throbbing led's

Discussion in 'The Projects Forum' started by slimnick, Dec 28, 2007.

  1. slimnick

    Thread Starter Member

    Nov 25, 2007
    21
    0
    i am currently trying to make a project that replicates a firework that disperses when it explodes. the idea behind the throbing led's is the brightest peak would be like the explosion and it brightness will fade.

    is there anyway that this task can be accomplished with the use of a 555 timer and a 4017 decade counter?
    I am limited on IC which i can get so i was hopin that these two chip's with some other components could do it.

    if this can be done, some little adivice would be greatly aprreciated thank you
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    A 4017 can't put out the power necessary to make an LED very bright.

    However, it could be used to trigger a Darlington pair or (preferably) an N-channel MOSFET to provide a ground to an LED that has a ready current source.

    (bear with me here, I'm brainstorming ;))

    Supply current to a super-bright LED via a capacitor that was charged up beforehand through a resistor. Additionally, drain the capacitor using a parallel source of resistance, because as the voltage across an LED becomes lower, their current drops off drastically, leaving the LED on for a ridiculously long amount of time. If you don't have the resistor in parallel with the cap, the LED will emit light for a very long time.

    Hope this helps...
     
  3. slimnick

    Thread Starter Member

    Nov 25, 2007
    21
    0
    i have an image attached of a ciruict that i have built at the moment. it seems to be simulating a little explosion. i am attaching this so that someone can look over it and tell me if there is anything wrong that can damage the circuit or anything i can imporve on.. thankyou in advance:D
     
  4. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
    If you can't get enough with the IC output you can always use a transistor. It's easy. If you want to run alot of LEDs you can use a darlington driver IC.

    You'll have to learn how much you can push the LED you choose. Some of them will take 50ma for a very short time. No need to charge a capacitor just set the current limiting resistor correctly and make *sure* the pulse width is no more than 75 percent of max on time. Some LEDs have this information some do not so expect to smoke a few.

    Look up darlington array IC for a simple higher current driver.

    'luck

    I have some green LEDs that when hooked directly to +5v are impressive. Lasts a second then they die. Poor LEDs. ;)
     
  5. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
    Oh, just dismembered. The capacitor idea will work with something simple. Steel wool. One single strand held between two posts with some way to hold it. Dump a very large amount of current into it.

    Now make a dozen and figure out how to set them off in a row without frying your controller.
    ;)
     
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