How To Protect A LED From Reverse Polarity

Discussion in 'The Projects Forum' started by haberdasherylondon, Mar 11, 2009.

  1. haberdasherylondon

    Thread Starter New Member

    Mar 11, 2009
    1
    0
    Hello.
    I'm using a 9V battery source to power 2 LED's each with a 3.5V forward Voltage. I need to protect the system from reverse polarity that might harm the LED's. I imagine that I should use a zener diode to do this, but I don't know how to specify the right diode.

    Can someone help me?

    Thanks
    -Dan
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,348
    Hello,

    A diode in series with the leds will help.
    A standard led will hold at a reverse voltage of about 6 Volts.

    Greetings,
    Bertus
     
  3. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Or you can put a conventional diode back biased compared to the LEDs. If you do reverse bias them the conventional diode will soak up the current and drop 0.7V, which most LEDs can handle OK.
     
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