The main feature of this real time clock circuit is that it only draws less than 100mA, so it can be run with rechargeable batteries. By increasing the value of resistors connected to the seven segment display you can decrease the current gain. 24(international time clock) to 12 hour time clock conversion can be done simply by burning the PIC microchip with the corresponding hex file.
Download Hex file of real time embedded C
Circuit diagram of Pacific Time clock
Click on the circuit for enlarged view
- PIC 16F84A
- Transistor BC548 (4-Nos)
- Resistor (180R-9Nos,10K,1K-4Nos)
- Push button (3-Nos)
- Crystal 4MHz
- Common cathode seven segment display (4-Nos)
How to make a digital clock?
- We use four common cathode seven segment displays which are connected in PORTB of the PIC.
- The seven inputs of seven segment displays are connected in parallel but it shows different values it is done by continues scanning, that is if a value want display on the first seven segment display activate the corresponding transistor then send the value to through the port that is shown below.
- To display a value on the second display activate the second transistor and send value through PORTB.
- This scanning is continually done by PORTA and PORTB sends the display value.
- Three push buttons are used one for reset the microcontroller and remaining two for set minute and hour which connected in PORTB which scan to get a zero volt on the pins RB6and RB7.
- An LED connected on the RB0 which blink for on second
Components pin out
7 segment display