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    555 timer astable multivibrator

    In the following astable multivibrator circuit,



    in some books, it is mentioned that the duty cycle id

    d=( R1+R2)/(R1+2*R2)

    in some other books, it is mentioned

    d= R2/(R1+2*R2)

    which is correct? which one should i use if i want to design a circuit of particular duty cycle ?

    please tell me whether duty cycle is Ton/(Ton+Toff) or Toff/(Ton+Toff)

    •   Alt5th May 2011, 18:03

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    Re: 555 timer astable multivibrator

    duty cycle is Ton/(Ton+Toff)


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    •   Alt5th May 2011, 18:14

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    Re: 555 timer astable multivibrator

    i can't understand still sir.. please explain me ..



    •   Alt5th May 2011, 18:30

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    Re: 555 timer astable multivibrator

    This page has the equations and a calculator

    555 Calculator

    Also check 555 and 556 Timer Circuits

    Alex


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    Re: 555 timer astable multivibrator

    which is correct? which one should i use if i want to design a circuit of particular duty cycle ?
    please tell me whether duty cycle is Ton/(Ton+Toff) or Toff/(Ton+Toff)
    I think, it's your choice. That's also the reason, why both expressions for d exist.

    In my opinion, you would define high output as "on" and duty cycle as Ton/(Ton+Toff).
    In this case, the first expression applies: d=( R1+R2)/(R1+2*R2)


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    •   Alt5th May 2011, 18:54

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    Re: 555 timer astable multivibrator

    Quote Originally Posted by electroboy View Post
    please tell me whether duty cycle is Ton/(Ton+Toff) or Toff/(Ton+Toff)
    Normally when we say that the duty cycle is 10% we mean then the output is on for 10% of the period time so I think you should use Ton/(Ton+Toff)

    Alex


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    Re: 555 timer astable multivibrator

    Ton/Ton+Toff


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    Re: 555 timer astable multivibrator

    duty cycle is ton/(ton+toff)

    http://teeblog.blog.com/archives/66/#as Read this for calculations and basic theory



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    Re: 555 timer astable multivibrator

    you can also try this link for understanding 555 ic as a-stable multivibrator



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