3V Battery powered

Beeps after a fixed number of minutes

 

Parts:

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.)

Device purpose:

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 2 minutes, and so on, reaching a maximum interval of 9 minutes in position 9.

Notes:

• 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. Pay attention to use only a 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.