How a Quartz Clock Works

Precision timekeeping using crystal vibrations.

The Piezoelectric Effect

The core of a quartz clock is a tiny crystal of silicon dioxide (quartz). This material has a unique property called piezoelectricity.

Pressure to Electricity: If you squeeze a quartz crystal, it generates a small electric voltage.
Electricity to Movement: Conversely, if you apply electricity to it, the crystal changes shape slightly.

By creating a feedback loop, we can make the crystal vibrate (resonate) continuously, like a tuning fork that never stops ringing.

Piezoelectricity Simulator

Apply voltage to the crystal lattice below to see how the atoms realign, causing the physical structure to expand or contract.

The Oscillator (The Heartbeat)

In a watch, the crystal is cut into a tiny tuning fork shape. When the battery stimulates it, it vibrates at a very specific frequency: 32,768 times per second (Hz).

Why this specific number?

It is high enough to be outside human hearing.
It is a power of 2 ($2^{15}$), which makes it easy for digital circuits to count.

The Tuning Fork Oscillator

Below is a visualization of the quartz tuning fork. In reality, it moves microscopically, but we have exaggerated the motion here.

The Divider (Counting to One)

A motor cannot spin 32,768 times a second. We need to slow this signal down to exactly 1 pulse per second (1 Hz).

We use a circuit called a Flip-Flop chain. Each flip-flop divides the frequency in half.

32,768 Hz → 16,384 Hz
16,384 Hz → 8,192 Hz
...and so on, 15 times...
2 Hz → 1 Hz

Frequency Division Visualization

This interactive component demonstrates how a high-speed signal is halved at each stage. Drag the slider to travel down the circuit chain.

The Lavet Motor (Making it Tick)

Once the signal is reduced to 1 pulse per second, it is sent to a specialized stepper motor called a Lavet type motor.

The Coil: The 1-second electrical pulse flows into a coil, creating a magnetic field.
The Stator: The metal body focuses this magnetic field.
The Rotor: A tiny cog with a permanent magnet sits inside. When the magnetic field flips, the rotor is repelled and turns 180 degrees.
The Gear Train: The rotor turns a series of gears that move the second, minute, and hour hands.

Interactive Stepper Motor

Click the button to send a 1 Hz pulse. Watch how the polarity flips (N/S) and forces the rotor to snap to the next position.