XPost: alt.home.repair, uk.d-i-y   
   From: Gothberg"@internet.co.is   
      
   On Thu, 20 Dec 2018 18:55:13 -0000, Rod Speed  wrote:   
      
   >   
   >   
   > "William Gothberg" <"William Gothberg"@internet.co.is> wrote in message   
   > news:op.zubminnfo5piw3@desktop-ga2mpl8.lan...   
   >> 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.   
   >   
   > No point in doing that.   
      
   There is when half the population is capable of seeing it.  Why only sell   
   things suitable for those with shitty eyesight?  If you can't see the flicker   
   that I can, then your eyes aren't as good as mine.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)