Wiring Schematic diagram

Packing a rucksack to go camping;  always poses problems. Either you stack everything exept the kitchen sink and stagger under the weight, or you keep the weight down but e t find yourself without something · essential.
An egg timer is not absolutely essential, of course, but it is often very handy. This circuit is aimed at people who want a small, battery-powered timer, which could also be used at home, if you dont have a mains socket free for an electronic egg timer. One half of the 556 timer is used to sound the buzzer. It is connected as an astable multivibrator and oscillates at about 2 kHz.

The actual   timing is controlled by Tj1g?‘other half of the timers. The sequence starts when,S3 connects th`e trigger input of the IC to ground. The length of the timing pulse is determined by the P1/R3/Copet work, For the prototype, ,C consisted of seven 47 pF/6 V capacitors in parallel. The total capacitance, about 300  gives a time of 6% minutes with P1 in mid-position. S1 is the power switch for the cir-  cult. Assuming this is ’on, pressing S2 resets the timer. Then the duration to be timed can be set with h P1 and started by pressing S3. ln case of a false start S2 will reset the circuit. Current consumption is about 23 mA. A scale can easily   be calibrated in minutes and . mounted behind the dial of P1, otherwise timing will still be a hit-or-miss affair! 

Please ignore the pen marks in the diagram.