I want to build a 555

Discussion in 'General Electronics Chat' started by babafellow, Mar 28, 2008.

  1. babafellow

    Thread Starter New Member

    Mar 28, 2008
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    i need to construct a 555 timer which includes sounds sir
     
  2. babafellow

    Thread Starter New Member

    Mar 28, 2008
    4
    0
    u just send only input and output wave what of d texts?
     
  3. babafellow

    Thread Starter New Member

    Mar 28, 2008
    4
    0
    but i need a 555 timer which includes sounds
     
  4. babafellow

    Thread Starter New Member

    Mar 28, 2008
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    i need to construct an astable multivibrator
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    I've moved these posts into their own thread.

    For clarification, do you wish to build a 555 equivalent from discreet components for educational purposes?
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Have you got an LM555 datasheet? I believe it has block diagrams of the internal circuitry.

    What portion must make sound?

    And, by the way, an astable multivibrator includes, but is not limited to, an LM555. A clear statement of your project would be nice to have. If it is simply an audio frequency oscillator, then reengineering an LM555 is more effort than is necessary for the result. Three resistors, two capacitors, a lamp and an op amp will do the trick.
     
  7. Thomas.R

    Member

    Aug 16, 2007
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    i made one using this page. look for the one shot-operation

    Thomas
     
  8. Thomas.R

    Member

    Aug 16, 2007
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  9. Wendy

    Moderator

    Mar 24, 2008
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  10. Audioguru

    New Member

    Dec 20, 2007
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    Hi Bill,
    An 8 ohm speaker has a peak current that is too high for your poor little 555.
    Connect a current-limiting resistor to limit the current to "only!" 200mA.

    Your LEDs won't light when they are connected upside down.
     
  11. Wendy

    Moderator

    Mar 24, 2008
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    Picky Picky, actually I've built the former circuit many orbits ago, the 555 didn't get hot or anything, just wasn't very loud. I'll change the latter schematic to correct the LEDs, and I'll breadboard the former to verify (but I'll change the schematic anyhow for now).

    An old fashioned 1K to 8 ohm audio transformer would pick the volume back in any case.

    My Dad's favorite phrase about this time was "Turn it off". He liked his TV and we lived in the deep country, where anything could interfere. Thanks for pointing out my boner.

    I've noticed .gif files look a LOT better for these applications.
     
  12. Audioguru

    New Member

    Dec 20, 2007
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    With a 9V battery, the output of a 555 is about 7.5V p-p into a 1k transformer winding. Then the power is only 14mW. Like a little earphone.

    The output at 200mA is 4V p-p. Then an 8 ohm speaker in series with a 12 ohm resistor will have a power of 320mW, 23 times more than with the 1k transformer.

    A little LM386 power amplifier produces a square-wave of 1.1W when it drives an 8 ohm speaker with a 9V supply.
     
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