XPost: alt.home.repair, uk.d-i-y
From: Gothberg"@internet.co.is
On Thu, 20 Dec 2018 16:19:47 -0000, trader_4 wrote:
> On Wednesday, December 19, 2018 at 11:03:21 PM UTC-5, Clare Snyder wrote:
>> On Wed, 19 Dec 2018 12:49:47 -0000, "William Gothberg" <"William
>> Gothberg"@internet.co.is> wrote:
>>
>> >On Wed, 19 Dec 2018 12:28:04 -0000, Rod Speed
wrote:
>> >
>> >>
>> >>
>> >> "William Gothberg" <"William Gothberg"@internet.co.is> wrote in message
>> >> news:op.zt9qc10co5piw3@desktop-ga2mpl8.lan...
>> >>> On Wed, 19 Dec 2018 11:51:35 -0000, Rod Speed
>> >>> wrote:
>> >>>
>> >>>> William Gothberg <"William Gothberg"@internet.co.is> 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, and all the lights were
switched on at the same time (with one lightswitch), they should remain in
synch forever. But since there are tolerances in all the components in the
PSUs, they won't stay in
time.
>
>
> Forget the component tolerances. Two mechanical light switches can't be
> synced to turn on the power at exactly the same time, anywhere close
> enough to sync them up to begin with.
Er.... I have more than one light running off one switch, many people do. A
large room normally has more than one light fixture, or a fixture with several
bulbs in it.
> You would need electronic
> switches driven by a common signal. And even then, even with components
> of sufficient tolerance, which is impossible, I'm not sure it would work.
> First thing that comes to mind is the freq source, which I'm guessing
> is a crystal. You could have crystals with theoretically identical
> frequencies, but I'm not sure that means they will start oscillating
> at exactly the same instant so there is no phase difference.
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