Spring-driven electronic speed control watches

While the unwinding mainspring drives the watch hands, it powers a crystal oscillator through the generator inside the watch to control smooth movement of the hands. 

The spring-driven electronic speed control watch has the same mechanism as a mechanical watch, except for its control system. The watch was invented in the 1970s when quartz watches had been developed and commercialized, in order to make higher precision mechanical watches. When the watch was first developed, the oscillation circuit inside the watch required more energy than the energy produced by the unwinding mainspring, and the energy imbalance was even greater than the automatic power generating system watch. After reducing the power used in the oscillation circuit and improving the efficiency of the generator, the spring-driven electronic speed control watch has been commercialized. 

The mechanism of the watch is as follows: 

  1. Torque developed by the unwinding mainspring rotates the train wheels (gear wheels).
  2. At the end of the train wheels, a rotor, which is used to generate electrical energy, is mounted. A rotating rotor changes the magnetic flux in the coil and electrical energy is generated due to the principle of electromagnetic induction.
  3. The generated electricity drives the IC and crystal oscillator, and the crystal oscillator makes a highly accurate time reference. 
  4. Based on the highly accurate time reference, the rotor's rotating speed is detected and controlled by adjusting the application of the brake.
  5. When the rotor starts rotating at a constant speed, both the train wheels connected to the rotor and the watch hands mounted to the wheels start to move.
  6. As described above, the spring-driven electronic speed control watch, which requires no battery, operates with quartz accuracy through the power of a wind-up mainspring.

Spring-driven electronic speed control watches

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