Simple pulse generator with accurate frequency 1Hz
This circuit is ideal for clocks and anything that has
to do with time measurement. The output pulse comes every one
second with great accuracy (without being affected by
environmental interferences or time). Its accuracy is based
on a quartz crystal oscillator, which guaranties that your clock
will not desynchronize.
The piezoelectric crystal is the most critical component and may hard
to find. You must use only the one I suggest. In any other case, the
output won't have the exact frequency of 1Hz. If you want different
frequencies we can get the pulse signal from the other output of 4521
- One CMOS 4521 Chip.
- A 1MŮ resistor (1/4 Watt).
- One 3.9KŮ resistor (1/4 Watt).
- One 22pF capacitor.
- One 82pF capacitor.
- One piezoelectric crystal 4,194,304Hz. Crystal's frequency is
critical. If you use a different crystal, you will not have the
exactly 1Hz output frequency.
- A 16 pin DIP socket (for the 4521 CMOS chip).
- A small piece of a Veroboard
- Wire for connections
- Solder and soldering iron
Also you will need a stabilized 5 Volt external power supply.
You can use a 4.5 Volt battery or even a 9 Volt battery. Be aware
that with the 9Volt battery the output level will be also at 9
Volt (not TTL logic).