Seems to me that half wave rectified 60 cycle AC would give you a 60 cycle frequency with a 50% duty cycle. Full wave rectification would result in 120 cycle frequency with 100% duty cycle. The human eye can only see so fast so that movies at 30 frames per second (32?) appear flicker. and maybe the brighter the light is, the more it is imprested on our eyes and less likely to flicker. But I do think that sometimes we can see a florescent light flicker (not sure if that is full wave or half wave, but back in my days when neon bulbs were used like led's, they turned on at a high voltage and turned off near zero volts.) Bill I can see a humming bird flap it's wings. So there! Pookie (the dog) ----- Original Message ----- From: "Robert Rolf" To: "Microcontroller discussion list - Public." Sent: Wednesday, December 14, 2005 4:40 PM Subject: Re: [OT:] Impressive lighting effects. LED lights >M Graff wrote: >> Dave Lag wrote: >> >>> I was going to scale back myself this year,( nothing to speak of - half >>> dozen rope lights, snowmen, trees) considering electricity prices etc... >> >> >> That's one nice thing about dimmable lights. I can have the same number >> of lights installed, but if I just use full-on for effects, and use half- >> or even quarter-brightness for most strings, I have a well-lit house that >> costs much less to run. >> >> BTW, I noticed LED bulbs, which I bought several strings of, flicker. I >> wonder if that is because they only use half the sine wave and I'm seeing >> the 50% duty cycle or if they full-wave rectify and i'm seeing the 120 Hz >> zero-crossings... > > MOST LED strings use half wave rectified AC. > As a result they have about a 30% duty cycle since they only > light up brightly on the top 1/3 of the cycle so the flicker is obvious, > particularly if you pan your eyes across them. > > I added full wave bridge to mine. Much less flicker, and about > twice as bright. Then I added 470uF 220VDC cap to the bridge (per > 4 watt string). BRIGHT. Much less flicker. > [120VAC 60Hz input. ~150VDC output]. > Not sure how long they're going to last now. Have to do some > clip leading to be able measure the peak DC current. > 5 year warranty . > > Robert > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist