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need help with low voltage led circuit

Discussion in 'Electronic Basics' started by Tgriff346, Sep 28, 2004.

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  1. Tgriff346

    Tgriff346 Guest

    I need to build a board with painted animals( got it) with led eyes that light
    up at night. I've tried to wire it up, but the led bulbs keep burning out. I am
    using a 9 voltbattery. Any wiring suggestions?
     
  2. If LEDs are burning out, it's almost certain to be your circuit. Perhaps you
    have no current limiting for the LEDs against the 9V source? But none of us are
    psychic, so what's the circuit you are currently using?

    Jon
     
  3. John Fields

    John Fields Guest

    ---
    Connect one 390 ohm quarter watt resistor between each LED and the
    battery.

    View with a fixed pitch font like Courier:

    +---[390R]---[LED>]---+
    | |
    +---[390R]---[LED>]---+
    | |
    . .
    . .
    . .
    | |
    +---[390R]---[LED>]---+
    |+ |
    [BATTERY] |
    |- |
    +---------------------+
     
  4. John Larkin

    John Larkin Guest

    Just two led's? Connect them in series, with a resistor in the
    circuit.

    Battery+-------resistor------led1------led2-------battery-
    A K A K

    A = led anode
    K = led cathode

    try 470 ohms for the resistor to start. The lower the resistance, the
    brighter the led's and the shorter the battery life. Don't go below,
    say, 150 ohms. The limiting case is R=0, infinite brightness, dead
    LED, which is what you're doing now.

    John
     
  5. You need a current limiting resistor in series with each LED -
    something around 1000 ohms should be OK (the value is not critical -
    lower resistance gives more current, and a brighter LED).
     
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