Digital Clocks and Watches – past and present
The digital clock was first invented in 1956 using a collaboration of methods and techniques that had been developed through other technological advances. The main difference a digital clock has over previous pendulum clocks, which were traditionally used before this time, is that it uses electronic methods of time keeping. This means that all the functions which aid the clock in telling the time are powered electronically rather than mechanically.
The digital clock was traditionally powered by an electronic power supply or quartz movement, the time base or "heartbeat" of the clock is electronic, the gearing mechanisms which extract the different components of time, e.g. hours, minutes and seconds, are electronic, and finally there is also an electronic display. This uses LCDs or LEDs to show the time in four digits, either using the 12 or 24-hour methods. With the 12-hour display clocks, the time mechanism within the clock had to be set so that when the display fell on 12:59:59 the next time shown was not 13:00:00 but 01:00:00.
What are digital clocks and watches used for?
When digital clocks were first invented they were used simply for telling the time. However, over the years their functions have widened and they now incorporate a number of different uses. The most common and popular of these is the digital alarm clock. These clocks can be set so that they will sound an alarm or, as radios have now been added as another function of the digital clock, turn on the radio at the required hour. Digital clocks and watches are now also commonly used as stop clocks as they can be used to record distances of time. This means that in particular referees and judges in sports and athletics now use them. As satellite waves are now being used to help set the time of digital clocks, they are being used for computer clocks so that an accurate time can be always be found to help aid their running and other machines which may run off them.
Problems and improvements to digital clocks and watches
- The main problem that occurred with the initial design of digital clocks was that when there was a power failure or a battery change the clock, when power was resumed, would reset itself to 12:00:00 instead of returning to the correct time. Alarm clocks which started to employ the digital display found that this fault was especially problematic for these types of clocks. If there was a power cut in the night, the clock would reset itself to 12:00:00 thus making the function of the alarm clock redundant. To solve this, later designs incorporated a battery backup so that if there was a cut in power from the mains supply, the battery would maintain the power, thus an electrical charge would be available at all times.
- However, more recently designs have been produced which contain a method of automatically setting the time from another mains source rather than the clock resetting itself. These methods include using broadcast radio time signals from an atomic clock, using satellite television waves to tell the time, or from a computer connection.
- Another problem that occurred with setting the time of the clock was that when a power supply was fed into it, the time would start automatically at 12:00:00 and the time would have to be set by the user. This meant that when daylight saving occurs the clock would need to be reset manually to the new time. However, later developments to digital clocks have meant that they have been fitted with a device which automatically sets the time using the methods mentioned above. The digital clocks and watches would be sourced by a mains supply from Greenwich Mean Time which would automatically update itself when necessary, and signals would be sent to the digital clocks and watches reporting the new correct time. When the clocks changed twice each year clocks fitted with these tracking methods will automatically update themselves. These systems are being fitted to computers, burglar alarms and handheld computer systems so that the correct time can always be found which aids the running of such machines and helps their users.
- Another method used to power the clock, so that there would be no break in the electrical connection, is to power the clock by using an internal rechargeable battery. This method is only suitable for digital watches as movement which comes naturally from the arm and wrist produces a quartz movement within the watch. A crystal is placed within an electronic circuit and when movement causes the crystal to vibrate, an electric signal is produced which powers the watch electronically. The clock is set at the factory to the correct time and, in theory, the quartz movement then maintains the clock working so the time will always be accurate.
- However, this method does not always work as it has been found that when some people remove their watches for sleeping the battery can slow down thus causing the time to do so. Improvements have been made so that the rechargeable battery lasts longer and movement during the day will be sufficient to power the digital watch into the night. The problem with setting the clock to the right time after daylight saving occurs is also still a problem with this method, so using this source of power combined with a satellite connection to set the time would be the most efficient system.
Today this is the system which most digital watches employ. The majority of digital clocks produced today have a means of setting the time from an external source using a satellite connection. This solves all problems with loss of power supply and changes to time during daylight saving.