Digital DCF77 clock with LCD and gong using PIC16F628A

Always the right time and date with DCF77

This project make use of a PIC16F628(A) and a DCF77 receiver from Conrad (Orderno. 64 11 38)

Optional there is a possibility to connect an electronic gong on it.
Click for information about DCF77 on the link underneath:

The working from the DCF77 time signal

Connect the output from the DCF77 module with PORTB.0 (pin 6).
The pull-up resistor on the DCF77 output isn’t necessary because PORTB.0 internal pull-up is enabled.

Digital DCF77 clock

Every second is on PORTA.1 (pin 18) a pulse from 0.5 second.
This signal isn’t necessary for anything, but maybe you want to connect a LED on it, so that these wil blink every second, or a piezo buzzer, so that the clock ticks as an analog clock.

PORTA.0 (pin 17) is the daylight-saving time (DST) pin and is high when it is summer.
For the LCD’s 2×20 and 2×24 is it possible to print a W or S on the LCD in winter/summertime.

When connect PORTA.6 (pin 15) to +5V, the clock stays in 24 hours notation and if is choosen for 12 hours notation (AM/PM) then connect this pin with GND.

Use a HD44780 (or compatible) device for the LC-Display.
Download the .HEX file which belongs to the used LCD size.

When switching the power on, the PIC waits till it get a signal from the DCF77 module (receiver).

When searching does take more than 45 seconds, the message “No signal” follows.
The PIC stays searching until it have a decent timesignal reception.

When there is a signal found, it search to the begin from a new minute, this will take maximum 1 minute.
The timebar gives the left time.
If the whole timebar is full, then there is no startsecond found and the message “No signal” appears.

When the startsecond is found, the bits are gonna filled with time and date.
This takes exactly one minute.
If the whole timebar is full, the actual time and date is complete.

From now the day, time and date can be read.

If PORTA.6 (pin 15) is connected to GND the clock stays in 12 hours (AM/PM) notation.
The W stays for Wintertime (S for Summertime, DST).
There is a .HEX file with W / S and a .HEX file without this indication.

When the reception becomes worse or disappears, then also follows the message “No signal”.
The PIC still keeps trying to find the actual time back when the reception is good (again).

The basis
If only the time and date must be read from LCD without any fuss then build the circuit from scheme 1.
Adjust the contrast from the LCD with P1.


For more detail: Digital DCF77 clock with LCD and gong using PIC16F628A

Current Project / Post can also be found using:

  • DIY Connecting PIC18F2550 to Serial LCD Displays
  • gong clock schematic
  • pic 18f452 c rogram lcd
  • Real time clock in pic18f452 projects using mp lab

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