Скачать или смотреть Digital clock with CMOS timebase and a TTL logic

Testing of the circuits for a planned Nixie clock - indicators are temporarily made from 7447 decoders and LED 7-segment displays.

Timebase (clock impulse generator) contains a 4060 circuit, which contains an oscillator and a 14bit frequency divider. LED indicates a 2Hz output pulses, then they are divided by 2 in first 2-divider in a counter for ten of hours (it may not be used for this, because this counter counts only "0", "1" and "2", so only 5-divider is sufficient).
Oscillator is controlled by 32.768kHz piezo crystal.

The counters are made with 74390 ICs (double BCD counters), resetting of the seconds counters and blocking the timebase are made from a simple diode logic. Button on the right side resets both second counters, resets counter in a 4060 and stops the oscillator. This function is useful for the accurate synchronization of the clock with a precise time normal (f. e. clock with a DCF-77 receiver).
Reset circuits for a ten of the seconds, ten of the minutes and reset of the hours counter at a "24" status, are also made simply by diodes and resistors.

The middle button takes a signal from "Q5" (pin 4) output of the 4060 to a clock input of the first counter for a setting a minutes and a left button takes a frequency direct from oscillator (pin 9), through a "separator" with KC507 transistor (without it an interferention between a Q3 output (pin 3) and a Ctc output (pin 9) results in a stopping the oscillator) to a counter - for setting a hours. There's also a separating resistors between outputs and a buttons, to avoid interference between outputs, when buttons are pressed.