On Wed, 19 Dec 2018 18:33:09 -0000, Rod Speed wrote:
"William Gothberg" "William wrote in message
news
On Wed, 19 Dec 2018 12:28:04 -0000, Rod Speed
wrote:
"William Gothberg" "William wrote in message
news
On Wed, 19 Dec 2018 11:51:35 -0000, Rod Speed
wrote:
William Gothberg "William wrote
Do switch mode power supplies flicker in time with mains?
No.
Specifically LED power supplies in commercially available domestic
lamps.
None of mine flicker at all.
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?
None of mine flicker at all.
And is there any way I can test this?
Yes, Get or make a strobe disk or use
one of the original LP disks that has
a strobe disk on it and see what it looks
like with the lights illuminating it. You'll
get it appearing to freeze when rotating
if the light level is varying in synch with
the mains frequency.
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.
Or they don't flicker at all. No reason why a proper
switched mode power supply needs to have any
AC component at all on its output. The cruder
ones may well do.
They probably are fairly crude. I know they flicker, for example if I
use
my cordless drill, the chuck appears to spin the wrong way under the LED
lighting.
But it's nothing like as low as 50Hz. What I want to know is if the
higher frequency they're flickering at is anchored with the rise of the
AC
wave.
No its not.
I.e. will all the LED lights in the room flicker at precisely the same
time, or will they be out of synch (due to tolerances in the circuitry
of
each PSU)
Due to it not being synched with the mains, actually.
I meant if the PSUs were absolutely identical,
They never can be.
Yes I know. It was hypothetical.
and all the lights were switched on at the same time (with one
lightswitch), they should remain in synch forever.
Nope, because the frequency at which the PSU works is entirely
determined by the component tolerances when it isnt operating
at 50Hz because it isnt a simple capacitance dropper.
But since there are tolerances in all the components in the PSUs,
Most of the components in the PSU don't determine the frequency
it operates at.
they won't stay in time.
They never will without an explicit design that keeps
the frequency in synch with the mains and there is no
point in the extra components to do that, so they don't.
Which is what I thought.
The only exception is very simple capacitance droppers
that operate at mains frequency and the effect you are
getting with the drill chuck proves that yours arent that.
and fudge the brightness together.
Its not a fudge, it's the lack of synch.
I didn't mean fudge, I meant smudge.
And you should be able to see that by watching
the chuck as you move the drill between lights.
The rate and direction of rotation should change.
Only if the frequency is different, which I doubt as they are all the same
model.
The frequencys will be slightly different
because of component variation.
I would have thought so, so why is it that in my room with 10 such lights, I still get flicker. Shouldn't they fill in each other's gaps?
What I need is a way of detecting if they're flashing together.
Like I said, do the drill chuck thing with all the
lights on at night and move the drill between
lights relatively close to the lights.
Just did that and proved nothing. Clearly I get the same effect under every light, as they'll be pretty similar frequencies. I'm not going to be able to tell the difference between them with something as simple as a drill chuck. Presumably they're something like 1995 Hz, 2001 Hz, 2003 Hz, etc. All I can think of to prove it would be a higher speed camera so I can spot them being on at different times.