Editing 555 timer for 60% interval change

Discussion in 'The Projects Forum' started by J7NF, Apr 4, 2016.

  1. J7NF

    Thread Starter New Member

    Mar 12, 2016
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    I need to edit my 555 timer in astable mode to get at least an interval change of 60% for the duty cycle, for example varying from 40 to 100% and so on. I am using a 10k potentiometer and 1 K resistor as R1 and R2 so I cannot go below 52 %. Any idea
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Lets have a circuit diagram first , then we can see what you need. You can do it with an hysterical circuit using diodes.
     
  3. dannyf

    Well-Known Member

    Sep 13, 2015
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    Have you tried to half R7 so that it's time constants with C3//Cr is less than R1?
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    :p:):confused:
     
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  5. crutschow

    Expert

    Mar 14, 2008
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    Below is a 555 astable design whose duty-cycle variation is close to 0-100% with pot position.
    (Shown for pot positions of 1% and 99%.)
    Edit: Either the OUT pin or DIS pin (with pullup) can be used as the output.
    The frequency is approximately 1/(0.73*Rpot*C2)

    upload_2016-4-4_16-17-25.png
     
    Last edited: Apr 4, 2016
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  6. Wendy

    Moderator

    Mar 24, 2008
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  7. engrBecks

    New Member

    Mar 31, 2016
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