Using microcontrollers we can design various electronic projects using few external electronic components . This circuit project is a very simple digital clock project that is based on the PIC16C54A microcontroller , manufactured by Microchip . As you can see in the circuit diagram , this microcontroller based , electronic clock is powered from a three volts DC power supply ( two AA cells ) .
This microcontroller project implements a 24-hour digital clock, alarm and 99 minute 59 second count down timer.
For this digital clock project high efficiency common cathode LED displays were chosen for their 3.5 mA current requirement, eliminating the need for any external transistors for display drive. A low impedance direct drive piezo buzzer was chosen and it’s tone is generated by the software of the PIC16C54A to further reduce system cost.
The PIC16C54A supports the 32.768 kHz “watch” crystal and typically consumes less than 15 mA of current in this configuration.
The display contains four digits with seven segments each; therefore a multiplexing scheme was used to reduce the number of I/O lines needed to drive the displays.
There are 4 common cathode display connections (one for each display digit and connected to
PORTA for convenience so that rotates and moves can be used) and 7 segments (connected to PORTB for convenience so that moves can be used) for a total of 11 I/O lines needed for the display. Common Cathode displays were chosen, since the PIC16C54A can sink 5 mA more current than it can source. The last I/O line (RB7) was used to drive the buzzer. The three keys for setting the time are multiplexed onto the LED display segments to eliminate the need for additional I/O lines.
This clock project based on the PIC16C54 was designed and developed by John Day from Microchip Technology Inc.
You can download the source code for this digital clock by following this link .PIC16C54A clock source code download