555 Timer example

Discussion in 'Homework Help' started by King7, May 14, 2016.

  1. King7

    Thread Starter Member

    May 14, 2016
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    Hey guys how are you?
    i'm kind of new at this so can anyone please solve this homework for me
    and because that R1 is unknown it is the only homework requirement
    thanks in advanced :)
     
  2. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    What is the actual question? Are you given the target frequency? If not, are you asked to solve R1 as a function of the frequency or the other way around?
    Have you attempted the problem?

    John
     
  3. King7

    Thread Starter Member

    May 14, 2016
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    ahhh sorry
    the frequency is 50
     
  4. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    ahh sorry
    Are you interested in getting help to solve the problem?

    John
     
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  5. King7

    Thread Starter Member

    May 14, 2016
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    yup brother
     
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The frequency is 50 what? Hz,kHz?

    Bertus
     
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  7. King7

    Thread Starter Member

    May 14, 2016
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    Hi bertus
    it's 50 Hz
     
  8. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Some hints. No one here is supposed to solve it for you.
    1) Calculate Tl + Th in seconds (or milliseconds)
    2) Then calculate Th with the information given
    3) Then calculate R1 from its equation and the known values

    John
     
  9. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Your picture has clear formulas:

    king7_555_oscillator.jpg

    Use the directions of John to calculate the cycle time and the high and low times.
    Then you can calculate R1.

    Bertus
     
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  10. King7

    Thread Starter Member

    May 14, 2016
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    which capacity i shall use
    c1 or c2 ?
    or both
     
  11. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Just C1.
     
  12. King7

    Thread Starter Member

    May 14, 2016
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    why not c2 it's less
     
  13. King7

    Thread Starter Member

    May 14, 2016
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    Hey bertus man
    which capacity i shall use
    c1 or c2 ?
    or both
     
  14. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    C1 is the timing capacitor,
    C2 is for decoupling.

    Bertus
     
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  15. King7

    Thread Starter Member

    May 14, 2016
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    so it's C1 then just like alec said
    thanks bro
     
  16. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    What is the total period time, when the given frequency is 50Hz?

    Bertus
     
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  17. King7

    Thread Starter Member

    May 14, 2016
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    i got the result (0.160 s) so it will be (160 ms)
     
  18. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    That is not correct.

    Please show your work.

    John
     
  19. King7

    Thread Starter Member

    May 14, 2016
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    This is my calculation
     
  20. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    That also is not correct.
    1) Where are your units?
    2) Given a frequency of 50 Hz, what is the period? That is all the information your need to calculate it.

    Just look at the units. What are the units of frequency? What are the units of period?

    John
     
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