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    555 and rectified ac Proteus

    Hello,

    I am trying to simulate a square wave with 555.
    It works ok if i power the circuit with DC, but when i try to power from a rectified ac voltage source, 50hz, it does not work anymore.
    I tried with Sine wave AC voltage source, also with Alternator, with or without transformer, with generic bridge rectifier or with 4 diodes, nothing works.

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  2. #2
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    Re: 555 and rectified ac Proteus

    look at the voltage on pin 8 carefully ...



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    Re: 555 and rectified ac Proteus

    The 555 simulation model seems to behave different than the real chip.



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    Re: 555 and rectified ac Proteus

    Have you tried to connect an earth to the primary side of the transformer?



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    Re: 555 and rectified ac Proteus

    other than 50 Hz, what are the characteristics of the source?
    what is the turns ration of the transformer?
    what voltage do you expect on the output side?

    how much current does the 555 circuit draw?

    on the surface, it looks like the capacitor should hold up the
    rectified AC, but the scope trace looks like it isn't holding up the DC

    as Easy peasy says, look at pin 8 of the 555 carefully
    please show the time scale of the 'scope

    what is the reference for the 'scope traces?



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  6. #6
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    Re: 555 and rectified ac Proteus

    Thanks for your answers,
    I found that adding a diode after the filter capacitor to separate the circuit from it fix the problem. It is like the filter capacitor maybe influences the R2, R1, C1 series ?!.
    I dont think a real circuit will have this problem, something may be wrong with proteus..


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