- on Microcontrollers
- Published in issue 12/2002 on page 0
Seconds Reference with Quartz Crystal
Simple analogue quartz watches or watch movements, which can be obtained inexpensively by mail order or at flea markets, contain a circuit that drives the watch motor with pulses at the rate of one per second. If you build such a watch movement into a small circuit, you have an inexpensive but nevertheless accurate 1-second frequency standard.
The RC time defined for IC2 needs to be increased by a factor of 10. This requires changing P1 to 1 MOhm and R7 to 330 kOhm.