Oscillator - divider 50 Hz

This is a square wave generator, made by me in three versions with the same schematic design. The output is a digital signal between 0 and +5 V and 50 Hz frequency. I designed the first prototype in 1987 as part of a digital frequency meter. In 1990, I made the second prototype as a divider for an existing digital desk clock. The third version was for a radar simulator.

This device uses a quartz oscillator and a series of dividers by ten. By using additional power transistors with heat sink at output, the output current capability of the generator is increased. The primary use of the generator in production was in a radar simulator and the second one in production was for converting a watch with time based on 230V / 50Hz mains power frequency in one with much better precision. According to electric grid regulations in Romania, the frequency of electric network must be maintained within a tolerance of ± 0,05%. In reality the tolerance is ±1,5%, and the the harmonics level is disastrous. That is unacceptable for a time base used in a digial clock.

Figure 1
Output signal
Figure 2
Radar simulator

Specification:
- square wave output
- output frequency: 50 Hz
- output frequency accuracy: ± 0.00001 Hz
- output voltage range: 0 - 5 V
- maximum output current: 200mA
- power supply: 5 V DC

Figure 4
Schematic (PDF)
Figure 5
PCB Layout

The oscillator is made with a CMOS inverter gate ( 1/6 CD 4069) and a 5MHz quartz crystal. The divider from 5MHz to 50Hz is made with five decade counters (CD 4029).

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Links:
[1] - CD4029 datasheet
[2] - CD4069 datasheet