Blinking circuit using hig power Truck LED lights

Discussion in 'The Projects Forum' started by steven2410, Jul 10, 2014.

  1. steven2410

    Thread Starter New Member

    Jul 7, 2014
    16
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    So recently, i got to build this simple blinking led circuit using 555 timer from instructable: http://www.instructables.com/id/Flashing-LED-using-555-Timer/.
    Now, for a project i'm doing, I need to build a similar thing but the light source has to be clearly visible from a distance (~30m). I'm thinking of using truck taillight as a light source (one of these maybe: http://www.princessauto.com/pal/en/Tail-Lights/4-in-LED-Stop-Turn-Tail-Light/8126047.p)
    Since it's no longer a single LED circuit, I don't know the intructables circuit would work anymore (dont really want to waste $29 to test it out). I would like to have some experts' ideas about it and someone to help me with these concerns:
    1) is it possible to power 12v LEDs truck light using 9v batteries? if so, how long would it last ?
    2) Is there an alternative way to build this blinking circuit without using 555 timer?
    I appreciate any advices/comments or circuit layouts ...
    Thank you! (Sorry for my bad English)
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,101
    3,036
    You'll need a power transistor to increase the current controlled by the timer circuit.
    1. It's unlikely that 9V will work well for an LED designed for 12V. It may not light at all. Small 9V "transistor" batteries would be run down very quickly if it did work. 2. Perhaps, but the 555 is widely used for exactly this purpose. I'd stick with it.
     
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  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,979
    744
    add a power transistor on the output of the 555 like this
     
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  4. RichardO

    Well-Known Member

    May 4, 2013
    1,234
    384
    A friend made this flashing tail light for my bicycle. :D

    It flashes about 3 times a second for about 3 milliseconds. Even though the light is made to run on 12 volts, it works good enough at 9 volts.

    The life of the 9-volt battery will be shortened because it will not be fully drained when the light is too dim to use. I am guessing that a 9-volt alkaline battery will last over 100 hours. When it is replaced it will still be good enough to use in other circuits.
     
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  5. steven2410

    Thread Starter New Member

    Jul 7, 2014
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    what if 2 9V in series (18v), would it work ? How's about a 9V in series with 2 1.5v?
     
  6. steven2410

    Thread Starter New Member

    Jul 7, 2014
    16
    0
    why is there a feedback wire on VR1 100k? is it just a variable resistor?
     
  7. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    VR1 is potentiometer used as a variable resistor (reostat).

    When using 9 Volts batteries the circuit will not last very long.
    Have a look at the following page:
    http://www.powerstream.com/9V-Alkaline-tests.htm

    As your led is taking 420 mA, take a look at the 500 mA curves.
    If you are using a duty cycle of 50 % ( 50 % of the ime on and 50 % of the tome off),
    The battery will last about twice the time in the curve.

    Bertus
     
  8. RichardO

    Well-Known Member

    May 4, 2013
    1,234
    384
    Two 9-volt batteries in series will exceed the voltage allowed for powering the C-MOS 555 timer. If you want full brightness from the light and long battery life use 8 1.5 volt batteries such as AA or AAA alkaline.
     
  9. RichardO

    Well-Known Member

    May 4, 2013
    1,234
    384
    Thanks for the link, Bertus. I have added to my references file.

    The trick is to pulse the LED's at a very low duty cycle. In my bike tail light, the LED's are only on for about 1% of the time. This would be equivalent to an average current draw of 4.2 mA (even less at 9 volts). This would give much longer life even to a "discharged" voltage of 8.5 volts. The curve for the ACCELERATED SMOKE DETECTOR in the link below shows a life of nearly 5 days. I think this is representative of what to expect for my bike tail light.

    http://data.energizer.com/PDFs/EN22.pdf
     
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