. Tried 3 different dimmers. Tried 2 different brands of bulbs. It is a slow irregular flicker. All connections have been checked - no flicker with incandescents or when full bright. Dlicker regardless if there is anything else running in the house - and other lights don't flicker. The only thing I have not done is change the actual sockets

[micky]

Not a rectangle. Two dots. " to trained personnel, the two sets of dots appearing on the screen on the top right corner every 15 minutes indicated that a change-over was about to take place."