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LEDs for high impact environment

Discussion in 'Electronic Basics' started by SR, May 12, 2004.

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  1. SR

    SR Guest


    Looking to use LEDs as decorating lights inside clear acrylic music drums.
    Will these stand up to the beating? . I was thinking of mounting them in
    clear plastic tube about 1/4to 1/2 inch diameter , looped to fit inside the
    drum, and connected in parallel (?) say 20 . What sort of power supply will
    I need? could I use dry cells?


  2. The LEDs are quite vibration resistance, since they are solid (chips
    potted in epoxy). The only thing you might have problems with are the
    connecting wires breaking off from flexing, and fine stranded wire
    should make that pretty unlikely. I would connect them in series and
    drive them with a single current. The exact voltage you need depends
    on what color LEDs you use. Red ones drop about 1.7 volts, orange,
    yellow and yellow-green ones about 2 volts and green blue or white
    ones drop 3 to 3.5 volts each. The cheap way to control the current
    is to have a DC supply that is 20 to 30% higher than the drop of the
    LEDs and waste the extra voltage with a series resistor. For
    instance, if you connected 20 3 volt, 20 milliamp green LEDs in series
    (60 volts total) you might use a 75 volt DC supply with a 750 ohm 1/2
    watt resistor in series. Or you could divide them into two strings of
    10, (30 volts needed to light the LEDs) and use a 40 volt supply with
    a 510 ohm 1/2 watt resistor in series with each string.

    If you connect them in parallel, you need to add a small resistor in
    series with each one to help them share current better. Otherwise the
    one that takes the least voltage to light will hog all the current and
    burn out. If you were using green LEDs you might use a 5 volt supply
    and add a 100 ohm 1/4 watt resistor in series with each LED. This
    passes about .02 amps to each LED but 20 in parallel would require a
    supply capable of delivering 20 * .02 = .4 amperes. But small DC
    receptacle mounted supplies (wall warts) in this range are available
    for 5 to 10 dollars.
  3. SR

    SR Guest

    All the info I needed in one reply - Well thank you Sir, very much

    Gotta love the internet for enabling the BEST of humanity to cut through!

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