What am I not seeing / Help troubleshooting

Discussion in 'The Projects Forum' started by nerdegutta, Aug 8, 2010.

  1. nerdegutta

    Thread Starter Moderator

    Dec 15, 2009
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    Hi,

    Think I'm going blind.

    Goal: make a 555-based buzzer, with piezo/8 Ohm speaker.

    Schematics, see attachment, I'm trying to build the one on the right hand side.

    When I assemble the parts on a breadboard, it sounds perfect, even with a 8Ohm speaker.

    But: When I draw the schematic i KiCad, and make a PCB, it's only coming some strange "hizzzzz" noise. Not what I would expect.

    I've nearly spent all Sunday, on this little simple task. :(

    What is the different between my schematic and the one on the right hand side?

    I'm open for any ideas and suggestions.
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    Care to show us both sides of the PCB board in a common graphic format?
     
  3. mik3

    Senior Member

    Feb 4, 2008
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    Have you checked if the PCB is fine (tracks, shorts etc)?
     
  4. nerdegutta

    Thread Starter Moderator

    Dec 15, 2009
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    785
    Here are some pictures, component side and copper side.

    I guess I've stared too much at them...

    I appreciate tips on placing components for more efficiency.
     
  5. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,869
    1,393
    In your schematic, C2 is connected to the wrong side of R3. C2 should be connected directly to pins 6 and 2 of the 555. You have it connected directly to pin 7.
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    Yep, that is what I'm seeing.
     
  7. nerdegutta

    Thread Starter Moderator

    Dec 15, 2009
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    You are absolutely right. When I 'quick' soldered the capacitor to the copper side, it's working.

    Thanks a lot!
     
  8. Wendy

    Moderator

    Mar 24, 2008
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    I hate that when it happens, but it happens to the best of us.
     
  9. nerdegutta

    Thread Starter Moderator

    Dec 15, 2009
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    It's good too hear that I'm not the only one, staring and staring at a simple circuit. Without seeing the solution.

    Thanks again for the help.
     
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