R1_____________47K 1/4W Resistor R2_____________10M 1/4W Resistor R3______________1M 1/4W Resistor R4_____________12K 1/4W Resistor (see notes) C1,C3__________10µF 25V Electrolytic Capacitors C2____________100nF 63V Polyester Capacitor D1___________1N4148 75V 150mA Diode IC1____________4093 Quad 2 input Schmitt NAND Gate IC IC2____________4060 14 stage ripple counter and oscillator IC IC3____________4017 Decade counter with 10 decoded outputs IC Q1____________BC337 45V 800mA NPN Transistor SW1___________1 pole 9 ways Rotary Switch (see notes) SW2___________SPST Slider Switch BZ1___________Piezo sounder (incorporating 3KHz oscillator) B1____________3V Battery (two 1.5V AA or AAA cells in series etc.)
This circuit was developed since a number of visitors of this website requested a timer capable of emitting a beep after one, two, three minutes and so on, for jogging purposes.
As shown in the Circuit diagram, SW1 is a 1 pole 9 ways Rotary Switch. Setting the switch in position 1, the Piezo sounder emits three short beeps every minute. In position 2 the same thing happens after a 2 minutes delay, and so on, reaching a maximum interval of 9 minutes in position 9.
- Needing only one time set, rotary switch can be replaced by an hard-wired link.
- A DIP-Switch can be used in place of the rotary type. Please pay attention to use only one switch at a time, or the device could be damaged.
- Varying R4 from 10K to 15K you can obtain more or less than three short beeps after the preset time delay.
- To obtain a one-second beep only, after the preset time delay, disconnect pin 9 of IC1C from pin 9 of IC2 and connect it to pin 8 of IC1C.