Number of LEDS per 9 V battery

Discussion in 'General Electronics Chat' started by dd1313, May 24, 2010.

  1. dd1313

    Thread Starter New Member

    May 23, 2010
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    Hi Guys

    Will putting 30 flashing LEDs to a 9V battery work.

    Thanks
    Devan
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    Not for long. If all of them are flashing LEDs, they will each need their own path and resistor. If each pulls 20ma, then 30 X 0.02 then the total current is 0.6A. Figure on limiting 9V batteries to 0.1A, and then the life will be short.

    You can use none blinking diodes in series to drastically reduce that current, but 9V batteries just don't have much juice in them.

    Do you have a datasheet of the LED you are thinking of using?

    Even "C" or "D" cells won't last long, but maybe long enough (an hour or more). Radio Shack has some pretty good battery holders at reasonable prices.
     
  3. dd1313

    Thread Starter New Member

    May 23, 2010
    14
    0
    Not as yet mate, will get them later today.How long do you think they will work for.

    Devan
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    A 9V will last only minutes. You really need something with a deeper draw.

    I am probably underestimating the life of the 9V though thinking about it, since these LEDs are flashing (which means they stay off ½ the time or so).

    How long do you need it to last?
     
  5. Wendy

    Moderator

    Mar 24, 2008
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  6. Audioguru

    New Member

    Dec 20, 2007
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    If you use simple current-limiting resistors for the LEDs then they will be bright when the 9V battery is new and you will see the LEDs dimming for the entire 15 minutes to 30 minutes life of the battery.
     
  7. flat5

    Active Member

    Nov 13, 2008
    403
    17
    Still, it's more fun than watching paint dry :)
     
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