Digital Clock

Analog clocks are not as popular as the whole world seems to be switching to digital options. There's no doubt that various types of timing devices have undergone changes over the last few years and with the rise of mobile devices, which are to totally digital, there are fewer analog clocks. They both tell time, hopefully accurately, but what makes these two types of time pieces different? What makes a digital clock work?

                               

Components Associated with all types of Clocks

No matter what type of clock is being considered, they all have some components in common. N matter what types of technology or electrical components are used in clock they will all share these features or qualities that make them a clock or a time keeping piece :

• Power Supply or Source 
• A time-base or counter that keeps time and is the heart of the clock, or its heartbeat 
• Components which break down the time base into components : Seconds, minutes and hours.
• Some way of displaying the time (analog clocks use a face and hands digital uses a lighted display) 

Digital clocks are not a lot different than analog clocks except that they handle the basic time keeping functions using all electronic components instead of mechanically. For instance, digital clocks use an electronic power supply, either AC power from an outlet in the wall or from a battery. It also has a time base that is electronic and "ticks" at an accurate rate. And a digital clock has an either Light Emitting Diodes (LED) or a Liquid Crystal Display (LCD) to Display the lighted time.

How the Digital Clock Works :

                          

An oscillator is needed for any type of clock to work. In a digital clock, this is usually provided by using a crystal which is made out of glass. As an electric charge passes through the crystal, it will change shape slightly and make a very light sound. The  sound which is heard at a regular frequency is then converted into an electronic signal. By using a series of counters, the oscillations from a 60 Hertz oscillator is reduced to a 1 Hertz oscillation.

This sets up 1 Hertz signal so that it can pass seconds because the actual definition od 1 Hertz is one oscillation for each second. The sex counter sets up the hours, since it counts for 6 sets of 10- or 60.

Clock Works 

This LED or LCD light display is called a "7-segment display." This is because there are seven segments that can light up to display a number. For instance, the number 8 uses all 7 lights. These lights are situated on the display so that they display two sets of two digit numbers. when the digital clock reaches 12:59 and goes to 1:00 it essentially resets or starts over.

The electric components in a digital clock are designed so that they have a built-in processor which basically looks for a "13" in the hours display. When it occurs, it resets the counter back to 1. Users can also reset the time using digital buttons that are installed on the clock in some accessible location. These buttons allow increased frequencies so that the number more much faster.

Building your Own Digital Clock 

The first thing we need is a power supply. We built one in the electronic gates article. That time, we used a standard wall transformer that produced DC (direct current) power and then regulated it to 5 volts using a 7805. For our clock, we want to do things sightly differently because we are going to extract our 0-Hz time base from the power line. Therefore, we need the following parts for our power supply :

• 12-volt AC transformer
• Bridge rectifier
• 7805-5-volt regulator
• Two 470-microfarad electrolytic capacitors
• 5.1-volt zener diode
• 1-K-ohm resistor 

A Few notes on the parts used :

• The difference between the AC transformer we are using here and the DC transformer we used in the article on gates is that the AC transformer preserves the 60-Hz sine wave found in 120-volt household current. If you want to use your volt-ohm meter to measure the voltage of an AC transformer, be sure you use an AC voltage range rather than a DC range.
• We use the bridge rectifier to convert the AC to DC. One of the terminals on the rectifier will be marked with a "+"-- from that you can find the minus and AC inputs. There is no polarity to an AC transformer lead you connect to which AC lead of the rectifier.
• The 7805 and capacitors are wired just like they were in the electronic gates article.
• The resistor and the zener diode extract a 60-Hz signal from the transformer's sine wave. A diode is a one-way valve for electrons. a zener diode is also a one-way value, but it also passes electrons in the other direction. If they are above a certain voltage. The zener diode therefore turns a 10-volt sine wave into a clipped wave oscillating between 0 and 5 volts. This is perfect for clocking the TTL counters. The diode will have a band painted on one end--this band should be the end connected to the resistor.

Advantage of Digital Clock :-

The main advantage of the digital clock system is the indication of an absolutely exact time (with an error of run-1 rs for 300000 years). The accuracy of signal timing is provided by cesium master clock at the paris Bureau of Weights and Measures.

Digital clock system provides :

• coordinated indications of all clocks at the site with a global universal time (UTC/GMT) ;
• Synchronous indication of an exact zone time in the pointer and digital formats on all clocks;
• Automatic conversion of clocks during the transition to winter/summer time;
• Automatic setting of te clock to the exact time after restoration of power or liquidation of the accident on a line;
• Synchronization of the computer network in accordance with the calendar date and exact time;
• Simplicity of usage that does not require special training of the engineering personnel. 

   Writer: Mr. Krishan Kumar Saini 

Today we have learnt Basics about Digital Clock. Hope this lesson is helpful for you.