building a 555 hysteretic osillator

Discussion in 'Feedback and Suggestions' started by hillshaveeyes57, Sep 12, 2012.

  1. hillshaveeyes57

    Thread Starter New Member

    Sep 12, 2012
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    trying to build my first 555 hy. oscillator. used these instructions online: http://www.allaboutcircuits.com/vol_6/chpt_8/3.html but there were some errors i think. i see where one capacitor goes, but not the second. also the pentometer and one of the resistors seem to be mislabeled, so i really don't know where one of the resistors go.

    does anyone know of a better diagram or something? i'm on breadboard, no soldering if that helps.

    Thanks.
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    The potentiometer should be 10K and not 10ohms as stated in the list of components, they have swapped R3 and R4.
    As for the other "C1" probably connects to pin 8 and pin 1.

    http://www.aldinc.com/pdf/time_15002.0.pdf
     
    Last edited: Sep 12, 2012
  3. Wendy

    Moderator

    Mar 24, 2008
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    You got me, the part list does not jive with the two schematics nor the picture. The three illustrations are consistent with each other, it is the parts list that is off, R3 and R4 are swapped on it.

    I made the article many years ago. I'll enter it into the corrections log. I am also moving this into the Feedback and Suggestions forum.

    As for the other C1, reading is your friend. This is explained in the paragraph, it is an alternate part to vary the frequency.

     
    Last edited: Sep 12, 2012
  4. Wendy

    Moderator

    Mar 24, 2008
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    R3 and R4 has been changed.

    Thank you for pointing it out.
     
    Last edited: Sep 12, 2012
  5. hillshaveeyes57

    Thread Starter New Member

    Sep 12, 2012
    16
    0
    i'm still having some trouble with it. i've built it a few times and what i'm getting now is both LEDs light up and stay that way and don't react to the pentometer in the circuit. it's like the pentometer isn't even there which makes me think either something is fried or the wiring doesn't work. i've tried turning the pentometer but the LEDs don't react. they just stay lit up, no oscillation.

    i'm def. a novice at this and really just want to get the thing oscillating. i understand a little from high school physics and know that electricity flows like water in the circuit. i do want to read more into this but really just want to get it working right now.

    is there another way i can wire it or is there another diagram i could use? is it possible i got some dud parts? i'll replace the oscillator and the 555 in the meantime.

    thanks for the help!
     
  6. Wendy

    Moderator

    Mar 24, 2008
    20,765
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    The schematic and layout works, it was verified. Please start another thread about this problem, as this forum is for feedback and corrections only.

    You either have a wiring error or a bad 555 (could it be a CMOS 555 like a TLC555?). Post pictures of the breadboard on the new thread.
     
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