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Xtal vs. Resonator

Discussion in 'Electronic Basics' started by randy.day, Nov 24, 2008.

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  1. randy.day

    randy.day Guest

    I noticed some catalog listings for 'resonators', which are portrayed
    schematically as a xtal with two included caps to ground.

    Are they xtals, or something different, and what are the pros/cons (if any)
    over xtals?

    Opinions welcome.
     
  2. Eeyore

    Eeyore Guest

    Optional caps. You can get 'plain ones'.

    NO. They're Ceramic resonators like the name says.

    Ceramic resonators are VASTLY cheaper but do not have the timekeeping tolerance
    of crystals. I like resonators since in medium quantities they knock $1.00+ off
    the retail price of one's goods..

    Graham
     
  3. Randy Day

    Randy Day Guest

    Heh. Got it in one! :)
    Fair enough...
    So they're ok where ppm accuracy isn't an issue?
    Useful to know. Thanks!
     
  4. Joerg

    Joerg Guest


    Actually there is one more important factor: Resonators can be a lot
    more rugged than crystals. I have used them in applications where
    frequent falls onto hard surfaces were to be expected. As Joel wrote if
    something like RS232 is the most timing-critical aspect on your design
    (on many of mine that was the case) you can usually find a resonator
    that is precise enough.
     
  5. Phil Allison

    Phil Allison Guest

    "Joel Koltner"
    "Randy Day"

    ** The "tempco" spec for an average crystal is +/- 50ppm, but be aware that
    this is for the whole operating temperature range, while the accuracy spec
    ( typically +/-20ppm) is given at ONE temperature, usually 25C.

    This causes lotsa confusion for novices, as the operating temp range can be
    70 to 100 degrees C wide.

    If you divide the tempco spec by the number of degrees in the operating
    range - you come up with a number of about +/-1ppm for the drift per
    degree C. In fact, the number may be rather better in the temp range
    around 25 C. Plus of course, it is a simple matter to use a trimmer
    capacitor adjust the frequency of a crystal oscillator to be "spot on" at a
    particular temperature.

    So, using only a standard crystal and with an indoor temp that stays within
    the range of say 20 to 25 C - one can easily have a crystal oscillator
    with an accuracy of a few ppm.

    My 1GHz bench frequency counter suffered from an annoying " warm up" drift
    of about 25ppm ( due to internal heat coming from the AC tranny and a 5 volt
    regulator) until I figured out a simple fix - I just added a 40mm DC fan
    blowing outside air DIRECTLY onto the crystal.

    Warm up drift is now gone.



    ...... Phil
     
  6. Phil Allison

    Phil Allison Guest

    "Joerg"

    ** That is contrary to the experience of folk who repair remote controls for
    TVs & DVDs etc.

    Failure of ceramic resonators inside them after dropping the devices is VERY
    common - particularly the 2 pin kind that operate around 400kHz.



    ..... Phil
     
  7. Phil Allison

    Phil Allison Guest

    "Joerg"...

    ** Shame how consumer grade parts ARE what we are discussing.


    ** Not relevant to the point.




    ...... Phil
     
  8. Eeyore

    Eeyore Guest

    YOU are not relevant to the point !
     
  9. Phil Allison

    Phil Allison Guest

    "Eeysore = Mad Dog Pommy **** "

    ** Drunk even before the sun goes over the yard arm ???

    Not even a sailor either ......

    Just another Rabid Mad Dog pommy ****.




    ..... Phil
     
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