Breadboarding Xtal OSC?

Discussion in 'Embedded Systems and Microcontrollers' started by spinnaker, Mar 7, 2012.

  1. spinnaker

    Thread Starter AAC Fanatic!

    Oct 29, 2009
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    I am going to be breadboarding a 32,768 hz Xtal OSC for timer 1. First off will it work at all? I do understand the the extra capacitance of the breadboard might throw the osc off a bit but I don't care as it will be in a printed circuit after I get everything working.

    The leads for the xtal seem kind of thin and I am not sure if they will make a proper connection when plugging it into breadboard. Maye I can but the xtal and loading capacitor leads into the same holes? Or would I do better to build a daughter board for the xtal and it's caps that would plug into the breadboard using a couple of header pins?
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    Take two short jumper wires or a 2-pin header and solder the XTAL leads to these.
    At 32KHz, the board stray capacitance will have negligible effect.
     
  3. Wendy

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    Mar 24, 2008
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  4. aeroguy

    Member

    Sep 16, 2009
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    FYI, I'm a novice.

    I recently breadboarded with a similar oscillator, and had no problem. I just "plugged" the xtal into the BB holes adjacent the appropriate PIC pins.

    The capacitors to ground were connected a few holes away from the PIC and xtal, but on the same breadboard "bus."

    All worked well. No soldering.
     
  5. panic mode

    Senior Member

    Oct 10, 2011
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    parasitic capacitance of breadboard is GREATLY exaggerated. whenever something doesn't work as planed, it gets attributed to this. ;)

    don't worry, capacitance IS there but it is very small and only affects really high frequency circuits. i've built bunch of circuits in tens of MHz without issue. last one i played with was PIC circuit with 20MHz crystal.
    in comparison, 32kHz is VERY low frequency (32kHz=0.032 MHz).

    ---EDIT--- (fixed typo - thank you atferrari )

    20MHz / 0.032MHz = 625 times

    as you probably know

    Xc= 1/(j*2*pi*f*C)

    so Xc (impedance of capacitor) is proportional to 1/f. issue with parasitic capacitance is that those stray capacitances become low impedance, in fact they are lower as frequency increases.

    let's assume that this capacitance is something like 10pF, then at 32.678kHz impedance would be some 486 kOhm.
    this is large enough to be ignored in just about any case.
     
    Last edited: Mar 30, 2012
  6. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    More exactly = 0.023 :eek: :)
     
  7. KJ6EAD

    Senior Member

    Apr 30, 2011
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    For components with weak, thin or even incorrectly spaced pins I permanently mount them on a milled-pin socket then I have good pins to work with.
     
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