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LED flasher

Discussion in 'Hobby Electronics' started by #HISH, Feb 26, 2004.

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  1. #HISH

    #HISH Guest

    Hi All,
    Im looking for a simple LED flasher circuit that will accept a 9v supply
    (battery) and has a run time of ~8 weeks. I have found a few IC based
    circuits but I was looking to go even simpler so I can do away with a board
    altogether.
    Cheers
    Wayno
     
  2. Bill Bailley

    Bill Bailley Guest

    Any number of led's with the flasher circuitry built in. Go to Jaycar here.

    http://www1.jaycar.com.au
     
  3. If you want the simplist solution available, use a flashing LED. The
    flash circuit is built into the LED.
    Are you stuck with using a 9V battery? If you want really long life, a
    single D cell is a good way to go. You can get single or dual cell LED
    flasher chips. 9V batteries have poor energy density and are more
    expensive.

    Regards
    Dave :)
     
  4. Bob M

    Bob M Guest

    How long do you want the LED lit verses off? How bright? What colour?
    There isn't much energy density stored in a 9 volt battery. 8 weeks is
    a LONG time!

    A single CMOS 555 chip connected as an oscillator with the LED in
    series with the discharge lead would probably be the most energy
    efficient. I would also recommend that you consider 6 or even 4.5
    volts as a power source (3 X D cell). A red high efficiency LED is a
    current device that only requires a low voltage to operate and
    probably will give you the brightest flash with the smallest amount of
    current drain to get you near the 8 weeks operation on one set of
    batteries. Besides the 8 pin chip, all you need is a couple of
    resistors and a capacitor. This could easily be wired point to point
    on a piece breadboard.

    A couple of more details would be helpful. What's it for?

    I purchased flashing LED modules for my kids to wear when they are
    riding their bicycles. I found them at a discount store for 99 cents
    each, the regular price was 8.99. They operate on a two AA cell and
    allow you to select 1 of 3 different flashing "modes". In the early
    spring and late fall, they go to Canoe/Kayak practise early in the
    morning (5AM) and wear these on the river so they don't get hit by
    rowers practising. Batteries last about 2 weeks worth of practises-
    guessing about 16-25 hours of actual operation. Be aware that some of
    these units use very expensive button style batteries with limited
    operational life. If you go this route, choose carefully.

    Cheers from Canada

    Bob M
     
  5. Phil Allison

    Phil Allison Guest


    ** An Energiser 9 volt battery has 625 mAh with an average voltage of 7.2
    volts = 4.5 Wh.

    An Energiser D cell has 18 Ah with an average voltage of 1 .1 volts =
    19.8 Wh.

    Allowing for the size difference (17.0 cc versus 58 cc ) the 9 volt
    battery is not too bad at 0.26 Wh/cc compared to 0.34 Wh/cc.



    ............ Phil
     
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