Outside interference on IC's

Discussion in 'The Projects Forum' started by fiskle, Feb 18, 2013.

  1. fiskle

    Thread Starter New Member

    Feb 18, 2013
    2
    0
    Hi all,

    I have made a simple 3.3 volt circuit where an output from an IC drives an input on a flip flop. The circuit has been put onto a prototype board. Everything works great, however if I touch the wire connecting the two IC's, the flip flop triggers. I don't actually even have to touch the wire, I just have to bring my finger close to it. What would be the best solution to fix this problem? I'm assuming because of inductance my finger is triggering the IC.

    Thanks
     
  2. sheldons

    Active Member

    Oct 26, 2011
    616
    101
    post your schematic.......
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,123
    3,047
    Keep your fingers away! :p Try shielding, such as placing the PCB into a metal box, such as the favorite, an Altoids tin.
     
  4. MrChips

    Moderator

    Oct 2, 2009
    12,441
    3,361
    Then you are doing something wrong.
    Show your work.
     
  5. fiskle

    Thread Starter New Member

    Feb 18, 2013
    2
    0
    here's the sample schematic. Nothing fancy. When the wire between the two IC's has a finger that is in proximity the IC fires. Otherwise, it works perfect on my breadboard. That's the only wire that causes the problem. If I put my scope on it the problem stops. I would like to understand and learn what is causing this phenomenon as well as what a solution would be.

    Many thanks
     
  6. MrChips

    Moderator

    Oct 2, 2009
    12,441
    3,361
    You did not say what is IC2.
    How do you know IC2 is programmed correctly?
    Connect a 100kΩ resistor from the CLK to GND.
     
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