XPost: alt.home.repair, uk.d-i-y   
   From: Gothberg"@internet.co.is   
      
   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.   
      
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