This project introduces the use of PCA21125 as

one of the components of this digital clock. It is a real time clock

made in CMOS technology and calendar optimized for low-power consumption

with an operating temperature up to 125 degree Celsius. Data is

transferred via a Serial Peripheral Interface (SPI-bus) with a maximum

data rate of 6 Mbit/s. The device displays the current time and date

with the use of an LCD.







ATMEGA8 microcontroller was

chosen for its high prevalence and low price. This microcontroller can

be used as a DIP- housing 28 and a housing SMD execution TQFP- 32.

Resistor R3 is needed to prevent random noise at terminal PC6. The LCD

display is connected to the microcontroller for four-bit system. The

variable resistor R2 is required to adjust the contrast of displayed

symbols. Rotating this resistor obtains the most precise indications on

the screen. The LCD backlight is organized through the conclusion of "A"

and "K" on the display board. The backlight is turned through the

current limiting resistor - R1. The higher the value, the dimmer the

display will light. The LED may be replaced by any audio circuitry,

which responds to a signal from the microcontroller. Managing the clock

setting is carried out by means of the buttons S1 - S4.







Digital

clocks had remarkably benefitted us for its accurate and readable time

display. This can be observed in a wide range of applications such as in

appliances, computers, automotive technology and industrial equipment

where time is considerably observed.