Beeps 7.5 seconds after a preset time, Adjustable time settings: 15s. 30s. 1min. & others This circuit is intended for alerting purposes after a certain time is elapsed. It is suitable for table games requiring a fixed time to answer a question, or to move a piece etc. In this view it is a modern substitute for the old sandglass. Useful also for time control when children are brushing teeth (at least two minutes!), or in the kitchen, and so on. Circuit diagram: Timed Beeper Circuit Diagram Parts: R1 = 220R R2 = 10M R3 = 1M R4 = 10K R5 = 47K C1 = 100nF-63V C2 = 22µF-25V D1 = 1N4148 D2 = 3mm. Red LED Q1 = BC337 P1 = SPST Pushbutton (Start) P2 = SPST Pushbutton (Reset) PS = Piezo sounder (incorporating 3KHz oscillator) B1 = 3V Battery (2 AA 1.5V Cells in series) IC1 = CD4081 Quad 2 input AND Gate IC IC2 = CD4060 14 stage ripple counter and oscillator IC SW1 = 4 ways Switch (See notes) Circuit operation: Pushing on P1 resets IC2 that start oscillating at a frequency fixed by R3 & C...