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who knows about noises?

Discussion in 'Electronic Basics' started by E.persia, Oct 11, 2008.

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  1. E.persia

    E.persia Guest

    hi every body
    I have a signal generator thak works with 555
    sometimes I see a a noise like digital FM that I think it from 50hz
    220 (network voltage)
    what i can do to remove it I dont know even when it comes
    may be its the malfunction of breadboard
    but this my problem the output square wave wavelenght decrease and
    increase priodically!
    what i can i do for such a thing?
     
  2. Eeyore

    Eeyore Guest

    Try explaining the question properly.

    Graham
     
  3. Bob Masta said a better power supply, which is a good guess.

    There is also the "voltage reference" pin on the 555, which is pin 5.
    Varying the voltage there will shift the frequency of the 555 oscillator,
    and if it's audio frequency injected there the oscillator will be
    frequency modulated. Putting a bypass capacitor on pin 5 will fix
    that.

    Of course, in order for that to be the problem, there has to
    be some strong AC nearby. While many 555 circuits will show that
    pin bypassed, I've never bypassed it 35 years of using the IC, and
    I've never had a problem.

    Michael
     
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