XPost: alt.home.repair, uk.d-i-y   
   From: Gothberg"@internet.co.is   
      
   On Thu, 20 Dec 2018 04:34:08 -0000, Clare Snyder  wrote:   
      
   > On Wed, 19 Dec 2018 19:34:57 -0000, "William Gothberg" <"William   
   > Gothberg"@internet.co.is> wrote:   
   >   
   >> On Wed, 19 Dec 2018 18:03:19 -0000, Clark W. Griswold  wrote:   
   >>   
   >>> On 12/19/2018 11:36 AM, William Gothberg wrote:   
   >>>> On Wed, 19 Dec 2018 16:18:29 -0000, Mark Lloyd  wrote:   
   >>>>   
   >>>>> On 12/19/18 5:23 AM, William Gothberg wrote:   
   >>>>>> 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.   
   >>>>>   
   >>>>> I once had an audio amplifier with a solar cell rather than a microphone   
   >>>>> for the input transducer. This made it possible to listen to light. The   
   >>>>> sun is steady, incandescent lights (AC powered) hum.   
   >>>>>   
   >>>>> That was 40 years ago. Maybe something like that would work today.   
   >>>>   
   >>>> The trouble is I want to compare 2kHz+ from one light with 2kHz+ from a   
   neighbouring light and see if they're in sync.   
   >>>   
   >>> Maybe use a dual trace oscilloscope?   
   >>   
   >> Haven't got one unfortunately.   
   >>   
   >>> Since this landed in alt.home.repair, I gotta ask.  Do you have   
   single-phase or two-phase?   
   >>   
   >> Single.  I'm in the UK.   
   >  so 50 Htz - you can almost see an incandescent flicker at that   
   > frequency (at 25 you could)   
      
   I was assuming it was higher frequency than that, from the SMPS.  But I'm   
   thinking they don't have one - see my other reply where I used the camera on a   
   long exposure.   
      
   >  (also rules out the previously mentioned "engineer friend")   
      
   Who?   
      
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