February 1958 Radio-Electronics
Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Electronics,
published 1930-1988. All copyrights hereby acknowledged.
The world's first electric wristwatch went on sale on January 3, 1957 - the Ventura model, by Hamilton Electric, and it retailed for $200. I use the event as the theme of the RF Cafe logo for that day in history. Unlike today's electric watches which use a crystal for timing, the early watches used a pulsed motor to energize the balance wheel coil, in place of a mainspring and an escapement mechanism. The watch shown in this article from the February 1958 edition of radio-electronics is a model 500, which you can find more detail about on the Unique Watch Guide website.
The electronic technician may soon be seeing a new item on his workbench, the electric wrist watch. He may need a powerful magnifying glass or two and a couple of jewelers' tools, but an electric watch is driven by a tiny electric motor using batteries of a highly specialized type and requires service know-how more closely allied to that of a radio technician than the jeweler.
The Hamilton Watch Co., after 10 years of research and testing, has placed an electric wristwatch on the market. Driven by a miniature reaction motor, it has an accuracy of 99.995% and is powered by a button battery with a life of more than 12 months.
A miniature triangular coil is attached to the balance wheel which is used as the motor's rotor. Platinum-alloy permanent magnets, claimed to have the highest energy content of any magnet in the world today, create the motor's magnetic field.
Coil contact is made through a silver-gold-alloy contact on a nonmagnetic spring fastened to a mounting plate (see figure). As the wheel oscillates its contact brushes against the spring contact, sending a pulse of current through the coil. Timing is based on the natural oscillation period of the balance wheel.
Electric Wristwatch Mechanism
Posted January 15, 2014