XPost: alt.home.repair, uk.d-i-y   
   From: Gothberg"@internet.co.is   
      
   On Wed, 19 Dec 2018 18:33:09 -0000, Rod Speed  wrote:   
      
   >   
   >   
   > "William Gothberg" <"William Gothberg"@internet.co.is> wrote in message   
   > news:op.zt9sk9gco5piw3@desktop-ga2mpl8.lan...   
   >> On Wed, 19 Dec 2018 12:28:04 -0000, Rod Speed    
   >> wrote:   
   >>   
   >>>   
   >>>   
   >>> "William Gothberg" <"William Gothberg"@internet.co.is> wrote in message   
   >>> news:op.zt9qc10co5piw3@desktop-ga2mpl8.lan...   
   >>>> On Wed, 19 Dec 2018 11:51:35 -0000, Rod Speed    
   >>>> wrote:   
   >>>>   
   >>>>> William Gothberg <"William Gothberg"@internet.co.is> wrote   
   >>>>>   
   >>>>>> Do switch mode power supplies flicker in time with mains?   
   >>>>>   
   >>>>> No.   
   >>>>>   
   >>>>>> Specifically LED power supplies in commercially available domestic   
   >>>>>> lamps.   
   >>>>>   
   >>>>> None of mine flicker at all.   
   >>>>>   
   >>>>>> 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?   
   >>>>>   
   >>>>> None of mine flicker at all.   
   >>>>>   
   >>>>>> And is there any way I can test this?   
   >>>>>   
   >>>>> Yes, Get or make a strobe disk or use   
   >>>>> one of the original LP disks that has   
   >>>>> a strobe disk on it and see what it looks   
   >>>>> like with the lights illuminating it. You'll   
   >>>>> get it appearing to freeze when rotating   
   >>>>> if the light level is varying in synch with   
   >>>>> the mains frequency.   
   >>>>>   
   >>>>>> 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.   
   >>>>>   
   >>>>> Or they don't flicker at all. No reason why a proper   
   >>>>> switched mode power supply needs to have any   
   >>>>> AC component at all on its output. The cruder   
   >>>>> ones may well do.   
   >>>>   
   >>>> They probably are fairly crude.  I know they flicker, for example if I   
   >>>> use   
   >>>> my cordless drill, the chuck appears to spin the wrong way under the LED   
   >>>> lighting.   
   >>>>   
   >>>> But it's nothing like as low as 50Hz.  What I want to know is if the   
   >>>> higher frequency they're flickering at is anchored with the rise of the   
   >>>> AC   
   >>>> wave.   
   >>>   
   >>> No its not.   
   >>>   
   >>>> I.e. will all the LED lights in the room flicker at precisely the same   
   >>>> time, or will they be out of synch (due to tolerances in the circuitry   
   >>>> of   
   >>>> each PSU)   
   >>>   
   >>> Due to it not being synched with the mains, actually.   
   >>   
   >> I meant if the PSUs were absolutely identical,   
   >   
   > They never can be.   
      
   Yes I know.  It was hypothetical.   
      
   >> and all the lights were switched on at the same time (with one   
   >> lightswitch), they should remain in synch forever.   
   >   
   > Nope, because the frequency at which the PSU works is entirely   
   > determined by the component tolerances when it isnt operating   
   > at 50Hz because it isnt a simple capacitance dropper.   
   >   
   >> But since there are tolerances in all the components in the PSUs,   
   >   
   > Most of the components in the PSU don't determine the frequency   
   > it operates at.   
   >   
   >> they won't stay in time.   
   >   
   > They never will without an explicit design that keeps   
   > the frequency in synch with the mains and there is no   
   > point in the extra components to do that, so they don't.   
      
   Which is what I thought.   
      
   > The only exception is very simple capacitance droppers   
   > that operate at mains frequency and the effect you are   
   > getting with the drill chuck proves that yours arent that.   
   >   
   >>>> and fudge the brightness together.   
   >>>   
   >>> Its not a fudge, it's the lack of synch.   
   >>   
   >> I didn't mean fudge, I meant smudge.   
   >>   
   >>> And you should be able to see that by watching   
   >>> the chuck as you move the drill between lights.   
   >>> The rate and direction of rotation should change.   
   >>   
   >> Only if the frequency is different, which I doubt as they are all the same   
   >> model.   
   >   
   > The frequencys will be slightly different   
   > because of component variation.   
      
   I would have thought so, so why is it that in my room with 10 such lights, I   
   still get flicker.  Shouldn't they fill in each other's gaps?   
      
   >> What I need is a way of detecting if they're flashing together.   
   >   
   > Like I said, do the drill chuck thing with all the   
   > lights on at night and move the drill between   
   > lights relatively close to the lights.   
      
   Just did that and proved nothing.  Clearly I get the same effect under every   
   light, as they'll be pretty similar frequencies.  I'm not going to be able to   
   tell the difference between them with something as simple as a drill chuck.    
   Presumably they're    
   something like 1995 Hz, 2001 Hz, 2003 Hz, etc.  All I can think of to prove it   
   would be a higher speed camera so I can spot them being on at different times.   
      
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