Long-time-timer

  
When used as a stand-alone device, ZN1034E from Ferranti can provide timed intervals ranging from 1 second to 19 days, although the rc time constant is only 220 seconds. The ZN1034E includes an internal voltage regulator, an oscillator, and a 12-stage binary counter. The total delay time provided by the counter is 4095 times the oscillator period. The control logic times-out after 4095 cyCles of the oscillator, and delivers high and low output pulses at pins 2 and 3.
Long-time-timer - schematic

The output at pin 3 is normally high and decreases at the end of the timed interval. The complementary output at pin 2 is normally low and becomes high at tbe end of the timed interval. The timing period is initiated by momentarily grounding pin 1. Timing resistor R 7 consists of two resistors, R1 and R2, in series. Because R1 has a fixed value of 100 KO, the total range of R7 is 100 K to 1.1 MO.




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