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LED fairy lights.

Discussion in 'Lighting' started by Clive Mitchell, Dec 20, 2003.

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  1. I've put some pictures on my site that show some hacked LED fairy lights
    from Habitat in the UK, which have been transformed from bland
    all-yellow LED lights to full colour red, orange, yellow, green and
    blue.

    To elaborate... The lighting chain as supplied uses 10 series circuits
    of ten LEDs wired in parallel just like normal low voltage fairy lights,
    and the lampholders are just the same ones as used for the filament
    based versions, but with the LED leads stuck in and folded back, while
    the LEDs themselves just butt against the lampholder.

    There are no series resistors. The circuit relies on the load
    regulation of a standard 18V DC transformer, and the theoretical voltage
    match of all the circuits.

    I modified a few sets by swapping in different colours of LEDs in equal
    quantities of two of each colour in each set of ten. The increased
    forward voltage and the inherent unpredictability of cheap crappy
    imported blues and greens from dubious Chinese "manufacturers" (probably
    individuals selling graded stock!), meant that I decided to add a 330
    ohm series resistor in each series circuit by soldering and
    heatshrinking it into the series wiring. For a power supply I just used
    a standard 24V AC transformer with a 1A rectifier and a large smoothing
    capacitor, which gives a voltage of about 30V under load. The LED
    series voltage is about 25V so the 330 ohm resistor drops 5V and gives
    about 15mA.

    You can see the results at:- http://www.bigclive.com in the temporary
    gallery section.

    Very, very nice.

    Habitat are selling the original 100 LED sets at about ten UKP which
    makes them very affordable for hacking. If you just use "Autumn"
    colours (red, orange and yellow), then they can run from the existing
    PSU and circuit configuration as long as you use equal numbers of
    specific colours in each series circuit. I used -
    R-O-Y-R-O-Y-R-O-Y-Y. It's a very nice colour combination, but just make
    sure you use the super high output LEDs with a forward voltage of about
    1.8V.

    Remember to match the polarity too!
     
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