XPost: alt.home.repair, uk.d-i-y   
   From: Gothberg"@internet.co.is   
      
   On Thu, 20 Dec 2018 04:03:06 -0000, Clare Snyder  wrote:   
      
   > On Wed, 19 Dec 2018 12:49:47 -0000, "William Gothberg" <"William   
   > Gothberg"@internet.co.is> wrote:   
   >   
   >> 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, and all the lights were   
   switched on at the same time (with one lightswitch), they should remain in   
   synch forever.  But since there are tolerances in all the components in the   
   PSUs, they won't stay in time.   
   >>   
   >>>> 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.  What I need is a way of detecting if they're flashing together.   
   >   
   > Why???  If the frequency is IDENTICAL (unlikely with production   
   > "tolerances" of consumer grade SMPS wall warts) the chance of them   
   > being EXACTLY in phase is remote at best as the "clock" trigger is   
   > generally not based on the mains frequency. Even if they STARTED   
   > exactly in phase, the frequency drift of the SMPS clock would take   
   > them out of synch pretty quickly - and they would go in and out of   
   > phase over time.   
      
   That's what I was asking, if the output frequency was synched to the mains   
   frequency.   
      
   > And why do ypu NEED to know if they are synched?  Just curious.   
      
   Because if I have several lights in one room, and they are out of sync, the   
   flicker is less of a problem, as one will fill in the gaps of the other.   
      
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