Mosquito Noise Maker

Discussion in 'The Projects Forum' started by Razor Concepts, Dec 10, 2008.

  1. Razor Concepts

    Thread Starter Active Member

    Oct 7, 2008
    212
    1
    Hi, I want to build this:
    http://www.instructables.com/id/The-Raven-high-pitched-torture/

    Here is the schematic:
    [​IMG]

    The 4194304hz crystal, located on pins 2 and 3, is also connected to two 18pf capacitors. I looked up the details on the crystal and found that it had a load capacitance of 18pf. Is that why he chose to use the two 18pf capacitors?

    I want to use a 49152941hz crystal, but in the specs all it says for load capacitance is "series".
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Why don't you just try building it as presented?

    18-30pF is pretty typical for xtals.
     
  3. Razor Concepts

    Thread Starter Active Member

    Oct 7, 2008
    212
    1
    I suppose I'll give it a shot. I have four 7pf caps, ill make two sets of two in parallel to make two 14pf caps and try that out.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Radio Shack sells an assortment of ceramic caps for around $2. It used to be that you'd get a wide variety of caps, from 1pF to 1nF. Nowadays, most of them are 1pF to 10pF.

    If you picked up one of those assortments, you'd practically have a lifetime supply of 10pF caps, which would match up pretty well with your 7pF caps. The numbers printed on the caps nowadays are pretty accurate.

    I think one of the RS 10pF caps with one of your 7pF caps would be a better match than two pairs of 7pF caps. The latter may be too much stress on the xtal.
     
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