Consumer Electronics

DIGITAL CLOCK

An interesting and common use of counters is for frequency division. An example of a simple system using a frequency divider is shown in Fig. 47.1. This system is the basis for an electric clock. The 60 Hz input frequency formed into a square wave is divided by 60, and output will be one pulse per second (1 Hz). This is a seconds timer.

 

 

Fig. 47.1 Practical divide-by-60 circuit used as a 1-second timer

 

Various counters are the heart of a digital clock system. Figure 47.2 (a) is a simple block diagram of a digital clock system. Many clocks use 60 Hz as their input or frequency standard. This frequency is divided into seconds, ...