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Electronic Wrist-Watches
February 1973 Popular Electronics

February 1973 Popular Electronics

February 1973 Popular Electronics Cover - RF CafeTable of Contents

Wax nostalgic about and learn from the history of early electronics. See articles from Popular Electronics, published October 1954 - April 1985. All copyrights are hereby acknowledged.

Try as I did, I could not find any instance of the Ness Clocks all-digital liquid crystal display (LCD) desk top which appeared in this 1973 Popular Electronics article. There must not have been many produced. LCDs had only been commercially available for a year or so when this went on sale. Of the relatively few digital display clocks and watches available in the 1970s, the vast majority used light-emitting diodes (LEDs), and most sold for north of $100 (~$600 in today's money). Portable devices with digital displays really began to flourish with the advent of both CMOS circuitry and LCD displays; i.e., low current devices that extended battery life. Wrist watches, which could only accommodate very small batteries with limited energy storage capacity, were amongst the greatest beneficiary of the technology. It was a big deal as evidenced by this article and many others like it in the era.

Electronic Wrist-Watches

Electronic Wrist-Watches, February 1973 Popular Electronics - RF CafeTiny Quartz Crystals and IC's Are Revolutionizing the World of Timekeeping

Electronics is currently creating a major revolution in the staid old world of timekeeping. Wristwatches designed to gain or lose no more than a minute a year are already beginning to take a prominent place in the market. Some are selling for less than $125, and the price is realistically expected to drop even lower in the near future. The new electronic timepieces require little or no cleaning or adjustment. Nor is it necessary for the wearer to wind his watch daily; the electronic watches operate a year or more on a single miniature battery.

The new generation of electronic time-pieces is the offspring of a logical mating of the quartz crystal with newly developed solid-state devices - emphasis in the latter area being on COS/MOS (complementary-symmetry/metal oxide semiconductor) integrated circuits. Steering away from traditional mainsprings, gears, and cogs, the new timepieces keep time via a tiny bar of quartz crystal and an integrated circuit which provide an accuracy heretofore unattainable in even the most expensive mechanical movement in consumer watches.

Simplified block diagram of typical electronic watch - RF Cafe

Fig. 1 - Simplified block diagram of typical electronic watch with conventional hands. Circuit can be used to drive stepping motor, synchronous motor, or balance wheel. In any case, the motor or wheel drives the hands as found on the typical watch face.

Ness Clocks, Ltd., of Palo Alto, California - RF Cafe

All-Electronic Desk Clock

Ness Clocks, Ltd., of Palo Alto, California, is producing an all-electronic desk clock built around digital IC technology and liquid crystal readouts. The new $150 timepiece derives its time from a special LSI timing chip. The output of this chip drives a newly developed liquid-crystal readout system. The liquid crystal display is guaranteed for two years. Should it fail, the display can be unplugged from the clock and replaced with a working system in about the time it would take to change a light bulb. The readout is in minutes and hours, with an AM/PM indicator which pulses once each second. Clock accuracy is said to be within several seconds per month.

The quartz crystal is the key to the precision timing in the electronic watch. But new developments in solid-state technology are what must be credited with bringing the electronic watch onto the consumer market according to Harry Weisberg of RCA's Solid State Division, pioneer of the new COS/MOS technology in IC's.

Mr. Weisberg explained: "The principle of using quartz as a time base is not new. It has long been employed in laboratories, by the U.S. Naval Observatory, and in other applications requiring precision timing. However, the introduction of quartz into consumer watches had to await a technology such as COS/MOS which could reduce the cost, size, and power requirements of the electronics associated with the quartz approach."

Indeed, COS/MOS technology has blossomed, and with it, the electronic wrist-watch. More than a dozen U.S., Swiss, and Japanese firms are either developing or marketing electronic timepieces. Among them are the most prominent names in the industry; Hamilton, General Time, Patek Philippe, Omega, Timex, Longines, Bulova, and Seiko, to name just a few. Most of these employ COS/MOS-type circuits supplied by such top names in the field as RCA, and Motorola.

Operating Principles

All of the current batch of electronic wristwatches operate in basically the same manner. When power is applied to the quartz crystal, the crystal's piezoelectric property generates a high-frequency signal, commonly in the 30,000-to-50,000-Hz range. (The smaller the crystal, the higher the frequency.) The high-frequency signal is then divided by an integrated circuit to yield a 1-Hz (1 pulse/sec) output signal which is used to drive either conventional mechanical hands or is decoded to drive seven-segment readouts.

The excellent stability of the quartz crystal - an attribute that has also made the crystal the frequency controlling device for broadcasting radio signals for decades - and its ability to produce the high-frequency signal account for the accuracy of the electronic watch. In effect, the quartz crystal splits a second into 30,000 to 50,000 parts as compared to the 360 parts produced by the tuning fork used in the most accurate conventional watches.

The greater the number of parts into which a second is split, the greater the obtainable accuracy. However, the electronic watch's frequency is determined by a cost/power tradeoff. A smaller high-frequency crystal is less expensive than a larger crystal of lower frequency, but it requires more power.

The greater accuracy of the quartz crystal approach also results from the elimination of the traditional mechanical parts whose precision is determined by the care exercised in their manufacture but deteriorate in normal use through wear. The substitution of solid-state parts for mechanical devices also means fewer malfunctions. And when repair is required, the problem in an electronic watch can quickly be isolated to one of a few components. It is not difficult to foresee the day when component repair of electronic watches will be done away with altogether. Breakdowns will be so infrequent, and the working portion of the watch so inexpensive, that when a malfunction does occur, the entire timing unit will be discarded and replaced with a new one.

All-electronic Pulsar (Hamilton, HMW Industries) - RF Cafe

All-electronic Pulsar (Hamilton, HMW Industries) displays time digitally with light emitting diodes which are activated when wearer presses button.

The COS/MOS circuit is an ideal teammate for the quartz crystal in an electronic watch. The large-scale integrated circuit COS/MOS chip can contain 1500 or more elements in a space the size of a match head and, therefore, fits in with the size requirements of the wristwatch. It also generates practically no heat and is highly immune to electrical noise. But perhaps the principal attribute of the COS/MOS IC for timing applications is its incredibly low power requirement, measured in microwatts (millionths of a watt), which is a tremendous advantage in situations where a small battery must last a long time.

Analog & Digital Watches

The quartz crystal and IC keep the time. The manner in which the time is displayed falls under two basic categories: analog which retains the traditional moving hands, and all-electronic which displays electronically generated numbers.

In the analog watch, some mechanical features of conventional watches must be retained to control and operate the moving hands. One version employs a stepper motor (Fig. 1), another a tuning fork, and still another the traditional balance wheel. These mechanical devices are driven by the output from the quartz crystal/IC system to achieve electronic accuracy.

The major advantage of the analog electronic watch is its low cost. Hence, the lowest cost electronic watches, expected to be priced at about $50 within a year or two, will almost certainly use a moving-hands display. (An alternative analog movement employs mechanical wheels that display the time in a digital manner.) Whether it uses hands or the digital wheel, the analog watch still has moving parts that are subject to wear and require periodic cleaning, oiling, and adjustment.

In contrast, the all-electronic watch contains no moving parts to wear out. The output of the IC triggers a display that flashes the time in discrete numerals (Fig. 2) . Too, encapsulation of the electronic components eliminates the need for cleaning and oiling.

Interior of Pulsar Wristwatch - RF Cafe

Interior of Pulsar Wristwatch

Gray bar at top is quartz crystal, black square is IC, LED readout at center.

The readout display for all-electronic watches is a principal area in which technology is still undergoing development. One approach is to use light-emitting diodes (LED's). But LED's are basically power hungry devices. Using them in a wristwatch with a continuous-duty display cycle is impractical when the only powering source is a small battery. In one LED-display watch on the market, for example, the wearer must push a button to activate the display for a few seconds, after which the display extinguishes. The LED's otherwise would drain the battery in short order.

Liquid crystals are the prime candidate for providing practical continuous-duty readout systems in electronic watches. They require very little driving power, and when teamed with micropower COS/MOS logic, can yield operating lives of a year or more from a single battery. Another advantage of LC's is that they are activated by ambient light. The brighter the light, the more visible and clearer the display. But by the same token, LC readouts cannot be read in darkness since there is no activating ambient light.

Regardless of the outcome of developments now under way to improve readouts, costs for all-electronic watches are already beginning to come down. As the watches gain in popularity and technical advances are made, major price reductions are envisioned.

They require one BCD (binary coded digital) seven-segment decoder for each display numeral.

Although the most dramatic and visible impact of electronic timekeeping has been in wristwatches, the technology is also being put to work in other areas. Desk and wall clocks are also employing the electronic approach. So are industrial timing systems and marine chronometers.

Block diagram of multiplexed system for producing digital display of time - RF Cafe

Fig. 2 - Block diagram of multiplexed system for producing digital display of time. Non-multiplexed systems can also be used.

Motorola package has quartz crystal - RF Cafe

Motorola package has quartz crystal, integrated circuit, and stepping motor.

Patek Philippe, the noted Swiss watch and clock manufacturer, is employing COS/MOS circuits in a timing system whose clocks can automatically switch over to small batteries in the event of a primary power source failure. This assures continued operation and eliminates the need for resetting numerous clocks in a large facility. The system is designed for factories, schools, hospitals, and other facilities where uninterrupted precision time keeping is a must.

Innovative applications such as this, combined with mass marketing of the electronic watch, are giving electronic timekeeping an increasingly important everyday role. It appears certain that by 1980 the electronic watch will dominate that part of the market consisting of watches in the over-$50 price range. In attaining this status, the electronic watch will enable solid-state technology to participate in a total worldwide market in which all types of watches are expected to sell at the rate of 300-million units annually by 1980.

How far the electronic watch sales penetrate into other segments of the market will depend to a large degree on how much the prices of electronic components call be reduced. Today, four-fifths of all watches sold in the U.S. are priced at $40 or less. Should component prices drop low enough to allow an all-electronic watch to appear on the market for $40 or less, there will be a corresponding increase in the electronic watch's segment of the overall market.

Electronic timekeeping is here now, but it is only recently on the scene. There is still much research and development to be undertaken before a "universal" electronic system is devised. Even so, the electronic watch has already established one fact of central importance to the consumer: The age of near-perfect timekeeping has arrived. Perhaps, if all goes well (and there is no indication that it will not), there is an electronic wristwatch in your future.



Posted February 19, 2020

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