Mechanism of Clock

Discussion in 'General Electronics Chat' started by extremeads1, May 27, 2007.

  1. extremeads1

    Thread Starter Active Member

    Feb 10, 2007
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    now i understand why the oscillations produced by the crystal need to be converted into a square wave,is it beacuse it uses a digital circuitary i.e 15 stage divide by 2 n/w . this means that we are making use of electronic circiut inside a watch so cant we produce the same resonant frequency of a crystal (32768 HZ) using a CMOS TIMER IC within a watch.
    my question is then for what purpose is the crystal used ?
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    The crystal produces very very stable oscillations, so the watch may keep very accurate time. ;)
     
  3. extremeads1

    Thread Starter Active Member

    Feb 10, 2007
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    sir but for the same purpose Can't CMOS 7555IC be used for generating 32768 hz which is cheap and also accurate moreover a 3vlithium cell can power the Cmos easily,isnt 't?
    one more question which is the Cmos IC used for a 15stage /2 counter circuit
     
  4. Gadget

    Distinguished Member

    Jan 10, 2006
    613
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    The 7555 / 555 is not the reference, it can be configured as an oscillator but uses an external resistor and capacitor for its time constant. R/C constants are quite inaccurate and also prone to frequency drift. The purpose of a watch is to keep reasonable time, therefore a crystal or some other accurate and stable timebase is still required.
    The 4044 is a single 12 stage counter/divider, the 4020 is a single 14 stage, the 4060 is a single 14 stage with built in oscillator.
     
  5. extremeads1

    Thread Starter Active Member

    Feb 10, 2007
    64
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    thank you very much sir
     
  6. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
    Go ahead and try the 555 as your square wave generator without the crystal. You might even build in both into the circuit and have jumpers or a switch to allow you to switch between them. This would be a good demonstration for other builders as to why you'd want to use a crystal.
     
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