Improvement method of LED digital clock frequency source

Most LED digital clocks use the mains power f 220V/50Hz as the frequency source for timing. The timing error is about 20 seconds per day and needs to be adjusted frequently, which is very troublesome.

In order to find a suitable crystal, I had to dismantle three abandoned BB machines of different models at home and found two 76,8kHz crystals. After calculation, this crystal uses CD4060 oscillator and 14-level counter to divide by 9 levels. It outputs 150Hz at its (13) pin. This 150Hz signal is divided by 3 by CD4017 counting distributor. It can get an accurate 50Hz frequency source, that is, CD4017 starts counting from 0, and its (4) pin outputs a high level every 3 pulses. The circuit is shown in the figure. Using 4017 frequency division, more crystals with different frequencies can be used as the frequency source of the clock. In addition, the CD4060 oscillator capacitor cx can be used to adjust the time with 8P or 10P ceramic capacitors. These two LED digital clocks are assembled with TMS3450NI and TIMS3459ML timing chips respectively. After the frequency source is improved, the daily timing error is less than 0.5 seconds. Then use 2 old mobile phone batteries connected in series to charge as a DC power supply, so that the LED digital clock has accurate timing, intuitive time reading, and can be used to check time at night. Its timing function can control household appliances, the alarm can be used as an alarm clock, and it is a multifunctional household appliance that is not afraid of power outages.