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Bypass capacitor

  1. Jan 15, 2014 #1
    Hi,

    I would like to know how to insert a bypass capacitor in parallel with the power supply.
    I drew some GREEN lines as jumpers and BLUE line as bypass capacitor for you guys to check if that's the correct way to do it.
    NOTE: Ignore the jumpers, just look at the lines I drew with MS paint.
     

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    Last edited: Jan 15, 2014
  2. jcsd
  3. Jan 15, 2014 #2

    CWatters

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    Your capacitor appear to be connected between 5V and 5V. Should be connected between 5V and 0V as close to the 5V pin on the IC as possible.

    On this type of breadboard (I believe) you have 5V (red) and 0V (blue) rails. Unless the circuit is particularly sensitive you can just plug the cap into the rails, no jumpers required.

    PS: On some breadboards not all the rails are connected to 5V and 0V. Sometimes they aren't connected at the ends (the idea being to allow you to create a 12V rail or similar). Just check any you use are connected on your breadboard.
     

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    Last edited: Jan 15, 2014
  4. Jan 15, 2014 #3
    I thought that to connect the capacitor in parallel with the power supply (5V, the red rail) I should connect it like that. The IC85 has its power supply on its 16th pin and the IC393 has its power supply on its 14th.
     
  5. Jan 15, 2014 #4
    Oh, so I need two capacitors? Can I just use one capacitor and connect the capacitor to the two IC's with jumpers instead? By 0V you mean ground, right?
     
  6. Jan 15, 2014 #5

    CWatters

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    Yes. Good practice is one per IC. I have added them to your circuit drawing...
     

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  7. Jan 15, 2014 #6
    I have to use 0.1μF capacitor and I am only provided one, but not two.
    Why do we need to ground the capacitor, too?
    Let me re-draw it with only one capacitor and the grounding.
     
  8. Jan 15, 2014 #7

    CWatters

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    Just to clarify...

    One per IC
    Located close to the 5V pin on the IC
    Connected between 5V and 0V/Ground

    Note that 0V isn't always Ground but in your case they are the same node.
     
  9. Jan 15, 2014 #8

    CWatters

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    If you only have one capacitor put it on the most sensitive device.

    Edit: Since there isn't much to choose between them I would put it on the 5V and 0V rail between the two devices and connect jumpers from that rail to both devices.
     
  10. Jan 15, 2014 #9
    Is this ok?
     

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  11. Jan 15, 2014 #10

    CWatters

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    Yes that's what I'd do if I only had one cap. You have the cap connected to the 5V pins on both ICs by nice short wires. I would also connect the 0V pins on the ICs directly to the 0V rail that the new capacitor is plugged into by short wires.

    All this may not make much difference to the operation of the circuit but it's good practice.
     
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