XPost: uk.d-i-y, alt.home.repair   
   From: Gothberg"@internet.co.is   
      
   On Thu, 20 Dec 2018 19:11:36 -0000, Rod Speed  wrote:   
      
   > "William Gothberg" <"William Gothberg"@internet.co.is> wrote in message   
   > news:op.zubnqbkho5piw3@desktop-ga2mpl8.lan...   
   >> On Thu, 20 Dec 2018 09:36:02 -0000, Jon Fairbairn   
   >>  wrote:   
   >>   
   >>> "William Gothberg" <"William Gothberg"@internet.co.is> writes:   
   >>>> Agreed. All I can detect (with my digital camera) is that   
   >>>> one brand of LED light I have flickers about 5 times less   
   >>>> (not sure if it's smother or faster) than the others.   
   >>>   
   >>> Try a longer exposure and move the light rapidly relative to the   
   >>> camera.   
   >>   
   >> I wonder, if I fed the lamps with mains voltage DC, simply a bridge   
   >> rectifier and a huge capacitor, they'd reduce their flicker.   
   >   
   > Wont work at all if they use capacitor droppers and   
      
   I made a few of those to power LEDs to indicate the function of my central   
   heating.  I'm looking inside the flickery lamp just now (£15, 20W).  Without   
   undoing the glue holding the PSU onto the inside of it, all I can see is   
   probably: the mains going    
   through a large bipolar cap, a tiny resistor (to discharge it safely?), a   
   bridge rectifier, another very large resister (to limit the LED current more   
   accurately?), then a 400V 4.7uF capacitor (which is bulged).  A capacitor   
   dropper with a rectifier and    
   smoothing capacitor after it?  The one I made has no smoothing cap, just mains   
   to cap to resistor to bridge to LED.  Perhaps this bulged cap is why I'm   
   getting flicker, I'll try replacing it tomorrow.   
      
   > they very likely do because those are the only cheap   
   > droppers for dropping such a large voltage.   
      
   Aren't miniature SMPS units pretty cheap?  I just bought a 12V 6A SMPS for   
   £4.50.  Designed for powering LEDs - but I've looked inside it and it's   
   definitely a switched mode, not a capacitor dropper.  Now this flickery LED   
   lamp I'm looking inside, it's    
   about 20W, so 12V at 2A is all that's required, it could have had an SMPS in   
   it similar to the one I just described.   
      
   I'm now looking inside one of the better LED lamps (the non-flickery model).    
   It has a basic SMPS inside it.  They're 9W and £4 each for the whole lamp.    
   I'm sure it's more than just a standard SMPS though, because when some LEDs   
   fail short circuit (it    
   has about 40 in series), the voltage coming from the PSU drops, to maintain   
   the correct current for the remaining good LEDs.   
      
   > Very easy to try tho and see if it works.   
      
   Looks like it would help the better ones, but not the crap one.  Better (as I   
   only have a few crap ones) to stick a bigger smoothing cap inside those.  For   
   the good ones, the only problem I can foresee with the external smoother, is   
   overloading the lamp'   
   s bridge rectifier, as it will only be conducting on two of the four diodes.   
      
   >> The cheap shit LED lamp I have that actually flashes at 100Hz would most   
   >> likely get much brighter and burn out, so I'd have to adjust that, but the   
   >> others which only flicker 8% would just get 4% brighter.   
      
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