-september.org> 0ec34ec0   
   XPost: alt.home.repair, uk.d-i-y   
   From: Gothberg"@internet.co.is   
      
   On Thu, 20 Dec 2018 08:19:58 -0000, gregz  wrote:   
      
   > 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)   
   >>   
   >>  (also rules out the previously mentioned "engineer friend")   
   >   
   > Lights flicker at twice the frequency, once for positive cycle, and once   
   > for negative cycle. LEDs only once unles using a bridge rectifier, or   
   > steady on using DC. Even though blinking they look normal straight on, my   
   > brain says something is wrong   
      
   Some brains (or eyes) seem to be faster than others.  I can easily (and   
   annoyingly) see flicker on CRT monitors below 90Hz, others don't even see the   
   50 or 60Hz ones.  I can see flicker on 80% of car LED lights, others don't see   
   any.  Designers really    
   ought to account for those of us with better eyesight.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)