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 NXP Semiconductors

  • Digital Clock Using PCA21125

  • Created: Feb 18, 2015

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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.