[time-nuts] Hi Power LED Light power supply...

Dennis Ferguson dennis.c.ferguson at gmail.com
Tue Sep 18 19:28:23 UTC 2012


On 18 Sep, 2012, at 15:06 , John Lofgren wrote:

> <snip>
> I would hence believe that a 50 Hz flicker must be pretty close to the edge of what can be perceived, so I'm having trouble believing that a flicker at more than twice that rate would be perceptible at all by anyone.
> <snip>
> 
> Oh, but it is.  A couple of years ago I bought one of the Chinese 30 LED spot light bulbs for about $8 on ebay.  I thought I'd give it a try for a workbench light.  When I plugged it in at work (60 Hz power, here) the two guys standing behind me yelled "gaahhh" at the same time I did.  The flicker was horrendous.  The earlier comment about peripheral vision also applies, though.  It's worse in the periphery than in direct view.
> 
> The "power supply" is nothing more than a bridge rectifier, two current limiting resistors, and a filter capacitor.  The capacitor obviously wasn't big enough, though, because it flcikered plenty.

Or could the problem have instead been that one side of the
bridge wasn't working, so you were getting a 60 Hz flicker
rather than 120 Hz?

Having seen what I am sure was a 50 Hz flicker, I'd believe
that 60 Hz might look awful but I still have some doubt about
120 Hz.

Dennis Ferguson


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