Timer With Audible Warning

*see text R1 045 TIMER WITH AUDIBLE WARNING RESET VI EMI ZIT) id 1 2 P1 * R2 5008 CAI9 220n 9V R3 c2 O Applications of this little circuit include a portable parking meter timer and egg timer. The 14-stage binary ripple counter Type 4060, IC1, has an on- chip oscillator capable of stable operation over a relatively wide frequency range. In the present circuit, the oscillator frequency is determined by an external RC network connected to pins 9,10 and 11. When the circuit is switched on with Sl, the pulse at junction R4-C2 resets the counter and counting starts. When the count reaches bit 14 (Q13), pin 3 goes high so that the self-oscillating piezo-electric buzzer, a 12 V type, is turned on via driver Tl. The time delay is set with the aid of P1. Time delays of between one minute and two hours are possible by appropriate dimensioning of the timing components: 1-30 minutes: Cl = 220 nF; P1 = 500 1d1 1-60 minutes: Cl = 470 nF; P1 = 500 kit 1-120 minutes: Cl = 470 nF; P1 =1 MCI 4060 0...