Display Technologies Demystified: LED Calculators & LED Watches

In the previous part, we read about the basics of display technologies and their initial applications (early 20th century)
http://guruprasad.net/posts/display-technologies-demystified/

With the advent of semiconductor technology in 1950s (transistors & diodes using silicon & germanium), scientists went on an overdrive to recreate all the existing technologies including displays with the help of semiconductors. This had led to the invention of Light Emitting Diode (LED) by scientists at Texas Instruments in the early 1960s. In its most basic form, LED consists of 2 types of materials sandwiched within a tiny shell with 2 terminals protruding out of it. When voltage is applied to these terminals, the LED glows as a result of movement of electrons which emit light.

led

The real reasons why scientists were fascinated with LED were:
1) Compact size: Due to semiconductor technology, the LEDs could be squeezed into tiny display units with minimal circuit parts.

2) Relatively lower power consumption: In an incandescent display, light glows as a result of a filament “burning” at high temperature and thereby consumes lot of power. Whereas in LED, the glow is due to emission of energy by electrons and hence much lesser power consumption.

7segment_displays

Due to the above 2 reasons (smaller size & lesser power consumption), LEDs took off in early 1960s with innovative experiments & use cases resulting in several new products. One such miniature product was the LED calculator which which was a paradigm shift from mechanical calculator to electronic calculator, saving space & adding to convenience.

mech_led_calc

Further advancement in Integrated Circuit (IC) technologies helped scientists squeeze electronic calculators into compact forms which could be fit into pocket (Pocket calculators)

AdHeathIC2006

 

Another revolutionary product was the LED watch (introduced during the late 1960s) which could  display time in numerical and the usage of quartz & Integrated Circuit (IC) technology drastically improved the accuracy compared to its predecessors.

time_computer

But the major problem with LED watch was the power consumption. Although LEDs consumed much lesser power compared to incandescent, it was still not practical for watches because of battery constrictions. Lighting the LEDs (and hence displaying numerical time) in watch even for a few hours would drain the battery. Companies tried to overcome this problem by displaying light “on demand” (for 5 seconds whenever a button is pressed after which it would disappear again, thereby conserving power).

LED_watch

While the analog watches would last for months, the LED watches, despite their power saving mode, would get drained within weeks (or days if looked up frequently throughout the day). Moreover, those who were used to quick glance at their watches were not impressed with such watches which always required manually pressing a button to look at the time. For example, imagine driving a car and pressing a button on a watch to look at the time. Every time, one had to bring the hand closer and use the other hand to press a button to look at the time which was impractical in the long run.

Some other companies came up with innovative solutions in which one could flick his hand, upon which the watch would display the time for a moment and again turn to power save mode.

pulsar-wrist-flick-ad

When companies were not able to convince customers, they turned aggressive and began to market it as a fashion statement by offering gold plated watches which were no less than jewels.

pulsar_gold

Even James Bond was roped in to promote LED watches in his movies during late 60s & early 70s.

james_bond_pulsar_watch

James Bond prominently displaying Pulsar LED Watch in a movie

Despite all these aggressive marketing strategies, sales of LED watches did not pick up. Not only the companies & marketing agencies, but even scientists were disappointed because while the quartz technology and integrated circuit (IC) of the digital watch was revolutionary and appreciated,  the display (LED) was proving to be a hindrance. But the scientists would not give up so easily. They planned to reuse the quartz & IC technology but with a better display technology.

In the next part, we shall find out how scientists overcame this battery restriction by using LCD technology for display on watches, which is still in use today.

You can subscribe for updates & future posts by entering your email id and confirming it from your mailbox

  • Enter your email id

, ,