Long-interval timer

C1 100p 15V This low-cost timer circuit can offer switching intervals up to about 24 hours and may, therefore, be useful for a variety of domestic as well as electronic applications. Depression of Si causes Re, to be energized and the timer to be started; the position of Pi determines the duration of the timing interval - the given value for C 2 allows a maxi- mum of 12 hours. Doubling the capacitance of C 2 lengthens the timing interval accordingly; the timer may thus be employed to control a NiCd battery charger. Depressing Si at any time during the interval causes the timer to be reset and Re, to be deactivated. The funtion of FF, is that of a counter output Q 3 rather than Q 1 3 to debouncer circuit for Si which, when long interval timer 0 10.12V 85 100k R4 P1 8 8 IC1 IC2 Si1 1N4148 Ref BC547B flpi EMI T1 R6 6J S R2 0 3S2 15 CK FF1 CK FF2 1C2 0sKR 2 11 14 12R K SR 0 4 12 FF1,FF2=1C1= 4027 1C2 = 4060 Ref =12V actuated, causes FF, to apply a logic high pulse to the clock input o...