Economical crystal timebase - a 50 Hz 'bench mark'

7-38 — elektor july/august 1982 This time base circuit is built using normal readily available CMOS ICs and a cheap crystal. The operation of this circuit is practically identical to that described in the "Crystal stroboscope" article in the April 1981 issue of Elektor. The difference between the two projects is that whereas the first one only produced an output of 50 Hz this new circuit gives the constructor the possibility of 50 Hz, 100 Hz or 200 Hz. The 50 Hz reference frequency is an ideal time base for the construction or calibration of electronic clocks, frequency meters and so on. Because of the flexible supply voltage require- ment, it is also a good basis from which to build a digital clock for the car. IC1 contains an oscillator and a 214 divider. Providing the oscillator Parts list Resistors: R1 = 10M R2=100t a 50 Hz "bench mark" rrpTali! 4 6 ‘PD RI OM H Ri S1GND 02 82 12 4 6 7 • 0 economical crystal time base IC1 4060 GND 11 clock 251 131 31 IC2 4013 TP 204800 Hz...