Hi Keith, That's interesting info. I was theorizing that they'd have to string about 100 leds in series to drop the 169 V p (or is it pp) that comes from the wall outlet without burning out the bulbs. I don't know how they wire them though.
Ron "Watson, Keith" <[email protected]> wrote: >I'm one of those people who can also see the LED Christmas lights >flickering. I was trained as a lookout in the Navy and spent a fair >amount of time searching for targets in very dark conditions which >requires extensive use of your peripheral vision. I'm also a juggler >(used to juggle professionally) and this also trains you to use your >peripheral vision. > >Color receptors (cones) in your eye are mostly located in the center of >your visual field and need a lot of light to distinguish color. Rods >are more sensitive to shades of brightness rather than color and are >more numerous in your periphery. This is why you can see an object at >night in your periphery but it disappears when you look directly at it. > >https://en.wikipedia.org/wiki/Eye#Rods_and_cones > >You can test this yourself by looking directly at an LED Christmas >light and then looking away. As the LED moves from the center of your >vision to the periphery the LED will flicker for a brief instant. > >Incandescent lights also flicker at 60Hz but due to the thermal mass of >the filament it does a better job of integrating the light intensity so >the flickering is not as obvious. I can very rarely catch an >incandescent bulb flickering. > >LEDs don't emit light by heating up like an incandescent so they >actually turn completely on and off at 60Hz (assuming they are being >driven by an AC voltage). > >LEDs have a safe operating envelope that is a combination of peak >current and average temperature. LED brightness is directly >proportional to the current. If you run the LED continuously at its >peak current rating at room temperature it will overheat and burn out. >To get the most light and stay within the max temperature rating you >can pulse the LED on and off at its peak current and adjust the duty >cycle to stay within the max temperature at the maximum ambient >temperature you want it to run at, this is typically how LED dimmers >work. You also have to pick a frequency that is high enough that the >human eye will not detect the flicker. Most people can't see 60Hz >flicker but enough can that monitors started supporting 72Hz as a >refresh rate. > >https://en.wikipedia.org/wiki/Refresh_rate > >If the LED lights are using 60Hz as the frequency for turning the LED >on and off there are going to be people who will see the flicker. > >Despite the flickering I prefer the LED lights because they run at a >lower temperature and use less power. Depending on how the LED light >string is wired (series versus parallel) the entire string won't die >when LEDs stop working. I spent well over an hour going through an >incandescent Christmas light string that didn't work, testing and >replacing burned out bulbs. When I was done I plugged it in and it >stayed lit for all of two seconds. To fix it I would have to retest >every bulb again. Needless to say the light string ended up in the >trash. > >I'm hoping the LED Christmas lights don't suffer the same rate of burn >out and a single, or multiple bulb, failure won't result in a dead >string. I haven't owned a set long enough yet so the jury is still out. > >keith > >-- > >Keith R. Watson Georgia Institute of Technology >IT Support Professional Lead College of Computing >[email protected] 801 Atlantic Drive NW >(404) 385-7401 Atlanta, GA 30332-0280 >_______________________________________________ >tech-chat mailing list >[email protected] >http://lists.linuxmoose.com/mailman/listinfo/tech-chat -- Sent from my Android Acer A500 tablet with bluetooth keyboard and K-9 Mail. Please excuse my potential brevity if I'm typing on the touch screen. (PS - If you email me and don't get a quick response, you might want to call on the phone. I get about 300 emails per day from alternate energy mailing lists and such. I don't always see new email messages very quickly.) Ron Frazier 770-205-9422 (O) Leave a message. linuxdude AT techstarship.com _______________________________________________ tech-chat mailing list [email protected] http://lists.linuxmoose.com/mailman/listinfo/tech-chat
