Automatic power generating system watches

"Automatic power generating system" refers to a function that automatically converts the arm movements of the wearer of the watch to electrical energy and stores it to power the watch itself. Watches equipped with this function are called automatic power generating system watches.

Automatic (self-winding) mechanical watches had been the mainstream of watches until quartz watches arrived on the market. Therefore, the idea of automatic power generating system, which utilizes oscillating weight to generate the power required to run the quartz watch, has long existed since the very beginning of quartz watch development.
However, the idea was not feasible at that time, since the electricity generated by such a mechanism was far too small to operate early quartz watches and the energy storage device for generated electricity was undeveloped. 
The subsequent developments of power saving technologies and energy storage technologies allowed for practical applications. 
An automatic power generating system watch works on basically the same principle of "electromagnetic induction" just like a bicycle lamp. This principle has been successfully applied to run quartz watches: to utilize the movements of the oscillating weight to rotate the built-in permanent magnet near the coil, where the electrical current is produced and transferred to the energy storage unit such as a rechargeable battery to power the watch.

The mechanism of automatic power generating system watches is explained below.

  1. The movement of the wearer's wrist rotates the half-moon shaped "oscillating weight."
  2. The gear train amplifies the rotational movement of the oscillating weight 100 fold and transfers it to the generating rotor.
  3. The generating rotor spins at extremely high speeds to generate power voltage across the coil block where the electric current flows.
  4. The produced electric current is stored in the energy storage unit.
  5. The energy storage unit supplies the electrical energy to the quartz crystal oscillator to run the quartz watch.

Quartz movement (Automatic power generating system watches)

(Note): The above information applies to the members of
the Japan Clock & Watch Association and their products.