alarm timer - for home and garden

for home and garden A periodic alarm signal has many ap- plications in daily day life: "lights off" indicator in cars, water level in- dicator, alarm clock, memory aid, limit indicator, and calling signal are but a few. The circuit begins to operate as soon as its input level becomes "0"; after about 30 seconds the buzzer sounds four times at one-second intervals. This happens every thirty seconds until the input goes logic high again. The circuit is based on a 14-stage CMOS binary counter and oscillator type 4060. The oscillator frequency, f, is determined by f = 1/2.2R3C1, where f is in Hz, R3 in ohms, and C1 in farad. The oscillator is internally connected to the clock input of the counter. As soon as the reset input (pin 12) is logic low, the counter begins to operate. Because at the onset out- puts Q4, Q7, and Q10 are logic "0", pin 12 goes low when the input to N1 is "0". After about 30 seconds, Q10 becomes "1". The 1 Hz signal on Q4 is then applied to the base of transistor...