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Christmas LED light strings

Discussion in 'Lighting' started by JohnR66, Nov 7, 2005.

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  1. JohnR66

    JohnR66 Guest

    I've been looking for these LED light strings for a couple years to show in
    the stores and I never see them. Well, in a Meijers store for another
    reason, I swung down the Christmas decoration isle and to my surprise, I saw
    LED light sets! There were 70, 25 and icicle sets. I got the 70 light
    string. Price was $8.44

    My analysis:

    These have a green wire with two circuits of 35 LEDs on each. LED is glued
    or embedded in little plastic colored flame shaped "bulbs". They are
    permanently glued to the sockets as they claim no replacements necessary.

    Colors are: yellow, orange, red, green (seems to be the aqua colored LED)
    and blue. For every green and blue LED, there are 2x the other colors
    (perhaps a voltage drop or cost issue). They seem to be as bright as the
    standard miniature light strings but with vibrant colors.

    Strobing effect is quite apparent since each LED is on for a half cycle and
    probably only near the peak voltage anyway. Power draw is around 2 watts.
  2. Are the LEDs in series across the mains like the foreverbrite lights?

    Here in the UK our LED strings tend to be run from the industry standard
    24VAC transformers for outdoor lighting. There's an inline rectifier
    and the LEDs are wired in strings of 7 or 8 LEDs with a resistor (if
    you're lucky!). The Gallium Arsenide versions use strings of 10 LEDs and
    a resistor.

    The flicker is there but not noticeable at 100Hz. (50Hz supply)

    The quality is getting higher.
    The use of a lower number of blues and greens is probably a cost and
    reliability issue. The Gallium Nitride blues and greens are much less
    reliable in low cost consumer goods. The real test is how long the LED
    strings last. Leave it on permanently as part of your analysis.
    In the UK a retail chain called Habitat was selling LED lights last year
    that used the AC to create a neat effect. Each LED was actually a red
    and blue chip in inverse parallel so that the lights lit a different
    colour on each half of the sine wave. Looking directly at them they
    look purple, but as soon as you eye moves you get a psychedelic red and
    blue strobing effect.
  3. JohnR66

    JohnR66 Guest

    They use a full wave rectifier? The ones here definitely flicker at 60Hz. I
    put a diode in series and the front half of the string came on. When I
    reversed the diode, the other end only lit.
    That would be a neat effect!
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