Mechanism Quartz clock

basic quartz wristwatch movement. bottom right quartz crystal oscillator, left button cell watch battery. top right oscillator counter, top left coil of stepper motor powers watch hands.



picture of quartz crystal resonator, used timekeeping component in quartz watches , clocks, case removed. formed in shape of tuning fork. such quartz clock crystals vibrate @ frequency of 32,768 hz.

in modern quartz clocks, quartz crystal resonator or oscillator in shape of small tuning fork, laser-trimmed or precision lapped vibrate @ 32,768 hz. frequency equal 2 cycles per second. power of 2 chosen simple chain of digital divide-by-2 stages can derive 1 hz signal needed drive watch s second hand. in clocks, resonator in small can or flat package, 4 mm long. reason 32,768 hz resonator has become common due compromise between large physical size of low frequency crystals watches , large current drain of high frequency crystals, reduces life of watch battery. during 1970s, introduction of metal–oxide–semiconductor (mos) integrated circuits allowed 12-month battery life single coin cell when driving either mechanical lavet type stepping motor or liquid crystal display (in lcd digital watch). light-emitting diode (led) displays watches have become rare due comparatively high battery consumption.

the basic formula calculating fundamental frequency (f) of vibration of cantilever function of dimensions (quadratic cross-section) is:

f
=



1.875

2



2
π





a

l

2







e

12
ρ






{\displaystyle f={\frac {1.875^{2}}{2\pi }}{\frac {a}{l^{2}}}{\sqrt {\frac {e}{12\rho }}}}

where

1.875 smallest positive solution of cos(x)cosh(x) = -1
l length of cantilever
a thickness along direction of motion
e young s modulus
and ρ density

a cantilever made of quartz (e = 10 n·m = 100 gpa , ρ = 2634 kg·m ) length of 3 mm , thickness of 0.3 mm has fundamental frequency of around 33 khz.

the crystal tuned 2 = 32,768 hz or runs @ higher frequency inhibition compensation (see below).