XPost: alt.home.repair, uk.d-i-y   
   From: Gothberg"@internet.co.is   
      
   On Thu, 20 Dec 2018 01:31:30 -0000, Rod Speed  wrote:   
      
   >   
   >   
   > "Brian Gaff"  wrote in message   
   > news:pvdu3r$oo6$1@dont-email.me...   
   >> Well the answer as in many things these days is it depends.   
   >> Some are very simple and do have a kind of pulsing taken from ripple on   
   >> the mains. Others seem to not do this, indeed poking a phototransistor   
   >> connected to an amplifier shows many different results. the same seems to   
   >> go for CFLs as well.   
   >> You would need to know what circuit they were using etc to figure out why.   
   >> One particular led in a stood across the road has a 1khz whine when point   
   >> the device at it but modulated onto a 100 hz buzz.   
   >>   
   >> I often wonder if there is some jiggery pokery going on to drive leds hard   
   >> for split seconds to make them brighter.   
   >   
   > Yes, there is, particularly with the brighter ones like car headlights etc.   
      
   Those designers need to do more research and realise that a lot of the   
   population have eyesight good enough to detect that flicker and should   
   therefore increase the frequency of the flicker, or they're causing   
   distractions and a danger on the roads.   
      
   >> "William Gothberg" <"William Gothberg"@internet.co.is> wrote in message   
   >> news:op.zt9okmwvo5piw3@desktop-ga2mpl8.lan...   
   >>> 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.   
   >>   
   >>   
      
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