LCD backlight overheats 7805

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  1. - 13th January 2007, 13:11 #14
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    Acetronics2
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    Hi, Sarma

    I just have MEASURED 3v9 @ 50 mA on one of my LCD Backlight ...

    so, ...

    ( 12v - 3.9v ) x .05 = 0.4 W to be dissipated ...


    now, as you do, pluggeg in the 5v with 11 Ohms

    ( 5 - 3.9 ) /11 = 100 mA !!!

    so, your 7805 is then overcharged and is close to it's maximun dissipated power before shutdown ( 130°C internal ? ) !!!

    Try a 22 Ohm resistor and everything might be Ok !!!

    Alain

    Ohm's law will still make ink flow ...
    Last edited by Acetronics2; - 13th January 2007 at 13:14.
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