555 Timer Configuration?


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  1. #1
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    Jan 2007
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    Question 555 Timer Configuration?

    Hi. i am trying to configure a 555 timer to output a 20khz cycle with a 1% duty. I am having trouble because I cant get it to output a lower than 50 % duty cycle with that frequency!
    Can you help me calculate the values of r1, r2, and c1?
    Thanks a lot.
    Manuel

  2. #2
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    When you aks Google to show you some application notes of the NE555 then you will get something to see how it's done.
    By using a diode (or 2) you will get the whole range from 1% till 99%.

  3. #3
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    Steve

    It's not a bug, it's a random feature.
    There's no problem, only learning opportunities.

  4. #4
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    Simple,

    Dump the 555.

    Get a 12F683.

    Then use ...
    Code:
    HPWM  1,2,20000
    No external parts. No difficult calculations.

    If desired, add a serial port to set the output with your computer, save the values in EEPROM, then disconnect the computer.

    Can't do that with a 555.
    <br>
    DT

  5. #5
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    Quote Originally Posted by manumenzella View Post
    Hi. i am trying to configure a 555 timer to output a 20khz cycle with a 1% duty. I am having trouble because I cant get it to output a lower than 50 % duty cycle with that frequency!
    Can you help me calculate the values of r1, r2, and c1?
    Thanks a lot.
    Manuel
    google 555 timer calc and you'll get lots of calculators that will do it for you.

  6. #6
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    yes, as long as they match the extra Diode(s) circuit.

    PIC10F???
    Steve

    It's not a bug, it's a random feature.
    There's no problem, only learning opportunities.

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