On Thu, 20 Dec 2018 03:09:44 -0000, "William Gothberg" "William
wrote:

On Thu, 20 Dec 2018 01:31:30 -0000, Rod Speed wrote:



"Brian Gaff" wrote in message
news
Well the answer as in many things these days is it depends.
Some are very simple and do have a kind of pulsing taken from ripple on
the mains. Others seem to not do this, indeed poking a phototransistor
connected to an amplifier shows many different results. the same seems to
go for CFLs as well.
You would need to know what circuit they were using etc to figure out why.
One particular led in a stood across the road has a 1khz whine when point
the device at it but modulated onto a 100 hz buzz.

I often wonder if there is some jiggery pokery going on to drive leds hard
for split seconds to make them brighter.

Yes, there is, particularly with the brighter ones like car headlights etc.

Those designers need to do more research and realise that a lot of the population have eyesight good enough to detect that flicker and should therefore increase the frequency of the flicker, or they're causing distractions and a danger on the roads.

"William Gothberg" "William wrote in message
news Do switch mode power supplies flicker in time with mains? Specifically
LED power supplies in commercially available domestic lamps. By in time,
I don't mean at the same 50/60Hz, but anchored to it. I.e. if you have
several such lamps each with their own built in supply, will they all
flicker in time, using the mains frequency to keep them in time, or will
they be random, making the room overall not flicker due to them all being
random? And is there any way I can test this? I tried taking photos of
them, but my camera only goes as fast as 1/2000th of a second, which
shows all the lights at the same brightness each time, I suspect the
flicker is above 2000Hz.


PLONK