Help with simple LED circuit

Discussion in 'General Electronics Chat' started by noingwhat, Jul 23, 2010.

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  1. noingwhat

    Thread Starter Member

    Jul 23, 2010
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    Hi! I am pretty new to circuitry (working on my first few projects). One of my projects was an LED flashlight hat. I had wired it up and everything, and it worked great. I used two 9v batteries in series with 5 LEDs in series, meaning each LED was recieving approx. 3.6v each. I have used the LEDs with 6v ea. using two 3v batteries wired in series, and it just made the LEDs really bright so I figured if I added another 9v battery meaning a total of 27v, that would be 5.4v per LED and it would just make it really bright. So I added it in and... It blew the LEDs. All five of them. Can anyone explain why, I do not understand why 5.4 blew the LEDs when 6v didn't.
     
  2. tom66

    Senior Member

    May 9, 2009
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    5.4 volts is well above the rating of the LEDs (usually no more than 4 volts is acceptable for blue/white LEDs, and no more than 3 volts for others), what colour were your LEDs?

    For higher brightness I suggest the calculator:
    http://led.linear1.org/1led.wiz

    Use 25mA for the forward current, this will make your LEDs glow really bright.
     
  3. Wendy

    Moderator

    Mar 24, 2008
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  4. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Bill_Marsden is right, one thread is enough.
    Lets continue in the other thread.

    Bertus
     
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