Question about crystal oscillator

Discussion in 'The Projects Forum' started by gaetan8888, Nov 24, 2008.

  1. gaetan8888

    Thread Starter Active Member

    Nov 14, 2008
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  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    Crystal oscillators tend to be single frequency devices, although they can be used at harmonic frequencies. Here is the Wikipedia article about them - http://en.wikipedia.org/wiki/Crystal_oscillator.

    If you are careful about layout and bypassing, the oscillator would be reasonably stable. But it won't tune to a different frequency, although you can always drop in another crystal.
     
  3. gaetan8888

    Thread Starter Active Member

    Nov 14, 2008
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    Hello

    In the web site it say that you can adjust the frequency by changing C1 value, so I would use a triming capacitor and replace it by a fix cap wen I would have the right frequency.

    Thank

    Bye

    Gaetan
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    Read it again!

    Values of capacitor (C1) and xtal (X1) to be varied for required frequency.

    The crystal sets the basic frequency.

    It's possible with careful tuning to get the circuit to oscillate at various overtones of the crystal's fundamental frequency, but these are basically multiples of the fundimental.

    If you want xtal stabilized clocking at various rates, you'll need to start out at a higher frequency and use clock dividers.
     
  5. gaetan8888

    Thread Starter Active Member

    Nov 14, 2008
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    Hello

    Here around I can not find a 11.2896 mhz crystal, and order it by mail would cost me quite to much high price for the minimum shipping cost.

    I only have a 11.275 mhz crystal and a 11.840 mhz crystal.

    So I did think to use an oscillator that I can adjust a bit the frequency.

    Thank

    Bye

    Gaetan
     
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    A crystal oscillator can be "pulled" for a maximum of 700 ppm.
    See the design notes in the PDF.

    Greetings,
    Bertus
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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  8. gaetan8888

    Thread Starter Active Member

    Nov 14, 2008
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    Hello

    I live in forest in mountain, in the north of Quebec in Canada.

    Thank

    Bye

    Gaetan
     
  9. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    And you REALLY have to work at it to get that much "rubber". I used to build VXO's, and by the time you got them working right, it was faster to regrind the crystals!

    eric
     
  10. scubasteve_911

    Senior Member

    Dec 27, 2007
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    Digikey ships to canada for a very fair price and quickly. Unless you're location needs a dog sled team to get to, they might charge a premium!

    Steve
     
  11. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    As eric KL7AJ already told you, the old crystals could be grinded.
    I used to do it with VIM on a glassplate, to get the frequency higher.
    If you wanted a lower frequency you painted the crystal with black lacquer.

    Greetings,
    Bertus
     
  12. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    You could also use McClean's toothpaste instead of Vim. It goes without saying that anything that could grind quartz down probably did wonders for your teeth too!

    Eric
     
  13. gaetan8888

    Thread Starter Active Member

    Nov 14, 2008
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    Hello

    Looking at Crystals Oscillators

    There is various types of Crystals Oscillators with different kind of output, which ones, in those output types can drive four 74HCT74 ?

    Crystals Oscillators output types; TTL - HCMOS - LVPECL - LVDS - LVDS

    Thank

    Gaetan
     
  14. SgtWookie

    Expert

    Jul 17, 2007
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    TTL or HCMOS.
     
  15. gaetan8888

    Thread Starter Active Member

    Nov 14, 2008
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    Hello

    Btw, what is the differences between TTL - HCMOS - LVPECL - LVDS - LVDS
    output ?

    Thank

    Bye

    Gaetan
     
  16. bertus

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  17. flat5

    Active Member

    Nov 13, 2008
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    How far can you bend a ceramic resonator. Is this a useful technique to get more spread that a xtal provides yet still have a good measure of frequency stability?
     
  18. gaetan8888

    Thread Starter Active Member

    Nov 14, 2008
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    Hello

    Fox made the FXO-HC52 serie, a very low jitter ceramic resonator crystal oscillator, at very low price and seem quite interesting.

    But is it true that the ceramic resonator crystal oscillator have less precise timing and do age more rapidely compared to the quartz crystal oscillator ?

    Maby those new models of ceramic resonators crystal oscillator would be much better ?

    Thank

    Bye

    Gaetan
     
    Last edited: Dec 3, 2008
  19. leftyretro

    Active Member

    Nov 25, 2008
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    Quartz crystals will always be superior to ceramic resonators as it a material with a much high Q value.

    Lefty
     
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