Simple LED blinking

Discussion in 'General Electronics Chat' started by bevi, Apr 23, 2009.

  1. bevi

    Thread Starter Member

    Apr 23, 2009
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    How to create a simple LED blinking TTL circuit with 555 chip? Just 1 led, resistor and and 555.
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    Simply make a low frequency astable ocillator with the 555 and have its output feed an LED with a current-limiting resistor in series with the LED.

    The supply needs a bypass capacitor and the oscillator needs one or two resistors and a capacitor.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    This is about as simple as it gets with a 555 timer:

    [​IMG]

    This will flash at a roughly 1Hz rate.
     
  4. Wendy

    Moderator

    Mar 24, 2008
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  5. bevi

    Thread Starter Member

    Apr 23, 2009
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    Thanks for advices. But I have just 0,01uF/100V capacitor. Can I use it in TTL circuit with 5,5V?
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    No, the LED would flash much too fast for you to be able to see it.

    The circuit I posted will flash at just under 1Hz with the values shown. If you tried to use your 0.01uF capacitor, it would flash at 100Hz, and you would not be able to see the flashing; it would just look dim. R1 can't be increased very much, because the current flow would be too low.

    You need a larger capacitor.
     
  7. bevi

    Thread Starter Member

    Apr 23, 2009
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    Thanks, I understand now.
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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    Good. :)

    Note that in the schematic, the pins on the 555 are reversed; as if you were looking at them from the bottom, with the notch on the end of the IC towards the top of the schematic.
     
  9. bevi

    Thread Starter Member

    Apr 23, 2009
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    I have had some doubts, if 100V capacitor will works on TLL with 5,5V. Now I know It will. I hope It's impossible to get a 100V electrick kick, if I messed up something?
     
  10. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
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    100V is just the rating of the capacitor. It can take up to 100V without being damaged. I won't have any where near 100V in this circuit.
     
  11. qwerty156

    New Member

    Jan 3, 2010
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    the schematic should connect pin 1 to GND
     
  12. redlight000

    Member

    Feb 26, 2010
    66
    2
    Hi Bevi,
    the above answers are right, but here's a little more info,
    rig up the Timer in astable mode. R1 in pins = 4k7 RES
    R2 =10k in pins 6+7, thats the Res bit, for C it depends on what flash rate you may want eg with the above put a 100uf electrolitic capacitor in pins 1&2 the negitive goes to pin one..ok? now I Personally find a 68 ohms ok for a decent brightnes.. the goes from pin 3 of the chip to a hole in the breadboard. then you positive of the LED goes in there to the 68 ohm resistor.. and take a wire from the negitive lead and insert that to 0volts..

    With the above C electro capacitor the LED will exactly flash 1 flash per second. now if you want to speed it up, you only have to change the capacitor buy a factor of ten, so if you use a 10uf elec -+ ones that will flash at approx 5/6hz per second..
    I think going a bit deeper a 47uf is 3hz.. ok and so on...
    and it works to I've timed them all. HTH

    redlight:)
     
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