XPost: alt.home.repair, uk.d-i-y   
   From: rod.speed.aaa@gmail.com   
      
   "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.   
      
   > "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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