sorry, the finger shook and doubletapped. I am going to pay more attention to the christmas tree light shake. I haven't put up a string of lights at home for 9 or 10 years. Wolf Halton -- http://wolfhalton.info Apache developer: [email protected] On Dec 13, 2013 12:28 PM, "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 >
_______________________________________________ tech-chat mailing list [email protected] http://lists.linuxmoose.com/mailman/listinfo/tech-chat
